Release 0.14.0

Version 0.14.0; the pending design-format changes are folded into format 25.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.config/nextest.toml

@@ -3,7 +3,8 @@
 
 [profile.ci]
 # Heavy tests (one to four minutes each on a CI runner) that pull requests skip. They run on
-# every push to main and nightly (`--ignore-default-filter`), and in `cargo xtask test`.
+# every push to main and nightly (`--ignore-default-filter`), and in `cargo xtask test`. The
+# boolean_props property tests run only nightly (ci.yml excludes them from pushes to main).
 # Keep this list in sync with docs/book/src/dev/testing.md and CONTRIBUTING.md.
 default-filter = """
 not (
@@ -16,6 +17,8 @@ not (
         | test(=cmd::plastic::tests::enclosure_snap_fit_follows_resized_front_wall)
     ))
     | (package(solidcraft-kernel) & test(=tests::boolean_identity_on_tangent_primitives))
+    | (package(solidcraft-kernel) & binary(boolean_props))
+    | (package(solidcraft-engine) & binary(atomic_commands))
     | (package(solidcraft-ui-egui) & binary(scenarios) & test(=acceptance_sensor_enclosure))
 )
 """

.github/workflows/ci.yml

@@ -1,4 +1,10 @@
 # Fast checks always run; native builds run for code/CI changes.
+# PRs test what they touch; main and nightly test everything. On a pull request the "Select
+# checks" job maps the changed files to workspace packages (scripts/ci/affected.py), adds the
+# packages that depend on them, and Clippy, the test archive and the test shards cover only
+# those. Changes to the lockfile, root manifest, toolchain/cargo/nextest config, .github/,
+# vendor/, tests/, scripts/ or any file no package owns select the whole workspace, as do
+# pushes to main, the nightly run and Run workflow.
 # Tests are built once and run in 4 shards. A few heavy tests (see .config/nextest.toml) are
 # skipped on pull requests and run on pushes to main and nightly.
 # Cross-compilation is opt-in through Run workflow; release builds remain in release.yml.
@@ -49,6 +55,8 @@ jobs:
     outputs:
       native: ${{ steps.paths.outputs.native }}
       kernel: ${{ steps.paths.outputs.kernel }}
+      full: ${{ steps.paths.outputs.full }}
+      packages: ${{ steps.paths.outputs.packages }}
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
@@ -62,6 +70,8 @@ jobs:
         run: |
           native=false
           kernel=false
+          full=true
+          packages=
           if [ "$EVENT_NAME" != pull_request ]; then
             native=true
           else
@@ -76,9 +86,20 @@ jobs:
                 *) native=true ;;
               esac
             done < "$RUNNER_TEMP/ci-paths"
+            # Pull requests build and test the touched packages and their dependents.
+            python3 -I scripts/ci/affected.py --paths "$RUNNER_TEMP/ci-paths" > "$RUNNER_TEMP/ci-affected"
+            cat "$RUNNER_TEMP/ci-affected"
+            full=$(sed -n 's/^full=//p' "$RUNNER_TEMP/ci-affected")
+            packages=$(sed -n 's/^packages=//p' "$RUNNER_TEMP/ci-affected")
+            # Code changed but nothing was selected: be safe and test everything.
+            if [ "$native" = true ] && [ "$full" != true ] && [ -z "$packages" ]; then full=true; fi
           fi
-          echo "native=$native" >> "$GITHUB_OUTPUT"
-          echo "kernel=$kernel" >> "$GITHUB_OUTPUT"
+          {
+            echo "native=$native"
+            echo "kernel=$kernel"
+            echo "full=$full"
+            echo "packages=$packages"
+          } >> "$GITHUB_OUTPUT"
 
   checks:
     name: Format and repository checks
@@ -102,6 +123,10 @@ jobs:
         run: cargo xtask layers
       - name: Web app offline use and updates (headless Chrome)
         run: cargo xtask web-offline-test
+      - name: Affected-package selection self-test
+        run: python3 -I scripts/ci/test_affected.py
+      - name: Claim bot tests
+        run: node --test scripts/claim/*.test.js
 
   clippy:
     name: Native Linux Clippy
@@ -117,7 +142,15 @@ jobs:
       - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
         with:
           key: native-clippy
-      - run: cargo clippy --workspace --all-targets --profile ci --locked -- -D warnings
+      - name: Clippy
+        env:
+          FULL: ${{ needs.changes.outputs.full }}
+          PACKAGES: ${{ needs.changes.outputs.packages }}
+        run: |
+          # Pull requests lint the affected packages (scripts/ci/affected.py); everything else, all.
+          scope=(--workspace)
+          if [ "$FULL" != true ]; then scope=(); for p in $PACKAGES; do scope+=(-p "$p"); done; fi
+          cargo clippy "${scope[@]}" --all-targets --profile ci --locked -- -D warnings
 
   build-tests:
     name: Build tests
@@ -144,7 +177,14 @@ jobs:
         with:
           tool: cargo-nextest
       - name: Compile tests into a nextest archive
-        run: cargo nextest archive --workspace --cargo-profile ci --locked --archive-file tests.tar.zst
+        env:
+          FULL: ${{ needs.changes.outputs.full }}
+          PACKAGES: ${{ needs.changes.outputs.packages }}
+        run: |
+          # Pull requests archive only the affected packages (scripts/ci/affected.py).
+          scope=(--workspace)
+          if [ "$FULL" != true ]; then scope=(); for p in $PACKAGES; do scope+=(-p "$p"); done; fi
+          cargo nextest archive "${scope[@]}" --cargo-profile ci --locked --archive-file tests.tar.zst
       - uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
         with:
           name: nextest-archive
@@ -164,8 +204,18 @@ jobs:
       fail-fast: false
       matrix:
         shard: [1, 2, 3, 4]
+    env:
+      # Pictures (snapshots, screenshots, ui.render, the viewport's offscreen tests) are drawn on
+      # the GPU. The runner has none: Mesa's lavapipe (software Vulkan) draws them, and a test that
+      # would skip for want of an adapter fails instead.
+      SOLIDCRAFT_GPU: software
+      SOLIDCRAFT_REQUIRE_GPU: "1"
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Install a software Vulkan driver (lavapipe)
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends mesa-vulkan-drivers libvulkan1
       - uses: taiki-e/install-action@1168f6810a3cb30a3514bf5756a3b7f0422c6df8 # v2.87.28
         with:
           tool: cargo-nextest
@@ -179,11 +229,15 @@ jobs:
         run: |
           # Pull requests skip the heavy tests (default-filter in .config/nextest.toml).
           all=()
-          if [ "$EVENT_NAME" != pull_request ]; then all=(--ignore-default-filter); fi
+          # The boolean property tests draw new random inputs every run; they run only in the
+          # nightly property-tests job, so a known kernel bug cannot turn main red at random.
+          if [ "$EVENT_NAME" != pull_request ]; then
+            all=(--ignore-default-filter -E 'not (package(solidcraft-kernel) & binary(boolean_props))')
+          fi
           # Extract into ./target: tests that run a built binary (env!("CARGO_BIN_EXE_*")) have
           # the build job's path, which is the same checkout path here.
           cargo nextest run --archive-file tests.tar.zst --workspace-remap . --extract-to . --extract-overwrite \
-            --profile ci --partition "slice:$SHARD/4" "${all[@]}"
+            --profile ci --partition "slice:$SHARD/4" --no-tests=pass "${all[@]}"
       - name: Robustness goldens sample (pull requests that touch the kernel)
         # Every 8th seed of tests/robustness/goldens.json, a quarter per shard; pushes to main and
         # the nightly run every seed in the step above.
@@ -267,6 +321,33 @@ jobs:
           cargo nextest run --archive-file tests.tar.zst --workspace-remap . --extract-to . --extract-overwrite \
             --profile ci --success-output final --run-ignored only -E "binary(action_matrix) & test(=action_matrix_determinism)"
 
+  property-tests:
+    # The boolean property tests and the atomic command tests with many cases. Pull requests skip
+    # them (.config/nextest.toml); pushes to main run atomic_commands with small defaults (seeds
+    # 0..4) and skip boolean_props, whose random inputs would fail main at random.
+    name: Property tests (many cases)
+    needs: build-tests
+    if: github.event_name == 'schedule' || github.event_name == 'workflow_dispatch'
+    runs-on: ubuntu-24.04
+    timeout-minutes: 60
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: taiki-e/install-action@1168f6810a3cb30a3514bf5756a3b7f0422c6df8 # v2.87.28
+        with:
+          tool: cargo-nextest
+      - uses: actions/download-artifact@9000827ccba6bdab643e8b6fd33ac0654aef8333 # v8.0.2
+        with:
+          name: nextest-archive
+      - name: Boolean properties and atomic commands
+        # The defaults (8 cases, seeds 0..4) take 159 s and 802 s on a 2-core VM; four times the
+        # cases and twice the seeds are estimated at about 40 minutes there (not yet timed on CI).
+        env:
+          PROPTEST_CASES: "32"
+          ATOMIC_SEEDS: "0..8"
+        run: |
+          cargo nextest run --archive-file tests.tar.zst --workspace-remap . --extract-to . --extract-overwrite \
+            --profile ci --ignore-default-filter --success-output final -E "binary(boolean_props) | binary(atomic_commands)"
+
   doc-tests:
     name: Doc tests
     needs: changes
@@ -326,7 +407,8 @@ jobs:
   # D3D12's older shader compiler (FXC, used where dxcompiler.dll is absent) is stricter than
   # DXC, Vulkan and Metal: a shader it cannot compile once crashed the app at startup. Build the
   # GPU tessellation pipeline with FXC on the runner's WARP software adapter and compare its
-  # results with the CPU.
+  # results with the CPU, and draw headless pictures with the viewport's pipelines there
+  # (crates/gpu/tests/capture.rs).
   windows-fxc:
     name: Windows D3D12 FXC shaders
     needs: changes
@@ -336,6 +418,8 @@ jobs:
     env:
       WGPU_BACKEND: dx12
       WGPU_DX12_COMPILER: fxc
+      # WARP is a software (Cpu) adapter.
+      SOLIDCRAFT_GPU: software
       SOLIDCRAFT_REQUIRE_GPU: "1"
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -365,12 +449,15 @@ jobs:
         with:
           key: windows-startup
       - name: Backend order and probing on Windows
-        run: cargo test -p solidcraft --profile ci --locked -- startup::tests native_crash::tests
+        run: cargo test -p solidcraft --profile ci --locked -- startup::tests native_crash::tests native_frame::tests
       - name: Build the app
         run: cargo build -p solidcraft --profile ci --locked
       - name: Start the app under different settings
         shell: pwsh
         run: tools/windows-startup-smoke.ps1 -Exe target/ci/solidcraft.exe
+      - name: Resize border from the first frame
+        shell: pwsh
+        run: tools/windows-resize-smoke.ps1 -Exe target/ci/solidcraft.exe
 
   # Preserve the existing check name for branch protection, including docs-only PRs.
   ci:

.github/workflows/claim.yml

@@ -0,0 +1,44 @@
+# `/claim` and `/unclaim` on issues (CONTRIBUTING.md, "Sending a change"), and a daily sweep that
+# frees claims nobody is working on. The logic is in scripts/claim/claim.js (tested in ci.yml).
+name: Claim
+
+on:
+  issue_comment:
+    types: [created]
+  schedule:
+    - cron: '17 5 * * *'
+  workflow_dispatch:
+
+permissions:
+  contents: read # to check out scripts/claim
+  issues: write
+  pull-requests: read
+
+# One run at a time per issue, so two simultaneous /claim comments can't both win.
+concurrency:
+  group: claim-${{ github.event.issue.number || 'sweep' }}
+  cancel-in-progress: false
+
+jobs:
+  claim:
+    name: Claim bot
+    runs-on: ubuntu-24.04
+    timeout-minutes: 10
+    if: >-
+      github.event_name != 'issue_comment' ||
+      (!github.event.issue.pull_request && github.event.comment.user.type != 'Bot' &&
+      (startsWith(github.event.comment.body, '/claim') || startsWith(github.event.comment.body, '/unclaim')))
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          sparse-checkout: scripts/claim
+      - uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
+        with:
+          script: |
+            const claim = require('./scripts/claim/claim.js');
+            if (context.eventName === 'issue_comment') {
+              await claim.handleComment({ github, context });
+            } else {
+              const released = await claim.sweep({ github, context });
+              core.info(`Released: ${released.join(', ') || 'none'}`);
+            }

.github/workflows/generated.yml

@@ -0,0 +1,48 @@
+# Files generated from the code are rewritten here, on main, after each merge, so pull requests
+# never edit them (two pull requests that each regenerated one would always conflict):
+# THIRD-PARTY-LICENSES.txt (`cargo xtask licences`) and docs/features.md (`cargo xtask features`).
+name: Generated files
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: write
+
+# One run at a time; a burst of merges leaves one run waiting, which sees all of them.
+concurrency:
+  group: generated-files
+  cancel-in-progress: false
+
+jobs:
+  regenerate:
+    name: Regenerate and commit
+    runs-on: ubuntu-24.04
+    timeout-minutes: 60
+    steps:
+      # Always main itself, never pull request code, since this job can push.
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          ref: main
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
+        with:
+          key: generated-files
+      - name: THIRD-PARTY-LICENSES.txt
+        run: cargo xtask licences
+      - name: docs/features.md
+        run: cargo xtask features
+      - name: Commit if changed
+        run: |
+          if git diff --quiet -- THIRD-PARTY-LICENSES.txt docs/features.md; then echo "unchanged"; exit 0; fi
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git add THIRD-PARTY-LICENSES.txt docs/features.md
+          git commit -m "Regenerate THIRD-PARTY-LICENSES.txt and docs/features.md [skip ci]"
+          for _ in 1 2 3; do
+            git pull --rebase origin main && git push origin HEAD:main && exit 0
+            sleep 10
+          done
+          exit 1

.github/workflows/lists.yml

@@ -0,0 +1,32 @@
+# Files many pull requests add to are kept so that additions don't conflict: one file per change
+# or one sorted line per item (CONTRIBUTING.md, "Lists many changes add to"). Fast, no build.
+name: Lists
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  format-changes:
+    name: Design format changes merge cleanly
+    runs-on: ubuntu-24.04
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - run: bash scripts/test-format-pending.sh
+
+  sorted:
+    name: Lists are sorted one item per line
+    runs-on: ubuntu-24.04
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
+        with:
+          key: lists
+      - run: cargo xtask lists

.github/workflows/pages.yml

@@ -45,7 +45,14 @@ jobs:
           curl -sSL "https://github.com/rust-lang/mdBook/releases/download/${MDBOOK_VERSION}/mdbook-${MDBOOK_VERSION}-x86_64-unknown-linux-gnu.tar.gz" | tar -xz -C "$HOME/.local/bin"
           curl -sSL "https://github.com/trunk-rs/trunk/releases/download/${TRUNK_VERSION}/trunk-x86_64-unknown-linux-gnu.tar.gz" | tar -xz -C "$HOME/.local/bin"
           echo "$HOME/.local/bin" >> "$GITHUB_PATH"
+      - name: Install a software Vulkan driver (lavapipe)
+        # The book's pictures are `solidcraft-cli snapshot`s, drawn on the GPU; the runner has none.
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends mesa-vulkan-drivers libvulkan1
       - name: Build the book
+        env:
+          SOLIDCRAFT_GPU: software
         run: cargo xtask book
       - name: Build the web app
         working-directory: apps/solidcraft-web

AGENTS.md

@@ -27,11 +27,13 @@ new uses of it anywhere else. Public docs/web/Flatpak deployments use project Pa
 ## Never crash
 People trust SolidCraft with their designs; a crash loses their work. **This outranks feature work.**
 - **No panics in non-test code:** no `unwrap()`, `expect()`, `panic!`, `unreachable!`, `todo!`,
-  `unimplemented!`; no `unsafe` (`unsafe_code = "forbid"`). The two exceptions, in the app crate
+  `unimplemented!`; no `unsafe` (`unsafe_code = "forbid"`). The three exceptions, in the app crate
   (which denies it instead), have no safe API: two functions in
   `apps/solidcraft/src/open_documents.rs` (macOS hands Finder files only to an Objective-C
-  method) and the Windows-only `apps/solidcraft/src/native_crash.rs` (the exception filter that
-  records crashes inside native code such as graphics drivers).
+  method), the Windows-only `apps/solidcraft/src/native_crash.rs` (the exception filter that
+  records crashes inside native code such as graphics drivers) and the Windows-only
+  `apps/solidcraft/src/native_frame.rs` (the window procedure that answers the resize-border hit
+  test of the window without OS decorations).
 - **Errors are `Result<T, E>`** through the crate's error type and `?`. An unfinished feature
   returns an error ("not supported yet: …"); it never panics.
 - **Input-derived numbers are hostile** (command parameters, design files, control-channel
@@ -79,6 +81,10 @@ People trust SolidCraft with their designs; a crash loses their work. **This out
   egui/eframe/winit/wgpu/rfd. **The UI crate is swappable.** Only `crates/kernel` may use `truck`.
 - **The UI is thin**: panels read engine state and act through `app.run(id, params)` /
   `app.start(id)`. Colours come from `theme::Tokens`.
+- **One set of camera controls**: every page or canvas with a camera (viewport, Render
+  preview, future flat pattern or drawing pages) calls `navigation::handle` with its `NavCaps`
+  (orbit off for flat 2D pages). New canvases must use `navigation::handle`; never hand-roll
+  camera input (a test rejects it).
 - **Rust only.** Units are millimetres and radians internally; Z is up. The one exception is
   JavaScript the browser requires: the service worker `apps/solidcraft-web/sw.js` (browsers only
   run service workers as JavaScript) and the small inline scripts in `apps/solidcraft-web/index.html`.
@@ -117,6 +123,23 @@ People trust SolidCraft with their designs; a crash loses their work. **This out
   keep monitoring it while the task is active and make its pending status clear at handoff;
   do not claim it merged without checking.
 
+## Claim = a draft PR
+- Before working on issue #N, check nobody has it: `gh pr list -R bherbruck/solidcraft --state open --search "#N"`.
+- If none, branch from the latest `origin/main`, `git commit --allow-empty -m "claim: #N"`, push,
+  and open a **draft** PR titled `<summary> (#N)` right away. **The lowest-numbered open PR for an
+  issue wins**; if yours lost, close it. Don't claim by commenting or by editing files.
+- Push work in progress at least daily. A draft with no pushes for 72 hours may be taken over:
+  comment on it first, then open your own claim (you may start from its branch).
+- On a shared build machine, check the load before a big build (`cut -d' ' -f1 /proc/loadavg`)
+  and wait while it is over 24; build with `nice`.
+
+## Design file format
+A change that saves something new in a design adds ONE file, `crates/doc/src/format/pending/<name>.rs`
+(a `//!` note, and `pub fn step` if older designs must be rewritten). Never edit `FORMAT`,
+`JSON_STEPS`, the history in `format.rs`, another change's file or a `v<N>/` folder: the build
+works out the number (the next one while anything is pending), and the release folds pending
+changes into `v<N>/` with `scripts/fold-format-pending.sh`. See CONTRIBUTING.md.
+
 ## Application releases
 Development pushes are not application releases. Follow `docs/releasing.md` when asked to
 prepare or ship a release: choose the version from the actual changes, update Cargo.toml and
@@ -147,5 +170,11 @@ before the draft is verified.
 
 ## Roadmap
 `ROADMAP.md` (committed) tracks status, milestones and estimates. Update it whenever a
-milestone task lands. `cargo xtask features` regenerates `docs/features.md` (SolidCraft's
-commands by area, from the registry) when commands are added or renamed.
+milestone task lands. `docs/features.md` (SolidCraft's commands by area, from the registry) and
+`THIRD-PARTY-LICENSES.txt` are regenerated on `main` after each merge by the Generated files
+workflow; never regenerate them in a PR.
+
+## Lists many PRs add to
+Keep them conflict-free (CONTRIBUTING.md, "Lists many changes add to"): message catalogs sorted
+(`cargo xtask lists --fix`), `mod` lines in their sorted group, the language list English first
+then by id, generated files left to `main`, and a design-format change as one new file.

ATTRIBUTION.md

@@ -16,7 +16,7 @@ Editable drawing code, native projects and shipped exports are collected under `
 |---|---|---|---|
 | examples/render-studio.json | SolidCraft contributors | original procedural box/cylinder enclosure script for the integrated Render workspace | MIT OR Apache-2.0 |
 | examples/render-opaque-studio.json | SolidCraft contributors | original procedural sphere study varying opaque metal fraction and roughness independently; no external assets or engineering data | MIT OR Apache-2.0 |
-| crates/ui-egui/src/pbr_gpu.rs | SolidCraft contributors | original WGSL translation of SolidCraft's opaque surface and fixed studio reference, embedded as Rust source; no external shader code | MIT OR Apache-2.0 |
+| crates/gpu/src/pbr.rs | SolidCraft contributors | original WGSL translation of SolidCraft's opaque surface and fixed studio reference, embedded as Rust source; no external shader code | MIT OR Apache-2.0 |
 | assets/archive/icons/macos-v1/exports/icon.svg | SolidCraft contributors | original macOS adaptation of the code-drawn SolidCraft mark, edited and exported with VectorCraft; Apple HIG and production templates consulted as layout references only | MIT OR Apache-2.0 |
 | assets/icons/app/macos/source/SolidCraft.icon/icon.json | SolidCraft contributors | approved Icon Composer composition and appearance settings for the original SolidCraft artwork | MIT OR Apache-2.0 |
 | assets/icons/app/macos/source/SolidCraft.icon/Assets/02-grid.svg | SolidCraft contributors | original perspective grid with elliptical radial alpha, exported from VectorCraft | MIT OR Apache-2.0 |
@@ -36,6 +36,7 @@ Editable drawing code, native projects and shipped exports are collected under `
 | assets/archive/icons/macos-v1/exports/icon.iconset/icon_256x256@2x.png | SolidCraft contributors | native sips export from assets/archive/icons/macos-v1/exports/icon.png | MIT OR Apache-2.0 |
 | assets/archive/icons/macos-v1/exports/icon.iconset/icon_512x512.png | SolidCraft contributors | native sips export from assets/archive/icons/macos-v1/exports/icon.png | MIT OR Apache-2.0 |
 | assets/archive/icons/macos-v1/exports/icon.iconset/icon_512x512@2x.png | SolidCraft contributors | native sips export from assets/archive/icons/macos-v1/exports/icon.png | MIT OR Apache-2.0 |
+| docs/screenshots/class-a-boundary.png | SolidCraft contributors | screenshot of SolidCraft itself: a patch through two sketch lines built by `surface.boundary` with `crown: 0.4` (`solidcraft-cli snapshot`) | MIT OR Apache-2.0 |
 | docs/screenshots/sample-plate.png | SolidCraft contributors | screenshot of SolidCraft itself (`solidcraft --sample`) | MIT OR Apache-2.0 |
 | docs/screenshots/demo-0.8.gif | SolidCraft contributors | original screen recording of the actual SolidCraft 0.8 English desktop UI modelling an original Raspberry Pi 4 case (no logos or branding; the engraved text is set in the system's DejaVu Sans Bold), generated with examples/demo/record_ui.sh and its original animated pointer overlay (9× playback) | MIT OR Apache-2.0 |
 | docs/screenshots/demo-0.8.mp4 | SolidCraft contributors | original screen recording of the actual SolidCraft 0.8 English desktop UI modelling an original Raspberry Pi 4 case (no logos or branding; the engraved text is set in the system's DejaVu Sans Bold), generated with examples/demo/record_ui.sh and its original animated pointer overlay (9× playback) | MIT OR Apache-2.0 |
@@ -96,6 +97,7 @@ Editable drawing code, native projects and shipped exports are collected under `
 | assets/locales/ja.json | SolidCraft contributors | Original SolidCraft resource data or drawing code, collected without redesign | MIT OR Apache-2.0 |
 | assets/locales/ko.json | SolidCraft contributors | Original SolidCraft resource data or drawing code, collected without redesign | MIT OR Apache-2.0 |
 | assets/locales/ru.json | Alex Pro (del000) | Russian translation of the English catalog, contributed upstream | MIT OR Apache-2.0 |
+| assets/locales/tr.json | macrulz54 | Turkish translation of the English catalog, contributed upstream | MIT OR Apache-2.0 |
 | assets/locales/uk.json | Igor Bronovskyi (BrunIF) | Ukrainian translation of the English catalog, contributed upstream | MIT OR Apache-2.0 |
 | assets/locales/zh.json | SolidCraft contributors | Original SolidCraft resource data or drawing code, collected without redesign | MIT OR Apache-2.0 |
 | assets/materials/library.rs | SolidCraft contributors | Original SolidCraft resource data or drawing code, collected without redesign | MIT OR Apache-2.0 |
@@ -109,6 +111,8 @@ Editable drawing code, native projects and shipped exports are collected under `
 | assets/shaders/viewport.wgsl | SolidCraft contributors | Original SolidCraft resource data or drawing code, collected without redesign | MIT OR Apache-2.0 |
 | assets/styles/ui/palettes.rs | SolidCraft contributors | Original SolidCraft resource data or drawing code, collected without redesign | MIT OR Apache-2.0 |
 | assets/styles/web/loading.css | SolidCraft contributors | Original SolidCraft resource data or drawing code, collected without redesign | MIT OR Apache-2.0 |
+| crates/io/src/native_cad/fixtures/block.FCStd | SolidCraft contributors | original 10 × 20 × 30 mm test box saved by FreeCAD 1.1.4 run as an external program (`make_block_fcstd.py` beside it); no third-party geometry | MIT OR Apache-2.0 |
+| crates/io/src/native_cad/fixtures/block.3dm | SolidCraft contributors | original 10 × 20 × 30 mm test box written with McNeel's MIT-licensed rhino3dm Python package (`make_block_3dm.py` beside it); no third-party geometry | MIT OR Apache-2.0 |
 
 | docs/book/src/og.png | SolidCraft contributors | copy of assets/branding/web/source/og.png staged by cargo xtask book (gitignored) | MIT OR Apache-2.0 |
 
@@ -139,6 +143,27 @@ work cooperative and adds checked run lengths, zero-run rejection, width validat
 header/input/radiance bounds and cancellation. Original licence texts are retained
 in THIRD-PARTY-LICENSES.txt; no images or artwork from that project are copied.
 
+## File-format crates
+
+| Crate | Used for | Licence |
+|---|---|---|
+| gltf 1.4.1, gltf-json 1.4.1, gltf-derive 1.4.1 (https://github.com/gltf-rs/gltf) | glTF 2.0 import (crates/io/src/gltf_in.rs): the JSON document model and its reference checks; the GLB container, buffers and accessors are read by SolidCraft's own code | MIT OR Apache-2.0 |
+| inflections 1.1.1 (build-time, through gltf-derive) | case conversion in gltf's derive macros | MIT |
+| lazy_static 1.5.1 (through gltf-json) | | MIT OR Apache-2.0 |
+
+The glTF test files are built by the tests themselves (crates/io/src/gltf_in_tests.rs,
+crates/engine/src/tests/gltf_import.rs); no third-party models are committed.
+
+## FreeCAD and Rhino import library
+
+FreeCAD `.FCStd` and Rhino `.3dm` files are read with [cadmpeg](https://github.com/cadmpeg/cadmpeg)
+0.6.1 (Apache-2.0), linked as the crates `cadmpeg-core`, `cadmpeg-ir`, `cadmpeg-registry`,
+`cadmpeg-container`, `cadmpeg-codec-freecad`, `cadmpeg-codec-rhino` and `cadmpeg-codec-step`
+in native builds (`crates/io/src/native_cad.rs`). Only those open-format codecs are built: no
+default features, so cadmpeg's codecs for commercial CAD formats and its ShapeManager/ACIS
+codec are not compiled in. Its licence text is in THIRD-PARTY-LICENSES.txt; no code from it is
+copied into SolidCraft.
+
 ## Recovered contributions
 
 | SolidCraft file | Original contribution | Licence |
@@ -152,6 +177,7 @@ in THIRD-PARTY-LICENSES.txt; no images or artwork from that project are copied.
 | vendor/truck-meshalgo | truck-meshalgo 0.4.0, https://github.com/ricosjp/truck (RICOS Co. Ltd.) | Apache-2.0 | meshing: bounded parameter searches, collapsed-boundary projection, subdivision and provisional fixed-grid previews (vendor/README.md) |
 | vendor/truck-stepio | truck-stepio 0.3.0, https://github.com/ricosjp/truck (RICOS Co. Ltd.) | Apache-2.0 | STEP writer: intersection-curve surfaces written at unique ids (vendor/README.md) |
 | vendor/truck-shapeops | truck-shapeops 0.4.0, https://github.com/ricosjp/truck (RICOS Co. Ltd.) | Apache-2.0 | robust meshing and nearest-parameter fallback in booleans; degenerate intersection-curve rejection; face and edge history of booleans; trace macro; corner choice at vertices several intersection curves end on (vendor/README.md) |
+| vendor/truck-geometry | truck-geometry 0.5.0, https://github.com/ricosjp/truck (RICOS Co. Ltd.) | Apache-2.0 | intersection curves divided from their neighbours' surface parameters (vendor/README.md) |
 | vendor/matext4cgmath | matext4cgmath 0.1.0, https://github.com/ricosjp/matext4cgmath (RICOS Co. Ltd.) | Apache-2.0 | root refinement stops after 100 Newton steps (vendor/README.md) |
 
 ## Vendored renderer compatibility fix
@@ -162,3 +188,5 @@ its original `egui.wgsl` shader are retained; no images or other artwork are cop
 SolidCraft's narrow patch selects a safe 1x MSAA path on the chosen OpenGL adapter
 and shares that effective count with the surface attachments and CAD callbacks.
 Vulkan, DirectX 12, Metal and WebGPU retain their requested multisampling.
+A frame whose meshes the GPU refuses to stage (device lost or out of memory) is
+skipped with a warning instead of panicking (#1469).

CLAUDE.md

@@ -27,11 +27,13 @@ new uses of it anywhere else. Public docs/web/Flatpak deployments use project Pa
 ## Never crash
 People trust SolidCraft with their designs; a crash loses their work. **This outranks feature work.**
 - **No panics in non-test code:** no `unwrap()`, `expect()`, `panic!`, `unreachable!`, `todo!`,
-  `unimplemented!`; no `unsafe` (`unsafe_code = "forbid"`). The two exceptions, in the app crate
+  `unimplemented!`; no `unsafe` (`unsafe_code = "forbid"`). The three exceptions, in the app crate
   (which denies it instead), have no safe API: two functions in
   `apps/solidcraft/src/open_documents.rs` (macOS hands Finder files only to an Objective-C
-  method) and the Windows-only `apps/solidcraft/src/native_crash.rs` (the exception filter that
-  records crashes inside native code such as graphics drivers).
+  method), the Windows-only `apps/solidcraft/src/native_crash.rs` (the exception filter that
+  records crashes inside native code such as graphics drivers) and the Windows-only
+  `apps/solidcraft/src/native_frame.rs` (the window procedure that answers the resize-border hit
+  test of the window without OS decorations).
 - **Errors are `Result<T, E>`** through the crate's error type and `?`. An unfinished feature
   returns an error ("not supported yet: …"); it never panics.
 - **Input-derived numbers are hostile** (command parameters, design files, control-channel
@@ -94,6 +96,23 @@ People trust SolidCraft with their designs; a crash loses their work. **This out
 - **Never break wasm**: everything below the apps must build for `wasm32-unknown-unknown`
   (`cargo xtask wasm`, part of `cargo xtask ci`).
 
+## Claim = a draft PR
+- Before working on issue #N, check nobody has it: `gh pr list -R bherbruck/solidcraft --state open --search "#N"`.
+- If none, branch from the latest `origin/main`, `git commit --allow-empty -m "claim: #N"`, push,
+  and open a **draft** PR titled `<summary> (#N)` right away. **The lowest-numbered open PR for an
+  issue wins**; if yours lost, close it. Don't claim by commenting or by editing files.
+- Push work in progress at least daily. A draft with no pushes for 72 hours may be taken over:
+  comment on it first, then open your own claim (you may start from its branch).
+- On a shared build machine, check the load before a big build (`cut -d' ' -f1 /proc/loadavg`)
+  and wait while it is over 24; build with `nice`.
+
+## Design file format
+A change that saves something new in a design adds ONE file, `crates/doc/src/format/pending/<name>.rs`
+(a `//!` note, and `pub fn step` if older designs must be rewritten). Never edit `FORMAT`,
+`JSON_STEPS`, the history in `format.rs`, another change's file or a `v<N>/` folder: the build
+works out the number (the next one while anything is pending), and the release folds pending
+changes into `v<N>/` with `scripts/fold-format-pending.sh`. See CONTRIBUTING.md.
+
 ## Application releases
 Development pushes are not application releases. Follow `docs/releasing.md` when asked to
 prepare or ship a release: choose the version from the actual changes, update Cargo.toml and
@@ -124,5 +143,11 @@ before the draft is verified.
 
 ## Roadmap
 `ROADMAP.md` (committed) tracks status, milestones and estimates. Update it whenever a
-milestone task lands. `cargo xtask features` regenerates `docs/features.md` (SolidCraft's
-commands by area, from the registry) when commands are added or renamed.
+milestone task lands. `docs/features.md` (SolidCraft's commands by area, from the registry) and
+`THIRD-PARTY-LICENSES.txt` are regenerated on `main` after each merge by the Generated files
+workflow; never regenerate them in a PR.
+
+## Lists many PRs add to
+Keep them conflict-free (CONTRIBUTING.md, "Lists many changes add to"): message catalogs sorted
+(`cargo xtask lists --fix`), `mod` lines in their sorted group, the language list English first
+then by id, generated files left to `main`, and a design-format change as one new file.

CONTRIBUTING.md

@@ -98,8 +98,8 @@ The [README](README.md#architecture) has the layer table. The short version:
    MIT OR Apache-2.0, and its solver and blends are written from the maths. (Running an
    open-source application to get reference values for a test is fine; reading its source is
    not.) Permissive
-   dependencies are fine. Note which one you're adding and why in the PR, and run
-   `cargo xtask licences` so THIRD-PARTY-LICENSES.txt lists it (CI checks that it is current).
+   dependencies are fine. Note which one you're adding and why in the PR. THIRD-PARTY-LICENSES.txt
+   lists it once the change lands: the Generated files workflow rewrites it on `main`.
    Nightly/manual CI also scans advisories, bans and sources with cargo-deny; see
    [the local command and coverage limits](docs/book/src/dev/testing.md#dependency-advisories).
 3. **Every asset is original or openly licensed and has a row in
@@ -116,6 +116,12 @@ The [README](README.md#architecture) has the layer table. The short version:
 5. **Everything is a command, with a test.** A new feature means a `CommandSpec` in
    `crates/engine/src/cmd/`, engine tests that measure the result (volume, area,
    face/edge/vertex counts against a value you can derive), and for UI work a scenario (below).
+6. **One set of camera controls.** Every page or canvas that shows a view (the modelling
+   viewport, the Render preview, and any new page such as a flat pattern or drawing) calls
+   `navigation::handle` (`crates/ui-egui/src/navigation.rs`) for its camera input, with
+   `NavCaps` saying whether it can orbit (off for flat 2D pages) and pick. New canvases must use
+   `navigation::handle`; never read drags, the wheel or pinch to move the camera yourself. The
+   `hand_rolled_camera_input_is_rejected` test fails if a page does.
 
 [AGENTS.md](AGENTS.md) has the long form of these rules. It's written for AI agents, but it's
 the most complete description of the house style.
@@ -157,6 +163,13 @@ in the PR. `cargo xtask test` builds the tests with it and then runs every test
 `cargo xtask test -- shell`. Tests run beside each other on a busy machine, so a test must not
 depend on wall-clock timing.
 
+**PRs test what they touch; main and nightly test everything.** On a pull request, CI maps the
+changed files to workspace packages and runs Clippy, the test build and the tests for those and
+the packages that depend on them (`scripts/ci/affected.py`, self-tested in the `checks` job). A
+change to `Cargo.lock`, the root `Cargo.toml`, `.cargo/`, `.config/`, `.github/`, `vendor/`,
+`tests/`, `scripts/` or any file outside a package runs the whole workspace, as does every push
+to `main`, the nightly run and Run workflow.
+
 **CI shards the tests.** One job builds them into a cargo-nextest archive and four jobs run a
 quarter each, so every test runs in its own process: don't rely on state left by another test.
 Pull requests skip a few heavy tests (one to four minutes each), which run on every push to
@@ -167,8 +180,9 @@ Pull requests skip a few heavy tests (one to four minutes each), which run on ev
   `tests::robustness_goldens` (pull requests that touch `crates/kernel` run its `sample_*` part),
   `pattern_suppress_tests::enclosure_arc_extinction_keeps_a_real_sharp_inner_lip_after_resize_and_reopen`,
   `pattern_suppress_tests::enclosure_datums_follow_wall_height_and_board_depth_with_material_proofs`,
-  `cmd::plastic::tests::enclosure_snap_fit_follows_resized_front_wall`
-- `solidcraft-kernel`: `tests::boolean_identity_on_tangent_primitives`
+  `cmd::plastic::tests::enclosure_snap_fit_follows_resized_front_wall`, the `atomic_commands` contract tests
+- `solidcraft-kernel`: `tests::boolean_identity_on_tangent_primitives`, and the `boolean_props` property tests
+  (these run only in the nightly "Property tests" job: their inputs are random, so main skips them too)
 - `solidcraft-ui-egui` scenarios: `acceptance_sensor_enclosure`
 
 **The action matrix** tries every ordinary action on every face, edge, vertex and body of a
@@ -186,18 +200,75 @@ the current results, and CI runs `cargo xtask oracle` on every pull request. A c
 because of a known bug names its issue in `expected.json` (`"known_failure": "#123"`); never
 change an expected value to match SolidCraft's output.
 
+## Changing the design file format
+
+A design file says which format it is in (`"format": "solidcraft/N"`). If your change saves
+something new in a design (a field, a feature type, a new kind of name), or makes older designs
+mean something else, it needs a format change. **Add one file, and edit nothing shared:**
+
+1. Create `crates/doc/src/format/pending/<what-it-is>.rs` (lowercase, dashes). Start it with a
+   `//!` note: what is saved, what older designs get without it, and that the last release asks
+   for an update instead of meeting it.
+2. If older designs must be rewritten as they open, put `pub fn step(v: &mut Value) ->
+   crate::Result<()>` in the same file. Pending steps run in file-name order, after the older
+   formats' steps.
+3. Don't touch `FORMAT`, `JSON_STEPS`, the history in `crates/doc/src/format.rs`, another
+   change's file, or any `v<N>/` folder: those are fixed once released.
+
+That's all. The build counts the files: while any are pending it writes the next format number,
+which no release reads, so a release refuses a design that has your change instead of losing it.
+A file also lists the pending changes it has (`format_pending`), so a later development build
+runs only the steps that file is missing. Two pull requests that each add a change merge without
+a conflict. `crates/doc/src/format/pending/README.md` has an example.
+
+**At release time** the maintainer runs `scripts/fold-format-pending.sh`, which moves the pending
+files into `crates/doc/src/format/v<N>/` and fixes that number for good (see
+[docs/releasing.md](docs/releasing.md)). Never add a file to a `v<N>/` folder afterwards.
+
+## Lists many changes add to
+
+Some files gain an item in many pull requests at once. They are kept so that two changes that
+each add an item only meet when their items are neighbours, which spares everyone a conflict
+and a fresh CI run:
+
+- **Message catalogs** (`assets/locales/*.json`): one message per line, sorted by id. Add your
+  message anywhere and run `cargo xtask lists --fix`; `cargo xtask lists` (in `cargo xtask ci`
+  and the Lists workflow) fails on an unsorted catalog or an id that appears twice.
+- **`mod` lines**: one per line, in the sorted group they belong to (`cargo fmt` keeps each group
+  sorted). Add a new module into the existing group, not as a new group at the end.
+- **Languages** (`crates/ui-egui/src/i18n.rs`): one per line, English first, then by id (a test
+  checks it).
+- **Generated files**: `THIRD-PARTY-LICENSES.txt` and `docs/features.md` are rewritten on `main`
+  after each merge by the Generated files workflow (`cargo xtask licences`, `cargo xtask
+  features`). Don't regenerate or edit them in a pull request.
+- **Design format**: one file per change, never an edit to a shared number (above).
+
 ## Sending a change
 
 1. Work is tracked in [GitHub issues](https://github.com/bherbruck/solidcraft/issues), labelled
-   by area (`area:kernel`, `area:sketch`, `area:doc`, `area:ui`, `area:infra`). Before starting,
-   comment on the issue so it gets the `in progress` label and two people don't build the same
-   thing. For anything bigger than a bug fix that has no issue yet, open one first.
+   by area (`area:kernel`, `area:sketch`, `area:doc`, `area:ui`, `area:infra`). For anything
+   bigger than a bug fix that has no issue yet, open one first. **Claim the issue with a draft
+   PR** before you start, so two people don't build the same thing:
+   - Check nobody has it: `gh pr list -R bherbruck/solidcraft --state open --search "#N"`.
+   - Branch from the latest `main`, commit `git commit --allow-empty -m "claim: #N"`, push, and
+     open a **draft** PR titled `<summary> (#N)`, e.g. `Fillet: variable radius along a chain (#123)`.
+   - **The lowest-numbered open PR for an issue wins.** If yours lost, close it (or offer to help
+     on the other one).
+   - Push work in progress at least daily. A draft with no pushes for 72 hours may be taken over:
+     comment on it first, then open your own claim.
+   - Mark the PR ready for review when it is done.
 2. Branch from `main` and keep the PR to one topic.
 3. Run `cargo xtask ci` before pushing. It runs fmt, the asset, licence and layer checks,
    clippy (`-D warnings`), then the tests with the wasm build check alongside. A PR has to pass it.
 4. Reference the issue (`Fixes #12`). In the PR, say what you tested and how. For geometry work, include the measured numbers (and
    the expected ones).
 
+Comment `/claim` on an issue to take it: you are assigned, it gets the `in progress` label, and
+the bot replies with the deadline. Open a draft PR referencing the issue within 72 hours, or the
+claim lapses and the issue is freed again; a claim with a PR is freed after 14 days without
+pushes. `/unclaim` releases it early (only you or a maintainer can). Issues a maintainer has
+taken are never freed automatically.
+
 Help reviewers see what the words mean. For observable CAD, UI or model behavior, please
 include actual descriptive screenshots or a short recording in the issue or PR. This evidence
 is required for changes or bugs that can be demonstrated in the app, including kernel,
@@ -226,6 +297,8 @@ long as the change meets the rules above.
 
 ## Where help is wanted most
 
+**Kernel speed (slow fillets, booleans, STEP):** please don't rewrite the current kernel code for speed; it is being replaced by [solidcore](https://github.com/bherbruck/solidcore) ([progress](https://bherbruck.github.io/solidcore/)). Report slow cases with a file under the `kernel-perf` label, and put kernel effort into solidcore instead. See [#1597](https://github.com/bherbruck/solidcraft/issues/1597).
+
 See the [`help wanted`](https://github.com/bherbruck/solidcraft/labels/help%20wanted) and
 [`good first issue`](https://github.com/bherbruck/solidcraft/labels/good%20first%20issue) labels.
 In order of how much they'd help users:

Cargo.toml

@@ -5,7 +5,7 @@ members = ["crates/*", "apps/*", "xtask"]
 exclude = ["vendor"]
 
 [workspace.package]
-version = "0.11.0"
+version = "0.14.0"
 edition = "2024"
 license = "MIT OR Apache-2.0"
 rust-version = "1.95"
@@ -36,6 +36,7 @@ syn = { version = "2", features = ["full"] }
 serde_json = { version = "1", features = ["float_roundtrip"] }
 log = "0.4"
 sha2 = "0.10"
+moxcms = { version = "0.8.1", default-features = false, features = ["extended_range"] }
 semver = "1"
 
 # geometry kernel (Apache-2.0; see plan/adr/0001-geometry-kernel.md). Only crates/kernel uses it.
@@ -52,6 +53,17 @@ rayon = "1.12"
 # packages (3MF)
 zip = { version = "3", default-features = false, features = ["deflate"] }
 quick-xml = "0.41"
+# glTF 2.0 import (MIT OR Apache-2.0): the document model and GLB container only; buffers are
+# read by crates/io itself, so no image decoding or file access comes with it.
+gltf = { version = "1.4", default-features = false, features = ["names"] }
+
+# FreeCAD and Rhino import (Apache-2.0, pure Rust apart from zstd; native builds only).
+# Pinned: its IR and codec APIs change between minor versions. Open formats only: no default
+# features, so cadmpeg's codecs for commercial formats (f3d, sldprt, inventor, catia, creo, nx)
+# and its ShapeManager/ACIS `sat` codec are not compiled in. `step` is the writer we restate through.
+cadmpeg-core = "=0.6.1"
+cadmpeg-ir = "=0.6.1"
+cadmpeg-registry = { version = "=0.6.1", default-features = false, features = ["fcstd", "rhino", "step"] }
 
 # fonts (sketch text outlines; MIT OR Apache-2.0, pure Rust)
 ttf-parser = { version = "0.25", default-features = false, features = ["std"] }
@@ -114,6 +126,7 @@ debug = "line-tables-only"
 
 # truck-shapeops with SolidCraft fixes (Apache-2.0, see vendor/truck-shapeops and ATTRIBUTION.md).
 [patch.crates-io]
+truck-geometry = { path = "vendor/truck-geometry" }
 truck-shapeops = { path = "vendor/truck-shapeops" }
 truck-stepio = { path = "vendor/truck-stepio" }
 truck-meshalgo = { path = "vendor/truck-meshalgo" }

README.md

@@ -82,6 +82,9 @@ rebuild with no errors, replayed here at 2× speed.
 
 ## What works
 
+- **Current-view DXF export** from File → Export Current View as DXF, with hidden edges
+  omitted or dashed, shown body placements and the current camera. See [view DXF](docs/view-dxf.md).
+
 - **Sketches** on origin planes, offset planes or planar faces: lines, rectangles, circles,
   arcs, polygons, slots, ellipses, fit/control splines, conics and text; construction geometry,
   projection, trimming, fillets and chamfers, including corners at the origin.
@@ -129,13 +132,16 @@ rebuild with no errors, replayed here at 2× speed.
   components as assemblies; revolved faces as native planes, cylinders, cones, spheres and tori),
   IGES 5.3 (manifold solid B-reps with names and colours), 3MF, STL (binary/ASCII) and OBJ, and
   assemblies with joints as URDF for robot simulators (docs/urdf.md);
-  3MF, STL and OBJ import as mesh bodies (they render, measure, move and export; solid features
+  3MF, STL, OBJ and glTF 2.0 (`.glb`/`.gltf`, its node tree as components and its materials as
+  appearances) import as mesh bodies (they render, measure, move and export; solid features
   need B-rep bodies). The `mesh.convert` command reconstructs supported closed constant-section parts
   as parametric solids with planar and circular cylindrical faces;
   STEP import (AP203/AP214/AP242 solids, assemblies, units, names, colours) and IGES import
   (manifold solid B-reps, or trimmed and bounded surfaces sewn into solids) as a base feature
   that later features build on — open a `.step`/`.stp`/`.igs`/`.iges` file, insert one into a
-  design, or drop it on the window ([docs/step-import.md](docs/step-import.md)).
+  design, or drop it on the window ([docs/step-import.md](docs/step-import.md)); FreeCAD
+  `.FCStd` and Rhino `.3dm` solids import the same way through
+  [cadmpeg](https://github.com/cadmpeg/cadmpeg) in the desktop app and CLI.
 - **Render:** opaque surfaces can use metal fraction, roughness and dielectric IOR in the
   integrated product viewport and CPU preview PNGs. Existing simple colors remain supported.
   Fixed direct lighting is a preview; HDRI, refraction and texture maps are not implemented.
@@ -178,7 +184,13 @@ Windows builds: `cargo xwin build --release --target x86_64-pc-windows-msvc -p s
 On Windows and Linux, SolidCraft detects a connected 3Dconnexion SpaceNavigator or SpaceMouse through its
 multi-axis HID interface. Move the cap to pan and zoom, and tilt or twist it to rotate the 3D view.
 While editing a sketch, the cap pans and zooms without changing the sketch view. The Navigation
-page in Preferences has an on/off switch and a speed control for the 3D mouse.
+page in Preferences has an on/off switch and a speed control for the 3D mouse. The web app reads
+it too, through the browser; Firefox needs a 3DxWare setting first (see
+[Getting started › 3D mouse in the browser](docs/book/src/guide/getting-started.md#3d-mouse-in-the-browser)).
+
+With 3DxWare on Windows, SolidCraft follows 3DxWare's profile for it when there is one, and
+3DxWare's object mode (tilt to roll, twist to spin) until there is. The mouse-wheel turns that
+3DxWare makes from the cap's motion are ignored, so the view doesn't zoom in steps as the cap tilts.
 
 On Linux SolidCraft reads `/dev/hidrawN` directly, so the logged-in user needs access to the
 device. A udev rule that adds the `uaccess` tag does that, for example
@@ -228,9 +240,9 @@ configuration and an example session: [docs/mcp.md](docs/mcp.md).
 | Layer | Crates | Role |
 |---|---|---|
 | L0 | `geom` | vectors, planes, profiles, meshes and their measures |
-| L1 | `sketch`, `kernel`, `render` | constraint solver and profiles; the B-rep kernel boundary (truck); view math and CPU rasterizer |
+| L1 | `sketch`, `kernel`, `render` | constraint solver and profiles; the B-rep kernel boundary (truck); view math and the headless scene description |
 | L2 | `doc` | parameters, expressions, the feature timeline and its incremental evaluation |
-| L3 | `io` | design files, STL/OBJ/STEP/3MF export, STEP and 3MF/STL import features |
+| L3 | `io` | design files, STL/OBJ/STEP/3MF export, STEP and 3MF/STL/OBJ/glTF import features |
 | L4 | `engine` | the session and the command registry (everything is a command) |
 | L5 | `gpu`, `ui-egui`, `mcp` | compute-shader evaluation of display tessellation plans; the swappable desktop front end; the MCP server (headless or bridged to the app) |
 | apps | `solidcraft`, `solidcraft-cli` | desktop app, headless CLI |

ROADMAP.md

@@ -7,7 +7,7 @@ features → parametric timeline) as an open, pure-Rust, agent-drivable applicat
 
 | Question | Answer |
 |---|---|
-| Where are we? | **M0 and M13 done; M1, M2, M5–M7, M9, M10, M14 in progress.** Sketch with solver and the full SKETCH create/modify set; extrude, revolve (two sides, symmetric, to object), fillet/chamfer (variable radius, chord length, a radius per edge, corner patches), holes, threads (cosmetic and modelled), patterns, mirror, shell (inside/outside/both), draft, loft, sweep, coil, split body and split face, delete face, construction planes, axes and points; persistent naming of faces and edges; parameters and configurations; components, joints, motion studies, exploded views; sheet metal and a plastic enclosure subset; STEP/IGES/3MF/STL/OBJ/DXF; autosave and crash recovery; desktop and browser (wasm) app, CLI, MCP server. |
+| Where are we? | **M0 and M13 done; M1, M2, M5–M7, M9, M10, M14 in progress.** Sketch with solver and the full SKETCH create/modify set; extrude, revolve (two sides, symmetric, to object), fillet/chamfer (variable radius, chord length, a radius per edge, corner patches), holes, threads (cosmetic and modelled), patterns, mirror, shell (inside/outside/both), draft, loft, sweep, coil, split body and split face, delete face, construction planes, axes and points; persistent naming of faces and edges; parameters and configurations; components, joints, motion studies, exploded views; sheet metal and a plastic enclosure subset; STEP/IGES/3MF/STL/OBJ/DXF; FreeCAD/Rhino import; autosave and crash recovery; desktop and browser (wasm) app, CLI, MCP server. |
 | Features | Every registered command by area — [docs/features.md](docs/features.md) (`cargo xtask features`); registry breadth does not establish workflow or geometric depth |
 | Reference tests | **82 / 82 parts match** — [docs/oracle.md](docs/oracle.md): public cases in `tests/oracle/` with analytic (61) or FreeCAD-computed (21) expected values, run by CI on every PR. |
 | Tests | Solver, profiles, kernel booleans/blends/measures, expressions, timeline, persistent naming, file formats and migrations, assemblies, sheet metal, engine end-to-end, hostile-input fuzz over every command and headless UI scenarios. `cargo xtask ci` reports the current passing counts. |
@@ -21,6 +21,8 @@ offsets and plastic face placements, XZ (+Y normal) with a v6 migration preservi
 designs, interactive angle placement, file-picker sketch imports, Home/recent controls,
 toolbar overflow, and the remaining component-frame and assembly WIP work. The enclosure
 acceptance scenarios now include board resizes; STEP reopening is automated. See [WIP reconciliation](docs/wip-reconciliation.md).
+Face-based Extrude Join (including outward Press Pull) now defaults to the picked body,
+so edge-touching assembly neighbours stay separate regardless of body order (#226).
 
 In scope, in priority order:
 1. SOLID and SKETCH (now).
@@ -47,12 +49,15 @@ PCB / Package, Render, Animation, Simulation, Manufacture/CAM, Drawings.
 | M1 | Sketch depth: command coverage implemented — projection/intersect/include as linked geometry (auto-project on faces, lost-reference warnings, break link), full SKETCH create/modify set (slots, polygons, tangent arcs/circles, ellipse, fit/control splines, conic, text, trim/extend/break, fillet/chamfer, offset, mirror, patterns, move/scale, blend curve, centerline), constraints incl. curvature and polygon with over-constraint refusal, driven/arc-length/linear-diameter dimensions, AutoConstrain, DXF/SVG insert, 3D sketch curves (Project To Surface, Intersection Curve, Isoparametric Curve, Spun Profile), exact free-form profiles (B-spline/NURBS edges, any spline degree, curves cut by crossings), sweeps and pipes along 3D sketch curves, canvases and decals, curvature combs. Exact free-form Extend and certified associative offsets now preserve geometry and IDs through edits, deletion and reopen. Occurrence-frame 3D wires now store explicit coordinate spaces and retain points and analytic fits through moves, refresh, undo and reopen. Constructive sketch solving (Owen 1991, Fudos & Hoffmann 1997) ahead of the numerical solver: points and rigid clusters are placed on the branch the sketch had, so dimension edits and drags keep their solution; edits that would turn a sketch over are refused; drags re-solve only the sketch per frame. Remaining workflow repairs: mixed offset junctions, legacy natural-spline seams, and damaged legacy wire links lacking frame provenance | in progress | 4 |
 | M2 | Robust modelling: coplanar booleans in the kernel, holes (placed on faces and on sketch points), threads (cosmetic, then modelled), patterns, mirror, shell, draft, split, construction geometry | in progress | 16 |
 | M3 | General fillets and chamfers (curved edges, chains, vertex blends); saddle rolling-ball surfaces now use continuous seam sections and arc-length fitting with shared contact boundaries and bounded accuracy checks | in progress | 30 |
-| M4 | Files: STEP import (done — [docs/step-import.md](docs/step-import.md)), 3MF export and 3MF/STL import as mesh bodies (done), 3MF with B-rep face tags ([docs/formats/3mf-face-tags.md](docs/formats/3mf-face-tags.md), done), constant-section parametric mesh reconstruction, DXF sketches, OBJ import | in progress | 6 |
+| M4 | Files: STEP import (done — [docs/step-import.md](docs/step-import.md)), FreeCAD/Rhino solids through cadmpeg (done, desktop and CLI), 3MF export and 3MF/STL import as mesh bodies (done), 3MF with B-rep face tags ([docs/formats/3mf-face-tags.md](docs/formats/3mf-face-tags.md), done), constant-section parametric mesh reconstruction, DXF sketches, OBJ import | in progress | 6 |
 | M5 | Persistent naming of faces and edges (docs/book/src/dev/naming.md): faces named from their exact kernel-reported history (sketch curve sides, caps, revolve sections, primitive sides, blends, shell inner walls, pattern/mirror copies; split pieces told apart by the faces around them, lumps of a cut body named after their faces), edges by their faces; fillets/chamfers, sketches on faces, shell/draft/offset/replace faces, hole placements, joint origins and face appearances resolve by name first and warn when the entity split or vanished: done. sheet metal edges by base sketch line and flange side, shell inner faces, sweep and loft roles: done. kernel-reported face history: done (merged faces answer to every name; operations without history yet fall back to geometric names, flagged unverified; format 14 keeps older designs' geometric names). Left: history through sheet metal, plastic, surface and emboss features; FaceSource certificates through history | in progress | 20 |
 | M6 | UI depth: selection feedback and origin (done), timeline editing (done: hover and selection highlight modifier faces, including fillets and chamfers; edit feature, history marker drag, dependency-checked single and multi-item reorder, suppress, rename, delete with dependents, re-resolved references; redefining selections refreshes persistent edge/face references while retaining feature identity and dimension names; optional compact named left feature history with rollback bar, multi-selection and persistent folders above the parts browser), right-docked dialogs (done), live previews for every feature dialog (done), keyboard-first commands with on-canvas value boxes and sketch inline dimensions (done), drag manipulators with automatic join/cut (done: extrude incl. two sides, fillet, shell, hole depth, move, pattern spacing, revolve rotator; taper handle open), dark theme (done), right-click menu with Repeat (done), measure tool (done), section analysis (done), selection filter (done), drag-solve of sketch points (done); appearance controls now preserve body/face/component targeting, named transparent looks, reuse/search and override removal; preferences | in progress | 6 |
 | M7 | Thin extrude (walls along open or closed curves: centre, inside, outside or two sides; mitred corners, crossing walls joined; #721), sweep, loft (incl. to a point), rib and web (to next / depth), emboss (planar faces and exact radial emboss/deboss of bounded orthogonal profiles on complete exterior cylinders/sleeves), thread (cosmetic, and modelled M3–M20 outside and inside: the ISO profile screwed in as a faceted cut), coil (smooth B-spline helical walls), pipe, pattern on path, patterns of bodies and components, replace face (parallel), align, remove, feature copy/paste: done. Unique eligible cylindrical targets are inferred for new Emboss features. Left: general curved-face emboss and exact (unfaceted) modelled threads | in progress | 12 |
-| M8 | Surface workspace (#772). Done: Patch (sketch regions; edge loops filled G0), Stitch, Thicken (planes and cylinders), Extend (straight edges of planar surfaces), Trim (by a plane or a face), Delete Face (healing), Boundary Fill, zebra/draft/curvature-map analysis. Proposed, in order: surface Extrude/Revolve/Sweep/Loft from open and closed curves (#757), Offset surface (#758), Unstitch and Reverse Normal (#766), Delete Face without healing (#768); Extend curved faces and edges (#760), mutual trim and trim by projected curves (#767), Untrim (#761), Thicken every surface kind (#765); Ruled (#762), Boundary surface and curve networks with G0/G1/G2 (#763), Patch with G1/G2 and general loops (#759), Blend surface (#764), sweep rails, twist and scale (#771, loft rails #201), fillet between surface bodies (#769); continuity analysis, surface curvature combs and isocurves (#770) | deferred | — |
+| M8 | Surface workspace (#772). Done: Patch (sketch regions; edge loops of any shape and number of sides as one face, G0/G1/G2 to the faces beside each edge, through points, #759), Stitch, Thicken (planes and cylinders), Extend (straight edges of planar surfaces), Trim (by a plane or a face), Delete Face (healing), Boundary Fill, zebra/draft/curvature-map analysis. Proposed, in order: surface Extrude/Revolve/Sweep/Loft from open and closed curves (#757), Offset surface (#758), Unstitch and Reverse Normal (#766), Delete Face without healing (#768); Extend curved faces and edges (#760), mutual trim and trim by projected curves (#767), Untrim (#761), Thicken every surface kind (#765); Ruled (#762), Boundary surface and curve networks with G0/G1/G2 (#763), Blend surface (#764), sweep guide rails and two-rail sweeps (#771; orientation, twist and end scale done; loft rails #201), fillet between surface bodies (#769); continuity analysis, surface curvature combs and isocurves (#770) | deferred | — |
 | M9 | Components and assemblies: New Component / Create Components from Bodies, active component, per-component origin/bodies/sketches/timeline entries, occurrences with transforms, Copy/Paste vs Paste New, nested Browser tree with visibility and isolate; Ground, Move/Copy of occurrences, joints (rigid, revolute, slider, cylindrical, pin-slot, planar, ball) by joint origins with limits and Drive Joints, closed kinematic loops (four-bar, slider-crank: the loop's other joints follow the driven one on its branch, and driving stops where a loop can no longer close), As-built Joint, Rigid Group, Contact Sets (driving and motion studies stop where bodies in a set would pass through each other), Motion Study (joint values keyed along a timeline, playback, export of occurrence positions as JSON/CSV), Exploded views (automatic or by hand, shown without changing placements); interference, per-component physical properties; STEP with assembly structure; URDF export for robot simulators (links with meshes, mass and inertia; joint chains whose values match Drive Joints; docs/urdf.md). Physical properties now measure material-aware component/occurrence placements, descendants and repeated instances, including pending moves and body reassignment offsets; contact geometry and automatic exploded centres respect those offsets. Groundwork done: component tree, occurrences with transforms (instances, Paste New), world placement, active component as authoring frame, ground, Capture/Revert Position, moving bodies and sketches. UI: ASSEMBLE panel dialogs for New Component, Joint (snaps on faces, edges, circles and vertices; animated motion preview; offsets, flip, limits), As-built Joint, Joint Origin, Rigid Group, Drive Joints (live slider), Motion Link and Interference (overlaps shown red); joints in the timeline and the Browser | in progress | 32 |
+| M8 | Surface workspace (#772). Done: Patch (sketch regions; edge loops filled G0), Stitch, Thicken (planes and cylinders), Extend (straight edges of planar surfaces), Trim (by a plane or a face), Delete Face (healing), Boundary Fill, zebra/draft/curvature-map analysis. Proposed, in order: surface Extrude/Revolve/Sweep/Loft from open and closed curves (#757), Offset surface (#758), Unstitch and Reverse Normal (#766), Delete Face without healing (#768); Extend curved faces and edges (#760), mutual trim and trim by projected curves (#767), Untrim (#761), Thicken every surface kind (#765); Ruled (#762), Boundary surface and curve networks with G0/G1/G2 (#763), Patch with G1/G2 and general loops (#759), Blend surface (#764), sweep guide rails and two-rail sweeps (#771; orientation, twist and end scale done; loft rails #201), fillet between surface bodies (#769); continuity analysis, surface curvature combs and isocurves (#770) | deferred | — |
+| M9 | Components and assemblies: New Component / Create Components from Bodies, active component, per-component origin/bodies/sketches/timeline entries, occurrences with transforms, Copy/Paste vs Paste New, nested Browser tree with visibility and isolate; Ground, Move/Copy of occurrences, joints (rigid, revolute, slider, cylindrical, pin-slot, planar, ball) by joint origins with limits and Drive Joints, closed kinematic loops (four-bar, slider-crank: the loop's other joints follow the driven one on its branch, and driving stops where a loop can no longer close), gears, rack and pinion and screws (motion links whose ratio follows picked radii, parameters or a pitch, also inside closed loops), As-built Joint, Rigid Group, Contact Sets (driving and motion studies stop where bodies in a set would pass through each other), Motion Study (joint values keyed along a timeline, playback, export of occurrence positions as JSON/CSV), Motion Trace (a picked point's path as a joint is driven or a study plays, closed loops following; kept as a 3D sketch spline), Exploded views (automatic or by hand, shown without changing placements); interference, per-component physical properties; STEP with assembly structure; URDF export for robot simulators (links with meshes, mass and inertia; joint chains whose values match Drive Joints; docs/urdf.md). Physical properties now measure material-aware component/occurrence placements, descendants and repeated instances, including pending moves and body reassignment offsets; contact geometry and automatic exploded centres respect those offsets. Groundwork done: component tree, occurrences with transforms (instances, Paste New), world placement, active component as authoring frame, ground, Capture/Revert Position, moving bodies and sketches. UI: ASSEMBLE panel dialogs for New Component, Joint (snaps on faces, edges, circles and vertices; animated motion preview; offsets, flip, limits), As-built Joint, Joint Origin, Rigid Group, Drive Joints (live slider), Motion Link, Gear, Rack and Pinion, Screw and Interference (overlaps shown red); joints in the timeline and the Browser | in progress | 32 |
+| M9 | Components and assemblies: New Component / Create Components from Bodies, active component, per-component origin/bodies/sketches/timeline entries, occurrences with transforms, Copy/Paste vs Paste New, nested Browser tree with visibility and isolate; Ground, Move/Copy of occurrences, joints (rigid, revolute, slider, cylindrical, pin-slot, planar, ball) by joint origins with limits and Drive Joints, closed kinematic loops (four-bar, slider-crank: the loop's other joints follow the driven one on its branch, and driving stops where a loop can no longer close), gears, rack and pinion and screws (motion links whose ratio follows picked radii, parameters or a pitch, also inside closed loops), inverse kinematics (`joint.reach`: a part's point to a target through the joints on its chain, within limits and with loops closed, nearest pose and its stopper when out of reach; dragging a jointed part in the viewport moves it as far as its joints allow), As-built Joint, Rigid Group, Contact Sets (driving and motion studies stop where bodies in a set would pass through each other), Motion Study (joint values keyed along a timeline, playback, export of occurrence positions as JSON/CSV), Exploded views (automatic or by hand, shown without changing placements); interference, per-component physical properties; STEP with assembly structure; URDF export for robot simulators (links with meshes, mass and inertia; joint chains whose values match Drive Joints; docs/urdf.md). Physical properties now measure material-aware component/occurrence placements, descendants and repeated instances, including pending moves and body reassignment offsets; contact geometry and automatic exploded centres respect those offsets. Groundwork done: component tree, occurrences with transforms (instances, Paste New), world placement, active component as authoring frame, ground, Capture/Revert Position, moving bodies and sketches. UI: ASSEMBLE panel dialogs for New Component, Joint (snaps on faces, edges, circles and vertices; animated motion preview; offsets, flip, limits), As-built Joint, Joint Origin, Rigid Group, Drive Joints (live slider), Motion Link, Gear, Rack and Pinion, Screw and Interference (overlaps shown red); joints in the timeline and the Browser | in progress | 32 |
 | M10 | Sheet metal: flange (base, edge, contour), hem, unfold/refold, convert, flat pattern + DXF, rules: done. PLASTIC enclosure subset: Boss, Rib, Web, Lip/Groove, Snap Fit, Rest, Plastic Rules (library, edit, assign; rule draft and clearance as feature defaults): done, tested against hand-computed geometry. UI: SHEET METAL and PLASTIC tabs in Fusion's layout with dialogs (live preview, Edit Feature, pre-selection) for Flange, Hem, Unfold/Refold, Convert, Sheet Metal Rules, Create Flat Pattern (flat view with bend lines, bend table CSV/JSON and DXF export with exact circle/arc/line cutouts), Boss, Lip/Groove, Snap Fit, Rest, Manage and Assign Plastic Rules; Fold (bend along a sketch line); flanges meeting at a corner closed at any angle with the rule's gap; edge flanges with their own angle and height per edge in one feature; corner reliefs (notch, round, rectangular, tear) chosen by the rule; Convert to Sheet Metal from a solid or shelled body by its bend edges (flat faces, sharp bends) | in progress | 36 |
 | M11 | 2D drawings | deferred | — |
 | M12 | Release: cross-platform packages, verification and deliberate publication implemented; original current-UI demo refreshed. Trusted distribution signing and broader performance work remain | in progress | 16 |
@@ -64,6 +69,18 @@ pointer movement orbits without a mouse button, and vertical scrolling zooms. Ot
 retain their saved two-finger scroll preference; camera motion is available through
 `view.navigate` and modifier-aware `ui.move` automation.
 
