feat: preserve adaptive sketch profiles and curved modeling workflows

crates/engine/src/cmd/component_clone.rs

@@ -9,6 +9,64 @@ use solvecraft_doc::{Document, Feature, FeatureKind, Mat, Occurrence};
 const CMD: &str = "component.paste_new";
 const MAX_WORK: usize = 10_000;
 
+fn mesh_distance(mesh: &solvecraft_geom::Mesh, point: solvecraft_geom::Vec3) -> f64 {
+    mesh.triangles
+        .iter()
+        .filter_map(|triangle| mesh.tri(triangle))
+        .map(|[a, b, c]| {
+            let normal = (b - a).cross(c - a);
+            let squared = normal.dot(normal);
+            let projected = if squared > 0. { point - normal * ((point - a).dot(normal) / squared) } else { point };
+            if squared > 0. && [(a, b), (b, c), (c, a)].iter().all(|(start, end)| (*end - *start).cross(projected - *start).dot(normal) >= 0.) {
+                return point.dist(projected);
+            }
+            [(a, b), (b, c), (c, a)]
+                .iter()
+                .map(|(start, end)| {
+                    let edge = *end - *start;
+                    let t = if edge.dot(edge) > 0. { ((point - *start).dot(edge) / edge.dot(edge)).clamp(0., 1.) } else { 0. };
+                    point.dist(*start + edge * t)
+                })
+                .fold(f64::INFINITY, f64::min)
+        })
+        .fold(f64::INFINITY, f64::min)
+}
+
+fn material_probe_matches(a: &solvecraft_geom::Mesh, b: &solvecraft_geom::Mesh, point: solvecraft_geom::Vec3, tol_a: f64, tol_b: f64) -> bool {
+    if !point.is_finite() || !tol_a.is_finite() || !tol_b.is_finite() || tol_a <= 0. || tol_b <= 0. {
+        return false;
+    }
+    if a.contains(point) == b.contains(point) {
+        return true;
+    }
+    // A chord approximation does not define material ON a boundary. Certify
+    // nearby stock and void instead, outside both meshes' approximation strips.
+    if mesh_distance(a, point) > tol_a || mesh_distance(b, point) > tol_b {
+        return false;
+    }
+    let offset = 4. * tol_a.max(tol_b);
+    let mut material = false;
+    let mut void = false;
+    for axis in [solvecraft_geom::Vec3::X, solvecraft_geom::Vec3::Y, solvecraft_geom::Vec3::Z] {
+        for sign in [-1., 1.] {
+            let q = point + axis * (sign * offset);
+            if !q.is_finite() {
+                return false;
+            }
+            if mesh_distance(a, q) <= tol_a || mesh_distance(b, q) <= tol_b {
+                continue;
+            }
+            let inside = a.contains(q);
+            if inside != b.contains(q) {
+                return false;
+            }
+            material |= inside;
+            void |= !inside;
+        }
+    }
+    material && void
+}
+
 fn cloned_path(source: &Document, path: &[u64], root: u64, destination: &[u64], occurrences: &BTreeMap<u64, u64>) -> Result<Vec<u64>> {
     let start = path
         .iter()
@@ -586,9 +644,13 @@ pub(super) fn paste(
         let mb = solvecraft_kernel::measure(&b)?;
         let tolerance = 1e-5 * (1.0 + (ma.bbox.max - ma.bbox.min).len()) + 64.0 * f64::EPSILON * (ma.bbox.min.len() + ma.bbox.max.len());
         let mut material_matches = true;
-        let mesh_a = a.display_mesh((a.size() * 1e-3).max(1e-3))?;
-        let mesh_b = b.display_mesh((b.size() * 1e-3).max(1e-3))?;
-        proof_work = proof_work.saturating_add(mesh_a.triangles.len().saturating_add(mesh_b.triangles.len()).saturating_mul(27));
+        let tol_a = (a.size() * 1e-3).max(1e-3).max(a.size() * 1e-6);
+        let tol_b = (b.size() * 1e-3).max(1e-3).max(b.size() * 1e-6);
+        let mesh_a = a.display_mesh(tol_a)?;
+        let mesh_b = b.display_mesh(tol_b)?;
+        // Precharge all 27 candidates, six possible replacements, their triangle
+        // distances and the three containment rays before any proof traversal.
+        proof_work = proof_work.saturating_add(mesh_a.triangles.len().saturating_add(mesh_b.triangles.len()).saturating_mul(27 * 7 * 4));
         if proof_work > 50_000_000 {
             return Err(bad(CMD, "geometry verification exceeds copy work limit"));
         }
@@ -597,7 +659,8 @@ pub(super) fn paste(
                 for z in [0.2, 0.5, 0.8] {
                     let d = ma.bbox.max - ma.bbox.min;
                     let p = ma.bbox.min + solvecraft_geom::Vec3::new(d.x * x, d.y * y, d.z * z);
-                    material_matches &= mesh_a.contains(p) == mesh_b.contains(p);
+                    let roundoff = 64. * f64::EPSILON * (1. + p.len());
+                    material_matches &= material_probe_matches(&mesh_a, &mesh_b, p, tol_a + roundoff, tol_b + roundoff);
                 }
             }
         }

crates/engine/src/cmd/component_clone_tests.rs

@@ -465,3 +465,57 @@ fn transferred_frozen_face_paint_ignores_consumed_legacy_offset() {
     let paint = s.doc.appearances.faces.iter().find(|face| face.body == "Foreign (copy)").unwrap();
     assert!(paint.point.dist(expected) < 1e-6, "{:?} versus {expected:?}", paint.point);
 }
+
+#[test]
+fn boundary_material_proof_requires_resolvable_stock_and_void() {
+    use solvecraft_geom::Vec3;
+    let a = solvecraft_kernel::box_solid(Vec3::ZERO, Vec3::new(10., 10., 10.)).unwrap().tessellate(1e-3).unwrap();
+    let b = solvecraft_kernel::box_solid(Vec3::new(1e-5, 0., 0.), Vec3::new(10.00001, 10., 10.)).unwrap().tessellate(1e-3).unwrap();
+    let p = Vec3::new(5e-6, 5., 5.);
+    assert_ne!(a.contains(p), b.contains(p));
+    assert!((super::mesh_distance(&a, p) - 5e-6).abs() < 1e-12);
+    assert!((super::mesh_distance(&b, p) - 5e-6).abs() < 1e-12);
+    assert!(super::material_probe_matches(&a, &b, p, 1e-3, 1e-3));
+    let shifted = solvecraft_kernel::box_solid(Vec3::new(1., 0., 0.), Vec3::new(11., 10., 10.)).unwrap().tessellate(1e-3).unwrap();
+    assert!(!super::material_probe_matches(&a, &shifted, p, 1e-3, 1e-3));
+    let thin = solvecraft_kernel::box_solid(Vec3::ZERO, Vec3::new(10., 10., 1e-4)).unwrap().tessellate(1e-6).unwrap();
+    let thin_shifted = solvecraft_kernel::box_solid(Vec3::new(0., 0., 1e-4), Vec3::new(10., 10., 2e-4)).unwrap().tessellate(1e-6).unwrap();
+    // Every resolvable replacement is void: thin ambiguous material is refused.
+    assert!(!super::material_probe_matches(&thin, &thin_shifted, Vec3::new(5., 5., 5e-5), 1e-3, 1e-3));
+    assert!(!super::material_probe_matches(&a, &b, p, f64::INFINITY, 1e-3));
+}
+
+#[test]
+fn frozen_bore_boundary_copy_preserves_stock_void_and_reopen() {
+    use solvecraft_geom::Vec3;
+    let bore = |center: f64| {
+        let mut s = Session::default();
+        run(&mut s, "solid.box", json!({"length":30,"width":20,"height":10,"body_name":"Drilled"}));
+        run(&mut s, "solid.cylinder", json!({"base":[center,10,0],"radius":4,"height":10,"operation":"cut"}));
+        s
+    };
+    let mut s = bore(10.);
+    let source = s.model.state().body("Drilled").unwrap().body.tessellate(1e-3).unwrap();
+    // The exact R4 wall passes through x6; a chord may end either side of that
+    // cardinal angle, so its distance is bounded by the requested sag tolerance.
+    assert!(super::mesh_distance(&source, Vec3::new(6., 10., 5.)) <= 1e-3);
+    let shifted = bore(11.).model.state().body("Drilled").unwrap().body.tessellate(1e-3).unwrap();
+    let lost = solvecraft_kernel::box_solid(Vec3::ZERO, Vec3::new(30., 20., 10.)).unwrap().tessellate(1e-3).unwrap();
+    assert!(!super::material_probe_matches(&source, &shifted, Vec3::new(6.5, 10., 5.), 1e-3, 1e-3));
+    assert!(!super::material_probe_matches(&source, &lost, Vec3::new(10., 10., 5.), 1e-3, 1e-3));
+    let created = run(&mut s, "component.from_bodies", json!({"bodies":["Drilled"]}));
+    let part = created["components"][0]["component"].as_u64().unwrap();
+    let copied = copy(&mut s, part)["component"].as_u64().unwrap();
+    let check = |session: &Session| {
+        let state = session.model.state();
+        let body = state.bodies.iter().find(|body| session.doc.model_body_component(body) == copied).unwrap();
+        let mesh = body.body.tessellate(1e-3).unwrap();
+        for (point, stock) in
+            [(Vec3::new(5.5, 10., 5.), true), (Vec3::new(6.5, 10., 5.), false), (Vec3::new(10., 10., 5.), false), (Vec3::new(18., 10., 5.), true)]
+        {
+            assert_eq!(mesh.contains(point), stock, "{point:?}");
+        }
+    };
+    check(&s);
+    check(&Session::new(solvecraft_doc::Document::from_json(&s.doc.to_json()).unwrap()));
+}

crates/engine/src/cmd/face_tests.rs

@@ -100,22 +100,17 @@ fn generated_profiles_and_press_pull_convert_rotated_occurrence_picks_once() {
         check(&mut s, area * 30.0, hole, 30.0);
         run(&mut s, "solid.press_pull", json!({"face":[35,-10,15],"distance":5}));
         check(&mut s, area * 35.0, hole, 35.0);
-        let height = if hole {
-            // Curved coincident Cut is an existing kernel limit; it must be atomic.
-            let before = s.doc.to_json();
-            let error = s.execute("solid.press_pull", &json!({"face":[35,-15,15],"distance":-5})).unwrap_err();
-            let message = error.to_string();
-            assert!(message.contains("takes planar faces only"), "{error}");
-            assert!(message.contains("the target has 2 curved faces (cylinder)"), "{error}");
-            assert!(message.contains("the tool has 2 curved faces (cylinder)"), "{error}");
-            assert_eq!(s.doc.to_json(), before);
-            check(&mut s, area * 35.0, hole, 35.0);
-            35.0
-        } else {
-            run(&mut s, "solid.press_pull", json!({"face":[35,-15,15],"distance":-5}));
-            check(&mut s, area * 30.0, hole, 30.0);
-            30.0
-        };
+        let before_cut = s.doc.to_json();
+        run(&mut s, "solid.press_pull", json!({"face":[35,-15,15],"distance":-5}));
+        let height = 30.0;
+        check(&mut s, area * height, hole, height);
+        let after_cut = s.doc.to_json();
+        run(&mut s, "edit.undo", json!({}));
+        assert_eq!(s.doc.to_json(), before_cut);
+        check(&mut s, area * 35.0, hole, 35.0);
+        run(&mut s, "edit.redo", json!({}));
+        assert_eq!(s.doc.to_json(), after_cut);
+        check(&mut s, area * height, hole, height);
         let world = s.world_state();
         let occupied = Vec3::new(35.0, 21.0 - height, 15.0);
         let absent = Vec3::new(35.0, 19.0 - height, 15.0);