+M11 precursor: File → Export Current View as DXF exports shown placed bodies from the current
+camera as a 2D millimetre drawing, with hidden edges omitted or dashed. Vector occlusion splits
+partly hidden edges and includes curved silhouettes. Curves are approximated; drawing sheets,
+annotations and exact projected curves remain deferred. See [view DXF](docs/view-dxf.md).
+
+## Interactive modelling
+
+- New Body extrusion and face-offset previews show completed intermediate geometry while a
+  drag continues, then catch up to the exact final value. Changes to the selected geometry,
+  operation or feature still discard obsolete results. Distance arrows and their value boxes
+  follow the current frame's input.
+
 ## Physical material data
 
 - Physical material card validation (#923/#922) provides typed SI mechanical and
@@ -94,6 +111,12 @@ retain their saved two-finger scroll preference; camera motion is available thro
 
 ## Render foundation
 
+- Explicit texture normalization (#1218) produces completed float RGBA with
+  role-aware linear color/data semantics, bounded matrix/TRC ICC conversion and
+  opt-in EXIF orientation. It retains high-precision raw samples and records lossy
+  gamut clipping only when explicitly requested. It is not a renderer/resource
+  consumer; see [the supported policy and limits](docs/render-texture-normalization.md).
+
 - Opt-in opaque PBR (#1046) connects persisted surface parameters to the integrated
   product viewport and CPU PNG, using a fixed direct-light studio. Geometry and mass
   stay unchanged. HDRI, transmission and textures remain separate gates.
@@ -207,6 +230,14 @@ retain their saved two-finger scroll preference; camera motion is available thro
   Crash Reports…) with a reviewed issue draft; agents read them through
   `diagnostics.crash_reports`, the MCP `crash_reports` tool or the CLI. Nothing is sent
   anywhere. See [crash reports](docs/crash-reports.md).
+- Agent chat (off by default, desktop): a side panel that drives a coding agent the user
+  already has (Claude Code through its ACP adapter, Codex, Gemini CLI, OpenCode, Grok Build, …) over the
+  Agent Client Protocol, under the user's own login; SolidCraft stores no keys. The agent works
+  through SolidCraft's MCP tools on a gated endpoint of its own: file actions wait for Allow or
+  Deny, crash reports are off limits, 24 changes per message, one undo step per message, and
+  the agent's whole process group ends with the panel or the app. Docks left or right,
+  minimises to a strip. Grok Build discovery includes `~/.grok/bin` and reuses the user's
+  Grok login. See [agent chat](docs/agent-chat.md).
 - Command scripts from designs (#886): `timeline.export_script` (CLI `solidcraft-cli script`)
   writes a design's history as a script that `eval` and `run` replay into the same design —
   user parameters, units, sheet metal and plastic rules and materials as their own commands,
@@ -279,11 +310,15 @@ retain their saved two-finger scroll preference; camera motion is available thro
   is an equivalent circular setback. Curved faces/edges, sloped ends and corner junctions remain unsupported.
 - Fillets and chamfers: constant, variable-radius and chord-length fillets; a radius per edge,
   rounds next to earlier rounds of another radius, and smooth corner patches where three rounds
-  meet (a sphere for equal radii); straight edges (convex or concave) between planar faces with perpendicular
+  meet (a sphere for equal radii); perpendicular corner fillets after a closed ring of earlier
+  rounds preserve the ring's radii and the enclosed planar face (#1557);
+  straight edges (convex or concave) between planar faces with perpendicular
   planar end faces (equal-distance chamfers also meet sloped planar end faces, including inner
   basin rims within the rim width); convex fillets also meet sloped planar ends and reflex
   corners around pocket rims, with unequal wall slopes and extensions confined to the face;
   connected equal-distance chamfers also trim each other across unequal sloped rim walls;
+  curved chamfer chains with straight planar ends can terminate across two existing planar
+  bevel faces, splitting their shared seam; picks on the same tangent chain are applied once (#1303);
   whole smooth loops of a planar face, picked whole or by one edge (tangent
   chain), including circles and walls at any angle (boss bases and tops, bores, pocket floors,
   plate outlines), loops with sharp corners between straight edges (the blends meet in mitres), runs of
@@ -336,6 +371,9 @@ retain their saved two-finger scroll preference; camera motion is available thro
   and conics; analytic trim/break also sees free-form cutters. Free-form curves cut at a tangent
   touch (no clean crossing) enter that profile as polylines.
   Sweeps along 3D sketch curves follow their polyline (smooth walls when the path is smooth).
+  A sweep with a twist, an end scale or a parallel or direction orientation (#771) follows its
+  path that way too, even along sketch lines and arcs: B-spline walls through stations, ruled
+  walls through denser stations where the path has corners or the profile has holes.
 - Extend intersects exact ellipses and rational/high-degree splines without moving the line or
   circular support. Associative free-form offsets have a whole-span 0.002 mm normal-distance
   certificate and refine within bounded node limits while retaining existing IDs.

apps/solidcraft-cli/Cargo.toml

@@ -21,5 +21,10 @@ path = "src/alias.rs"
 
 [dependencies]
 solidcraft-engine = { workspace = true }
+solidcraft-gpu = { workspace = true }
 solidcraft-mcp = { workspace = true }
 serde_json = { workspace = true }
+
+[dev-dependencies]
+# Snapshot tests decode the pictures to compare them with a tolerance.
+image = { workspace = true }

apps/solidcraft-cli/src/main.rs

@@ -34,7 +34,6 @@ use serde_json::{Value, json};
 mod app_icon;
 
 use solidcraft_engine::Session;
-use solidcraft_engine::render::render_png;
 use solidcraft_engine::view::Guides;
 
 const USAGE: &str = "usage:
@@ -63,6 +62,10 @@ const USAGE: &str = "usage:
   solidcraft-cli mcp [--in design.solidcraft|script.json] [--connect 127.0.0.1:PORT [--token T]] [--allow-path DIR]... [--allow-any-path]
   solidcraft-cli crashes [list [--json] | show <id> | replay <id> | dir | clear [<id>]]
   solidcraft-cli licences
+  solidcraft-cli gpu [--policy auto|hardware|software|cpu]
+      (the GPU adapters a headless render can open, best first, the one the policy picks and the tier it
+       lands on: gpu, gpu-software, or the CPU rasterizer (auto with no adapter, or cpu); the policy defaults
+       to SOLIDCRAFT_GPU, else auto; exits with an error when hardware or software finds no such adapter)
   solidcraft-cli icon --out icon.png [--size 256] | --out icon.ico
 ";
 
@@ -75,6 +78,7 @@ fn main() -> ExitCode {
         Some("snapshot") => cmd_snapshot(&args[1..]),
         Some("render") => render::run(&args[1..]),
         Some("exec") => cmd_exec(&args[1..]),
+        Some("gpu") => cmd_gpu(&args[1..]),
         Some("commands") => {
             use std::io::Write as _;
             let mut s = Session::default();
@@ -213,6 +217,7 @@ fn print_json(v: &Value, file: Option<&str>) -> Result<(), String> {
 }
 
 fn cmd_run(args: &[String]) -> Result<(), String> {
+    install_renderer();
     let json_out = json_out(args)?;
     let base = flag(args, "--in");
     let path = positional(args);
@@ -334,13 +339,59 @@ fn cmd_script(args: &[String]) -> Result<(), String> {
     Ok(())
 }
 
+/// `gpu`: the headless adapter survey and the policy's pick.
+fn cmd_gpu(args: &[String]) -> Result<(), String> {
+    use solidcraft_gpu::select::{Policy, survey};
+    let policy = match args {
+        [] => Policy::from_env()?,
+        [flag, v] if flag == "--policy" => Policy::parse(v).ok_or_else(|| format!("--policy must be auto, hardware, software or cpu, not `{v}`"))?,
+        _ => return Err("usage: solidcraft-cli gpu [--policy auto|hardware|software|cpu]".into()),
+    };
+    let s = survey(policy);
+    let chosen = s.chosen.and_then(|i| s.adapters.get(i)).cloned();
+    // The tier pictures land on: a hardware GPU, a software adapter, or the CPU rasterizer.
+    let renderer = s.lands_on.map(|l| l.renderer());
+    println!(
+        "{}",
+        pretty(&json!({
+            "policy": policy.name(),
+            "backends": s.backends,
+            "adapters": s.adapters,
+            "chosen": chosen,
+            "lands_on": s.lands_on,
+            "renderer": renderer,
+        }))
+    );
+    match s.lands_on {
+        Some(solidcraft_gpu::select::Landing::Cpu) => {
+            eprintln!("warning: {}", solidcraft_engine::capture::CPU_WARNING);
+            Ok(())
+        }
+        Some(_) => Ok(()),
+        None => Err(format!("no adapter qualifies under the {} policy", policy.name())),
+    }
+}
+
+/// Draw this process's pictures (snapshots, MCP screenshots, saved thumbnails) on the GPU with the
+/// viewport's pipelines: the headless device the `SOLIDCRAFT_GPU` policy picks, opened on the first
+/// picture; under `auto` with no qualifying adapter (or `cpu`), the CPU rasterizer, and the
+/// picture says so. Under `hardware` or `software` with no such adapter a picture fails with an
+/// error that names the policy.
+fn install_renderer() {
+    solidcraft_engine::capture::install(std::sync::Arc::new(|scene, cam, w, h| {
+        let (rgba, renderer) = solidcraft_gpu::capture::headless_rgba(scene, cam, w, h)?;
+        Ok(solidcraft_engine::capture::Picture { rgba, renderer })
+    }));
+}
+
 fn cmd_snapshot(args: &[String]) -> Result<(), String> {
+    install_renderer();
     known_flags("snapshot", args, &["--in", "--out", "--width", "--height", "--view", "--camera"], &["--no-grid", "--no-axes"])?;
     if positional(args).is_none() && flag(args, "--in").is_none() {
         return Err(USAGE.to_string());
     }
     let out = flag(args, "--out").ok_or("snapshot needs --out FILE.png")?;
-    let size = |name: &str, default: usize| match flag(args, name) {
+    let size = |name: &str, default: u32| match flag(args, name) {
         None => Ok(default),
         Some(x) => x.parse().ok().filter(|n| (16..=8192).contains(n)).ok_or_else(|| format!("{name} must be 16 to 8192 pixels, not `{x}`")),
     };
@@ -364,9 +415,14 @@ fn cmd_snapshot(args: &[String]) -> Result<(), String> {
     let cam = s.camera.unwrap_or_else(|| solidcraft_engine::view::home_camera(&s));
     let guides = Guides { grid: !args.iter().any(|a| a == "--no-grid"), axes: !args.iter().any(|a| a == "--no-axes") };
     let scene = solidcraft_engine::view::scene_with_guides(&s, &cam, s.section, guides);
-    let png = render_png(&scene, &cam, w, h).ok_or("render failed")?;
-    std::fs::write(out, &png).map_err(|e| format!("{out}: {e}"))?;
-    println!("{}", pretty(&json!({"path": out, "width": w, "height": h, "bytes": png.len()})));
+    let png = solidcraft_engine::capture::png(&scene, &cam, w, h)?;
+    std::fs::write(out, &png.bytes).map_err(|e| format!("{out}: {e}"))?;
+    let mut reply = json!({"path": out, "width": w, "height": h, "bytes": png.bytes.len(), "renderer": png.renderer});
+    if let Some(w) = solidcraft_engine::capture::warning(png.renderer) {
+        eprintln!("warning: {w}");
+        reply["warning"] = json!(w);
+    }
+    println!("{}", pretty(&reply));
     Ok(())
 }
 
@@ -412,6 +468,7 @@ fn ico(images: &[(usize, Vec<u8>)]) -> Result<Vec<u8>, String> {
 }
 
 fn cmd_exec(args: &[String]) -> Result<(), String> {
+    install_renderer();
     let id = args.first().ok_or_else(|| USAGE.to_string())?;
     let p: Value = match args.get(1) {
         Some(t) => serde_json::from_str(t).map_err(|e| format!("params: {e}"))?,
@@ -427,6 +484,7 @@ fn cmd_exec(args: &[String]) -> Result<(), String> {
 /// a running app's control port. stdout carries only protocol messages. Files the agent's tool
 /// calls reach are confined to `solidcraft_mcp::agent_scope` unless `--allow-any-path` is given.
 fn cmd_mcp(args: &[String]) -> Result<(), String> {
+    install_renderer();
     let scope = (!args.iter().any(|a| a == "--allow-any-path"))
         .then(|| solidcraft_mcp::agent_scope(flags(args, "--allow-path").into_iter().map(std::path::PathBuf::from)));
     if let Some(s) = &scope {

apps/solidcraft-cli/tests/run_results.rs

@@ -151,11 +151,20 @@ fn snapshot_runs_its_script_on_the_in_design() {
         json_output(cli().arg("snapshot").args(args).arg("--out").arg(&png).args(["--width", "64", "--height", "48"]).output().unwrap());
         std::fs::read(&png).unwrap()
     };
-    let alone = shot("alone.png", &[shifted.as_os_str()]);
-    let on_base = shot("on_base.png", &[shifted.as_os_str(), "--in".as_ref(), base.as_os_str()]);
-    let base_only = shot("base.png", &["--in".as_ref(), base.as_os_str()]);
-    assert_ne!(alone, on_base, "the script ran on the --in design");
-    assert_ne!(base_only, on_base);
+    // Pictures are drawn on the GPU: without an adapter only the option checks below run.
+    match solidcraft_gpu::capture::shared() {
+        Ok(_) => {
+            let alone = shot("alone.png", &[shifted.as_os_str()]);
+            let on_base = shot("on_base.png", &[shifted.as_os_str(), "--in".as_ref(), base.as_os_str()]);
+            let base_only = shot("base.png", &["--in".as_ref(), base.as_os_str()]);
+            assert_ne!(alone, on_base, "the script ran on the --in design");
+            assert_ne!(base_only, on_base);
+        }
+        Err(e @ solidcraft_gpu::GpuError::NoAdapter(_)) if std::env::var_os("SOLIDCRAFT_REQUIRE_GPU").is_none() => {
+            eprintln!("pictures left out: {e}")
+        }
+        Err(e) => panic!("{e}"),
+    }
     for (bad, says) in [(["--frobnicate", "1"], "doesn't take --frobnicate"), (["--width", "wide"], "--width must be 16 to 8192")] {
         let output = cli().arg("snapshot").arg(&base).arg("--out").arg(dir.0.join("x.png")).args(bad).output().unwrap();
         assert_eq!(output.status.code(), Some(1));

apps/solidcraft-cli/tests/snapshot_camera.rs

@@ -1,6 +1,8 @@
 //! `snapshot` frames its picture like the MCP `screenshot`: from a camera, a view saved in the
 //! design or one the script applies itself, and without the ground grid and the origin's axes
-//! when asked (the grid lies on Z 0 and cuts through a part that straddles it).
+//! when asked (the grid lies on Z 0 and cuts through a part that straddles it). Pictures are drawn
+//! on the GPU and compared with a tolerance; without a GPU adapter the tests that draw are skipped
+//! with the reason printed (`SOLIDCRAFT_REQUIRE_GPU=1` makes that a failure).
 
 use std::path::{Path, PathBuf};
 use std::process::{Command, Output};
@@ -12,7 +14,52 @@ use solidcraft_mcp::{Headless, Server};
 
 static NEXT: AtomicUsize = AtomicUsize::new(0);
 
-const SIZE: (usize, usize) = (160, 100);
+/// Whether pictures can be drawn here; installs the renderer the CLI installs, so the MCP
+/// `screenshot` in this process draws as `solidcraft-cli mcp` does.
+fn gpu() -> bool {
+    match solidcraft_gpu::capture::shared() {
+        Ok(c) => {
+            solidcraft_engine::capture::install(std::sync::Arc::new(move |scene, cam, w, h| {
+                c.rgba(scene, cam, w, h).map(|rgba| solidcraft_engine::capture::Picture { rgba, renderer: c.renderer() }).map_err(|e| e.to_string())
+            }));
+            true
+        }
+        Err(e @ solidcraft_gpu::GpuError::NoAdapter(_)) if std::env::var_os("SOLIDCRAFT_REQUIRE_GPU").is_none() => {
+            eprintln!("skipping: {e}");
+            false
+        }
+        Err(e) => panic!("{e}"),
+    }
+}
+
+/// A PNG's size and RGBA pixels.
+fn decode(png: &[u8]) -> (u32, u32, Vec<u8>) {
+    let img = image::load_from_memory_with_format(png, image::ImageFormat::Png).unwrap().to_rgba8();
+    (img.width(), img.height(), img.into_raw())
+}
+
+/// Pixels of two same-sized pictures that differ by more than a little in some channel.
+fn differing(a: &[u8], b: &[u8]) -> usize {
+    let ((wa, ha, a), (wb, hb, b)) = (decode(a), decode(b));
+    assert_eq!((wa, ha), (wb, hb), "pictures of different sizes");
+    a.as_chunks::<4>().0.iter().zip(b.as_chunks::<4>().0).filter(|(p, q)| p.iter().zip(q.iter()).any(|(x, y)| x.abs_diff(*y) > 16)).count()
+}
+
+/// The same picture: GPU output may differ by a few levels or a stray edge pixel between drivers.
+#[track_caller]
+fn assert_same(a: &[u8], b: &[u8], what: &str) {
+    let (n, total) = (differing(a, b), (SIZE.0 * SIZE.1) as usize);
+    assert!(n * 500 <= total, "{what}: {n} of {total} pixels differ");
+}
+
+/// Different pictures: more than stray pixels differ.
+#[track_caller]
+fn assert_differs(a: &[u8], b: &[u8], what: &str) {
+    let n = differing(a, b);
+    assert!(n >= 20, "{what}: only {n} pixels differ");
+}
+
+const SIZE: (u32, u32) = (160, 100);
 
 fn camera() -> Value {
     json!({"target": [20, 0, 0], "yaw": 0.6, "pitch": 0.25, "distance": 100})
@@ -88,32 +135,38 @@ impl Drop for Scratch {
 /// not the home view the option used to be ignored for.
 #[test]
 fn a_camera_frames_the_picture_as_the_mcp_screenshot_does() {
+    if !gpu() {
+        return;
+    }
     let dir = Scratch::new();
     let script = dir.script("part.json", &[]);
     let home = dir.snapshot(&script, "home.png", &[]);
     let json = camera().to_string();
     let shot = dir.snapshot(&script, "camera.png", &["--camera", &json]);
-    assert_ne!(shot, home, "--camera was ignored");
-    assert_eq!(shot, dir.mcp(&script, "mcp-camera.png", json!({"camera": camera()})));
+    assert_differs(&shot, &home, "--camera was ignored");
+    assert_same(&shot, &dir.mcp(&script, "mcp-camera.png", json!({"camera": camera()})), "the MCP screenshot");
     // A perspective camera too, and a different eye gives a different picture.
     let mut near = camera();
     near["fov"] = json!(0.6);
     let perspective = dir.snapshot(&script, "perspective.png", &["--camera", &near.to_string()]);
-    assert_ne!(perspective, shot);
-    assert_eq!(perspective, dir.mcp(&script, "mcp-perspective.png", json!({"camera": near})));
+    assert_differs(&perspective, &shot, "perspective");
+    assert_same(&perspective, &dir.mcp(&script, "mcp-perspective.png", json!({"camera": near})), "the MCP perspective screenshot");
 }
 
 /// `--view` also takes a view saved in the design, which is the camera it was saved with; a
 /// standard view still looks as it did.
 #[test]
 fn a_saved_view_is_its_camera_and_a_standard_view_is_unchanged() {
+    if !gpu() {
+        return;
+    }
     let dir = Scratch::new();
     let script = dir.script("part.json", &[]);
     let json = camera().to_string();
     let by_camera = dir.snapshot(&script, "camera.png", &["--camera", &json]);
     let saved = dir.snapshot(&script, "saved.png", &["--view", "Detail"]);
-    assert_eq!(saved, by_camera);
-    assert_eq!(saved, dir.mcp(&script, "mcp-saved.png", json!({"view": "Detail"})));
+    assert_same(&saved, &by_camera, "the saved view");
+    assert_same(&saved, &dir.mcp(&script, "mcp-saved.png", json!({"view": "Detail"})), "the MCP saved view");
     // A standard view frames the model from its direction, as before: the home camera turned.
     let top = dir.snapshot(&script, "top.png", &["--view", "top"]);
     let mut s = Session::default();
@@ -121,32 +174,38 @@ fn a_saved_view_is_its_camera_and_a_standard_view_is_unchanged() {
     let mut cam = solidcraft_engine::view::home_camera(&s);
     cam.set_view(solidcraft_engine::render::StandardView::Top);
     let scene = solidcraft_engine::view::scene(&s, &cam);
-    assert_eq!(top, solidcraft_engine::render::render_png(&scene, &cam, SIZE.0, SIZE.1).unwrap());
-    assert_eq!(top, dir.mcp(&script, "mcp-top.png", json!({"view": "top"})));
-    assert_ne!(top, saved);
+    assert_same(&top, &solidcraft_engine::capture::png(&scene, &cam, SIZE.0, SIZE.1).unwrap().bytes, "the home camera turned to the top");
+    assert_same(&top, &dir.mcp(&script, "mcp-top.png", json!({"view": "top"})), "the MCP top view");
+    assert_differs(&top, &saved, "top and the saved view");
     let iso = dir.snapshot(&script, "iso.png", &["--view", "iso"]);
-    assert_eq!(iso, dir.snapshot(&script, "home.png", &[]));
-    assert_ne!(iso, top);
+    assert_same(&iso, &dir.snapshot(&script, "home.png", &[]), "iso is home");
+    assert_differs(&iso, &top, "iso and top");
 }
 
 /// A script that applies a view itself (as an MCP `execute` of `view.apply` does) sets the camera
 /// of its snapshot; `--view` and `--camera` still decide when given.
 #[test]
 fn a_script_can_carry_its_camera() {
+    if !gpu() {
+        return;
+    }
     let dir = Scratch::new();
     let script = dir.script("carried.json", &[json!({"command": "view.apply", "params": {"camera": camera()}})]);
     let plain = dir.script("plain.json", &[]);
     let carried = dir.snapshot(&script, "carried.png", &[]);
-    assert_eq!(carried, dir.snapshot(&plain, "by-camera.png", &["--camera", &camera().to_string()]));
-    assert_ne!(carried, dir.snapshot(&plain, "home.png", &[]));
+    assert_same(&carried, &dir.snapshot(&plain, "by-camera.png", &["--camera", &camera().to_string()]), "the carried camera");
+    assert_differs(&carried, &dir.snapshot(&plain, "home.png", &[]), "the carried camera and home");
     let top = dir.snapshot(&script, "top.png", &["--view", "top"]);
-    assert_eq!(top, dir.snapshot(&plain, "plain-top.png", &["--view", "top"]));
+    assert_same(&top, &dir.snapshot(&plain, "plain-top.png", &["--view", "top"]), "--view decides");
 }
 
 /// The grid and the axes each go when asked, and a render without both from any side shows the
 /// model alone: an empty design is then the same blank picture from every camera.
 #[test]
 fn the_grid_and_the_axes_can_be_left_out() {
+    if !gpu() {
+        return;
+    }
     let dir = Scratch::new();
     let script = dir.script("part.json", &[]);
     let json = camera().to_string();
@@ -161,7 +220,7 @@ fn the_grid_and_the_axes_can_be_left_out() {
         let different = [&all, &no_grid, &no_axes, &bare];
         for (i, a) in different.iter().enumerate() {
             for b in &different[i + 1..] {
-                assert_ne!(a, b, "{view:?}: two pictures are the same");
+                assert_differs(a, b, &format!("{view:?}: two of the pictures"));
             }
         }
         // The same as the MCP's `grid` and `axes`.
@@ -173,15 +232,151 @@ fn the_grid_and_the_axes_can_be_left_out() {
             a.as_object_mut().unwrap().extend(extra.as_object().unwrap().clone());
             dir.mcp(&script, out, a)
         };
-        assert_eq!(no_grid, mcp(json!({"grid": false}), "mcp-no-grid.png"));
-        assert_eq!(no_axes, mcp(json!({"axes": false}), "mcp-no-axes.png"));
-        assert_eq!(bare, mcp(json!({"grid": false, "axes": false}), "mcp-bare.png"));
+        assert_same(&no_grid, &mcp(json!({"grid": false}), "mcp-no-grid.png"), "the MCP's grid: false");
+        assert_same(&no_axes, &mcp(json!({"axes": false}), "mcp-no-axes.png"), "the MCP's axes: false");
+        assert_same(&bare, &mcp(json!({"grid": false, "axes": false}), "mcp-bare.png"), "the MCP's bare picture");
     }
     let empty = dir.0.join("empty.json");
     std::fs::write(&empty, json!({"commands": []}).to_string()).unwrap();
     let blank = |view: &str, out: &str| dir.snapshot(&empty, out, &["--view", view, "--no-grid", "--no-axes"]);
-    assert_eq!(blank("top", "blank-top.png"), blank("front", "blank-front.png"));
-    assert_ne!(blank("top", "blank-top.png"), dir.snapshot(&empty, "top.png", &["--view", "top"]));
+    assert_same(&blank("top", "blank-top.png"), &blank("front", "blank-front.png"), "blank from every side");
+    assert_differs(&blank("top", "blank-top.png"), &dir.snapshot(&empty, "top.png", &["--view", "top"]), "blank and the grid");
+}
+
+/// A snapshot of a box shows its silhouette where the camera puts it: the pixels that differ
+/// from an empty design's picture (same camera, no grid or axes) span the box's corners projected
+/// to pixels, within the edge and silhouette lines' width.
+#[test]
+fn a_snapshot_shows_the_part_where_the_camera_puts_it() {
+    if !gpu() {
+        return;
+    }
+    let dir = Scratch::new();
+    let part = dir.0.join("box.json");
+    let empty = dir.0.join("empty.json");
+    let corner = [10.0, -20.0, -15.0];
+    let size = [60.0, 40.0, 30.0];
+    std::fs::write(
+        &part,
+        json!({"commands": [{"command": "solid.box", "params": {"length": size[0], "width": size[1], "height": size[2], "corner": corner}}]})
+            .to_string(),
+    )
+    .unwrap();
+    std::fs::write(&empty, json!({"commands": []}).to_string()).unwrap();
+    for cam in [
+        camera(),
+        json!({"target": [40, 0, 0], "yaw": 0.0, "pitch": 0.0, "distance": 160}),
+        json!({"target": [40, 0, 0], "yaw": -0.4, "pitch": 0.5, "distance": 150, "fov": 0.6}),
+    ] {
+        let args = ["--camera", &cam.to_string(), "--no-grid", "--no-axes"];
+        let (_, _, with) = decode(&dir.snapshot(&part, "part.png", &args));
+        let (_, _, without) = decode(&dir.snapshot(&empty, "empty.png", &args));
+        // The part's pixels: where the picture differs from the empty one.
+        let (mut lo, mut hi) = ([u32::MAX; 2], [0u32; 2]);
+        for (i, (p, q)) in with.as_chunks::<4>().0.iter().zip(without.as_chunks::<4>().0).enumerate() {
+            if p.iter().zip(q.iter()).any(|(x, y)| x.abs_diff(*y) > 24) {
+                let (x, y) = (i as u32 % SIZE.0, i as u32 / SIZE.0);
+                lo = [lo[0].min(x), lo[1].min(y)];
+                hi = [hi[0].max(x), hi[1].max(y)];
+            }
+        }
+        assert!(lo[0] <= hi[0], "{cam}: the part is not in the picture");
+        // Where the camera puts the corners.
+        let mut s = solidcraft_engine::Session::default();
+        s.execute("view.apply", &json!({"camera": cam})).unwrap();
+        let c = s.camera.unwrap();
+        let vp = c.view_proj(f64::from(SIZE.0) / f64::from(SIZE.1), 1000.0);
+        let (mut elo, mut ehi) = ([f64::MAX; 2], [f64::MIN; 2]);
+        for k in 0..8 {
+            let p = solidcraft_engine::geom::Vec3::new(
+                corner[0] + size[0] * f64::from(k & 1),
+                corner[1] + size[1] * f64::from((k >> 1) & 1),
+                corner[2] + size[2] * f64::from((k >> 2) & 1),
+            );
+            let q = vp.apply(p);
+            let (x, y) = ((q[0] / q[3] + 1.0) * 0.5 * f64::from(SIZE.0), (1.0 - q[1] / q[3]) * 0.5 * f64::from(SIZE.1));
+            elo = [elo[0].min(x), elo[1].min(y)];
+            ehi = [ehi[0].max(x), ehi[1].max(y)];
+        }
+        let near = |got: u32, want: f64| (f64::from(got) - want).abs() <= 2.5;
+        assert!(
+            near(lo[0], elo[0]) && near(lo[1], elo[1]) && near(hi[0] + 1, ehi[0]) && near(hi[1] + 1, ehi[1]),
+            "{cam}: the part spans pixels {lo:?}..={hi:?}, its corners project to {elo:?}..{ehi:?}"
+        );
+    }
+}
+
+/// `snapshot` under a `SOLIDCRAFT_GPU` policy: its reply and stderr.
+fn snapshot_under(dir: &Scratch, script: &Path, out: &str, policy: &str) -> Output {
+    Command::new(env!("CARGO_BIN_EXE_solidcraft-cli"))
+        .env("SOLIDCRAFT_GPU", policy)
+        .arg("snapshot")
+        .arg(script)
+        .arg("--out")
+        .arg(dir.0.join(out))
+        .args(["--width", &SIZE.0.to_string(), "--height", &SIZE.1.to_string(), "--view", "top"])
+        .output()
+        .unwrap()
+}
+
+/// The last tier: `SOLIDCRAFT_GPU=cpu` draws with the CPU rasterizer whatever adapters there are,
+/// says so (`renderer: cpu` and a warning that overlays are not drawn), and the picture is the
+/// rasterizer's own.
+#[test]
+fn a_forced_cpu_snapshot_is_the_cpu_rasterizers_and_says_so() {
+    let dir = Scratch::new();
+    let script = dir.script("part.json", &[]);
+    let output = snapshot_under(&dir, &script, "cpu.png", "cpu");
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(output.status.success(), "{stderr}");
+    let reply: Value = serde_json::from_slice(&output.stdout).unwrap();
+    assert_eq!(reply["renderer"], "cpu", "{reply}");
+    assert!(reply["warning"].as_str().is_some_and(|w| w.contains("not drawn")), "{reply}");
+    assert!(stderr.contains("CPU rasterizer"), "{stderr}");
+    let mut s = Session::default();
+    s.run_script(&serde_json::from_slice(&std::fs::read(&script).unwrap()).unwrap()).unwrap();
+    let mut cam = solidcraft_engine::view::home_camera(&s);
+    cam.set_view(solidcraft_engine::render::StandardView::Top);
+    let scene = solidcraft_engine::view::scene(&s, &cam);
+    let cpu = solidcraft_engine::render::render_png(&scene, &cam, SIZE.0 as usize, SIZE.1 as usize).unwrap();
+    assert_eq!(std::fs::read(dir.0.join("cpu.png")).unwrap(), cpu);
+}
+
+/// `hardware` (and `software`) never fall to the CPU rasterizer: without such an adapter the
+/// snapshot fails, naming the policy, and writes nothing; with one it says it was drawn on the GPU.
+/// `auto` lands where `solidcraft-cli gpu` says it does.
+#[test]
+fn a_strict_policy_never_falls_to_the_cpu() {
+    let dir = Scratch::new();
+    let script = dir.script("part.json", &[]);
+    let survey = |policy: &str| {
+        let o = Command::new(env!("CARGO_BIN_EXE_solidcraft-cli")).args(["gpu", "--policy", policy]).output().unwrap();
+        (o.status.success(), serde_json::from_slice::<Value>(&o.stdout).unwrap_or(Value::Null))
+    };
+    for policy in ["hardware", "software"] {
+        let (found, report) = survey(policy);
+        let output = snapshot_under(&dir, &script, &format!("{policy}.png"), policy);
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        if found {
+            assert!(output.status.success(), "{policy}: {stderr}");
+            let reply: Value = serde_json::from_slice(&output.stdout).unwrap();
+            assert_eq!(reply["renderer"], report["renderer"], "{policy}: {reply}");
+            assert_ne!(reply["renderer"], "cpu");
+        } else {
+            assert_eq!(report["lands_on"], Value::Null, "{policy}: {report}");
+            assert_eq!(output.status.code(), Some(1), "{policy}: {stderr}");
+            assert!(stderr.contains(&format!("`{policy}` policy")) && stderr.contains("solidcraft-cli gpu"), "{policy}: {stderr}");
+            assert!(!dir.0.join(format!("{policy}.png")).exists());
+        }
+    }
+    let (found, report) = survey("auto");
+    assert!(found, "auto always lands somewhere: {report}");
+    let output = snapshot_under(&dir, &script, "auto.png", "auto");
+    assert!(output.status.success(), "{}", String::from_utf8_lossy(&output.stderr));
+    let reply: Value = serde_json::from_slice(&output.stdout).unwrap();
+    assert_eq!(reply["renderer"], report["renderer"], "{reply} vs {report}");
+    let (_, cpu) = survey("cpu");
+    assert_eq!((cpu["lands_on"].clone(), cpu["renderer"].clone()), (json!("cpu"), json!("cpu")), "{cpu}");
 }
 
 #[test]

apps/solidcraft-web/Cargo.toml

@@ -29,5 +29,5 @@ web-sys = { version = "0.3", features = [
     "Window", "Document", "Element", "HtmlElement", "HtmlCanvasElement", "Location", "Navigator", "StorageManager",
     "FileSystemHandle", "FileSystemDirectoryHandle", "FileSystemFileHandle", "FileSystemGetFileOptions", "FileSystemWritableFileStream",
     "WritableStream", "File", "FileList", "Blob", "BlobPropertyBag", "Url", "HtmlAnchorElement", "HtmlInputElement", "Storage",
-    "BeforeUnloadEvent", "Event", "EventTarget", "Response",
+    "BeforeUnloadEvent", "Event", "EventTarget", "Response", "MediaQueryList", "Gamepad",
 ] }

apps/solidcraft-web/index.html

@@ -23,6 +23,15 @@
   <link data-trunk rel="copy-file" href="../../assets/fonts/biz-udp-gothic/BIZUDPGothic-Regular.ttf" data-target-path="fonts" />
   <link data-trunk rel="copy-file" href="../../assets/fonts/biz-udp-gothic/OFL.txt" data-target-path="fonts" />
   <link data-trunk rel="css" href="../../assets/styles/web/loading.css" />
+  <!-- Installable as an app (manifest.webmanifest); the icons are the Linux exports of the app mark. -->
+  <meta name="theme-color" content="#343840">
+  <link rel="manifest" href="manifest.webmanifest">
+  <link rel="icon" type="image/png" sizes="32x32" href="icons/32x32/ai.storyteller.solidcraft.png">
+  <link rel="apple-touch-icon" href="icons/256x256/ai.storyteller.solidcraft.png">
+  <link data-trunk rel="copy-file" href="manifest.webmanifest" />
+  <link data-trunk rel="copy-file" href="../../assets/icons/app/linux/exports/hicolor/32x32/apps/ai.storyteller.solidcraft.png" data-target-path="icons/32x32" />
+  <link data-trunk rel="copy-file" href="../../assets/icons/app/linux/exports/hicolor/256x256/apps/ai.storyteller.solidcraft.png" data-target-path="icons/256x256" />
+  <link data-trunk rel="copy-file" href="../../assets/icons/app/linux/exports/hicolor/512x512/apps/ai.storyteller.solidcraft.png" data-target-path="icons/512x512" />
 </head>
 <body>
   <canvas id="solidcraft_canvas"></canvas>
@@ -32,6 +41,10 @@
     if ("serviceWorker" in navigator) {
       addEventListener("load", () => navigator.serviceWorker.register("sw.js").catch(() => {}));
     }
+    // Install as an app: the browser's offer can come before the app runs, so it is kept here for
+    // the app's File ▸ Install app… item (src/install.rs). Installed, the browser makes no more offers.
+    addEventListener("beforeinstallprompt", (e) => { e.preventDefault(); window.solidcraftInstall = e; });
+    addEventListener("appinstalled", () => { window.solidcraftInstall = null; });
   </script>
 </body>
 </html>

apps/solidcraft-web/manifest.webmanifest

@@ -0,0 +1,16 @@
+{
+  "name": "SolidCraft",
+  "short_name": "SolidCraft",
+  "description": "Open-source parametric CAD built in Rust.",
+  "start_url": "./",
+  "scope": "./",
+  "display": "standalone",
+  "background_color": "#e8ebf0",
+  "theme_color": "#343840",
+  "categories": ["productivity", "utilities"],
+  "icons": [
+    { "src": "icons/32x32/ai.storyteller.solidcraft.png", "sizes": "32x32", "type": "image/png" },
+    { "src": "icons/256x256/ai.storyteller.solidcraft.png", "sizes": "256x256", "type": "image/png" },
+    { "src": "icons/512x512/ai.storyteller.solidcraft.png", "sizes": "512x512", "type": "image/png" }
+  ]
+}

apps/solidcraft-web/src/files.rs

@@ -458,7 +458,7 @@ fn input_picker(files: &Rc<Files>, intent: Intent) {
     let Some(doc) = web_sys::window().and_then(|w| w.document()) else { return };
     let Ok(input) = doc.create_element("input").map(|e| e.unchecked_into::<web_sys::HtmlInputElement>()) else { return };
     input.set_type("file");
-    input.set_accept(".solidcraft,.solvecraft,.json,.step,.stp,.3mf,.stl");
+    input.set_accept(".solidcraft,.solvecraft,.json,.step,.stp,.3mf,.stl,.obj,.glb,.gltf");
     // Attached (hidden) while it is open: some browsers ignore a click on a detached input.
     let _ = input.set_attribute("style", "display:none");
     if let Some(body) = doc.body() {

apps/solidcraft-web/src/install.rs

@@ -0,0 +1,67 @@
+//! Install as an app (`solidcraft_ui_egui::install`). The browser offers it with a
+//! `beforeinstallprompt` event, which can come before this code runs: index.html keeps the event
+//! as `window.solidcraftInstall` (and drops it once the app is installed). The offer is good for
+//! one prompt; a browser that is still willing makes a new one later. Safari makes no offer: it
+//! gets its steps, unless the app is already running installed.
+
+use solidcraft_ui_egui::install::{InstallApp, Offer, safari_steps};
+use wasm_bindgen::{JsCast as _, JsValue};
+
+/// Where index.html keeps the browser's offer.
+const OFFER: &str = "solidcraftInstall";
+
+/// The browser's offer, kept by index.html (None: none, or it was used).
+fn offer() -> Option<js_sys::Object> {
+    let window = web_sys::window()?;
+    js_sys::Reflect::get(&window, &OFFER.into()).ok()?.dyn_into().ok()
+}
+
+/// Show the browser's install prompt (from the File menu click, so the page may).
+fn prompt() {
+    let Some(offer) = offer() else { return };
+    if let Some(window) = web_sys::window() {
+        let _ = js_sys::Reflect::set(&window, &OFFER.into(), &JsValue::NULL);
+    }
+    let shown = js_sys::Reflect::get(&offer, &"prompt".into())
+        .and_then(|f| f.dyn_into::<js_sys::Function>().map_err(JsValue::from))
+        .and_then(|f| f.call0(&offer))
+        .and_then(|p| p.dyn_into::<js_sys::Promise>().map_err(JsValue::from));
+    match shown {
+        // Accepted or dismissed, the browser handles it; a refusal is only logged.
+        Ok(p) => wasm_bindgen_futures::spawn_local(async move {
+            if let Err(e) = wasm_bindgen_futures::JsFuture::from(p).await {
+                log::warn!("install prompt: {e:?}");
+            }
+        }),
+        Err(e) => log::warn!("install prompt: {e:?}"),
+    }
+}
+
+/// The page runs as the installed app (its own window, or from the Home Screen on iOS).
+fn running_installed(window: &web_sys::Window) -> bool {
+    let standalone = window.match_media("(display-mode: standalone)").ok().flatten().is_some_and(|m| m.matches());
+    let home_screen = js_sys::Reflect::get(&window.navigator(), &"standalone".into()).ok().and_then(|v| v.as_bool()).unwrap_or(false);
+    standalone || home_screen
+}
+
+/// The host service for File ▸ Install app…; the UI is drawn again whenever the browser
+/// makes or withdraws its offer (even with nothing else happening).
+pub fn service(ctx: &egui::Context) -> InstallApp {
+    // Safari's steps, decided once: the browser and the way the page runs don't change.
+    let steps = web_sys::window().filter(|w| !running_installed(w)).and_then(|w| {
+        let nav = w.navigator();
+        let vendor = js_sys::Reflect::get(&nav, &"vendor".into()).ok().and_then(|v| v.as_string()).unwrap_or_default();
+        safari_steps(&nav.user_agent().unwrap_or_default(), &vendor, nav.max_touch_points())
+    });
+    if let Some(window) = web_sys::window() {
+        for event in ["beforeinstallprompt", "appinstalled"] {
+            let ctx = ctx.clone();
+            let redraw = wasm_bindgen::closure::Closure::<dyn FnMut()>::new(move || ctx.request_repaint());
+            let _ = window.add_event_listener_with_callback(event, redraw.as_ref().unchecked_ref());
+            // The listener lives as long as the page.
+            redraw.forget();
+        }
+    }
+    let offered = move || if offer().is_some() { Some(Offer::Prompt) } else { steps.map(Offer::Steps) };
+    InstallApp { offer: Box::new(offered), prompt: Box::new(prompt) }
+}

apps/solidcraft-web/src/main.rs

@@ -2,12 +2,16 @@
 //!
 //! Runs the same [`solidcraft_ui_egui::SolveApp`] as the desktop app through eframe's web runner
 //! (wgpu: WebGPU where available, WebGL2 otherwise). Build with `trunk build --release` from this
-//! directory (output in `dist/web`). URL flags: `?webgl` forces WebGL2, `?sample` opens the
-//! sample part.
+//! directory (output in `dist/web`). URL flags: `?webgl` forces WebGL2 (remembered until
+//! `?webgpu`), `?sample` opens the sample part.
 #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
 
 #[cfg(target_arch = "wasm32")]
 mod files;
+#[cfg(target_arch = "wasm32")]
+mod install;
+#[cfg(any(target_arch = "wasm32", test))]
+mod space_mouse;
 
 #[cfg(target_arch = "wasm32")]
 mod web {
@@ -19,6 +23,7 @@ mod web {
     use wasm_bindgen::JsCast as _;
 
     use crate::files::{self, Files, Intent};
+    use crate::space_mouse::SpaceMouse;
 
     const CANVAS_ID: &str = "solidcraft_canvas";
     const LOADING_ID: &str = "solidcraft_loading";
@@ -65,6 +70,7 @@ mod web {
         /// On-demand CJK font: fetched only when a CJK language is selected.
         font: solidcraft_ui_egui::fonts::CjkFontLoader,
         font_result: FontLoadResult,
+        space_mouse: SpaceMouse,
     }
 
     impl Shell {
@@ -83,7 +89,16 @@ mod web {
             for (text, error) in self.files.messages.borrow_mut().drain(..) {
                 self.app.set_status(text, error);
             }
-            let incoming: Vec<_> = self.files.incoming.borrow_mut().drain(..).collect();
+            let mut incoming: Vec<_> = self.files.incoming.borrow_mut().drain(..).collect();
+            // A glTF file's buffers picked with it are kept next to it, not opened.
+            incoming.retain_mut(|(name, bytes, _)| {
+                let companion =
+                    std::path::Path::new(name.as_str()).extension().and_then(|e| e.to_str()).is_some_and(|e| e.eq_ignore_ascii_case("bin"));
+                if companion {
+                    vfs::insert(&format!("{}{name}", files::UPLOAD), std::mem::take(bytes));
+                }
+                !companion
+            });
             for (name, bytes, intent) in incoming {
                 let design = solidcraft_engine::io::is_design_path(&name);
                 let path = if design && intent == Intent::Open {
@@ -371,11 +386,14 @@ mod web {
         fn logic(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
             self.tick_font(ctx);
             self.app.logic(ctx);
+            self.space_mouse.logic(&mut self.app, ctx);
             self.files_tick(ctx);
             UNSAVED.with(|u| u.set(solidcraft_ui_egui::documents::any_dirty(&self.app)));
         }
-        fn raw_input_hook(&mut self, _ctx: &egui::Context, raw: &mut egui::RawInput) {
+        fn raw_input_hook(&mut self, ctx: &egui::Context, raw: &mut egui::RawInput) {
             files::take_drops(&self.files, raw);
+            // Before the app's own hook, which adds the control channel's events.
+            self.space_mouse.raw_input_hook(ctx, self.app.preferences.space_mouse_enabled, raw);
             self.app.raw_input_hook(raw);
         }
         fn ui(&mut self, ui: &mut egui::Ui, _frame: &mut eframe::Frame) {
@@ -398,6 +416,29 @@ mod web {
         web_sys::window().and_then(|w| w.location().search().ok()).unwrap_or_default()
     }
 
+    /// Where `?webgl` is remembered. The installed app starts from its manifest's start URL, which
+    /// has no query, so the choice has to outlive the page it was made on.
+    const WEBGL_KEY: &str = "solidcraft.webgl";
+
+    /// Render with WebGL2: asked for now (`?webgl`, remembered) or before (until `?webgpu`).
+    fn webgl() -> bool {
+        let storage = web_sys::window().and_then(|w| w.local_storage().ok().flatten());
+        let q = query();
+        if q.contains("webgl") {
+            if let Some(s) = &storage {
+                let _ = s.set_item(WEBGL_KEY, "1");
+            }
+            return true;
+        }
+        if q.contains("webgpu") {
+            if let Some(s) = &storage {
+                let _ = s.remove_item(WEBGL_KEY);
+            }
+            return false;
+        }
+        storage.and_then(|s| s.get_item(WEBGL_KEY).ok().flatten()).is_some()
+    }
+
     /// Fetch font bytes asynchronously through the browser.
     async fn fetch_font_bytes(url: &str) -> Result<Vec<u8>, String> {
         let window = web_sys::window().ok_or("no window")?;
@@ -422,7 +463,7 @@ mod web {
                 return;
             };
             let mut options = eframe::WebOptions { depth_buffer: DEPTH_BITS, ..Default::default() };
-            if query().contains("webgl")
+            if webgl()
                 && let eframe::egui_wgpu::WgpuSetup::CreateNew(create) = &mut options.wgpu_options.wgpu_setup
             {
                 create.instance_descriptor.backends = eframe::wgpu::Backends::GL;
@@ -447,8 +488,11 @@ mod web {
                                 let design = exts.contains(&solidcraft_engine::io::DESIGN_EXT);
                                 Box::pin(std::future::ready(Some(format!("{}{name}", if design { files::OPFS } else { files::DOWNLOADS }))))
                             })),
+                            install_app: Some(crate::install::service(&cc.egui_ctx)),
                             ..Default::default()
                         };
+                        // Thumbnails of saves and start-page cards.
+                        solidcraft_ui_egui::gpu::install_cpu_picture_renderer();
                         let mut app = SolveApp::new(Session::default(), services);
                         if let Some(p) = cc.storage.and_then(|s| solidcraft_ui_egui::prefs::stored(|k| s.get_string(k))) {
                             app.load_prefs(&p);
@@ -481,6 +525,7 @@ mod web {
                             recents_synced: false,
                             font: Default::default(),
                             font_result: Rc::new(std::cell::RefCell::new(None)),
+                            space_mouse: SpaceMouse::default(),
                         }))
                     }),
                 )

apps/solidcraft-web/src/space_mouse.rs

@@ -0,0 +1,285 @@
+//! The 3D mouse in the browser (#1336), through the Gamepad API.
+//!
+//! Chromium browsers list a 3Dconnexion device itself, with its six axes scaled to -1..1 from the
+//! device's ±350. Firefox lists only joysticks and gamepads (a 3D mouse is a HID multi-axis
+//! controller), but 3DxWare's virtual joystick carries the same six axes once 3DxWare's profile
+//! for Firefox sends them there. Both come in the device's own order and signs, so the shared
+//! navigation takes them with 3DxWare's object-mode mapping, as the Linux app does without a
+//! profile.
+
+use solidcraft_ui_egui::space_mouse::{Axes, FULL_SCALE};
+
+/// Logitech's vendor id, which older 3Dconnexion devices carry, and those devices' product ids
+/// (usb.ids). Logitech's own gamepads and wheels carry the same vendor id.
+const LOGITECH: u16 = 0x046d;
+const LOGITECH_3D_MICE: [u16; 11] = [0xc603, 0xc605, 0xc606, 0xc621, 0xc623, 0xc625, 0xc626, 0xc627, 0xc628, 0xc629, 0xc62b];
+/// 3Dconnexion's own vendor id. The browser lists only its 3D mice as gamepads: its mice, and the
+/// mouse side of its receivers, are not gamepads.
+const THREEDCONNEXION: u16 = 0x256f;
+/// 3DxWare's virtual joystick.
+const VIRTUAL_JOYSTICK: (u16, u16) = (0xbeef, 0x046d);
+
+/// What a gamepad the browser lists is, when it is a 3D mouse. A device is read before the
+/// joystick: in a Chromium browser both are listed, and the joystick stays at rest.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub enum Source {
+    Device,
+    VirtualJoystick,
+}
+
+/// The vendor and product ids in a gamepad's id: `Name (Vendor: 046d Product: c62b)` in Chromium
+/// browsers, `046d-c62b-Name` in Firefox.
+fn vendor_product(id: &str) -> Option<(u16, u16)> {
+    fn hex(digits: &str) -> Option<u16> {
+        if (1..=4).contains(&digits.len()) && digits.bytes().all(|b| b.is_ascii_hexdigit()) { u16::from_str_radix(digits, 16).ok() } else { None }
+    }
+    if let Some((_, ids)) = id.rsplit_once("Vendor: ") {
+        let (vendor, rest) = ids.split_once(" Product: ")?;
+        let product = rest.split(|c: char| !c.is_ascii_hexdigit()).next()?;
+        return Some((hex(vendor)?, hex(product)?));
+    }
+    let mut parts = id.splitn(3, '-');
+    let (vendor, product, _name) = (parts.next()?, parts.next()?, parts.next()?);
+    Some((hex(vendor)?, hex(product)?))
+}
+
+/// Whether a gamepad is a 3D mouse, from the id the browser gives it.
+pub fn source(id: &str) -> Option<Source> {
+    match vendor_product(id)? {
+        VIRTUAL_JOYSTICK => Some(Source::VirtualJoystick),
+        (THREEDCONNEXION, _) => Some(Source::Device),
+        (LOGITECH, product) if LOGITECH_3D_MICE.contains(&product) => Some(Source::Device),
+        _ => None,
+    }
+}
+
+/// The six axes in the device's raw units, from a gamepad's axes (-1..1). Fewer than six: not a
+/// 3D mouse. A value that isn't a number reads as rest.
+pub fn axes(values: &[f64]) -> Option<Axes> {
+    let raw = |i: usize| values.get(i).map(|&v| if v.is_finite() { (v.clamp(-1.0, 1.0) * f64::from(FULL_SCALE)).round() as i16 } else { 0 });
+    Some(Axes { translation: [raw(0)?, raw(1)?, raw(2)?], rotation: [raw(3)?, raw(4)?, raw(5)?] })
+}
+
+/// The 3D mouse to read among the ones listed: the first device, else the first joystick.
+pub fn choose(found: impl IntoIterator<Item = (Source, Axes)>) -> Option<Axes> {
+    found.into_iter().min_by_key(|(source, _)| *source).map(|(_, axes)| axes)
+}
+
+#[cfg(target_arch = "wasm32")]
+pub use browser::SpaceMouse;
+
+#[cfg(target_arch = "wasm32")]
+mod browser {
+    use std::cell::Cell;
+    use std::rc::Rc;
+
+    use solidcraft_ui_egui::SolveApp;
+    use solidcraft_ui_egui::space_mouse::{Axes, DriverMapping, navigate_frame};
+    use wasm_bindgen::JsCast as _;
+    use wasm_bindgen::closure::Closure;
+
+    use solidcraft_ui_egui::space_mouse::WheelGuard;
+
+    use super::{axes, choose, source};
+
+    /// How often the page looks for the cap starting to move while nothing else redraws.
+    const WAKE_MS: i32 = 50;
+
+    /// The 3D mouse the browser lists, if any.
+    fn read() -> Option<Axes> {
+        let pads = web_sys::window()?.navigator().get_gamepads().ok()?;
+        choose(pads.iter().filter_map(|pad| {
+            let pad = pad.dyn_into::<web_sys::Gamepad>().ok().filter(web_sys::Gamepad::connected)?;
+            let source = source(&pad.id())?;
+            let values: Vec<f64> = pad.axes().iter().map(|v| v.as_f64().unwrap_or(f64::NAN)).collect();
+            Some((source, axes(&values)?))
+        }))
+    }
+
+    /// Reads the 3D mouse once per frame and moves the view with it.
+    #[derive(Default)]
+    pub struct SpaceMouse {
+        axes: Axes,
+        /// The previous frame's time and the step since it (seconds).
+        last: Option<f64>,
+        seconds: f64,
+        wheel: WheelGuard,
+        /// Listening for gamepads (from the first frame with navigation on).
+        listening: bool,
+        /// The timer that wakes the app when the cap starts moving runs (from when a 3D mouse
+        /// is first listed).
+        waking: bool,
+        /// Navigation is on (the waker reads it).
+        enabled: Rc<Cell<bool>>,
+    }
+
+    impl SpaceMouse {
+        /// At the start of a frame: reads the cap and drops 3DxWare's emulated wheel from the
+        /// frame's input, before the app sees it.
+        pub fn raw_input_hook(&mut self, ctx: &egui::Context, enabled: bool, raw: &mut egui::RawInput) {
+            let now = raw.time.unwrap_or_else(|| js_sys::Date::now() / 1000.0);
+            self.seconds = self.last.map_or(0.0, |last| now - last);
+            self.last = Some(now);
+            self.enabled.set(enabled);
+            self.axes = Axes::default();
+            if !enabled {
+                return;
+            }
+            if !self.listening {
+                self.listening = true;
+                listen(ctx);
+            }
+            let reading = read();
+            if reading.is_some() && !self.waking {
+                self.waking = wake(ctx, &self.enabled);
+            }
+            // Inside the dead zone is rest: a cap resting just off zero doesn't keep redrawing.
+            self.axes = reading.filter(|axes| axes.moving()).unwrap_or_default();
+            self.wheel.filter(self.axes.moving(), now, &mut raw.events);
+        }
+
+        pub fn logic(&self, app: &mut SolveApp, ctx: &egui::Context) {
+            navigate_frame(app, ctx, DriverMapping::object_mode(), self.axes, self.seconds);
+        }
+    }
+
+    /// A 3D mouse is listed only once it has been moved on the page: redraw then, so the frame
+    /// finds it without waiting for the pointer.
+    fn listen(ctx: &egui::Context) {
+        let Some(window) = web_sys::window() else { return };
+        let ctx = ctx.clone();
+        let on_connect = Closure::<dyn FnMut()>::new(move || ctx.request_repaint());
+        let _ = window.add_event_listener_with_callback("gamepadconnected", on_connect.as_ref().unchecked_ref());
+        // The listener lives as long as the page.
+        on_connect.forget();
+    }
+
+    /// The browser sends no event when a gamepad moves, so a timer looks while the app is idle and
+    /// redraws when the cap starts moving; the frames that follow keep going on their own.
+    fn wake(ctx: &egui::Context, enabled: &Rc<Cell<bool>>) -> bool {
+        let Some(window) = web_sys::window() else { return false };
+        let (ctx, enabled) = (ctx.clone(), Rc::clone(enabled));
+        let tick = Closure::<dyn FnMut()>::new(move || {
+            if enabled.get() && read().is_some_and(Axes::moving) {
+                ctx.request_repaint();
+            }
+        });
+        let started = window.set_interval_with_callback_and_timeout_and_arguments_0(tick.as_ref().unchecked_ref(), WAKE_MS).is_ok();
+        // The timer lives as long as the page.
+        tick.forget();
+        started
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn recognises_3d_mice_in_each_browsers_ids() {
+        // As Edge and Firefox list them (Windows 11, SpaceMouse Pro, 3DxWare 10).
+        assert_eq!(source("SpaceMouse Pro (Vendor: 046d Product: c62b)"), Some(Source::Device));
+        assert_eq!(source("Unknown Gamepad (Vendor: beef Product: 046d)"), Some(Source::VirtualJoystick));
+        assert_eq!(source("beef-046d-Unknown Gamepad"), Some(Source::VirtualJoystick));
+        // 3Dconnexion's own vendor id, any product; the older devices under Logitech's.
+        assert_eq!(source("SpaceMouse Compact (Vendor: 256f Product: c635)"), Some(Source::Device));
+        assert_eq!(source("256f-c652-3Dconnexion Universal Receiver"), Some(Source::Device));
+        assert_eq!(source("46d-c626-SpaceNavigator"), Some(Source::Device));
+        assert_eq!(source("SpaceNavigator (STANDARD GAMEPAD Vendor: 046d Product: c626)"), Some(Source::Device));
+        for product in LOGITECH_3D_MICE {
+            assert_eq!(source(&format!("x (Vendor: 046d Product: {product:04x})")), Some(Source::Device));
+            assert_eq!(source(&format!("046d-{product:04X}-x")), Some(Source::Device));
+        }
+    }
+
+    #[test]
+    fn gamepads_and_other_logitech_devices_are_not_3d_mice() {
+        for id in [
+            "Logitech Dual Action (STANDARD GAMEPAD Vendor: 046d Product: c216)",
+            "046d-c21d-Logitech Gamepad F310",
+            "G29 Driving Force Racing Wheel (Vendor: 046d Product: c24f)",
+            "046d-c215-Logitech Extreme 3D",
+            "NuLOOQ navigator (Vendor: 046d Product: c640)",
+            "Xbox 360 Controller (XInput STANDARD GAMEPAD)",
+            "45e-28e-Xbox 360 Wired Controller",
+            "beef-046e-Unknown Gamepad",
+            "beee-046d-Unknown Gamepad",
+            "",
+            "-",
+            "--",
+            "256f-",
+            "256f-c635",
+            "Vendor: 256f",
+            "Vendor: 256f Product: ",
+            "x (Vendor: 256fff Product: c635)",
+            "x (Vendor: zz6f Product: c635)",
+            "12345-c635-x",
+            "256f--x",
+            "SpaceMouse Pro",
+        ] {
+            assert_eq!(source(id), None, "{id:?}");
+        }
+    }
+
+    #[test]
+    fn ids_never_panic() {
+        // Hostile and odd ids: multi-byte text around the markers, markers repeated or cut short.
+        for id in [
+            "Vendor: é Product: ü",
+            "Vendor: Vendor: 256f Product: c635)",
+            "é-ü-ö",
+            "Ⅰ (Vendor: 256f Product: c6Ⅰ)",
+            "\u{0}-\u{0}-\u{0}",
+            "Vendor: 256f Product: c635 Vendor: ",
+        ] {
+            let _ = source(id);
+        }
+        let mut seed = 0x2545_f491_4f6c_dd1d_u64;
+        let alphabet: Vec<char> = "0123456789abcdefABCDEF- ():VendorProductéⅠ\u{0}".chars().collect();
+        for _ in 0..20_000 {
+            let len = (seed % 40) as usize;
+            let id: String = (0..len)
+                .map(|_| {
+                    seed ^= seed << 13;
+                    seed ^= seed >> 7;
+                    seed ^= seed << 17;
+                    alphabet[(seed % alphabet.len() as u64) as usize]
+                })
+                .collect();
+            if let Some(Source::Device) = source(&id) {
+                let (vendor, product) = vendor_product(&id).expect("recognised ids have both");
+                assert!(vendor == THREEDCONNEXION || (vendor == LOGITECH && LOGITECH_3D_MICE.contains(&product)), "{id:?}");
+            }
+        }
+    }
+
+    #[test]
+    fn gamepad_axes_are_the_devices_raw_units() {
+        // Full deflection is the desktop's 350, and the browser's scale keeps the device's steps.
+        let axes = axes(&[1.0, -1.0, 0.5, -0.5, 2.0 / 700.0, 0.0]).expect("six axes");
+        assert_eq!(axes, Axes { translation: [350, -350, 175], rotation: [-175, 1, 0] });
+        for raw in -350_i16..=350 {
+            let value = f64::from(raw) / 350.0;
+            assert_eq!(super::axes(&[value; 6]).map(|a| a.translation[0]), Some(raw));
+        }
+        // Past full deflection is full deflection; anything that isn't a number is rest.
+        let hostile = super::axes(&[f64::NAN, f64::INFINITY, f64::NEG_INFINITY, 1e300, -1e300, f64::MIN_POSITIVE]).expect("six axes");
+        assert_eq!(hostile, Axes { translation: [0, 0, 0], rotation: [350, -350, 0] });
+        // A gamepad with fewer than six axes is not a 3D mouse; extra axes are ignored.
+        assert_eq!(super::axes(&[1.0; 5]), None);
+        assert_eq!(super::axes(&[]), None);
+        assert_eq!(super::axes(&[0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0]), Some(Axes::default()));
+    }
+
+    #[test]
+    fn a_device_is_read_before_the_virtual_joystick() {
+        let moving = Axes { translation: [100, 0, 0], rotation: [0; 3] };
+        let other = Axes { translation: [0, 200, 0], rotation: [0; 3] };
+        assert_eq!(choose([(Source::VirtualJoystick, other), (Source::Device, moving)]), Some(moving));
+        assert_eq!(choose([(Source::Device, moving), (Source::VirtualJoystick, other)]), Some(moving));
+        assert_eq!(choose([(Source::VirtualJoystick, other)]), Some(other));
+        // Two devices: the first listed.
+        assert_eq!(choose([(Source::Device, moving), (Source::Device, other)]), Some(moving));
+        assert_eq!(choose([]), None);
+    }
+}

apps/solidcraft/Cargo.toml

@@ -8,8 +8,8 @@ publish = false
 default-run = "solidcraft"
 