crates/engine/src/cmd/features.rs

@@ -124,17 +124,9 @@ fn extrude_base(s: &Session, p: &Value) -> Option<(Vec3, Vec3)> {
         ProfileSel::All => ps.first()?.region.interior_point(),
         ProfileSel::Indices { indices } => ps.get(*indices.first()?)?.region.interior_point(),
         ProfileSel::Points { points } => *points.first()?,
-        ProfileSel::Curves { loops } => {
-            let mut want: Vec<&String> = loops.first()?.iter().collect();
-            want.sort();
-            ps.iter()
-                .find(|x| {
-                    let mut have: Vec<&String> = x.outer_curves.iter().collect();
-                    have.sort();
-                    have == want
-                })?
-                .region
-                .interior_point()
+        selection @ (ProfileSel::Curves { .. } | ProfileSel::OffsetBoundaries { .. } | ProfileSel::WholeBoundaries { .. }) => {
+            let indices = solvecraft_doc::profile_selection_indices(ss, &selection).ok()?;
+            ps.get(*indices.first()?)?.region.interior_point()
         }
     };
     Some((ss.plane.to_world(q), ss.plane.normal()))
@@ -216,9 +208,14 @@ pub(super) fn feature_sketch(s: &Session, p: &Value, cmd: &str) -> Result<u64> {
 fn stable_profiles(s: &Session, kind: &mut FeatureKind) -> Result<()> {
     let st = s.model.state();
     'sels: for (sketch, sel) in kind.profile_sels_mut() {
-        let ProfileSel::Indices { indices } = sel else { continue };
         let Some(ss) = st.sketch(sketch) else { continue };
-        let mut loops = Vec::with_capacity(indices.len());
+        if !matches!(
+            sel,
+            ProfileSel::Indices { .. } | ProfileSel::Curves { .. } | ProfileSel::OffsetBoundaries { .. } | ProfileSel::WholeBoundaries { .. }
+        ) {
+            continue;
+        }
+        let indices = solvecraft_doc::profile_selection_indices(ss, sel)?;
         for i in indices.iter() {
             let pr = ss
                 .profiles
@@ -226,12 +223,39 @@ fn stable_profiles(s: &Session, kind: &mut FeatureKind) -> Result<()> {
                 .ok_or_else(|| EngineError::Other(format!("no profile {i} in sketch `{}` (it has {})", ss.name, ss.profiles.len())))?;
             // Two profiles with the same outer curves (one inside the other's holes cannot be):
             // keep the index then.
-            if pr.outer_curves.is_empty() || ss.profiles.iter().filter(|q| same_loop(&q.outer_curves, &pr.outer_curves)).count() != 1 {
+            if !matches!(sel, ProfileSel::WholeBoundaries { .. })
+                && (pr.outer_curves.is_empty() || ss.profiles.iter().filter(|q| same_loop(&q.outer_curves, &pr.outer_curves)).count() != 1)
+            {
                 continue 'sels;
             }
-            loops.push(pr.outer_curves.clone());
         }
-        *sel = ProfileSel::Curves { loops };
+        let captured = solvecraft_doc::capture_profile_selection(ss, &indices)?;
+        *sel = match captured {
+            ProfileSel::OffsetBoundaries { associations }
+                if associations.iter().any(|id| {
+                    s.doc
+                        .sketch(sketch)
+                        .is_ok_and(|raw| !raw.offsets.iter().filter_map(|offset| offset.topology.as_ref()).any(|topology| topology.id == *id))
+                }) =>
+            {
+                // Legacy upgrade descriptors belong to the solved copy. Persist the
+                // complete original role IDs instead of an unsaved association ID.
+                let loops = associations
+                    .iter()
+                    .map(|id| {
+                        ss.sketch
+                            .offsets
+                            .iter()
+                            .filter_map(|offset| offset.topology.as_ref())
+                            .find(|topology| topology.id == *id)
+                            .map(|topology| topology.roles.iter().map(|role| role.output.clone()).collect())
+                            .ok_or_else(|| EngineError::Other(format!("offset association `{id}` changed during profile capture")))
+                    })
+                    .collect::<Result<Vec<_>>>()?;
+                ProfileSel::Curves { loops }
+            }
+            captured => captured,
+        };
     }
     Ok(())
 }
@@ -246,6 +270,32 @@ fn same_loop(a: &[String], b: &[String]) -> bool {
 pub(super) fn profiles(p: &Value, cmd: &str) -> Result<ProfileSel> {
     let Some(v) = p.get("profiles") else { return Ok(ProfileSel::All) };
     match v {
+        Value::Object(fields) => {
+            if fields.get("type").and_then(Value::as_str) == Some("whole_boundaries") {
+                return solvecraft_doc::whole_profile_selection_from_value(v).map_err(|error| bad(cmd, error.to_string()));
+            }
+            let associations = fields
+                .get("offset_boundaries")
+                .or_else(|| (fields.get("type").and_then(Value::as_str) == Some("offset_boundaries")).then(|| fields.get("associations")).flatten())
+                .and_then(Value::as_array)
+                .ok_or_else(|| bad(cmd, "profile object must provide `offset_boundaries: [association ids]`"))?;
+            if associations.is_empty() || associations.len() > 128 {
+                return Err(bad(cmd, "offset profile selection needs 1 to 128 association ids"));
+            }
+            let associations = associations
+                .iter()
+                .map(|id| {
+                    id.as_str()
+                        .filter(|id| !id.is_empty() && id.len() <= 512)
+                        .map(str::to_string)
+                        .ok_or_else(|| bad(cmd, "offset association ids must be nonempty strings of at most 512 bytes"))
+                })
+                .collect::<Result<Vec<_>>>()?;
+            if associations.iter().collect::<std::collections::BTreeSet<_>>().len() != associations.len() {
+                return Err(bad(cmd, "offset association ids must be unique"));
+            }
+            Ok(ProfileSel::OffsetBoundaries { associations })
+        }
         Value::String(s) if s.eq_ignore_ascii_case("all") => Ok(ProfileSel::All),
         Value::Number(n) => Ok(ProfileSel::Indices { indices: vec![n.as_u64().ok_or_else(|| bad(cmd, "profile index"))? as usize] }),
         Value::Array(a) if a.is_empty() => Err(bad(cmd, "`profiles` is empty")),
@@ -1351,3 +1401,15 @@ mod patterns_tests;
 #[cfg(test)]
 #[path = "revolve_convention_tests.rs"]
 mod revolve_convention_tests;
+
+#[cfg(test)]
+#[path = "offset_topology_tests.rs"]
+mod offset_topology_tests;
+
+#[cfg(test)]
+#[path = "offset_identity_tests.rs"]
+mod offset_identity_tests;
+
+#[cfg(test)]
+#[path = "offset_edit_guard_tests.rs"]
+mod offset_edit_guard_tests;

crates/engine/src/cmd/offset_edit_guard_tests.rs

@@ -0,0 +1,183 @@
+#![allow(clippy::unwrap_used, clippy::panic)]
+use serde_json::{Value, json};
+use solvecraft_doc::{Document, FeatureKind, ProfileSel};
+use solvecraft_geom::Vec2;
+use solvecraft_sketch::{CurveKind, Sketch};
+
+use crate::{Session, Snapshot};
+
+fn run(s: &mut Session, command: &str, params: Value) -> Value {
+    s.execute(command, &params).unwrap_or_else(|error| panic!("{command}: {error}"))
+}
+fn rounded() -> (Session, u64, String) {
+    let mut s = Session::default();
+    run(&mut s, "sketch.create", json!({"plane":"XY","name":"Rounded"}));
+    let sketch = s.active_sketch.unwrap();
+    run(&mut s, "sketch.rectangle.two_point", json!({"p0":[-38,-33],"p1":[38,33]}));
+    let fillet = run(&mut s, "sketch.fillet", json!({"points":["l1.start","l1.end","l2.end","l3.end"],"radius":"1 mm"}));
+    (s, sketch, fillet["param"].as_str().unwrap().into())
+}
+fn offset(s: &mut Session, curve: &str, distance: f64) -> (String, Vec<String>) {
+    let result = run(s, "sketch.offset", json!({"curves":[curve],"distance":distance,"side":[0,0]}));
+    (result["association"].as_str().unwrap().into(), result["curves"].as_array().unwrap().iter().map(|v| v.as_str().unwrap().into()).collect())
+}
+fn solved(s: &Session, id: u64) -> Sketch {
+    s.model.state().sketch(id).unwrap().sketch.clone()
+}
+fn arc_centres(sk: &Sketch, curves: &[String]) -> Vec<(String, usize, Vec2)> {
+    curves
+        .iter()
+        .filter_map(|id| {
+            let CurveKind::Arc { c, .. } = sk.curves.get(sk.curve_index(id)?)?.kind else { return None };
+            Some((id.clone(), c, sk.point(c)?))
+        })
+        .collect()
+}
+fn history(stack: &[Snapshot]) -> Vec<(String, String, Option<u64>, String)> {
+    stack.iter().map(|entry| (entry.label.clone(), entry.doc.to_json(), entry.active_sketch, format!("{:?}", entry.pending_moves))).collect()
+}
+fn refuses_atomically(s: &mut Session, command: &str, params: Value) -> String {
+    let document = s.doc.to_json();
+    let undo = history(&s.undo);
+    let redo = history(&s.redo);
+    let active = s.active_sketch;
+    let error = s.execute(command, &params).unwrap_err().to_string();
+    assert_eq!(s.doc.to_json(), document);
+    assert_eq!(history(&s.undo), undo);
+    assert_eq!(history(&s.redo), redo);
+    assert_eq!(s.active_sketch, active);
+    error
+}
+
+#[test]
+fn offset_guard_retired_parent_refuses_new_child_without_destroying_redo() {
+    let (mut s, sketch, _) = rounded();
+    let (_, outputs) = offset(&mut s, "l1", 1.4);
+    assert_eq!(outputs.len(), 4);
+    assert_eq!(solved(&s, sketch).offsets[0].topology.as_ref().unwrap().roles.iter().filter(|r| r.retired).count(), 4);
+    run(&mut s, "sketch.point", json!({"point":[100,100]}));
+    run(&mut s, "edit.undo", json!({}));
+    assert!(!s.redo.is_empty());
+    let error = refuses_atomically(&mut s, "sketch.offset", json!({"curves":[outputs[0]],"distance":0.2,"side":[0,0]}));
+    assert!(error.contains("retired corner") && error.contains("break its offset association"), "{error}");
+}
+
+#[test]
+fn offset_guard_live_child_follows_radius_then_retirement_is_honest() {
+    let (mut s, sketch, radius) = rounded();
+    let (_, parent) = offset(&mut s, "l1", 0.2);
+    let (child_association, child) = offset(&mut s, &parent[0], 0.2);
+    let arc_radius = |s: &Session| {
+        let sk = solved(s, sketch);
+        child
+            .iter()
+            .filter_map(|id| {
+                let CurveKind::Arc { c, a, .. } = sk.curves.get(sk.curve_index(id)?)?.kind else { return None };
+                Some(sk.point(c)?.dist(sk.point(a)?))
+            })
+            .collect::<Vec<_>>()
+    };
+    assert_eq!(arc_radius(&s).len(), 4);
+    assert!(arc_radius(&s).iter().all(|r| (*r - 0.6).abs() < 1e-6));
+    run(&mut s, "parameters.change", json!({"name":radius,"expression":"2 mm"}));
+    assert!(s.model.results.iter().all(|r| r.error.is_none()));
+    assert!(arc_radius(&s).iter().all(|r| (*r - 1.6).abs() < 1e-6));
+    run(&mut s, "sketch.finish", json!({}));
+    run(
+        &mut s,
+        "solid.extrude",
+        json!({"sketch":sketch,"profiles":{"offset_boundaries":[child_association]},"distance":2,"operation":"new","body_name":"Child"}),
+    );
+    let before = s.doc.to_json();
+    let undo = history(&s.undo);
+    let redo = history(&s.redo);
+    match s.execute("parameters.change", &json!({"name":radius,"expression":"0.1 mm"})) {
+        Err(error) => {
+            assert!(error.to_string().contains("offset"), "{error}");
+            assert_eq!(s.doc.to_json(), before);
+            assert_eq!(history(&s.undo), undo);
+            assert_eq!(history(&s.redo), redo);
+        }
+        Ok(_) => {
+            assert!(s.model.results.iter().any(|r| r.error.is_some()), "retired parent must not keep a stale successful child");
+            assert!(s.world_state().body("Child").is_none());
+            let reopened = Session::new(Document::from_json(&s.doc.to_json()).unwrap());
+            assert!(reopened.model.results.iter().any(|r| r.error.is_some()));
+            assert!(reopened.world_state().body("Child").is_none());
+        }
+    }
+}
+
+#[test]
+fn offset_guard_partial_delete_requires_break_and_surviving_arc_centres_detach() {
+    let (mut s, sketch, _) = rounded();
+    let (association, outputs) = offset(&mut s, "l1", 0.2);
+    let error = refuses_atomically(&mut s, "sketch.delete", json!({"entities":[outputs[0]]}));
+    assert!(error.contains("break the offset association"), "{error}");
+    let source = solved(&s, sketch);
+    let source_ids: Vec<_> = source.curves.iter().filter(|c| !outputs.contains(&c.id)).map(|c| c.id.clone()).collect();
+    let source_centres = arc_centres(&source, &source_ids);
+    assert_eq!(source_centres.len(), 4);
+    run(&mut s, "sketch.offset.break", json!({"curve":association}));
+    let released = solved(&s, sketch);
+    let independent = arc_centres(&released, &outputs);
+    assert_eq!(independent.len(), 4);
+    assert!(independent.iter().all(|(_, centre, _)| source_centres.iter().all(|(_, source, _)| centre != source)));
+    // Released geometry is editable: anchor its new centres independently, then
+    // move a source centre. Shared source nodes would block that actual move.
+    let released_centres: Vec<_> = independent.iter().map(|(id, _, _)| format!("{id}.center")).collect();
+    run(&mut s, "sketch.constraint.fix", json!({"entities":released_centres,"fixed":true}));
+    run(&mut s, "sketch.delete", json!({"entities":[outputs[0]]}));
+    let deleted = solved(&s, sketch);
+    assert!(deleted.curve_index(&outputs[0]).is_none());
+    let survivors = arc_centres(&deleted, &outputs);
+    let (source_id, _, position) = source_centres.first().unwrap();
+    let target = *position + Vec2::new(5.0, 5.0);
+    run(&mut s, "sketch.move_point", json!({"point":format!("{source_id}.center"),"to":[target.x,target.y]}));
+    assert!(s.model.results.iter().all(|r| r.error.is_none()));
+    let changed = solved(&s, sketch);
+    for (id, _, position) in independent {
+        let after = arc_centres(&changed, std::slice::from_ref(&id));
+        assert_eq!(after.len(), 1);
+        assert!(
+            after[0].2.dist(position) < 1e-8,
+            "{id}: released {position:?}, after deletion {:?}, after source move {:?}; deleted curve {}",
+            survivors.iter().find(|(curve, _, _)| curve == &id),
+            after[0],
+            outputs[0]
+        );
+    }
+    let moved = arc_centres(&changed, std::slice::from_ref(source_id));
+    assert_eq!(moved.len(), 1);
+    assert!(moved[0].2.dist(target) < 1e-8);
+    assert!(moved[0].2.dist(*position) > 5.0);
+}
+
+#[test]
+fn offset_guard_complete_delete_keeps_dangling_profile_loadable_without_circle_retarget() {
+    let (mut s, sketch, _) = rounded();
+    let (association, outputs) = offset(&mut s, "l1", 0.2);
+    run(&mut s, "sketch.circle.center", json!({"center":[100,0],"radius":3,"id":"Unrelated"}));
+    run(&mut s, "sketch.finish", json!({}));
+    run(
+        &mut s,
+        "solid.extrude",
+        json!({"sketch":sketch,"profiles":{"offset_boundaries":[association]},"distance":2,"operation":"new","name":"OffsetBody","body_name":"Selected"}),
+    );
+    run(&mut s, "sketch.edit", json!({"sketch":sketch}));
+    run(&mut s, "sketch.delete", json!({"entities":outputs}));
+    let saved = s.doc.to_json();
+    let FeatureKind::Extrude { profiles: ProfileSel::OffsetBoundaries { associations }, .. } = &s.doc.find_feature("OffsetBody").unwrap().kind else {
+        panic!("explicit offset identity lost")
+    };
+    assert_eq!(associations, &vec![association]);
+    let check = |s: &Session| {
+        assert!(solved(s, sketch).curve_index("Unrelated").is_some());
+        assert!(s.model.results.iter().find(|r| r.id == s.doc.find_feature("OffsetBody").unwrap().id).unwrap().error.is_some());
+        assert!(s.world_state().body("Selected").is_none(), "dangling selection must never adopt the unrelated circle");
+    };
+    check(&s);
+    let reopened = Session::new(Document::from_json(&saved).unwrap());
+    check(&reopened);
+    assert_eq!(reopened.doc.to_json(), saved);
+}