 # The workspace lints, except unsafe_code: denied, not forbidden, so that src/open_documents.rs
-# (macOS file-open events) and src/native_crash.rs (Windows exception filter) can allow it: neither
-# has a safe API. Keep the rest in sync with [workspace.lints].
+# (macOS file-open events), src/native_crash.rs (Windows exception filter) and src/native_frame.rs
+# (Windows resize border) can allow it: none has a safe API. Keep the rest in sync with [workspace.lints].
 [lints.rust]
 unsafe_code = "deny"
 
@@ -36,13 +36,19 @@ getrandom = "0.3"
 # The update check (docs/updates.md): HTTPS with rustls, certificates from the operating system.
 ureq = { version = "3.4", default-features = false, features = ["rustls-no-provider", "platform-verifier"] }
 rustls = { version = "0.23", default-features = false, features = ["ring", "std", "tls12", "logging"] }
+# API keys of the agent chat's API agents (docs/agent-chat.md) live in the system keychain:
+# Keychain on macOS, Credential Manager on Windows, the Secret Service (pure-Rust D-Bus) elsewhere.
+keyring = { version = "3.6", default-features = false, features = ["apple-native", "windows-native", "async-secret-service", "async-io", "crypto-rust"] }
 
 [target.'cfg(any(target_os = "windows", target_os = "linux"))'.dependencies]
 quick-xml = { workspace = true }
 
 [target.'cfg(target_os = "windows")'.dependencies]
 hidapi = { version = "2.6.7", default-features = false, features = ["windows-native"] }
+# The main window's handle for src/native_frame.rs (already in the tree through eframe and winit).
+raw-window-handle = "0.6"
 # Native crash capture (src/native_crash.rs): the exception filter, the faulting module, a minidump.
+# The window's resize border and DPI size (src/native_frame.rs): the window procedure, hit test, DPI.
 windows-sys = { version = "0.61", features = [
     "Win32_Foundation",
     "Win32_Security",
@@ -53,6 +59,8 @@ windows-sys = { version = "0.61", features = [
     "Win32_System_LibraryLoader",
     "Win32_System_Memory",
     "Win32_System_Threading",
+    "Win32_UI_HiDpi",
+    "Win32_UI_WindowsAndMessaging",
 ] }
 
 [target.'cfg(target_os = "macos")'.dependencies]

apps/solidcraft/src/control_server.rs

@@ -4,7 +4,7 @@
 use std::io::{BufRead, BufReader, Write};
 use std::net::{TcpListener, TcpStream};
 use std::sync::atomic::{AtomicUsize, Ordering};
-use std::sync::mpsc::{Receiver, Sender, channel};
+use std::sync::mpsc::{Receiver, Sender, TryRecvError, channel};
 use std::time::Duration;
 
 use serde_json::{Value, json};
@@ -18,8 +18,9 @@ const MAX_CONNECTIONS: usize = 16;
 const MAX_BAD_LINES: usize = 8;
 
 static OPEN: AtomicUsize = AtomicUsize::new(0);
-/// The token file this launch wrote, removed when the app ends.
-static TOKEN_FILE: std::sync::OnceLock<std::path::PathBuf> = std::sync::OnceLock::new();
+/// The token files this launch wrote (its `--control` port, the agent chat's endpoint), removed
+/// when the app ends.
+static TOKEN_FILES: std::sync::Mutex<Vec<std::path::PathBuf>> = std::sync::Mutex::new(Vec::new());
 
 /// A new random token: 32 bytes from the operating system, as hex.
 fn new_token() -> Option<String> {
@@ -30,30 +31,55 @@ fn new_token() -> Option<String> {
 
 /// Remove this launch's token file (at exit).
 pub fn remove_token_file() {
-    if let Some(p) = TOKEN_FILE.get() {
-        let _ = std::fs::remove_file(p);
+    if let Ok(files) = TOKEN_FILES.lock() {
+        for p in files.iter() {
+            let _ = std::fs::remove_file(p);
+        }
     }
 }
 
 pub fn start(port: u16, ctx: egui::Context) -> Receiver<ControlRequest> {
     let (tx, rx) = channel::<ControlRequest>();
     // Every connection must show the token before anything runs (docs/control-protocol.md).
-    let Some(token) = control_auth::env_token().or_else(new_token) else {
-        eprintln!("solidcraft: control server not started: no random token available");
-        return rx;
+    match control_auth::env_token().or_else(new_token) {
+        Some(token) => {
+            listen(port, token, tx, ctx, false);
+        }
+        None => eprintln!("solidcraft: control server not started: no random token available"),
+    }
+    rx
+}
+
+/// The agent chat's own endpoint for its agent's MCP server (docs/agent-chat.md): a free loopback
+/// port with a fresh token of its own (never `SOLIDCRAFT_CONTROL_TOKEN`), written to the usual
+/// token file, where the MCP server finds it, so the token never passes through the agent. Its
+/// requests go to `tx`, where the chat's gate reads them; one may wait long for the user's Allow.
+pub fn listen_agent(tx: Sender<ControlRequest>, ctx: egui::Context) -> Option<u16> {
+    let Some(token) = new_token() else {
+        eprintln!("solidcraft: agent chat endpoint not started: no random token available");
+        return None;
     };
+    listen(0, token, tx, ctx, true)
+}
+
+/// Listen on `port` (0: a free port the system picks) with `token`; the port it listens on.
+/// `patient`: every request may wait as long as a batch (a person decides on it).
+fn listen(port: u16, token: String, tx: Sender<ControlRequest>, ctx: egui::Context, patient: bool) -> Option<u16> {
     let listener = match TcpListener::bind(("127.0.0.1", port)) {
         Ok(l) => l,
         Err(e) => {
             eprintln!("solidcraft: control server failed to bind 127.0.0.1:{port}: {e}");
-            return rx;
+            return None;
         }
     };
+    let port = listener.local_addr().map(|a| a.port()).unwrap_or(port);
     match control_auth::token_path(port) {
         Some(path) => match control_auth::write_token_file(&path, &token) {
             Ok(()) => {
                 eprintln!("solidcraft: control server listening on 127.0.0.1:{port} (token in {})", path.display());
-                let _ = TOKEN_FILE.set(path);
+                if let Ok(mut files) = TOKEN_FILES.lock() {
+                    files.push(path);
+                }
             }
             Err(e) => eprintln!(
                 "solidcraft: control server listening on 127.0.0.1:{port}, but its token file {} could not be written ({e}); \
@@ -78,12 +104,12 @@ pub fn start(port: u16, ctx: egui::Context) -> Receiver<ControlRequest> {
             let ctx = ctx.clone();
             let token = token.clone();
             std::thread::spawn(move || {
-                serve(stream, &token, tx, ctx);
+                serve(stream, &token, tx, ctx, patient);
                 OPEN.fetch_sub(1, Ordering::Relaxed);
             });
         }
     });
-    rx
+    Some(port)
 }
 
 /// One line without its newline, or `None` at the end of the stream. A client that sends
@@ -134,12 +160,35 @@ fn refuse(out: &mut TcpStream, reader: &mut BufReader<TcpStream>) {
     let _ = std::io::copy(&mut reader.by_ref().take(64 * 1024), &mut std::io::sink());
 }
 
-fn serve(stream: TcpStream, token: &str, tx: Sender<ControlRequest>, ctx: egui::Context) {
+/// How long a request waits for the app's reply: most requests, and a batch (or every request,
+/// on a patient connection).
+#[derive(Clone, Copy)]
+struct Waits {
+    short: Duration,
+    long: Duration,
+}
+
+const WAITS: Waits = Waits { short: Duration::from_secs(60), long: Duration::from_secs(3600) };
+
+/// A request that timed out but is still running in the app (#1618): its id and method, and where
+/// its reply will land.
+struct Pending {
+    id: Value,
+    method: String,
+    reply: Receiver<Value>,
+}
+
+fn serve(stream: TcpStream, token: &str, tx: Sender<ControlRequest>, ctx: egui::Context, patient: bool) {
+    serve_with(stream, token, tx, ctx, patient, WAITS);
+}
+
+fn serve_with(stream: TcpStream, token: &str, tx: Sender<ControlRequest>, ctx: egui::Context, patient: bool, waits: Waits) {
     let Ok(read) = stream.try_clone() else { return };
     let mut out = stream;
     let mut reader = BufReader::new(read);
     let mut bad = 0usize;
     let mut authenticated = false;
+    let mut pending: Option<Pending> = None;
     loop {
         let line = match read_line(&mut reader, MAX_LINE) {
             Ok(Some(l)) => String::from_utf8_lossy(&l).into_owned(),
@@ -167,14 +216,46 @@ fn serve(stream: TcpStream, token: &str, tx: Sender<ControlRequest>, ctx: egui::
                 let id = msg.get("id").cloned().unwrap_or(Value::Null);
                 let method = msg.get("method").and_then(Value::as_str).unwrap_or("").to_string();
                 let params = msg.get("params").cloned().unwrap_or(json!({}));
-                // A batch replaces many short requests: the whole of it may take long (#743).
-                let wait = Duration::from_secs(if method == "engine.batch" { 3600 } else { 60 });
-                let (req, rrx) = ControlRequest::new(method, params);
-                if tx.send(req).is_err() {
-                    break;
-                }
-                ctx.request_repaint();
-                let mut r = rrx.recv_timeout(wait).unwrap_or_else(|_| json!({"ok": false, "error": "timeout"}));
+                // A request that timed out may have finished since (#1618).
+                let late = pending.as_ref().and_then(|p| match p.reply.try_recv() {
+                    Ok(reply) => Some(reply),
+                    Err(TryRecvError::Disconnected) => Some(json!({"ok": false, "error": "the app ended the request without a reply"})),
+                    Err(TryRecvError::Empty) => None,
+                });
+                let mut r = if method == "control.pending" {
+                    match (pending.take(), late) {
+                        (None, _) => json!({"ok": true, "result": {"pending": null}}),
+                        (Some(p), Some(reply)) => json!({"ok": true, "result": {"pending": p.id, "method": p.method, "done": true, "reply": reply}}),
+                        (Some(p), None) => {
+                            let r = json!({"ok": true, "result": {"pending": p.id, "method": p.method, "done": false}});
+                            pending = Some(p);
+                            r
+                        }
+                    }
+                } else if let Some(p) = pending.as_ref().filter(|_| late.is_none()) {
+                    // Nothing more is queued behind it, to run unseen when it ends.
+                    json!({"ok": false, "busy": true, "error": format!("busy: request {} (`{}`) is still running; ask `control.pending` for its result", p.id, p.method)})
+                } else {
+                    if late.is_some() {
+                        // Finished, and the client moved on without asking: it is dropped.
+                        pending = None;
+                    }
+                    // A batch replaces many short requests: the whole of it may take long (#743).
+                    let wait = if patient || method == "engine.batch" { waits.long } else { waits.short };
+                    let (req, rrx) = ControlRequest::new(method.clone(), params);
+                    if tx.send(req).is_err() {
+                        break;
+                    }
+                    ctx.request_repaint();
+                    match rrx.recv_timeout(wait) {
+                        Ok(r) => r,
+                        Err(_) => {
+                            let r = json!({"ok": false, "running": true, "error": format!("timeout: `{method}` is still running in the app and will still apply; ask `control.pending` for its result")});
+                            pending = Some(Pending { id: id.clone(), method, reply: rrx });
+                            r
+                        }
+                    }
+                };
                 if let Some(o) = r.as_object_mut() {
                     o.insert("id".into(), id);
                 }
@@ -202,6 +283,62 @@ fn serve(stream: TcpStream, token: &str, tx: Sender<ControlRequest>, ctx: egui::
 mod tests {
     use super::*;
 
+    /// #1618: a request that outlasts its wait says it is still running; the connection keeps its
+    /// reply for `control.pending`, and refuses other requests as `busy` until it lands, so none
+    /// is queued to run unseen behind it.
+    #[test]
+    fn a_timed_out_request_can_be_asked_for_later() {
+        let token = "0123456789abcdef0123456789abcdef";
+        let listener = TcpListener::bind("127.0.0.1:0").unwrap();
+        let addr = listener.local_addr().unwrap();
+        let (tx, rx) = channel::<ControlRequest>();
+        let ran = std::sync::Arc::new(std::sync::Mutex::new(Vec::<String>::new()));
+        let seen = ran.clone();
+        std::thread::spawn(move || {
+            for req in rx {
+                seen.lock().unwrap().push(req.method.clone());
+                if req.method == "slow" {
+                    std::thread::sleep(Duration::from_millis(400));
+                }
+                let _ = req.reply.send(json!({"ok": true, "result": req.method}));
+            }
+        });
+        let waits = Waits { short: Duration::from_millis(100), long: Duration::from_millis(100) };
+        std::thread::spawn(move || {
+            if let Some(stream) = listener.incoming().flatten().next() {
+                serve_with(stream, token, tx, egui::Context::default(), false, waits);
+            }
+        });
+        let s = TcpStream::connect(addr).unwrap();
+        s.set_read_timeout(Some(Duration::from_secs(10))).unwrap();
+        let mut out = s.try_clone().unwrap();
+        let mut lines = BufReader::new(s);
+        let mut ask = |v: Value| -> Value {
+            writeln!(out, "{v}").unwrap();
+            let mut l = String::new();
+            lines.read_line(&mut l).unwrap();
+            serde_json::from_str(&l).unwrap()
+        };
+        let r = ask(json!({"id": 1, "method": "slow", "token": token}));
+        assert!(r["ok"] == false && r["running"] == true && r["error"].as_str().is_some_and(|e| e.starts_with("timeout")), "{r}");
+        let r = ask(json!({"id": 2, "method": "ui.view"}));
+        assert!(r["busy"] == true && r["id"] == 2, "{r}");
+        let r = ask(json!({"id": 3, "method": "control.pending"}));
+        assert_eq!((&r["result"]["pending"], &r["result"]["done"]), (&json!(1), &json!(false)), "{r}");
+        std::thread::sleep(Duration::from_millis(600));
+        let r = ask(json!({"id": 4, "method": "control.pending"}));
+        assert_eq!(
+            (&r["result"]["pending"], &r["result"]["done"], &r["result"]["reply"]["result"]),
+            (&json!(1), &json!(true), &json!("slow")),
+            "{r}"
+        );
+        let r = ask(json!({"id": 5, "method": "control.pending"}));
+        assert_eq!(r["result"]["pending"], Value::Null, "{r}");
+        let r = ask(json!({"id": 6, "method": "ui.view"}));
+        assert_eq!((&r["ok"], &r["result"]), (&json!(true), &json!("ui.view")), "{r}");
+        assert_eq!(*ran.lock().unwrap(), ["slow", "ui.view"], "the busy request never reached the app");
+    }
+
     /// #205: a connection runs nothing until a request carries the launch's token; a wrong or
     /// missing token, or garbage, is refused and the connection closed. Once shown, the token
     /// need not be repeated on that connection.
@@ -223,7 +360,7 @@ mod tests {
         std::thread::spawn(move || {
             for stream in listener.incoming().flatten() {
                 let tx = tx.clone();
-                std::thread::spawn(move || serve(stream, token, tx, egui::Context::default()));
+                std::thread::spawn(move || serve(stream, token, tx, egui::Context::default(), false));
             }
         });
         let session = |lines: &[String]| {

apps/solidcraft/src/main.rs

@@ -6,7 +6,7 @@
 //! the software renderer; see `startup` and docs/book/src/guide/troubleshooting.md.
 //!
 //! A `.step`/`.stp` file opens as a new design holding the file's bodies (an Import feature); a
-//! `.3mf`/`.stl` file as a new design holding mesh bodies.
+//! `.3mf`/`.stl`/`.obj`/`.glb`/`.gltf` file as a new design holding mesh bodies.
 //!
 //! `--control <port>` (or `SOLIDCRAFT_CONTROL_PORT`) starts a localhost JSON-lines control
 //! server: `{"id":1,"method":"engine.execute","params":{"command":"solid.box","params":{…}}}`.
@@ -21,6 +21,8 @@ mod app_icon;
 mod control_server;
 #[cfg(target_os = "windows")]
 mod native_crash;
+#[cfg(target_os = "windows")]
+mod native_frame;
 #[cfg(target_os = "macos")]
 mod open_documents;
 #[cfg(any(target_os = "windows", target_os = "linux"))]
@@ -75,6 +77,9 @@ impl eframe::App for App {
         }
     }
     fn raw_input_hook(&mut self, _ctx: &egui::Context, raw: &mut egui::RawInput) {
+        // Before the app's own hook, which adds the control channel's events.
+        #[cfg(any(target_os = "windows", target_os = "linux"))]
+        self.space_mouse.raw_input_hook(self.solve.preferences.space_mouse_enabled, raw);
         self.solve.raw_input_hook(raw);
     }
     fn ui(&mut self, ui: &mut egui::Ui, _frame: &mut eframe::Frame) {
@@ -84,6 +89,8 @@ impl eframe::App for App {
         storage.set_string(solidcraft_ui_egui::prefs::STORAGE_KEY, self.solve.prefs());
     }
     fn on_exit(&mut self) {
+        // The agent chat's agent and everything it started end with the app.
+        solidcraft_ui_egui::agent_chat::shutdown(&mut self.solve);
         solidcraft_ui_egui::recovery_ui::close(&mut self.solve);
         solidcraft_engine::crash::end_session();
         // An update asked to restart into the new version or to run its installer.
@@ -104,7 +111,7 @@ fn services(cc: &eframe::CreationContext<'_>) -> Services {
             let future = open_parent
                 .clone()
                 .add_filter(
-                    "Designs, STEP, IGES and meshes",
+                    "Designs, CAD files and meshes",
                     &[
                         io::DESIGN_EXT,
                         io::LEGACY_DESIGN_EXT,
@@ -117,16 +124,27 @@ fn services(cc: &eframe::CreationContext<'_>) -> Services {
                         "iges",
                         "IGS",
                         "IGES",
+                        "FCStd",
+                        "fcstd",
+                        "3dm",
+                        "3DM",
                         "3mf",
                         "3MF",
                         "stl",
                         "STL",
+                        "obj",
+                        "OBJ",
+                        "glb",
+                        "GLB",
+                        "gltf",
+                        "GLTF",
                     ],
                 )
                 .add_filter("SolidCraft design (container or JSON)", &[io::DESIGN_EXT, io::LEGACY_DESIGN_EXT, "json"])
                 .add_filter("STEP", &["step", "stp", "STEP", "STP"])
                 .add_filter("IGES", &["igs", "iges", "IGS", "IGES"])
-                .add_filter("Mesh (3MF, STL)", &["3mf", "3MF", "stl", "STL"])
+                .add_filter("FreeCAD and Rhino", &["FCStd", "fcstd", "3dm", "3DM"])
+                .add_filter("Mesh (3MF, STL, OBJ, glTF)", &["3mf", "3MF", "stl", "STL", "obj", "OBJ", "glb", "GLB", "gltf", "GLTF"])
                 .add_filter("Sketch drawings (DXF, SVG)", &["dxf", "DXF", "svg", "SVG"])
                 .add_filter("All files", &["*"])
                 .pick_file();
@@ -155,6 +173,10 @@ fn services(cc: &eframe::CreationContext<'_>) -> Services {
         graphics_path: graphics_path().map(|p| p.to_string_lossy().to_string()),
         http_get: Some(std::sync::Arc::new(http_get)),
         http_download: Some(std::sync::Arc::new(http_download)),
+        // Already an installed app: only the browser build offers to install.
+        install_app: None,
+        agent_http: Some(std::sync::Arc::new(agent_http)),
+        secrets: Some(std::sync::Arc::new(Keychain)),
         show_in_folder: Some(Box::new(|path| {
             let folder = std::path::Path::new(path).parent().unwrap_or_else(|| std::path::Path::new("."));
             let mut command = std::process::Command::new(if cfg!(target_os = "windows") {
@@ -211,6 +233,71 @@ fn http_download(url: &str, to: &std::path::Path, progress: &dyn Fn(u64, Option<
     Ok(())
 }
 
+/// HTTP for the agent chat's API agents (OpenAI-compatible endpoints, docs/agent-chat.md): to the
+/// URL the user configured, which may be plain HTTP on this computer (Ollama, LM Studio). No
+/// redirects (a key must not follow one elsewhere), at most 16 MB back.
+fn agent_http(r: &solidcraft_ui_egui::agent_chat::backend::HttpRequest) -> Result<(u16, Vec<u8>), String> {
+    use std::time::Duration;
+    let tls = ureq::tls::TlsConfig::builder()
+        .root_certs(ureq::tls::RootCerts::PlatformVerifier)
+        .unversioned_rustls_crypto_provider(std::sync::Arc::new(rustls::crypto::ring::default_provider()))
+        .build();
+    let agent: ureq::Agent = ureq::Agent::config_builder()
+        .tls_config(tls)
+        .http_status_as_error(false)
+        .timeout_global(Some(Duration::from_secs(r.timeout_s.clamp(1, 900))))
+        .timeout_connect(Some(Duration::from_secs(10)))
+        .user_agent("SolidCraft")
+        .max_redirects(0)
+        .build()
+        .into();
+    let mut response = if r.method == "POST" {
+        let mut req = agent.post(&r.url);
+        for (k, v) in &r.headers {
+            req = req.header(k, v);
+        }
+        req.send(r.body.as_deref().unwrap_or_default())
+    } else {
+        let mut req = agent.get(&r.url);
+        for (k, v) in &r.headers {
+            req = req.header(k, v);
+        }
+        req.call()
+    }
+    .map_err(|e| e.to_string())?;
+    let status = response.status().as_u16();
+    let body = response.body_mut().with_config().limit(16 << 20).read_to_vec().map_err(|e| e.to_string())?;
+    Ok((status, body))
+}
+
+/// API keys in the system keychain (service "SolidCraft agent chat", one entry per agent).
+struct Keychain;
+
+impl Keychain {
+    fn entry(id: &str) -> Result<keyring::Entry, String> {
+        keyring::Entry::new("SolidCraft agent chat", id).map_err(|e| e.to_string())
+    }
+}
+
+impl solidcraft_ui_egui::agent_chat::backend::Secrets for Keychain {
+    fn get(&self, id: &str) -> Result<Option<String>, String> {
+        match Self::entry(id)?.get_password() {
+            Ok(p) => Ok(Some(p)),
+            Err(keyring::Error::NoEntry) => Ok(None),
+            Err(e) => Err(e.to_string()),
+        }
+    }
+    fn set(&self, id: &str, secret: &str) -> Result<(), String> {
+        Self::entry(id)?.set_password(secret).map_err(|e| e.to_string())
+    }
+    fn delete(&self, id: &str) -> Result<(), String> {
+        match Self::entry(id)?.delete_credential() {
+            Ok(()) | Err(keyring::Error::NoEntry) => Ok(()),
+            Err(e) => Err(e.to_string()),
+        }
+    }
+}
+
 /// One GET to GitHub: a 200 answer, or why not (rate limits included).
 fn http_call(url: &str, timeout: std::time::Duration) -> Result<ureq::http::Response<ureq::Body>, solidcraft_ui_egui::update::FetchError> {
     use solidcraft_ui_egui::update::FetchError;
@@ -465,6 +552,15 @@ fn main() -> eframe::Result {
             let mut app = SolveApp::new(Session::default(), services(cc));
             app.apply_off_thread = Some(solidcraft_ui_egui::dialogs::APPLY_AT_ONCE);
             app.custom_titlebar = CUSTOM_TITLEBAR;
+            // Windows: the OS hit test offers the resize border, at the window's DPI, from the
+            // first message (#1381).
+            #[cfg(target_os = "windows")]
+            {
+                app.native_resize_border = CUSTOM_TITLEBAR && native_frame::install(cc);
+                if CUSTOM_TITLEBAR && !app.native_resize_border {
+                    eprintln!("SolidCraft window: no native resize border; egui edge zones instead");
+                }
+            }
             app.integrated_titlebar = cfg!(target_os = "macos");
             app.cpu_meshing = safe_mode;
             if let Some(p) = cc.storage.and_then(|s| solidcraft_ui_egui::prefs::stored(|k| s.get_string(k))).filter(|_| !safe_mode) {
@@ -474,6 +570,7 @@ fn main() -> eframe::Result {
                 eprintln!("SolidCraft graphics: {:?}, MSAA {}x (requested {}x)", rs.adapter.get_info().backend, rs.msaa_samples, samples);
                 solidcraft_engine::crash::phase("viewport pipelines (shader compile)");
                 app.set_wgpu(rs, DEPTH_BITS, STENCIL_BITS, rs.msaa_samples);
+                solidcraft_ui_egui::gpu::install_picture_renderer(rs);
                 // The graphics driver is loaded now; it may have put its own exception filter
                 // in front of ours.
                 #[cfg(target_os = "windows")]
@@ -490,6 +587,10 @@ fn main() -> eframe::Result {
                 let rx = control_server::start(port, cc.egui_ctx.clone());
                 app = app.with_control(rx);
             }
+            // The agent chat's MCP bridge reaches the app through an endpoint of its own, started
+            // on a free port the first time the chat connects (docs/agent-chat.md).
+            let ctx = cc.egui_ctx.clone();
+            app.agent_chat.control_starter = Some(Box::new(move |tx| control_server::listen_agent(tx, ctx.clone())));
             if sample {
                 if let Err(e) = app.session.run_script(&solidcraft_engine::sample::script()) {
                     app.set_status(format!("sample: {e}"), true);

apps/solidcraft/src/native_frame.rs

@@ -0,0 +1,177 @@
+//! Windows: the resize border of the window without OS decorations (#1381).
+//!
+//! The window keeps its native thick frame (`WS_THICKFRAME`, so Aero Snap, Win+arrows and the
+//! OS's own move and size loops work) but winit draws no frame: its `WM_NCCALCSIZE` makes the
+//! whole window client area, and every point then hit-tests as `HTCLIENT`. This module puts the
+//! resize border back by answering `WM_NCHITTEST` itself: within Windows' resize-border width
+//! for the window's current DPI from each edge (`solidcraft_ui_egui::titlebar::resize_hit`;
+//! 8 px at 100 %, corners win), it returns `HTLEFT`, `HTTOPRIGHT`, … So from the first message
+//! the OS shows its resize cursors and runs its own resize, whatever egui has laid out, whatever
+//! the scale; nothing waits for a first frame or a first size change.
+//!
+//! It also answers `WM_GETDPISCALEDSIZE` with the size the window will really have at the new
+//! DPI (the same logical size, as winit computes it), so the rect Windows suggests while the
+//! title bar is dragged onto a monitor with another scale is the rect winit then applies: the
+//! window rescales once at the crossing and stays under the pointer, instead of the OS's move
+//! loop and winit disagreeing about a frame the window doesn't have.
+//!
+//! Replacing a window procedure has no safe API, hence the `unsafe_code` allowance on this
+//! module (the app crate denies it; see `native_crash.rs` and `open_documents.rs` for the others).
+//! The procedure is installed once, on the thread that owns the window, for the main window only,
+//! and calls the previous one (winit's) for everything it doesn't answer.
+#![allow(unsafe_code)]
+
+use std::sync::atomic::{AtomicIsize, Ordering};
+
+use raw_window_handle::{HasWindowHandle, RawWindowHandle};
+use solidcraft_ui_egui::titlebar;
+use windows_sys::Win32::Foundation::{HWND, LPARAM, LRESULT, RECT, SIZE, WPARAM};
+use windows_sys::Win32::UI::HiDpi::{GetDpiForWindow, GetSystemMetricsForDpi};
+use windows_sys::Win32::UI::WindowsAndMessaging::{
+    CallWindowProcW, GWL_STYLE, GWLP_WNDPROC, GetClientRect, GetWindowLongPtrW, GetWindowRect, HTBOTTOM, HTBOTTOMLEFT, HTBOTTOMRIGHT, HTLEFT,
+    HTRIGHT, HTTOP, HTTOPLEFT, HTTOPRIGHT, IsIconic, IsZoomed, SM_CXPADDEDBORDER, SM_CXSIZEFRAME, SetWindowLongPtrW, WM_GETDPISCALEDSIZE,
+    WM_NCDESTROY, WM_NCHITTEST, WNDPROC, WS_THICKFRAME,
+};
+
+/// The window procedure ours replaced (winit's), as an address; 0 before [`install`].
+static PREVIOUS: AtomicIsize = AtomicIsize::new(0);
+
+/// Answer the main window's hit test and DPI-size questions from now on. Call it once, on the
+/// thread that created the window (eframe's app creator). `false` if it isn't a Win32 window.
+pub fn install(window: &impl HasWindowHandle) -> bool {
+    let Ok(handle) = window.window_handle() else { return false };
+    let RawWindowHandle::Win32(w) = handle.as_raw() else { return false };
+    let hwnd = w.hwnd.get() as HWND;
+    if PREVIOUS.load(Ordering::SeqCst) != 0 {
+        return false;
+    }
+    // SAFETY: `hwnd` is the live window eframe just created on this thread; `frame_proc` has the
+    // WNDPROC signature and stays valid for the life of the process. SetWindowLongPtrW returns
+    // the previous procedure, which `frame_proc` calls for every other message.
+    let previous = unsafe { SetWindowLongPtrW(hwnd, GWLP_WNDPROC, frame_proc as *const () as isize as _) };
+    // `as _`: on 32-bit Windows SetWindowLongPtrW is SetWindowLongW, which takes and
+    // returns i32.
+    if previous == 0 {
+        return false;
+    }
+    PREVIOUS.store(previous as _, Ordering::SeqCst);
+    true
+}
+
+/// The procedure ours replaced.
+fn previous() -> WNDPROC {
+    let p = PREVIOUS.load(Ordering::SeqCst);
+    // SAFETY: a nonzero value is the WNDPROC that SetWindowLongPtrW returned in `install`.
+    (p != 0).then(|| unsafe { std::mem::transmute::<isize, unsafe extern "system" fn(HWND, u32, WPARAM, LPARAM) -> LRESULT>(p) })
+}
+
+unsafe extern "system" fn frame_proc(hwnd: HWND, msg: u32, wparam: WPARAM, lparam: LPARAM) -> LRESULT {
+    let prev = previous();
+    // SAFETY: the arguments are the message as Windows delivered it to this window.
+    let call_previous = || unsafe { CallWindowProcW(prev, hwnd, msg, wparam, lparam) };
+    match msg {
+        WM_NCHITTEST => {
+            let default = call_previous();
+            // Screen coordinates, signed (monitors left of or above the primary one).
+            let (x, y) = (i32::from(lparam as u16 as i16), i32::from((lparam >> 16) as u16 as i16));
+            // The border, else what winit and the system say (`HTCLIENT` everywhere else).
+            border_hit(hwnd, x, y).map_or(default, |hit| hit as LRESULT)
+        }
+        WM_GETDPISCALEDSIZE => {
+            let new_dpi = wparam as u32;
+            // SAFETY: for this message lParam points to a SIZE the system reads back.
+            match (resizable(hwnd), client_size(hwnd), unsafe { (lparam as *mut SIZE).as_mut() }) {
+                (true, Some(size), Some(out)) => {
+                    // SAFETY: a window handle the system passed in.
+                    let old_dpi = unsafe { GetDpiForWindow(hwnd) };
+                    match titlebar::dpi_scaled_size(size, old_dpi, new_dpi) {
+                        Some((cx, cy)) => {
+                            *out = SIZE { cx, cy };
+                            1
+                        }
+                        None => call_previous(),
+                    }
+                }
+                _ => call_previous(),
+            }
+        }
+        WM_NCDESTROY => {
+            // Hand the window back to winit's procedure for its last message.
+            if prev.is_some() {
+                // SAFETY: restores the procedure this window had before `install`.
+                unsafe { SetWindowLongPtrW(hwnd, GWLP_WNDPROC, PREVIOUS.load(Ordering::SeqCst) as _) };
+            }
+            call_previous()
+        }
+        _ => call_previous(),
+    }
+}
+
+/// The window can be resized by its border now: it has the thick frame (not fullscreen, which
+/// drops it) and is neither maximized nor minimized.
+fn resizable(hwnd: HWND) -> bool {
+    // SAFETY: plain queries on a window handle the system passed in.
+    unsafe {
+        let style = GetWindowLongPtrW(hwnd, GWL_STYLE) as u32;
+        style & WS_THICKFRAME != 0 && IsZoomed(hwnd) == 0 && IsIconic(hwnd) == 0
+    }
+}
+
+/// The client area's size in pixels (the whole window: winit gives it no frame).
+fn client_size(hwnd: HWND) -> Option<(i32, i32)> {
+    let mut r = RECT { left: 0, top: 0, right: 0, bottom: 0 };
+    // SAFETY: `r` is a valid RECT to fill.
+    (unsafe { GetClientRect(hwnd, &mut r) } != 0).then_some((r.right - r.left, r.bottom - r.top))
+}
+
+/// Windows' resize border at the window's DPI: the sizing frame plus its padding, as Windows
+/// itself sizes it, or 8 px scaled when the system has no answer.
+fn border_px(hwnd: HWND) -> f32 {
+    // SAFETY: plain queries.
+    let (dpi, metric) = unsafe {
+        let dpi = GetDpiForWindow(hwnd);
+        (dpi, GetSystemMetricsForDpi(SM_CXSIZEFRAME, dpi) + GetSystemMetricsForDpi(SM_CXPADDEDBORDER, dpi))
+    };
+    let scale = if dpi > 0 { dpi as f32 / 96.0 } else { 1.0 };
+    if metric > 0 { metric as f32 } else { titlebar::resize_border_px(scale) }
+}
+
+/// The `HT*` resize code at screen point (`x`, `y`), if it is on the border.
+fn border_hit(hwnd: HWND, x: i32, y: i32) -> Option<u32> {
+    if !resizable(hwnd) {
+        return None;
+    }
+    let mut r = RECT { left: 0, top: 0, right: 0, bottom: 0 };
+    // SAFETY: `r` is a valid RECT to fill.
+    if unsafe { GetWindowRect(hwnd, &mut r) } == 0 {
+        return None;
+    }
+    let w = egui::Rect::from_min_max(egui::pos2(r.left as f32, r.top as f32), egui::pos2(r.right as f32, r.bottom as f32));
+    titlebar::resize_hit(w, egui::pos2(x as f32, y as f32), border_px(hwnd)).map(hit_code)
+}
+
+fn hit_code(d: egui::ResizeDirection) -> u32 {
+    use egui::ResizeDirection::*;
+    match d {
+        North => HTTOP,
+        South => HTBOTTOM,
+        West => HTLEFT,
+        East => HTRIGHT,
+        NorthWest => HTTOPLEFT,
+        NorthEast => HTTOPRIGHT,
+        SouthWest => HTBOTTOMLEFT,
+        SouthEast => HTBOTTOMRIGHT,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn every_direction_has_its_own_hit_code() {
+        use egui::ResizeDirection::*;
+        let codes: Vec<u32> = [North, South, West, East, NorthWest, NorthEast, SouthWest, SouthEast].into_iter().map(hit_code).collect();
+        assert_eq!(codes, vec![HTTOP, HTBOTTOM, HTLEFT, HTRIGHT, HTTOPLEFT, HTTOPRIGHT, HTBOTTOMLEFT, HTBOTTOMRIGHT]);
+    }
+}

apps/solidcraft/src/space_mouse.rs

@@ -15,79 +15,18 @@ use hid_descriptor::Layout;
 use hidapi::{DeviceInfo, HidApi};
 use quick_xml::Reader;
 use quick_xml::events::Event;
-use solidcraft_engine::render::Camera;
 use solidcraft_ui_egui::SolveApp;
+use solidcraft_ui_egui::space_mouse::{Axes, AxisRule, DriverMapping, WheelGuard, navigate_frame};
 
 const STALE_AFTER: Duration = Duration::from_millis(150);
 const RETRY_AFTER: Duration = Duration::from_secs(2);
 const MAX_PROFILE_BYTES: u64 = 1024 * 1024;
 
-#[derive(Clone, Copy, Debug, Default, PartialEq)]
-struct Axes {
-    translation: [i16; 3],
-    rotation: [i16; 3],
-}
-
-#[derive(Clone, Copy, Debug, PartialEq)]
-struct AxisRule {
-    output: usize,
-    enabled: bool,
-    reversed: bool,
-    scale: f64,
-}
-
-#[derive(Clone, Copy, Debug, PartialEq)]
-struct DriverMapping {
-    axes: [AxisRule; 6],
-    overall_scale: f64,
-}
-
-impl Default for DriverMapping {
-    fn default() -> Self {
-        Self { axes: std::array::from_fn(|output| AxisRule { output, enabled: true, reversed: false, scale: 1.0 }), overall_scale: 1.0 }
-    }
-}
-
-impl DriverMapping {
-    /// The mapping used when no 3DxWare profile is found. On Linux there is no 3DxWare, so it is
-    /// what the driver applies by default in object mode (#1172): the physical Ry and Rz swapped
-    /// and reversed, so a tilt left/right rolls and a twist spins. Elsewhere the driver writes a
-    /// profile, and the raw axes are used until it does.
-    fn without_profile() -> Self {
-        let mut mapping = Self::default();
-        if cfg!(target_os = "linux") {
-            mapping.axes[4] = AxisRule { output: 5, enabled: true, reversed: true, scale: 1.0 };
-            mapping.axes[5] = AxisRule { output: 4, enabled: true, reversed: true, scale: 1.0 };
-        }
-        mapping
-    }
-}
-
-#[derive(Clone, Copy, Debug, Default, PartialEq)]
-struct Motion {
-    translation: [f64; 3],
-    rotation: [f64; 3],
-}
-
-impl DriverMapping {
-    fn apply(self, axes: Axes) -> Motion {
-        let raw = [
-            normalized(axes.translation[0]),
-            normalized(axes.translation[1]),
-            normalized(axes.translation[2]),
-            normalized(axes.rotation[0]),
-            normalized(axes.rotation[1]),
-            normalized(axes.rotation[2]),
-        ];
-        let mut logical = [0.0; 6];
-        for (input, rule) in self.axes.iter().enumerate() {
-            if rule.enabled {
-                let sign = if rule.reversed { -1.0 } else { 1.0 };
-                logical[rule.output] = raw[input] * sign * rule.scale * self.overall_scale;
-            }
-        }
-        Motion { translation: [logical[0], logical[1], logical[2]], rotation: [logical[3], logical[4], logical[5]] }
-    }
+/// The mapping used when no 3DxWare profile is found: what the driver applies by default in
+/// object mode. On Linux there is no 3DxWare (#1172); on Windows 3DxWare has no profile for
+/// SolidCraft until one is made, and the raw axes swap roll and spin (#1380).
+fn without_profile() -> DriverMapping {
+    DriverMapping::object_mode()
 }
 
 #[derive(Clone, Copy, Debug, Default)]
@@ -381,6 +320,9 @@ pub struct SpaceMouse {
     last_frame: Instant,
     driver_mapping: DriverMapping,
     mapping_checked_at: Instant,
+    /// Drops 3DxWare's emulated wheel while the cap moves (#1380).
+    wheel: WheelGuard,
+    started: Instant,
 }
 
 impl SpaceMouse {
@@ -395,84 +337,53 @@ impl SpaceMouse {
         Self {
             shared,
             last_frame: now,
-            driver_mapping: load_driver_mapping().unwrap_or_else(DriverMapping::without_profile),
+            driver_mapping: load_driver_mapping().unwrap_or_else(without_profile),
             mapping_checked_at: now,
+            wheel: WheelGuard::default(),
+            started: now,
         }
     }
 
+    /// Before the app's own hook (which adds the control channel's events): with navigation on,
+    /// the wheel events 3DxWare makes from the cap's motion are dropped.
+    pub fn raw_input_hook(&mut self, enabled: bool, raw: &mut egui::RawInput) {
+        if !enabled {
+            return;
+        }
+        let now = Instant::now();
+        let moving = self.shared.lock().map(|reading| reading.current(now).moving()).unwrap_or(false);
+        self.wheel.filter(moving, now.duration_since(self.started).as_secs_f64(), &mut raw.events);
+    }
+
     pub fn tick(&mut self, app: &mut SolveApp, ctx: &Context) {
         let now = Instant::now();
-        let seconds = now.duration_since(self.last_frame).as_secs_f64().min(0.05);
+        let seconds = now.duration_since(self.last_frame).as_secs_f64();
         self.last_frame = now;
         if now.duration_since(self.mapping_checked_at) >= RETRY_AFTER {
-            let updated = load_driver_mapping().unwrap_or_else(DriverMapping::without_profile);
+            let updated = load_driver_mapping().unwrap_or_else(without_profile);
             if updated != self.driver_mapping {
                 log::info!("3D mouse: applying updated 3DxWare axis profile");
                 self.driver_mapping = updated;
             }
             self.mapping_checked_at = now;
         }
-        if !app.preferences.space_mouse_enabled || app.home.open {
-            return;
-        }
         let axes = match self.shared.lock() {
             Ok(reading) => reading.current(now),
             Err(_) => return,
         };
-        if axes == Axes::default() {
-            return;
-        }
-        let speed = f64::from(app.preferences.space_mouse_speed);
-        if !speed.is_finite() {
-            return;
-        }
-        app.begin_external_navigation();
-        let height = app.viewport.rect.map_or(600.0, |rect| f64::from(rect.height().max(1.0)));
-        navigate(
-            &mut app.cam,
-            self.driver_mapping.apply(axes),
-            seconds * speed.clamp(0.1, 5.0),
-            height,
-            app.session.active_sketch.is_some(),
-            app.preferences.zoom_reverse,
-        );
-        ctx.request_repaint_after(Duration::from_millis(16));
-    }
-}
-
-/// A small dead zone avoids drift at rest. A full cap deflection takes roughly one viewport
-/// per second to pan and about two radians per second to turn, independent of frame rate.
-fn normalized(value: i16) -> f64 {
-    let v = f64::from(value);
-    if v.abs() <= 20.0 { 0.0 } else { v.signum() * ((v.abs() - 20.0) / 330.0).min(1.0) }
-}
-
-fn navigate(cam: &mut Camera, motion: Motion, seconds: f64, height: f64, sketch: bool, reverse_zoom: bool) {
-    if !(seconds > 0.0) || !seconds.is_finite() {
-        return;
-    }
-    let [x, y, z] = motion.translation;
-    let [rx, ry, rz] = motion.rotation;
-    // Logical 3DxWare coordinates are X = left/right, Y = zoom and Z = up/down. The user's
-    // profile above can swap the physical forward/back and up/down axes before they reach here.
-    cam.pan(x * height * 0.6 * seconds, z * height * 0.6 * seconds, height);
-    let zoom_sign = if reverse_zoom { -1.0 } else { 1.0 };
-    cam.zoom_at((-y * zoom_sign * 1.5 * seconds).exp(), None);
-    if !sketch {
-        // These are logical 3DxWare coordinates after the profile mapping above: Rx is Tilt,
-        // Ry is Roll and Rz is Spin. The KMJ profile swaps physical Ry/Rz for the selected
-        // navigation mode, so swapping them again here would make Roll behave like Spin.
-        cam.orbit(ry * 250.0 * seconds, rx * 250.0 * seconds);
-        cam.roll_by(rz * 2.0 * seconds);
+        navigate_frame(app, ctx, self.driver_mapping, axes, seconds);
     }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
+    use solidcraft_ui_egui::space_mouse::{DeviceMotion, Motion};
 
-    fn raw(axes: Axes) -> Motion {
-        DriverMapping::default().apply(axes)
+    /// The logical axes a reading reaches. Logical Rz rolls the view and logical Ry turns it about
+    /// its vertical (`navigation::device_camera` in solidcraft-ui-egui, tested there).
+    fn rotation(mapping: DriverMapping, rotation: [i16; 3]) -> [f64; 3] {
+        mapping.apply(Axes { translation: [0; 3], rotation }).rotation
     }
 
     #[test]
@@ -519,69 +430,6 @@ mod tests {
         assert_eq!(reading.current(now), Axes { translation: [1, 2, 3], rotation: [4, 5, 6] });
     }
 
-    #[test]
-    fn six_axes_move_the_camera_and_sketches_keep_their_orientation() {
-        let mut cam = Camera::default();
-        let before = cam;
-        navigate(&mut cam, raw(Axes { translation: [350, 350, 350], rotation: [350, 350, 350] }), 0.02, 600.0, false, false);
-        assert_ne!(cam.target, before.target);
-        assert!(cam.distance < before.distance);
-        assert_ne!(cam.yaw, before.yaw);
-        assert_ne!(cam.pitch, before.pitch);
-        assert_ne!(cam.roll, before.roll);
-        let orientation = (cam.yaw, cam.pitch, cam.roll);
-        navigate(&mut cam, raw(Axes { translation: [350, 0, 0], rotation: [350, 350, 350] }), 0.02, 600.0, true, false);
-        assert_eq!((cam.yaw, cam.pitch, cam.roll), orientation);
-        assert!(cam.is_valid());
-    }
-
-    #[test]
-    fn individual_axes_have_physical_spacemouse_meaning() {
-        let before = Camera::default();
-
-        let mut slide = before;
-        navigate(&mut slide, raw(Axes { translation: [350, 0, 0], rotation: [0; 3] }), 0.02, 600.0, false, false);
-        assert_ne!(slide.target, before.target);
-        assert_eq!(slide.distance, before.distance);
-
-        let mut push = before;
-        navigate(&mut push, raw(Axes { translation: [0, 350, 0], rotation: [0; 3] }), 0.02, 600.0, false, false);
-        assert_eq!(push.target, before.target);
-        assert!(push.distance < before.distance);
-
-        let mut lift = before;
-        navigate(&mut lift, raw(Axes { translation: [0, 0, 350], rotation: [0; 3] }), 0.02, 600.0, false, false);
-        assert_ne!(lift.target, before.target);
-        assert_eq!(lift.distance, before.distance);
-
-        let mut tilt = before;
-        navigate(&mut tilt, raw(Axes { translation: [0; 3], rotation: [350, 0, 0] }), 0.02, 600.0, false, false);
-        assert_eq!((tilt.yaw, tilt.roll), (before.yaw, before.roll));
-        assert_ne!(tilt.pitch, before.pitch);
-
-        let mut roll = before;
-        navigate(&mut roll, raw(Axes { translation: [0; 3], rotation: [0, 350, 0] }), 0.02, 600.0, false, false);
-        assert_eq!((roll.pitch, roll.roll), (before.pitch, before.roll));
-        assert_ne!(roll.yaw, before.yaw);
-
-        let mut twist = before;
-        navigate(&mut twist, raw(Axes { translation: [0; 3], rotation: [0, 0, 350] }), 0.02, 600.0, false, false);
-        assert_eq!((twist.yaw, twist.pitch), (before.yaw, before.pitch));
-        assert_ne!(twist.roll, before.roll);
-    }
-
-    #[test]
-    fn reverse_zoom_setting_applies_to_spacemouse() {
-        let before = Camera::default();
-        let motion = raw(Axes { translation: [0, 350, 0], rotation: [0; 3] });
-        let mut normal = before;
-        navigate(&mut normal, motion, 0.02, 600.0, false, false);
-        let mut reversed = before;
-        navigate(&mut reversed, motion, 0.02, 600.0, false, true);
-        assert!(normal.distance < before.distance);
-        assert!(reversed.distance > before.distance);
-    }
-
     #[test]
     fn applies_3dxware_axis_swaps_and_reversals() {
         let profile = br#"
@@ -601,7 +449,7 @@ mod tests {
     }
 
     #[test]
-    fn without_a_profile_linux_uses_the_drivers_object_mode_axes() {
+    fn without_a_profile_the_drivers_object_mode_axes_are_used() {
         // 3DxWare's object-mode mapping, as a profile (#1172: confirmed on a SpaceMouse Compact).
         let object_mode = br#"
             <AppCfg><Devices><Device><AxisBank>
@@ -614,39 +462,15 @@ mod tests {
             </AxisBank></Device></Devices></AppCfg>
         "#;
         let profile = parse_driver_mapping(object_mode).expect("valid 3DxWare profile");
-        if cfg!(target_os = "linux") {
-            assert_eq!(DriverMapping::without_profile(), profile);
-            // Tilting the cap rolls the view and twisting it spins it, as with the driver.
-            let before = Camera::default();
-            let mut tilt = before;
-            navigate(
-                &mut tilt,
-                DriverMapping::without_profile().apply(Axes { translation: [0; 3], rotation: [0, 350, 0] }),
-                0.02,
-                600.0,
-                false,
-                false,
-            );
-            assert_eq!((tilt.yaw, tilt.pitch), (before.yaw, before.pitch));
-            assert_ne!(tilt.roll, before.roll);
-            let mut twist = before;
-            navigate(
-                &mut twist,
-                DriverMapping::without_profile().apply(Axes { translation: [0; 3], rotation: [0, 0, 350] }),
-                0.02,
-                600.0,
-                false,
-                false,
-            );
-            assert_ne!(twist.yaw, before.yaw);
-            assert_eq!(twist.roll, before.roll);
-        } else {
-            assert_eq!(DriverMapping::without_profile(), DriverMapping::default());
-        }
+        // On every platform (#1172 on Linux, #1380 on Windows).
+        assert_eq!(without_profile(), profile);
+        // Tilting the cap rolls the view and twisting it spins it, as with the driver.
+        assert_eq!(rotation(without_profile(), [0, 350, 0]), [0.0, 0.0, -1.0]);
+        assert_eq!(rotation(without_profile(), [0, 0, 350]), [0.0, -1.0, 0.0]);
     }
 
     #[test]
-    fn mapped_roll_and_spin_reach_distinct_camera_rotations() {
+    fn mapped_roll_and_spin_reach_the_roll_and_turn_axes() {
         let profile = br#"
             <AppCfg><Devices><Device><AxisBank>
               <Axis><Enabled>true</Enabled><Input><ActionID>HIDMultiAxis_Ry</ActionID></Input><Output><ActionID>HIDMultiAxis_Rz</ActionID><Reversed>false</Reversed></Output></Axis>
@@ -654,16 +478,90 @@ mod tests {
             </AxisBank></Device></Devices></AppCfg>
         "#;
         let mapping = parse_driver_mapping(profile).expect("valid 3DxWare profile");
-        let before = Camera::default();
+        // The physical roll reaches the roll axis only, and the physical spin the turn only.
+        assert_eq!(rotation(mapping, [0, 350, 0]), [0.0, 0.0, 1.0]);
+        assert_eq!(rotation(mapping, [0, 0, 350]), [0.0, -1.0, 0.0]);
+    }
 
-        let mut physical_roll = before;
-        navigate(&mut physical_roll, mapping.apply(Axes { translation: [0; 3], rotation: [0, 350, 0] }), 0.02, 600.0, false, false);
-        assert_eq!((physical_roll.yaw, physical_roll.pitch), (before.yaw, before.pitch));
-        assert_ne!(physical_roll.roll, before.roll);
+    #[test]
+    fn each_frame_hands_the_view_its_motion_through_the_drivers_mapping() {
+        // The reader's latest tilt, and a profile that makes tilt roll: the frame's motion rolls.
+        let now = Instant::now();
+        let mut reading = Reading::new(now);
+        reading.axes.rotation = [0, 350, 0];
+        let mut mouse = SpaceMouse {
+            shared: Arc::new(Mutex::new(reading)),
+            last_frame: now - Duration::from_millis(20),
+            driver_mapping: DriverMapping::object_mode(),
+            mapping_checked_at: now,
+            wheel: WheelGuard::default(),
+            started: now,
+        };
+        let mut app = SolveApp::new(solidcraft_engine::Session::default(), solidcraft_ui_egui::Services::default());
+        app.home.open = false;
+        mouse.tick(&mut app, &Context::default());
+        let DeviceMotion { motion, seconds } = app.viewport.device_motion.expect("the frame hands the page its motion");
+        assert_eq!(motion, Motion { translation: [0.0; 3], rotation: [0.0, 0.0, -1.0] });
+        assert!(seconds > 0.0);
+    }
 
-        let mut physical_spin = before;
-        navigate(&mut physical_spin, mapping.apply(Axes { translation: [0; 3], rotation: [0, 0, 350] }), 0.02, 600.0, false, false);
-        assert_ne!(physical_spin.yaw, before.yaw);
-        assert_eq!((physical_spin.pitch, physical_spin.roll), (before.pitch, before.roll));
+    fn wheel() -> egui::Event {
+        egui::Event::MouseWheel {
+            unit: egui::MouseWheelUnit::Line,
+            delta: egui::vec2(0.0, -1.0),
+            modifiers: Default::default(),
+            phase: egui::TouchPhase::Move,
+        }
+    }
+
+    fn mouse(reading: Reading) -> SpaceMouse {
+        let now = Instant::now();
+        SpaceMouse {
+            shared: Arc::new(Mutex::new(reading)),
+            last_frame: now,
+            driver_mapping: DriverMapping::object_mode(),
+            mapping_checked_at: now,
+            wheel: WheelGuard::default(),
+            started: now,
+        }
+    }
+
+    #[test]
+    fn the_wheel_3dxware_makes_from_the_cap_is_dropped() {
+        // The cap tilted forward: 3DxWare also sends wheel turns (#1380). They are dropped.
+        let now = Instant::now();
+        let mut tilted = Reading::new(now);
+        tilted.axes.rotation = [-200, 0, 0];
+        let mut moving = mouse(tilted);
+        let mut raw = egui::RawInput { events: vec![wheel(), egui::Event::Zoom(1.1), egui::Event::Text("a".into())], ..Default::default() };
+        moving.raw_input_hook(true, &mut raw);
+        assert_eq!(raw.events, [egui::Event::Text("a".into())]);
+        // With navigation off, the wheel is the cap's only way to move the view: kept.
+        let mut raw = egui::RawInput { events: vec![wheel()], ..Default::default() };
+        moving.raw_input_hook(false, &mut raw);
+        assert_eq!(raw.events.len(), 1);
+        // The cap at rest: the wheel is the user's.
+        let mut resting = mouse(Reading::new(now));
+        let mut raw = egui::RawInput { events: vec![wheel()], ..Default::default() };
+        resting.raw_input_hook(true, &mut raw);
+        assert_eq!(raw.events.len(), 1);
+    }
+
+    #[test]
+    fn the_wheel_is_the_users_again_once_the_cap_has_been_still_a_moment() {
+        let mut tilted = Reading::new(Instant::now());
+        tilted.axes.rotation = [-200, 0, 0];
+        let mut cap = mouse(tilted);
+        let mut raw = egui::RawInput { events: vec![wheel()], ..Default::default() };
+        cap.raw_input_hook(true, &mut raw);
+        assert!(raw.events.is_empty(), "dropped while the cap moves");
+        // Let go, then wait out the quiet time.
+        if let Ok(mut reading) = cap.shared.lock() {
+            *reading = Reading::new(Instant::now());
+        }
+        std::thread::sleep(Duration::from_secs_f64(solidcraft_ui_egui::space_mouse::WHEEL_QUIET_S) + Duration::from_millis(60));
+        let mut raw = egui::RawInput { events: vec![wheel()], ..Default::default() };
+        cap.raw_input_hook(true, &mut raw);
+        assert_eq!(raw.events.len(), 1, "kept once the cap has been still");
     }
 }

assets/README.md

@@ -75,7 +75,7 @@ The CLI still supports arbitrary PNG/ICO exports with `solidcraft-cli icon`.
 | Linux, Nix, deb/rpm, tar, Flatpak, Snap | Copy canonical hicolor images; icon name stays `ai.storyteller.solidcraft` |
 | AppImage | Uses the Linux 256 px image and `.DirIcon` alias |
 | FreeBSD | Shares Linux hicolor images and freedesktop metadata |
-| Web | HTML/Trunk stays in `apps/solidcraft-web/`; copies Japanese font/licence to `fonts/` and uses the collected CSS; no favicon/PWA icon currently exists |
+| Web | HTML/Trunk and `manifest.webmanifest` stay in `apps/solidcraft-web/`; copies Japanese font/licence to `fonts/`, uses the collected CSS, and copies the Linux 32/256/512 px images to `icons/` for the favicon and installed app |
 | Docs and link previews | `xtask book` copies the shared card to the existing `/solidcraft/og.png` public path |
 
 ## Code and provenance

assets/icons/ui/source/icons.rs

@@ -21,6 +21,19 @@ fn ellipse(x: f32, y: f32, rx: f32, ry: f32, a0: f32, a1: f32, n: usize) -> Vec<
     (0..=n).map(|i| a0 + (a1 - a0) * i as f32 / n as f32).map(|a| (x + rx * a.cos(), y + ry * a.sin())).collect()
 }
 
+/// A gear's toothed outline about (x, y): `n` teeth from the root radius `root` out to `tip`,
+/// turned by `phase` radians.
+fn teeth(x: f32, y: f32, root: f32, tip: f32, n: usize, phase: f32) -> Vec<(f32, f32)> {
+    let step = std::f32::consts::TAU / n as f32;
+    let at = |a: f32, r: f32| (x + r * a.cos(), y - r * a.sin());
+    (0..n)
+        .flat_map(|k| {
+            let a = phase + step * k as f32;
+            [at(a - 0.3 * step, root), at(a - 0.15 * step, tip), at(a + 0.15 * step, tip), at(a + 0.3 * step, root)]
+        })
+        .collect()
+}
+
 struct Pen<'a> {
     p: &'a Painter,
     r: Rect,
@@ -271,6 +284,13 @@ pub(crate) fn paint_with(p: &Painter, r: Rect, name: &str, ink: Color32, fill: C
             pen.line(&[(7.5, 10.0), (12.0, 14.5), (16.5, 10.0)], ink);
             pen.line(&[(4.0, 15.0), (4.0, 20.0), (20.0, 20.0), (20.0, 15.0)], ink);
         }
+        // Agent chat: a speech bubble with three dots.
+        "agent_chat" => {
+            pen.closed(&[(4.0, 5.0), (20.0, 5.0), (20.0, 16.0), (11.0, 16.0), (6.5, 20.0), (7.5, 16.0), (4.0, 16.0)], ink);
+            for x in [8.5, 12.0, 15.5] {
+                pen.dot(x, 10.5, ink);
+            }
+        }
         // Help: a question mark in a ring.
         "help" => {
             pen.circle(12.0, 12.0, 9.0, Color32::TRANSPARENT, ink);
@@ -470,6 +490,23 @@ pub(crate) fn paint_with(p: &Painter, r: Rect, name: &str, ink: Color32, fill: C
             }
             p.circle_filled(at(0.5), dot_r, a);
         }
+        "infinite" => {
+            // An infinite line (#1359): Construction's broken line, with an open arrowhead at
+            // each end saying it runs on. Accent only, like Construction and Centerline.
+            let w = line_type_stroke(r);
+            let at = |t: f32| pen.at(3.0 + 16.0 * t, 19.0 - 16.0 * t);
+            for (t0, t1) in [(0.0, 0.38), (0.62, 1.0)] {
+                p.add(Shape::line(vec![at(t0), at(t1)], Stroke::new(w, a)));
+            }
+            // Each head: two short strokes back from the tip, either side of the line.
+            let tip_len = 0.3;
+            for (tip, back) in [(0.0f32, tip_len), (1.0, 1.0 - tip_len)] {
+                let (t, b) = (at(tip), at(back));
+                let along = b - t;
+                let side = egui::vec2(-along.y, along.x) * 0.55;
+                p.add(Shape::line(vec![b + side, t, b - side], Stroke::new(w, a)));
+            }
+        }
         "c_hv" => {
             pen.line(&[(4.0, 18.0), (20.0, 18.0)], a);
             pen.line(&[(6.0, 4.0), (6.0, 14.0)], a);
@@ -725,6 +762,20 @@ pub(crate) fn paint_with(p: &Painter, r: Rect, name: &str, ink: Color32, fill: C
             pen.closed(&[(21.0, 6.0), (15.0, 10.0), (15.0, 18.0), (21.0, 18.0)], a);
         }
         "sketch_circ_pattern" => paint(p, r, "pattern_circ", ink, Color32::TRANSPARENT, a),
+        "pattern_flip" => {
+            // Opposing arrows show reversal, with a short reference tick between them.
+            pen.arrow((4.0, 7.0), (20.0, 7.0), a);
+            pen.arrow((20.0, 17.0), (4.0, 17.0), ink);
+            pen.line(&[(12.0, 10.0), (12.0, 14.0)], ink);
+        }
+        "pattern_center" => {
+            // An original on a reference axis, with one equally spaced copy on either side.
+            pen.line(&[(12.0, 3.0), (12.0, 21.0)], a);
+            pen.line(&[(4.0, 12.0), (20.0, 12.0)], ink);
+            for x in [4.0, 12.0, 20.0] {
+                pen.circle(x, 12.0, 2.4, fill, if x == 12.0 { a } else { ink });
+            }
+        }
         "sketch_rect_pattern" => paint(p, r, "pattern_rect", ink, Color32::TRANSPARENT, a),
         "line_mid" => {
             pen.line(&[(3.0, 19.0), (21.0, 5.0)], a);
@@ -1242,6 +1293,14 @@ pub(crate) fn paint_with(p: &Painter, r: Rect, name: &str, ink: Color32, fill: C
             pen.arc(12.0, 12.0, 8.5, 0.3, 4.6, a);
             pen.arrow((11.0, 20.4), (14.5, 20.3), a);
         }
+        // A crank on its pivot and the closed path its far end draws (accent).
+        "trace" => {
+            pen.curve([(15.0, 13.0), (22.0, 13.0), (23.0, 3.0), (15.0, 3.0)], a);
+            pen.curve([(15.0, 3.0), (8.0, 3.0), (9.0, 13.0), (15.0, 13.0)], a);
+            pen.line(&[(5.0, 20.0), (15.0, 13.0)], ink);
+            pen.circle(5.0, 20.0, 2.4, pen.fill, ink);
+            pen.dot(15.0, 13.0, a);
+        }
         "motion_link" => {
             pen.circle(7.0, 14.0, 4.5, pen.fill, ink);
             pen.circle(17.5, 9.0, 3.0, pen.fill, ink);
@@ -1249,6 +1308,36 @@ pub(crate) fn paint_with(p: &Painter, r: Rect, name: &str, ink: Color32, fill: C
             pen.dot(7.0, 14.0, a);
             pen.dot(17.5, 9.0, a);
         }
+        // Couplings: the driven part in the accent.
+        "gear" => {
+            pen.circle(9.0, 14.0, 5.2, pen.fill, Color32::TRANSPARENT);
+            pen.closed(&teeth(9.0, 14.0, 5.2, 6.8, 9, 0.0), ink);
+            pen.dot(9.0, 14.0, ink);
+            pen.circle(17.6, 7.4, 3.2, pen.fill, Color32::TRANSPARENT);
+            pen.closed(&teeth(17.6, 7.4, 3.2, 4.6, 6, 0.3), a);
+            pen.dot(17.6, 7.4, a);
+        }
+        "rack_pinion" => {
+            pen.circle(12.0, 7.4, 4.2, pen.fill, Color32::TRANSPARENT);
+            pen.closed(&teeth(12.0, 7.4, 4.2, 5.8, 8, 0.2), ink);
+            pen.dot(12.0, 7.4, ink);
+            let mut rack = vec![(2.0, 18.0)];
+            for k in 0..5 {
+                let x = 2.5 + 4.0 * k as f32;
+                rack.extend([(x, 14.3), (x + 1.0, 12.8), (x + 2.2, 12.8), (x + 3.2, 14.3)]);
+            }
+            rack.extend([(22.0, 14.3), (22.0, 18.0)]);
+            pen.closed(&rack, a);
+            pen.arrow((7.0, 21.5), (17.5, 21.5), a);
+        }
+        "screw" => {
+            pen.poly(&[(9.5, 2.0), (14.5, 2.0), (14.5, 22.0), (9.5, 22.0)], pen.fill, ink);
+            for y in [5.0, 8.0, 17.0, 20.0] {
+                pen.line(&[(9.5, y), (14.5, y - 2.0)], ink);
+            }
+            pen.poly(&[(6.0, 10.0), (18.0, 10.0), (18.0, 15.0), (6.0, 15.0)], pen.fill, a);
+            pen.arrow((21.0, 17.0), (21.0, 6.0), a);
+        }
         "interference" => {
             pen.closed(&[(3.0, 5.0), (14.0, 5.0), (14.0, 16.0), (3.0, 16.0)], ink);
             pen.poly(&[(9.0, 10.0), (14.0, 10.0), (14.0, 16.0), (9.0, 16.0)], ic.interference, ic.interference);
@@ -1432,7 +1521,7 @@ mod tests {
     /// theme's construction orange) and must not change with `ink`.
     #[test]
     fn construction_and_centerline_icons_follow_the_callers_accent_only() {
-        for name in ["construction", "centerline"] {
+        for name in ["construction", "centerline", "infinite"] {
             let base = drawn(name, Color32::BLACK, Color32::WHITE, Color32::from_rgb(1, 2, 3));
             let other_accent = drawn(name, Color32::BLACK, Color32::WHITE, Color32::from_rgb(4, 5, 6));
             assert_ne!(base, other_accent, "{name} icon must change with the caller's accent colour");

assets/styles/ui/palettes.rs

@@ -93,12 +93,7 @@ impl Tokens {
             bend_up: Color32::from_rgb(30, 140, 50),
             bend_down: Color32::from_rgb(200, 90, 20),
             interference: Color32::from_rgb(235, 45, 40),
-            analysis: AnalysisColors {
-                draft: [[0.20, 0.75, 0.30], [0.95, 0.80, 0.15], [0.85, 0.22, 0.20]],
-                access: [[0.20, 0.75, 0.30], [0.85, 0.22, 0.20]],
-                curvature: [[0.15, 0.35, 0.95], [0.10, 0.80, 0.25], [0.90, 0.15, 0.10]],
-                hatch: false,
-            },
+            analysis: AnalysisColors::DEFAULT,
             icons: IconColors {
                 sheet: Color32::from_rgb(170, 200, 240),
                 sheet_2: Color32::from_rgb(150, 185, 235),

crates/derive/src/lib.rs

@@ -10,16 +10,17 @@
 //!
 //! What a field is, is written once, on the field, with `#[walk(...)]`:
 //!
-//! - no attribute: the field's own type walks itself (`impl Walk`): a plane, a nested struct, a
-//!   list of them, or nothing for names, flags and numbers. A bare `Vec3` has no walk, so a point
-//!   that does not say its role does not compile;
-//! - `length = label`, `angle = label`, `unitless = label`: an expression input (a `String`, an
-//!   optional one, a list or an array of them, or `(f64, String)` pairs). The label is any
+//! - no attribute: the field's own type walks itself (`impl Walk`): a reference (`SketchId`,
+//!   `BodyName`, `FeatureName`), a point with its role (`FacePick`, `Position`, `Dir`), a plane, a
+//!   nested struct, a list of them, or nothing for names, flags and numbers. An `Expr` or a bare
+//!   `Vec3` has no walk, so an expression or a point that does not say what it is does not
+//!   compile;
+//! - `length = label`, `angle = label`, `unitless = label`: an expression input (an `Expr`, an
+//!   optional one, a list or an array of them, or `(f64, Expr)` pairs). The label is any
 //!   expression: a `&'static str`, an array of them (one per element), or a closure
 //!   `|i: usize, n: usize| -> &'static str`; it may read the other fields;
-//! - `sketch`, `feature`, `body`: a reference (an id, or a name, optional or a list);
-//! - `pick`, `pinned`, `pos`, `dir`: a point (`Vec3`, optional or a list) with that role;
-//!   `pick_if = cond`: a pick when `cond` holds, else a position;
+//! - `pinned`: a face pick that stays where it is when the feature moves;
+//!   `pick_if = cond`: a face pick when `cond` holds, else a position;
 //! - `placement`: a primitive's placement point (its X, Y and Z expressions are not inputs);
 //! - `profiles_of = sketch_field`, optionally with `when = cond`: a profile selection;
 //! - `after = field`: visit this field right after `field` instead of in declaration order (where
@@ -60,8 +61,6 @@ struct Roles {
     geo: Option<Geo>,
     /// The kind (`Length`, `Angle`, `Unitless`) and the label.
     expr: Option<(&'static str, Expr)>,
-    /// `Sketch`, `Feature` or `Body`.
-    reference: Option<&'static str>,
     after: Option<Ident>,
     /// The positions inside this (nested) value pick faces here.
     picks_faces: bool,
@@ -70,7 +69,7 @@ struct Roles {
 impl Roles {
     /// No role given: the field's type walks itself.
     fn nested(&self) -> bool {
-        self.geo.is_none() && self.expr.is_none() && self.reference.is_none()
+        self.geo.is_none() && self.expr.is_none()
     }
 }
 
@@ -82,10 +81,7 @@ fn roles(field: &syn::Field) -> syn::Result<Roles> {
         attr.parse_nested_meta(|meta| {
             let name = meta.path.get_ident().map(Ident::to_string).unwrap_or_default();
             match name.as_str() {
-                "pick" => r.geo = Some(Geo::Points("Pick")),
                 "pinned" => r.geo = Some(Geo::Points("Pinned")),
-                "pos" => r.geo = Some(Geo::Points("Pos")),
-                "dir" => r.geo = Some(Geo::Points("Dir")),
                 "placement" => r.geo = Some(Geo::Placement),
                 "pick_if" => r.geo = Some(Geo::PickIf(meta.value()?.parse()?)),
                 "profiles_of" => sketch = Some(meta.value()?.parse::<Ident>()?),
@@ -93,9 +89,6 @@ fn roles(field: &syn::Field) -> syn::Result<Roles> {
                 "length" => r.expr = Some(("Length", meta.value()?.parse()?)),
                 "angle" => r.expr = Some(("Angle", meta.value()?.parse()?)),
                 "unitless" => r.expr = Some(("Unitless", meta.value()?.parse()?)),
-                "sketch" => r.reference = Some("Sketch"),
-                "feature" => r.reference = Some("Feature"),
-                "body" => r.reference = Some("Body"),
                 "after" => r.after = Some(meta.value()?.parse()?),
                 "picks_faces" => r.picks_faces = true,
                 _ => return Err(meta.error("unknown walk role")),
@@ -157,14 +150,7 @@ fn walk_field(b: &Ident, r: &Roles, which: Which, mutable: bool) -> Tokens {
                 _ => quote!(),
             }
         }
-        Which::Refs => match r.reference {
-            Some(kind) => {
-                let t = if kind == "Sketch" { quote!(u64) } else { quote!(String) };
-                let kind = Ident::new(kind, Span::call_site());
-                quote! { #w::Each::<#t>::#each(#b, &mut |x| f(#w::Ref::#kind(x))); }
-            }
-            None => quote!(),
-        },
+        Which::Refs => quote!(),
         Which::Geometry => match &r.geo {
             Some(Geo::Points(v)) => {
                 let v = Ident::new(v, Span::call_site());
@@ -209,7 +195,7 @@ fn pre_values(b: &Ident, r: &Roles, which: Which) -> Tokens {
             quote! {
                 let #wh: bool = #when;
                 let mut #id: Option<u64> = None;
-                #w::Each::<u64>::each(&*#sketch, &mut |s| #id = Some(*s));
+                #w::Each::<crate::SketchId>::each(&*#sketch, &mut |s| #id = Some(s.0));
             }
         }
         _ => quote!(),

crates/doc/build.rs

@@ -0,0 +1,62 @@
+//! Lists the design-format changes in `src/format/`: one file per change, in `v<N>/` once a
+//! release fixed its number, else in `pending/` (see `src/format/pending/README.md`). The list is
+//! generated so that a change adds a file and never edits a line another change also edits.
+
+use std::fmt::Write as _;
+use std::path::{Path, PathBuf};
+
+/// The last format whose upgrade steps are written out in `format.rs` (`JSON_STEPS`).
+const HAND_WRITTEN: u32 = 22;
+
+fn main() {
+    let root = PathBuf::from(std::env::var("CARGO_MANIFEST_DIR").unwrap()).join("src/format");
+    println!("cargo:rerun-if-changed={}", root.display());
+    let mut folded: Vec<(u32, PathBuf)> = std::fs::read_dir(&root)
+        .unwrap_or_else(|e| panic!("{}: {e}", root.display()))
+        .filter_map(|entry| {
+            let path = entry.ok()?.path();
+            let version = path.file_name()?.to_str()?.strip_prefix('v')?.parse().ok()?;
+            path.is_dir().then_some((version, path))
+        })
+        .collect();
+    folded.sort();
+    for (i, (version, _)) in folded.iter().enumerate() {
+        let expected = HAND_WRITTEN + 1 + i as u32;
+        assert_eq!(*version, expected, "src/format/: expected v{expected}/ next, found v{version}/ (versions are contiguous)");
+    }
+    let mut out = String::new();
+    let mut mods = String::new();
+    out.push_str("/// The changes of each format after the hand-written ones, oldest first.\nconst FOLDED: &[(u32, &[Part])] = &[\n");
+    for (version, dir) in &folded {
+        let _ = writeln!(out, "    ({version}, &[");
+        parts(dir, &format!("v{version}"), &mut out, &mut mods);
+        out.push_str("    ]),\n");
+    }
+    out.push_str("];\n\n/// The changes no release has a number for yet (`src/format/pending/`).\nconst PENDING: &[Part] = &[\n");
+    parts(&root.join("pending"), "pending", &mut out, &mut mods);
+    out.push_str("];\n");
+    out.push_str(&mods);
+    let dest = PathBuf::from(std::env::var("OUT_DIR").unwrap()).join("format_parts.rs");
+    std::fs::write(dest, out).unwrap();
+}
+
+/// The `Part`s of the change files in `dir`, in file-name order, and a module for each.
+fn parts(dir: &Path, prefix: &str, out: &mut String, mods: &mut String) {
+    let Ok(entries) = std::fs::read_dir(dir) else { return };
+    let mut files: Vec<PathBuf> = entries.filter_map(|e| e.ok().map(|e| e.path())).filter(|p| p.extension().is_some_and(|x| x == "rs")).collect();
+    files.sort();
+    for path in files {
+        let name = path.file_stem().and_then(|s| s.to_str()).unwrap_or_default().to_string();
+        assert!(
+            !name.is_empty() && name.bytes().all(|b| b.is_ascii_lowercase() || b.is_ascii_digit() || b == b'-'),
+            "{}: name a format change file with lowercase letters, digits and dashes",
+            path.display()
+        );
+        let text = std::fs::read_to_string(&path).unwrap();
+        assert!(text.trim_start().starts_with("//!"), "{}: start a format change with a `//!` note", path.display());
+        let module = format!("{prefix}_{}", name.replace('-', "_"));
+        let step = if text.contains("fn step(") { format!("Some({module}::step)") } else { "None".into() };
+        let _ = writeln!(out, "        Part {{ name: {name:?}, step: {step} }},");
+        let _ = writeln!(mods, "#[path = {:?}]\nmod {module};", path.display().to_string());
+    }
+}

crates/doc/src/assembly.rs

@@ -136,11 +136,16 @@ fn map_plane(m: &Mat, p: &Plane) -> Plane {
 fn map_plane_ref(m: &Mat, p: &mut PlaneRef) {
     match p {
         PlaneRef::Custom { plane } => *plane = map_plane(m, plane),
+        PlaneRef::Placed { origin, x_dir, y_dir } => {
+            map_point_expr(m, origin);
+            *x_dir = apply_vector(m, *x_dir);
+            *y_dir = apply_vector(m, *y_dir);
+        }
         PlaneRef::Face { plane, at, .. } => {
             *plane = map_plane(m, plane);
             *at = apply_point(m, *at);
         }
-        PlaneRef::Offset { base, .. } => map_plane_ref(m, base),
+        PlaneRef::Offset { base, .. } | PlaneRef::Flipped { base, .. } => map_plane_ref(m, base),
         PlaneRef::AtAngle { base, axis_origin, axis_dir, .. } => {
             map_plane_ref(m, base);
             *axis_origin = apply_point(m, *axis_origin);
@@ -171,7 +176,7 @@ fn map_geo_ref(m: &Mat, g: &mut crate::construct::GeoRef) {
 /// Map a point given as expressions by `m`: numbers stay numbers; a coordinate that is an
 /// expression stays one (`m · (x, y, z) + t`, written out), so it still follows its parameters.
 pub fn map_point_expr(m: &Mat, p: &mut crate::PointExpr) {
-    let num = |e: &String| e.trim().parse::<f64>().ok().filter(|v| v.is_finite());
+    let num = |e: &crate::Expr| e.trim().parse::<f64>().ok().filter(|v| v.is_finite());
     if let [Some(x), Some(y), Some(z)] = [num(&p[0]), num(&p[1]), num(&p[2])] {
         *p = crate::point_expr(apply_point(m, Vec3::new(x, y, z)));
         return;
@@ -197,7 +202,7 @@ pub fn map_point_expr(m: &Mat, p: &mut crate::PointExpr) {
         } else if constant.abs() >= 1e-12 {
             e = format!("{e} {} {} mm", if constant < 0.0 { '-' } else { '+' }, constant.abs());
         }
-        *out = e;
+        *out = e.into();
     }
 }
 

crates/doc/src/body_transfer.rs

@@ -78,7 +78,13 @@ mod tests {
             (vec!["bad\nname".into()], 0, crate::IDENTITY),
             (vec!["Block".into()], 0, scaled),
         ] {
-            assert!(doc.add_feature(crate::FeatureKind::BodyTransfer { bodies, from, to: 0, transform }, None).is_err());
+            assert!(
+                doc.add_feature(
+                    crate::FeatureKind::BodyTransfer { bodies: bodies.into_iter().map(crate::BodyName).collect(), from, to: 0, transform },
+                    None
+                )
+                .is_err()
+            );
             assert_eq!(doc.to_json(), before);
         }
     }

crates/doc/src/clipboard.rs

@@ -113,8 +113,10 @@ fn remap_plane(
         return Err(crate::DocError::Invalid("clone plane reference depth exceeded".into()));
     }
     match p {
-        PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } => remap_plane(base, ids, names, bodies, depth + 1)?,
-        PlaneRef::Construction { name } => mapped_name(name, names),
+        PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } | PlaneRef::Flipped { base, .. } => {
+            remap_plane(base, ids, names, bodies, depth + 1)?
+        }
+        PlaneRef::Construction { name } => mapped_name(&mut name.0, names),
         PlaneRef::Face { name, anchor, .. } => {
             if let Some(name) = name {
                 *name = remap_topology(name, ids, bodies);
@@ -221,10 +223,10 @@ impl crate::Feature {
             *n = remap_topology(n, ids, bodies);
         }
         for (_, e, _) in self.kind.inputs_mut() {
-            *e = clone_expression(e, parameters);
+            *e = clone_expression(e, parameters).into();
         }
-        for e in self.kind.point_expr_mut().into_iter().flatten() {
-            *e = clone_expression(e, parameters);
+        for e in self.kind.placement_exprs_mut() {
+            *e = clone_expression(e, parameters).into();
         }
         self.kind.remap_bodies(bodies);
         match &mut self.kind {
@@ -235,6 +237,9 @@ impl crate::Feature {
                         mapped_name(n, parameters);
                     }
                 }
+                for e in sketch.text_exprs_mut() {
+                    *e = clone_expression(e, parameters);
+                }
                 for link in &mut sketch.links {
                     remap_link(&mut link.source, ids, names, bodies, 0);
                     for n in link.face_name.iter_mut().chain(&mut link.edge_name) {
@@ -280,7 +285,7 @@ fn checked_plane(p: &PlaneRef, depth: usize) -> crate::Result<()> {
         return Err(crate::DocError::Invalid("copy reference nesting exceeds 64".into()));
     }
     match p {
-        PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } => checked_plane(base, depth + 1)?,
+        PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } | PlaneRef::Flipped { base, .. } => checked_plane(base, depth + 1)?,
         PlaneRef::Midplane { a, b } | PlaneRef::TwoEdges { a, b } => {
             checked_geo(a, depth + 1)?;
             checked_geo(b, depth + 1)?;

crates/doc/src/config_certificates.rs

@@ -148,6 +148,35 @@ pub(crate) fn extrude_cap_bindings(sketch: &SolvedSketch, bodies: &[solidcraft_k
     Some(bindings)
 }
 
+/// Cap signatures for a thin extrude (#1519). A thin wall's caps are bounded by offset curves
+/// the sketch doesn't have, so [`extrude_cap_bindings`] can never certify them. A wall built
+/// from one region is signed by the curves it follows instead: the cap of this extrude whose
+/// wall runs along them. That is the signature its solid caps had when the wall follows the
+/// whole profile (a rectangle's four lines), so a sketch attached to a solid cap keeps its face
+/// when the extrude is made thin, and the other way round. Several regions (walls apart, or one
+/// meeting itself) are left uncertified: they keep their history names.
+pub(crate) fn thin_extrude_cap_bindings(curves: &[String], regions: usize, bodies: &[solidcraft_kernel::Body]) -> CapBindings {
+    use solidcraft_kernel::FaceSource;
+    let mut outer = curves.to_vec();
+    outer.sort();
+    outer.dedup();
+    let signed = regions == 1 && bodies.len() == 1 && valid_signature(&outer, &[]);
+    bodies
+        .iter()
+        .map(|body| {
+            let sources: Vec<_> = body.face_sources().into_iter().flatten().collect();
+            let ends =
+                |high: bool| sources.iter().filter(|source| matches!(source, Some(FaceSource::ExtrudeCap { high: h, .. }) if *h == high)).count();
+            // One cap at each end, or none of them is certified.
+            let unique = ends(true) <= 1 && ends(false) <= 1;
+            sources
+                .iter()
+                .map(|source| (signed && unique && matches!(source, Some(FaceSource::ExtrudeCap { .. }))).then(|| (outer.clone(), Vec::new())))
+                .collect()
+        })
+        .collect()
+}
+
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(tag = "kind", rename_all = "snake_case", deny_unknown_fields)]
 pub enum FaceCertificate {

crates/doc/src/config_shell_tests.rs

@@ -17,7 +17,7 @@ fn shell_document() -> (Document, u64, u64) {
     let shell = doc
         .add_feature(
             FeatureKind::Shell {
-                faces: vec![Vec3::new(5., 6., 10.)],
+                faces: vec![crate::FacePick(Vec3::new(5., 6., 10.))],
                 thickness: "wall".into(),
                 body: Some("Case".into()),
                 direction: "inside".into(),
@@ -119,7 +119,7 @@ fn shell_planar_anchor_rebuild_cold_geometry_and_missing_source_errors() {
         .add_feature(
             FeatureKind::Extrude {
                 thin: None,
-                sketch: sk,
+                sketch: crate::SketchId(sk),
                 profiles: crate::ProfileSel::All,
                 extent: serde_json::from_value(json!({"distance":"2"})).unwrap(),
                 operation: crate::Operation::NewBody,
@@ -282,7 +282,7 @@ fn saved_former_strip_projection_reports_lost_without_expanding_healthy_material
         .add_feature(
             FeatureKind::Extrude {
                 thin: None,
-                sketch: sk,
+                sketch: crate::SketchId(sk),
                 profiles: crate::ProfileSel::All,
                 extent: serde_json::from_value(json!({"distance":"1"})).unwrap(),
                 operation: crate::Operation::NewBody,
@@ -344,7 +344,7 @@ fn saved_curved_strip_projection_is_lost_after_exact_wall_coalescence() {
     let shell = doc
         .add_feature(
             FeatureKind::Shell {
-                faces: vec![Vec3::new(0., 0., 30.)],
+                faces: vec![crate::FacePick(Vec3::new(0., 0., 30.))],
                 thickness: "wall".into(),
                 body: Some("Case".into()),
                 direction: "inside".into(),
@@ -432,7 +432,7 @@ fn saved_curved_strip_projection_is_lost_after_exact_wall_coalescence() {
         .add_feature(
             FeatureKind::Extrude {
                 thin: None,
-                sketch: sk,
+                sketch: crate::SketchId(sk),
                 profiles: crate::ProfileSel::All,
                 extent: serde_json::from_value(json!({"distance":"1"})).unwrap(),
                 operation: crate::Operation::NewBody,
@@ -557,7 +557,7 @@ fn saved_stepped_tab_cut_piece_projection_is_lost_without_expanding_material() {
         .add_feature(
             FeatureKind::Extrude {
                 thin: None,
-                sketch: sk,
+                sketch: crate::SketchId(sk),
                 profiles: crate::ProfileSel::All,
                 extent: serde_json::from_value(json!({"distance":"1"})).unwrap(),
                 operation: crate::Operation::NewBody,

crates/doc/src/construct.rs

@@ -82,7 +82,7 @@ pub enum PointDef {
     /// Where an edge (line) crosses a plane.
     EdgeAndPlane { edge: GeoRef, plane: GeoRef },
     /// At a fraction `t` (0…1) of the way along an edge or sketch curve.
-    AlongPath { path: GeoRef, t: String },
+    AlongPath { path: GeoRef, t: crate::Expr },
 }
 
 /// Resolved construction geometry, kept in the model state by feature.
@@ -633,7 +633,7 @@ impl PlaneRef {
             PlaneRef::ThreePoints { a, b, c } => vec![a.as_mut(), b.as_mut(), c.as_mut()],
             PlaneRef::Tangent { face, .. } => vec![face.as_mut()],
             PlaneRef::AlongPath { path, .. } => vec![path.as_mut()],
-            PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } => base.refs_mut(),
+            PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } | PlaneRef::Flipped { base, .. } => base.refs_mut(),
             _ => Vec::new(),
         }
     }

crates/doc/src/display_quality.rs

@@ -77,6 +77,57 @@ impl DisplayQuality {
     }
 }
 
+/// Most refinement steps view-dependent display refinement takes past the chosen level (#1320):
+/// each halves the chord tolerance, so the finest is 1/16 of the chosen level's.
+pub const MAX_REFINE: u8 = 4;
+
+/// Screen-space error (physical pixels) above which a body is refined: a facet's sag shows.
+pub const REFINE_PX: f64 = 1.0;
+/// Error a refinement aims for (below [`REFINE_PX`], so a body just refined is not refined again
+/// at the next small zoom step).
+pub const TARGET_PX: f64 = 0.75;
+/// Error below which a refined body steps back toward the chosen level. A refinement lands
+/// between half [`TARGET_PX`] and [`TARGET_PX`], and a step back between this and twice this, so
+/// zooming out or in by up to 2× from either never flips the level back.
+pub const COARSEN_PX: f64 = 0.175;
+
+impl DisplayQuality {
+    /// Chord tolerance (mm) of a body of this size refined `k` steps past this level: halved
+    /// per step.
+    pub fn refined_chord(self, size: f64, k: u8) -> f64 {
+        self.chord(size) / f64::from(1u32 << k.min(MAX_REFINE))
+    }
+
+    /// Facet angle (radians) `k` steps past this level: an arc's sag goes with the square of its
+    /// angle, so the angle shrinks by √2 per step, keeping pace with the chord.
+    pub fn refined_angle(self, k: u8) -> f64 {
+        self.angle() / std::f64::consts::SQRT_2.powi(i32::from(k.min(MAX_REFINE)))
+    }
+}
+
+/// The refinement step a body should be drawn at (0: the chosen level), from `err_px`: the
+/// screen-space error of the chosen level, its chord tolerance in physical pixels where the body
+/// is nearest the eye (0 for a body off screen or too small to matter). `current` is the step
+/// drawn now; steps halve the error. A body is refined once its error passes [`REFINE_PX`], to the
+/// first step under [`TARGET_PX`], and steps back only once the error falls under [`COARSEN_PX`],
+/// to the coarsest step that stays under twice that: the band between keeps an orbit or a small
+/// zoom from flipping levels. Never past `max` (at most [`MAX_REFINE`]).
+pub fn refinement_for(err_px: f64, current: u8, max: u8) -> u8 {
+    let max = max.min(MAX_REFINE);
+    let current = current.min(max);
+    if !(err_px.is_finite() && err_px > 0.0) {
+        return 0;
+    }
+    let err = |k: u8| err_px / f64::from(1u32 << k);
+    if err(current) > REFINE_PX {
+        (current..=max).find(|&k| err(k) <= TARGET_PX).unwrap_or(max)
+    } else if err(current) < COARSEN_PX {
+        (0..=current).find(|&k| err(k) <= 2.0 * COARSEN_PX).unwrap_or(current)
+    } else {
+        current
+    }
+}
+
 static CURRENT: AtomicU8 = AtomicU8::new(1);
 
 /// The level the viewport draws at (process-wide; set from the preferences).
@@ -140,4 +191,58 @@ mod tests {
             plan.vertex_count()
         });
     }
+
+    #[test]
+    fn refinement_follows_the_screen_space_error_with_hysteresis() {
+        // Off screen or tiny: the chosen level.
+        assert_eq!(refinement_for(0.0, 3, MAX_REFINE), 0);
+        assert_eq!(refinement_for(f64::NAN, 2, MAX_REFINE), 0);
+        // Fine already: stays.
+        assert_eq!(refinement_for(0.6, 0, MAX_REFINE), 0);
+        assert_eq!(refinement_for(1.0, 0, MAX_REFINE), 0);
+        // Past a pixel: the first step under the target (each halves the error).
+        assert_eq!(refinement_for(1.2, 0, MAX_REFINE), 1);
+        assert_eq!(refinement_for(5.0, 0, MAX_REFINE), 3);
+        assert_eq!(refinement_for(5.0, 1, MAX_REFINE), 3);
+        // Capped.
+        assert_eq!(refinement_for(1e6, 0, MAX_REFINE), MAX_REFINE);
+        assert_eq!(refinement_for(1e6, 0, 2), 2);
+        assert_eq!(refinement_for(1e6, 9, 99), MAX_REFINE);
+        // Zooming back out: kept until the error is well under a pixel, then the coarsest step
+        // that stays under half a pixel.
+        assert_eq!(refinement_for(5.0, 3, MAX_REFINE), 3);
+        assert_eq!(refinement_for(2.5, 3, MAX_REFINE), 3, "0.31 px at step 3: in the band");
+        assert_eq!(refinement_for(1.2, 3, MAX_REFINE), 2, "0.15 px at step 3: down to 0.3 px");
+        assert_eq!(refinement_for(0.05, 3, MAX_REFINE), 0);
+        // No flicker: any error, once settled, gives the same step again, and a zoom by up to
+        // 2x either way from where a level was chosen keeps it.
+        let mut e = 0.01;
+        while e < 1e4 {
+            for start in 0..=MAX_REFINE {
+                let k = refinement_for(e, start, MAX_REFINE);
+                assert_eq!(refinement_for(e, k, MAX_REFINE), k, "error {e}, from {start}");
+                // Settled by zooming in (from the chosen level) or out (from the finest).
+                if start == 0 || start == MAX_REFINE {
+                    for f in [0.5, 0.7, 1.0, 1.4, 2.0] {
+                        let back = refinement_for(e * f, k, MAX_REFINE);
+                        let zoomed_in = f >= 1.0;
+                        assert!(
+                            back == k || (zoomed_in && back > k && start == 0) || (!zoomed_in && back < k && start == MAX_REFINE),
+                            "error {e} x{f} from {start}: {k} -> {back}"
+                        );
+                    }
+                }
+            }
+            e *= 1.13;
+        }
+    }
+
+    #[test]
+    fn refined_steps_halve_the_chord() {
+        let q = DisplayQuality::Normal;
+        assert_eq!(q.refined_chord(200.0, 0), q.chord(200.0));
+        assert_eq!(q.refined_chord(200.0, 2), q.chord(200.0) / 4.0);
+        assert_eq!(q.refined_chord(200.0, 99), q.chord(200.0) / 16.0);
+        assert!((q.refined_angle(2) - q.angle() / 2.0).abs() < 1e-12);
+    }
 }

crates/doc/src/eval_more.rs

@@ -10,7 +10,7 @@ use solidcraft_geom::{Loop2, Seg2};
 pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature, st: &mut ModelState) -> Result<()> {
     match &f.kind {
         FeatureKind::Emboss { sketch, profiles, depth, deboss, targets, face } => {
-            let ss = st.sketch(*sketch).ok_or_else(|| DocError::Unknown(format!("sketch {sketch}")))?;
+            let ss = st.sketch(sketch.0).ok_or_else(|| DocError::Unknown(format!("sketch {sketch}")))?;
             let regions = select_profiles(ss, profiles)?;
             let d = val(vals, depth, Kind::Length)?;
             if !(d > 0.0) {
@@ -35,7 +35,7 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
                     crate::apply_vector(&sketch_transform, ss.plane.y),
                 )
                 .ok_or_else(|| DocError::Invalid("invalid cylinder sketch frame".into()))?;
-                let mut at = crate::apply_point(&crate::mat_mul(&inverse, &author_frame), face.at);
+                let mut at = crate::apply_point(&crate::mat_mul(&inverse, &author_frame), face.at.0);
                 let name = f
                     .face_names
                     .first()
@@ -67,10 +67,10 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
             if st.bodies.is_empty() {
                 return Err(DocError::Invalid("there is no body to emboss".into()));
             }
-            apply_op(st, f, tools, if *deboss { Operation::Cut } else { Operation::Join }, targets)
+            apply_op(st, f, tools, if *deboss { Operation::Cut } else { Operation::Join }, &crate::plain(targets))
         }
         FeatureKind::Rib { sketch, curves, thickness, depth, flip, web } => {
-            let ss = st.sketch(*sketch).ok_or_else(|| DocError::Unknown(format!("sketch {sketch}")))?.clone();
+            let ss = st.sketch(sketch.0).ok_or_else(|| DocError::Unknown(format!("sketch {sketch}")))?.clone();
             let t = val(vals, thickness, Kind::Length)?;
             if !(t > 0.0) {
                 return Err(DocError::Invalid("the rib thickness must be positive".into()));
@@ -95,17 +95,18 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
         FeatureKind::ReplaceFace { faces, target, body } => {
             let tp = doc.resolve_plane_in(vals, target, 0, Some(st))?;
             let tn = tp.normal();
-            let i = body_at(st, body, faces)?;
+            let i = body_at(st, body, &crate::plain(faces))?;
             let Some(mb) = st.bodies.get(i).cloned() else { return Err(DocError::Invalid("body".into())) };
             let mut b = mb.body.clone();
             for p in faces {
-                let n = planar_normal_at(&b, *p).ok_or_else(|| DocError::Invalid("not supported yet: replacing a face that is not planar".into()))?;
+                let n =
+                    planar_normal_at(&b, p.0).ok_or_else(|| DocError::Invalid("not supported yet: replacing a face that is not planar".into()))?;
                 if n.dot(tn).abs() < 1.0 - 1e-9 {
                     return Err(DocError::Invalid("not supported yet: a target that is not parallel to the face".into()));
                 }
-                let d = (tp.origin - *p).dot(n);
+                let d = (tp.origin - p.0).dot(n);
                 if d.abs() > 1e-9 {
-                    b = kernel::offset_faces(&b, &[*p], d)?;
+                    b = kernel::offset_faces(&b, &[p.0], d)?;
                 }
             }
             if let Some(slot) = st.bodies.get_mut(i) {
@@ -115,17 +116,17 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
         }
         FeatureKind::Align { bodies, from, to, from_normal, to_normal, flip } => {
             let mut m = translation(Vec3::ZERO);
-            if let (Some(a), Some(b)) = (from_normal.and_then(Vec3::normalized), to_normal.and_then(Vec3::normalized)) {
+            if let (Some(a), Some(b)) = (from_normal.and_then(|n| n.normalized()), to_normal.and_then(|n| n.normalized())) {
                 // Turn `a` onto −b (faces meet) or b (flipped), about the `from` point.
                 let want = if *flip { b } else { b * -1.0 };
                 let axis = a.cross(want);
                 let ang = axis.len().atan2(a.dot(want));
                 let axis = axis.normalized().unwrap_or_else(|| a.any_perp());
                 if ang.abs() > 1e-12 {
-                    m = rotation(*from, axis, ang);
+                    m = rotation(from.0, axis, ang);
                 }
             }
-            let d = *to - *from;
+            let d = to.0 - from.0;
             m[3][0] += d.x;
             m[3][1] += d.y;
             m[3][2] += d.z;
@@ -150,7 +151,7 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
                     return Err(DocError::Unknown(format!("body `{n}`")));
                 }
             }
-            st.bodies.retain(|b| !bodies.contains(&b.name));
+            st.bodies.retain(|b| !bodies.iter().any(|t| *t == b.name));
             Ok(())
         }
         _ => Err(DocError::Invalid(format!("{} is not evaluated here", f.name))),
@@ -331,7 +332,7 @@ fn rebuild_sheet(st: &mut ModelState, idx: usize) -> Result<()> {
 }
 
 /// The sheet a feature works on: by body name, else the one with an edge nearest the pick.
-fn sheet_for(st: &ModelState, body: &Option<String>, pick: Option<Vec3>) -> Result<usize> {
+fn sheet_for(st: &ModelState, body: &Option<crate::BodyName>, pick: Option<Vec3>) -> Result<usize> {
     if let Some(n) = body {
         return st.sheets.iter().position(|s| &s.body == n).ok_or_else(|| DocError::Invalid(format!("`{n}` is not a sheet metal body")));
     }
@@ -391,7 +392,7 @@ pub(super) fn sheet_eval(
     use crate::sheet;
     match &f.kind {
         FeatureKind::SheetBase { sketch, profiles, rule, flip } => {
-            let ss = st.sketch(*sketch).ok_or_else(|| DocError::Unknown(format!("sketch {sketch}")))?.clone();
+            let ss = st.sketch(sketch.0).ok_or_else(|| DocError::Unknown(format!("sketch {sketch}")))?.clone();
             let regions = solidcraft_sketch::merge_regions(&select_profiles(&ss, profiles)?);
             let r = doc.sheet_rule(rule.as_deref());
             let rv = doc.rule_values(vals, &r)?;
@@ -425,7 +426,7 @@ pub(super) fn sheet_eval(
             Ok(())
         }
         FeatureKind::SheetContour { sketch, curves, distance, rule, flip, reverse } => {
-            let ss = st.sketch(*sketch).ok_or_else(|| DocError::Unknown(format!("sketch {sketch}")))?.clone();
+            let ss = st.sketch(sketch.0).ok_or_else(|| DocError::Unknown(format!("sketch {sketch}")))?.clone();
             for id in curves {
                 let ci = ss.sketch.curve_index(id).ok_or_else(|| DocError::Unknown(format!("curve `{id}`")))?;
                 if !ss.sketch.segs(ci).iter().all(|s| matches!(s, Seg2::Line { .. })) {
@@ -449,8 +450,8 @@ pub(super) fn sheet_eval(
             st.sheets.push(sh);
             Ok(())
         }
-        FeatureKind::SheetFlange { edges, height, angle, radius, position, flip, body } => {
-            let i = sheet_for(st, body, edges.first().map(|e| e.point))?;
+        FeatureKind::SheetFlange { edges, height, angle, radius, position, flip, body, corner_relief_shape, corner_relief } => {
+            let i = sheet_for(st, body, edges.first().map(|e| e.point.0))?;
             let (h, a) = (val(vals, height, Kind::Length)?, val(vals, angle, Kind::Angle)?);
             // Each edge's own height and angle, else the feature's.
             let mut own = Vec::with_capacity(edges.len());
@@ -472,18 +473,32 @@ pub(super) fn sheet_eval(
                     doc.rule_values(vals, &doc.sheet_rule(Some(&rule)))?.bend_radius
                 }
             };
+            // The corner relief these flanges ask for in place of the rule's.
+            let relief = sheet::ReliefOverride {
+                shape: match corner_relief_shape {
+                    Some(name) => Some(
+                        sheet::ReliefShape::parse(name)
+                            .ok_or_else(|| DocError::Invalid(format!("unknown corner relief shape `{name}` (notch, round, rectangular or tear)")))?,
+                    ),
+                    None => None,
+                },
+                size: match corner_relief {
+                    Some(e) => Some(val(vals, e, Kind::Length)?),
+                    None => None,
+                },
+            };
             let sh = st.sheets.get_mut(i).ok_or_else(|| DocError::Invalid("sheet".into()))?;
             if sh.flat {
                 return Err(DocError::Invalid("refold the sheet before adding flanges".into()));
             }
-            let points: Vec<Vec3> = edges.iter().map(|e| e.point).collect();
+            let points: Vec<Vec3> = edges.iter().map(|e| e.point.0).collect();
             let each: Vec<sheet::EdgeFlange> = sheet_picks(sh, f, &points, warning)
                 .into_iter()
                 .zip(own)
                 .map(|(pick, (height, angle))| sheet::EdgeFlange { pick, height, angle })
                 .collect();
             let n0 = sh.flanges.len();
-            let (_, notes) = sh.add_flanges_each(&each, rr, position, *flip)?;
+            let (_, notes) = sh.add_flanges_each(&each, rr, position, *flip, relief)?;
             if !notes.is_empty() {
                 let notes = notes.join("; ");
                 *warning = Some(match warning.take() {
@@ -521,7 +536,7 @@ pub(super) fn sheet_eval(
             Ok(())
         }
         FeatureKind::SheetHem { edges, length, gap, flip, body } => {
-            let i = sheet_for(st, body, edges.first().copied())?;
+            let i = sheet_for(st, body, edges.first().copied().map(Vec3::from))?;
             let l = val(vals, length, Kind::Length)?;
             let g = match gap {
                 Some(e) => val(vals, e, Kind::Length)?,
@@ -531,7 +546,7 @@ pub(super) fn sheet_eval(
                 }
             };
             let sh = st.sheets.get_mut(i).ok_or_else(|| DocError::Invalid("sheet".into()))?;
-            let picks = sheet_picks(sh, f, edges, warning);
+            let picks = sheet_picks(sh, f, &crate::plain(edges), warning);
             let n0 = sh.flanges.len();
             for e in &picks {
                 sh.add_hem(*e, l, g, *flip)?;
@@ -543,14 +558,14 @@ pub(super) fn sheet_eval(
             // The sketch line, where it is now.
             let (a, b) = match (sketch, curve) {
                 (Some(sk), Some(c)) => {
-                    let ss = st.sketch(*sk).ok_or_else(|| DocError::Unknown(format!("sketch {sk}")))?;
+                    let ss = st.sketch(sk.0).ok_or_else(|| DocError::Unknown(format!("sketch {sk}")))?;
                     let ci = ss.sketch.curve_index(c).ok_or_else(|| DocError::Unknown(format!("curve `{c}`")))?;
                     match ss.sketch.segs(ci).as_slice() {
                         [Seg2::Line { a, b }] => (ss.plane.to_world(*a), ss.plane.to_world(*b)),
                         _ => return Err(DocError::Invalid("the fold line must be a sketch line".into())),
                     }
                 }
-                _ => (*a, *b),
+                _ => (a.0, b.0),
             };
             let i = sheet_for(st, body, Some((a + b) * 0.5))?;
             let ang = val(vals, angle, Kind::Angle)?;
@@ -564,7 +579,7 @@ pub(super) fn sheet_eval(
             // A fixed point that touches no material at all (e.g. far above the sheet) still picks
             // the side it lies on, so a stored fold keeps recomputing; it says so (#371).
             if let Some(p) = fixed
-                && !on_sheet_material(st, i, *p)
+                && !on_sheet_material(st, i, p.0)
             {
                 *warning = Some(format!(
                     "{} at ({:.3}, {:.3}, {:.3}); the side of the fold line it lies on stays",
@@ -579,7 +594,7 @@ pub(super) fn sheet_eval(
                 return Err(DocError::Invalid("refold the sheet before folding it".into()));
             }
             let n0 = sh.flanges.len();
-            sh.add_fold(a, b, ang, rr, position, *flip, *fixed, warning)?;
+            sh.add_fold(a, b, ang, rr, position, *flip, fixed.map(Vec3::from), warning)?;
             tag_flanges(sh, n0, f.id);
             rebuild_sheet(st, i)
         }
@@ -604,7 +619,7 @@ pub(super) fn sheet_eval(
             let mut picks = Vec::with_capacity(bends.len());
             for (i, p) in bends.iter().enumerate() {
                 let name = f.edge_names.get(i).filter(|n| !n.is_empty());
-                picks.push(match name.map(|n| (n, crate::naming::locate_edge(&mb, n, *p))) {
+                picks.push(match name.map(|n| (n, crate::naming::locate_edge(&mb, n, p.0))) {
                     Some((n, Ok(hit))) => {
                         if let Some(note) = hit.note(n) {
                             append_warning(warning, note);
@@ -613,21 +628,24 @@ pub(super) fn sheet_eval(
                     }
                     Some((n, Err(_))) => {
                         append_warning(warning, format!("edge `{n}` no longer exists; using the edge at the picked point"));
-                        *p
+                        p.0
                     }
-                    None => *p,
+                    None => p.0,
                 });
             }
-            let mut sh = sheet::convert_body(&mb, &r.name, &rv, *face, &picks)?;
+            let (mut sh, notes) = sheet::convert_body(&mb, &r.name, &rv, face.0, &picks)?;
+            for note in notes {
+                append_warning(warning, note);
+            }
             tag_flanges(&mut sh, 0, f.id);
             put_sheet(st, sh)
         }
         FeatureKind::SheetConvert { body, face, rule, .. } => {
             let mb = st.body(body).cloned().ok_or_else(|| DocError::Unknown(format!("body `{body}`")))?;
-            let n = planar_normal_at(&mb.body, *face).ok_or_else(|| DocError::Invalid("pick a planar face of the plate".into()))?;
+            let n = planar_normal_at(&mb.body, face.0).ok_or_else(|| DocError::Invalid("pick a planar face of the plate".into()))?;
             // Thickness: the body's extent along the face normal.
             let extent = |mesh: &solidcraft_geom::Mesh| {
-                mesh.positions.iter().map(|p| (*p - *face).dot(n)).fold((f64::MAX, f64::MIN), |(lo, hi), d| (lo.min(d), hi.max(d)))
+                mesh.positions.iter().map(|p| (*p - face.0).dot(n)).fold((f64::MAX, f64::MIN), |(lo, hi), d| (lo.min(d), hi.max(d)))
             };
             // The tolerance (the mesh's chords, and how far off the face's plane a point of it may
             // be) is at most a tenth of the thickness, not only a thousandth of the size. On a long
@@ -645,13 +663,13 @@ pub(super) fn sheet_eval(
             // The face outline: boundary edges of the triangles on that face's plane, where it runs
             // along a round wall an arc of the wall's circle (not chords: the plate check below
             // compares its area with the exact volume).
-            let plane = Plane::from_normal(*face + n * lo, n * -1.0).ok_or_else(|| DocError::Invalid("face".into()))?;
+            let plane = Plane::from_normal(face.0 + n * lo, n * -1.0).ok_or_else(|| DocError::Invalid("face".into()))?;
             // Recesses in one face (an engraved label) become pockets; the outline is the other face's.
-            let recesses = plate_recesses(&mb.body, &mesh, &plane, *face, n, (lo, hi), tol)?;
+            let recesses = plate_recesses(&mb.body, &mesh, &plane, face.0, n, (lo, hi), tol)?;
             let mut walls = std::collections::HashMap::new();
             let mut wall = |f: u32| *walls.entry(f).or_insert_with(|| sheet::round_wall(&mb.body, &plane, n, f));
             let mut loops: Vec<Loop2> =
-                face_outline(&mesh, &plane, *face, n, recesses.level, tol).iter().map(|l| sheet::outline_loop(l, &mut wall, tol * 1e-2)).collect();
+                face_outline(&mesh, &plane, face.0, n, recesses.level, tol).iter().map(|l| sheet::outline_loop(l, &mut wall, tol * 1e-2)).collect();
             loops.sort_by(|a, b| b.signed_area().abs().total_cmp(&a.signed_area().abs()));
             let mut it = loops.into_iter();
             let outer = it.next().ok_or_else(|| DocError::Invalid("no outline on that face".into()))?.ccw();
@@ -761,14 +779,24 @@ pub(super) fn sheet_cut(
     tools: &[Body],
     targets: &[String],
     constructor: Option<&ExtrudeConstructor>,
+    warning: &mut Option<String>,
 ) -> Result<Vec<String>> {
     let FeatureKind::Extrude { sketch, profiles, operation, extent, .. } = &f.kind else { return Ok(Vec::new()) };
     if extent.taper.is_some() || !any_eligible_sheet(f, st, targets) {
         return Ok(Vec::new());
     }
-    let Some(ss) = st.sketch(*sketch).cloned() else { return Ok(Vec::new()) };
+    let Some(ss) = st.sketch(sketch.0).cloned() else { return Ok(Vec::new()) };
     let regions = solidcraft_sketch::merge_regions(&select_profiles(&ss, profiles)?);
-    sheet_prism_cut(f, st, &ss.plane, &regions, *operation, tools, targets, constructor, extent.to.is_some())
+    // The outlines of the sketch's text: the sheet remembers where its letters went.
+    let text: Vec<Seg2> = ss
+        .sketch
+        .links
+        .iter()
+        .filter(|l| matches!(l.source, solidcraft_sketch::LinkSource::Text { .. }))
+        .flat_map(|l| ss.sketch.link_curves(&l.id))
+        .flat_map(|ci| ss.sketch.exact_segs(ci).unwrap_or_else(|| ss.sketch.segs(ci)))
+        .collect();
+    sheet_prism_cut(f, st, &ss.plane, &regions, *operation, tools, targets, constructor, extent.to.is_some(), &text, warning)
 }
 
 /// Whether a cut of `f` with these targets (else its participants, else its component's
@@ -800,6 +828,7 @@ pub(super) fn sheet_primitive_cut(
     prism: PrimitivePrism,
     operation: Operation,
     drill: bool,
+    warning: &mut Option<String>,
 ) -> Result<Vec<String>> {
     if !matches!(operation, Operation::Cut | Operation::Intersect) || !any_eligible_sheet(f, st, &[]) {
         return Ok(Vec::new());
@@ -824,7 +853,7 @@ pub(super) fn sheet_primitive_cut(
     let Some(normal) = normal else { return Ok(Vec::new()) };
     let Some((plane, region, interval)) = prism.along(normal) else { return Ok(Vec::new()) };
     let tools = kernel::extrude(&plane, std::slice::from_ref(&region), interval.0, interval.1)?;
-    sheet_prism_cut(f, st, &plane, std::slice::from_ref(&region), operation, &tools, &[], None, false)
+    sheet_prism_cut(f, st, &plane, std::slice::from_ref(&region), operation, &tools, &[], None, false, &[], warning)
 }
 
 /// A hole's straight drill along a panel of a sheet (into its rim), kept as a bore of each
@@ -911,6 +940,12 @@ impl PrimitivePrism {
     }
 }
 
+/// The most outline segments of a sketch's text a cut tells letters by, and the most text regions
+/// a sheet keeps (see [`crate::sheet::SheetBody::labels`]).
+const MAX_TEXT_CURVES: usize = 20_000;
+const MAX_LABELS: usize = 1000;
+
+/// `text` is the outlines of the text in the cut's sketch (none for a primitive's cut).
 #[allow(clippy::too_many_arguments)]
 fn sheet_prism_cut(
     f: &Feature,
@@ -922,6 +957,8 @@ fn sheet_prism_cut(
     targets: &[String],
     constructor: Option<&ExtrudeConstructor>,
     footprints_bound: bool,
+    text: &[Seg2],
+    warning: &mut Option<String>,
 ) -> Result<Vec<String>> {
     let n = plane.normal();
     let mut work = sheet::FlatWork::new();
@@ -960,7 +997,14 @@ fn sheet_prism_cut(
             && current_footprints.iter().all(|(plane, r)| plane.x == placed_basis.x && plane.y == placed_basis.y && regions.contains(r)))
         .then_some(c.interval)
     });
+    // The regions of the cut that are letters, with their counters.
+    let letters: Vec<&Region2> = if operation == Operation::Cut && !text.is_empty() && text.len() <= MAX_TEXT_CURVES {
+        regions.iter().filter(|r| sheet::loop_lies_on(&r.outer, text)).collect()
+    } else {
+        Vec::new()
+    };
     let mut plans = Vec::new();
+    let mut notes = Vec::new();
     'sheets: for original in &st.sheets {
         if !sheet_eligible(f, st, targets, original) {
             continue;
@@ -993,6 +1037,7 @@ fn sheet_prism_cut(
             sh.material_panels(Some(plane), &mut work)?
         };
         let mut modeled = false;
+        let mut labels = Vec::new();
         for (pi, panel) in candidates {
             let w = if sh.flat { sh.world(None) } else { sh.world(pi) };
             let zorigin = (apply_point(&w, Vec3::ZERO) - plane.origin).dot(n);
@@ -1032,6 +1077,7 @@ fn sheet_prism_cut(
             let (z0, z1) = (a.min(b).max(0.0), a.max(b).min(sh.t));
             // Sub-resolution layers must not be silently erased by endpoint snapping.
             let depth_resolved = ![z0, sh.t - z1, z1 - z0].into_iter().any(|d| d > 0.0 && d < 1e-6);
+            labels.extend(letters.iter().filter_map(|r| sh.region_to_flat(pi, plane, r).ok()));
             let mapped = if footprints_bound && current_footprints.len() == tools.len() {
                 current_footprints.iter().map(|(plane, r)| sh.region_to_flat(pi, plane, r)).collect::<Result<Vec<_>>>()?
             } else {
@@ -1096,19 +1142,34 @@ fn sheet_prism_cut(
                 }
             }
         }
+        if modeled {
+            for flat in labels {
+                if !sh.labels.contains(&flat) && sh.labels.len() < MAX_LABELS {
+                    sh.labels.push(flat);
+                }
+            }
+        }
         if !modeled {
             super::sheet_boolean_unchanged(&mb.body, tools, operation)?;
             plans.push((sh.body.clone(), Some((sh, mb.body.clone()))));
-        } else if sh.flat_material()?.is_empty() {
-            // Empty exact material removes geometry and metadata together. Budget or
-            // topology errors propagate; they are never mistaken for an empty blank.
-            plans.push((sh.body.clone(), None));
         } else {
-            let body = sh.solid()?;
-            plans.push((sh.body.clone(), Some((sh, body))));
+            let material = sh.flat_material()?;
+            if material.is_empty() {
+                // Empty exact material removes geometry and metadata together. Budget or
+                // topology errors propagate; they are never mistaken for an empty blank.
+                plans.push((sh.body.clone(), None));
+            } else {
+                // Every piece the cut leaves stays; the ones it parts from the base are named.
+                notes.extend(parted_note(&sh, &material, original));
+                let body = sh.solid()?;
+                plans.push((sh.body.clone(), Some((sh, body))));
+            }
         }
     }
     let handled = plans.iter().map(|(name, _)| name.clone()).collect();
+    if !notes.is_empty() {
+        append_warning(warning, notes.join("; "));
+    }
     for (name, result) in plans {
         match result {
             Some((sh, body)) => {
@@ -1129,6 +1190,35 @@ fn sheet_prism_cut(
     Ok(handled)
 }
 
+/// A cut's note on the pieces it parted from the base of `sh` (see
+/// [`sheet::SheetBody::parted_from_base`]; `material` is the sheet's flat material after the cut,
+/// `before` the sheet before it): how many, their area and where they lie in the flat pattern.
+/// The pieces stay, as every piece a cut leaves does. None when nothing is parted, and when the
+/// pieces can't be worked out: the note is no reason for a cut to fail.
+fn parted_note(sh: &sheet::SheetBody, material: &[Region2], before: &sheet::SheetBody) -> Option<String> {
+    let pieces = sh.parted_from_base(material, before).ok().filter(|p| !p.is_empty())?;
+    let area: f64 = pieces.iter().map(Region2::area).sum();
+    let at: Vec<String> = pieces
+        .iter()
+        .take(4)
+        .map(|r| {
+            let c = r.interior_point();
+            format!("({:.1}, {:.1})", c.x, c.y)
+        })
+        .collect();
+    let at = at.join(", ");
+    let body = &sh.body;
+    Some(match pieces.len() {
+        1 => format!("1 piece of `{body}` is no longer joined to its base ({area:.2} mm², near {at} in the flat pattern); it is kept"),
+        n => {
+            let more = if n > 4 { format!(" and {} more", n - 4) } else { String::new() };
+            format!(
+                "{n} pieces of `{body}` are no longer joined to its base ({area:.2} mm² in all, near {at}{more} in the flat pattern); they are kept"
+            )
+        }
+    })
+}
+
 /// Outline loops (in `plane` coordinates) of the mesh triangles lying in the plane at distance
 /// `level` from `at` along `n`: the edges used by one of them only, chained.
 fn face_loops(mesh: &solidcraft_geom::Mesh, plane: &Plane, at: Vec3, n: Vec3, level: f64, tol: f64) -> Vec<Vec<Vec2>> {
@@ -1390,7 +1480,7 @@ fn plate_recesses(body: &Body, mesh: &Mesh, plane: &Plane, at: Vec3, n: Vec3, (l
 }
 
 /// The body a placed plastic feature joins: by name, else the one under the point.
-fn body_under(st: &ModelState, body: &Option<String>, p: Vec3) -> Result<String> {
+fn body_under(st: &ModelState, body: &Option<crate::BodyName>, p: Vec3) -> Result<String> {
     let i = body_at(st, body, &[p])?;
     let b = st.bodies.get(i).ok_or_else(|| DocError::Invalid("there is no body".into()))?;
     let tolerance = (b.body.size() * 1e-5).max(1e-4);
@@ -1452,7 +1542,7 @@ pub(super) fn plastic_eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &F
             rib_offset,
             body,
         } => {
-            let target = body_under(st, body, *position)?;
+            let target = body_under(st, body, position.0)?;
             let (r0, h) = (len(diameter)? / 2.0, len(height)?);
             if !(r0 > 0.0 && h > 0.0) {
                 return Err(DocError::Invalid("the boss diameter and height must be positive".into()));
@@ -1470,9 +1560,9 @@ pub(super) fn plastic_eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &F
                 return Err(DocError::Invalid("the draft closes the boss before its top".into()));
             }
             let delta = (h * 0.05).clamp(1e-3, 0.5);
-            let (x, _, z) = local_frame(*direction, None)?;
+            let (x, _, z) = local_frame(direction.0, None)?;
             // The post: a (tapered) cylinder from a little inside the face.
-            let base = Plane::new(*position - z * delta, x, z.cross(x)).ok_or_else(|| DocError::Invalid("boss frame".into()))?;
+            let base = Plane::new(position.0 - z * delta, x, z.cross(x)).ok_or_else(|| DocError::Invalid("boss frame".into()))?;
             let r_in = r0 + delta * dr.tan();
             let disc = Region2 { outer: Loop2::circle(Vec2::ZERO, r_in), holes: Vec::new() };
             let post = if dr.abs() > 1e-12 {
@@ -1505,7 +1595,7 @@ pub(super) fn plastic_eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &F
                 for k in 0..n as usize {
                     let a = std::f64::consts::TAU * k as f64 / n;
                     let (u, v) = (x * a.cos() + z.cross(x) * a.sin(), z.cross(x) * a.cos() - x * a.sin());
-                    let rp = Plane::new(*position, u, v).ok_or_else(|| DocError::Invalid("rib frame".into()))?;
+                    let rp = Plane::new(position.0, u, v).ok_or_else(|| DocError::Invalid("rib frame".into()))?;
                     let rect = Region2 {
                         outer: Loop2::polygon(&[
                             Vec2::new(r0 * 0.5, -t / 2.0),
@@ -1524,7 +1614,7 @@ pub(super) fn plastic_eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &F
                 let i = st.bodies.iter().position(|b| b.name == target).ok_or_else(|| DocError::Invalid("boss body".into()))?;
                 let Some(mb) = st.bodies.get(i).cloned() else { return Err(DocError::Invalid("boss body".into())) };
                 let mut warn = None;
-                let edges = resolve_edges(&mb.body, &[*position + x * r0], &[], &mut warn)?;
+                let edges = resolve_edges(&mb.body, &[position.0 + x * r0], &[], &mut warn)?;
                 let nb = mb.traced().then(kernel::fillet(&mb.body, &edges, rf)?);
                 if let Some(slot) = st.bodies.get_mut(i) {
                     *slot = ModelBody::traced_new(mb.name, nb, mb.feature);
@@ -1539,7 +1629,7 @@ pub(super) fn plastic_eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &F
                 if !(rh > 0.0 && rh < r_top && depth > 0.0) {
                     return Err(DocError::Invalid("the boss hole must fit inside the boss".into()));
                 }
-                let hp = Plane::new(*position, x, z.cross(x)).ok_or_else(|| DocError::Invalid("hole frame".into()))?;
+                let hp = Plane::new(position.0, x, z.cross(x)).ok_or_else(|| DocError::Invalid("hole frame".into()))?;
                 let tool = kernel::extrude(&hp, &[Region2 { outer: Loop2::circle(Vec2::ZERO, rh), holes: Vec::new() }], h - depth, h + delta)?;
                 let tool = tool.into_iter().map(|b| crate::lineage::part_tool(b, "hole")).collect();
                 apply_traced(st, f, tool, Operation::Cut, std::slice::from_ref(&target))?;
@@ -1547,9 +1637,9 @@ pub(super) fn plastic_eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &F
             Ok(())
         }
         FeatureKind::Lip { face, width, height, groove, gap, outside, body } => {
-            let target = body_under(st, body, *face)?;
+            let target = body_under(st, body, face.0)?;
             let mb = st.body(&target).cloned().ok_or_else(|| DocError::Invalid("body".into()))?;
-            let n = planar_normal_at(&mb.body, *face).ok_or_else(|| DocError::Invalid("pick the planar rim face".into()))?;
+            let n = planar_normal_at(&mb.body, face.0).ok_or_else(|| DocError::Invalid("pick the planar rim face".into()))?;
             let (w, h) = (len(width)?, len(height)?);
             let g = match gap {
                 Some(e) => len(e)?,
@@ -1559,10 +1649,10 @@ pub(super) fn plastic_eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &F
             if !(w > 0.0 && h > 0.0 && g >= 0.0) {
                 return Err(DocError::Invalid("the lip width and height must be positive".into()));
             }
-            let plane = Plane::from_normal(*face, n).ok_or_else(|| DocError::Invalid("rim plane".into()))?;
+            let plane = Plane::from_normal(face.0, n).ok_or_else(|| DocError::Invalid("rim plane".into()))?;
             let tol = (mb.body.size() * 1e-3).max(1e-3);
             let mesh = mb.body.tessellate(tol)?;
-            let mut loops = face_loops(&mesh, &plane, *face, n, 0.0, tol);
+            let mut loops = face_loops(&mesh, &plane, face.0, n, 0.0, tol);
             loops.sort_by(|a, b| poly_area(b).abs().total_cmp(&poly_area(a).abs()));
             let ccw = |l: &[Vec2]| if poly_area(l) < 0.0 { l.iter().rev().copied().collect::<Vec<_>>() } else { l.to_vec() };
             // The inner edge is an opening (the cavity under a rim): not the foot of a boss or a
@@ -1596,7 +1686,7 @@ pub(super) fn plastic_eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &F
             // A lip: the band raised from the rim's own faces (its walls continue the walls
             // below, which a join can't do: they would coincide).
             if !*groove
-                && let Ok(b) = kernel::raise_band(&mb.body, *face, w, h, *outside)
+                && let Ok(b) = kernel::raise_band(&mb.body, face.0, w, h, *outside)
                 && let Some(slot) = st.bodies.iter_mut().find(|x| x.name == target)
             {
                 *slot = ModelBody::traced_new(target.clone(), Traced::step(b, &[&mb.traced()]), slot.feature);
@@ -1626,17 +1716,17 @@ pub(super) fn plastic_eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &F
             }
         }
         FeatureKind::SnapFit { position, direction, hook, length, thickness, width, catch_depth, catch_length, body } => {
-            let target = body_under(st, body, *position)?;
+            let target = body_under(st, body, position.0)?;
             let (l, t, w, cd, cl) = (len(length)?, len(thickness)?, len(width)?, len(catch_depth)?, len(catch_length)?);
             if !(l > 0.0 && t > 0.0 && w > 0.0 && cd > 0.0 && cl > 0.0 && cl < l) {
                 return Err(DocError::Invalid("the snap fit's sizes must be positive and the catch shorter than the arm".into()));
             }
-            let (x, y, z) = local_frame(*direction, Some(*hook))?;
+            let (x, y, z) = local_frame(direction.0, Some(hook.0))?;
             let delta = (l * 0.05).clamp(1e-3, 0.5);
             // Side profile (x = toward the catch, y = up the arm), extruded across the width.
             let pts =
                 [Vec2::new(-t, -delta), Vec2::new(0.0, -delta), Vec2::new(0.0, l - cl), Vec2::new(cd, l - cl), Vec2::new(0.0, l), Vec2::new(-t, l)];
-            let o = *position - y * (w / 2.0);
+            let o = position.0 - y * (w / 2.0);
             let pl = Plane::new(o, x, z).ok_or_else(|| DocError::Invalid("snap fit frame".into()))?;
             let mut lp = Loop2::polygon(&pts);
             if lp.signed_area() < 0.0 {
@@ -1649,7 +1739,7 @@ pub(super) fn plastic_eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &F
             apply_traced(st, f, tool, Operation::Join, std::slice::from_ref(&target))
         }
         FeatureKind::Rest { position, direction, along, width, length, height, draft, thickness, body } => {
-            let target = body_under(st, body, *position)?;
+            let target = body_under(st, body, position.0)?;
             let (w, h) = (len(width)?, len(height)?);
             let l = length.as_deref().map(len).transpose()?;
             let dr = match draft {
@@ -1672,7 +1762,7 @@ pub(super) fn plastic_eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &F
                 return Err(DocError::Invalid("the draft closes the rest before its top".into()));
             }
             let delta = (h * 0.05).clamp(1e-3, 0.5);
-            let (x, y, z) = local_frame(*direction, *along)?;
+            let (x, y, z) = local_frame(direction.0, along.map(Vec3::from))?;
             // Sized at the face: the tool starts a little inside, grown by the draft over that.
             let e = delta * dr.tan();
             let shape = |grow: f64| match l {
@@ -1689,7 +1779,7 @@ pub(super) fn plastic_eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &F
                 None => Vec::new(),
             };
             let region = Region2 { outer: shape(e), holes };
-            let base = Plane::new(*position - z * delta, x, y).ok_or_else(|| DocError::Invalid("rest frame".into()))?;
+            let base = Plane::new(position.0 - z * delta, x, y).ok_or_else(|| DocError::Invalid("rest frame".into()))?;
             let tool = if dr.abs() > 1e-12 {
                 vec![kernel::extrude_tapered(&base, &region, h + delta, 1.0, -dr)?]
             } else {

crates/doc/src/eval_surface.rs

@@ -6,21 +6,27 @@ use super::*;
 use crate::{RuledCorners, RuledMode};
 use solidcraft_geom::Seg2;
 
-pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature, st: &mut ModelState) -> Result<()> {
+pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature, st: &mut ModelState, warning: &mut Option<String>) -> Result<()> {
     match &f.kind {
-        FeatureKind::Patch { sketch, profiles, body, edges } => {
+        FeatureKind::Patch { sketch, profiles, body, edges, crown, continuity, points } => {
             let mut made = Vec::new();
             if let Some(sk) = sketch {
-                let ss = st.sketch(*sk).ok_or_else(|| DocError::Unknown(format!("sketch {sk} (it must come earlier in the timeline)")))?;
+                let ss = st.sketch(sk.0).ok_or_else(|| DocError::Unknown(format!("sketch {sk} (it must come earlier in the timeline)")))?;
                 let regions = solidcraft_sketch::merge_regions(&select_profiles(ss, profiles)?);
                 for r in &regions {
                     made.push(kernel::patch_region(&ss.plane, r)?);
                 }
             }
             if !edges.is_empty() {
-                let i = body_at(st, body, edges)?;
+                let i = body_at(st, body, &crate::plain(edges))?;
                 let b = st.bodies.get(i).ok_or_else(|| DocError::Invalid("body".into()))?;
-                made.push(kernel::patch_edges(&b.body, edges)?);
+                let spec = kernel::PatchSpec {
+                    continuity: continuity.all,
+                    edges: continuity.edges.iter().map(|e| (e.edge.0, e.g)).collect(),
+                    points: crate::plain(points),
+                    crown: *crown,
+                };
+                made.push(kernel::patch_edges_with(&b.body, &crate::plain(edges), &spec)?);
             }
             if made.is_empty() {
                 return Err(DocError::Invalid("a patch needs a sketch region or a loop of edges".into()));
@@ -59,7 +65,7 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
             if tools.is_empty() {
                 return Err(DocError::Invalid("pick the surfaces to thicken".into()));
             }
-            apply_op(st, f, tools, *operation, targets)
+            apply_op(st, f, tools, *operation, &crate::plain(targets))
         }
         FeatureKind::SurfaceTrim { body, plane, tool, keep } => {
             let i = st.bodies.iter().position(|b| &b.name == body).ok_or_else(|| DocError::Unknown(format!("body `{body}`")))?;
@@ -67,11 +73,11 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
             let trimmed = match tool {
                 Some(t) => {
                     let tb = st.body(&t.body).ok_or_else(|| DocError::Unknown(format!("body `{}`", t.body)))?;
-                    let face = crate::appearance::face_index_at(tb, t.point)
+                    let face = crate::appearance::face_index_at(tb, t.point.0)
                         .ok_or_else(|| DocError::Invalid(format!("no face of `{}` at the tool point", t.body)))?;
-                    kernel::trim(&mb.body, &kernel::SplitTool::Face { body: &tb.body, face }, *keep)?
+                    kernel::trim(&mb.body, &kernel::SplitTool::Face { body: &tb.body, face }, keep.0)?
                 }
-                None => kernel::trim(&mb.body, &kernel::SplitTool::Plane(doc.resolve_plane_in(vals, plane, 0, Some(st))?), *keep)?,
+                None => kernel::trim(&mb.body, &kernel::SplitTool::Plane(doc.resolve_plane_in(vals, plane, 0, Some(st))?), keep.0)?,
             };
             if let Some(slot) = st.bodies.get_mut(i) {
                 *slot = ModelBody::new(mb.name, trimmed, mb.feature);
@@ -88,18 +94,20 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
             };
             let at = |limit| kernel::ExtendOptions { mode, limit, neighbours: *neighbours };
             let out = match up_to {
-                None => kernel::extend_surface(&mb.body, edges, &at(kernel::ExtendLimit::Distance(val(vals, distance, Kind::Length)?)))?,
-                Some(crate::ExtendTo::Bounds) => kernel::extend_surface(&mb.body, edges, &at(kernel::ExtendLimit::Bounds))?,
+                None => {
+                    kernel::extend_surface(&mb.body, &crate::plain(edges), &at(kernel::ExtendLimit::Distance(val(vals, distance, Kind::Length)?)))?
+                }
+                Some(crate::ExtendTo::Bounds) => kernel::extend_surface(&mb.body, &crate::plain(edges), &at(kernel::ExtendLimit::Bounds))?,
                 Some(crate::ExtendTo::Plane(plane)) => {
                     let tool = kernel::SplitTool::Plane(doc.resolve_plane_in(vals, plane, 0, Some(st))?);
-                    kernel::extend_surface(&mb.body, edges, &at(kernel::ExtendLimit::UpTo(&tool)))?
+                    kernel::extend_surface(&mb.body, &crate::plain(edges), &at(kernel::ExtendLimit::UpTo(&tool)))?
                 }
                 Some(crate::ExtendTo::Face(t)) => {
                     let tb = st.body(&t.body).ok_or_else(|| DocError::Unknown(format!("body `{}`", t.body)))?;
-                    let face = crate::appearance::face_index_at(tb, t.point)
+                    let face = crate::appearance::face_index_at(tb, t.point.0)
                         .ok_or_else(|| DocError::Invalid(format!("no face of `{}` at the target point", t.body)))?;
                     let tool = kernel::SplitTool::Face { body: &tb.body, face };
-                    kernel::extend_surface(&mb.body, edges, &at(kernel::ExtendLimit::UpTo(&tool)))?
+                    kernel::extend_surface(&mb.body, &crate::plain(edges), &at(kernel::ExtendLimit::UpTo(&tool)))?
                 }
             };
             if let Some(slot) = st.bodies.get_mut(i) {
@@ -107,10 +115,112 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
             }
             Ok(())
         }
+        FeatureKind::SurfaceBlend { from, to, continuity, bulge, align, stitch } => {
+            let a = st.body(&from.body).ok_or_else(|| DocError::Unknown(format!("body `{}`", from.body)))?.body.clone();
+            let b = st.body(&to.body).ok_or_else(|| DocError::Unknown(format!("body `{}`", to.body)))?.body.clone();
+            if from.edges.is_empty() || to.edges.is_empty() {
+                return Err(DocError::Invalid("a blend needs a chain of edges at each end".into()));
+            }
+            let (made, gap) = kernel::blend_between(
+                &a,
+                &crate::plain(&from.edges),
+                &b,
+                &crate::plain(&to.edges),
+                *continuity,
+                *bulge,
+                align.map(|[p, q]| [p.0, q.0]),
+                BLEND_STATIONS,
+                *stitch,
+            )?;
+            if gap > 1e-9 {
+                *warning = Some(format!("the blend's boundary lies up to {gap:.4} mm from the edges it was built on"));
+            }
+            let name = new_name(st, f, 0);
+            // A stitched blend takes the place of both bodies it joins; otherwise it is a new
+            // surface body of its own.
+            if *stitch {
+                let gone = [from.body.0.clone(), to.body.0.clone()];
+                st.bodies.retain(|x| !gone.contains(&x.name));
+            }
+            st.bodies.push(ModelBody::new(name, made, f.id));
+            Ok(())
+        }
+        FeatureKind::SurfaceBoundary { sketch, curves, orders, crown, samples } => {
+            let ss = sketch_in_feature_frame(
+                doc,
+                st.sketch(sketch.0).ok_or_else(|| DocError::Unknown(format!("sketch {sketch} (it must come earlier in the timeline)")))?,
+                f.component,
+            )?;
+            let boundaries = boundary_frames(&ss, curves, orders, *samples)?;
+            let body = kernel::boundary_patch(&boundaries, *crown, *samples)?;
+            let name = new_name(st, f, 0);
+            st.bodies.push(ModelBody::new(name, body, f.id));
+            Ok(())
+        }
+        FeatureKind::SurfaceMatch { body, faces, target, edges, order } => {
+            let i = st.bodies.iter().position(|b| &b.name == body).ok_or_else(|| DocError::Unknown(format!("body `{body}`")))?;
+            let Some(mb) = st.bodies.get(i).cloned() else { return Err(DocError::Invalid("body".into())) };
+            let tb = st.body(target).ok_or_else(|| DocError::Unknown(format!("body `{target}`")))?.body.clone();
+            if edges.is_empty() {
+                return Err(DocError::Invalid("a match needs a chain of the target's edges".into()));
+            }
+            // Picked by a point on the face; without picks, the body's first face.
+            let picked: Vec<solidcraft_geom::Vec3> = if faces.is_empty() {
+                let faces = mb.body.faces(mb.body.size() * 1e-2)?;
+                vec![faces.first().ok_or_else(|| DocError::Invalid(format!("`{body}` has no face to match")))?.centroid]
+            } else {
+                crate::plain(faces)
+            };
+            let made = kernel::match_surface(&mb.body, &picked, &tb, &crate::plain(edges), *order)?;
+            // A match rebuilds the face in place: the body keeps its name, and whatever meets it
+            // downstream still finds it.
+            if let Some(slot) = st.bodies.get_mut(i) {
+                *slot = ModelBody::new(mb.name, made, mb.feature);
+            }
+            Ok(())
+        }
+        FeatureKind::SurfaceFair { body, faces, strength, iterations, keep_edges, tolerance } => {
+            let tol = val(vals, tolerance, Kind::Length)?;
+            let opts = kernel::FairOptions::new(*strength, *iterations as usize, *keep_edges, tol)?;
+            let i = st.bodies.iter().position(|b| &b.name == body).ok_or_else(|| DocError::Unknown(format!("body `{body}`")))?;
+            let Some(mb) = st.bodies.get(i).cloned() else { return Err(DocError::Invalid("body".into())) };
+            // Picked by a point on the face; without picks, every face of the body.
+            let mut picked: Vec<usize> = Vec::new();
+            if faces.is_empty() {
+                picked.extend(0..mb.body.face_count());
+            } else {
+                for p in faces {
+                    let fi =
+                        crate::appearance::face_index_at(&mb, p.0).ok_or_else(|| DocError::Invalid(format!("Fair: no face of {body} at {p:?}")))?;
+                    if !picked.contains(&fi) {
+                        picked.push(fi);
+                    }
+                }
+            }
+            if picked.is_empty() {
+                return Err(DocError::Invalid("the body has no faces to fair".into()));
+            }
+            // The face keeps every edge it had: only the surface between them is faired. The
+            // energy before and after goes into the feature's warning, so the reply can say how
+            // much the face moved.
+            let (faired, report) = kernel::fair_faces(&mb.body, &picked, &opts)?;
+            *warning = Some(format!(
+                "faired {} face(s): energy {:.6} → {:.6} in {} step(s), control points moved up to {:.4} mm",
+                picked.len(),
+                report.energy_before,
+                report.energy_after,
+                report.steps,
+                report.movement
+            ));
+            if let Some(slot) = st.bodies.get_mut(i) {
+                *slot = ModelBody::new(mb.name, faired, mb.feature);
+            }
+            Ok(())
+        }
         FeatureKind::SurfaceExtrude { sketch, profiles, curves, extent } => {
             let ss = sketch_in_feature_frame(
                 doc,
-                st.sketch(*sketch).ok_or_else(|| DocError::Unknown(format!("sketch {sketch} (it must come earlier in the timeline)")))?,
+                st.sketch(sketch.0).ok_or_else(|| DocError::Unknown(format!("sketch {sketch} (it must come earlier in the timeline)")))?,
                 f.component,
             )?;
             if extent.through_all || extent.taper.is_some() || extent.to.is_some() || extent.from.is_some() {
@@ -127,7 +237,7 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
         FeatureKind::SurfaceRevolve { sketch, profiles, curves, axis, angle, angle2, symmetric } => {
             let ss = sketch_in_feature_frame(
                 doc,
-                st.sketch(*sketch).ok_or_else(|| DocError::Unknown(format!("sketch {sketch} (it must come earlier in the timeline)")))?,
+                st.sketch(sketch.0).ok_or_else(|| DocError::Unknown(format!("sketch {sketch} (it must come earlier in the timeline)")))?,
                 f.component,
             )?;
             let (o, d) = revolve_axis(&ss, axis)?;
@@ -148,7 +258,7 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
         FeatureKind::Unstitch { body, faces } => {
             let i = st.bodies.iter().position(|b| &b.name == body).ok_or_else(|| DocError::Unknown(format!("body `{body}`")))?;
             let Some(mb) = st.bodies.get(i).cloned() else { return Err(DocError::Invalid("body".into())) };
-            let (pieces, rest) = kernel::unstitch(&mb.body, faces)?;
+            let (pieces, rest) = kernel::unstitch(&mb.body, &crate::plain(faces))?;
             let source = mb.traced();
             // The faces left keep the body's name; each face taken out is a new surface body.
             match rest {
@@ -170,16 +280,17 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
         FeatureKind::ReverseNormal { body, faces } => {
             let i = st.bodies.iter().position(|b| &b.name == body).ok_or_else(|| DocError::Unknown(format!("body `{body}`")))?;
             let Some(mb) = st.bodies.get(i).cloned() else { return Err(DocError::Invalid("body".into())) };
-            let turned = mb.traced().then(kernel::reverse_faces(&mb.body, faces)?);
+            let turned = mb.traced().then(kernel::reverse_faces(&mb.body, &crate::plain(faces))?);
             if let Some(slot) = st.bodies.get_mut(i) {
                 *slot = ModelBody::traced_new(mb.name, turned, mb.feature);
             }
             Ok(())
         }
-        FeatureKind::SurfaceSweep { sketch, profiles, curves, path_sketch, path } => {
-            let ss = st.sketch(*sketch).ok_or_else(|| DocError::Unknown(format!("sketch {sketch} (it must come earlier in the timeline)")))?;
+        FeatureKind::SurfaceSweep { sketch, profiles, curves, path_sketch, path, orientation, twist, scale } => {
+            let ctl = crate::eval::sweep_control(vals, orientation, twist, scale)?;
+            let ss = st.sketch(sketch.0).ok_or_else(|| DocError::Unknown(format!("sketch {sketch} (it must come earlier in the timeline)")))?;
             let ps =
-                st.sketch(*path_sketch).ok_or_else(|| DocError::Unknown(format!("sketch {path_sketch} (it must come earlier in the timeline)")))?;
+                st.sketch(path_sketch.0).ok_or_else(|| DocError::Unknown(format!("sketch {path_sketch} (it must come earlier in the timeline)")))?;
             // As Sweep: a 3D path sketch is followed in the feature's frame, the curves with it.
             let profile;
             let ss = if !ps.sketch.wires.is_empty() {
@@ -195,8 +306,8 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
             let pts: Vec<Vec2> = chains.iter().flatten().flat_map(|s| s.polyline(1e-2)).collect();
             let start = ss.plane.to_world(pts.iter().fold(Vec2::default(), |a, p| a + *p) * (1.0 / pts.len().max(1) as f64));
             let body = match path_points(ps, path, start)? {
-                Some(pts) => kernel::sweep_sheet_points(&ss.plane, &chains, &pts)?,
-                None => kernel::sweep_sheet(&ss.plane, &chains, &path_segments(ps, path, start)?)?,
+                Some(pts) => kernel::sweep_sheet_points_with(&ss.plane, &chains, &pts, &ctl)?,
+                None => kernel::sweep_sheet_with(&ss.plane, &chains, &path_segments(ps, path, start)?, &ctl)?,
             };
             let traced = crate::lineage::ChainRoles { sketch: ss, chains: &chains }.tool(body);
             push_sheet(st, f, traced);
@@ -208,7 +319,7 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
             for sec in sections {
                 let ss = sketch_in_feature_frame(
                     doc,
-                    st.sketch(sec.sketch)
+                    st.sketch(sec.sketch.0)
                         .ok_or_else(|| DocError::Unknown(format!("sketch {} (it must come earlier in the timeline)", sec.sketch)))?,
                     f.component,
                 )?;
@@ -238,9 +349,9 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
                 Some(t) => val(vals, t, Kind::Length)?,
                 None => 0.01,
             };
-            let i = body_at(st, body, faces)?;
+            let i = body_at(st, body, &crate::plain(faces))?;
             let Some(mb) = st.bodies.get(i).cloned() else { return Err(DocError::Invalid("body".into())) };
-            let picks = if *chain { smooth_chain(&mb, faces) } else { faces.clone() };
+            let picks = if *chain { smooth_chain(&mb, &crate::plain(faces)) } else { crate::plain(faces) };
             let mut picked: Vec<usize> = Vec::new();
             for p in &picks {
                 let fi =
@@ -261,10 +372,10 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
                 RuledMode::Tangent => kernel::RuledMode::Tangent,
                 RuledMode::Angle => {
                     let a = angle.as_ref().ok_or_else(|| DocError::Invalid("a ruled surface at an angle needs `angle`".into()))?;
-                    kernel::RuledMode::Angle { angle: val(vals, a, Kind::Angle)?, reference: *direction }
+                    kernel::RuledMode::Angle { angle: val(vals, a, Kind::Angle)?, reference: direction.map(Vec3::from) }
                 }
                 RuledMode::Direction => kernel::RuledMode::Direction(
-                    direction.ok_or_else(|| DocError::Invalid("a ruled surface along a direction needs `direction`".into()))?,
+                    direction.map(Vec3::from).ok_or_else(|| DocError::Invalid("a ruled surface along a direction needs `direction`".into()))?,
                 ),
             };
             let corners = match corners {
@@ -272,8 +383,8 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
                 RuledCorners::Round => kernel::RuledCorners::Round,
             };
             let mb = st.body(body).cloned().ok_or_else(|| DocError::Unknown(format!("body `{body}`")))?;
-            let r = kernel::Ruled { distance: d, mode, flip: *flip, corners, face: *face };
-            let made = Traced::step(kernel::ruled_surface(&mb.body, edges, &r)?, &[&mb.traced()]);
+            let r = kernel::Ruled { distance: d, mode, flip: *flip, corners, face: face.map(Vec3::from) };
+            let made = Traced::step(kernel::ruled_surface(&mb.body, &crate::plain(edges), &r)?, &[&mb.traced()]);
             let name = new_name(st, f, 0);
             st.bodies.push(ModelBody::traced_new(name, made, f.id));
             Ok(())
@@ -281,11 +392,11 @@ pub(super) fn eval(doc: &Document, vals: &BTreeMap<String, Value>, f: &Feature,
         FeatureKind::SurfaceUntrim { face, holes, outer, in_place } => {
             let i = st.bodies.iter().position(|b| b.name == face.body).ok_or_else(|| DocError::Unknown(format!("body `{}`", face.body)))?;
             let Some(mb) = st.bodies.get(i).cloned() else { return Err(DocError::Invalid("body".into())) };
-            let fi = crate::appearance::face_index_at(&mb, face.point)
+            let fi = crate::appearance::face_index_at(&mb, face.point.0)
                 .ok_or_else(|| DocError::Invalid(format!("Untrim: no face of {} at {:?}", mb.name, face.point)))?;
             let which = match holes {
                 None => kernel::UntrimHoles::All,
-                Some(points) => kernel::UntrimHoles::At(points),
+                Some(points) => kernel::UntrimHoles::At(&crate::plain(points)),
             };
             // A surface body's face is untrimmed where it is when asked; a solid's is copied out.
             let replace = *in_place && mb.body.is_surface();
@@ -310,6 +421,70 @@ fn push_sheet(st: &mut ModelState, f: &Feature, traced: crate::lineage::Traced)
     st.bodies.push(ModelBody::traced_new(name, traced, f.id));
 }
 
+/// The boundaries `surface.boundary` builds its patch from: each picked curve's own stations in
+/// the sketch's frame, every one of them leaving the boundary square into the loop — the direction
+/// from the curve towards the middle of the loop, taken across its tangent — over the plane the
+/// curve lies in (so a chain of planar curves makes a flat patch, and a network that is not
+/// coplanar is followed as the plane through the curve's own tangent). `orders` sets how much of
+/// that plane each side repeats.
+fn boundary_frames(
+    ss: &SolvedSketch,
+    curves: &[String],
+    orders: &[solidcraft_kernel::Continuity],
+    samples: usize,
+) -> Result<Vec<solidcraft_kernel::Boundary>> {
+    use solidcraft_kernel::{Boundary, Frame};
+    // The stations along each curve, evenly in its own arclength, so every side carries the same
+    // number of frames and the patch's net is square.
+    let mut sides: Vec<Vec<solidcraft_geom::Vec3>> = Vec::with_capacity(curves.len());
+    for id in curves {
+        let ci = ss.sketch.curve_index(id).ok_or_else(|| DocError::Unknown(format!("sketch curve `{id}`")))?;
+        let pieces = ss.sketch.exact_pieces(ci);
+        if pieces.is_empty() {
+            return Err(DocError::Invalid(format!("curve `{id}` has no exact geometry to build on")));
+        }
+        let lengths: Vec<f64> = pieces.iter().map(Seg2::length).collect();
+        let total: f64 = lengths.iter().sum();
+        if !total.is_finite() || total <= 1e-9 {
+            return Err(DocError::Invalid(format!("curve `{id}` has no length")));
+        }
+        let mut pts = Vec::with_capacity(samples);
+        let (mut used, mut at) = (0.0, 0usize);
+        for k in 0..samples {
+            let want = total * k as f64 / (samples.saturating_sub(1)).max(1) as f64;
+            while at + 1 < pieces.len() && used + lengths[at] < want {
+                used += lengths[at];
+                at += 1;
+            }
+            let (Some(piece), Some(len)) = (pieces.get(at), lengths.get(at)) else { return Err(DocError::Invalid("boundary piece".into())) };
+            let t = ((want - used) / len.max(1e-12)).clamp(0.0, 1.0);
+            pts.push(ss.plane.to_world(piece.point_at(t)));
+        }
+        sides.push(pts);
+    }
+    // The middle of the loop, so every side leaves towards the inside of the patch.
+    let count = sides.iter().map(Vec::len).sum::<usize>().max(1) as f64;
+    let centre = sides.iter().flatten().fold(solidcraft_geom::Vec3::ZERO, |a, p| a + *p) * (1.0 / count);
+    let mut out = Vec::with_capacity(sides.len());
+    for (side, pts) in sides.iter().enumerate() {
+        let mut frames = Vec::with_capacity(pts.len());
+        for (i, p) in pts.iter().enumerate() {
+            // The tangent from the stations on either side, one-sided at the ends (where the side
+            // only has one neighbour).
+            let before = if i == 0 { *p } else { pts[i - 1] };
+            let after = if i + 1 == pts.len() { *p } else { pts[i + 1] };
+            let tangent = (after - before).normalized().ok_or_else(|| DocError::Invalid("a boundary curve has a stationary station".into()))?;
+            let across = centre - *p;
+            let leave = (across - tangent * across.dot(tangent))
+                .normalized()
+                .ok_or_else(|| DocError::Invalid("a boundary runs through the middle of the loop: no patch can leave it".into()))?;
+            frames.push(Frame { p: *p, leave, bend: Vec3::ZERO, bend_change: Vec3::ZERO });
+        }
+        out.push(Boundary { frames, order: orders.get(side).copied().unwrap_or(solidcraft_kernel::Continuity::G1) });
+    }
+    Ok(out)
+}
+
 /// What a surface builder sweeps: the boundary loops of the picked profiles, then the picked
 /// curves chained end to end.
 fn sheet_chains(ss: &SolvedSketch, profiles: Option<&ProfileSel>, curves: &[String]) -> Result<Vec<Vec<Seg2>>> {
@@ -328,6 +503,9 @@ fn sheet_chains(ss: &SolvedSketch, profiles: Option<&ProfileSel>, curves: &[Stri
 
 /// Most sketch curves one feature chains.
 const MAX_CHAIN_CURVES: usize = 1000;
+/// Stations a blend samples each of its two boundaries at: enough that the boundary it fits is
+/// within a small part of a thousandth of the chain's length of the edges it was built on.
+const BLEND_STATIONS: usize = 41;
 
 /// The sketch curves `ids` (free-form ones exactly where they can be) grouped into chains of segments that meet end to end, each oriented
 /// to run one way. Curves are joined greedily at their free ends: where three meet, one of them

crates/doc/src/expr.rs

@@ -15,6 +15,94 @@ const MAX_LEN: usize = 4096;
 const MAX_DEPTH: usize = 64;
 const MAX_ARGS: usize = 64;
 
+/// An expression a feature holds, as the user wrote it (`2 * width + 5 mm`): kept as text and
+/// evaluated with the design's parameters. It is saved as a plain string, and reads as one
+/// (`&expr` is a `&str`); it changes only as a whole (`*expr = new.into()`).
+#[derive(Clone, Debug, Default, PartialEq, Eq, Hash, PartialOrd, Ord, serde::Serialize, serde::Deserialize)]
+#[serde(transparent)]
+pub struct Expr(String);
+
+impl Expr {
+    pub fn new(s: impl Into<String>) -> Self {
+        Expr(s.into())
+    }
+
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    pub fn into_string(self) -> String {
+        self.0
+    }
+}
+
+impl std::ops::Deref for Expr {
+    type Target = str;
+    fn deref(&self) -> &str {
+        &self.0
+    }
+}
+
+impl AsRef<str> for Expr {
+    fn as_ref(&self) -> &str {
+        &self.0
+    }
+}
+
+impl From<String> for Expr {
+    fn from(s: String) -> Self {
+        Expr(s)
+    }
+}
+
+impl From<&str> for Expr {
+    fn from(s: &str) -> Self {
+        Expr(s.to_string())
+    }
+}
+
+impl From<&String> for Expr {
+    fn from(s: &String) -> Self {
+        Expr(s.clone())
+    }
+}
+
+impl From<Expr> for String {
+    fn from(e: Expr) -> Self {
+        e.0
+    }
+}
+
+impl std::fmt::Display for Expr {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&self.0)
+    }
+}
+
+impl PartialEq<str> for Expr {
+    fn eq(&self, other: &str) -> bool {
+        self.0 == other
+    }
+}
+
+impl PartialEq<&str> for Expr {
+    fn eq(&self, other: &&str) -> bool {
+        self.0 == *other
+    }
+}
+
+impl PartialEq<Expr> for String {
+    fn eq(&self, other: &Expr) -> bool {
+        *self == other.0
+    }
+}
+
+impl PartialEq<String> for Expr {
+    fn eq(&self, other: &String) -> bool {
+        &self.0 == other
+    }
+}
+
 /// What an expression must evaluate to.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
 #[serde(rename_all = "snake_case")]
@@ -237,6 +325,8 @@ fn lex_spans(s: &str) -> Result<Vec<(Tok, usize, usize)>, DocError> {
     let at = |i: usize| cs.get(i).map(|x| x.0).unwrap_or(s.len());
     let mut i = 0;
     let mut out = Vec::new();
+    // Parentheses open at this point: a comma outside them can only be a decimal comma.
+    let mut depth = 0usize;
     while let Some(&(_, c)) = cs.get(i) {
         if c.is_whitespace() {
             i += 1;
@@ -245,6 +335,17 @@ fn lex_spans(s: &str) -> Result<Vec<(Tok, usize, usize)>, DocError> {
             while cs.get(i).is_some_and(|(_, c)| c.is_ascii_digit() || *c == '.') {
                 i += 1;
             }
+            // A decimal comma (`2,5 mm`, as typed with a numeric keypad in many locales, #1347):
+            // a comma between digits, in a number with no point, outside any parentheses (inside
+            // them a comma separates a function's arguments: `max(1,2)`).
+            let digit = |k: usize| cs.get(k).is_some_and(|(_, c)| c.is_ascii_digit());
+            let has_point = cs.get(st..i).is_some_and(|ds| ds.iter().any(|(_, c)| *c == '.'));
+            if depth == 0 && !has_point && digit(i.wrapping_sub(1)) && cs.get(i).is_some_and(|(_, c)| *c == ',') && digit(i + 1) {
+                i += 1;
+                while digit(i) {
+                    i += 1;
+                }
+            }
             // Exponent: 1e-3 (but not `2em`).
             if cs.get(i).is_some_and(|(_, c)| *c == 'e' || *c == 'E') {
                 let sign = cs.get(i + 1).is_some_and(|(_, c)| *c == '-' || *c == '+');
@@ -257,7 +358,7 @@ fn lex_spans(s: &str) -> Result<Vec<(Tok, usize, usize)>, DocError> {
                 }
             }
             let t = s.get(at(st)..at(i)).unwrap_or_default();
-            let v: f64 = t.parse().map_err(|_| DocError::Expr(format!("bad number `{t}`")))?;
+            let v: f64 = t.replace(',', ".").parse().map_err(|_| DocError::Expr(format!("bad number `{t}`")))?;
             out.push((Tok::Num(v), at(st), at(i)));
         } else if c.is_alphabetic() || c == '_' || c == 'µ' {
             let st = i;
@@ -268,6 +369,13 @@ fn lex_spans(s: &str) -> Result<Vec<(Tok, usize, usize)>, DocError> {
         } else if c == '°' {
             out.push((Tok::Id("deg".into()), at(i), at(i + 1)));
             i += 1;
+        } else if c == '"' || c == '″' {
+            // Inch and foot marks (`1"`, `2'`, #1502), straight or as primes.
+            out.push((Tok::Id("in".into()), at(i), at(i + 1)));
+            i += 1;
+        } else if c == '\'' || c == '′' {
+            out.push((Tok::Id("ft".into()), at(i), at(i + 1)));
+            i += 1;
         } else if c == '×' || c == '·' {
             out.push((Tok::Op('*'), at(i), at(i + 1)));
             i += 1;
@@ -282,6 +390,11 @@ fn lex_spans(s: &str) -> Result<Vec<(Tok, usize, usize)>, DocError> {
             out.push((Tok::Op(','), at(i), at(i + 1)));
             i += 1;
         } else if "+-*/^(),%".contains(c) {
+            match c {
+                '(' => depth += 1,
+                ')' => depth = depth.saturating_sub(1),
+                _ => {}
+            }
             out.push((Tok::Op(c), at(i), at(i + 1)));
             i += 1;
         } else {
@@ -819,6 +932,39 @@ mod tests {
         ParamDef { name: n.into(), expr: e.into(), unit: u.into() }
     }
 
+    #[test]
+    fn a_decimal_comma_outside_parentheses() {
+        // #1347: a comma between digits is a decimal comma where it cannot separate arguments.
+        assert_eq!(ev("2,5", Kind::Unitless).unwrap(), 2.5);
+        assert_eq!(ev("2,5 mm", Kind::Length).unwrap(), 2.5);
+        assert_eq!(ev("12,75mm + 0,25", Kind::Length).unwrap(), 13.0);
+        assert_eq!(ev("width / 2,5", Kind::Length).unwrap(), 16.0);
+        assert!((ev("1,5e3 mm", Kind::Length).unwrap() - 1500.0).abs() < 1e-9);
+        assert!((ev("22,5 deg", Kind::Angle).unwrap() - 22.5f64.to_radians()).abs() < 1e-12);
+        // Inside parentheses a comma still separates a function's arguments.
+        assert_eq!(ev("max(1,2)", Kind::Unitless).unwrap(), 2.0);
+        assert_eq!(ev("max(1 mm, 3, 2)", Kind::Length).unwrap(), 3.0);
+        assert_eq!(ev("(2,5)", Kind::Unitless).ok(), None, "a comma inside parentheses is not a decimal comma");
+        // Not between two digits, or a second comma: still an error.
+        for bad in ["2,", ",5", "2 ,5", "2, 5", "1,5,3", "1.5,3"] {
+            assert!(ev(bad, Kind::Unitless).is_err(), "{bad}");
+        }
+    }
+
+    #[test]
+    fn inch_and_foot_marks() {
+        // #1502: `1"` in a millimetre design is an inch, `2'` two feet, straight or as primes.
+        assert_eq!(ev("1\"", Kind::Length).unwrap(), 25.4);
+        assert_eq!(ev("1″", Kind::Length).unwrap(), 25.4);
+        assert_eq!(ev("2'", Kind::Length).unwrap(), 609.6);
+        assert_eq!(ev("2′", Kind::Length).unwrap(), 609.6);
+        assert_eq!(ev("1/2\"", Kind::Length).unwrap(), 12.7);
+        assert_eq!(ev("width + 1\"", Kind::Length).unwrap(), 65.4);
+        assert_eq!(ev("2' + 3\"", Kind::Length).unwrap(), 685.8);
+        // A mark alone is its unit alone, as `in` is.
+        assert_eq!(ev("\"", Kind::Length).ok(), ev("in", Kind::Length).ok());
+    }
+
     #[test]
     fn arithmetic_and_units() {
         assert_eq!(ev("10", Kind::Length).unwrap(), 10.0);

crates/doc/src/face_anchor.rs

@@ -69,8 +69,12 @@ impl FaceAnchor {
         }
         let inverse = crate::mat_inverse(&self.author_frame(doc, author)?)
             .ok_or_else(|| DocError::Invalid("attached sketch author frame is invalid".into()))?;
-        let source =
-            EmbossFace { body: self.target.body.clone(), at: self.target.point, path: self.path.clone(), author_path: self.author_path.clone() };
+        let source = EmbossFace {
+            body: self.target.body.clone().into(),
+            at: crate::FacePick(self.target.point),
+            path: self.path.clone(),
+            author_path: self.author_path.clone(),
+        };
         Ok(crate::mat_mul(&inverse, &source.body_frame(doc, body)?))
     }
 }
@@ -78,7 +82,7 @@ impl FaceAnchor {
 pub fn plane_face_anchor(plane: &PlaneRef) -> Option<&FaceAnchor> {
     match plane {
         PlaneRef::Face { anchor, .. } => anchor.as_deref(),
-        PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } => plane_face_anchor(base),
+        PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } | PlaneRef::Flipped { base, .. } => plane_face_anchor(base),
         _ => None,
     }
 }
@@ -86,7 +90,7 @@ pub fn plane_face_anchor(plane: &PlaneRef) -> Option<&FaceAnchor> {
 fn has_face_reference(plane: &PlaneRef) -> bool {
     match plane {
         PlaneRef::Face { .. } => true,
-        PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } => has_face_reference(base),
+        PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } | PlaneRef::Flipped { base, .. } => has_face_reference(base),
         _ => false,
     }
 }
@@ -106,7 +110,9 @@ impl Document {
             }
             match plane {
                 PlaneRef::Face { anchor: Some(anchor), .. } => *plane = PlaneRef::Custom { plane: doc.resolve_face_anchor(anchor, author, state)? },
-                PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } => replace(doc, base, author, state, depth + 1)?,
+                PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } | PlaneRef::Flipped { base, .. } => {
+                    replace(doc, base, author, state, depth + 1)?
+                }
                 _ => {}
             }
             Ok(())
@@ -447,7 +453,7 @@ mod tests {
             .add_feature(
                 FeatureKind::Extrude {
                     thin: None,
-                    sketch: source,
+                    sketch: crate::SketchId(source),
                     profiles: crate::ProfileSel::Indices { indices: vec![0, 1] },
                     extent,
                     operation: crate::Operation::NewBody,
@@ -558,7 +564,7 @@ mod tests {
             .add_feature(
                 FeatureKind::Extrude {
                     thin: None,
-                    sketch: sk,
+                    sketch: crate::SketchId(sk),
                     profiles: crate::ProfileSel::All,
                     extent,
                     operation: crate::Operation::NewBody,

crates/doc/src/feature_refs.rs

@@ -5,15 +5,14 @@
 
 use std::collections::BTreeMap;
 
-use crate::FeatureKind;
 use crate::walk::Walk;
+use crate::{BodyName, FeatureKind, FeatureName, SketchId};
 
-/// A reference a feature holds: `S` is `&u64` or `&mut u64` (a sketch id), `N` is `&String` or
-/// `&mut String` (a feature or body name).
-pub(crate) enum Ref<S, N> {
+/// A reference a feature holds: `S` is `&SketchId` or `&mut SketchId`, and so on.
+pub(crate) enum Ref<S, F, B> {
     Sketch(S),
-    Feature(N),
-    Body(N),
+    Feature(F),
+    Body(B),
 }
 
 impl FeatureKind {
@@ -23,7 +22,7 @@ impl FeatureKind {
         let mut v = Vec::new();
         self.walk_refs(&mut |r| {
             if let Ref::Sketch(id) = r {
-                v.push(*id);
+                v.push(id.0);
             }
         });
         v
@@ -34,13 +33,13 @@ impl FeatureKind {
     pub fn remap_refs(&mut self, sketches: &BTreeMap<u64, u64>, names: &BTreeMap<String, String>) {
         self.walk_refs_mut(&mut |r| match r {
             Ref::Sketch(id) => {
-                if let Some(n) = sketches.get(id) {
-                    *id = *n;
+                if let Some(n) = sketches.get(&id.0) {
+                    *id = SketchId(*n);
                 }
             }
             Ref::Feature(name) => {
-                if let Some(n) = names.get(name) {
-                    *name = n.clone();
+                if let Some(n) = names.get(name.as_ref()) {
+                    *name = FeatureName(n.clone());
                 }
             }
             Ref::Body(_) => {}
@@ -51,9 +50,9 @@ impl FeatureKind {
     pub fn remap_bodies(&mut self, bodies: &BTreeMap<String, String>) {
         self.walk_refs_mut(&mut |r| {
             if let Ref::Body(name) = r
-                && let Some(n) = bodies.get(name)
+                && let Some(n) = bodies.get(name.as_ref())
             {
-                *name = n.clone();
+                *name = BodyName(n.clone());
             }
         });
     }

crates/doc/src/feature_walk_tests.rs

@@ -73,9 +73,9 @@ fn ref_record() -> String {
     out
 }
 
-/// A variant with a field that refers to a sketch (a field named `*sketch*` holding an id, sketch
-/// points or loft sections) must report it from `input_sketches`, or deleting the sketch leaves
-/// the feature broken. New variants are caught by the walk's exhaustive match; this catches a
+/// A variant with a field that refers to a sketch (a `SketchId`, sketch points or loft
+/// sections) must report it from `input_sketches`, or deleting the sketch leaves the feature
+/// broken. New variants are caught by the walk's exhaustive match; this catches a
 /// sketch field added to an existing variant (its fixture has to set it).
 /// Per fixture (with every reference and position set): the fields `transform_geometry` changes
 /// under a turn and a shift (every point, direction and plane it maps), the face points that name
@@ -107,7 +107,7 @@ fn geometry_record() -> String {
             out += &format!("  profiles: {}\n", profiles.join(", "));
         }
         if let Some(p) = kind.point_expr() {
-            out += &format!("  placement: {}\n", p.join(", "));
+            out += &format!("  placement: {}\n", p.iter().map(|e| e.as_str()).collect::<Vec<_>>().join(", "));
         }
     }
     out
@@ -151,8 +151,8 @@ fn input_sketches_lists_every_variant_with_a_sketch_field() {
             variant = t.split(|c: char| !c.is_alphanumeric()).next().unwrap_or("").to_lowercase();
             continue;
         }
-        let Some((name, ty)) = t.strip_prefix("pub ").unwrap_or(t).split_once(':') else { continue };
-        let refers = (name.contains("sketch") && ty.contains("u64")) || ty.contains("SketchPoints") || ty.contains("LoftSection");
+        let Some((_, ty)) = t.strip_prefix("pub ").unwrap_or(t).split_once(':') else { continue };
+        let refers = ty.contains("SketchId") || ty.contains("SketchPoints") || ty.contains("LoftSection");
         if refers && !t.starts_with("//") && !with_sketch.contains(&variant) {
             with_sketch.push(variant.clone());
         }

crates/doc/src/feature_walk_tests/fixtures.rs

@@ -75,10 +75,16 @@ pub(super) fn fixtures() -> Vec<(&'static str, Value)> {
         ("thread", json!({"type": "thread", "face": o, "length": "thread.length"})),
         ("loft", json!({"type": "loft", "sections": []})),
         ("sweep", json!({"type": "sweep", "sketch": 1, "profiles": {"type": "all"}, "path_sketch": 2, "path": ["l1"]})),
+        (
+            "sweep_options",
+            json!({"type": "sweep", "sketch": 1, "profiles": {"type": "all"}, "path_sketch": 2, "path": ["l1"],
+                "orientation": {"direction": [0, 1, 0]}, "twist": "sweep.twist", "scale": "sweep.scale"}),
+        ),
         ("shell", json!({"type": "shell", "faces": [o], "thickness": "shell.thickness"})),
         ("draft", json!({"type": "draft", "faces": [o], "angle": "draft.angle", "neutral": plane("draft_neutral"), "pull": [0, 0, 1]})),
         ("construction_plane", json!({"type": "construction_plane", "plane": plane("cplane")})),
         ("split", json!({"type": "split", "body": "B", "plane": plane("split")})),
+        ("split_line", json!({"type": "split", "body": "B", "plane": plane("split_line")})),
         (
             "construction_axis",
             json!({"type": "construction_axis", "def": {"type": "two_planes", "a": geo_plane("axis_a"), "b": geo_plane("axis_b")}}),
@@ -109,7 +115,7 @@ pub(super) fn fixtures() -> Vec<(&'static str, Value)> {
         ("sheet_contour", json!({"type": "sheet_contour", "sketch": 1, "curves": ["l1"], "distance": "contour.distance"})),
         (
             "sheet_flange",
-            json!({"type": "sheet_flange", "edges": [{"point": o, "angle": "flange.e1_angle", "height": "flange.e1_height"}, {"point": o, "angle": null, "height": "flange.e2_height"}], "height": "flange.height", "angle": "flange.angle", "radius": "flange.radius"}),
+            json!({"type": "sheet_flange", "edges": [{"point": o, "angle": "flange.e1_angle", "height": "flange.e1_height"}, {"point": o, "angle": null, "height": "flange.e2_height"}], "height": "flange.height", "angle": "flange.angle", "radius": "flange.radius", "corner_relief_shape": "round", "corner_relief": "flange.relief"}),
         ),
         ("sheet_hem", json!({"type": "sheet_hem", "edges": [o], "length": "hem.length", "gap": "hem.gap"})),
         (
@@ -147,8 +153,19 @@ pub(super) fn fixtures() -> Vec<(&'static str, Value)> {
             json!({"type": "surface_revolve", "sketch": 1, "axis": {"type": "world", "axis": "X"}, "angle": "srev.angle", "angle2": "srev.angle2"}),
         ),
         ("surface_sweep", json!({"type": "surface_sweep", "sketch": 1, "path_sketch": 2, "path": ["l1"]})),
+        (
+            "surface_sweep_options",
+            json!({"type": "surface_sweep", "sketch": 1, "path_sketch": 2, "path": ["l1"],
+                "orientation": "parallel", "twist": "surface_sweep.twist", "scale": "surface_sweep.scale"}),
+        ),
         ("surface_loft", json!({"type": "surface_loft", "sections": []})),
+        ("surface_blend", json!({"type": "surface_blend", "from": {"body": "B", "edges": [o]}, "to": {"body": "C", "edges": [o]}, "align": [o, o]})),
         ("surface_offset", json!({"type": "surface_offset", "faces": [o], "distance": "soff.distance", "tolerance": "soff.tolerance"})),
+        // The Class-A surface family (surface.blend/boundary/match/fair).
+        ("surface_blend", json!({"type": "surface_blend", "from": {"body": "B", "edges": [o]}, "to": {"body": "C", "edges": [o]}, "align": [o, o]})),
+        ("surface_boundary", json!({"type": "surface_boundary", "sketch": 1, "curves": ["l1", "l2"]})),
+        ("surface_match", json!({"type": "surface_match", "body": "B", "faces": [o], "target": "C", "edges": [o]})),
+        ("surface_fair", json!({"type": "surface_fair", "body": "B", "faces": [o], "tolerance": "sfair.tolerance"})),
         ("unstitch", json!({"type": "unstitch", "body": "B"})),
         ("reverse_normal", json!({"type": "reverse_normal", "body": "B"})),
         ("surface_untrim", json!({"type": "surface_untrim", "face": {"body": "B", "point": o}, "holes": [o], "outer": true})),
@@ -181,7 +198,7 @@ pub(super) fn with_refs(name: &str, mut v: Value) -> Value {
     let o = [0, 0, 0];
     let tool = json!({"body": "B", "point": o});
     let extra = match name {
-        "extrude" | "extrude_thin" | "revolve" | "sweep" | "pipe" | "coil" | "thicken" => json!({"targets": ["B"]}),
+        "extrude" | "extrude_thin" | "revolve" | "sweep" | "sweep_options" | "pipe" | "coil" | "thicken" => json!({"targets": ["B"]}),
         "fillet_constant" | "fillet_chord" | "fillet_curvature" | "fillet_variable" | "fillet_spline" | "chamfer" | "shell" | "draft"
         | "offset_face" | "delete_face" | "replace_face" | "sheet_flange" | "sheet_hem" | "sheet_perforate" | "sheet_unfold" | "boss" | "lip"
         | "snap_fit" | "rest" | "surface_offset" => {
@@ -192,6 +209,7 @@ pub(super) fn with_refs(name: &str, mut v: Value) -> Value {
         "hole_simple" | "hole_drilled" | "hole_counterbore" | "hole_countersink" => json!({"points": {"sketch": 3, "ids": ["p"]}}),
         "loft" => json!({"sections": [{"sketch": 4, "profiles": {"type": "all"}}, {"sketch": 5, "profiles": {"type": "all"}}], "targets": ["B"]}),
         "split" | "surface_trim" => json!({"tool": tool}),
+        "split_line" => json!({"sketch": 6, "line": "l1"}),
         "surface_loft" => json!({"sections": [{"sketch": 4}, {"sketch": 5}]}),
         "split_face" => json!({"body": "B", "tool": tool, "sketch": 6}),
         "emboss" => json!({"face": {"body": "B", "at": o}, "targets": ["B"]}),

crates/doc/src/feature_walk_tests/golden_exprs.txt

@@ -136,6 +136,11 @@ thread
   expressions: thread.length
 loft
 sweep
+sweep_options
+  inputs:
+    Twist = sweep.twist (Angle)
+    Scale = sweep.scale (Unitless)
+  expressions: sweep.twist, sweep.scale
 shell
   inputs:
     Thickness = shell.thickness (Length)
@@ -156,6 +161,11 @@ split
     Angle = split.angle (Angle)
     Offset = split.offset (Length)
   expressions: split.angle, split.offset
+split_line
+  inputs:
+    Angle = split_line.angle (Angle)
+    Offset = split_line.offset (Length)
+  expressions: split_line.angle, split_line.offset
 construction_axis
   inputs:
     Angle = axis_a.angle (Angle)
@@ -238,7 +248,8 @@ sheet_flange
     Edge angle = flange.e1_angle (Angle)
     Edge height = flange.e1_height (Length)
     Edge height = flange.e2_height (Length)
-  expressions: flange.height, flange.angle, flange.radius, flange.e1_angle, flange.e1_height, flange.e2_height
+    Corner relief = flange.relief (Length)
+  expressions: flange.height, flange.angle, flange.radius, flange.e1_angle, flange.e1_height, flange.e2_height, flange.relief
 sheet_hem
   inputs:
     Length = hem.length (Length)
@@ -317,12 +328,25 @@ surface_revolve
     Angle 2 = srev.angle2 (Angle)
   expressions: srev.angle, srev.angle2
 surface_sweep
+surface_sweep_options
+  inputs:
+    Twist = surface_sweep.twist (Angle)
+    Scale = surface_sweep.scale (Unitless)
+  expressions: surface_sweep.twist, surface_sweep.scale
 surface_loft
+surface_blend
 surface_offset
   inputs:
     Distance = soff.distance (Length)
     Tolerance = soff.tolerance (Length)
   expressions: soff.distance, soff.tolerance
+surface_blend
+surface_boundary
+surface_match
+surface_fair
+  inputs:
+    Tolerance = sfair.tolerance (Length)
+  expressions: sfair.tolerance
 unstitch
 reverse_normal
 surface_untrim

crates/doc/src/feature_walk_tests/golden_geometry.txt

@@ -63,6 +63,9 @@ loft
   profiles: 4 all, 5 all
 sweep
   profiles: 1 all
+sweep_options
+  moves: orientation.direction[1], orientation.direction[2]
+  profiles: 1 all
 shell
   moves: faces[0][0], faces[0][1], faces[0][2]
   face points: [0, 0, 0]
@@ -73,6 +76,8 @@ construction_plane
   moves: plane.axis_dir[0], plane.axis_dir[1], plane.axis_origin[0], plane.axis_origin[1], plane.axis_origin[2]
 split
   moves: plane.axis_dir[0], plane.axis_dir[1], plane.axis_origin[0], plane.axis_origin[1], plane.axis_origin[2], tool.point[0], tool.point[1], tool.point[2]
+split_line
+  moves: plane.axis_dir[0], plane.axis_dir[1], plane.axis_origin[0], plane.axis_origin[1], plane.axis_origin[2]
 construction_axis
   moves: def.a.plane.axis_dir[0], def.a.plane.axis_dir[1], def.a.plane.axis_origin[0], def.a.plane.axis_origin[1], def.a.plane.axis_origin[2], def.b.plane.axis_dir[0], def.b.plane.axis_dir[1], def.b.plane.axis_origin[0], def.b.plane.axis_origin[1], def.b.plane.axis_origin[2]
 construction_point_planes
@@ -142,10 +147,22 @@ surface_extrude
 surface_revolve
   moves: axis.dir[0], axis.dir[1], axis.dir[2], axis.origin[0], axis.origin[1], axis.origin[2]
 surface_sweep
+surface_sweep_options
 surface_loft
+surface_blend
+  moves: align[0][0], align[0][1], align[0][2], align[1][0], align[1][1], align[1][2], from.edges[0][0], from.edges[0][1], from.edges[0][2], to.edges[0][0], to.edges[0][1], to.edges[0][2]
 surface_offset
   moves: faces[0][0], faces[0][1], faces[0][2]
   face points: [0, 0, 0]
+surface_blend
+  moves: align[0][0], align[0][1], align[0][2], align[1][0], align[1][1], align[1][2], from.edges[0][0], from.edges[0][1], from.edges[0][2], to.edges[0][0], to.edges[0][1], to.edges[0][2]
+surface_boundary
+surface_match
+  moves: edges[0][0], edges[0][1], edges[0][2], faces[0][0], faces[0][1], faces[0][2]
+  face points: [0, 0, 0]
+surface_fair
+  moves: faces[0][0], faces[0][1], faces[0][2]
+  face points: [0, 0, 0]
 unstitch
   moves: faces[0][0], faces[0][1], faces[0][2]
 reverse_normal

crates/doc/src/feature_walk_tests/golden_refs.txt

@@ -67,6 +67,10 @@ sweep
   sketches: [1, 2]
   remap_refs: path_sketch, sketch
   remap_bodies: targets[0]
+sweep_options
+  sketches: [1, 2]
+  remap_refs: path_sketch, sketch
+  remap_bodies: targets[0]
 shell
   remap_bodies: body
 draft
@@ -77,6 +81,10 @@ construction_plane
 split
   remap_refs: plane.base.base.name
   remap_bodies: body, tool.body
+split_line
+  sketches: [6]
+  remap_refs: plane.base.base.name, sketch
+  remap_bodies: body
 construction_axis
 construction_point_planes
 construction_point_along
@@ -159,11 +167,25 @@ surface_revolve
 surface_sweep
   sketches: [1, 2]
   remap_refs: path_sketch, sketch
+surface_sweep_options
+  sketches: [1, 2]
+  remap_refs: path_sketch, sketch
 surface_loft
   sketches: [4, 5]
   remap_refs: sections[0].sketch, sections[1].sketch
+surface_blend
+  remap_bodies: from.body
 surface_offset
   remap_bodies: body
+surface_blend
+  remap_bodies: from.body
+surface_boundary
+  sketches: [1]
+  remap_refs: sketch
+surface_match
+  remap_bodies: body
+surface_fair
+  remap_bodies: body
 unstitch
   remap_bodies: body
 reverse_normal

crates/doc/src/format.rs

@@ -191,13 +191,142 @@
 //!   A bend point can also lie on a bend modelled with its radius (a cylinder between two flat
 //!   faces tangent to it), which then is one bend at the two faces' virtual sharp with the
 //!   rule's radius; 0.11.0 found no edge there or refused the curved face.
+//!   Also under 21, a Sweep and a Surface Sweep can carry `orientation` (`parallel`, or
+//!   `{direction: [x, y, z]}`; absent: perpendicular), `twist` (an angle expression) and `scale`
+//!   (the end scale, an expression). A sweep without them saves as before; 0.11.x refuses
+//!   format 21, so no released build sweeps a twisted or scaled profile straight.
+//!   Nothing new is saved for converted sheets' corners and bend ends, but a design converts as
+//!   the rule says when it is evaluated: corners between the walls take the rule's corner relief
+//!   and a bend ending beside more of the fixed face its bend relief (0.11.0 left every corner a
+//!   notch and cut no bend relief), and a wall on part of an edge bends only where it stands
+//!   (0.11.0 refused it).
+//! - 22: an Import (STEP) feature can list `skip`: indices of the file's bodies it does not
+//!   build, because they are later instances of a part the file places more than once and the
+//!   other occurrences of that part's component show them (#1386: an imported file becomes a
+//!   component, an assembly in it nested components). Version 21 designs need no
+//!   transformation: an Import without it builds every body, as it always did, and designs
+//!   whose imports sit loose in a component are left as they are. The version stamp makes
+//!   0.12.0 (which reads up to 21) ask for an update instead of building those instances again
+//!   on top of their occurrences.
+//!   Also under 22, a number in an expression can be written with a decimal comma outside
+//!   parentheses (`2,5 mm` is `2.5 mm`, #1347; inside a function's parentheses the comma still
+//!   separates its arguments). Nothing new is saved, but an expression typed that way is saved as
+//!   typed; 0.12.0 asks for an update instead of failing to evaluate it.
+//!   Also under 22, a design can hold a `SurfaceBlend` (Blend Surface: `from`/`to` edge chains of
+//!   two bodies, optional `continuity`, `bulge`, `align`, `stitch`), and a `Patch` can carry a
+//!   `crown` (0 by default, and then not saved: a bump that vanishes on the loop, so the face
+//!   still meets the picked edges). Version 21 designs need no transformation; 0.12.0 asks for an
+//!   update instead of meeting a feature it can't read or dropping a patch's crown.
+//!   Also under 22, a sketch text's link source can say that its place, height or angle are
+//!   expressions (`exprs`: `x`, `y`, `height`, `angle`, each an expression over the design's
+//!   parameters); the source's `at`, `height` and `angle` then hold the numbers they last came
+//!   to. A text without `exprs` is set as it always was; 0.12.0 asks for an update instead of
+//!   dropping the expressions and keeping the text at its last numbers.
+//!
+//! Later formats are one file per change, so changes made side by side never edit the same line
+//! (`src/format/pending/README.md`):
+//! - `src/format/v<N>/`: the changes format N added, one file each, its `//!` note saying what is
+//!   saved and what older designs get, and a `step` when older designs are rewritten as they open
+//!   (23: motion link couplings, FreeCAD and Rhino imports; 24: an Edge Flange's own corner relief).
+//! - `src/format/pending/`: changes no release has fixed a number for yet. While there are any,
+//!   this build writes the next number (which no release reads), with the names of these changes
+//!   in `format_pending`, so a later build applies just the steps a file is missing. At release
+//!   time `scripts/fold-format-pending.sh` moves them into the next `v<N>/`.
 
 use serde_json::Value;
 
 use crate::{DocError, Document, Result};
 
-/// The format this build writes.
-pub const FORMAT: u32 = 21;
+/// The format this build writes: the last folded one, or the next while changes are pending.
+pub const FORMAT: u32 = FORMATS.current();
+
+/// The last format whose upgrade step is written out in [`JSON_STEPS`]; later formats are made
+/// of [`Part`]s (`src/format/`, listed by `build.rs`).
+const HAND_WRITTEN: u32 = 22;
+
+/// One change to the file format: a file in `src/format/v<N>/` or `src/format/pending/`.
+pub(crate) struct Part {
+    /// The file's name, which a file written while the change was pending lists.
+    pub name: &'static str,
+    /// How a design from before the change is rewritten as it opens, if it is.
+    pub step: Option<JsonStep>,
+}
+
+include!(concat!(env!("OUT_DIR"), "/format_parts.rs"));
+
+/// Every format this build knows and how to upgrade a design through them.
+const FORMATS: Formats<'static> = Formats { hand: &JSON_STEPS, folded: FOLDED, pending: PENDING };
+
+/// The names of the pending changes this build writes into a design (`format_pending`).
+pub fn pending_names() -> Vec<String> {
+    FORMATS.pending.iter().map(|p| p.name.to_string()).collect()
+}
+
+/// The upgrade path: the hand-written steps up to [`HAND_WRITTEN`], the folded formats after it
+/// (each a list of changes) and the pending changes, which make the next format.
+struct Formats<'a> {
+    hand: &'a [JsonStep],
+    folded: &'a [(u32, &'a [Part])],
+    pending: &'a [Part],
+}
+
+impl Formats<'_> {
+    const fn current(&self) -> u32 {
+        self.hand.len() as u32 + 1 + self.folded.len() as u32 + if self.pending.is_empty() { 0 } else { 1 }
+    }
+
+    /// The changes format `version` is made of, if it is made of changes.
+    fn parts(&self, version: u32) -> Option<&[Part]> {
+        let after = version.checked_sub(self.hand.len() as u32 + 2)? as usize;
+        match self.folded.get(after) {
+            Some((_, parts)) => Some(parts),
+            None if after == self.folded.len() && !self.pending.is_empty() => Some(self.pending),
+            None => None,
+        }
+    }
+
+    /// Bring a design of format `version` up to [`Formats::current`]. `applied` is the file's
+    /// `format_pending`: the changes of its format it already has, when it was written while they
+    /// were pending; the others' steps run first. A pending change this build doesn't have is a
+    /// newer build's, and the design is refused.
+    fn upgrade(&self, v: &mut Value, version: u32, applied: Option<&[String]>) -> Result<()> {
+        if version == 0 || version > self.current() {
+            return Err(DocError::Invalid(format!("not a SolidCraft design (format {version})")));
+        }
+        // A list beside a format that isn't made of changes means nothing (a tool or a test set
+        // an older number on a newer file): it is ignored, like any field an upgrade drops.
+        if let (Some(applied), Some(parts)) = (applied, self.parts(version)) {
+            let pending = version == self.current() && !self.pending.is_empty();
+            if let Some(unknown) = applied.iter().find(|name| pending && !parts.iter().any(|p| p.name == name.as_str())) {
+                return Err(DocError::Invalid(format!(
+                    "this design was saved by a newer SolidCraft (file format {version} with `{unknown}`, which this version doesn't know): update SolidCraft to open it"
+                )));
+            }
+            for part in parts.iter().filter(|p| !applied.iter().any(|name| name == p.name)) {
+                part.step.map_or(Ok(()), |step| step(v))?;
+            }
+        }
+        for from in version..self.current() {
+            match self.hand.get(from as usize - 1) {
+                Some(step) => step(v)?,
+                None => {
+                    for part in self.parts(from + 1).unwrap_or_default() {
+                        part.step.map_or(Ok(()), |step| step(v))?;
+                    }
+                }
+            }
+        }
+        Ok(())
+    }
+}
+
+/// Take a file's `format_pending` (the pending changes it has) out of its JSON.
+fn take_pending(v: &mut Value) -> Result<Option<Vec<String>>> {
+    let Some(list) = v.as_object_mut().and_then(|o| o.remove("format_pending")) else { return Ok(None) };
+    let invalid = || DocError::Invalid("damaged design: `format_pending` is not a short list of names".into());
+    let list = list.as_array().filter(|l| l.len() <= 1000).ok_or_else(invalid)?;
+    list.iter().map(|n| n.as_str().filter(|n| n.len() <= 128).map(str::to_string).ok_or_else(invalid)).collect::<Result<_>>().map(Some)
+}
 
 pub fn format_string(n: u32) -> String {
     format!("solidcraft/{n}")
@@ -212,9 +341,10 @@ pub fn version_of(s: &str) -> Option<u32> {
     s.strip_prefix("solidcraft/").or_else(|| s.strip_prefix(LEGACY_FORMAT_PREFIX))?.parse().ok()
 }
 
-/// JSON-level upgrades: entry `i` turns format `i + 1` into `i + 2`.
+/// JSON-level upgrades up to [`HAND_WRITTEN`]: entry `i` turns format `i + 1` into `i + 2`.
+/// Never add to it: a new format is a file in `src/format/pending/`.
 type JsonStep = fn(&mut Value) -> Result<()>;
-const JSON_STEPS: [JsonStep; 20] = [
+const JSON_STEPS: [JsonStep; HAND_WRITTEN as usize - 1] = [
     |_| Ok(()),
     v2_to_v3,
     v3_to_v4,
@@ -235,6 +365,7 @@ const JSON_STEPS: [JsonStep; 20] = [
     |_| Ok(()),
     |_| Ok(()),
     |_| Ok(()),
+    |_| Ok(()),
 ];
 
 /// Stored face and edge names were worked out from geometry before format 14; they get the
@@ -425,6 +556,7 @@ pub fn read(s: &str) -> Result<Document> {
         Some(Value::String(f)) => version_of(f).ok_or_else(|| DocError::Invalid(format!("not a SolidCraft design (format `{f}`)")))?,
         Some(_) => return Err(DocError::Invalid("not a SolidCraft design (format is not a string)".into())),
     };
+    let applied = take_pending(&mut v)?;
     if version == 0 {
         return Err(DocError::Invalid("not a SolidCraft design (format 0)".into()));
     }
@@ -444,9 +576,7 @@ pub fn read(s: &str) -> Result<Document> {
     crate::format_offsets::validate_raw(&v)?;
     let legacy_wires = validate_wires(&v, version)?;
     validate_body_transfers(&v)?;
-    for step in JSON_STEPS.iter().skip(version as usize - 1).take((FORMAT - version) as usize) {
-        step(&mut v)?;
-    }
+    FORMATS.upgrade(&mut v, version, applied.as_deref())?;
     let mut d: Document = serde_json::from_value(v).map_err(|e| DocError::Invalid(format!("design file: {e}")))?;
     let mut legacy_by_feature = std::collections::BTreeMap::<usize, Vec<usize>>::new();
     for (feature, wire) in legacy_wires {
@@ -545,6 +675,7 @@ pub fn read(s: &str) -> Result<Document> {
     let floor = largest.checked_add(1).ok_or_else(|| DocError::Invalid("damaged design: the id space is exhausted".into()))?;
     d.next_id = d.next_id.max(floor).max(1);
     d.format = format_string(FORMAT);
+    d.format_pending = pending_names();
     Ok(d)
 }
 
@@ -967,6 +1098,170 @@ fn normalise(d: &mut Document) -> Result<()> {
 mod tests {
     use super::*;
 