crates/engine/src/cmd/offset_identity_tests.rs

@@ -0,0 +1,136 @@
+#![allow(clippy::unwrap_used, clippy::panic)]
+use serde_json::{Value, json};
+use solvecraft_doc::{Document, FeatureKind, ProfileSel};
+
+use crate::Session;
+
+fn run(session: &mut Session, command: &str, params: Value) -> Value {
+    session.execute(command, &params).unwrap_or_else(|error| panic!("{command}: {error}"))
+}
+
+fn rounded_offset(radius: f64) -> (Session, u64, String, String) {
+    let mut session = Session::default();
+    run(&mut session, "sketch.create", json!({"plane":"XY","name":"Rounded"}));
+    let sketch = session.active_sketch.unwrap();
+    run(&mut session, "sketch.rectangle.two_point", json!({"p0":[-37.-radius,-32.-radius],"p1":[37.+radius,32.+radius]}));
+    let fillet = run(&mut session, "sketch.fillet", json!({"points":["l1.start","l1.end","l2.end","l3.end"],"radius":radius}));
+    // The radius is the only intended source freedom: keep the four exact arc
+    // centres at (+/-37,+/-32), independently of the corner radius.
+    let centers = fillet["curves"].as_array().unwrap().iter().map(|id| format!("{}.center", id.as_str().unwrap())).collect::<Vec<_>>();
+    run(&mut session, "sketch.constraint.fix", json!({"entities":centers,"fixed":true}));
+    let offset = run(&mut session, "sketch.offset", json!({"curves":["l1"],"distance":1.4,"side":[0,0]}));
+    run(&mut session, "sketch.finish", json!({}));
+    (session, sketch, fillet["param"].as_str().unwrap().into(), offset["association"].as_str().unwrap().into())
+}
+
+fn volume(session: &Session, feature: u64) -> f64 {
+    let state = session.model.state();
+    let body = state.bodies.iter().find(|body| body.feature == feature).unwrap();
+    solvecraft_kernel::measure(&body.body).unwrap().volume
+}
+
+fn healthy(session: &Session) {
+    assert!(session.model.results.iter().all(|result| result.error.is_none()), "{:?}", session.model.results);
+}
+
+#[test]
+fn legacy_offset_capture_persists_reserved_curves_without_a_transient_association() {
+    let (session, sketch, radius, _) = rounded_offset(2.);
+    let mut document = (*session.doc).clone();
+    let raw = document.sketch_mut(sketch).unwrap();
+    let reserved = raw.offsets[0].outputs.clone();
+    assert_eq!(reserved.len(), 8);
+    raw.offsets[0].topology = None;
+    document.format = "solvecraft/11".into();
+    let mut session = Session::new(Document::from_json(&document.to_json()).unwrap());
+    assert!(session.doc.sketch(sketch).unwrap().offsets[0].topology.is_none());
+    let state = session.model.state();
+    let solved = state.sketch(sketch).unwrap();
+    assert!(solved.sketch.offsets[0].topology.is_some(), "legacy upgrade belongs only to the evaluated copy");
+    let index = solvecraft_doc::profile_selection_indices(solved, &ProfileSel::Curves { loops: vec![reserved.clone()] }).unwrap()[0];
+    let extrusion = run(&mut session, "solid.extrude", json!({"sketch":sketch,"profiles":[index],"distance":2,"name":"Legacy inner"}))["feature"]
+        .as_u64()
+        .unwrap();
+    assert!(
+        matches!(&session.doc.feature(extrusion).unwrap().kind,FeatureKind::Extrude {profiles:ProfileSel::Curves {loops},..} if loops == &vec![reserved.clone()])
+    );
+    assert!(session.doc.sketch(sketch).unwrap().offsets[0].topology.is_none());
+    run(&mut session, "parameters.change", json!({"name":radius,"expression":"1 mm"}));
+    healthy(&session);
+    assert_eq!(session.model.state().sketch(sketch).unwrap().sketch.offsets[0].outputs.len(), 4);
+    assert!(
+        (volume(&session, extrusion) - 73.2 * 63.2 * 2.).abs() < 1e-6,
+        "legacy sharp volume {} bounds {:?}",
+        volume(&session, extrusion),
+        session.model.state().bodies.last().unwrap().mesh().bounds()
+    );
+    let saved = session.doc.to_json();
+    let mut reopened = Session::new(Document::from_json(&saved).unwrap());
+    healthy(&reopened);
+    assert_eq!(reopened.doc.to_json(), saved);
+    assert!(reopened.doc.sketch(sketch).unwrap().offsets[0].topology.is_none());
+    assert!((volume(&reopened, extrusion) - 73.2 * 63.2 * 2.).abs() < 1e-6);
+    run(&mut reopened, "parameters.change", json!({"name":radius,"expression":"2 mm"}));
+    healthy(&reopened);
+    let state = reopened.model.state();
+    assert_eq!(state.sketch(sketch).unwrap().sketch.offsets[0].outputs, reserved);
+    let expected = 2. * (75.2 * 65.2 - (4. - std::f64::consts::PI) * 0.6 * 0.6);
+    assert!((volume(&reopened, extrusion) - expected).abs() < 0.002);
+}
+
+#[test]
+fn pasted_offset_boundary_has_scoped_identity_and_independent_dimensions_and_material() {
+    let (mut session, sketch, radius, association) = rounded_offset(1.);
+    let extrusion = run(
+        &mut session,
+        "solid.extrude",
+        json!({"sketch":sketch,"profiles":{"offset_boundaries":[association]},"distance":2,"name":"Inner"}),
+    )["feature"]
+        .as_u64()
+        .unwrap();
+    let source_body = session.model.state().bodies[0].name.clone();
+    run(&mut session, "material.assign", json!({"bodies":[source_body],"material":"Brass"}));
+    run(&mut session, "timeline.copy", json!({"features":[sketch,extrusion]}));
+    let pasted = run(&mut session, "timeline.paste", json!({"translate":[100,0,0]}));
+    assert_eq!(pasted["errors"], json!([]));
+    let copied_sketch = pasted["pasted"][0]["id"].as_u64().unwrap();
+    let copied_extrusion = pasted["pasted"][1]["id"].as_u64().unwrap();
+    assert_ne!(copied_sketch, sketch);
+    assert!(
+        matches!(&session.doc.feature(copied_extrusion).unwrap().kind,FeatureKind::Extrude {sketch:source,profiles:ProfileSel::OffsetBoundaries {associations},..} if *source==copied_sketch && associations == &vec![association.clone()])
+    );
+    let source = session.doc.sketch(sketch).unwrap();
+    let copy = session.doc.sketch(copied_sketch).unwrap();
+    assert_eq!(source.offsets[0].topology.as_ref().unwrap().id, copy.offsets[0].topology.as_ref().unwrap().id);
+    let dimension = source.constraints.iter().position(|constraint| constraint.param.as_deref() == Some(&radius)).unwrap();
+    let copied_radius = copy.constraints[dimension].param.clone().unwrap();
+    assert_ne!(copied_radius, radius);
+    let copied_body = session.model.state().bodies.iter().find(|body| body.feature == copied_extrusion).unwrap().name.clone();
+    run(&mut session, "material.assign", json!({"bodies":[copied_body],"material":"Aluminum"}));
+    let sharp = 73.2 * 63.2 * 2.;
+    assert!((volume(&session, extrusion) - sharp).abs() < 1e-6);
+    assert!((volume(&session, copied_extrusion) - sharp).abs() < 1e-6);
+    run(&mut session, "parameters.change", json!({"name":copied_radius,"expression":"2 mm"}));
+    healthy(&session);
+    let state = session.model.state();
+    assert_eq!(state.sketch(sketch).unwrap().sketch.offsets[0].outputs.len(), 4);
+    assert_eq!(state.sketch(copied_sketch).unwrap().sketch.offsets[0].outputs.len(), 8);
+    assert!((volume(&session, extrusion) - sharp).abs() < 1e-6);
+    let rounded = 2. * (75.2 * 65.2 - (4. - std::f64::consts::PI) * 0.6 * 0.6);
+    assert!(
+        (volume(&session, copied_extrusion) - rounded).abs() < 0.002,
+        "copied rounded volume {} expected {rounded} bounds {:?}",
+        volume(&session, copied_extrusion),
+        session.model.state().bodies.last().unwrap().mesh().bounds()
+    );
+    assert_eq!(session.doc.materials.get(&source_body).map(String::as_str), Some("Brass"));
+    assert_eq!(session.doc.materials.get(&copied_body).map(String::as_str), Some("Aluminum"));
+    let reopened = Session::new(Document::from_json(&session.doc.to_json()).unwrap());
+    healthy(&reopened);
+    assert!((volume(&reopened, extrusion) - sharp).abs() < 1e-6);
+    assert!((volume(&reopened, copied_extrusion) - rounded).abs() < 0.002);
+    let state = reopened.world_state();
+    let bounds = state.body(&copied_body).unwrap().mesh().bounds();
+    assert!((bounds.min.x - (100. - 37.6)).abs() < 1e-6);
+    assert!((bounds.max.x - (100. + 37.6)).abs() < 1e-6);
+}

crates/engine/src/cmd/offset_topology_tests.rs

@@ -0,0 +1,109 @@
+#![allow(clippy::unwrap_used, clippy::panic)]
+use serde_json::{Value, json};
+use solvecraft_doc::{FeatureKind, ProfileSel};
+use solvecraft_geom::Vec3;
+
+use crate::Session;
+
+fn run(session: &mut Session, command: &str, params: Value) -> Value {
+    session.execute(command, &params).unwrap_or_else(|error| panic!("{command}: {error}"))
+}
+
+#[test]
+fn breaking_offset_preserves_downstream_material_history_and_source_independence() {
+    for distance in [0.2, 1.4] {
+        let (mut session, sketch, radius) = rounded_source();
+        let offset = run(&mut session, "sketch.offset", json!({"curves":["l1"],"distance":distance,"side":[0,0]}));
+        let association = offset["association"].as_str().unwrap().to_string();
+        let curves = session.model.state().sketch(sketch).unwrap().sketch.offset_boundary(&association).unwrap();
+        run(&mut session, "sketch.finish", json!({}));
+        run(&mut session, "solid.extrude", json!({"sketch":sketch,"profiles":{"offset_boundaries":[association]},"distance":2,"operation":"new"}));
+        let before_volume = session.world_state().bodies.last().unwrap().mesh().measure().volume.abs();
+        run(&mut session, "sketch.edit", json!({"sketch":sketch}));
+        let before = session.doc.to_json();
+        let history = session.undo.len();
+        run(&mut session, "sketch.offset.break", json!({"curve":association}));
+        assert_eq!(session.undo.len(), history + 1);
+        assert!(session.model.results.iter().all(|result| result.error.is_none()));
+        assert!(
+            matches!(&session.doc.features.last().unwrap().kind, FeatureKind::Extrude { profiles: ProfileSel::Curves { loops }, .. } if loops == &vec![curves.clone()])
+        );
+        let frozen = session.doc.to_json();
+        assert!((session.world_state().bodies.last().unwrap().mesh().measure().volume.abs() - before_volume).abs() < 1e-6);
+        run(&mut session, "edit.undo", json!({}));
+        assert_eq!(session.doc.to_json(), before);
+        run(&mut session, "edit.redo", json!({}));
+        assert_eq!(session.doc.to_json(), frozen);
+        run(&mut session, "parameters.change", json!({"name":radius,"expression":"2 mm"}));
+        assert!(session.model.results.iter().all(|result| result.error.is_none()));
+        assert!((session.world_state().bodies.last().unwrap().mesh().measure().volume.abs() - before_volume).abs() < 1e-6);
+        let reopened = Session::new(solvecraft_doc::Document::from_json(&session.doc.to_json()).unwrap());
+        assert!(reopened.model.results.iter().all(|result| result.error.is_none()));
+        assert!((reopened.world_state().bodies.last().unwrap().mesh().measure().volume.abs() - before_volume).abs() < 1e-6);
+    }
+}
+
+fn rounded_source() -> (Session, u64, String) {
+    let mut session = Session::default();
+    run(&mut session, "sketch.create", json!({"plane":"XY","name":"Rounded"}));
+    let sketch = session.active_sketch.unwrap();
+    run(&mut session, "sketch.rectangle.two_point", json!({"p0":[-38,-33],"p1":[38,33]}));
+    let fillet = run(&mut session, "sketch.fillet", json!({"points":["l1.start","l1.end","l2.end","l3.end"],"radius":"1 mm"}));
+    (session, sketch, fillet["param"].as_str().unwrap().to_string())
+}
+
+#[test]
+fn inset_past_corner_radius_creates_a_real_boundary_and_saved_profile_identity() {
+    let (mut session, sketch, _) = rounded_source();
+    let offset = run(&mut session, "sketch.offset", json!({"curves":["l1"],"distance":1.4,"side":[0,0]}));
+    assert_eq!(offset["curves"].as_array().unwrap().len(), 4);
+    let state = session.model.state();
+    let solved = state.sketch(sketch).unwrap();
+    let record = solved.sketch.offsets.last().unwrap();
+    let topology = record.topology.as_ref().unwrap();
+    let association = topology.id.clone();
+    assert_eq!(topology.roles.len(), 8);
+    assert_eq!(topology.roles.iter().filter(|role| role.retired).count(), 4);
+    assert_eq!(solved.sketch.offset_boundary(&association).unwrap(), record.outputs);
+    assert!(topology.roles.iter().filter(|role| role.retired).all(|role| solved.sketch.curve_index(&role.output).is_none()));
+    run(&mut session, "sketch.finish", json!({}));
+    run(
+        &mut session,
+        "solid.extrude",
+        json!({"sketch":sketch,"profiles":{"offset_boundaries":[association]},"distance":2,"operation":"new","name":"Inner"}),
+    );
+    let feature = session.doc.features.last().unwrap();
+    assert!(matches!(&feature.kind, FeatureKind::Extrude { profiles: ProfileSel::OffsetBoundaries { associations }, .. } if associations.len() == 1));
+    let check = |session: &Session| {
+        assert!(session.model.results.iter().all(|result| result.error.is_none()));
+        let state = session.world_state();
+        let body = state.bodies.last().unwrap();
+        // The exact inward parallel set is a sharp 73.2 by 63.2 rectangle.
+        let mesh = body.mesh();
+        assert!((mesh.measure().volume.abs() - 73.2 * 63.2 * 2.0).abs() < 1e-6);
+        assert!(mesh.contains(Vec3::new(36.5, 31.5, 1.0)));
+        assert!(!mesh.contains(Vec3::new(36.7, 31.5, 1.0)));
+        assert!(!mesh.contains(Vec3::new(36.5, 31.7, 1.0)));
+    };
+    check(&session);
+    let saved = session.doc.to_json();
+    let reopened = Session::new(solvecraft_doc::Document::from_json(&saved).unwrap());
+    check(&reopened);
+    assert_eq!(reopened.doc.to_json(), saved);
+    let undo = session.undo.len();
+    let redo = session.redo.len();
+    for params in [
+        json!({"profiles":{"offset_boundaries":[]}}),
+        json!({"profiles":{"offset_boundaries":["missing"]}}),
+        json!({"profiles":{"offset_boundaries":[association,association]}}),
+        json!({"profiles":[[record.outputs[0],record.outputs[1],record.outputs[2]]]}),
+    ] {
+        let mut params = params;
+        params["sketch"] = json!(sketch);
+        params["distance"] = json!(1);
+        assert!(session.execute("solid.extrude", &params).is_err());
+        assert_eq!(session.doc.to_json(), saved);
+        assert_eq!(session.undo.len(), undo);
+        assert_eq!(session.redo.len(), redo);
+    }
+}

crates/engine/src/cmd/plastic.rs

@@ -267,6 +267,7 @@ fn snap_fit(s: &mut Session, p: &Value) -> Result<Value> {
 
 #[cfg(test)]
 mod tests {
+    use solvecraft_geom::Vec3;
     use std::f64::consts::PI;
 
     use serde_json::{Value, json};
@@ -352,6 +353,40 @@ mod tests {
         assert!(s.execute("plastic.snap_fit", &json!({"position": [5, 5, 4], "direction": [0, 0, 1], "hook": [0, 0, 1], "length": 15, "thickness": 1.5, "width": 6, "catch_depth": 1, "catch_length": 3})).is_err());
     }
 