+    /// A pending change that records that its step ran, in `trace`.
+    fn traced(name: &'static str) -> Part {
+        fn step_a(v: &mut Value) -> Result<()> {
+            trace(v, "a")
+        }
+        fn step_b(v: &mut Value) -> Result<()> {
+            trace(v, "b")
+        }
+        fn trace(v: &mut Value, s: &str) -> Result<()> {
+            let o = v.as_object_mut().ok_or_else(|| DocError::Invalid("no object".into()))?;
+            o.entry("trace").or_insert_with(|| Value::Array(Vec::new())).as_array_mut().into_iter().for_each(|t| t.push(Value::from(s)));
+            Ok(())
+        }
+        Part { name, step: Some(if name.starts_with('a') { step_a } else { step_b }) }
+    }
+
+    fn trace_of(v: &Value) -> Vec<&str> {
+        v["trace"].as_array().into_iter().flatten().filter_map(Value::as_str).collect()
+    }
+
+    /// Formats after the hand-written ones follow on from them, one folder each, and the build
+    /// writes the next number exactly while changes are pending, so the last release (which
+    /// reads up to 22) refuses what a development build saves.
+    #[test]
+    fn formats_follow_on_and_pending_changes_take_the_next_number() {
+        assert_eq!(JSON_STEPS.len() as u32, HAND_WRITTEN - 1);
+        for (i, (version, parts)) in FOLDED.iter().enumerate() {
+            assert_eq!(*version, HAND_WRITTEN + 1 + i as u32);
+            assert!(!parts.is_empty(), "format {version} has no changes");
+        }
+        let last_folded = HAND_WRITTEN + FOLDED.len() as u32;
+        assert_eq!(FORMAT, last_folded + u32::from(!PENDING.is_empty()));
+        const { assert!(FORMAT >= 24, "designs saved as 23 and 24 by nightlies still open") };
+        assert_eq!(pending_names(), PENDING.iter().map(|p| p.name).collect::<Vec<_>>());
+        assert_eq!(Document::new("A").format_pending, pending_names());
+    }
+
+    /// The build lists every change file there is, in file-name order: a change is a file, so
+    /// two branches that each add one merge cleanly and the merged build has both.
+    #[test]
+    fn every_change_file_is_listed_in_name_order() {
+        let root = std::path::Path::new(env!("CARGO_MANIFEST_DIR")).join("src/format");
+        let names = |dir: &str| -> Vec<String> {
+            let mut names: Vec<String> = std::fs::read_dir(root.join(dir))
+                .map(|d| d.filter_map(|e| e.ok()?.file_name().to_str()?.strip_suffix(".rs").map(str::to_string)).collect())
+                .unwrap_or_default();
+            names.sort();
+            names
+        };
+        assert_eq!(names("pending"), pending_names());
+        for (version, parts) in FOLDED {
+            assert_eq!(names(&format!("v{version}")), parts.iter().map(|p| p.name).collect::<Vec<_>>());
+        }
+    }
+
+    /// Two changes pending side by side both run, in name order, after every older format's
+    /// steps: an old design upgrades through all of them, and one from the last folded format
+    /// gets just the pending ones.
+    #[test]
+    fn pending_changes_apply_in_order_after_older_formats() {
+        let pending = [traced("a-first"), traced("b-second")];
+        let formats = Formats { hand: &JSON_STEPS, folded: FOLDED, pending: &pending };
+        let next = HAND_WRITTEN + FOLDED.len() as u32 + 1;
+        assert_eq!(formats.current(), next);
+        for version in [1, HAND_WRITTEN, next - 1] {
+            let mut v = serde_json::json!({"features": [], "assembly": {"joints": [{"flip": false}]}});
+            formats.upgrade(&mut v, version, None).unwrap();
+            assert_eq!(trace_of(&v), ["a", "b"], "from format {version}");
+            // The hand-written steps ran too: format 3's joints were flipped on the way up.
+            assert_eq!(v["assembly"]["joints"][0]["flip"], Value::Bool(version < 4), "from format {version}");
+        }
+        // A design of the pending number written before `b-second` existed gets just that step.
+        let mut v = serde_json::json!({});
+        formats.upgrade(&mut v, next, Some(&["a-first".to_string()])).unwrap();
+        assert_eq!(trace_of(&v), ["b"]);
+        // One that has both, or that this build wrote, needs nothing.
+        let mut v = serde_json::json!({});
+        formats.upgrade(&mut v, next, Some(&["a-first".into(), "b-second".into()])).unwrap();
+        assert_eq!(trace_of(&v), Vec::<&str>::new());
+        // A change this build doesn't know is a newer build's: refused, not guessed at.
+        let err = formats.upgrade(&mut serde_json::json!({}), next, Some(&["c-later".into()])).unwrap_err();
+        assert!(err.to_string().contains("newer SolidCraft"), "{err}");
+        // A list on a format that isn't made of changes means nothing.
+        let mut v = serde_json::json!({});
+        formats.upgrade(&mut v, HAND_WRITTEN, Some(&["a-first".into()])).unwrap();
+        assert_eq!(trace_of(&v), ["a", "b"]);
+    }
+
+    /// Folding the pending changes into a number (the release script) keeps every design
+    /// opening the same: a file saved while they were pending gets the steps it missed.
+    #[test]
+    fn folded_changes_upgrade_like_pending_ones() {
+        let parts = [traced("a-first"), traced("b-second")];
+        let mut folded: Vec<(u32, &[Part])> = FOLDED.to_vec();
+        let next = HAND_WRITTEN + folded.len() as u32 + 1;
+        folded.push((next, &parts));
+        let formats = Formats { hand: &JSON_STEPS, folded: &folded, pending: &[] };
+        assert_eq!(formats.current(), next);
+        let mut old = serde_json::json!({});
+        formats.upgrade(&mut old, HAND_WRITTEN, None).unwrap();
+        assert_eq!(trace_of(&old), ["a", "b"]);
+        let mut nightly = serde_json::json!({});
+        formats.upgrade(&mut nightly, next, Some(&["a-first".into()])).unwrap();
+        assert_eq!(trace_of(&nightly), ["b"]);
+        let mut released = serde_json::json!({});
+        formats.upgrade(&mut released, next, None).unwrap();
+        assert_eq!(trace_of(&released), Vec::<&str>::new());
+    }
+
+    /// `format_pending` is read and checked: a damaged list is refused, a list of changes this
+    /// build doesn't have is a newer build's, and saving writes this build's own list.
+    #[test]
+    fn format_pending_in_a_file_is_checked() {
+        let mut file: Value = serde_json::from_str(&Document::new("A").to_json()).unwrap();
+        assert_eq!(file.get("format_pending").is_some(), !PENDING.is_empty());
+        for damaged in [serde_json::json!("x"), serde_json::json!([1]), serde_json::json!(["x".repeat(200)])] {
+            file["format_pending"] = damaged;
+            assert!(read(&file.to_string()).is_err());
+        }
+        file["format_pending"] = serde_json::json!(["not-a-change-anyone-made"]);
+        assert_eq!(read(&file.to_string()).is_err(), !PENDING.is_empty(), "only a pending format's list names changes");
+        file["format_pending"] = Value::from(pending_names());
+        let opened = read(&file.to_string()).unwrap();
+        assert_eq!(opened.format_pending, pending_names());
+    }
+
+    /// 24 added the corner relief of an edge flange: a no-op step carries a 23 design up, a flange
+    /// without a relief of its own saves as before, and one with it is saved under 24 and kept.
+    #[test]
+    fn version_twenty_three_designs_open_and_an_edge_flange_relief_is_saved_in_twenty_four() {
+        let flange = |shape: Option<&str>, size: Option<&str>| crate::FeatureKind::SheetFlange {
+            edges: vec![crate::FlangeEdge::at(solidcraft_geom::Vec3::ZERO)],
+            height: "10 mm".into(),
+            angle: "90 deg".into(),
+            radius: None,
+            position: "inside".into(),
+            flip: false,
+            body: None,
+            corner_relief_shape: shape.map(Into::into),
+            corner_relief: size.map(Into::into),
+        };
+        let saved = |document: &Document| -> Value { serde_json::from_str(&document.to_json()).unwrap() };
+        // A flange that follows the rule saves neither key, and a design of format 23 opens as it was.
+        let mut plain = Document::new("A");
+        plain.add_feature(flange(None, None), None).unwrap();
+        let mut file = saved(&plain);
+        let feature = file["features"].as_array().and_then(|f| f.last()).cloned().unwrap();
+        assert_eq!(feature["type"], "sheet_flange");
+        assert!(feature.get("corner_relief_shape").is_none() && feature.get("corner_relief").is_none(), "{feature}");
+        file["format"] = Value::from("solidcraft/23");
+        let opened = read(&file.to_string()).unwrap();
+        assert_eq!(opened.format, format_string(FORMAT));
+        assert_eq!(opened.features, plain.features);
+        // One that chooses its relief says so in the file, which is stamped 24 and keeps it.
+        let mut own = Document::new("A");
+        own.add_feature(flange(Some("round"), Some("6 mm")), None).unwrap();
+        let file = saved(&own);
+        let feature = file["features"].as_array().and_then(|f| f.last()).cloned().unwrap();
+        assert_eq!((&feature["corner_relief_shape"], &feature["corner_relief"]), (&Value::from("round"), &Value::from("6 mm")));
+        // A build that reads up to 23 asks for an update on that stamp instead of dropping the relief.
+        assert_eq!(version_of(file["format"].as_str().unwrap_or_default()), Some(FORMAT));
+        assert_eq!(read(&file.to_string()).unwrap(), own);
+    }
+
     #[test]
     fn version_thirteen_names_keep_their_meaning_under_the_legacy_mark() {
         let file = serde_json::json!({
@@ -1140,7 +1435,7 @@ mod tests {
             .add_feature(
                 FeatureKind::Extrude {
                     thin: None,
-                    sketch,
+                    sketch: crate::SketchId(sketch),
                     profiles: ProfileSel::All,
                     extent: Extent {
                         convention: crate::ExtrudeConvention::LegacyPerSide,
@@ -1150,9 +1445,9 @@ mod tests {
                         start_offset: None,
                         through_all: false,
                         taper: Some("0 deg".into()),
-                        to: Some(solidcraft_geom::Vec3::new(0.0, 0.0, 10.0)),
+                        to: Some(crate::FacePick(solidcraft_geom::Vec3::new(0.0, 0.0, 10.0))),
                         to_offset: Some("offset + 1 mm".into()),
-                        from: Some(solidcraft_geom::Vec3::new(0.0, 0.0, 5.0)),
+                        from: Some(crate::FacePick(solidcraft_geom::Vec3::new(0.0, 0.0, 5.0))),
                     },
                     operation: Operation::NewBody,
                     targets: vec![],
@@ -1763,4 +2058,28 @@ mod tests {
         let json = edited(&d, |v| v["components"][1]["id"] = u64::MAX.into());
         assert!(read(&json).unwrap_err().to_string().contains("damaged design"));
     }
+
+    /// A sweep saved before its options existed loads as a plain sweep and saves as it was; the
+    /// options round-trip.
+    #[test]
+    fn sweep_options_are_optional_and_round_trip() {
+        use crate::{FeatureKind, SweepOrientation};
+        let old =
+            serde_json::json!({"type": "sweep", "sketch": 1, "profiles": {"type": "all"}, "path_sketch": 2, "path": ["l1"], "operation": "new_body"});
+        let k: FeatureKind = serde_json::from_value(old.clone()).unwrap();
+        let FeatureKind::Sweep { orientation, twist, scale, .. } = &k else { panic!("{k:?}") };
+        assert!(orientation.is_perpendicular() && twist.is_none() && scale.is_none());
+        assert_eq!(serde_json::to_value(&k).unwrap(), old);
+        let old = serde_json::json!({"type": "surface_sweep", "sketch": 1, "path_sketch": 2, "path": ["l1"]});
+        let k: FeatureKind = serde_json::from_value(old.clone()).unwrap();
+        assert_eq!(serde_json::to_value(&k).unwrap(), old);
+        let new = serde_json::json!({"type": "surface_sweep", "sketch": 1, "path_sketch": 2, "path": ["l1"],
+            "orientation": {"direction": [0.0, 1.0, 0.0]}, "twist": "90 deg", "scale": "0.5"});
+        let k: FeatureKind = serde_json::from_value(new.clone()).unwrap();
+        let FeatureKind::SurfaceSweep { orientation, .. } = &k else { panic!("{k:?}") };
+        assert_eq!(*orientation, SweepOrientation::Direction(crate::Dir(solidcraft_geom::Vec3::Y)));
+        assert_eq!(serde_json::to_value(&k).unwrap(), new);
+        let parallel: SweepOrientation = serde_json::from_value(serde_json::json!("parallel")).unwrap();
+        assert_eq!(parallel, SweepOrientation::Parallel);
+    }
 }

crates/doc/src/format/pending/README.md

@@ -0,0 +1,27 @@
+# Pending design-format changes
+
+One file per change to what a design file saves that no release has shipped yet. Adding a file
+here is the whole format bump: never edit `FORMAT`, `JSON_STEPS` or another change's file.
+
+- Name it after the change, lowercase with dashes: `placed-plane-origins.rs`.
+- Start it with a `//!` note: what is saved, what an older design gets without it, and what
+  the last release does with a design that has it (it refuses the newer format number).
+- If older designs must be rewritten as they open, add the step to the same file:
+
+  ```rust
+  //! …the note…
+  use serde_json::Value;
+
+  pub fn step(v: &mut Value) -> crate::Result<()> {
+      // rewrite the design's JSON here
+      Ok(())
+  }
+  ```
+
+  Steps run in file-name order, after the steps of every older format.
+
+While this folder has a change in it, the build writes the next format number (the last
+folded one + 1, which no release reads), and lists the changes a file has in its
+`format_pending` field, so a later build applies only the steps that file is missing. At release
+time `scripts/fold-format-pending.sh` moves these files into `../v<N>/`, which fixes that number
+for good. See `crates/doc/src/format.rs` and CONTRIBUTING.md.

crates/doc/src/format/v23/import-fcstd-3dm.rs

@@ -0,0 +1,4 @@
+//! An Import's `file` can name a FreeCAD `.FCStd` or Rhino `.3dm` file (#1435, read through
+//! cadmpeg); its `step` is still the STEP text the file was restated as, so the feature's fields
+//! are unchanged and version 22 designs need no transformation; 0.13.x asks for an update before
+//! it meets these imports.

crates/doc/src/format/v23/motion-link-coupling.rs

@@ -0,0 +1,7 @@
+//! A motion link can carry a `coupling`: a gear pair (`ra`, `rb`, `internal`), a rack and pinion
+//! (`radius`) or a screw (`pitch`), each size a number in mm, an expression or a picked round
+//! face, and `reverse`. The link's `ratio` is worked out from it whenever the design changes and
+//! saved as well, so a link reads the same without it. Version 22 designs need no
+//! transformation: a link without `coupling` is a plain motion link, as it always was; 0.13.0
+//! (which reads up to 22) asks for an update instead of keeping a gear's ratio when its radius
+//! changes.

crates/doc/src/format/v24/edge-flange-corner-relief.rs

@@ -0,0 +1,5 @@
+//! An Edge Flange feature can choose its own corner relief (`corner_relief_shape`: notch, round,
+//! rectangular or tear, and `corner_relief`, the size across), for the corners its flanges make.
+//! Version 23 designs need no transformation: a feature without them follows the sheet metal
+//! rule, as it always did, and saves as before; 0.13.0 (which reads up to 22) asks for an update
+//! instead of silently building the rule's relief where a design asks for another.

crates/doc/src/format/v25/class-a-surfaces.rs

@@ -0,0 +1,5 @@
+//! The Class-A surface pass adds `SurfaceBoundary` (Boundary Surface: `sketch`, `curves`,
+//! optional `orders`, `crown`, `samples`), `SurfaceMatch` (Match Surface: `body`, optional
+//! `faces`, `target`, `edges`, optional `order`) and `SurfaceFair` (Fair Surface: `body`, optional
+//! `faces`, `strength`, `iterations`, `keep_edges`, `tolerance`). Older designs need no
+//! transformation; 0.13.x asks for an update instead of meeting a feature it can't read.

crates/doc/src/format/v25/feature-pattern-alignment.rs

@@ -0,0 +1,4 @@
+//! Rectangular and circular feature patterns store alignment and reversal, independently for
+//! each rectangular direction. Defaults preserve older positive-direction placements.
+//! Center retains the source and alternates copies on either side, as sketch patterns do.
+//! The last release refuses this pending format and asks for an update instead of losing it.

crates/doc/src/format/v25/flipped-sketch-plane.rs

@@ -0,0 +1,5 @@
+//! A sketch can sit on a plane seen from its other side: `{"type": "flipped", "base": <plane>}`
+//! (with `"about_y": true` when it turns about the plane's y axis rather than its x axis). New
+//! sketches started from behind an origin or construction plane save this, so they face the
+//! viewer. Older designs have no flipped planes and open unchanged; the last release refuses a
+//! design that has one (it asks for an update) instead of putting the sketch on the wrong side.

crates/doc/src/format/v25/infinite-sketch-lines.rs

@@ -0,0 +1,5 @@
+//! A sketch line can be `infinite` (#1359): construction geometry through its two points, drawn
+//! across the whole view, a boundary for trim and extend along its whole line. Saved only when
+//! set: older designs need no transformation, and a line without it is the line it always was;
+//! 0.13.x (which reads up to 24) asks for an update instead of drawing such a line between its
+//! two points.

crates/doc/src/format/v25/patch-continuity-and-points.rs

@@ -0,0 +1,6 @@
+//! A `Patch` on edges can carry `continuity` (`all`: `g0`, `g1` or `g2`, and `edges`:
+//! `[{edge: [x, y, z], g}]` for edges met otherwise; G0 everywhere when absent, and then not
+//! saved) and `points` it passes through (none when absent). Older designs need no
+//! transformation: a patch without them fills as it always did; a loop that is not a height field
+//! over its plane, which 0.13.0 refused, now fills with one face. 0.13.x asks for an update
+//! instead of dropping them.

crates/doc/src/format/v25/placed-plane-origins.rs

@@ -0,0 +1,4 @@
+//! An explicit plane (a mirror's, or any plane reference) can be `placed`: an `origin` of three
+//! length expressions with `x_dir` and `y_dir`, so it follows the design's parameters (#1492). A
+//! plane whose origin is plain numbers is still saved as `custom`. Older designs need no
+//! transformation; 0.13.x asks for an update instead of failing to read the plane.

crates/doc/src/format/v25/sketch-pattern-directions.rs

@@ -0,0 +1,5 @@
+//! Sketch linear patterns save two independent live direction-line references and each
+//! direction's alignment and reversal. Even centered totals keep the original fixed and use
+//! reversal to choose which side receives the extra copy. Older patterns retain their fixed
+//! vectors and positive-direction placement through defaulted fields, so no rewrite is needed.
+//! The last release refuses this pending format instead of silently losing the references.

crates/doc/src/format/v25/split-by-sketch-line.rs

@@ -0,0 +1,4 @@
+//! A Split Body feature can take a straight sketch line as its tool (`sketch`, the sketch's
+//! feature id, and `line`, the line's id), splitting by the plane through the line along the
+//! sketch's normal (#1552). Older designs need no transformation: a split without them uses its
+//! plane or face as before; 0.13.x asks for an update instead of splitting by the stored plane.

crates/doc/src/format_offsets.rs

@@ -424,7 +424,7 @@ mod tests {
                 .add_feature(
                     FeatureKind::Extrude {
                         thin: None,
-                        sketch: if missing_sketch { 999_999 } else { id },
+                        sketch: crate::SketchId(if missing_sketch { 999_999 } else { id }),
                         profiles: ProfileSel::OffsetBoundaries { associations: vec!["deleted-o1".into()] },
                         extent: crate::Extent {
                             convention: crate::ExtrudeConvention::LegacyPerSide,

crates/doc/src/joints.rs

@@ -1,7 +1,8 @@
 //! Joints between occurrences: joint origins (snap frames on component geometry, re-found on
 //! every solve so they follow edits), joints (rigid, revolute, slider, cylindrical, pin-slot,
-//! planar, ball) with their motion values and limits, motion links, and the solver that places
-//! occurrences from the joint graph.
+//! planar, ball) with their motion values and limits, motion links (gears, racks and screws are
+//! links whose ratio comes from radii or a pitch), and the solver that places occurrences from
+//! the joint graph.
 //!
 //! A joint makes B's joint frame coincide with A's frame moved by the joint's motion:
 //! `T_B · F_b = T_A · F_a · M(q) · Flip`, so `T_B = T_A · F_a · M(q) · Flip · F_b⁻¹`, where `T`
@@ -151,6 +152,115 @@ pub struct MotionLink {
     pub ratio: f64,
     #[serde(default)]
     pub offset: f64,
+    /// Gears, a rack and pinion or a screw: what the ratio comes from. The ratio is worked out
+    /// from it again whenever the design changes (`coupling_ratio`), so it follows the radii and
+    /// the pitch; the last one worked out is kept in `ratio`.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub coupling: Option<Coupling>,
+}
+
+/// A length a coupling's ratio comes from: millimetres, an expression over the design's
+/// parameters, or the radius of the round face picked on an occurrence (a circle-centre snap,
+/// found again on every solve like a joint origin).
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(untagged)]
+pub enum Size {
+    Length(f64),
+    Expr(String),
+    Circle(JointOrigin),
+}
+
+/// The geometry a motion link's ratio comes from. `reverse` turns the follower the other way.
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(tag = "type", rename_all = "snake_case")]
+pub enum Coupling {
+    /// Two gears on revolute joints, `ra` on a's and `rb` on b's (pitch radii, or any two lengths
+    /// in their proportion such as tooth counts): b turns ra/rb as far as a, the other way round,
+    /// or the same way when one is an internal (ring) gear.
+    Gear {
+        ra: Size,
+        rb: Size,
+        #[serde(default, skip_serializing_if = "std::ops::Not::not")]
+        internal: bool,
+        #[serde(default, skip_serializing_if = "std::ops::Not::not")]
+        reverse: bool,
+    },
+    /// A pinion of pitch radius `radius` on a revolute joint and a rack on a slider: the rack
+    /// travels the radius times the pinion's turn in radians (either joint may drive).
+    RackPinion {
+        radius: Size,
+        #[serde(default, skip_serializing_if = "std::ops::Not::not")]
+        reverse: bool,
+    },
+    /// A screw: the travel advances `pitch` per turn (a cylindrical joint's angle and distance,
+    /// or a revolute joint and a slider). Right-handed unless reversed.
+    Screw {
+        pitch: Size,
+        #[serde(default, skip_serializing_if = "std::ops::Not::not")]
+        reverse: bool,
+    },
+}
+
+impl Coupling {
+    /// The lengths the ratio comes from: a's gear and b's, or the pinion's radius or the pitch.
+    pub fn sizes(&self) -> Vec<&Size> {
+        match self {
+            Coupling::Gear { ra, rb, .. } => vec![ra, rb],
+            Coupling::RackPinion { radius: s, .. } | Coupling::Screw { pitch: s, .. } => vec![s],
+        }
+    }
+
+    pub fn sizes_mut(&mut self) -> Vec<&mut Size> {
+        match self {
+            Coupling::Gear { ra, rb, .. } => vec![ra, rb],
+            Coupling::RackPinion { radius: s, .. } | Coupling::Screw { pitch: s, .. } => vec![s],
+        }
+    }
+}
+
+/// Largest length a coupling takes (mm).
+const MAX_SIZE: f64 = 1e7;
+
+/// A coupling length in millimetres: positive and finite.
+fn size_of(doc: &Document, st: &ModelState, s: &Size) -> Result<f64> {
+    let v = match s {
+        Size::Length(v) => *v,
+        Size::Expr(e) => doc.eval(e, crate::expr::Kind::Length)?,
+        Size::Circle(o) => circle_at(doc, st, o)?.1.radius,
+    };
+    if v.is_finite() && v > 1e-9 && v <= MAX_SIZE {
+        Ok(v)
+    } else {
+        Err(DocError::Invalid(format!("a gear, rack or screw needs a positive length, not {v}")))
+    }
+}
+
+/// The ratio a link's coupling gives it (b's value per a's, in radians and mm), worked out from
+/// the geometry and parameters it is defined by; `None` for a plain link.
+pub fn coupling_ratio(doc: &Document, st: &ModelState, l: &MotionLink) -> Option<Result<f64>> {
+    l.coupling.as_ref().map(|c| coupled(doc, st, l, c))
+}
+
+fn coupled(doc: &Document, st: &ModelState, l: &MotionLink, c: &Coupling) -> Result<f64> {
+    let angle = |id: u64, i: usize| doc.assembly.joints.iter().find(|j| j.id == id).is_some_and(|j| j.kind.is_angle(i));
+    let (turn_a, turn_b) = (angle(l.a, l.ia), angle(l.b, l.ib));
+    // Travel per radian, for a turn coupled to a travel either way round.
+    let travel = |k: f64| match (turn_a, turn_b) {
+        (true, false) => Ok(k),
+        (false, true) => Ok(1.0 / k),
+        _ => Err(DocError::Invalid("a rack or a screw couples a turn and a travel".into())),
+    };
+    let sign = |reverse: bool| if reverse { -1.0 } else { 1.0 };
+    match c {
+        Coupling::Gear { ra, rb, internal, reverse } => {
+            if !(turn_a && turn_b) {
+                return Err(DocError::Invalid("gears couple two turns".into()));
+            }
+            Ok(size_of(doc, st, ra)? / size_of(doc, st, rb)? * sign(!internal) * sign(*reverse))
+        }
+        Coupling::RackPinion { radius, reverse } => Ok(travel(size_of(doc, st, radius)?)? * sign(*reverse)),
+        Coupling::Screw { pitch, reverse } => Ok(travel(size_of(doc, st, pitch)? / std::f64::consts::TAU)? * sign(*reverse)),
+    }
 }
 
 /// Joints, joint origins and motion links of a design.
@@ -272,27 +382,35 @@ pub fn resolve_origin(doc: &Document, st: &ModelState, o: &JointOrigin) -> Resul
             let (_, c, n) = best.ok_or_else(|| DocError::Invalid("joint origin: no planar face there".into()))?;
             frame(c, n, None).ok_or_else(bad)
         }
-        Snap::CircleCenter { pick, face } => {
-            let pick = &named_pick(st, *pick, face.as_deref())?;
-            let comp = component_of(doc, o.occurrence)?;
-            let cyl = component_bodies(doc, st, comp)
-                .into_iter()
-                .filter_map(|b| solidcraft_kernel::cylinder_face_at(&b.body, *pick))
-                .min_by(|a, b| {
-                    let off = |c: &solidcraft_kernel::CylinderFace| {
-                        let v = *pick - c.axis_point;
-                        ((v - c.axis * v.dot(c.axis)).len() - c.radius).abs()
-                    };
-                    off(a).total_cmp(&off(b))
-                })
-                .ok_or_else(|| DocError::Invalid("joint origin: no cylindrical face there".into()))?;
-            let s = (*pick - cyl.axis_point).dot(cyl.axis);
+        Snap::CircleCenter { .. } => {
+            let (pick, cyl) = circle_at(doc, st, o)?;
+            let s = (pick - cyl.axis_point).dot(cyl.axis);
             let (at, dir) = if (s - cyl.start).abs() <= (cyl.end - s).abs() { (cyl.start, -1.0) } else { (cyl.end, 1.0) };
             frame(cyl.axis_point + cyl.axis * at, cyl.axis * dir, None).ok_or_else(bad)
         }
     }
 }
 
+/// The pick of a circle-centre snap (on its named face) and the cylindrical face there
+/// (component coordinates). Any other snap is refused.
+fn circle_at(doc: &Document, st: &ModelState, o: &JointOrigin) -> Result<(Vec3, solidcraft_kernel::CylinderFace)> {
+    let Snap::CircleCenter { pick, face } = &o.snap else { return Err(DocError::Invalid("pick a round face".into())) };
+    let pick = named_pick(st, *pick, face.as_deref())?;
+    let comp = component_of(doc, o.occurrence)?;
+    let cyl = component_bodies(doc, st, comp)
+        .into_iter()
+        .filter_map(|b| solidcraft_kernel::cylinder_face_at(&b.body, pick))
+        .min_by(|a, b| {
+            let off = |c: &solidcraft_kernel::CylinderFace| {
+                let v = pick - c.axis_point;
+                ((v - c.axis * v.dot(c.axis)).len() - c.radius).abs()
+            };
+            off(a).total_cmp(&off(b))
+        })
+        .ok_or_else(|| DocError::Invalid("joint origin: no cylindrical face there".into()))?;
+    Ok((pick, cyl))
+}
+
 /// World transform of an occurrence (through its parents).
 pub fn occurrence_world(doc: &Document, occ: u64) -> Mat {
     let mut m = IDENTITY;
@@ -624,6 +742,16 @@ fn unknowns(tree: &Tree, around: &BTreeSet<u64>, asm: &Assembly, linked: &BTreeS
     vars
 }
 
+/// Each value's limits, or none.
+fn limit_bounds(tree: &Tree, vars: &[(u64, usize)]) -> Vec<(f64, f64)> {
+    vars.iter()
+        .map(|(id, i)| match tree.joints.get(id).and_then(|j| j.limits.get(*i).copied().flatten()) {
+            Some((lo, hi)) => (lo.min(hi), hi.max(lo)),
+            None => (f64::NEG_INFINITY, f64::INFINITY),
+        })
+        .collect()
+}
+
 /// The loops' size: the diagonal of the box around their joints' A frames, 1 mm to 1 km. Points
 /// that far apart weigh turns like moves.
 fn loop_scale(tree: &Tree, around: &BTreeSet<u64>, vals: &Values) -> f64 {
@@ -658,11 +786,72 @@ fn closure_gaps(tree: &Tree, closing: &[u64], vals: &Values, scale: f64, out: &m
 /// keep the tree's count.
 const MAX_DOF_OCCURRENCES: usize = 256;
 
+/// How far `nearby_pose` moves each value: radians for an angle, a share of the loops' size for a
+/// distance. Far enough for a part's motion that vanishes at a dead point to show in a rank, near
+/// enough to stay on the mechanism's branch.
+const NUDGE: f64 = 1e-3;
+
+/// A pose of the loops near `vals`: each value they move nudged by an amount of its own within
+/// its limits (so the nudge points in no special direction), then each group of loops closed
+/// again. A group that can't close again, or only further away than a few nudges (on another
+/// branch), keeps its values. It has a work budget of its own.
+fn nearby_pose(tree: &Tree, groups: &[Group], asm: &Assembly, linked: &BTreeSet<(u64, usize)>, vals: &Values) -> Values {
+    let mut near = vals.clone();
+    let mut spent = 0usize;
+    for (closing, around, _) in groups {
+        let vars = unknowns(tree, around, asm, linked, &Held::new());
+        if vars.is_empty() || vars.len() > MAX_LOOP_VALUES {
+            continue;
+        }
+        let scale = loop_scale(tree, around, vals);
+        let step: Vec<f64> =
+            vars.iter().map(|(id, i)| NUDGE * if tree.joints.get(id).is_some_and(|j| j.kind.is_angle(*i)) { 1.0 } else { scale }).collect();
+        let bounds = limit_bounds(tree, &vars);
+        let x0: Vec<f64> = vars.iter().map(|(id, i)| near.get(id).and_then(|q| q.get(*i)).copied().unwrap_or(0.0)).collect();
+        let mut x: Vec<f64> = x0
+            .iter()
+            .zip(step.iter().zip(&bounds))
+            .enumerate()
+            .map(|(k, (v, (d, (lo, hi))))| {
+                // 0.5 to 1.5 nudges, alternately up and down.
+                let w = 0.5 + (k as f64 * 0.618_034).fract();
+                (v + d * if k % 2 == 0 { w } else { -w }).max(*lo).min(*hi)
+            })
+            .collect();
+        let mut work = near.clone();
+        let mut gaps = |x: &[f64]| -> Option<Vec<f64>> {
+            spent += 1;
+            if spent > MAX_LOOP_WORK {
+                return None;
+            }
+            for ((id, i), v) in vars.iter().zip(x) {
+                if let Some(slot) = work.get_mut(id).and_then(|q| q.get_mut(*i)) {
+                    *slot = *v;
+                }
+            }
+            apply_links(asm, &mut work);
+            let mut out = Vec::with_capacity(closing.len() * 9);
+            closure_gaps(tree, closing, &work, scale, &mut out)?;
+            out.iter().all(|v| v.is_finite()).then_some(out)
+        };
+        if least_squares(&mut gaps, &mut x, &bounds, (1e-10 * scale).min(1e-7))
+            && x.iter().zip(&x0).zip(&step).all(|((a, b), d)| (a - b).abs() <= 4.0 * d)
+            && gaps(&x).is_some()
+        {
+            near = work;
+        }
+    }
+    near
+}
+
 /// The degrees of freedom of the occurrences loops constrain: how many independent ways each can
 /// still move with every loop kept closed, the rank of its placement over the joint values once
 /// the loops' closure is taken out (rank [J_loops; J_placement] - rank J_loops). An occurrence's
-/// values are those on its tree path and the unknowns of the loops on that path. The tree's
-/// count stands where a loop group is over the solver's caps or the work runs out.
+/// values are those on its tree path and the unknowns of the loops on that path. It is counted at
+/// the pose and at a pose nearby, and the larger count stands: at a dead point of its loop (an
+/// actuator in line with the path of its tip pin) a part's motion vanishes to first order, so the
+/// pose alone counts 0. The tree's count stands where a loop group is over the solver's caps or
+/// the work runs out.
 fn loop_dof(tree: &Tree, closing: &[u64], asm: &Assembly, vals: &Values, dof: &mut BTreeMap<u64, usize>) {
     if closing.len() > MAX_LOOPS {
         return;
@@ -690,6 +879,8 @@ fn loop_dof(tree: &Tree, closing: &[u64], asm: &Assembly, vals: &Values, dof: &m
         }
     }
     let (mut spent, mut counted) = (0usize, 0usize);
+    // A pose nearby, when one differs.
+    let near = (!candidates.is_empty()).then(|| nearby_pose(tree, &groups, asm, &linked, vals)).filter(|n| n != vals);
     for occ in tree.order.iter().filter(|o| candidates.contains(o)) {
         let path: Vec<u64> = tree.path(*occ).1.iter().map(|(k, _)| *k).collect();
         let (mut values, mut have): (Vec<(u64, usize)>, BTreeSet<(u64, usize)>) = (Vec::new(), BTreeSet::new());
@@ -751,41 +942,47 @@ fn loop_dof(tree: &Tree, closing: &[u64], asm: &Assembly, vals: &Values, dof: &m
             continue;
         }
         let scale = loop_scale(tree, &around, vals);
-        let mut work = vals.clone();
-        // The loops' gaps, then three points of the occurrence `scale` apart.
-        let mut f = |x: &[f64]| -> Option<Vec<f64>> {
-            spent += 1;
-            for ((id, i), v) in values.iter().zip(x) {
-                if let Some(slot) = work.get_mut(id).and_then(|q| q.get_mut(*i)) {
-                    *slot = *v;
-                }
-            }
-            apply_links(asm, &mut work);
-            let mut out = Vec::with_capacity(closers.len() * 9 + 9);
-            closure_gaps(tree, &closers, &work, scale, &mut out)?;
-            let t = tree.world(*occ, &work)?;
-            for p in [Vec3::ZERO, Vec3::X * scale, Vec3::Y * scale] {
-                let q = apply_point(&t, p);
-                out.extend([q.x, q.y, q.z]);
-            }
-            out.iter().all(|v| v.is_finite()).then_some(out)
-        };
-        let x0: Vec<f64> = values.iter().map(|(id, i)| vals.get(id).and_then(|q| q.get(*i)).copied().unwrap_or(0.0)).collect();
         let (n, gaps) = (values.len(), closers.len() * 9);
-        let Some(jac) = jacobian(&mut f, &x0, gaps + 9) else { continue };
-        let rank = |rows: usize| {
-            let mut a = linalg::Mat::zeros(rows, n);
-            let mut big = 0.0f64;
-            for r in 0..rows {
-                for c in 0..n {
-                    let v = jac.get(r * n + c).copied().unwrap_or(0.0);
-                    big = big.max(v.abs());
-                    a.set(r, c, v);
+        // How many ways the occurrence moves at a pose, with the loops kept closed.
+        let mut free_at = |at: &Values| -> Option<usize> {
+            let mut work = at.clone();
+            // The loops' gaps, then three points of the occurrence `scale` apart.
+            let mut f = |x: &[f64]| -> Option<Vec<f64>> {
+                spent += 1;
+                for ((id, i), v) in values.iter().zip(x) {
+                    if let Some(slot) = work.get_mut(id).and_then(|q| q.get_mut(*i)) {
+                        *slot = *v;
+                    }
                 }
-            }
-            linalg::rref(&mut a, 1e-6 * big.max(1.0)).len()
+                apply_links(asm, &mut work);
+                let mut out = Vec::with_capacity(closers.len() * 9 + 9);
+                closure_gaps(tree, &closers, &work, scale, &mut out)?;
+                let t = tree.world(*occ, &work)?;
+                for p in [Vec3::ZERO, Vec3::X * scale, Vec3::Y * scale] {
+                    let q = apply_point(&t, p);
+                    out.extend([q.x, q.y, q.z]);
+                }
+                out.iter().all(|v| v.is_finite()).then_some(out)
+            };
+            let x0: Vec<f64> = values.iter().map(|(id, i)| at.get(id).and_then(|q| q.get(*i)).copied().unwrap_or(0.0)).collect();
+            let jac = jacobian(&mut f, &x0, gaps + 9)?;
+            let rank = |rows: usize| {
+                let mut a = linalg::Mat::zeros(rows, n);
+                let mut big = 0.0f64;
+                for r in 0..rows {
+                    for c in 0..n {
+                        let v = jac.get(r * n + c).copied().unwrap_or(0.0);
+                        big = big.max(v.abs());
+                        a.set(r, c, v);
+                    }
+                }
+                linalg::rref(&mut a, 1e-6 * big.max(1.0)).len()
+            };
+            Some(rank(gaps + 9).saturating_sub(rank(gaps)))
         };
-        let free = rank(gaps + 9).saturating_sub(rank(gaps));
+        let here = free_at(vals);
+        let there = near.as_ref().and_then(&mut free_at);
+        let Some(free) = here.max(there) else { continue };
         dof.insert(*occ, free.min(6));
     }
 }
@@ -814,13 +1011,7 @@ fn close_group(
     if vars.len() > MAX_LOOP_VALUES {
         return Some(BTreeMap::new());
     }
-    let bounds: Vec<(f64, f64)> = vars
-        .iter()
-        .map(|(id, i)| match tree.joints.get(id).and_then(|j| j.limits.get(*i).copied().flatten()) {
-            Some((lo, hi)) => (lo.min(hi), hi.max(lo)),
-            None => (f64::NEG_INFINITY, f64::INFINITY),
-        })
-        .collect();
+    let bounds = limit_bounds(tree, &vars);
     let scale = loop_scale(tree, around, vals);
     // Closer than the conflict check needs: 1e-7 mm, and turns of 1e-10 rad across the loop.
     let tol = (1e-10 * scale).min(1e-7);
@@ -1020,72 +1211,8 @@ pub fn solve(doc: &Document, st: &ModelState) -> Solution {
 pub fn solve_holding(doc: &Document, st: &ModelState, held: &Held) -> Solution {
     let asm = &doc.assembly;
     let mut sol = Solution::default();
-    let joints: Vec<&Joint> = asm.joints.iter().filter(|j| !j.suppressed).take(MAX_JOINTS).collect();
     let mut vals = joint_values(asm);
-    // Joint frames in component coordinates (errors leave the joint out).
-    let mut frames: BTreeMap<u64, (Mat, Mat)> = BTreeMap::new();
-    for j in &joints {
-        match (resolve_origin(doc, st, &j.a), resolve_origin(doc, st, &j.b)) {
-            (Ok(fa), Ok(fb)) => {
-                frames.insert(j.id, (fa, fb));
-            }
-            (Err(e), _) | (_, Err(e)) => sol.errors.push((j.id, j.name.clone(), e.to_string())),
-        }
-    }
-    // Fixed: the root, grounded occurrences; with neither involved, the first joint's A side.
-    let mut placed: BTreeMap<u64, Mat> = BTreeMap::new();
-    let mut dof: BTreeMap<u64, usize> = BTreeMap::new();
-    placed.insert(0, IDENTITY);
-    dof.insert(0, 0);
-    for o in doc.occurrences.iter().filter(|o| o.grounded) {
-        placed.insert(o.id, occurrence_world(doc, o.id));
-        dof.insert(o.id, 0);
-    }
-    let involved: BTreeSet<u64> = joints.iter().flat_map(|j| [j.a.occurrence, j.b.occurrence]).collect();
-    if !involved.iter().any(|o| placed.contains_key(o))
-        && let Some(j) = joints.first()
-    {
-        placed.insert(j.a.occurrence, occurrence_world(doc, j.a.occurrence));
-        dof.insert(j.a.occurrence, 0);
-    }
-    sol.fixed = placed.keys().copied().collect();
-    let mut tree =
-        // Every joint's values are known, suppressed ones too (their motion links still set values).
-        Tree { joints: asm.joints.iter().map(|j| (j.id, j)).collect(), frames, fixed: placed.clone(), parent: BTreeMap::new(), order: Vec::new() };
-    let mut used: BTreeSet<u64> = BTreeSet::new();
-    let mut queue: VecDeque<u64> = placed.keys().copied().collect();
-    while let Some(occ) = queue.pop_front() {
-        let Some(t) = placed.get(&occ).copied() else { continue };
-        for j in &joints {
-            if used.contains(&j.id) || !tree.frames.contains_key(&j.id) {
-                continue;
-            }
-            let (other, from_a) = if j.a.occurrence == occ {
-                (j.b.occurrence, true)
-            } else if j.b.occurrence == occ {
-                (j.a.occurrence, false)
-            } else {
-                continue;
-            };
-            if placed.contains_key(&other) {
-                continue;
-            }
-            let Some(m) = tree.step(j.id, from_a, &t, &vals) else { continue };
-            used.insert(j.id);
-            placed.insert(other, m);
-            tree.parent.insert(other, (occ, j.id, from_a));
-            tree.order.push(other);
-            dof.insert(other, dof.get(&occ).copied().unwrap_or(0) + j.kind.dofs().len());
-            queue.push_back(other);
-        }
-    }
-    // Joints that close loops: move the loops' values to meet them, then check they agree.
-    let closing: Vec<u64> = joints
-        .iter()
-        .filter(|j| !used.contains(&j.id) && tree.frames.contains_key(&j.id))
-        .filter(|j| placed.contains_key(&j.a.occurrence) && placed.contains_key(&j.b.occurrence))
-        .map(|j| j.id)
-        .collect();
+    let Built { tree, mut placed, closing, mut dof } = build(doc, st, &vals, &mut sol);
     let mut stuck = BTreeSet::new();
     if !closing.is_empty() {
         (sol.values, stuck) = close_loops(&tree, &closing, asm, held, &mut vals);
@@ -1123,6 +1250,99 @@ pub fn solve_holding(doc: &Document, st: &ModelState, held: &Held) -> Solution {
     sol
 }
 
+/// The joint graph laid out for a solve: the tree, where it places each occurrence for the
+/// values it was built with, the joints that close loops, and each occurrence's degrees of
+/// freedom along the tree.
+struct Built<'a> {
+    tree: Tree<'a>,
+    placed: BTreeMap<u64, Mat>,
+    closing: Vec<u64>,
+    dof: BTreeMap<u64, usize>,
+}
+
+/// Lay out the joint graph: the spanning tree out from the fixed occurrences (the root, grounded
+/// ones; with neither involved, the first joint's A side) and the joints left over, which close
+/// loops. Joints whose origins can't be resolved go to `sol.errors`; `sol.fixed` is set.
+fn build<'a>(doc: &'a Document, st: &ModelState, vals: &Values, sol: &mut Solution) -> Built<'a> {
+    let asm = &doc.assembly;
+    let joints: Vec<&Joint> = asm.joints.iter().filter(|j| !j.suppressed).take(MAX_JOINTS).collect();
+    // Joint frames in component coordinates (errors leave the joint out).
+    let mut frames: BTreeMap<u64, (Mat, Mat)> = BTreeMap::new();
+    for j in &joints {
+        match (resolve_origin(doc, st, &j.a), resolve_origin(doc, st, &j.b)) {
+            (Ok(fa), Ok(fb)) => {
+                frames.insert(j.id, (fa, fb));
+            }
+            (Err(e), _) | (_, Err(e)) => sol.errors.push((j.id, j.name.clone(), e.to_string())),
+        }
+    }
+    // Fixed: the root, grounded occurrences; with neither involved, the first joint's A side.
+    let mut placed: BTreeMap<u64, Mat> = BTreeMap::new();
+    let mut dof: BTreeMap<u64, usize> = BTreeMap::new();
+    placed.insert(0, IDENTITY);
+    dof.insert(0, 0);
+    for o in doc.occurrences.iter().filter(|o| o.grounded) {
+        placed.insert(o.id, occurrence_world(doc, o.id));
+        dof.insert(o.id, 0);
+    }
+    let involved: BTreeSet<u64> = joints.iter().flat_map(|j| [j.a.occurrence, j.b.occurrence]).collect();
+    if !involved.iter().any(|o| placed.contains_key(o))
+        && let Some(j) = joints.first()
+    {
+        placed.insert(j.a.occurrence, occurrence_world(doc, j.a.occurrence));
+        dof.insert(j.a.occurrence, 0);
+    }
+    sol.fixed = placed.keys().copied().collect();
+    let mut tree =
+        // Every joint's values are known, suppressed ones too (their motion links still set values).
+        Tree { joints: asm.joints.iter().map(|j| (j.id, j)).collect(), frames, fixed: placed.clone(), parent: BTreeMap::new(), order: Vec::new() };
+    let mut used: BTreeSet<u64> = BTreeSet::new();
+    let mut queue: VecDeque<u64> = placed.keys().copied().collect();
+    // The joints at each occurrence, in the joints' order (a large assembly is not walked joint by
+    // joint for every occurrence).
+    let mut at: BTreeMap<u64, Vec<&Joint>> = BTreeMap::new();
+    for j in joints.iter().copied() {
+        at.entry(j.a.occurrence).or_default().push(j);
+        if j.b.occurrence != j.a.occurrence {
+            at.entry(j.b.occurrence).or_default().push(j);
+        }
+    }
+    while let Some(occ) = queue.pop_front() {
+        let Some(t) = placed.get(&occ).copied() else { continue };
+        for j in at.get(&occ).map(Vec::as_slice).unwrap_or_default() {
+            if used.contains(&j.id) || !tree.frames.contains_key(&j.id) {
+                continue;
+            }
+            let (other, from_a) = if j.a.occurrence == occ {
+                (j.b.occurrence, true)
+            } else if j.b.occurrence == occ {
+                (j.a.occurrence, false)
+            } else {
+                continue;
+            };
+            if placed.contains_key(&other) {
+                continue;
+            }
+            let Some(m) = tree.step(j.id, from_a, &t, vals) else { continue };
+            used.insert(j.id);
+            placed.insert(other, m);
+            tree.parent.insert(other, (occ, j.id, from_a));
+            tree.order.push(other);
+            dof.insert(other, dof.get(&occ).copied().unwrap_or(0) + j.kind.dofs().len());
+            queue.push_back(other);
+        }
+    }
+    // Joints that close loops: the solve moves the loops' values to meet them, then checks they
+    // agree.
+    let closing: Vec<u64> = joints
+        .iter()
+        .filter(|j| !used.contains(&j.id) && tree.frames.contains_key(&j.id))
+        .filter(|j| placed.contains_key(&j.a.occurrence) && placed.contains_key(&j.b.occurrence))
+        .map(|j| j.id)
+        .collect();
+    Built { tree, placed, closing, dof }
+}
+
 impl Document {
     /// Apply a solution: occurrence transforms (in their parents) for the occurrences it places,
     /// and the values of the joints that moved to close loops. Returns true when something moved.
@@ -1168,6 +1388,10 @@ impl Document {
     }
 }
 
+#[path = "joints_reach.rs"]
+mod reach;
+pub use reach::{REACH_TOL, Reach, Reached, reach};
+
 /// The frame matrix for an explicit origin / z / x (public for commands).
 pub fn frame_of(o: Vec3, z: Vec3, x: Option<Vec3>) -> Option<Mat> {
     frame(o, z, x)
@@ -1201,7 +1425,7 @@ mod tests {
                 suppressed: false,
             })
             .collect();
-        let links = (1..n).rev().map(|a| MotionLink { a, ia: 0, b: a + 1, ib: 0, ratio: 2.0, offset: 0.0 }).collect();
+        let links = (1..n).rev().map(|a| MotionLink { a, ia: 0, b: a + 1, ib: 0, ratio: 2.0, offset: 0.0, coupling: None }).collect();
         Assembly { joints, links, ..Assembly::default() }
     }
 
@@ -1224,6 +1448,53 @@ mod tests {
         assert_eq!(again, vals);
     }
 
+    /// A coupling saves as its definition: sizes as numbers, expressions or picked faces, flags
+    /// only when set; a link without one (as every design before couplings has) reads as before.
+    #[test]
+    fn couplings_read_and_write_their_definition() {
+        let old: MotionLink = serde_json::from_str(r#"{"a": 1, "b": 2, "ratio": 2}"#).unwrap();
+        assert_eq!((old.coupling, old.offset, old.ia), (None, 0.0, 0));
+        let text = r#"{"a": 1, "b": 2, "ratio": -0.5, "coupling": {"type": "gear", "ra": 10, "rb": "r2 * 2",
+            "internal": true}}"#;
+        let l: MotionLink = serde_json::from_str(text).unwrap();
+        let Some(Coupling::Gear { ra, rb, internal, reverse }) = &l.coupling else { panic!("{l:?}") };
+        assert_eq!((ra, rb, *internal, *reverse), (&Size::Length(10.0), &Size::Expr("r2 * 2".into()), true, false));
+        let back = serde_json::to_value(&l).unwrap();
+        assert_eq!(back["coupling"], serde_json::json!({"type": "gear", "ra": 10.0, "rb": "r2 * 2", "internal": true}));
+        let picked: Size = serde_json::from_str(r#"{"occurrence": 3, "snap": {"type": "circle_center", "pick": [1, 0, 0]}}"#).unwrap();
+        assert!(matches!(picked, Size::Circle(JointOrigin { occurrence: 3, snap: Snap::CircleCenter { .. } })));
+        let screw: Coupling = serde_json::from_str(r#"{"type": "screw", "pitch": 1.5, "reverse": true}"#).unwrap();
+        assert_eq!(screw, Coupling::Screw { pitch: Size::Length(1.5), reverse: true });
+    }
+
+    /// Ratios from the sizes: gears turn by their radii (the other way unless internal), a rack
+    /// and a screw travel per radian whichever of the two joints drives.
+    #[test]
+    fn coupling_ratios_follow_their_sizes() {
+        let mut doc = Document { assembly: chain(3, 0.0), ..Document::default() };
+        if let Some(j) = doc.assembly.joints.get_mut(2) {
+            j.kind = JointKind::Slider;
+        }
+        let st = ModelState::default();
+        let ratio = |a: u64, b: u64, c: Coupling| {
+            let l = MotionLink { a, ia: 0, b, ib: 0, ratio: 0.0, offset: 0.0, coupling: Some(c) };
+            coupling_ratio(&doc, &st, &l).map(|r| r.map_err(|e| e.to_string()))
+        };
+        let len = Size::Length;
+        assert_eq!(ratio(1, 2, Coupling::Gear { ra: len(10.0), rb: len(40.0), internal: false, reverse: false }), Some(Ok(-0.25)));
+        assert_eq!(ratio(1, 2, Coupling::Gear { ra: len(10.0), rb: len(40.0), internal: true, reverse: false }), Some(Ok(0.25)));
+        assert_eq!(ratio(1, 3, Coupling::RackPinion { radius: len(8.0), reverse: false }), Some(Ok(8.0)));
+        assert_eq!(ratio(3, 1, Coupling::RackPinion { radius: len(8.0), reverse: true }), Some(Ok(-0.125)));
+        let screw = ratio(1, 3, Coupling::Screw { pitch: len(std::f64::consts::TAU), reverse: false });
+        assert_eq!(screw, Some(Ok(1.0)));
+        assert!(matches!(ratio(1, 2, Coupling::RackPinion { radius: len(8.0), reverse: false }), Some(Err(_))));
+        assert!(matches!(ratio(1, 3, Coupling::Gear { ra: len(1.0), rb: len(1.0), internal: false, reverse: false }), Some(Err(_))));
+        for bad in [0.0, -2.0, f64::NAN, f64::INFINITY, 1e300] {
+            assert!(matches!(ratio(1, 2, Coupling::Gear { ra: len(bad), rb: len(1.0), internal: false, reverse: false }), Some(Err(_))), "{bad}");
+        }
+        assert!(matches!(ratio(1, 2, Coupling::Gear { ra: Size::Expr("nope".into()), rb: len(1.0), internal: false, reverse: false }), Some(Err(_))));
+    }
+
     #[test]
     fn motions_compose() {
         assert!(close(&motion(JointKind::Revolute, &[std::f64::consts::FRAC_PI_2]), &rot_z(std::f64::consts::FRAC_PI_2)));

crates/doc/src/joints_reach.rs

@@ -0,0 +1,445 @@
+//! Inverse kinematics (`joint.reach`): move the values of the joints on an occurrence's chain so a
+//! point of it reaches a target (and an axis of it points a given way), every value within its
+//! limits, motion links followed, and the closed loops those values are in kept closed.
+
+use std::cell::Cell;
+use std::collections::BTreeSet;
+
+use solidcraft_geom::Vec3;
+use solidcraft_sketch::linalg;
+
+use super::{
+    Assembly, Held, MAX_LOOP_VALUES, MAX_LOOP_WORK, MAX_LOOPS, Solution, Tree, Values, apply_links, build, closure_gaps, jacobian, joint_values,
+    largest, least_squares, limit_bounds, link_chains, loop_groups, loop_scale, unknowns,
+};
+use crate::{Document, ModelState, apply_point, apply_vector, mat_mul};
+
+/// How close counts as reached: mm for the point, degrees for the axis.
+pub const REACH_TOL: f64 = 1e-4;
+
+/// What a reach asks.
+#[derive(Clone, Debug)]
+pub struct Reach {
+    /// The occurrence that reaches.
+    pub occurrence: u64,
+    /// Its point that goes to `to`, in its own (component) coordinates.
+    pub point: Vec3,
+    /// Where the point goes (world).
+    pub to: Vec3,
+    /// A unit axis of it (its own coordinates) and the unit world direction it turns to.
+    pub axis: Option<(Vec3, Vec3)>,
+    /// The joints whose values move toward the target (`None`: every joint on its chain). The
+    /// other joints of a closed loop they are in follow.
+    pub joints: Option<BTreeSet<u64>>,
+}
+
+/// How a reach ended.
+#[derive(Clone, Debug, Default)]
+pub struct Reached {
+    /// The new stored values of the joints that moved (joint id → values).
+    pub values: Values,
+    /// Short of the target: the values it ended on a limit of, with the target pulling past it
+    /// (joint, value index, the upper limit).
+    pub limits: Vec<(u64, usize, bool)>,
+    /// Short of the target: the closing joint of a loop that stopped it (the chain alone, the
+    /// loop left open, gets closer).
+    pub stopped_by_loop: Option<u64>,
+}
+
+/// How much a loop's gap (mm) outweighs a miss of the target (mm) in a step: enough to keep the
+/// step along the mechanism, so putting it back on the loops moves it little.
+const LOOP_WEIGHT: f64 = 1e3;
+/// Steps a reach takes at most, each moving no value more than 10° or a tenth of the chain's
+/// size (so it follows the mechanism's branch).
+const MAX_REACH_STEPS: usize = 200;
+const STEP_ANGLE: f64 = 10.0;
+const STEP_SHARE: f64 = 0.1;
+
+/// Move the values of the joints on `r.occurrence`'s chain (those in `r.joints`, when given) so
+/// its point gets to `r.to`, or as close as the limits and closed loops let it: the nearest pose,
+/// found from where it is (it stays on the mechanism's branch). Values a motion link sets move
+/// through the start of their link chain; the other values of the loops they are in follow. An
+/// error says why nothing can move.
+pub fn reach(doc: &Document, st: &ModelState, r: &Reach) -> Result<Reached, String> {
+    let asm = &doc.assembly;
+    let vals = joint_values(asm);
+    let built = build(doc, st, &vals, &mut Solution::default());
+    let tree = &built.tree;
+    if tree.fixed.contains_key(&r.occurrence) {
+        return Err("it is fixed in place (grounded, or the part its joints are placed from)".into());
+    }
+    if !tree.parent.contains_key(&r.occurrence) {
+        return Err("no joint places it: it is not connected to anything grounded (ground a part, or join it to a grounded part)".into());
+    }
+    let linked: BTreeSet<(u64, usize)> = asm.links.iter().map(|l| (l.b, l.ib)).collect();
+    let allowed = |id: &u64| r.joints.as_ref().is_none_or(|js| js.contains(id));
+    let path: BTreeSet<u64> = tree.path(r.occurrence).1.iter().map(|(k, _)| *k).collect();
+    // The values that move it: those of the joints on its chain (the ones given), a linked one
+    // through the start of its link chain (given or not), and the starts given of the chain's
+    // other linked values.
+    let chosen: BTreeSet<u64> = path.iter().copied().filter(allowed).collect();
+    let mut drive: Vec<(u64, usize)> = Vec::new();
+    for j in chosen.iter().filter_map(|id| tree.joints.get(id)) {
+        drive.extend((0..j.kind.dofs().len()).map(|i| (j.id, i)).filter(|v| !linked.contains(v)));
+    }
+    let starts = link_chains(asm, tree, &path, &linked).1.into_iter().filter(|v| allowed(&v.0));
+    for v in link_chains(asm, tree, &chosen, &linked).1.into_iter().chain(starts) {
+        if !drive.contains(&v) {
+            drive.push(v);
+        }
+    }
+    if drive.is_empty() {
+        return Err(if r.joints.is_some() {
+            "none of the joints given moves it"
+        } else {
+            "no joint on its chain moves (rigid, or set by motion links)"
+        }
+        .into());
+    }
+    // The loops those values are in, and the values of theirs that follow.
+    if built.closing.len() > MAX_LOOPS {
+        return Err(format!("the design has more than {MAX_LOOPS} closed loops"));
+    }
+    let groups = loop_groups(tree, &built.closing, asm, &linked);
+    let (mut vars, mut closers, mut around) = (drive.clone(), Vec::new(), path.clone());
+    let mut taken = BTreeSet::new();
+    while vars.len() <= MAX_LOOP_VALUES {
+        let more: Vec<usize> =
+            groups.iter().enumerate().filter(|(g, (_, _, t))| !taken.contains(g) && t.iter().any(|v| vars.contains(v))).map(|(g, _)| g).collect();
+        if more.is_empty() {
+            break;
+        }
+        for (c, a, _) in more.iter().filter_map(|g| groups.get(*g)) {
+            closers.extend(c.iter().copied());
+            around.extend(a.iter().copied());
+            for v in unknowns(tree, a, asm, &linked, &Held::new()) {
+                if !vars.contains(&v) {
+                    vars.push(v);
+                }
+            }
+        }
+        taken.extend(more);
+    }
+    if vars.len() > MAX_LOOP_VALUES {
+        return Err(format!("its chain and loops have more than {MAX_LOOP_VALUES} values"));
+    }
+    let scale = loop_scale(tree, &around, &vals);
+    let bounds = limit_bounds(tree, &vars);
+    let x0: Vec<f64> = vars.iter().map(|(id, i)| vals.get(id).and_then(|q| q.get(*i)).copied().unwrap_or(0.0)).collect();
+    // A distance steps by a share of the chain's size, of the way to the target or of the point's
+    // reach from its joints, whichever is longest (one slider on its own has no size, and a part
+    // turning about a joint far from its point moves that far).
+    let point = tree.world(r.occurrence, &vals).map(|t| apply_point(&t, r.point));
+    let lever = path
+        .iter()
+        .filter_map(|id| {
+            let (j, (fa, _)) = (tree.joints.get(id)?, tree.frames.get(id)?);
+            Some(apply_point(&mat_mul(&tree.world(j.a.occurrence, &vals)?, fa), Vec3::ZERO).dist(point?))
+        })
+        .fold(0.0, f64::max);
+    let span = point.map_or(scale, |p| scale.max(p.dist(r.to)).max(lever));
+    let cap: Vec<f64> = vars
+        .iter()
+        .map(|(id, i)| if tree.joints.get(id).is_some_and(|j| j.kind.is_angle(*i)) { STEP_ANGLE.to_radians() } else { STEP_SHARE * span })
+        .collect();
+    // Every value around the chain and its loops, links included, moves at most a step at a time:
+    // a value a link sets can turn far more than the one that drives it, and a loop must stay
+    // closed on the way, as joint.drive steps its loops.
+    let mut paced: Vec<((u64, usize), f64)> = Vec::new();
+    for j in around.iter().filter_map(|id| tree.joints.get(id)) {
+        for i in 0..j.kind.dofs().len() {
+            paced.push(((j.id, i), if j.kind.is_angle(i) { STEP_ANGLE.to_radians() } else { STEP_SHARE * span }));
+        }
+    }
+    let tol = (1e-10 * scale).min(1e-7);
+    let mt = if r.axis.is_some() { 6 } else { 3 };
+    let spent = Cell::new(0usize);
+    let mut work = vals.clone();
+    let mut f = |x: &[f64]| misses(tree, asm, r, scale, &vars, &closers, x, &mut work, &spent);
+    let mut x = x0.clone();
+    let miss = |res: &[f64]| res.iter().take(mt).map(|v| v * v).sum::<f64>().sqrt();
+    let before = f(&x0).map_or(f64::INFINITY, |r| miss(&r));
+    let res = approach(&mut f, &|a, b| stride(asm, &vals, &vars, &paced, a, b), mt, &mut x, &bounds, &cap, tol)
+        .ok_or("a closed loop on its chain is open and can't close (joint.list shows its conflict)")?;
+    let mut out = Reached::default();
+    let point_miss = res.iter().take(3).map(|v| v * v).sum::<f64>().sqrt();
+    let turn_miss = (res.iter().skip(3).take(mt - 3).map(|v| v * v).sum::<f64>().sqrt() / scale).to_degrees();
+    if point_miss > REACH_TOL || turn_miss > REACH_TOL {
+        // The limits it rests on: the target pulls the value past them (−Jᵀr over the target's
+        // rows, ignoring pulls at right angles to the miss: under a millionth of the value's own
+        // reach times the miss).
+        let n = x.len();
+        if let Some(jac) = jacobian(&mut f, &x, res.len()) {
+            for (k, (((id, i), v), (lo, hi))) in vars.iter().zip(&x).zip(&bounds).enumerate() {
+                let column = |row: usize| jac.get(row * n + k).copied().unwrap_or(0.0);
+                let pull: f64 = -(0..mt).map(|row| column(row) * res.get(row).copied().unwrap_or(0.0)).sum::<f64>();
+                let eps = 1e-6 * (0..mt).map(|row| column(row).powi(2)).sum::<f64>().sqrt() * miss(&res);
+                let at = |b: f64| b.is_finite() && (v - b).abs() <= 1e-9 * b.abs().max(1.0);
+                if at(*hi) && pull > eps {
+                    out.limits.push((*id, *i, true));
+                } else if at(*lo) && pull < -eps {
+                    out.limits.push((*id, *i, false));
+                }
+            }
+        }
+        // A value a motion link sets, held at its own limit (the link clamps it there): the
+        // target's pull on it as if it were free.
+        if f(&x).is_some() {
+            for (id, i) in linked.iter().filter(|(id, _)| around.contains(id)) {
+                let (Some(v), Some((lo, hi))) = (work.get(id).and_then(|q| q.get(*i)).copied(), limit_bounds(tree, &[(*id, *i)]).first().copied())
+                else {
+                    continue;
+                };
+                let at = |b: f64| b.is_finite() && (v - b).abs() <= 1e-9 * b.abs().max(1.0);
+                if !at(lo) && !at(hi) {
+                    continue;
+                }
+                let nudged = |dv: f64| {
+                    let mut w = work.clone();
+                    if let Some(slot) = w.get_mut(id).and_then(|q| q.get_mut(*i)) {
+                        *slot = v + dv;
+                    }
+                    target(tree, r, scale, &w)
+                };
+                let (Some(up), Some(down)) = (nudged(1e-6), nudged(-1e-6)) else { continue };
+                let pull: f64 = -up.iter().zip(&down).zip(&res).map(|((a, b), r)| (a - b) / 2e-6 * r).sum::<f64>();
+                let eps = 1e-6 * up.iter().zip(&down).map(|(a, b)| ((a - b) / 2e-6).powi(2)).sum::<f64>().sqrt() * miss(&res);
+                if at(hi) && pull > eps {
+                    out.limits.push((*id, *i, true));
+                } else if at(lo) && pull < -eps {
+                    out.limits.push((*id, *i, false));
+                }
+            }
+        }
+        // A loop stopped it when the chain alone gets closer.
+        // ponytail: names the first loop of several; trying each one open would name the one that binds.
+        if let Some(first) = closers.first() {
+            let k = drive.len();
+            let mut alone = vals.clone();
+            let mut g = |x: &[f64]| misses(tree, asm, r, scale, &drive, &[], x, &mut alone, &spent);
+            let (mut xo, bo, co) = (x0.get(..k).unwrap_or_default().to_vec(), bounds.get(..k).unwrap_or_default(), cap.get(..k).unwrap_or_default());
+            // The loops left open, nothing to pace.
+            if let Some(ro) = approach(&mut g, &|_, _| 0.0, mt, &mut xo, bo, co, tol)
+                && miss(&ro) < miss(&res) - REACH_TOL.max(1e-9 * miss(&res))
+            {
+                out.stopped_by_loop = Some(*first);
+            }
+        }
+    }
+    // The stored values that changed, when that got it closer (by more than the solver's noise:
+    // a held part doesn't creep).
+    let gained = before - miss(&res) > 1e-7;
+    for ((id, i), v) in vars.iter().zip(&x).filter(|_| gained) {
+        let Some(j) = tree.joints.get(id) else { continue };
+        if j.values.get(*i) == Some(v) {
+            continue;
+        }
+        let q = out.values.entry(*id).or_insert_with(|| {
+            let mut q = j.values.clone();
+            q.resize(j.kind.dofs().len(), 0.0);
+            q
+        });
+        if let Some(slot) = q.get_mut(*i) {
+            *slot = *v;
+        }
+    }
+    Ok(out)
+}
+
+/// The target's misses with the values `vars` at `x`: the point's (mm), then the axis's (as mm
+/// across the chain's `scale`), then the gaps of the loops `closers`, weighted.
+fn misses(
+    tree: &Tree,
+    asm: &Assembly,
+    r: &Reach,
+    scale: f64,
+    vars: &[(u64, usize)],
+    closers: &[u64],
+    x: &[f64],
+    work: &mut Values,
+    spent: &Cell<usize>,
+) -> Option<Vec<f64>> {
+    spent.set(spent.get() + 1);
+    if spent.get() > MAX_LOOP_WORK {
+        return None;
+    }
+    for ((id, i), v) in vars.iter().zip(x) {
+        if let Some(slot) = work.get_mut(id).and_then(|q| q.get_mut(*i)) {
+            *slot = *v;
+        }
+    }
+    apply_links(asm, work);
+    let mut out = target(tree, r, scale, work)?;
+    let n = out.len();
+    closure_gaps(tree, closers, work, scale, &mut out)?;
+    for v in out.iter_mut().skip(n) {
+        *v *= LOOP_WEIGHT;
+    }
+    out.iter().all(|v| v.is_finite()).then_some(out)
+}
+
+/// The target's misses for these values: the point's (mm), then the axis's (as mm across `scale`).
+fn target(tree: &Tree, r: &Reach, scale: f64, vals: &Values) -> Option<Vec<f64>> {
+    let t = tree.world(r.occurrence, vals)?;
+    let d = apply_point(&t, r.point) - r.to;
+    let mut out = vec![d.x, d.y, d.z];
+    if let Some((a, z)) = r.axis {
+        let w = (apply_vector(&t, a) - z) * scale;
+        out.extend([w.x, w.y, w.z]);
+    }
+    Some(out)
+}
+
+/// How many steps apart the values `vars` at `a` and at `b` put the `paced` values (each with its
+/// step), motion links followed.
+fn stride(asm: &Assembly, vals: &Values, vars: &[(u64, usize)], paced: &[((u64, usize), f64)], a: &[f64], b: &[f64]) -> f64 {
+    let at = |x: &[f64]| {
+        let mut w = vals.clone();
+        for ((id, i), v) in vars.iter().zip(x) {
+            if let Some(slot) = w.get_mut(id).and_then(|q| q.get_mut(*i)) {
+                *slot = *v;
+            }
+        }
+        apply_links(asm, &mut w);
+        w
+    };
+    let (wa, wb) = (at(a), at(b));
+    let get = |w: &Values, id: &u64, i: usize| w.get(id).and_then(|q| q.get(i)).copied().unwrap_or(0.0);
+    paced.iter().map(|((id, i), step)| (get(&wb, id, *i) - get(&wa, id, *i)).abs() / step).fold(0.0, f64::max)
+}
+
+/// Levenberg-Marquardt that stays on the loops: move `x` (within `bounds`, at most `cap` per value
+/// and a step of every value `stride` measures, links included, a step) to bring the first `mt` values of `f` (the target's misses) toward zero, the rest (the
+/// loops' weighted gaps) at zero. Each step is solved over all the rows, values on a limit the
+/// step pushes past held, then put back on the loops (`least_squares` on their gaps) and taken
+/// when it gets closer. It ends at the target, or as close as the limits and loops let it get.
+/// Returns `f` there, or `None` when the loops don't close at the start.
+fn approach(
+    f: &mut dyn FnMut(&[f64]) -> Option<Vec<f64>>,
+    stride: &dyn Fn(&[f64], &[f64]) -> f64,
+    mt: usize,
+    x: &mut Vec<f64>,
+    bounds: &[(f64, f64)],
+    cap: &[f64],
+    tol: f64,
+) -> Option<Vec<f64>> {
+    let n = x.len();
+    let miss = |r: &[f64]| r.iter().take(mt).map(|v| v * v).sum::<f64>();
+    let close = |f: &mut dyn FnMut(&[f64]) -> Option<Vec<f64>>, x: &mut Vec<f64>| {
+        least_squares(&mut |y| f(y).map(|r| r.get(mt..).unwrap_or_default().to_vec()), x, bounds, tol * LOOP_WEIGHT)
+    };
+    let loops = f(x)?.len() > mt;
+    if loops && !close(f, x) {
+        return None;
+    }
+    let mut r = f(x)?;
+    let (mut lambda, mut kicked) = (1e-3, false);
+    for _ in 0..MAX_REACH_STEPS {
+        if largest(r.get(..mt).unwrap_or_default()) <= tol {
+            break;
+        }
+        let m = r.len();
+        let Some(jac) = jacobian(f, x, m) else { break };
+        // The normal equations JᵀJ δ = −Jᵀr, and the target rows' share of the diagonal (the
+        // damping scales with it, so the loops' weight doesn't slow the step along them).
+        let (mut jtj, mut g, mut diag) = (linalg::Mat::zeros(n, n), vec![0.0; n], vec![0.0; n]);
+        for (row, ri) in r.iter().enumerate() {
+            let a = jac.get(row * n..(row + 1) * n).unwrap_or_default();
+            for (p, ap) in a.iter().enumerate().filter(|(_, v)| **v != 0.0) {
+                if let Some(gp) = g.get_mut(p) {
+                    *gp -= ap * ri;
+                }
+                if row < mt
+                    && let Some(dp) = diag.get_mut(p)
+                {
+                    *dp += ap * ap;
+                }
+                for (q, aq) in a.iter().enumerate().skip(p) {
+                    jtj.add(p, q, ap * aq);
+                }
+            }
+        }
+        for p in 0..n {
+            for q in 0..p {
+                jtj.set(p, q, jtj.get(q, p));
+            }
+        }
+        let mut stepped = false;
+        while lambda < 1e12 && !stepped {
+            let mut held = vec![false; n];
+            // Solved, then again with the values held that it pushes past their limits.
+            for _ in 0..=n {
+                let mut a = jtj.clone();
+                let mut b = g.clone();
+                for p in 0..n {
+                    a.add(p, p, lambda * (1.0 + diag.get(p).copied().unwrap_or(0.0)));
+                    if held.get(p).copied().unwrap_or(false) {
+                        for q in 0..n {
+                            a.set(p, q, if p == q { 1.0 } else { 0.0 });
+                            a.set(q, p, if p == q { 1.0 } else { 0.0 });
+                        }
+                        if let Some(bp) = b.get_mut(p) {
+                            *bp = 0.0;
+                        }
+                    }
+                }
+                let Some(d) = linalg::solve(a, b) else { break };
+                let past: Vec<bool> =
+                    x.iter().zip(&d).zip(bounds).map(|((v, dv), (lo, hi))| (*dv > 0.0 && *v >= *hi) || (*dv < 0.0 && *v <= *lo)).collect();
+                if past.iter().zip(&held).any(|(p, h)| *p && !*h) {
+                    held = held.iter().zip(&past).map(|(h, p)| *h || *p).collect();
+                    continue;
+                }
+                let full: Vec<f64> = x.iter().zip(&d).map(|(v, dv)| v + dv).collect();
+                let over = d.iter().zip(cap).map(|(d, c)| d.abs() / c).fold(1.0f64, f64::max).max(stride(x, &full));
+                let mut next: Vec<f64> = x.iter().zip(&d).zip(bounds).map(|((v, dv), (lo, hi))| (v + dv / over).max(*lo).min(*hi)).collect();
+                // Checked again once taken: a link held at a limit or the loops closed again may
+                // move it further than foreseen (joint.drive halves such steps too).
+                if (!loops || close(f, &mut next))
+                    && stride(x, &next) <= 2.0
+                    && let Some(rn) = f(&next)
+                    && miss(&rn) < miss(&r)
+                {
+                    (*x, r) = (next, rn);
+                    // A step cut down to the cap (as at a stretched, singular pose) damps the next one
+                    // more instead of less, so it doesn't crawl along its longest value.
+                    lambda = if over > 1.0 { (lambda * over).min(1e6) } else { (lambda / 3.0).max(1e-9) };
+                    stepped = true;
+                }
+                break;
+            }
+            if !stepped {
+                lambda *= 4.0;
+            }
+        }
+        if !stepped {
+            // Where nothing changes the misses to first order but they aren't least (the target
+            // straight across a pivot from the point), a small kick off it gets closer, once.
+            if kicked {
+                break;
+            }
+            kicked = true;
+            // Both ways: one may run into a limit.
+            for sign in [1.0, -1.0] {
+                let mut next: Vec<f64> = x
+                    .iter()
+                    .zip(cap.iter().zip(bounds))
+                    .enumerate()
+                    .map(|(k, (v, (c, (lo, hi))))| (v + sign * 1e-3 * c * if k % 2 == 0 { 1.0 } else { -1.0 }).max(*lo).min(*hi))
+                    .collect();
+                if (!loops || close(f, &mut next))
+                    && stride(x, &next) <= 2.0
+                    && let Some(rn) = f(&next)
+                    && miss(&rn) < miss(&r)
+                {
+                    (*x, r, lambda, stepped) = (next, rn, 1e-3, true);
+                    break;
+                }
+            }
+            if !stepped {
+                break;
+            }
+        }
+    }
+    Some(r)
+}

crates/doc/src/lib.rs

@@ -34,10 +34,12 @@ pub mod metadata;
 pub use metadata::Metadata;
 pub mod motion;
 mod name_lookup;
+mod names;
 pub mod naming;
 mod params;
 pub mod physical_material;
 mod piece_names;
+mod points;
 mod profile_refs;
 pub mod progress;
 mod walk;
@@ -56,11 +58,14 @@ pub use assembly::{
 pub use document::*;
 pub use eval::{
     EdgeRef, FeatureResult, Model, ModelBody, ModelState, PlacedBodies, RevolveExtent, SolvedSketch, ThreadInfo, curve_pick_error, edge_names_for,
-    edge_refs, face_point_names, face_point_state, hole_direction_at, object_height, parse_metric_thread, pattern_matrices, revolve_extent,
-    revolve_extent_with_convention, select_profiles, sketch_hole_direction, state_in_frame, state_in_frame_at, through_all_distance, world_state,
-    world_state_reusing,
+    edge_refs, face_point_names, face_point_state, hole_direction_at, import_body_names, object_height, parse_metric_thread, pattern_matrices,
+    revolve_extent, revolve_extent_with_convention, select_profiles, sketch_hole_direction, sketch_line_plane, state_in_frame, state_in_frame_at,
+    through_all_distance, world_state, world_state_reusing,
 };
+pub use expr::Expr;
+pub use names::{BodyName, FeatureName, SketchId};
 pub use params::{ParamRow, ParamUser, cycles};
+pub use points::{Dir, FacePick, Position, plain};
 pub use solidcraft_kernel as kernel;
 pub use solidcraft_sketch as sketch;
 

crates/doc/src/names.rs

@@ -0,0 +1,146 @@
+//! What a feature refers to: bodies and features by name, sketches by id. Each is saved as the
+//! plain name or id it wraps, but has its own type, so a body name can't be passed where a
+//! feature name or an expression is meant.
+
+use std::ops::Deref;
+
+use serde::{Deserialize, Serialize};
+
+macro_rules! name_type {
+    ($(#[$doc:meta])* $name:ident) => {
+        $(#[$doc])*
+        #[derive(Clone, Debug, Default, PartialEq, Eq, Hash, PartialOrd, Ord, Serialize, Deserialize)]
+        #[serde(transparent)]
+        pub struct $name(pub String);
+
+        impl Deref for $name {
+            type Target = str;
+            fn deref(&self) -> &str {
+                &self.0
+            }
+        }
+
+        impl AsRef<str> for $name {
+            fn as_ref(&self) -> &str {
+                &self.0
+            }
+        }
+
+        impl std::borrow::Borrow<str> for $name {
+            fn borrow(&self) -> &str {
+                &self.0
+            }
+        }
+
+        impl From<String> for $name {
+            fn from(s: String) -> Self {
+                $name(s)
+            }
+        }
+
+        impl From<&str> for $name {
+            fn from(s: &str) -> Self {
+                $name(s.to_string())
+            }
+        }
+
+        impl From<&String> for $name {
+            fn from(s: &String) -> Self {
+                $name(s.clone())
+            }
+        }
+
+        impl From<$name> for String {
+            fn from(n: $name) -> String {
+                n.0
+            }
+        }
+
+        impl std::fmt::Display for $name {
+            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                f.write_str(&self.0)
+            }
+        }
+
+        impl PartialEq<str> for $name {
+            fn eq(&self, other: &str) -> bool {
+                self.0 == other
+            }
+        }
+
+        impl PartialEq<&str> for $name {
+            fn eq(&self, other: &&str) -> bool {
+                self.0 == *other
+            }
+        }
+
+        impl PartialEq<String> for $name {
+            fn eq(&self, other: &String) -> bool {
+                &self.0 == other
+            }
+        }
+
+        impl PartialEq<$name> for String {
+            fn eq(&self, other: &$name) -> bool {
+                *self == other.0
+            }
+        }
+
+        impl PartialEq<$name> for str {
+            fn eq(&self, other: &$name) -> bool {
+                self == other.0
+            }
+        }
+    };
+}
+
+name_type!(
+    /// A body, by name.
+    BodyName
+);
+name_type!(
+    /// A feature, by name.
+    FeatureName
+);
+
+/// A sketch, by its feature id.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash, PartialOrd, Ord, Serialize, Deserialize)]
+#[serde(transparent)]
+pub struct SketchId(pub u64);
+
+impl Deref for SketchId {
+    type Target = u64;
+    fn deref(&self) -> &u64 {
+        &self.0
+    }
+}
+
+impl From<u64> for SketchId {
+    fn from(id: u64) -> Self {
+        SketchId(id)
+    }
+}
+
+impl From<SketchId> for u64 {
+    fn from(id: SketchId) -> u64 {
+        id.0
+    }
+}
+
+impl PartialEq<u64> for SketchId {
+    fn eq(&self, other: &u64) -> bool {
+        self.0 == *other
+    }
+}
+
+impl PartialEq<SketchId> for u64 {
+    fn eq(&self, other: &SketchId) -> bool {
+        *self == other.0
+    }
+}
+
+impl std::fmt::Display for SketchId {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.0.fmt(f)
+    }
+}

crates/doc/src/naming.rs

@@ -540,7 +540,7 @@ fn role_name(f: &Feature, before: &ModelState, ps: &[Vec3], ns: &[Vec3], fi: usi
     let c = ps.iter().fold(Vec3::ZERO, |a, p| a + *p) * (1.0 / ps.len().max(1) as f64);
     match &f.kind {
         FeatureKind::Extrude { sketch, .. } => {
-            let Some(ss) = before.sketch(*sketch) else { return format!("F{fid}:face:{fi}") };
+            let Some(ss) = before.sketch(sketch.0) else { return format!("F{fid}:face:{fi}") };
             let n = ss.plane.normal();
             // A face across the extrusion is a cap; others sweep a sketch curve.
             let flat = !ns.is_empty() && ns.iter().all(|m| m.cross(n).len() < 1e-6);
@@ -552,7 +552,7 @@ fn role_name(f: &Feature, before: &ModelState, ps: &[Vec3], ns: &[Vec3], fi: usi
             nearest_curve(ss, Vec2::new(q.x, q.y)).map(|id| format!("F{fid}:side:{id}")).unwrap_or_else(|| format!("F{fid}:face:{fi}"))
         }
         FeatureKind::Revolve { sketch, axis, .. } => {
-            let Some(ss) = before.sketch(*sketch) else { return format!("F{fid}:face:{fi}") };
+            let Some(ss) = before.sketch(sketch.0) else { return format!("F{fid}:face:{fi}") };
             let Ok((o2, d2)) = crate::eval::revolve_axis(ss, axis) else { return format!("F{fid}:face:{fi}") };
             let (o, d) = (ss.plane.to_world(o2), (ss.plane.to_world(o2 + d2) - ss.plane.to_world(o2)).normalized().unwrap_or(Vec3::Z));
             // A flat face holding the axis is an angle cap: on the sketch plane, or the far one.
@@ -582,7 +582,7 @@ fn role_name(f: &Feature, before: &ModelState, ps: &[Vec3], ns: &[Vec3], fi: usi
                 FeatureKind::Loft { sections, .. } => sections.first().map(|x| x.sketch),
                 _ => None,
             };
-            let Some(ss) = sk.and_then(|k| before.sketch(k)) else { return format!("F{fid}:face:{fi}") };
+            let Some(ss) = sk.and_then(|k| before.sketch(k.0)) else { return format!("F{fid}:face:{fi}") };
             let n = ss.plane.normal();
             let h = |p: &Vec3| (*p - ss.plane.origin).dot(n);
             let flat = !ns.is_empty() && ns.windows(2).all(|w| w[0].cross(w[1]).len() < 1e-6);
@@ -613,10 +613,10 @@ fn role_name(f: &Feature, before: &ModelState, ps: &[Vec3], ns: &[Vec3], fi: usi
             format!("F{fid}:{role}")
         }
         FeatureKind::Cylinder { axis, .. } => {
-            let flat = !ns.is_empty() && ns.iter().all(|m| m.cross(*axis).len() < 1e-6);
+            let flat = !ns.is_empty() && ns.iter().all(|m| m.cross(axis.0).len() < 1e-6);
             let role = if !flat {
                 "side"
-            } else if ns.first().is_some_and(|m| m.dot(*axis) > 0.0) {
+            } else if ns.first().is_some_and(|m| m.dot(axis.0) > 0.0) {
                 "top"
             } else {
                 "bottom"

crates/doc/src/params.rs

@@ -8,7 +8,7 @@ use std::collections::{BTreeMap, BTreeSet};
 
 use serde::{Deserialize, Serialize};
 
-use crate::expr::{self, Kind, ParamDef, Value};
+use crate::expr::{self, Expr, Kind, ParamDef, Value};
 use crate::walk::Walk;
 use crate::{DocError, Document, FeatureKind, MAX_PARAMS, Result};
 
@@ -23,7 +23,7 @@ pub(crate) enum ExprRole {
 
 impl FeatureKind {
     /// The feature's numeric inputs: (label, expression, kind), in a fixed order.
-    pub fn inputs_mut(&mut self) -> Vec<(&'static str, &mut String, Kind)> {
+    pub fn inputs_mut(&mut self) -> Vec<(&'static str, &mut Expr, Kind)> {
         let mut v = Vec::new();
         self.walk_exprs_mut(&mut |(label, e, kind, role)| {
             if role == ExprRole::Input {
@@ -38,7 +38,31 @@ impl FeatureKind {
         let mut v = Vec::new();
         self.walk_exprs(&mut |(label, e, kind, role)| {
             if role == ExprRole::Input {
-                v.push((label, e.clone(), kind));
+                v.push((label, e.to_string(), kind));
+            }
+        });
+        v
+    }
+
+    /// The coordinates of the points that place the feature: a primitive's position, an
+    /// explicit plane's origin. They are not inputs (no parameter names), but follow
+    /// parameters as inputs do.
+    pub fn placement_exprs_mut(&mut self) -> Vec<&mut Expr> {
+        let mut v = Vec::new();
+        self.walk_exprs_mut(&mut |(_, e, _, role)| {
+            if role == ExprRole::Placement {
+                v.push(e);
+            }
+        });
+        v
+    }
+
+    /// Read-only view of [`FeatureKind::placement_exprs_mut`].
+    pub fn placement_exprs(&self) -> Vec<&str> {
+        let mut v = Vec::new();
+        self.walk_exprs(&mut |(_, e, _, role)| {
+            if role == ExprRole::Placement {
+                v.push(e.as_str());
             }
         });
         v
@@ -236,7 +260,7 @@ impl Document {
         if let Some(f) = next.features.get_mut(i)
             && let Some((_, e, _)) = f.kind.inputs_mut().into_iter().nth(k)
         {
-            *e = expr_s.clone();
+            *e = expr_s.clone().into();
         }
         if let Some(c) = comment {
             next.param_comments.insert(name.to_string(), c.to_string());
@@ -284,7 +308,7 @@ impl Document {
             if *target != normalized {
                 changed.insert(name.clone());
             }
-            *target = normalized;
+            *target = normalized.into();
         }
         let (_, errors) = next.param_values();
         for (name, error) in errors {
@@ -352,6 +376,25 @@ impl Document {
         rows
     }
 
+    /// Move user parameter `name` to just before (or with `after`, just after) user parameter
+    /// `target`: the order the Parameters dialog lists them in. Nothing else changes.
+    pub fn move_user_param(&mut self, name: &str, target: &str, after: bool) -> Result<()> {
+        fn user(params: &[crate::Param], n: &str) -> Option<usize> {
+            params.iter().position(|p| p.name == n && !p.model)
+        }
+        let (Some(from), Some(_)) = (user(&self.params, name), user(&self.params, target)) else {
+            let missing = if user(&self.params, name).is_none() { name } else { target };
+            return Err(DocError::Unknown(format!("user parameter `{missing}`")));
+        };
+        if name == target {
+            return Err(DocError::Invalid("a parameter cannot move next to itself".into()));
+        }
+        let moved = self.params.remove(from);
+        let at = user(&self.params, target).map_or(self.params.len(), |i| if after { i + 1 } else { i });
+        self.params.insert(at, moved);
+        Ok(())
+    }
+
     pub fn set_favorite(&mut self, name: &str, on: bool) -> Result<()> {
         if !self.name_taken(name) {
             return Err(DocError::Unknown(format!("parameter `{name}`")));
@@ -556,7 +599,7 @@ impl Document {
                     }
                 }
             }
-            if f.kind.point_expr().is_some_and(|p| p.iter().any(|e| expr::references(e).iter().any(|r| r == name))) {
+            if f.kind.placement_exprs().iter().any(|e| expr::references(e).iter().any(|r| r == name)) {
                 out.push(ParamUser::Feature { feature: f.id, name: f.name.clone(), input: "Position".into() });
             }
             if let FeatureKind::Sketch { sketch, .. } = &f.kind {
@@ -565,6 +608,11 @@ impl Document {
                         out.push(ParamUser::Dimension { feature: f.id, name: f.name.clone(), constraint: c.id.clone() });
                     }
                 }
+                for (what, e) in sketch.text_exprs() {
+                    if expr::references(e).iter().any(|r| r == name) {
+                        out.push(ParamUser::Feature { feature: f.id, name: f.name.clone(), input: what.to_string() });
+                    }
+                }
             }
         }
         out
@@ -622,17 +670,17 @@ impl Document {
                     *x = new.to_string();
                 }
             }
-            for e in f.kind.point_expr_mut().into_iter().flatten() {
+            for e in f.kind.placement_exprs_mut() {
                 let r = expr::rename_reference(e, old, new);
                 if r != *e {
-                    *e = r;
+                    *e = r.into();
                     n += 1;
                 }
             }
             for (_, e, _) in f.kind.inputs_mut() {
                 let r = expr::rename_reference(e, old, new);
                 if r != *e {
-                    *e = r;
+                    *e = r.into();
                     n += 1;
                 }
             }
@@ -643,6 +691,13 @@ impl Document {
                         n += 1;
                     }
                 }
+                for e in sketch.text_exprs_mut() {
+                    let r = expr::rename_reference(e, old, new);
+                    if r != *e {
+                        *e = r;
+                        n += 1;
+                    }
+                }
             }
         }
         if self.favorites.remove(old) {
@@ -698,6 +753,7 @@ impl Document {
             let mut names: BTreeSet<String> = f.param_names.iter().filter(|n| !n.is_empty()).cloned().collect();
             if let FeatureKind::Sketch { sketch, .. } = &f.kind {
                 names.extend(sketch.constraints.iter().filter_map(|c| c.param.clone()));
+                names.extend(sketch.text_exprs().into_iter().flat_map(|(_, e)| expr::references(e)));
             }
             out.extend(names.into_iter().map(|n| (format!("Feature:{}", f.name), n)));
         }
@@ -725,6 +781,7 @@ impl Document {
             hit |= f.kind.expressions().iter().any(|e| expr::references(e).iter().any(|r| affected.contains(r)));
             if let FeatureKind::Sketch { sketch, .. } = &f.kind {
                 hit |= sketch.constraints.iter().any(|c| c.param.as_ref().is_some_and(|p| affected.contains(p)));
+                hit |= sketch.text_exprs().iter().any(|(_, e)| expr::references(e).iter().any(|r| affected.contains(r)));
             }
             if hit {
                 out.push(f.id);

crates/doc/src/physical_material.rs

@@ -3,7 +3,7 @@
 
 use serde::{Deserialize, Serialize};
 use serde_json::Value;
-use std::collections::BTreeSet;
+use std::collections::{BTreeMap, BTreeSet};
 
 use crate::{DocError, Result};
 
@@ -116,6 +116,10 @@ pub struct Validation {
     pub property_kinds: Vec<String>,
     pub isotropic_moduli: Option<IsotropicModuli>,
     pub unspecified_conditions: Vec<String>,
+    /// Property kind -> absent condition fields under the existing family policy.
+    /// Empty when reading an older report that did not include this detail.
+    #[serde(default)]
+    pub missing_condition_fields: BTreeMap<String, Vec<String>>,
     pub source_review_required: Vec<String>,
     pub analysis_solver_available: bool,
     pub rendering_properties_available: bool,
@@ -256,6 +260,7 @@ impl MaterialCard {
         let mut kinds = BTreeSet::new();
         let mut used_sources = BTreeSet::new();
         let mut unspecified = Vec::new();
+        let mut missing_condition_fields = BTreeMap::new();
         let mut isotropic_moduli = None;
         for property in &self.properties {
             let kind = property.data.kind();
@@ -279,12 +284,20 @@ impl MaterialCard {
             if let Some(state) = &conditions.state {
                 text(state, 1024, "conditions.state")?;
             }
-            if conditions.temperature_k.is_none()
-                || conditions.state.is_none()
-                || (self.family == Family::Wood && conditions.moisture_dry_basis_kg_kg.is_none())
-                || (self.family == Family::Polymer && conditions.strain_rate_per_s.is_none())
-            {
+            let mut missing = Vec::new();
+            for (absent, field) in [
+                (conditions.temperature_k.is_none(), "temperature_k"),
+                (conditions.state.is_none(), "state"),
+                (self.family == Family::Wood && conditions.moisture_dry_basis_kg_kg.is_none(), "moisture_dry_basis_kg_kg"),
+                (self.family == Family::Polymer && conditions.strain_rate_per_s.is_none(), "strain_rate_per_s"),
+            ] {
+                if absent {
+                    missing.push(field.to_string());
+                }
+            }
+            if !missing.is_empty() {
                 unspecified.push(kind.to_string());
+                missing_condition_fields.insert(kind.to_string(), missing);
             }
             if let Some(moduli) = property.data.validate()? {
                 isotropic_moduli = Some(moduli);
@@ -295,6 +308,7 @@ impl MaterialCard {
             property_kinds: kinds.into_iter().collect(),
             isotropic_moduli,
             unspecified_conditions: unspecified,
+            missing_condition_fields,
             source_review_required: used_sources.into_iter().collect(),
             analysis_solver_available: false,
             rendering_properties_available: false,

crates/doc/src/physical_material_tests.rs

@@ -132,6 +132,58 @@ fn conditions_missing_values_and_source_claims_remain_explicit() {
     assert_eq!(serde_json::from_value::<MaterialCard>(serde_json::to_value(&parsed).unwrap()).unwrap(), parsed);
 }
 
+#[test]
+fn missing_condition_fields_follow_family_policy_without_inventing_values() {
+    for (family, extra) in
+        [("wood", Some("moisture_dry_basis_kg_kg")), ("polymer", Some("strain_rate_per_s")), ("glass", None), ("metal", None), ("other", None)]
+    {
+        let mut value = card(json!({"kind":"density","kg_m3":600.}));
+        value["family"] = json!(family);
+        let mut expected = vec!["temperature_k", "state"];
+        expected.extend(extra);
+        let result = validate_card(&value).unwrap();
+        assert_eq!(result.missing_condition_fields, BTreeMap::from([("density".into(), expected.iter().map(|s| (*s).into()).collect())]));
+        assert_eq!(result.unspecified_conditions, vec!["density"]);
+
+        // Explicit zero dry-basis moisture is known; no wet/dry conversion or default is inferred.
+        value["properties"][0]["conditions"] =
+            json!({"temperature_k":293.15,"state":"synthetic","moisture_dry_basis_kg_kg":0.,"strain_rate_per_s":1.});
+        assert!(validate_card(&value).unwrap().missing_condition_fields.is_empty());
+        for field in expected {
+            let mut partial = value.clone();
+            partial["properties"][0]["conditions"].as_object_mut().unwrap().remove(field);
+            let result = validate_card(&partial).unwrap();
+            assert_eq!(result.missing_condition_fields, BTreeMap::from([("density".into(), vec![field.into()])]));
+            assert_eq!(result.unspecified_conditions, vec!["density"]);
+        }
+        value["properties"] = json!([]);
+        let result = validate_card(&value).unwrap();
+        assert!(result.missing_condition_fields.is_empty() && result.unspecified_conditions.is_empty());
+    }
+}
+
+#[test]
+fn missing_condition_fields_are_per_property_and_reports_remain_backward_readable() {
+    let mut value = card(json!({"kind":"density","kg_m3":600.}));
+    value["properties"][0]["conditions"] = json!({"temperature_k":293.15,"state":"synthetic"});
+    value["properties"].as_array_mut().unwrap().push(json!({"data":isotropic(12e9,0.25),"source_id":"test",
+        "conditions":{"state":"synthetic","moisture_dry_basis_kg_kg":1.5}}));
+    let before = value.clone();
+    let result = validate_card(&value).unwrap();
+    let expected = json!({"density":["moisture_dry_basis_kg_kg"],"elasticity":["temperature_k"]});
+    let serialized = serde_json::to_value(&result).unwrap();
+    assert_eq!(serialized["missing_condition_fields"], expected);
+    assert_eq!(result.unspecified_conditions, vec!["density", "elasticity"]);
+    assert_eq!(value, before);
+    assert_eq!(serde_json::from_value::<Validation>(serialized.clone()).unwrap(), result);
+    let mut old = serialized;
+    old.as_object_mut().unwrap().remove("missing_condition_fields");
+    let old: Validation = serde_json::from_value(old).unwrap();
+    assert!(old.missing_condition_fields.is_empty());
+    assert_eq!(old.unspecified_conditions, result.unspecified_conditions);
+    assert_eq!(old.source_review_required, result.source_review_required);
+}
+
 #[test]
 fn thermal_properties_accept_negative_expansion_but_not_negative_conductivity() {
     assert!(validate_card(&card(json!({"kind":"thermal_expansion","per_k":[-1e-6,0.,2e-6],"axes":"material123"}))).is_ok());

crates/doc/src/points.rs

@@ -0,0 +1,61 @@
+//! The points a feature holds, by what they are: a point that picks a face, any other
+//! position, a direction. Each is a `Vec3` (and is saved as one), but a different type, so a
+//! direction can't be moved like a position, and a pick can't be mistaken for either.
+
+use std::ops::{Deref, DerefMut};
+
+use serde::{Deserialize, Serialize};
+use solidcraft_geom::Vec3;
+
+macro_rules! point_type {
+    ($(#[$doc:meta])* $name:ident) => {
+        $(#[$doc])*
+        #[derive(Clone, Copy, Debug, Default, PartialEq, Serialize, Deserialize)]
+        #[serde(transparent)]
+        pub struct $name(pub Vec3);
+
+        impl Deref for $name {
+            type Target = Vec3;
+            fn deref(&self) -> &Vec3 {
+                &self.0
+            }
+        }
+
+        impl DerefMut for $name {
+            fn deref_mut(&mut self) -> &mut Vec3 {
+                &mut self.0
+            }
+        }
+
+        impl From<Vec3> for $name {
+            fn from(v: Vec3) -> Self {
+                $name(v)
+            }
+        }
+
+        impl From<$name> for Vec3 {
+            fn from(p: $name) -> Vec3 {
+                p.0
+            }
+        }
+    };
+}
+
+point_type!(
+    /// A point that picks a face: it moves with the feature, and names the face it picks.
+    FacePick
+);
+point_type!(
+    /// A position (an edge pick, an axis origin, a fold line): it moves with the feature.
+    Position
+);
+point_type!(
+    /// A direction: it turns with the feature, and never moves.
+    Dir
+);
+
+/// The plain values of a list of picks, positions, directions or names (for code that takes
+/// `Vec3`s or `String`s).
+pub fn plain<T, P: Clone + Into<T>>(ps: &[P]) -> Vec<T> {
+    ps.iter().map(|p| p.clone().into()).collect()
+}

crates/doc/src/profile_refs.rs

@@ -309,7 +309,7 @@ mod tests {
             .add_feature(
                 crate::FeatureKind::Extrude {
                     thin: None,
-                    sketch: feature,
+                    sketch: crate::SketchId(feature),
                     profiles: selection.clone(),
                     extent: crate::Extent {
                         convention: crate::ExtrudeConvention::LegacyPerSide,
@@ -436,7 +436,7 @@ mod tests {
             .add_feature(
                 crate::FeatureKind::Extrude {
                     thin: None,
-                    sketch: feature,
+                    sketch: crate::SketchId(feature),
                     profiles: selection.clone(),
                     extent: crate::Extent {
                         convention: crate::ExtrudeConvention::LegacyPerSide,

crates/doc/src/project.rs

@@ -255,14 +255,17 @@ fn resolve_uncached(
         LinkSource::SketchAxis { name } => {
             vec![solidcraft_sketch::sketch_axis_geom(name).ok_or_else(|| DocError::Unknown(format!("sketch axis `{name}`")))?]
         }
-        LinkSource::Text { text, at, height, angle, font, style } if style.path.is_none() => {
+        LinkSource::Text { text, at, height, angle, font, style, .. } if style.path.is_none() => {
             solidcraft_sketch::text_geometry_styled(font.as_deref(), text, *at, *height, *angle, style, None)?
         }
         // Its path is a curve of its own sketch: set with the sketch (`Sketch::text_source_geometry`).
         LinkSource::Text { .. } => return Err(DocError::Invalid("a text on a path is set with its sketch".into())),
         LinkSource::Plane { name } => {
-            let pr =
-                if Plane::named(name).is_some() { PlaneRef::Origin { name: name.clone() } } else { PlaneRef::Construction { name: name.clone() } };
+            let pr = if Plane::named(name).is_some() {
+                PlaneRef::Origin { name: name.clone() }
+            } else {
+                PlaneRef::Construction { name: name.clone().into() }
+            };
             let other = doc.resolve_plane_in(vals, &pr, 0, Some(st)).map_err(|_| lost(&format!("plane {name}")))?;
             plane_trace(plane, &other).into_iter().collect()
         }

crates/doc/src/render_settings.rs

@@ -67,13 +67,18 @@ impl Default for RenderSetup {
 impl RenderSetup {
     pub fn validate(&self) -> Result<()> {
         let limits = RenderLimits::default();
-        if self.width == 0
-            || self.height == 0
-            || u64::from(self.width) > limits.max_dimension
-            || u64::from(self.height) > limits.max_dimension
-            || u64::from(self.width) * u64::from(self.height) > limits.max_pixels
+        let (width, height) = (u64::from(self.width), u64::from(self.height));
+        if width == 0 || height == 0 {
+            return Err(DocError::Invalid("render output must be at least 1 × 1 pixels".into()));
+        }
+        if let Some((w, h)) = limits.fit(width, height, None)
+            && (w, h) != (width, height)
         {
-            return Err(DocError::Invalid("render output exceeds the dimension/pixel limits".into()));
+            return Err(DocError::Invalid(format!(
+                "render output {width} × {height} exceeds the image limits ({} pixels per side, {} pixels in all); \
+                 the largest image at this aspect is {w} × {h}",
+                limits.max_dimension, limits.max_pixels
+            )));
         }
         let camera = &self.camera;
         if !camera.is_valid()
@@ -218,6 +223,18 @@ mod tests {
         }
     }
 
+    #[test]
+    fn oversized_output_names_the_limits_and_the_largest_size() {
+        let setup = RenderSetup { width: 4096, height: 4096, ..Default::default() };
+        let message = setup.validate().unwrap_err().to_string();
+        assert!(message.contains("4096 × 4096 exceeds the image limits (4096 pixels per side, 4194304 pixels in all)"), "{message}");
+        assert!(message.contains("the largest image at this aspect is 2048 × 2048"), "{message}");
+        let setup = RenderSetup { width: 7680, height: 4320, ..Default::default() };
+        let message = setup.validate().unwrap_err().to_string();
+        assert!(message.contains("the largest image at this aspect is 27"), "{message}");
+        assert!(RenderSetup { width: 2048, height: 2048, ..Default::default() }.validate().is_ok());
+    }
+
     #[test]
     fn invalid_saved_intent_is_rejected_at_deserialization() {
         for patch in [

crates/doc/src/sheet.rs

@@ -31,6 +31,8 @@ const MAX_FLAT_POINTS: usize = 16_384;
 const MAX_FLAT_SAMPLES: usize = 65_536;
 const MAX_FLAT_PIECES: usize = 4096;
 const MAX_FLAT_WORK: usize = 500_000_000;
+/// Pieces of flat material sharing less area than this (mm²) only touch.
+const TOUCH_AREA: f64 = 1e-6;
 
 /// Starts the warning a fold gives when its `fixed` point touches no material: a recompute keeps
 /// the side the point lies on, and the `sheet.fold` command refuses such a point (#263).
@@ -359,6 +361,15 @@ impl ReliefShape {
     }
 }
 
+/// The corner relief an edge flange feature asks for in place of the rule's. A value left out
+/// follows the rule.
+#[derive(Clone, Copy, Debug, Default, PartialEq)]
+pub struct ReliefOverride {
+    pub shape: Option<ReliefShape>,
+    /// How far across the relief is (mm).
+    pub size: Option<f64>,
+}
+
 /// A rule's values (mm, unit-less K).
 #[derive(Clone, Copy, Debug, PartialEq, Serialize)]
 pub struct RuleValues {
@@ -490,6 +501,12 @@ pub struct SheetBody {
     /// Perforation fields (#732), flat coordinates; their holes are computed on demand and never cut into the B-rep.
     #[serde(skip_serializing_if = "Vec::is_empty")]
     pub perforations: Vec<SheetPerforation>,
+    /// Regions (flat coordinates) that text cut or machined, letters with their counters as
+    /// holes: a record of where the sheet's text went, so that its DXF can write the letters on
+    /// layers of their own (see [`SheetBody::letters`]). The cut-outs and pockets themselves are
+    /// in `holes` and `pockets`. Derived from feature history, like `pockets`.
+    #[serde(skip_serializing_if = "Vec::is_empty")]
+    pub labels: Vec<Region2>,
     /// Unfolded.
     pub flat: bool,
     /// Gap between flanges that meet at a corner.
@@ -1600,6 +1617,26 @@ impl SheetBody {
         Ok(through.unwrap_or_default())
     }
 
+    /// The text the sheet carries: what [`SheetBody::labels`] records, ready to tell whether a
+    /// loop of the flat pattern is a letter.
+    pub fn letters(&self) -> Letters {
+        let regions = self
+            .labels
+            .iter()
+            .map(|r| {
+                let (mut lo, mut hi) = (Vec2::new(f64::MAX, f64::MAX), Vec2::new(f64::MIN, f64::MIN));
+                for p in r.outer.polyline(1e-3) {
+                    lo = Vec2::new(lo.x.min(p.x), lo.y.min(p.y));
+                    hi = Vec2::new(hi.x.max(p.x), hi.y.max(p.y));
+                }
+                // A polyline of 0.001 mm chords is within 0.001 mm of the curve.
+                let pad = Vec2::new(0.01, 0.01);
+                (lo - pad, hi + pad, std::iter::once(&r.outer).chain(&r.holes).flat_map(|lp| lp.segs.iter().copied()).collect())
+            })
+            .collect();
+        Letters { regions }
+    }
+
     /// Pocket operations clipped to the surviving flat material, with exact depth intervals.
     pub fn machining(&self) -> Result<Vec<SheetPocket>> {
         let material = self.flat_regions()?;
@@ -1670,6 +1707,84 @@ impl SheetBody {
         let regions = if cuts.is_empty() { regions } else { material_boolean(&regions, &cuts, kernel::BoolOp::Cut, &mut work)? };
         Ok(regions)
     }
+
+    /// The pieces of flat material that a cut parted from the base: `after` is this sheet's
+    /// [`Self::flat_material`] after the cut, `before` the sheet before it. A piece is parted when
+    /// it holds none of the base panel, lies in a piece that held some before the cut, and no
+    /// other piece surrounds it: a flange cut off along its bend (with any flange on it), the
+    /// part of a ring's inside that lies on a flange's edge, the tip of a flange beyond a cut
+    /// through a closed corner. A ring's island and a letter's counter, inside other material,
+    /// are not counted; nor are pieces an earlier cut parted, nor anything once no piece holds
+    /// the base.
+    pub(crate) fn parted_from_base(&self, after: &[Region2], before: &SheetBody) -> Result<Vec<Region2>> {
+        if after.len() < 2 {
+            return Ok(Vec::new());
+        }
+        let mut work = FlatWork::new();
+        work.charge(after.len().saturating_mul(after.len()))?;
+        let base = [planar_region(&self.base)?];
+        let holds_base = |piece: &Region2, work: &mut FlatWork| -> Result<bool> {
+            let common = material_boolean(std::slice::from_ref(piece), &base, kernel::BoolOp::Intersect, work)?;
+            Ok(common.iter().map(Region2::area).sum::<f64>() > TOUCH_AREA)
+        };
+        // The cheap test first: a piece inside another's outline is an island, whatever it holds.
+        let outlines: Vec<(Vec<Vec2>, Vec2, Vec2)> = after
+            .iter()
+            .map(|r| {
+                let pts = r.outer.polyline(1e-3);
+                let lo = pts.iter().fold(Vec2::new(f64::MAX, f64::MAX), |a, p| Vec2::new(a.x.min(p.x), a.y.min(p.y)));
+                let hi = pts.iter().fold(Vec2::new(f64::MIN, f64::MIN), |a, p| Vec2::new(a.x.max(p.x), a.y.max(p.y)));
+                (pts, lo, hi)
+            })
+            .collect();
+        let (mut open, mut islands) = (Vec::new(), Vec::new());
+        for (i, piece) in after.iter().enumerate() {
+            let p = piece.interior_point();
+            let inside = |(pts, lo, hi): &(Vec<Vec2>, Vec2, Vec2)| (lo.x..=hi.x).contains(&p.x) && (lo.y..=hi.y).contains(&p.y) && point_in(pts, p);
+            if outlines.iter().enumerate().any(|(j, o)| j != i && inside(o)) {
+                islands.push(piece);
+            } else {
+                open.push(piece);
+            }
+        }
+        let (mut joined, mut loose) = (false, Vec::new());
+        for piece in open {
+            if holds_base(piece, &mut work)? {
+                joined = true;
+            } else {
+                loose.push(piece);
+            }
+        }
+        if loose.is_empty() {
+            return Ok(Vec::new());
+        }
+        // The base may be an island itself (a cut all round it).
+        for piece in islands {
+            if joined {
+                break;
+            }
+            joined = holds_base(piece, &mut work)?;
+        }
+        if !joined {
+            return Ok(Vec::new());
+        }
+        // A cut only takes material away: each piece lies in the piece it was part of.
+        let mut held = Vec::new();
+        for piece in before.flat_material()? {
+            if holds_base(&piece, &mut work)? {
+                held.push(piece);
+            }
+        }
+        Ok(loose
+            .into_iter()
+            .filter(|piece| {
+                let p = piece.interior_point();
+                held.iter().any(|h| h.contains(p))
+            })
+            .cloned()
+            .collect())
+    }
+
     /// Outline loops of the flat pattern (flat coordinates): the pieces' edges, shared ones left out.
     pub fn outline(&self) -> Result<Vec<Vec<Vec2>>> {
         if self.flanges.len().saturating_mul(2).saturating_add(1) > MAX_FLAT_PIECES {
@@ -2045,7 +2160,7 @@ impl SheetBody {
         flip: bool,
     ) -> Result<(Vec<usize>, Vec<String>)> {
         let each: Vec<EdgeFlange> = picks.iter().map(|&pick| EdgeFlange { pick, height, angle }).collect();
-        self.add_flanges_each(&each, radius, position, flip)
+        self.add_flanges_each(&each, radius, position, flip, ReliefOverride::default())
     }
 
     /// Edge flanges that each have their own height and angle, in one go: every edge is trimmed
@@ -2058,8 +2173,16 @@ impl SheetBody {
     /// the base that ends beside more of the base gets the rule's bend relief there
     /// (`relieve_bend_ends`). Where cut-outs have taken part of a picked edge away, the flange
     /// runs along the stretch they leave nearest the pick and takes its setback off that stretch
-    /// only; an edge they took whole is refused.
-    pub fn add_flanges_each(&mut self, edges: &[EdgeFlange], radius: f64, position: &str, flip: bool) -> Result<(Vec<usize>, Vec<String>)> {
+    /// only; an edge they took whole is refused. The corners between these flanges are relieved
+    /// as the rule says, except where `relief` names another shape or size.
+    pub fn add_flanges_each(
+        &mut self,
+        edges: &[EdgeFlange],
+        radius: f64,
+        position: &str,
+        flip: bool,
+        relief: ReliefOverride,
+    ) -> Result<(Vec<usize>, Vec<String>)> {
         if edges.is_empty() || edges.len() > 1000 {
             return Err(DocError::Invalid("pick 1…1000 edges".into()));
         }
@@ -2187,7 +2310,7 @@ impl SheetBody {
         for (&i, &free) in made.iter().zip(&freed) {
             notes.extend(self.relieve_bend_ends(i, free));
         }
-        notes.extend(self.close_corners(&made));
+        notes.extend(self.close_corners(&made, relief));
         notes.extend(self.close_return_corners(&made));
         Ok((made, notes))
     }
@@ -2201,7 +2324,7 @@ impl SheetBody {
     /// such end left as it is.
     fn relieve_bend_ends(&mut self, i: usize, free: (bool, bool)) -> Vec<String> {
         let Some(f) = self.flanges.get(i).cloned() else { return Vec::new() };
-        if f.parent.is_some() || f.shape.is_some() {
+        if f.parent.is_some() {
             return Vec::new();
         }
         let (width, depth) = (self.bend_relief.0, self.bend_relief.1.max(0.0));
@@ -2605,37 +2728,50 @@ impl SheetBody {
         out
     }
 
-    /// Close the corners the new flanges make, then cut the rule's relief at each (or tear it).
-    /// Returns a note for every corner left open, without its relief or not torn.
-    fn close_corners(&mut self, made: &[usize]) -> Vec<String> {
+    /// Close the corners the new flanges make, then cut the relief at each (or tear it): the
+    /// rule's, but for the shape or size `relief` names. Returns a note for every corner left
+    /// open, without its relief or not torn.
+    fn close_corners(&mut self, made: &[usize], relief: ReliefOverride) -> Vec<String> {
         let corners = self.corners(made);
         let mut notes = Vec::new();
-        let at = |s: &SheetBody, c: Vec2| {
-            let w = apply_point(&s.frame_mat(), v3(c));
-            format!("({:.3}, {:.3}, {:.3})", w.x, w.y, w.z)
-        };
         let mut closed = Vec::with_capacity(corners.len());
         for k in &corners {
             match self.close_corner(k) {
                 Ok(()) => closed.push(*k),
-                Err(why) => notes.push(format!("the flanges at {} are left open: {why}", at(self, k.c))),
+                Err(why) => notes.push(format!("the flanges at {} are left open: {why}", self.shown(k.c))),
             }
         }
-        match self.relief {
+        notes.extend(self.relieve_corners(&corners, &closed, relief));
+        notes
+    }
+
+    /// A point of the flat frame, in the part's coordinates, for a note.
+    fn shown(&self, c: Vec2) -> String {
+        let w = apply_point(&self.frame_mat(), v3(c));
+        format!("({:.3}, {:.3}, {:.3})", w.x, w.y, w.z)
+    }
+
+    /// Cut the relief at each of `corners`, or tear those of them that are `closed`: the rule's,
+    /// but for the shape or size `relief` names. Returns a note for every corner without its
+    /// relief or not torn.
+    fn relieve_corners(&mut self, corners: &[Corner], closed: &[Corner], relief: ReliefOverride) -> Vec<String> {
+        let mut notes = Vec::new();
+        let (shape, size) = (relief.shape.unwrap_or(self.relief), relief.size.unwrap_or(self.relief_size));
+        match shape {
             ReliefShape::Notch => {}
             // The reliefs come last: they move the bends' ends, which is how the corners were found.
             ReliefShape::Round | ReliefShape::Rectangular => {
-                for k in &corners {
-                    if let Err(why) = self.relieve_corner(k, &corners) {
-                        notes.push(format!("no corner relief at {}: {why}", at(self, k.c)));
+                for k in corners {
+                    if let Err(why) = self.relieve_corner(k, corners, shape, size) {
+                        notes.push(format!("no corner relief at {}: {why}", self.shown(k.c)));
                     }
                 }
             }
             // A tear cuts to the flanges' closed ends, so a corner left open gets none.
             ReliefShape::Tear => {
-                for k in &closed {
+                for k in closed {
                     if let Err(why) = self.tear_corner(k) {
-                        notes.push(format!("the corner at {} keeps its notch: {why}", at(self, k.c)));
+                        notes.push(format!("the corner at {} keeps its notch: {why}", self.shown(k.c)));
                     }
                 }
             }
@@ -2802,7 +2938,7 @@ impl SheetBody {
         Ok(())
     }
 
-    /// Cut the rule's relief where two bends meet at a corner of the base, `relief_size / 2`
+    /// Cut a relief `size` across where two bends meet at a corner of the base, `size / 2`
     /// from the corner along both edges: a round about the corner through the angle the base
     /// fills there, or the square with that side (a kite where the corner isn't square, its
     /// cuts square to the two edges). The base's edges then start that far from the corner, so
@@ -2812,8 +2948,7 @@ impl SheetBody {
     /// that would leave nothing of an edge it starts on (with the relief at that edge's other
     /// end, where there is one), or one reaching as far from the corner as another edge of the
     /// base is, is refused with the reason.
-    fn relieve_corner(&mut self, k: &Corner, corners: &[Corner]) -> std::result::Result<(), String> {
-        let size = self.relief_size;
+    fn relieve_corner(&mut self, k: &Corner, corners: &[Corner], shape: ReliefShape, size: f64) -> std::result::Result<(), String> {
         if !(size >= MIN_CORNER_RELIEF) {
             return Err(format!("the relief size {size:.4} mm is below {MIN_CORNER_RELIEF} mm"));
         }
@@ -2845,7 +2980,7 @@ impl SheetBody {
         }
         // The relief from the edge that ends at the corner to the one that starts there, and
         // how far from the corner it reaches.
-        let (relief, reach) = match self.relief {
+        let (relief, reach) = match shape {
             ReliefShape::Notch | ReliefShape::Tear => return Ok(()),
             ReliefShape::Round => (vec![Seg2::Arc { center: c, radius: r, start: da.angle(), sweep: -alpha }], r),
             ReliefShape::Rectangular => {
@@ -3953,6 +4088,30 @@ fn polys_cross(a: &[Vec2], b: &[Vec2]) -> bool {
     })
 }
 
+/// Whether every segment of `lp` lies on one of `curves` (its ends and its middle, within
+/// 0.0001 mm): the loop is made of those curves, or of parts of them.
+pub fn loop_lies_on(lp: &Loop2, curves: &[Seg2]) -> bool {
+    const TOL: f64 = 1e-4;
+    let near = |p: Vec2| curves.iter().any(|c| c.point_at(c.closest_param(p)).dist(p) <= TOL);
+    !lp.segs.is_empty() && lp.segs.iter().all(|g| near(g.start()) && near(g.mid()) && near(g.end()))
+}
+
+/// Tells which loops of a sheet's flat pattern are letters (see [`SheetBody::letters`]).
+#[derive(Clone, Debug)]
+pub struct Letters {
+    /// Each text region's corners (lowest, highest) and the segments of its outlines.
+    regions: Vec<(Vec2, Vec2, Vec<Seg2>)>,
+}
+
+impl Letters {
+    /// Whether `lp` is made of the outlines of text the sheet carries: a letter, or one of its
+    /// counters.
+    pub fn is_letter(&self, lp: &Loop2) -> bool {
+        let Some(p) = lp.segs.first().map(Seg2::start) else { return false };
+        self.regions.iter().any(|(lo, hi, curves)| p.x >= lo.x && p.x <= hi.x && p.y >= lo.y && p.y <= hi.y && loop_lies_on(lp, curves))
+    }
+}
+
 /// Bounded overlap predicate, including crossing-only cuts whose vertices lie outside a panel.
 pub(crate) fn flat_regions_overlap(a: &Region2, b: &Region2, work: &mut FlatWork) -> Result<bool> {
     let (a, b) = (planar_region(a)?, planar_region(b)?);
@@ -3974,6 +4133,7 @@ pub fn base_flange(body: &str, rule: &str, rv: &RuleValues, plane: Plane, region
         pockets: Vec::new(),
         bores: Vec::new(),
         perforations: Vec::new(),
+        labels: Vec::new(),
         flat: false,
         gap: rv.gap,
         relief: rv.corner_relief_shape,
@@ -4031,6 +4191,7 @@ pub fn contour_flange(body: &str, rule: &str, rv: &RuleValues, plane: &Plane, pt
         pockets: Vec::new(),
         bores: Vec::new(),
         perforations: Vec::new(),
+        labels: Vec::new(),
         flat: false,
         gap: rv.gap,
         relief: rv.corner_relief_shape,
@@ -4096,7 +4257,9 @@ pub fn rename_plane_sheet_body(plane: &mut crate::PlaneRef, old: &str, new: &str
                 *name = renamed;
             }
         }
-        crate::PlaneRef::Offset { base, .. } | crate::PlaneRef::AtAngle { base, .. } => rename_plane_sheet_body(base, old, new),
+        crate::PlaneRef::Offset { base, .. } | crate::PlaneRef::AtAngle { base, .. } | crate::PlaneRef::Flipped { base, .. } => {
+            rename_plane_sheet_body(base, old, new)
+        }
         _ => {}
     }
 }
@@ -4106,7 +4269,9 @@ pub fn rename_plane_sheet_body(plane: &mut crate::PlaneRef, old: &str, new: &str
 pub fn plane_sheet_face(plane: &crate::PlaneRef) -> Option<&str> {
     match plane {
         crate::PlaneRef::Face { name: Some(name), anchor: None, .. } if split_sheet_face_name(name).is_some() => Some(name),
-        crate::PlaneRef::Offset { base, .. } | crate::PlaneRef::AtAngle { base, .. } => plane_sheet_face(base),
+        crate::PlaneRef::Offset { base, .. } | crate::PlaneRef::AtAngle { base, .. } | crate::PlaneRef::Flipped { base, .. } => {
+            plane_sheet_face(base)
+        }
         _ => None,
     }
 }
@@ -4175,6 +4340,41 @@ mod tests {
         kernel::measure(b).map(|m| m.volume).unwrap_or(f64::NAN)
     }
 
+    #[test]
+    fn loops_lie_on_the_curves_they_are_made_of() {
+        let circle = Loop2::circle(Vec2::new(5.0, 5.0), 3.0);
+        let curves: Vec<Seg2> = circle.segs.clone();
+        // The loop itself, started elsewhere and run the other way, and a loop of its halves.
+        assert!(loop_lies_on(&circle, &curves));
+        assert!(loop_lies_on(&Loop2::circle_from(Vec2::new(5.0, 5.0), 3.0, 1.0).reversed(), &curves));
+        let halves: Vec<Seg2> = circle.segs.iter().flat_map(|g| [g.split_half().0, g.split_half().1]).collect();
+        assert!(loop_lies_on(&Loop2 { segs: halves }, &curves));
+        // Another circle, a square and an empty loop do not.
+        assert!(!loop_lies_on(&Loop2::circle(Vec2::new(5.0, 5.0), 3.1), &curves));
+        assert!(!loop_lies_on(&Loop2::circle(Vec2::new(5.0, 5.0), 2.0), &curves));
+        assert!(!loop_lies_on(&rect(Vec2::ZERO, Vec2::X, Vec2::new(1.0, 1.0), Vec2::Y).outer, &curves));
+        assert!(!loop_lies_on(&Loop2 { segs: Vec::new() }, &curves));
+        // A loop only partly on them (a letter across the sheet's edge) is not on them.
+        let notch = Loop2 { segs: vec![circle.segs[0], Seg2::Line { a: circle.segs[0].end(), b: Vec2::new(50.0, 50.0) }] };
+        assert!(!loop_lies_on(&notch, &curves));
+    }
+
+    #[test]
+    fn a_sheet_knows_the_letters_it_carries() {
+        // A recorded text region with a counter: its outline and its counter are letters, the same
+        // circle elsewhere, a loop near it that is another size and a loop far away are not.
+        let mut s = plate(100.0, 60.0);
+        let counter = Loop2::circle(Vec2::new(20.0, 20.0), 2.0).reversed();
+        s.labels.push(Region2 { outer: Loop2::circle(Vec2::new(20.0, 20.0), 5.0), holes: vec![counter.clone()] });
+        let letters = s.letters();
+        assert!(letters.is_letter(&Loop2::circle(Vec2::new(20.0, 20.0), 5.0)));
+        assert!(letters.is_letter(&counter.reversed()));
+        assert!(!letters.is_letter(&Loop2::circle(Vec2::new(20.0, 20.0), 4.0)));
+        assert!(!letters.is_letter(&Loop2::circle(Vec2::new(70.0, 20.0), 5.0)));
+        // A sheet that carries none has no letters.
+        assert!(!plate(100.0, 60.0).letters().is_letter(&Loop2::circle(Vec2::new(20.0, 20.0), 5.0)));
+    }
+
     #[test]
     fn edge_flange_matches_fusion() {
         // Oracle 68: 100 x 60 plate, 20 mm flange on the y = 0 top edge.
@@ -5898,7 +6098,7 @@ mod tests {
     /// sheet and the notes on corners left open.
     fn flanges_each(base: Region2, rv: &RuleValues, each: &[EdgeFlange]) -> (SheetBody, Vec<String>) {
         let mut s = base_flange("Body1", "AL2", rv, Plane::XY, base);
-        let notes = s.add_flanges_each(each, rv.bend_radius, "inside", false).unwrap().1;
+        let notes = s.add_flanges_each(each, rv.bend_radius, "inside", false, ReliefOverride::default()).unwrap().1;
         (s, notes)
     }
 
@@ -6453,7 +6653,7 @@ mod tests {
         let (mut s, _) = tray(&rv, 90.0, 20.0);
         let each: Vec<EdgeFlange> =
             (0..4).map(|i| EdgeFlange { pick: far_edge_pick(&s, i, true), height: 12.0, angle: [90f64, 70.0][i % 2].to_radians() }).collect();
-        let (made, notes) = s.add_flanges_each(&each, 1.0, "inside", false).unwrap();
+        let (made, notes) = s.add_flanges_each(&each, 1.0, "inside", false, ReliefOverride::default()).unwrap();
         assert!(notes.is_empty() && made == [4, 5, 6, 7], "{made:?} {notes:?}");
         for (a, a_end, b, b_end) in TRAY_RETURNS {
             let (fa, fb) = (&s.flanges[a], &s.flanges[b]);
@@ -6626,7 +6826,7 @@ mod tests {
                     EdgeFlange { pick: far_edge_pick(&s, i, true), height: 12.0, angle: deg.to_radians() }
                 })
                 .collect();
-            let (_, notes) = s.add_flanges_each(&each, 1.0, "inside", false).unwrap();
+            let (_, notes) = s.add_flanges_each(&each, 1.0, "inside", false, ReliefOverride::default()).unwrap();
             assert!(notes.is_empty(), "{what}: {notes:?}");
             returns_keep_out_of_the_walls(&s, &what);
             holds_the_flat_material(&s, &what);
@@ -7292,4 +7492,49 @@ mod tests {
             holds_the_flat_material(&s, &what);
         }
     }
+
+    /// The 100 x 60 plate with a 20 mm flange on its y = 0 edge (2.5 mm, R 2.5, K 0.44): in the
+    /// flat the base starts at y = t + R = 5, the bend's zone is (π/2)·(R + K·t) long and the
+    /// flange's panel 20 − 5, so its far edge lies at y = 5 − (π/2)·3.6 − 15.
+    #[test]
+    fn a_cut_names_the_pieces_it_parts_from_the_base_and_no_others() {
+        use std::f64::consts::{FRAC_PI_2, PI};
+        let far = 5.0 - FRAC_PI_2 * (2.5 + 0.44 * 2.5) - 15.0;
+        let mut s = plate(100.0, 60.0);
+        s.add_flange(Vec3::new(50.0, 0.0, 2.5), 20.0, FRAC_PI_2, 2.5, "inside", false).unwrap();
+        let r = |x0: f64, y0: f64, x1: f64, y1: f64| rect(Vec2::new(x0, y0), Vec2::new(x1, y0), Vec2::new(x1, y1), Vec2::new(x0, y1));
+        let ring = |c: Vec2, ro: f64, ri: f64| Region2 { outer: Loop2::circle(c, ro), holes: vec![Loop2::circle(c, ri)] };
+        let parted = |before: &SheetBody, holes: &[Region2]| {
+            let mut after = before.clone();
+            after.holes.extend_from_slice(holes);
+            after.parted_from_base(&after.flat_material().unwrap(), before).unwrap()
+        };
+        // A slot across the flange beside its bend parts the rest of the flange: 100 × (−3 − far).
+        let slot = r(-5.0, -3.0, 105.0, -1.0);
+        let p = parted(&s, std::slice::from_ref(&slot));
+        assert!(p.len() == 1 && (p[0].area() - 100.0 * (-3.0 - far)).abs() < 1e-6, "{p:?}");
+        // So does a ring on the flange's far edge: the half of its inside on the flange, π·2²/2.
+        let p = parted(&s, &[ring(Vec2::new(50.0, far), 4.0, 2.0)]);
+        assert!(p.len() == 1 && (p[0].area() - 2.0 * PI).abs() < 1e-6, "{p:?}");
+        // A ring's island, on the base or on the flange, has material round it; a strip across the
+        // whole sheet leaves two halves that each keep their part of the base. None is named.
+        for holes in [ring(Vec2::new(50.0, 30.0), 10.0, 5.0), ring(Vec2::new(50.0, -9.0), 4.0, 2.0), r(45.0, -30.0, 55.0, 70.0)] {
+            assert!(parted(&s, std::slice::from_ref(&holes)).is_empty(), "{holes:?}");
+        }
+        // Pieces an earlier cut parted are not named again, nor when a later cut splits them.
+        let mut cut = s.clone();
+        cut.holes.push(slot);
+        for holes in [Region2 { outer: Loop2::circle(Vec2::new(30.0, 30.0), 4.0), holes: vec![] }, r(45.0, -30.0, 55.0, -2.0)] {
+            assert!(parted(&cut, std::slice::from_ref(&holes)).is_empty(), "{holes:?}");
+        }
+        // Nothing is named once no piece holds the base: a cut that takes the base and both bends
+        // of a sheet with flanges on two sides leaves the two flanges.
+        let mut two = plate(100.0, 60.0);
+        two.add_flanges(&[Vec3::new(50.0, 0.0, 2.5), Vec3::new(50.0, 60.0, 2.5)], 20.0, FRAC_PI_2, 2.5, "inside", false).unwrap();
+        let mut after = two.clone();
+        after.holes.push(r(-5.0, -3.0, 105.0, 63.0));
+        let material = after.flat_material().unwrap();
+        assert_eq!(material.len(), 2);
+        assert!(after.parted_from_base(&material, &two).unwrap().is_empty());
+    }
 }

crates/doc/src/sheet_convert.rs

@@ -11,6 +11,14 @@
 //! two panels that is no bend is cut open: each panel ends square to the sheet, half the rule's
 //! gap from the plane halfway between the two.
 //!
+//! The bends on the fixed face are finished as the flanges of one edge flange feature are: where
+//! two meet at a corner of it, their walls are closed with the rule's gap and the corner gets the
+//! rule's corner relief (round, rectangular, a tear, or the notch the bends leave), and where one
+//! ends beside more of the fixed face, the rule's bend relief is cut there. A wall that stands on
+//! part of an edge of the fixed face (its outside in one plane with the plate's edge, which runs
+//! on past it a strip no taller than the bend's setback) bends only where it stands: the strip is
+//! the fixed face's own edge.
+//!
 //! A bend can also be a chamfer: a flat strip between two faces, as a model without bend radii
 //! draws a bend (the chord of its arc). Picked in its middle, the strip is no face of the sheet:
 //! the faces on either side are taken out to where their planes meet, and that line is the
@@ -37,7 +45,7 @@
 //! Not supported yet: curved faces other than bends (rolled sheet), holes and pockets that reach
 //! into a bend, pockets deeper than half the sheet or with a step or a hole in their floor, round
 //! edges that end at a bend or a cut edge, loops of bends, two faces that meet along more than
-//! one edge.
+//! one edge, a wall on part of an edge of a face other than the fixed one.
 
 use std::collections::BTreeMap;
 use std::f64::consts::{FRAC_PI_2, PI, TAU};
@@ -45,7 +53,7 @@ use std::f64::consts::{FRAC_PI_2, PI, TAU};
 use solidcraft_geom::{Loop2, Mesh, Plane, Region2, Seg2, Vec2, Vec3};
 use solidcraft_kernel::{Body, FaceSurface, face_surface};
 
-use super::{FlatWork, RuleValues, SheetBody, SheetFlange, base_flange, point_in, polys_cross, signed_area, snap};
+use super::{FlatWork, ReliefOverride, RuleValues, SheetBody, SheetFlange, base_flange, point_in, polys_cross, signed_area, snap};
 use crate::{DocError, ModelBody, Result, apply_point, mat_inverse};
 
 const MAX_BENDS: usize = 1000;
@@ -500,6 +508,96 @@ fn inset(pts: &[Vec2], by: &[f64]) -> Result<(Vec<Vec2>, Vec<Option<usize>>)> {
     Ok((out, from))
 }
 