+    #[test]
+    fn enclosure_snap_fit_follows_resized_front_wall() {
+        let mut s = Session::default();
+        let script: Value = serde_json::from_str(include_str!("../../../../examples/acceptance/sensor_enclosure.json")).unwrap();
+        s.run_script(&script).unwrap();
+        let feature = s.doc.find_feature("SnapFit1").unwrap().clone();
+        run(&mut s, "parameters.change", json!({"name":"board_d","expression":"50 mm"}));
+        let before = s.model.state_before(feature.id);
+        let name = feature.face_names.first().unwrap();
+        let point = solvecraft_doc::naming::point_on_face(&before, name, Vec3::new(0., -28., 20.))
+            .expect("the original wall identity survives merged pieces")
+            .0;
+        assert!((point - Vec3::new(0., -33., 20.)).len() < 1e-8, "{point:?}");
+        assert!(s.model.results.iter().all(|result| result.error.is_none()));
+        let check = |session: &Session| {
+            let before = session.model.state_before(feature.id);
+            let after = &session.model.result(feature.id).unwrap().state;
+            let old = before.body("Case").unwrap();
+            let body = after.body("Case").unwrap();
+            let added = solvecraft_kernel::measure(&body.body).unwrap().volume - solvecraft_kernel::measure(&old.body).unwrap().volume;
+            // Rectangular arm + triangular catch; the small attachment overlap lies inside the wall.
+            assert!((added - (8. * 1.2 + 0.8 * 1.5 / 2.) * 6.).abs() < 0.05, "{added}");
+            let mesh = body.mesh();
+            assert!(mesh.contains(Vec3::new(0., -29., 19.4)), "the arm follows the inner wall");
+            assert!(mesh.contains(Vec3::new(0., -25.9, 20.2)), "the catch follows the arm");
+            assert!(!mesh.contains(Vec3::new(0., -22., 19.4)), "the old arm placement is empty");
+            assert!(!mesh.contains(Vec3::new(0., -24., 19.4)), "the arm ends at its specified length");
+        };
+        check(&s);
+        let cold = Session::new(solvecraft_doc::Document::from_json(&s.doc.to_json()).unwrap());
+        assert!(cold.model.results.iter().all(|result| result.error.is_none()));
+        check(&cold);
+    }
+
     fn plate() -> (Session, f64) {
         let mut s = Session::default();
         run(&mut s, "solid.box", json!({"length": 60, "width": 60, "height": 3}));

crates/engine/src/cmd/sheet_tests.rs

@@ -1103,3 +1103,458 @@ fn ring_cut_preserves_retained_island_through_unfold_and_refold() {
     assert!((volume(&mut s) - expected).abs() < 0.2);
     material_probes(&s);
 }
+
+fn retained_depth_check(s: &mut Session, want: f64, z0: f64, z1: f64) {
+    use solvecraft_geom::Vec3;
+    assert!((volume(s) - want).abs() < 1e-6, "{} vs {want}", volume(s));
+    let state = s.model.state();
+    assert_eq!(state.sheets.len(), 1);
+    assert_eq!(state.sheets[0].t, 2.5, "rule stock gauge is preserved");
+    assert!(state.bodies.iter().any(|b| b.body.contains(Vec3::new(25.0, 25.0, (z0 + z1) * 0.5))));
+    assert!(!state.bodies.iter().any(|b| b.body.contains(Vec3::new(25.0, 25.0, z0 - 0.1))));
+    assert!(!state.bodies.iter().any(|b| b.body.contains(Vec3::new(25.0, 25.0, z1 + 0.1))));
+    assert!(!state.bodies.iter().any(|b| b.body.contains(Vec3::new(10.0, 25.0, (z0 + z1) * 0.5))));
+    let bounds = state.bodies[0].mesh().bounds();
+    assert!((bounds.min.z - z0).abs() < 1e-8 && (bounds.max.z - z1).abs() < 1e-8, "{bounds:?}");
+}
+
+fn depth_step_reopen(s: &mut Session, suffix: &str, want: f64, inside: solvecraft_geom::Vec3, outside: solvecraft_geom::Vec3) {
+    let path = std::env::temp_dir().join(format!("solvecraft-depth-intersect-{suffix}-{}.step", std::process::id()));
+    run(s, "file.export", json!({"path":path.to_string_lossy()}));
+    let mut imported = Session::default();
+    run(&mut imported, "doc.open", json!({"path":path.to_string_lossy()}));
+    assert!((volume(&mut imported) - want).abs() < 1e-6);
+    assert!(imported.model.state().bodies.iter().any(|b| b.body.contains(inside)));
+    assert!(!imported.model.state().bodies.iter().any(|b| b.body.contains(outside)));
+    std::fs::remove_file(path).unwrap();
+}
+
+/// The generic sketch importer intentionally drops DXF layers/depth. Reimport only the
+/// material outline at a separately known depth, never pretend all entities reconstruct3D.
+fn dxf_outline_only(text: &str) -> String {
+    let lines: Vec<_> = text.lines().collect();
+    let pairs: Vec<_> = lines.as_chunks::<2>().0.iter().filter_map(|p| Some((p.first()?.trim(), *p.get(1)?))).collect();
+    let mut out = String::from("0\nSECTION\n2\nENTITIES\n");
+    let mut start = 0;
+    for end in 1..=pairs.len() {
+        if end == pairs.len() || pairs.get(end).is_some_and(|p| p.0 == "0") {
+            let entity = &pairs[start..end];
+            if entity.first().is_some_and(|p| matches!(p.1, "LINE" | "ARC" | "CIRCLE")) && entity.iter().any(|p| p.0 == "8" && p.1 == "OUTLINE") {
+                for (code, value) in entity {
+                    out.push_str(&format!("{code}\n{value}\n"));
+                }
+            }
+            start = end;
+        }
+    }
+    out.push_str("0\nENDSEC\n0\nEOF\n");
+    out
+}
+
+#[test]
+fn partial_depth_intersect_retains_bottom_top_and_middle_material_through_history_and_exports() {
+    use solvecraft_geom::Vec3;
+    for (offset, z0, z1, layers) in [
+        (0.0, 0.0, 1.0, vec![("top", 1.0, 2.5)]),
+        (1.5, 1.5, 2.5, vec![("bottom", 0.0, 1.5)]),
+        (0.5, 0.5, 1.5, vec![("bottom", 0.0, 0.5), ("top", 1.5, 2.5)]),
+    ] {
+        let mut s = Session::default();
+        base(&mut s, 100.0, 60.0);
+        rectangle_tool(&mut s, "RetainDepth", [20.0, 20.0], [30.0, 30.0]);
+        run(&mut s, "solid.extrude", json!({"sketch":"RetainDepth","distance":1,"start_offset":offset,"operation":"intersect","name":"RetainSlab"}));
+        retained_depth_check(&mut s, 100.0, z0, z1);
+        let exported = flat(&mut s);
+        assert_eq!(exported["thickness"], 2.5);
+        assert_eq!(exported["pockets"].as_array().unwrap().len(), layers.len());
+        let dxf = run(&mut s, "sheet.export_dxf", json!({}))["dxf"].as_str().unwrap().to_string();
+        for (side, a, b) in &layers {
+            assert!(
+                exported["pockets"]
+                    .as_array()
+                    .unwrap()
+                    .iter()
+                    .any(|p| p["side"] == *side && p["z0_mm"] == *a && p["z1_mm"] == *b && p["depth_mm"] == b - a)
+            );
+            assert!(dxf.contains(&format!("POCKET_{}_Z{a:.6}_TO_{b:.6}_MM", side.to_uppercase())));
+        }
+        let outline = dxf_outline_only(&dxf);
+        assert_eq!(solvecraft_io::read_dxf(&outline).unwrap().len(), 4);
+        let mut outline_import = Session::default();
+        run(&mut outline_import, "sketch.insert_dxf", json!({"text":outline,"name":"Outline"}));
+        run(&mut outline_import, "sketch.finish", json!({}));
+        run(&mut outline_import, "solid.extrude", json!({"distance":1}));
+        assert!((volume(&mut outline_import) - 100.0).abs() < 1e-6);
+        run(&mut s, "edit.undo", json!({}));
+        assert!((volume(&mut s) - 15000.0).abs() < 1e-6);
+        run(&mut s, "edit.redo", json!({}));
+        for command in ["sheet.unfold", "sheet.refold"] {
+            run(&mut s, command, json!({}));
+            retained_depth_check(&mut s, 100.0, z0, z1);
+            assert_eq!(flat(&mut s)["pockets"], exported["pockets"]);
+        }
+        let mut reopened = Session::new(solvecraft_doc::Document::from_json(&s.doc.to_json()).unwrap());
+        retained_depth_check(&mut reopened, 100.0, z0, z1);
+        depth_step_reopen(&mut s, &format!("offset{offset}"), 100.0, Vec3::new(25.0, 25.0, (z0 + z1) * 0.5), Vec3::new(25.0, 25.0, z1 + 0.1));
+    }
+}
+
+#[test]
+fn partial_depth_intersect_preserves_prior_pockets_and_actual_interval_intersections() {
+    use solvecraft_geom::Vec3;
+    let mut s = Session::default();
+    base(&mut s, 100.0, 60.0);
+    rectangle_tool(&mut s, "OldPocket", [20.0, 20.0], [25.0, 30.0]);
+    run(&mut s, "solid.extrude", json!({"sketch":"OldPocket","distance":1,"operation":"cut"}));
+    rectangle_tool(&mut s, "RetainDepth", [20.0, 20.0], [30.0, 30.0]);
+    run(&mut s, "solid.extrude", json!({"sketch":"RetainDepth","distance":1,"start_offset":0.5,"operation":"intersect"}));
+    for command in [None, Some("sheet.unfold"), Some("sheet.refold")] {
+        if let Some(command) = command {
+            run(&mut s, command, json!({}));
+        }
+        assert!((volume(&mut s) - 75.0).abs() < 1e-6);
+        let state = s.model.state();
+        let body = &state.bodies[0].body;
+        assert!(!body.contains(Vec3::new(22.0, 25.0, 0.75)));
+        assert!(body.contains(Vec3::new(22.0, 25.0, 1.25)));
+        assert!(body.contains(Vec3::new(27.0, 25.0, 0.75)));
+        assert!(!body.contains(Vec3::new(27.0, 25.0, 0.25)));
+    }
+    let records = s.model.state().sheets[0].pockets.clone();
+    run(&mut s, "solid.extrude", json!({"sketch":"RetainDepth","distance":1.5,"start_offset":0.25,"operation":"intersect"}));
+    assert!((volume(&mut s) - 75.0).abs() < 1e-6);
+    assert_eq!(s.model.state().sheets[0].pockets, records, "no-change leaves replay work unchanged");
+    run(&mut s, "solid.extrude", json!({"sketch":"RetainDepth","distance":0.25,"start_offset":1.0,"operation":"intersect"}));
+    assert!((volume(&mut s) - 25.0).abs() < 1e-6);
+    run(&mut s, "sheet.unfold", json!({}));
+    assert!((volume(&mut s) - 25.0).abs() < 1e-6);
+    let mut cold = Session::new(solvecraft_doc::Document::from_json(&s.doc.to_json()).unwrap());
+    assert!((volume(&mut cold) - 25.0).abs() < 1e-6);
+    depth_step_reopen(&mut s, "prior", 25.0, Vec3::new(22.0, 25.0, 1.125), Vec3::new(22.0, 25.0, 0.75));
+}
+
+#[test]
+fn partial_depth_intersect_keeps_disconnected_tool_islands_and_annular_curves() {
+    use solvecraft_geom::Vec3;
+    let mut s = Session::default();
+    base(&mut s, 100.0, 60.0);
+    rectangle_tool(&mut s, "Islands", [20.0, 20.0], [30.0, 30.0]);
+    run(&mut s, "sketch.edit", json!({"sketch":"Islands"}));
+    run(&mut s, "sketch.rectangle.two_point", json!({"p0":[60,20],"p1":[70,30]}));
+    run(&mut s, "sketch.finish", json!({}));
+    run(&mut s, "solid.extrude", json!({"sketch":"Islands","distance":1,"operation":"intersect"}));
+    for command in [None, Some("sheet.unfold"), Some("sheet.refold")] {
+        if let Some(command) = command {
+            run(&mut s, command, json!({}));
+        }
+        assert!((volume(&mut s) - 200.0).abs() < 1e-6);
+        assert_eq!(s.model.state().sheets[0].flat_regions().unwrap().len(), 2);
+        for x in [25.0, 65.0] {
+            assert!(s.model.state().bodies[0].body.contains(Vec3::new(x, 25.0, 0.5)));
+        }
+        assert!(!s.model.state().bodies[0].body.contains(Vec3::new(45.0, 25.0, 0.5)));
+    }
+    depth_step_reopen(&mut s, "islands", 200.0, Vec3::new(65.0, 25.0, 0.5), Vec3::new(45.0, 25.0, 0.5));
+    let mut ring = Session::default();
+    base(&mut ring, 100.0, 60.0);
+    run(&mut ring, "sketch.create", json!({"plane":"XY","name":"Ring"}));
+    for radius in [10.0, 5.0] {
+        run(&mut ring, "sketch.circle.center", json!({"center":[50,30],"radius":radius}));
+    }
+    run(&mut ring, "sketch.finish", json!({}));
+    run(&mut ring, "solid.extrude", json!({"sketch":"Ring","profiles":[{"point":[57,30]}],"distance":1,"operation":"intersect"}));
+    for command in [None, Some("sheet.unfold"), Some("sheet.refold")] {
+        if let Some(command) = command {
+            run(&mut ring, command, json!({}));
+        }
+        let state = ring.model.state();
+        let area: f64 = state.sheets[0].flat_regions().unwrap().iter().map(|r| r.area()).sum();
+        assert!((area - 75.0 * PI).abs() < 1e-8);
+        assert!((volume(&mut ring) - 75.0 * PI).abs() < 0.1);
+        assert!(state.bodies[0].body.contains(Vec3::new(57.0, 30.0, 0.5)));
+        assert!(!state.bodies[0].body.contains(Vec3::new(50.0, 30.0, 0.5)));
+        assert!(!state.bodies[0].body.contains(Vec3::new(57.0, 30.0, 1.5)));
+    }
+    let dxf = run(&mut ring, "sheet.export_dxf", json!({}))["dxf"].as_str().unwrap().to_string();
+    assert!(dxf.contains("POCKET_TOP_Z1.000000_TO_2.500000_MM"));
+    assert_eq!(solvecraft_io::read_dxf(&dxf_outline_only(&dxf)).unwrap().len(), 2);
+}
+
+#[test]
+fn partial_depth_intersect_deletes_material_already_removed_by_a_pocket_atomically() {
+    let mut s = Session::default();
+    base(&mut s, 100.0, 60.0);
+    rectangle_tool(&mut s, "Removed", [20.0, 20.0], [30.0, 30.0]);
+    run(&mut s, "solid.extrude", json!({"sketch":"Removed","distance":1,"operation":"cut"}));
+    run(&mut s, "solid.extrude", json!({"sketch":"Removed","distance":1,"operation":"intersect"}));
+    assert!(s.model.state().bodies.is_empty());
+    assert!(s.model.state().sheets.is_empty());
+    run(&mut s, "edit.undo", json!({}));
+    assert!((volume(&mut s) - 14900.0).abs() < 1e-6);
+    run(&mut s, "edit.redo", json!({}));
+    assert!(s.model.state().bodies.is_empty());
+}
+
+#[test]
+fn partial_depth_intersect_flipped_tool_and_transferred_sheet_keep_depth_side_and_world_pose() {
+    use solvecraft_geom::Vec3;
+    let mut flipped = Session::default();
+    base(&mut flipped, 100.0, 60.0);
+    run(&mut flipped, "sketch.create", json!({"name":"FlippedTool","plane":{"origin":[0,0,2.5],"x_dir":[1,0,0],"y_dir":[0,-1,0]}}));
+    run(&mut flipped, "sketch.rectangle.two_point", json!({"p0":[20,-30],"p1":[30,-20]}));
+    run(&mut flipped, "sketch.finish", json!({}));
+    run(&mut flipped, "solid.extrude", json!({"sketch":"FlippedTool","distance":1,"operation":"intersect"}));
+    retained_depth_check(&mut flipped, 100.0, 1.5, 2.5);
+    assert_eq!(flat(&mut flipped)["pockets"][0]["side"], "bottom");
+    assert_eq!(flat(&mut flipped)["pockets"][0]["depth_mm"], 1.5);
+    let mut s = Session::default();
+    base(&mut s, 100.0, 60.0);
+    rectangle_tool(&mut s, "RetainDepth", [20.0, 20.0], [30.0, 30.0]);
+    run(&mut s, "solid.extrude", json!({"sketch":"RetainDepth","distance":1,"start_offset":0.5,"operation":"intersect","name":"RetainSlab"}));
+    let before = s.world_state().bodies[0].mesh().bounds();
+    let name = s.model.state().sheets[0].body.clone();
+    let destination = run(&mut s, "component.create", json!({"name":"Destination","parent":0}));
+    let owner = destination["component"].as_u64().unwrap();
+    let occurrence = destination["occurrence"].as_u64().unwrap();
+    run(&mut s, "occurrence.move", json!({"occurrence":occurrence,"translate":[30,20,10],"axis":[1,0,0],"angle":"90 deg","capture":true}));
+    run(&mut s, "component.move_bodies", json!({"component":owner,"bodies":[name]}));
+    for command in [None, Some("sheet.unfold"), Some("sheet.refold")] {
+        if let Some(command) = command {
+            run(&mut s, command, json!({}));
+        }
+        let state = s.model.state();
+        let sh = &state.sheets[0];
+        assert_eq!(sh.t, 2.5);
+        assert!(sh.frame.origin.dist(Vec3::new(-30.0, -10.0, 20.0)) < 1e-8);
+        assert!(sh.frame.normal().dist(Vec3::Y) < 1e-8);
+        assert_eq!(sh.pockets.len(), 2);
+        assert_eq!(state.body(&name).unwrap().component, owner);
+        assert!(state.body(&name).unwrap().transferred);
+        let world = s.world_state();
+        let body = &world.body(&name).unwrap().body;
+        assert!(body.contains(Vec3::new(25.0, 25.0, 1.0)));
+        assert!(!body.contains(Vec3::new(25.0, 25.0, 0.25)));
+        assert!(!body.contains(Vec3::new(25.0, 25.0, 2.0)));
+        let bounds = world.body(&name).unwrap().mesh().bounds();
+        assert!(before.min.dist(bounds.min) < 1e-8 && before.max.dist(bounds.max) < 1e-8);
+        assert!((solvecraft_kernel::measure(body).unwrap().volume - 100.0).abs() < 1e-6);
+    }