+/// A wall standing on part of an edge of the fixed face: where the outline of `wall`, the face
+/// across a bend from the fixed face `base` (`ids`: the two faces), leaves the bend's edge up a
+/// strip no taller than the bend's setback `by`, runs back along the edge and climbs the wall's
+/// end, the strip is the fixed face's own edge (a plate's edge face in one plane with the outside
+/// of a wall that stands on part of it), which the setback would use up. It is cut off the wall,
+/// whose bend's edge then ends where the line of the wall's end meets it, and the fixed face's
+/// edge is split there: the pieces beside the wall are no bend. `bend` says whether a face is a
+/// bend of the wall. Any other wall is left as it is.
+fn end_at_wall(base: &mut Face, wall: &mut Face, ids: (usize, usize), by: f64, bend: &dyn Fn(usize) -> bool, tol: f64) {
+    let (m, n) = (wall.pts.len(), base.pts.len());
+    let at_wall: Vec<usize> = (0..m).filter(|i| wall.across.get(*i).copied().flatten() == Some(ids.0)).collect();
+    let at_base: Vec<usize> = (0..n).filter(|i| base.across.get(*i).copied().flatten() == Some(ids.1)).collect();
+    let (&[k], &[i]) = (at_wall.as_slice(), at_base.as_slice()) else { return };
+    if m < 5 {
+        return;
+    }
+    // Corner `j` and edge `j` (from corner `j`) counted from the bend's edge on.
+    let pt = |j: usize| wall.pts.get((k + j) % m).copied().unwrap_or_default();
+    let (p, q) = (pt(0), pt(1));
+    let Some(d) = (q - p).normalized() else { return };
+    // Up the wall from the bend's edge (the outline runs counter-clockwise about the normal), and
+    // along the edge.
+    let up = |x: Vec3| (x - p).dot(wall.n.cross(d));
+    let along = |x: Vec3| (x - p).dot(d);
+    let free = |j: usize| {
+        let j = (k + j) % m;
+        wall.round.get(j).is_some_and(Option::is_none) && wall.across.get(j).copied().flatten().is_none_or(|g| !bend(g))
+    };
+    let low = |x: Vec3| up(x) > tol && up(x) <= by + tol;
+    // A strip from an end of the bend's edge up to `x1`, back along the edge (`back`: the way it
+    // runs) to `x2`, then the wall's end up to `x3`: where the line of that end meets the edge.
+    let foot = |x1: Vec3, x2: Vec3, x3: Vec3, back: f64| {
+        let rise = up(x3) - up(x2);
+        (low(x1) && low(x2) && (x2 - x1).dot(d) * back > tol && rise > tol).then(|| x2 - (x3 - x2) * (up(x2) / rise))
+    };
+    // At the edge's end the strip is edges 1 and 2, the wall's end edge 3; at its start the strip
+    // is edges m - 1 and m - 2, the wall's end edge m - 3.
+    let ok = |js: [usize; 3]| js.iter().all(|j| free(*j));
+    let end = if ok([1, 2, 3]) { foot(pt(2), pt(3), pt(4), -1.0) } else { None };
+    let start = if ok([m - 1, m - 2, m - 3]) { foot(pt(m - 1), pt(m - 2), pt(m - 3), 1.0) } else { None };
+    let (p1, q1) = (start.unwrap_or(p), end.unwrap_or(q));
+    let len = along(q);
+    let inside = |x: Option<Vec3>| x.is_none_or(|x| along(x) > tol && along(x) < len - tol);
+    if (start.is_none() && end.is_none())
+        || !inside(start)
+        || !inside(end)
+        || along(q1) - along(p1) <= tol
+        || (start.is_some() && end.is_some() && m < 7)
+    {
+        return;
+    }
+    // The wall: the strips' corners and edges go, the bend's edge runs from `p1` to `q1`.
+    let (mut corners_out, mut edges_out) = (Vec::new(), Vec::new());
+    if end.is_some() {
+        corners_out.extend([2, 3]);
+        edges_out.extend([1, 2]);
+    }
+    if start.is_some() {
+        corners_out.extend([m - 1, m - 2]);
+        edges_out.extend([m - 1, m - 2]);
+    }
+    if let Some(x) = wall.pts.get_mut(k) {
+        *x = p1;
+    }
+    if let Some(x) = wall.pts.get_mut((k + 1) % m) {
+        *x = q1;
+    }
+    let kept = |j: usize, out: &[usize]| !out.contains(&((j + m - k) % m));
+    wall.pts = wall.pts.iter().enumerate().filter(|(j, _)| kept(*j, &corners_out)).map(|(_, x)| *x).collect();
+    wall.across = wall.across.iter().enumerate().filter(|(j, _)| kept(*j, &edges_out)).map(|(_, x)| *x).collect();
+    wall.round = wall.round.iter().enumerate().filter(|(j, _)| kept(*j, &edges_out)).map(|(_, x)| *x).collect();
+    // The fixed face's edge: the bend from `p1` to `q1` (it runs the other way along it), no bend
+    // beside it.
+    let (Some(&a), Some(&b)) = (base.pts.get(i), base.pts.get((i + 1) % n)) else { return };
+    let from_a = |x: Vec3| (x - a).dot(b - a);
+    let (x, y) = if from_a(p1) < from_a(q1) { (p1, q1) } else { (q1, p1) };
+    let mut pieces: Vec<(Vec3, Option<usize>)> = Vec::with_capacity(3);
+    if x.dist(a) > tol {
+        pieces.push((a, None));
+    }
+    pieces.push((if x.dist(a) > tol { x } else { a }, Some(ids.1)));
+    if y.dist(b) > tol {
+        pieces.push((y, None));
+    }
+    let count = pieces.len();
+    base.pts.splice(i..=i, pieces.iter().map(|(x, _)| *x));
+    base.across.splice(i..=i, pieces.iter().map(|(_, g)| *g));
+    base.round.splice(i..=i, std::iter::repeat_n(None, count));
+}
+
 /// Give flange `i` its panel: `outline` in flat coordinates, counter-clockwise, its edge at the
 /// bend first trimmed to the end of the bend zone.
 fn set_panel(sh: &mut SheetBody, i: usize, outline: &[Vec2]) {
@@ -574,7 +672,8 @@ pub fn bend_edge_names(st: &crate::ModelState, body: &str, pts: &[Vec3]) -> Vec<
 /// Convert body `mb` to a sheet under the rule `rule` with values `rv`: `face` is a point on the
 /// fixed face and `bends` are points on the sharp edges that become bends, in the middle of
 /// chamfers or on bend cylinders that do (the body's coordinates, mm). See the module docs.
-pub fn convert_body(mb: &ModelBody, rule: &str, rv: &RuleValues, face: Vec3, bends: &[Vec3]) -> Result<SheetBody> {
+/// Returns the sheet and a note for every corner or end of a bend not finished as the rule says.
+pub fn convert_body(mb: &ModelBody, rule: &str, rv: &RuleValues, face: Vec3, bends: &[Vec3]) -> Result<(SheetBody, Vec<String>)> {
     if bends.is_empty() || bends.len() > MAX_BENDS {
         return err(format!("pick 1…{MAX_BENDS} bend edges"));
     }
@@ -696,6 +795,20 @@ pub fn convert_body(mb: &ModelBody, rule: &str, rv: &RuleValues, face: Vec3, ben
         .and_then(|(a, b)| Some((*a, (*b - *a).normalized()?)))
         .and_then(|(a, x)| Plane::new(a, x, x.cross(base.face.n)))
         .ok_or_else(|| DocError::Invalid("the fixed face has no plane".into()))?;
+    // A wall on part of an edge of the fixed face bends only where it stands (a bend picked as a
+    // chamfer or a cylinder is taken as it is).
+    let walls: Vec<(usize, f64)> = panels.iter().filter(|(_, p)| p.parent == Some(f0)).map(|(g, p)| (*g, p.setback)).collect();
+    for (g, by) in walls {
+        if chamfers.iter().any(|c| (c.a, c.b) == (f0, g) || (c.a, c.b) == (g, f0)) {
+            continue;
+        }
+        let kids: Vec<usize> = panels.iter().filter(|(_, p)| p.parent == Some(g)).map(|(h, _)| *h).collect();
+        let Some(mut wall) = panels.remove(&g) else { continue };
+        if let Some(base) = panels.get_mut(&f0) {
+            end_at_wall(&mut base.face, &mut wall.face, (f0, g), by, &|h| h == f0 || kids.contains(&h), tol);
+        }
+        panels.insert(g, wall);
+    }
     let mut sh = base_flange(&mb.name, rule, &RuleValues { thickness: t, ..*rv }, frame, Region2::default());
     // How far behind a face of the sheet the body's face `g` starts and ends: a hole's wall
     // reaches through the sheet, a pocket's ends on its floor, an island's starts at the face.
@@ -872,7 +985,25 @@ pub fn convert_body(mb: &ModelBody, rule: &str, rv: &RuleValues, face: Vec3, ben
             queue.push((g, Some(sh.flanges.len() - 1)));
         }
     }
-    Ok(sh)
+    // The bends on the fixed face finished as an edge flange feature finishes its own
+    // (`SheetBody::add_flanges_each`): the rule's bend relief where one ends beside more of the
+    // fixed face; where two meet at a corner of it, their walls closed with the rule's gap (which
+    // the cuts above already are) and the rule's corner relief.
+    let made: Vec<usize> = (0..sh.flanges.len()).collect();
+    let mut notes = Vec::new();
+    for &i in &made {
+        notes.extend(sh.relieve_bend_ends(i, (false, false)));
+    }
+    let corners = sh.corners(&made);
+    let mut closed = Vec::with_capacity(corners.len());
+    for k in &corners {
+        match sh.close_corner(k) {
+            Ok(()) => closed.push(*k),
+            Err(why) => notes.push(format!("the corner at {} stays cut open: {why}", sh.shown(k.c))),
+        }
+    }
+    notes.extend(sh.relieve_corners(&corners, &closed, ReliefOverride::default()));
+    Ok((sh, notes))
 }
 
 #[cfg(test)]

crates/doc/src/tests.rs

@@ -30,7 +30,7 @@ fn plate_doc() -> (Document, u64) {
     doc.add_feature(
         FeatureKind::Extrude {
             thin: None,
-            sketch: s,
+            sketch: crate::SketchId(s),
             profiles: ProfileSel::All,
             extent: Extent {
                 convention: crate::ExtrudeConvention::LegacyPerSide,
@@ -108,7 +108,7 @@ fn box_fillet_cut_timeline() {
     let (mut doc, _) = plate_doc();
     doc.add_feature(
         FeatureKind::Fillet {
-            edges: vec![Vec3::new(0.0, 0.0, 10.0)],
+            edges: vec![Position(Vec3::new(0.0, 0.0, 10.0))],
             radius: "3".into(),
             body: None,
             style: Default::default(),
@@ -123,7 +123,7 @@ fn box_fillet_cut_timeline() {
     doc.add_feature(
         FeatureKind::Extrude {
             thin: None,
-            sketch: s2,
+            sketch: crate::SketchId(s2),
             profiles: ProfileSel::Points { points: vec![Vec2::new(20.0, 15.0)] },
             extent: Extent {
                 convention: crate::ExtrudeConvention::LegacyPerSide,
@@ -162,7 +162,7 @@ fn errors_are_reported_not_fatal() {
     let (mut doc, s) = plate_doc();
     doc.add_feature(
         FeatureKind::Revolve {
-            sketch: s,
+            sketch: crate::SketchId(s),
             profiles: ProfileSel::All,
             axis: AxisRef::SketchAxis { axis: "y".into() },
             angle: "90 deg".into(),
@@ -178,7 +178,7 @@ fn errors_are_reported_not_fatal() {
     .unwrap();
     doc.add_feature(
         FeatureKind::Fillet {
-            edges: vec![Vec3::new(500.0, 0.0, 0.0)],
+            edges: vec![Position(Vec3::new(500.0, 0.0, 0.0))],
             radius: "1".into(),
             body: None,
             style: Default::default(),
@@ -244,7 +244,7 @@ fn primitives_and_combine() {
     doc.add_feature(
         FeatureKind::Cylinder {
             base: point_expr(Vec3::new(5.0, 5.0, 0.0)),
-            axis: Vec3::Z,
+            axis: Dir(Vec3::Z),
             radius: "2".into(),
             height: "20".into(),
             operation: Operation::NewBody,

crates/doc/src/walk.rs

@@ -13,13 +13,13 @@ pub(crate) use crate::expr::Kind;
 pub(crate) use crate::feature_geometry::Geo;
 pub(crate) use crate::feature_refs::Ref;
 pub(crate) use crate::params::ExprRole;
-use crate::{PlaneRef, PointExpr};
+use crate::{BodyName, Dir, Expr, FacePick, FeatureName, PlaneRef, PointExpr, Position, SketchId};
 
 /// An expression: its label, the expression, its kind and its role.
-pub(crate) type ExprItem<'a> = (&'static str, &'a String, Kind, ExprRole);
-pub(crate) type ExprItemMut<'a> = (&'static str, &'a mut String, Kind, ExprRole);
-pub(crate) type RefItem<'a> = Ref<&'a u64, &'a String>;
-pub(crate) type RefItemMut<'a> = Ref<&'a mut u64, &'a mut String>;
+pub(crate) type ExprItem<'a> = (&'static str, &'a Expr, Kind, ExprRole);
+pub(crate) type ExprItemMut<'a> = (&'static str, &'a mut Expr, Kind, ExprRole);
+pub(crate) type RefItem<'a> = Ref<&'a SketchId, &'a FeatureName, &'a BodyName>;
+pub(crate) type RefItemMut<'a> = Ref<&'a mut SketchId, &'a mut FeatureName, &'a mut BodyName>;
 pub(crate) type GeoItem<'a> = Geo<&'a Vec3, &'a PlaneRef, &'a GeoRef, &'a PointExpr, &'a ProfileSel>;
 pub(crate) type GeoItemMut<'a> = Geo<&'a mut Vec3, &'a mut PlaneRef, &'a mut GeoRef, &'a mut PointExpr, &'a mut ProfileSel>;
 
@@ -40,10 +40,14 @@ impl Walk for bool {}
 impl Walk for u64 {}
 impl Walk for i8 {}
 impl Walk for f64 {}
+impl Walk for usize {}
+impl Walk for u32 {}
 impl Walk for ProfileSel {}
 impl Walk for solidcraft_sketch::Sketch {}
+impl Walk for solidcraft_sketch::PatternAlignment {}
 impl Walk for solidcraft_kernel::StepNode {}
 impl Walk for crate::document::Operation {}
+impl Walk for solidcraft_kernel::Continuity {}
 impl Walk for crate::document::Direction {}
 impl Walk for crate::document::FilletFit {}
 impl Walk for crate::document::MeshData {}
@@ -55,6 +59,52 @@ impl Walk for crate::document::RuledMode {}
 impl Walk for crate::document::RuledCorners {}
 impl Walk for crate::document::ExtrudeConvention {}
 
+/// A reference walks itself: a sketch, a feature or a body.
+macro_rules! reference {
+    ($t:ty, $role:ident) => {
+        impl Walk for $t {
+            fn walk_refs<'a>(&'a self, f: &mut dyn FnMut(RefItem<'a>)) {
+                f(Ref::$role(self))
+            }
+            fn walk_refs_mut<'a>(&'a mut self, f: &mut dyn FnMut(RefItemMut<'a>)) {
+                f(Ref::$role(self))
+            }
+        }
+    };
+}
+
+reference!(SketchId, Sketch);
+reference!(FeatureName, Feature);
+reference!(BodyName, Body);
+
+/// A point walks itself with its role: a face pick, a position or a direction. As a plain
+/// `Vec3` it also serves a field whose attribute gives it another role (`pinned`, `pick_if`).
+macro_rules! point {
+    ($t:ty, $role:ident) => {
+        impl Walk for $t {
+            fn walk_geometry<'a>(&'a self, f: &mut dyn FnMut(GeoItem<'a>)) {
+                f(Geo::$role(&self.0))
+            }
+            fn walk_geometry_mut<'a>(&'a mut self, f: &mut dyn FnMut(GeoItemMut<'a>)) {
+                f(Geo::$role(&mut self.0))
+            }
+        }
+
+        impl Each<Vec3> for $t {
+            fn each<'a>(&'a self, f: &mut dyn FnMut(&'a Vec3)) {
+                f(&self.0)
+            }
+            fn each_mut<'a>(&'a mut self, f: &mut dyn FnMut(&'a mut Vec3)) {
+                f(&mut self.0)
+            }
+        }
+    };
+}
+
+point!(FacePick, Pick);
+point!(Position, Pos);
+point!(Dir, Dir);
+
 /// Containers walk what they hold, in order.
 macro_rules! walk_each {
     ($([$($g:tt)*] $t:ty),*) => {$(
@@ -136,6 +186,36 @@ impl<T> Each<T> for Vec<T> {
     }
 }
 
+impl<T, const N: usize> Each<T> for [T; N] {
+    fn each<'a>(&'a self, f: &mut dyn FnMut(&'a T)) {
+        for t in self {
+            f(t)
+        }
+    }
+    fn each_mut<'a>(&'a mut self, f: &mut dyn FnMut(&'a mut T)) {
+        for t in self {
+            f(t)
+        }
+    }
+}
+
+impl<T, const N: usize> Each<T> for Option<[T; N]> {
+    fn each<'a>(&'a self, f: &mut dyn FnMut(&'a T)) {
+        if let Some(a) = self {
+            for t in a {
+                f(t)
+            }
+        }
+    }
+    fn each_mut<'a>(&'a mut self, f: &mut dyn FnMut(&'a mut T)) {
+        if let Some(a) = self {
+            for t in a {
+                f(t)
+            }
+        }
+    }
+}
+
 impl<T> Each<T> for Option<Vec<T>> {
     fn each<'a>(&'a self, f: &mut dyn FnMut(&'a T)) {
         for t in self.iter().flatten() {
@@ -151,36 +231,36 @@ impl<T> Each<T> for Option<Vec<T>> {
 
 /// The expressions of an expression field, each with its index and their count (for its label).
 pub(crate) trait ExprField {
-    fn each<'a>(&'a self, f: &mut dyn FnMut(usize, usize, &'a String));
-    fn each_mut<'a>(&'a mut self, f: &mut dyn FnMut(usize, usize, &'a mut String));
+    fn each<'a>(&'a self, f: &mut dyn FnMut(usize, usize, &'a Expr));
+    fn each_mut<'a>(&'a mut self, f: &mut dyn FnMut(usize, usize, &'a mut Expr));
 }
 
-impl ExprField for String {
-    fn each<'a>(&'a self, f: &mut dyn FnMut(usize, usize, &'a String)) {
+impl ExprField for Expr {
+    fn each<'a>(&'a self, f: &mut dyn FnMut(usize, usize, &'a Expr)) {
         f(0, 1, self)
     }
-    fn each_mut<'a>(&'a mut self, f: &mut dyn FnMut(usize, usize, &'a mut String)) {
+    fn each_mut<'a>(&'a mut self, f: &mut dyn FnMut(usize, usize, &'a mut Expr)) {
         f(0, 1, self)
     }
 }
 
 /// A position along an edge with its radius (a variable fillet's mid radii).
-impl ExprField for (f64, String) {
-    fn each<'a>(&'a self, f: &mut dyn FnMut(usize, usize, &'a String)) {
+impl ExprField for (f64, Expr) {
+    fn each<'a>(&'a self, f: &mut dyn FnMut(usize, usize, &'a Expr)) {
         f(0, 1, &self.1)
     }
-    fn each_mut<'a>(&'a mut self, f: &mut dyn FnMut(usize, usize, &'a mut String)) {
+    fn each_mut<'a>(&'a mut self, f: &mut dyn FnMut(usize, usize, &'a mut Expr)) {
         f(0, 1, &mut self.1)
     }
 }
 
 impl<T: ExprField> ExprField for Option<T> {
-    fn each<'a>(&'a self, f: &mut dyn FnMut(usize, usize, &'a String)) {
+    fn each<'a>(&'a self, f: &mut dyn FnMut(usize, usize, &'a Expr)) {
         if let Some(t) = self {
             t.each(f)
         }
     }
-    fn each_mut<'a>(&'a mut self, f: &mut dyn FnMut(usize, usize, &'a mut String)) {
+    fn each_mut<'a>(&'a mut self, f: &mut dyn FnMut(usize, usize, &'a mut Expr)) {
         if let Some(t) = self {
             t.each_mut(f)
         }
@@ -191,13 +271,13 @@ impl<T: ExprField> ExprField for Option<T> {
 macro_rules! expr_list {
     ($([$($g:tt)*] $t:ty),*) => {$(
         impl<$($g)*> ExprField for $t {
-            fn each<'a>(&'a self, f: &mut dyn FnMut(usize, usize, &'a String)) {
+            fn each<'a>(&'a self, f: &mut dyn FnMut(usize, usize, &'a Expr)) {
                 let n = self.len();
                 for (i, t) in self.iter().enumerate() {
                     t.each(&mut |_, _, e| f(i, n, e));
                 }
             }
-            fn each_mut<'a>(&'a mut self, f: &mut dyn FnMut(usize, usize, &'a mut String)) {
+            fn each_mut<'a>(&'a mut self, f: &mut dyn FnMut(usize, usize, &'a mut Expr)) {
                 let n = self.len();
                 for (i, t) in self.iter_mut().enumerate() {
                     t.each_mut(&mut |_, _, e| f(i, n, e));
@@ -233,8 +313,9 @@ impl<F: Fn(usize, usize) -> &'static str> Label for F {
     }
 }
 
-/// The offsets and angles of a plane, outermost first (nesting is capped like every walk over a
-/// plane), the construction plane it is built on, and the plane itself.
+/// The offsets and angles of a plane, outermost first, and an explicit origin's coordinates
+/// (nesting is capped like every walk over a plane), the construction plane it is built on, and
+/// the plane itself.
 impl Walk for PlaneRef {
     fn walk_exprs<'a>(&'a self, f: &mut dyn FnMut(ExprItem<'a>)) {
         let mut p = self;
@@ -249,6 +330,12 @@ impl Walk for PlaneRef {
                     p = base;
                 }
                 PlaneRef::AlongPath { t, .. } => return f(("Distance (0 to 1)", t, Kind::Unitless, ExprRole::Input)),
+                PlaneRef::Placed { origin, .. } => {
+                    for (label, e) in ["X", "Y", "Z"].into_iter().zip(origin) {
+                        f((label, e, Kind::Length, ExprRole::Placement));
+                    }
+                    return;
+                }
                 _ => return,
             }
         }
@@ -266,6 +353,12 @@ impl Walk for PlaneRef {
                     p = base;
                 }
                 PlaneRef::AlongPath { t, .. } => return f(("Distance (0 to 1)", t, Kind::Unitless, ExprRole::Input)),
+                PlaneRef::Placed { origin, .. } => {
+                    for (label, e) in ["X", "Y", "Z"].into_iter().zip(origin) {
+                        f((label, e, Kind::Length, ExprRole::Placement));
+                    }
+                    return;
+                }
                 _ => return,
             }
         }
@@ -274,7 +367,7 @@ impl Walk for PlaneRef {
         let mut p = self;
         for _ in 0..64 {
             match p {
-                PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } => p = base,
+                PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } | PlaneRef::Flipped { base, .. } => p = base,
                 PlaneRef::Construction { name } => return f(Ref::Feature(name)),
                 _ => return,
             }
@@ -284,7 +377,7 @@ impl Walk for PlaneRef {
         let mut p = self;
         for _ in 0..64 {
             match p {
-                PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } => p = base,
+                PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } | PlaneRef::Flipped { base, .. } => p = base,
                 PlaneRef::Construction { name } => return f(Ref::Feature(name)),
                 _ => return,
             }

crates/engine/src/boolean_regression_tests.rs

@@ -267,3 +267,48 @@ fn lip_swept_flush_round_a_corner_joins() {
     let volume = b.body.tessellate(1e-5).unwrap().measure().volume;
     assert!((volume - block - lip).abs() < 0.02, "{volume} expected {}", block + lip);
 }
+
+/// #1275: an Extrude Cut of a whole face of a rounded-rectangle block with a bottom chamfer. The
+/// tool's corner cylinders lay on the block's; they are grown off them now, as straight edges
+/// were, and the cut takes 5 mm off the top.
+#[test]
+fn cut_of_a_whole_face_beside_round_corners_after_a_chamfer() {
+    let s = replay(include_str!("../../../examples/regressions/cut_whole_face_after_bottom_chamfer.json"));
+    let bodies = &s.model.state().bodies;
+    assert_eq!(bodies.len(), 1);
+    let b = &bodies[0];
+    assert!(b.body.validity().is_empty(), "{:?}", b.body.validity());
+    let pi = std::f64::consts::PI;
+    let block = (40.0 * 40.0 - (4.0 - pi) * 8.0 * 8.0) * 15.0;
+    // The chamfer's 2 × 2 triangle swept along the loop (Pappus: its centroid is 2/3 mm in).
+    let chamfer = 2.0 * (4.0 * 24.0 + 2.0 * pi * (8.0 - 2.0 / 3.0));
+    let mesh = b.body.tessellate(1e-4).unwrap();
+    let volume = mesh.measure().volume;
+    assert!((volume - (block - chamfer)).abs() < 0.05, "{volume} expected {}", block - chamfer);
+    let top = mesh.bounds().max.z;
+    assert!((top - 15.0).abs() < 1e-6, "top at {top}");
+}
+
+/// The display tessellation of loft bodies joined into a bike frame plans at every display
+/// quality and every refinement step. The edge nodes on an intersection of two lofts once
+/// stepped back along the curve (the edge's fit rang where truck's parameter changes speed, and
+/// took a leader point off the curve past a vertex), so a face's boundary crossed itself and
+/// the body fell back to the reference mesher, which drew a sheet across the down tube.
+#[test]
+fn joined_loft_frames_plan_their_display_at_every_quality() {
+    use solidcraft_doc::display_quality::{DisplayQuality, MAX_REFINE};
+    for (script, name) in [
+        (include_str!("../../../examples/regressions/loft_join_bracket_hull_triangle.json"), "DT2"),
+        (include_str!("../../../examples/regressions/front_triangle_hull_triangle.json"), "FrontTriangle"),
+    ] {
+        let s = replay(script);
+        let state = s.model.state();
+        let body = &state.body(name).unwrap().body;
+        for q in DisplayQuality::ALL {
+            for k in 0..=MAX_REFINE {
+                let plan = body.display_plan_angular(q.refined_chord(body.size(), k), q.refined_angle(k));
+                assert!(plan.is_ok(), "{name} at {} + {k}: {:?}", q.id(), plan.err());
+            }
+        }
+    }
+}

crates/engine/src/capture.rs

@@ -0,0 +1,114 @@
+//! How headless pictures of the model are drawn: a renderer the host installs. The engine
+//! describes what a picture shows ([`crate::view::scene`]); drawing it is a GPU job the engine
+//! cannot do itself (the GPU crate sits above it), so the application, the CLI and the MCP
+//! server install one ([`install`]) that draws with the viewport's own pipelines (or, as a last
+//! resort the host chooses, the CPU rasterizer). Every picture names the renderer that drew it.
+//! Without a renderer, a picture is an error and a save simply has no thumbnail.
+
+use std::sync::{Arc, RwLock};
+
+use solidcraft_render::{Camera, Scene};
+
+/// A picture: straight RGBA, rows top to bottom, and the renderer that drew it (`gpu`,
+/// `gpu-software` or `cpu`).
+pub struct Picture {
+    pub rgba: Vec<u8>,
+    pub renderer: &'static str,
+}
+
+/// A picture as PNG bytes, and the renderer that drew it.
+pub struct Png {
+    pub bytes: Vec<u8>,
+    pub renderer: &'static str,
+}
+
+/// What a reply says when the CPU rasterizer drew the picture.
+pub const CPU_WARNING: &str = "drawn by the CPU rasterizer (no GPU adapter qualified, or SOLIDCRAFT_GPU=cpu): surface analysis colours, highlights and legends are not drawn; `solidcraft-cli gpu` lists the adapters";
+
+/// The warning that goes with a picture drawn by `renderer`, if any.
+pub fn warning(renderer: &str) -> Option<&'static str> {
+    (renderer == "cpu").then_some(CPU_WARNING)
+}
+
+/// Draws `scene` seen by `cam` at `width` × `height` pixels (`width * height * 4` bytes of RGBA),
+/// or says why it could not.
+pub type Renderer = dyn Fn(&Scene, &Camera, u32, u32) -> Result<Picture, String> + Send + Sync;
+
+static RENDERER: RwLock<Option<Arc<Renderer>>> = RwLock::new(None);
+
+/// Make `renderer` draw this process's headless pictures (replacing any installed before).
+pub fn install(renderer: Arc<Renderer>) {
+    if let Ok(mut r) = RENDERER.write() {
+        *r = Some(renderer);
+    }
+}
+
+/// The installed renderer, if any.
+pub fn installed() -> Option<Arc<Renderer>> {
+    RENDERER.read().ok().and_then(|r| r.clone())
+}
+
+/// `scene` drawn by the installed renderer.
+pub fn rgba(scene: &Scene, cam: &Camera, width: u32, height: u32) -> Result<Picture, String> {
+    rgba_with(installed().as_deref(), scene, cam, width, height)
+}
+
+/// `scene` drawn by the installed renderer, as PNG.
+pub fn png(scene: &Scene, cam: &Camera, width: u32, height: u32) -> Result<Png, String> {
+    png_with(installed().as_deref(), scene, cam, width, height)
+}
+
+/// [`rgba`] with `renderer` instead of the installed one.
+pub fn rgba_with(renderer: Option<&Renderer>, scene: &Scene, cam: &Camera, width: u32, height: u32) -> Result<Picture, String> {
+    let renderer = renderer.ok_or("no renderer is installed to draw pictures in this process")?;
+    let picture = renderer(scene, cam, width, height)?;
+    if picture.rgba.len() as u64 != u64::from(width) * u64::from(height) * 4 {
+        return Err(format!("the renderer returned {} bytes for {width} × {height} pixels", picture.rgba.len()));
+    }
+    if let Some(w) = warning(picture.renderer) {
+        log::warn!("{w}");
+    }
+    Ok(picture)
+}
+
+/// [`png`] with `renderer` instead of the installed one.
+pub fn png_with(renderer: Option<&Renderer>, scene: &Scene, cam: &Camera, width: u32, height: u32) -> Result<Png, String> {
+    let Picture { rgba, renderer } = rgba_with(renderer, scene, cam, width, height)?;
+    let bytes = solidcraft_render::png(width as usize, height as usize, rgba).ok_or_else(|| "PNG encoding failed".to_string())?;
+    Ok(Png { bytes, renderer })
+}
+
+/// For tests: a stand-in for the renderer the hosts install, a flat picture whose first byte
+/// counts the scene's meshes.
+#[cfg(test)]
+pub(crate) fn install_test_renderer() {
+    install(Arc::new(|scene: &Scene, _: &Camera, w: u32, h: u32| {
+        let mut rgba = vec![200; (w * h * 4) as usize];
+        if let Some(first) = rgba.first_mut() {
+            *first = scene.meshes.len() as u8;
+        }
+        Ok(Picture { rgba, renderer: "gpu" })
+    }));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn without_a_renderer_a_picture_is_an_error_not_a_crash() {
+        let e = png_with(None, &Scene::default(), &Camera::default(), 16, 16).err().unwrap();
+        assert!(e.contains("no renderer"), "{e}");
+    }
+
+    #[test]
+    fn a_renderer_that_returns_the_wrong_size_is_an_error() {
+        let short: &Renderer = &|_, _, _, _| Ok(Picture { rgba: vec![0; 3], renderer: "gpu" });
+        assert!(rgba_with(Some(short), &Scene::default(), &Camera::default(), 2, 2).is_err());
+        let plain: &Renderer = &|_, _, w, h| Ok(Picture { rgba: vec![255; (w * h * 4) as usize], renderer: "cpu" });
+        let png = png_with(Some(plain), &Scene::default(), &Camera::default(), 2, 2).unwrap();
+        assert!(png.bytes.starts_with(b"\x89PNG"));
+        assert_eq!(png.renderer, "cpu");
+        assert_eq!((warning("cpu"), warning("gpu"), warning("gpu-software")), (Some(CPU_WARNING), None, None));
+    }
+}

crates/engine/src/cmd/browser.rs

@@ -837,7 +837,7 @@ mod tests {
             solidcraft_doc::FeatureKind::Move { bodies, .. } => Some(bodies.clone()),
             _ => None,
         });
-        assert_eq!(moved, Some(vec!["Lid".to_string()]), "the move follows the rename");
+        assert_eq!(moved, Some(vec![solidcraft_doc::BodyName::from("Lid")]), "the move follows the rename");
         assert!(s.model.results.iter().all(|r| r.error.is_none()));
     }
 

crates/engine/src/cmd/clipboard.rs

@@ -45,7 +45,7 @@ fn explicit_planes(p: &mut PlaneRef) {
                 *p = PlaneRef::Custom { plane };
             }
         }
-        PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } => explicit_planes(base),
+        PlaneRef::Offset { base, .. } | PlaneRef::AtAngle { base, .. } | PlaneRef::Flipped { base, .. } => explicit_planes(base),
         _ => {}
     }
 }
@@ -374,9 +374,14 @@ mod tests {
         let second = run(&mut s, "file.insert_step", json!({"path": path.to_string_lossy()}))["feature"].clone();
         assert_eq!(body_names(&s), ["Aa", "Bb", "Cc", "Aa (2)", "Bb (2)", "Cc (2)"]);
         paste_import_with_two_lifts(&mut s, &second, ["Aa (2)", "Bb (2)", "Cc (2)"]);
+        // Each import is a component of its own (#1386), shown after the pasted copies: the first
+        // import's bodies stay where they were, the second's and their copies are lifted.
         let plain = [[0.0, 0.0, 0.0], [30.0, 0.0, 0.0], [60.0, 0.0, 0.0]];
-        let at: Vec<Vec<f64>> = plain.iter().chain(&LIFTED).chain(&LIFTED).map(|c| c.to_vec()).collect();
+        let at: Vec<Vec<f64>> = LIFTED.iter().chain(&plain).chain(&LIFTED).map(|c| c.to_vec()).collect();
         assert_eq!(corners(&mut s), at, "{:?}", body_names(&s));
+        let m = run(&mut s, "inspect.measure", json!({}));
+        let names: Vec<&str> = m["bodies"].as_array().unwrap().iter().filter_map(|b| b["name"].as_str()).collect();
+        assert_eq!(names, ["Aa (copy)", "Bb (copy)", "Cc (copy)", "Aa", "Bb", "Cc", "Aa (2)", "Bb (2)", "Cc (2)"]);
     }
 
     /// A cylinder Emboss finds its face by the persistent name it recorded when it was made. The
@@ -522,6 +527,9 @@ mod tests {
         assert_eq!(def["definition"]["targets"], json!(["Plate (copy)"]), "{def}");
         let st = s.world_state();
         let v = |name: &str| solidcraft_kernel::measure(&st.body(name).unwrap().body).unwrap().volume;
-        assert!((v("Plate") - v("Plate (copy)")).abs() < 1e-6, "each plate carries one spring: {} vs {}", v("Plate"), v("Plate (copy)"));
+        // A spring on the wrong plate is hundreds of mm³ off. The two plates are measured apart
+        // (one moved 50 mm), which the boolean and the measure each round in their own way:
+        // a few 1e-6 mm³ on 5000.
+        assert!((v("Plate") - v("Plate (copy)")).abs() < 1e-8 * v("Plate"), "each plate carries one spring: {} vs {}", v("Plate"), v("Plate (copy)"));
     }
 }

crates/engine/src/cmd/compare.rs

@@ -0,0 +1,309 @@
+//! Compare Bodies: two versions of one part laid over each other. Both are measured, each
+//! surface's distance to the other is sampled, and the places where only one of them has
+//! material are found, measured and, on request, coloured. It works from the surfaces
+//! ([`solidcraft_geom::compare`]), not from a boolean of the two bodies, so bodies that share
+//! almost every face compare as well as any.
+
+use serde_json::{Value, json};
+use solidcraft_geom::Vec3;
+use solidcraft_geom::compare::{self, CompareOptions, Side};
+
+use super::CommandSpec;
+use crate::params::bad;
+use crate::{Result, Sel, Session};
+
+pub static COMMANDS: &[CommandSpec] = &[CommandSpec::new("inspect.compare", "Compare Bodies", compare_bodies).params(
+    "a, b: body names (default: the two selected bodies, or the design's only two), in world placement; tolerance?: mm (0.001 to 10, default 0.01): \
+     surfaces closer than this agree; spacing?: mm (default 0.5): the largest piece of a face sampled as one point, coarser for a body that would need \
+     more than max_points? (default 8 million, up to 50 million) samples; max_regions? (default 50); color?: true | {only_in_a?, only_in_b?: \"#rrggbb\"} \
+     (colours the faces that hold a region, red where only a has material and green where only b has: the faces mostly beyond the tolerance, else the \
+     one with the largest share; an undo step) → a, b: volume_mm3, area_mm2, center_of_mass, bbox; difference: b − a; \
+     deviation: a_to_b, b_to_a (max_mm, mean_mm, at, area_beyond_mm2); regions, largest first: side (only_in_a | only_in_b), volume_mm3 (integrated along \
+     lines through the region: resolution), area_mm2, max_deviation_mm, at, center, bbox, faces_a, faces_b (face indices, as model.faces lists them); \
+     identical; verdict; warnings (a body whose surface does not enclose what it measures, lines left out). Works from the two surfaces, without a boolean of the bodies, so near-identical bodies compare too",
+)];
+
+/// Default colours: red for material only `a` has, green for material only `b` has.
+const ONLY_IN_A: [u8; 3] = [0xe0, 0x31, 0x31];
+const ONLY_IN_B: [u8; 3] = [0x2f, 0x9e, 0x44];
+
+fn side_name(s: Side) -> &'static str {
+    match s {
+        Side::OnlyInA => "only_in_a",
+        Side::OnlyInB => "only_in_b",
+    }
+}
+
+/// A number parameter in `range`, `default` when absent.
+fn number(cmd: &str, p: &Value, key: &str, default: f64, range: std::ops::RangeInclusive<f64>) -> Result<f64> {
+    match p.get(key) {
+        None | Some(Value::Null) => Ok(default),
+        Some(v) => v
+            .as_f64()
+            .filter(|x| x.is_finite() && range.contains(x))
+            .ok_or_else(|| bad(cmd, format!("`{key}` must be a number from {} to {}", range.start(), range.end()))),
+    }
+}
+
+/// The two bodies: `a` and `b`, else the two selected bodies, else the design's only two.
+fn pair(s: &Session, st: &solidcraft_doc::ModelState, p: &Value, cmd: &str) -> Result<(String, String)> {
+    let given = |k: &str| -> Result<Option<String>> {
+        match p.get(k) {
+            None | Some(Value::Null) => Ok(None),
+            Some(Value::String(n)) => Ok(Some(n.clone())),
+            Some(_) => Err(bad(cmd, format!("`{k}` must be a body name"))),
+        }
+    };
+    let (a, b) = match (given("a")?, given("b")?) {
+        (Some(a), Some(b)) => (a, b),
+        (None, None) => {
+            let selected: Vec<String> =
+                s.selection.iter().filter_map(|x| if let Sel::Body { name } = x { Some(name.clone()) } else { None }).collect();
+            let all: Vec<String> = st.bodies.iter().map(|b| b.name.clone()).collect();
+            match (selected.as_slice(), all.as_slice()) {
+                ([a, b], _) | (_, [a, b]) => (a.clone(), b.clone()),
+                _ => return Err(bad(cmd, "give `a` and `b` (or select two bodies)")),
+            }
+        }
+        _ => return Err(bad(cmd, "give both `a` and `b`")),
+    };
+    for n in [&a, &b] {
+        if st.body(n).is_none() {
+            return Err(bad(cmd, format!("no body `{n}`")));
+        }
+    }
+    if a == b {
+        return Err(bad(cmd, "`a` and `b` must be two different bodies"));
+    }
+    Ok((a, b))
+}
+
+fn colours(cmd: &str, p: &Value) -> Result<Option<[[u8; 3]; 2]>> {
+    match p.get("color") {
+        None | Some(Value::Null) | Some(Value::Bool(false)) => Ok(None),
+        Some(Value::Bool(true)) => Ok(Some([ONLY_IN_A, ONLY_IN_B])),
+        Some(Value::Object(o)) => {
+            let pick = |k: &str, d: [u8; 3]| match o.get(k) {
+                None | Some(Value::Null) => Ok(d),
+                Some(v) => {
+                    super::inspect::color_param(v).ok_or_else(|| bad(cmd, format!("`color.{k}` must be \"#rrggbb\" or [r, g, b] with values 0–255")))
+                }
+            };
+            Ok(Some([pick("only_in_a", ONLY_IN_A)?, pick("only_in_b", ONLY_IN_B)?]))
+        }
+        Some(_) => Err(bad(cmd, "`color` must be true or {only_in_a, only_in_b}")),
+    }
+}
+
+fn v3(v: &Value) -> Option<Vec3> {
+    crate::params::vec3(v)
+}
+
+/// b − a of the two bodies' measures.
+fn difference(ma: &Value, mb: &Value) -> Value {
+    let f = |m: &Value, k: &str| m.get(k).and_then(Value::as_f64);
+    let sub = |x: Option<f64>, y: Option<f64>| x.zip(y).map(|(x, y)| y - x);
+    let (va, vb) = (f(ma, "volume_mm3"), f(mb, "volume_mm3"));
+    let com = v3(&ma["center_of_mass"]).zip(v3(&mb["center_of_mass"])).map(|(a, b)| b - a);
+    let corner = |k: &str| v3(&ma["bbox"][k]).zip(v3(&mb["bbox"][k])).map(|(a, b)| b - a);
+    json!({
+        "volume_mm3": sub(va, vb),
+        "volume_percent": va.zip(vb).filter(|(a, _)| a.abs() > 0.0).map(|(a, b)| 100.0 * (b - a) / a),
+        "area_mm2": sub(f(ma, "area_mm2"), f(mb, "area_mm2")),
+        "center_of_mass": com,
+        "center_of_mass_distance_mm": com.map(Vec3::len),
+        "bbox_min": corner("min"),
+        "bbox_max": corner("max"),
+    })
+}
+
+/// The volume a closed mesh encloses (divergence theorem, about its box's centre).
+fn enclosed_volume(m: &solidcraft_geom::Mesh) -> f64 {
+    let o = m.bounds().center();
+    m.triangles.iter().filter_map(|t| m.tri(t)).map(|[a, b, c]| (a - o).dot((b - o).cross(c - o)) / 6.0).sum()
+}
+
+/// What makes the comparison less certain: a body whose surface does not enclose what it
+/// measures (open, or faces that failed), lines left out of region volumes.
+fn warnings(bodies: [(&str, &Value, &solidcraft_geom::Mesh); 2], chord: f64, c: &compare::Comparison) -> Vec<String> {
+    let mut out = Vec::new();
+    for (name, measure, mesh) in bodies {
+        let (Some(v), area) = (measure["volume_mm3"].as_f64(), measure["area_mm2"].as_f64().unwrap_or(0.0)) else { continue };
+        let enclosed = enclosed_volume(mesh);
+        // A mesh within `chord` of the surface encloses the volume to within chord × area.
+        if !((enclosed - v).abs() <= chord * area.abs() + 1e-6 * v.abs()) {
+            out.push(format!(
+                "`{name}`: its surface encloses {enclosed:.3} mm³ but the body measures {v:.3} mm³: it is open or has faces that failed, so its measures and the regions near the gap are unreliable"
+            ));
+        }
+    }
+    let skipped: usize = c.regions.iter().map(|r| r.lines.skipped).sum();
+    if skipped > 0 {
+        out.push(format!("{skipped} line(s) through the regions crossed a gap in a surface and were left out of their volumes"));
+    }
+    out
+}
+
+fn deviation_json(d: &compare::Deviation) -> Value {
+    json!({"max_mm": d.max, "mean_mm": d.mean, "at": d.at, "area_beyond_mm2": d.beyond_area, "area_mm2": d.area, "points": d.points})
+}
+
+fn compare_bodies(s: &mut Session, p: &Value) -> Result<Value> {
+    let cmd = "inspect.compare";
+    let tolerance = number(cmd, p, "tolerance", 0.01, 0.001..=10.0)?;
+    let spacing = number(cmd, p, "spacing", 0.5, 0.01..=1000.0)?;
+    let max_points = number(cmd, p, "max_points", 8e6, 1e4..=5e7)? as usize;
+    let max_regions = number(cmd, p, "max_regions", 50.0, 1.0..=1000.0)? as usize;
+    let colors = colours(cmd, p)?;
+    let st = s.world_state();
+    let (na, nb) = pair(s, &st, p, cmd)?;
+    let (Some(ba), Some(bb)) = (st.body(&na), st.body(&nb)) else { return Err(bad(cmd, "no such body")) };
+    // Meshed within a quarter of the tolerance (the kernel goes no finer than a millionth of a
+    // body's size), so two meshes of one surface agree well within it.
+    let chord = tolerance / 4.0;
+    let mut done = solidcraft_kernel::map_on_threads(&[ba, bb], 2, |b| (super::inspect::measure_json(b), b.body.tessellate_with(chord, true)))
+        .into_iter()
+        .zip([&na, &nb]);
+    let mut next = || -> Result<(Value, solidcraft_geom::Mesh)> {
+        let Some((r, name)) = done.next() else { return Err(bad(cmd, "no such body")) };
+        let (m, mesh) = r.ok_or_else(|| bad(cmd, format!("`{name}`: measuring it failed")))?;
+        let mesh = mesh.map_err(|e| bad(cmd, format!("`{name}`: {e}")))?;
+        if mesh.triangles.is_empty() {
+            return Err(bad(cmd, format!("`{name}` has no surface")));
+        }
+        Ok((m, mesh))
+    };
+    let ((measure_a, mesh_a), (measure_b, mesh_b)) = (next()?, next()?);
+    let options = CompareOptions { tolerance, spacing, max_points, max_regions, ..CompareOptions::default() };
+    let each = |n: usize, job: &(dyn Fn(usize) + Sync)| {
+        let jobs: Vec<usize> = (0..n).collect();
+        solidcraft_kernel::for_each_on_threads(&jobs, 16, |i| job(*i));
+    };
+    let c = compare::compare(&mesh_a, &mesh_b, &options, &each);
+    let axis = |k: usize| ["X", "Y", "Z"].get(k).copied().unwrap_or("?");
+    let regions: Vec<Value> = c
+        .regions
+        .iter()
+        .enumerate()
+        .map(|(i, r)| {
+            json!({
+                "index": i + 1,
+                "side": side_name(r.side),
+                "material_of": if r.side == Side::OnlyInA { &na } else { &nb },
+                "volume_mm3": r.volume,
+                "area_mm2": r.area_a + r.area_b,
+                "area_a_mm2": r.area_a,
+                "area_b_mm2": r.area_b,
+                "max_deviation_mm": r.max_deviation,
+                "at": r.at,
+                "center": r.center,
+                "bbox": {"min": r.bbox.min, "max": r.bbox.max},
+                "faces_a": r.faces_a.iter().map(|x| x.0).collect::<Vec<u32>>(),
+                "faces_b": r.faces_b.iter().map(|x| x.0).collect::<Vec<u32>>(),
+                "resolution": {"along": axis(r.lines.axis), "line_spacing_mm": r.lines.spacing, "lines": r.lines.count, "skipped_lines": r.lines.skipped},
+            })
+        })
+        .collect();
+    let total = |side: Side| {
+        let rs: Vec<&compare::Region> = c.regions.iter().filter(|r| r.side == side).collect();
+        // `+ 0.0`: an empty sum is -0.0.
+        (rs.len(), rs.iter().map(|r| r.volume).filter(|v| v.is_finite()).sum::<f64>() + 0.0)
+    };
+    let ((ca, va), (cb, vb)) = (total(Side::OnlyInA), total(Side::OnlyInB));
+    let worst = c.a_to_b.max.max(c.b_to_a.max);
+    let identical = c.regions.is_empty() && c.unlisted == 0;
+    let warnings = warnings([(na.as_str(), &measure_a, &mesh_a), (nb.as_str(), &measure_b, &mesh_b)], chord, &c);
+    let mut verdict = if identical {
+        format!("identical within {tolerance} mm (largest deviation {worst:.4} mm)")
+    } else {
+        let more = if c.unlisted > 0 { format!(" (and {} more, not measured)", c.unlisted) } else { String::new() };
+        format!(
+            "{} {} by more than {tolerance} mm: {ca} with material only in `{na}` ({va:.3} mm³), {cb} only in `{nb}` ({vb:.3} mm³){more}",
+            c.regions.len(),
+            if c.regions.len() == 1 { "region differs" } else { "regions differ" }
+        )
+    };
+    if !warnings.is_empty() {
+        verdict += &format!(" ({} warning{})", warnings.len(), if warnings.len() == 1 { "" } else { "s" });
+    }
+    let mut out = json!({
+        "a": measure_a,
+        "b": measure_b,
+        "difference": difference(&measure_a, &measure_b),
+        "tolerance_mm": tolerance,
+        "deviation": {"a_to_b": deviation_json(&c.a_to_b), "b_to_a": deviation_json(&c.b_to_a), "max_mm": worst},
+        "identical": identical,
+        "verdict": verdict,
+        "regions": regions,
+        "only_in_a": {"regions": ca, "volume_mm3": va},
+        "only_in_b": {"regions": cb, "volume_mm3": vb},
+        "unlisted_regions": c.unlisted,
+        "warnings": warnings,
+        "sampling": {"spacing_mm": c.spacing, "chord_mm": chord, "triangles_a": mesh_a.triangles.len(), "triangles_b": mesh_b.triangles.len()},
+    });
+    if let Some(colors) = colors {
+        out["colored_faces"] = json!(color_regions(s, &c, [&na, &nb], colors)?);
+    }
+    Ok(out)
+}
+
+/// A face is coloured for a region when at least this share of it deviates there.
+const MOSTLY: f64 = 0.5;
+
+/// The faces to colour for a region, as (body: 0 = a, 1 = b; face): those mostly beyond the
+/// tolerance (a small difference on a large face would colour all of it), or, when it has none,
+/// the one with the largest share.
+fn faces_to_color(c: &compare::Comparison, r: &compare::Region) -> Vec<(usize, u32)> {
+    let share = |m: usize, &(f, beyond): &(u32, f64)| {
+        let all = c.face_area.get(m).and_then(|x| x.get(&f)).copied().unwrap_or(0.0);
+        (m, f, if all > 0.0 { beyond / all } else { 0.0 })
+    };
+    let all: Vec<(usize, u32, f64)> = r.faces_a.iter().map(|x| share(0, x)).chain(r.faces_b.iter().map(|x| share(1, x))).collect();
+    let mostly: Vec<(usize, u32)> = all.iter().filter(|x| x.2 >= MOSTLY).map(|x| (x.0, x.1)).collect();
+    if !mostly.is_empty() {
+        return mostly;
+    }
+    all.iter().max_by(|x, y| x.2.total_cmp(&y.2)).map(|x| vec![(x.0, x.1)]).unwrap_or_default()
+}
+
+/// Give the faces holding each region the colour of its side (a face holding several takes the
+/// largest one's); returns how many face appearances were set.
+fn color_regions(s: &mut Session, c: &compare::Comparison, names: [&String; 2], colors: [[u8; 3]; 2]) -> Result<usize> {
+    use solidcraft_doc::appearance::{FaceLook, Look};
+    let st = s.model.state();
+    // Where each face of the two bodies is, as the design file names and finds it. A body placed
+    // by an occurrence is coloured where it is defined, if at all.
+    let found: Vec<_> =
+        names.iter().map(|n| st.body(n).map(|b| (solidcraft_doc::naming::face_spots(b), solidcraft_doc::naming::face_names(b)))).collect();
+    let mut picks: Vec<(String, Vec3, Option<String>, Look)> = Vec::new();
+    // Smallest region first, so the largest one's colour is the one that stays.
+    for r in c.regions.iter().rev() {
+        let colour = if r.side == Side::OnlyInA { colors[0] } else { colors[1] };
+        let mut look = Look::custom(colour, 1.0);
+        look.name = if r.side == Side::OnlyInA { "Only in a".into() } else { "Only in b".into() };
+        for (m, f) in faces_to_color(c, r) {
+            let (Some(Some((spots, face_names))), Some(name)) = (found.get(m), names.get(m)) else { continue };
+            let Some(spot) = spots.get(f as usize).copied().flatten() else { continue };
+            picks.retain(|(b, pt, _, _)| !(b == *name && pt.dist(spot.point) < 1e-9));
+            picks.push(((*name).clone(), spot.point, face_names.get(f as usize).cloned(), look.clone()));
+        }
+    }
+    if picks.is_empty() {
+        return Ok(0);
+    }
+    let a = &mut s.doc_mut().appearances;
+    let mut n = 0;
+    for (body, point, name, look) in picks {
+        a.faces.retain(|f| !(f.body == body && f.point.dist(point) < 1e-9));
+        if a.faces.len() >= 100_000 {
+            return Err(bad("inspect.compare", "too many face appearances"));
+        }
+        a.faces.push(FaceLook { body, point, look, name, strict_name: false, certificate: None });
+        n += 1;
+    }
+    Ok(n)
+}
+
+#[cfg(test)]
+#[path = "compare_tests.rs"]
+mod tests;

crates/engine/src/cmd/compare_tests.rs

@@ -0,0 +1,212 @@
+use serde_json::{Value, json};
+
+use crate::Session;
+
+fn run(s: &mut Session, id: &str, p: Value) -> Value {
+    match s.execute(id, &p) {
+        Ok(v) => v,
+        Err(e) => panic!("{id} {p}: {e}"),
+    }
+}
+
+fn regions(r: &Value) -> Vec<Value> {
+    r["regions"].as_array().cloned().unwrap_or_default()
+}
+
+fn f(v: &Value) -> f64 {
+    v.as_f64().unwrap_or(f64::NAN)
+}
+
+fn close(got: f64, want: f64, rel: f64) -> bool {
+    (got - want).abs() <= rel * want.abs()
+}
+
+/// A 40 x 30 x 10 box `A` and its copy `A (2)`, in the same place.
+fn two_boxes() -> Session {
+    let mut s = Session::default();
+    run(&mut s, "solid.box", json!({"length": 40, "width": 30, "height": 10, "body_name": "A"}));
+    run(&mut s, "solid.move", json!({"bodies": ["A"], "translate": [0, 0, 0], "copy": true}));
+    s
+}
+
+#[test]
+fn a_box_and_its_copy_are_identical() {
+    let mut s = two_boxes();
+    let r = run(&mut s, "inspect.compare", json!({"a": "A", "b": "A (2)"}));
+    assert_eq!(r["identical"], true, "{r}");
+    assert_eq!(r["warnings"], json!([]), "{r}");
+    assert!(regions(&r).is_empty());
+    assert!(f(&r["deviation"]["max_mm"]) < 1e-9, "{}", r["deviation"]);
+    assert_eq!(f(&r["difference"]["volume_mm3"]), 0.0);
+    assert!(close(f(&r["a"]["volume_mm3"]), 12_000.0, 1e-9));
+    assert!(r["verdict"].as_str().unwrap_or_default().starts_with("identical within 0.01 mm"), "{}", r["verdict"]);
+    // Without names: the design's only two bodies. Comparing changes nothing.
+    let before = s.doc.clone();
+    let r = run(&mut s, "inspect.compare", json!({}));
+    assert_eq!(r["identical"], true);
+    assert!(std::sync::Arc::ptr_eq(&before, &s.doc));
+}
+
+#[test]
+fn a_pocket_is_material_only_the_plain_box_has() {
+    // b has a 10 x 8 x 0.5 pocket in its top: 40 mm³ that only a has.
+    let mut s = two_boxes();
+    run(&mut s, "solid.box", json!({"length": 10, "width": 8, "height": 0.5, "corner": [10, 10, 9.5], "operation": "cut", "targets": ["A (2)"]}));
+    let r = run(&mut s, "inspect.compare", json!({"a": "A", "b": "A (2)"}));
+    let rs = regions(&r);
+    assert_eq!(rs.len(), 1, "{r}");
+    let g = &rs[0];
+    assert_eq!(g["side"], "only_in_a");
+    assert_eq!(g["material_of"], "A");
+    assert!(close(f(&g["volume_mm3"]), 40.0, 0.01), "{g}");
+    assert!((f(&g["max_deviation_mm"]) - 0.5).abs() < 1e-6, "{g}");
+    let (lo, hi) = (&g["bbox"]["min"], &g["bbox"]["max"]);
+    for (k, (want_lo, want_hi)) in [(10.0, 20.0), (10.0, 18.0), (9.5, 10.0)].into_iter().enumerate() {
+        assert!((f(&lo[k]) - want_lo).abs() < 0.05 && (f(&hi[k]) - want_hi).abs() < 0.05, "{g}");
+    }
+    let c = &g["center"];
+    assert!((f(&c[0]) - 15.0).abs() < 0.02 && (f(&c[1]) - 14.0).abs() < 0.02 && (f(&c[2]) - 9.75).abs() < 1e-6, "{g}");
+    // The pocket's floor and walls, and a's top.
+    assert_eq!(g["faces_b"].as_array().map(Vec::len), Some(5), "{g}");
+    assert_eq!(g["faces_a"].as_array().map(Vec::len), Some(1), "{g}");
+    assert!(close(f(&r["difference"]["volume_mm3"]), -40.0, 1e-6), "{}", r["difference"]);
+    assert!(close(f(&r["only_in_a"]["volume_mm3"]), 40.0, 0.01));
+    assert_eq!(r["only_in_b"]["regions"], 0);
+    // The other way round, the same material is only in b.
+    let r = run(&mut s, "inspect.compare", json!({"a": "A (2)", "b": "A"}));
+    assert_eq!(regions(&r).len(), 1);
+    assert_eq!(regions(&r)[0]["side"], "only_in_b");
+    assert_eq!(regions(&r)[0]["material_of"], "A");
+}
+
+#[test]
+fn a_boss_is_material_only_the_box_with_it_has() {
+    // b has a 6 x 5 x 2 boss on its top: 60 mm³ that only b has.
+    let mut s = two_boxes();
+    run(&mut s, "solid.box", json!({"length": 6, "width": 5, "height": 2, "corner": [5, 5, 10], "operation": "join", "targets": ["A (2)"]}));
+    let r = run(&mut s, "inspect.compare", json!({"a": "A", "b": "A (2)", "color": true}));
+    let rs = regions(&r);
+    assert_eq!(rs.len(), 1, "{r}");
+    assert_eq!(rs[0]["side"], "only_in_b");
+    assert!(close(f(&rs[0]["volume_mm3"]), 60.0, 0.01), "{}", rs[0]);
+    assert!((f(&rs[0]["max_deviation_mm"]) - 2.0).abs() < 1e-6);
+    assert!(close(f(&r["difference"]["volume_mm3"]), 60.0, 1e-6));
+    // Coloured green: the boss's top and four sides, all of them beyond the tolerance; not a's top,
+    // of which only the boss's footprint is. One undo step.
+    assert_eq!(r["colored_faces"], 5, "{r}");
+    let green = |s: &Session, body: &str| s.doc.appearances.faces.iter().filter(|x| x.body == body && x.look.color == [0x2f, 0x9e, 0x44]).count();
+    assert_eq!((green(&s, "A (2)"), green(&s, "A")), (5, 0));
+    run(&mut s, "edit.undo", json!({}));
+    assert_eq!(s.doc.appearances.faces.len(), 0);
+    // Own colours.
+    let r = run(&mut s, "inspect.compare", json!({"color": {"only_in_b": "#0000ff"}}));
+    assert_eq!(r["colored_faces"], 5);
+    assert_eq!(s.doc.appearances.faces.iter().filter(|x| x.look.color == [0, 0, 255]).count(), 5);
+}
+
+/// A 100 x 60 sheet-metal plate with a 20 mm flange along y = 0 and a 5 mm hole at (x, 40).
+fn bracket(s: &mut Session, name: &str, x: f64) {
+    run(s, "sketch.create", json!({"plane": "XY", "name": format!("{name} base")}));
+    run(s, "sketch.rectangle.two_point", json!({"p0": [0, 0], "p1": [100, 60]}));
+    run(s, "sketch.finish", json!({}));
+    run(s, "sheet.flange", json!({"sketch": format!("{name} base"), "body_name": name}));
+    run(s, "sheet.flange", json!({"edges": [[50, 0, 2.5]], "height": 20, "body": name}));
+    run(s, "sketch.create", json!({"plane": "XY", "name": format!("{name} hole")}));
+    run(s, "sketch.circle.center", json!({"center": [x, 40], "diameter": 5}));
+    run(s, "sketch.finish", json!({}));
+    run(s, "solid.extrude", json!({"sketch": format!("{name} hole"), "through_all": true, "operation": "cut", "targets": [name]}));
+}
+
+#[test]
+fn a_hole_moved_2_mm_leaves_two_crescents() {
+    let mut s = Session::default();
+    bracket(&mut s, "Before", 50.0);
+    bracket(&mut s, "After", 52.0);
+    let r = run(&mut s, "inspect.compare", json!({"a": "Before", "b": "After"}));
+    let rs = regions(&r);
+    assert_eq!(rs.len(), 2, "{r}");
+    // Each is a disk of 2.5 mm radius less its overlap with the other, centres 2 mm apart, through
+    // the 2.5 mm sheet: (π r² − 2 r² acos(d / 2r) + (d / 2) √(4 r² − d²)) · t.
+    let (rr, d, t) = (2.5f64, 2.0f64, 2.5);
+    let crescent = (std::f64::consts::PI * rr * rr - 2.0 * rr * rr * (d / (2.0 * rr)).acos() + d / 2.0 * (4.0 * rr * rr - d * d).sqrt()) * t;
+    assert!((crescent - 24.316_34).abs() < 1e-4);
+    for g in &rs {
+        assert!(close(f(&g["volume_mm3"]), crescent, 0.02), "{g}");
+        let c = &g["center"];
+        assert!((f(&c[1]) - 40.0).abs() < 0.05 && (f(&c[2]) - 1.25).abs() < 0.01, "{g}");
+        // Material only Before has is where After's hole is (beyond x = 51), and the reverse.
+        match g["side"].as_str() {
+            Some("only_in_a") => assert!(f(&c[0]) > 51.5, "{g}"),
+            Some("only_in_b") => assert!(f(&c[0]) < 50.5, "{g}"),
+            _ => panic!("{g}"),
+        }
+    }
+    assert_ne!(rs[0]["side"], rs[1]["side"]);
+    assert!(f(&r["difference"]["volume_mm3"]).abs() < 1e-3, "{}", r["difference"]);
+    // Coloured: the hole walls, not the plate's faces, of which only the crescents deviate.
+    let r = run(&mut s, "inspect.compare", json!({"a": "Before", "b": "After", "color": true}));
+    let n = r["colored_faces"].as_u64().unwrap_or(0) as usize;
+    assert!((2..=8).contains(&n), "{r}");
+    let looks = &s.doc.appearances.faces;
+    assert_eq!(looks.len(), n);
+    for l in looks {
+        assert!(((l.point.x - 51.0).powi(2) + (l.point.y - 40.0).powi(2)).sqrt() < 4.0, "{:?}", l.point);
+    }
+}
+
+#[test]
+fn a_part_and_its_step_round_trips_are_identical() {
+    // Curved faces too: a hole and a rounded edge.
+    let mut s = Session::default();
+    run(&mut s, "solid.box", json!({"length": 40, "width": 30, "height": 10, "body_name": "Part"}));
+    run(&mut s, "solid.cylinder", json!({"diameter": 8, "height": 10, "base": [20, 15, 0], "operation": "cut", "targets": ["Part"]}));
+    run(&mut s, "solid.fillet", json!({"edges": [[40, 15, 10]], "radius": 3}));
+    let dir = std::env::temp_dir().join(format!("solidcraft-compare-{}", std::process::id()));
+    std::fs::create_dir_all(&dir).unwrap();
+    let path = dir.join("part.step");
+    run(&mut s, "file.export", json!({"path": path, "bodies": ["Part"]}));
+    let mut inserted = Vec::new();
+    for _ in 0..2 {
+        let r = run(&mut s, "file.insert_step", json!({"path": path}));
+        inserted.push(r["created_bodies"][0].as_str().unwrap().to_string());
+    }
+    let _ = std::fs::remove_dir_all(&dir);
+    for (a, b) in [("Part", inserted[0].as_str()), (inserted[0].as_str(), inserted[1].as_str())] {
+        let r = run(&mut s, "inspect.compare", json!({"a": a, "b": b}));
+        assert_eq!(r["identical"], true, "{a} vs {b}: {r}");
+        assert!(f(&r["deviation"]["max_mm"]) < 0.005, "{a} vs {b}: {}", r["deviation"]);
+        assert!(f(&r["difference"]["volume_mm3"]).abs() < 0.05, "{a} vs {b}: {}", r["difference"]);
+    }
+}
+
+#[test]
+fn bad_parameters_are_refused() {
+    let mut s = two_boxes();
+    run(&mut s, "solid.box", json!({"length": 5, "width": 5, "height": 5, "body_name": "C"}));
+    for p in [
+        json!({}),
+        json!({"a": "A"}),
+        json!({"a": "A", "b": "A"}),
+        json!({"a": "A", "b": "nope"}),
+        json!({"a": "A", "b": 3}),
+        json!({"a": "A", "b": "C", "tolerance": 0}),
+        json!({"a": "A", "b": "C", "tolerance": -1}),
+        json!({"a": "A", "b": "C", "tolerance": "a lot"}),
+        json!({"a": "A", "b": "C", "tolerance": 1e300}),
+        json!({"a": "A", "b": "C", "spacing": 0}),
+        json!({"a": "A", "b": "C", "max_regions": 0}),
+        json!({"a": "A", "b": "C", "max_points": 10}),
+        json!({"a": "A", "b": "C", "color": "blue"}),
+        json!({"a": "A", "b": "C", "color": {"only_in_a": "#12345"}}),
+    ] {
+        assert!(s.execute("inspect.compare", &p).is_err(), "{p}");
+    }
+    // Two selected bodies are the pair.
+    s.selection = vec![crate::Sel::Body { name: "A".into() }, crate::Sel::Body { name: "C".into() }];
+    let r = run(&mut s, "inspect.compare", json!({}));
+    assert_eq!(r["a"]["name"], "A");
+    assert_eq!(r["b"]["name"], "C");
+    assert_eq!(r["only_in_a"]["regions"], 1, "{r}");
+    assert!(close(f(&r["only_in_a"]["volume_mm3"]), 12_000.0 - 125.0, 0.01), "{r}");
+    assert!(r["verdict"].as_str().unwrap_or_default().starts_with("1 region differs by more than 0.01 mm"), "{}", r["verdict"]);
+}