+    let mut reopened = Session::new(solvecraft_doc::Document::from_json(&s.doc.to_json()).unwrap());
+    let reopened_world = reopened.world_state();
+    let body = &reopened_world.body(&name).unwrap().body;
+    assert!(body.contains(Vec3::new(25.0, 25.0, 1.0)));
+    assert!((solvecraft_kernel::measure(body).unwrap().volume - 100.0).abs() < 1e-6);
+    run(&mut reopened, "timeline.edit", json!({"feature":"RetainSlab","set":{"extent":{"distance":"1.5"}}}));
+    let world = reopened.world_state();
+    let body = &world.body(&name).unwrap().body;
+    assert!((solvecraft_kernel::measure(body).unwrap().volume - 150.0).abs() < 1e-6);
+    assert!(body.contains(Vec3::new(25.0, 25.0, 1.75)));
+    assert!(!body.contains(Vec3::new(25.0, 25.0, 2.25)));
+}
+
+#[test]
+fn partial_depth_intersect_full_gauge_in_rotated_frames_does_not_invent_pockets() {
+    use solvecraft_geom::Vec3;
+    for (angle, translate) in [(37.0, [30.0, 20.0, 10.0]), (121.0, [12345.678, 98765.432, 4321.123])] {
+        let mut s = Session::default();
+        base(&mut s, 100.0, 60.0);
+        let name = s.model.state().sheets[0].body.clone();
+        let destination = run(&mut s, "component.create", json!({"name":"Destination","parent":0}));
+        let owner = destination["component"].as_u64().unwrap();
+        run(
+            &mut s,
+            "occurrence.move",
+            json!({"occurrence":destination["occurrence"],"translate":translate,"axis":[1,2,3],"angle":format!("{angle} deg"),"capture":true}),
+        );
+        run(&mut s, "component.move_bodies", json!({"component":owner,"bodies":[name]}));
+        run(&mut s, "component.activate", json!({"component":owner}));
+        run(&mut s, "sketch.create", json!({"name":"WorldTool","plane":{"origin":[0,0,0],"x_dir":[1,0,0],"y_dir":[0,1,0]}}));
+        run(&mut s, "sketch.rectangle.two_point", json!({"p0":[20,20],"p1":[30,30]}));
+        run(&mut s, "sketch.finish", json!({}));
+        let mut tool_session = Session::new(solvecraft_doc::Document::from_json(&s.doc.to_json()).unwrap());
+        run(&mut tool_session, "solid.extrude", json!({"sketch":"WorldTool","distance":2.5,"body_name":"CapWitness"}));
+        let witness_state = tool_session.model.state();
+        let witness = &witness_state.body("CapWitness").unwrap().body;
+        let tool_plane = witness_state.sketches.last().unwrap().plane;
+        let sources = witness.face_sources().unwrap();
+        assert_eq!(sources.len(), witness.face_count());
+        let mut cap_count = 0;
+        for (index, source) in sources.iter().enumerate() {
+            if let Some(solvecraft_kernel::FaceSource::CertifiedExtrudeCap { high, plane, .. }) = source {
+                cap_count += 1;
+                let current = witness.planar_face(index).unwrap();
+                assert!(current.normal().cross(tool_plane.normal()).len() < 1e-10);
+                assert!((current.origin - plane.origin).dot(tool_plane.normal()).abs() < 1e-8);
+                assert!(((plane.origin - tool_plane.origin).dot(tool_plane.normal()) - if *high { 2.5 } else { 0.0 }).abs() < 1e-8);
+            }
+        }
+        assert_eq!(cap_count, 2);
+        run(&mut s, "solid.extrude", json!({"sketch":"WorldTool","distance":2.5,"operation":"intersect","name":"PostTransferRetain"}));
+        for command in [None, Some("sheet.unfold"), Some("sheet.refold")] {
+            if let Some(command) = command {
+                run(&mut s, command, json!({}));
+            }
+            assert!(s.model.state().sheets[0].pockets.is_empty(), "full gauge must not acquire roundoff-depth pockets");
+            let world = s.world_state();
+            let body = &world.body(&name).unwrap().body;
+            assert!((solvecraft_kernel::measure(body).unwrap().volume - 250.0).abs() < 1e-5);
+            assert!(body.contains(Vec3::new(25.0, 25.0, 0.1)));
+            assert!(body.contains(Vec3::new(25.0, 25.0, 2.4)));
+            assert!(!body.contains(Vec3::new(10.0, 25.0, 1.0)));
+        }
+        let mut cold = Session::new(solvecraft_doc::Document::from_json(&s.doc.to_json()).unwrap());
+        assert!(cold.model.state().sheets[0].pockets.is_empty());
+        assert!(flat(&mut cold)["pockets"].as_array().unwrap().is_empty());
+        run(&mut s, "timeline.edit", json!({"feature":"PostTransferRetain","set":{"extent":{"distance":"1","start_offset":"0.5"}}}));
+        for command in [None, Some("sheet.unfold"), Some("sheet.refold")] {
+            if let Some(command) = command {
+                run(&mut s, command, json!({}));
+            }
+            assert_eq!(s.model.state().sheets[0].pockets.len(), 2);
+            let world = s.world_state();
+            let body = &world.body(&name).unwrap().body;
+            let measured = solvecraft_kernel::measure(body).unwrap().volume;
+            assert!((measured - 100.0).abs() < 1e-5, "retained volume {measured}");
+            assert!(body.contains(Vec3::new(25.0, 25.0, 1.0)));
+            assert!(!body.contains(Vec3::new(25.0, 25.0, 0.1)));
+            assert!(!body.contains(Vec3::new(25.0, 25.0, 2.4)));
+        }
+        let cold = Session::new(solvecraft_doc::Document::from_json(&s.doc.to_json()).unwrap());
+        let world = cold.world_state();
+        let body = &world.body(&name).unwrap().body;
+        assert!((solvecraft_kernel::measure(body).unwrap().volume - 100.0).abs() < 1e-5);
+        assert!(body.contains(Vec3::new(25.0, 25.0, 1.0)));
+        assert!(!body.contains(Vec3::new(25.0, 25.0, 0.1)));
+    }
+}
+
+#[test]
+fn partial_depth_intersect_planar_to_object_retains_current_target_depth() {
+    use solvecraft_geom::Vec3;
+    let mut s = Session::default();
+    base(&mut s, 100.0, 60.0);
+    let name = s.model.state().sheets[0].body.clone();
+    run(&mut s, "solid.box", json!({"corner":[200,0,1.5],"length":10,"width":10,"height":1,"body_name":"Roof"}));
+    rectangle_tool(&mut s, "Tool", [20.0, 20.0], [30.0, 30.0]);
+    run(&mut s, "solid.extrude", json!({"sketch":"Tool","to":[205,5,1.5],"start_offset":0.5,"operation":"intersect","participants":[name]}));
+    for command in [None, Some("sheet.unfold"), Some("sheet.refold")] {
+        if let Some(command) = command {
+            run(&mut s, command, json!({"body":name}));
+        }
+        let state = s.model.state();
+        let body = &state.body(&name).unwrap().body;
+        assert!((solvecraft_kernel::measure(body).unwrap().volume - 100.0).abs() < 1e-6);
+        assert!(body.contains(Vec3::new(25.0, 25.0, 1.0)));
+        assert!(!body.contains(Vec3::new(25.0, 25.0, 0.1)));
+        assert!(!body.contains(Vec3::new(25.0, 25.0, 2.0)));
+        assert_eq!(state.sheets[0].pockets.len(), 2);
+        assert!((solvecraft_kernel::measure(&state.body("Roof").unwrap().body).unwrap().volume - 100.0).abs() < 1e-6);
+    }
+    let cold = Session::new(solvecraft_doc::Document::from_json(&s.doc.to_json()).unwrap());
+    assert!((solvecraft_kernel::measure(&cold.model.state().body(&name).unwrap().body).unwrap().volume - 100.0).abs() < 1e-6);
+}
+
+#[test]
+fn partial_depth_intersect_curved_to_object_refuses_unrepresentable_depth_atomically() {
+    let mut s = Session::default();
+    base(&mut s, 100.0, 60.0);
+    let name = s.model.state().sheets[0].body.clone();
+    run(&mut s, "solid.cylinder", json!({"base":[25,20,12],"axis":[0,1,0],"radius":11,"height":10,"body_name":"CurvedRoof"}));
+    rectangle_tool(&mut s, "Tool", [24.0, 23.0], [26.0, 27.0]);
+    let before = s.doc.to_json();
+    let error =
+        s.execute("solid.extrude", &json!({"sketch":"Tool","to":[36,25,12],"operation":"intersect","participants":[name]})).unwrap_err().to_string();
+    assert!(error.contains("sheet machining"), "{error}");
+    assert_eq!(s.doc.to_json(), before);
+    for command in [None, Some("sheet.unfold"), Some("sheet.refold")] {
+        if let Some(command) = command {
+            run(&mut s, command, json!({"body":name}));
+        }
+        let state = s.model.state();
+        assert!((solvecraft_kernel::measure(&state.body(&name).unwrap().body).unwrap().volume - 15000.0).abs() < 1e-6);
+        assert!(state.sheets[0].pockets.is_empty());
+    }
+}
+
+#[test]
+fn partial_depth_intersect_curved_to_object_preserves_current_trimmed_cap_footprint() {
+    use solvecraft_geom::Vec3;
+    let mut s = Session::default();
+    base(&mut s, 100.0, 60.0);
+    let name = s.model.state().sheets[0].body.clone();
+    run(&mut s, "solid.cylinder", json!({"base":[25,25,0],"axis":[0,0,1],"radius":2,"height":20,"body_name":"CurvedRoof"}));
+    run(&mut s, "solid.box", json!({"corner":[19,19,1],"length":12,"width":12,"height":1,"body_name":"StopPlate"}));
+    run(&mut s, "solid.combine", json!({"target":"CurvedRoof","tools":["StopPlate"],"operation":"join"}));
+    rectangle_tool(&mut s, "Tool", [20.0, 20.0], [30.0, 30.0]);
+    let mut tool_session = Session::new(solvecraft_doc::Document::from_json(&s.doc.to_json()).unwrap());
+    run(&mut tool_session, "solid.extrude", json!({"sketch":"Tool","to":[27,25,10],"body_name":"TrimWitness"}));
+    let ts = tool_session.model.state();
+    let witness = &ts.body("TrimWitness").unwrap().body;
+    assert!((solvecraft_kernel::measure(witness).unwrap().volume - (100.0 - 4.0 * std::f64::consts::PI)).abs() < 0.01);
+    assert!(witness.contains(Vec3::new(21.0, 21.0, 0.5)));
+    assert!(!witness.contains(Vec3::new(25.0, 25.0, 0.5)));
+    run(&mut s, "solid.extrude", json!({"sketch":"Tool","to":[27,25,10],"operation":"intersect","participants":[name]}));
+    for command in [None, Some("sheet.unfold"), Some("sheet.refold")] {
+        if let Some(command) = command {
+            run(&mut s, command, json!({"body":name}));
+        }
+        let state = s.model.state();
+        let body = &state.body(&name).unwrap().body;
+        let measured = solvecraft_kernel::measure(body).unwrap().volume;
+        assert!((measured - (100.0 - 4.0 * std::f64::consts::PI)).abs() < 0.01);
+        let area: f64 = state.sheets[0].flat_regions().unwrap().iter().map(|r| r.area()).sum();
+        assert!((area - (100.0 - 4.0 * std::f64::consts::PI)).abs() < 1e-8);
+        assert!(body.contains(Vec3::new(21.0, 21.0, 0.5)));
+        assert!(!body.contains(Vec3::new(25.0, 25.0, 0.5)));
+        assert!(!body.contains(Vec3::new(21.0, 21.0, 1.5)));
+    }
+    let cold = Session::new(solvecraft_doc::Document::from_json(&s.doc.to_json()).unwrap());
+    assert!(!cold.model.state().body(&name).unwrap().body.contains(Vec3::new(25.0, 25.0, 0.5)));
+    let dxf = run(&mut s, "sheet.export_dxf", json!({"body":name}))["dxf"].as_str().unwrap().to_string();
+    assert!(dxf.contains("POCKET_TOP_Z1.000000_TO_2.500000_MM"));
+    let outline = dxf_outline_only(&dxf);
+    assert_eq!(solvecraft_io::read_dxf(&outline).unwrap().len(), 5);
+    let mut outline_import = Session::default();
+    run(&mut outline_import, "sketch.insert_dxf", json!({"text":outline,"name":"Outline"}));
+    run(&mut outline_import, "sketch.finish", json!({}));
+    run(&mut outline_import, "solid.extrude", json!({"distance":1,"profiles":[{"point":[21,21]}]}));
+    assert!((volume(&mut outline_import) - (100.0 - 4.0 * std::f64::consts::PI)).abs() < 0.01);
+    assert!(!outline_import.model.state().bodies[0].body.contains(Vec3::new(25.0, 25.0, 0.5)));
+    let path = std::env::temp_dir().join(format!("solvecraft-current-trim-cap-{}.step", std::process::id()));
+    run(&mut s, "file.export", json!({"path":path.to_string_lossy(),"bodies":[name]}));
+    let mut imported = Session::default();
+    run(&mut imported, "doc.open", json!({"path":path.to_string_lossy()}));
+    assert!((volume(&mut imported) - (100.0 - 4.0 * std::f64::consts::PI)).abs() < 0.01);
+    assert!(!imported.model.state().bodies[0].body.contains(Vec3::new(25.0, 25.0, 0.5)));
+    std::fs::remove_file(path).unwrap();
+}
+
+#[test]
+fn partial_depth_intersect_sub_extrusion_resolution_layers_refuse_atomically() {
+    for (distance, offset) in [(2.5 - 1e-8, 1e-8), (2.5 - 1e-8, 0.0), (1e-8, 0.0)] {
+        let mut s = Session::default();
+        base(&mut s, 100.0, 60.0);
+        let name = s.model.state().sheets[0].body.clone();
+        let destination = run(&mut s, "component.create", json!({"name":"Far","parent":0}));
+        let owner = destination["component"].as_u64().unwrap();
+        run(
+            &mut s,
+            "occurrence.move",
+            json!({"occurrence":destination["occurrence"],"translate":[12345.678,98765.432,4321.123],"axis":[1,2,3],"angle":"121 deg","capture":true}),
+        );
+        run(&mut s, "component.move_bodies", json!({"component":owner,"bodies":[name]}));
+        run(&mut s, "component.activate", json!({"component":owner}));
+        run(&mut s, "sketch.create", json!({"name":"Tool","plane":{"origin":[0,0,0],"x_dir":[1,0,0],"y_dir":[0,1,0]}}));
+        run(&mut s, "sketch.rectangle.two_point", json!({"p0":[20,20],"p1":[30,30]}));
+        run(&mut s, "sketch.finish", json!({}));
+        let before = s.doc.to_json();
+        let error = s
+            .execute("solid.extrude", &json!({"sketch":"Tool","distance":distance,"start_offset":offset,"operation":"intersect"}))
+            .unwrap_err()
+            .to_string();
+        assert!(error.contains("resolution") || error.contains("distance is zero") || error.contains("sheet machining"), "{error}");
+        assert_eq!(s.doc.to_json(), before);
+        assert!(s.model.state().sheets[0].pockets.is_empty());
+        assert!((solvecraft_kernel::measure(&s.world_state().body(&name).unwrap().body).unwrap().volume - 15000.0).abs() < 1e-5);
+    }
+}

crates/engine/src/cmd/sketch.rs

@@ -873,7 +873,7 @@ fn arc_center(s: &mut Session, p: &Value) -> Result<Value> {
             let end = c.pos() + Vec2::from_angle((a.pos() - c.pos()).angle() + sw.to_radians()) * a.pos().dist(c.pos());
             let cid = match &id {
                 Some(i) => i.clone(),
-                None => sk.fresh("a"),
+                None => sk.fresh("a")?,
             };
             let ai = match a.idx() {
                 Some(i) => i,
@@ -1748,6 +1748,26 @@ fn sketch_delete(s: &mut Session, p: &Value) -> Result<Value> {
                 return Err(bad(cmd, format!("unknown sketch entity `{id}`")));
             }
         }
+        let selected_curves = curves.iter().copied().collect::<std::collections::BTreeSet<_>>();
+        let selected_points = points.iter().copied().collect::<std::collections::BTreeSet<_>>();
+        let removed = sk
+            .curves
+            .iter()
+            .enumerate()
+            .filter(|(index, curve)| selected_curves.contains(index) || curve.kind.point_ids().iter().any(|point| selected_points.contains(point)))
+            .map(|(_, curve)| curve.id.as_str())
+            .collect::<std::collections::BTreeSet<_>>();
+        for offset in &sk.offsets {
+            let Some(topology) = &offset.topology else { continue };
+            if offset.outputs.iter().any(|id| removed.contains(id.as_str()))
+                && topology
+                    .roles
+                    .iter()
+                    .any(|role| !role.retired && role.kind == solvecraft_sketch::OffsetRoleKind::Arc && !removed.contains(role.output.as_str()))
+            {
+                return Err(bad(cmd, "break the offset association before deleting only part of its curved boundary"));
+            }
+        }
         sk.constraints.retain(|c| !cons.contains(&c.id));
         let pids: Vec<String> = points.iter().filter_map(|q| sk.points.get(*q).map(|x| x.id.clone())).collect();
         sk.remove_curves(&curves);

crates/engine/src/cmd/sketch_modify.rs

@@ -4,6 +4,7 @@
 use std::f64::consts::TAU;
 
 use serde_json::{Value, json};
+use solvecraft_doc::ProfileSel;
 use solvecraft_geom::Vec2;
 use solvecraft_sketch::{ConstraintKind, Curve, CurveKind, Shape, Sketch, intersections};
 
@@ -95,7 +96,9 @@ fn curve_arg(sk: &Sketch, p: &Value, cmd: &str) -> Result<usize> {
     if sk.is_linked_curve(c) {
         return Err(bad(cmd, format!("`{id}` is projected geometry: break its link first")));
     }
-    if sk.freeform_offsets.iter().any(|offset| offset.output == id) {
+    if sk.freeform_offsets.iter().any(|offset| offset.output == id)
+        || sk.offsets.iter().filter_map(|offset| offset.topology.as_ref()).any(|topology| topology.roles.iter().any(|role| role.output == id))
+    {
         return Err(bad(cmd, "break the offset association before editing its output"));
     }
     Ok(c)
@@ -184,7 +187,7 @@ fn split_at(sk: &mut Sketch, ci: usize, ts: &[f64]) -> Result<(Vec<usize>, Vec<u
     }
     let mut pieces = vec![ci];
     let mut push = |sk: &mut Sketch, kind: CurveKind, prefix: &str| -> Result<()> {
-        let id = sk.fresh(prefix);
+        let id = sk.fresh(prefix)?;
         sk.curves.push(Curve { id, kind, construction, reversed: false, link: None, centerline: false, fixed: false });
         pieces.push(sk.curves.len() - 1);
         Ok(())
@@ -549,7 +552,7 @@ fn keep_corner(sk: &mut Sketch, c: usize, [(ca, na), (cb, nb)]: [(usize, usize);
     let virtual_corner = if used || c == 0 {
         None
     } else {
-        let id = sk.fresh("corner");
+        let id = sk.fresh("corner")?;
         if let Some(pt) = sk.points.get_mut(c) {
             pt.id = id.clone();
         }
@@ -934,6 +937,14 @@ fn offset(s: &mut Session, p: &Value) -> Result<Value> {
         sk.refresh_offsets()?;
         let sel: Vec<usize> = ids.iter().map(|i| sk.curve_index(i).ok_or_else(|| bad(cmd, format!("unknown curve `{i}`")))).collect::<Result<_>>()?;
         let first = *sel.first().ok_or_else(|| bad(cmd, "no curves"))?;
+        if sk.offsets.iter().filter_map(|offset| offset.topology.as_ref()).any(|topology| {
+            topology.roles.iter().any(|role| role.retired) && topology.roles.iter().any(|role| !role.retired && ids.contains(&role.output))
+        }) {
+            return Err(bad(
+                cmd,
+                "offsets of a boundary with retired corner arcs are not supported yet; break its offset association to use the current fixed topology",
+            ));
+        }
         let mut made = Vec::new();
         let mut cons = Vec::new();
         // Circles offset on their own.
@@ -954,8 +965,9 @@ fn offset(s: &mut Session, p: &Value) -> Result<Value> {
                 outputs: ids_of(sk, &made),
                 distance: r - nr,
                 closed: true,
+                topology: None,
             });
-            return Ok((ids_of(sk, &made), cons));
+            return Ok((ids_of(sk, &made), cons, None));
         }
         let pool: Vec<usize> = if use_chain {
             (0..sk.curves.len())
@@ -986,7 +998,31 @@ fn offset(s: &mut Session, p: &Value) -> Result<Value> {
             }
             let (source, forward) = order[0];
             let output = sk.add_freeform_offset(source, forward, d)?;
-            return Ok((ids_of(sk, &[output]), cons));
+            return Ok((ids_of(sk, &[output]), cons, None));
+        }
+        let sources = order
+            .iter()
+            .map(|(index, forward)| {
+                sk.curves.get(*index).map(|curve| (curve.id.clone(), *forward)).ok_or_else(|| bad(cmd, "offset chain source vanished"))
+            })
+            .collect::<Result<Vec<_>>>()?;
+        if closed && sk.convex_offset_supported(&sources)? {
+            let created = sk.add_convex_offset(sources.clone(), d)?;
+            let roles = sk
+                .offsets
+                .iter()
+                .filter_map(|offset| offset.topology.as_ref())
+                .find(|topology| topology.id == created.association)
+                .map(|topology| topology.roles.clone())
+                .ok_or_else(|| bad(cmd, "new offset association is missing"))?;
+            for (source, role) in sources.iter().zip(&roles) {
+                if role.kind == solvecraft_sketch::OffsetRoleKind::Line {
+                    let a = sk.curve_index(&source.0).ok_or_else(|| bad(cmd, "offset source line vanished"))?;
+                    let b = sk.curve_index(&role.output).ok_or_else(|| bad(cmd, "offset output line vanished"))?;
+                    cons.push(add_c(sk, ConstraintKind::Parallel { a, b })?);
+                }
+            }
+            return Ok((created.curves, cons, Some(created.association)));
         }
         let pieces: Vec<Piece> =
             order.iter().map(|(c, f)| offset_piece(sk, *c, *f, d)).collect::<Option<_>>().ok_or_else(|| bad(cmd, "the offset collapses an arc"))?;
@@ -1072,23 +1108,32 @@ fn offset(s: &mut Session, p: &Value) -> Result<Value> {
         let outputs = ids_of(sk, &made);
         if pieces.iter().all(|p| !matches!(p, Piece::Free(_))) {
             let sources = order.iter().filter_map(|(i, forward)| sk.curves.get(*i).map(|c| (c.id.clone(), *forward))).collect();
-            sk.offsets.push(solvecraft_sketch::OffsetChain { sources, outputs: outputs.clone(), distance: d, closed });
+            sk.offsets.push(solvecraft_sketch::OffsetChain { sources, outputs: outputs.clone(), distance: d, closed, topology: None });
             sk.refresh_offsets()?;
         }
-        Ok((outputs, cons))
+        Ok((outputs, cons, None))
     })?;
-    Ok(json!({"curves": out.0, "constraints": out.1, "sketch": info}))
+    let mut response = json!({"curves":out.0,"constraints":out.1,"sketch":info});
+    if let Some(association) = out.2 {
+        response["association"] = json!(association);
+    }
+    Ok(response)
 }
 
 fn break_offset(s: &mut Session, p: &Value) -> Result<Value> {
     let cmd = "sketch.offset.break";
+    let sketch = super::sketch::target_sketch(s, p, cmd)?;
     let (out, info) = edit(s, p, cmd, true, |sk, doc| {
         let output = str_(p, "curve").ok_or_else(|| bad(cmd, "`curve` must name an offset output"))?;
-        let record = sk
-            .freeform_offsets
+        let record = sk.freeform_offsets.iter().position(|record| record.output == output);
+        let topology = sk
+            .offsets
             .iter()
-            .position(|record| record.output == output)
-            .ok_or_else(|| bad(cmd, "that curve has no free-form offset association"))?;
+            .filter_map(|record| record.topology.as_ref())
+            .any(|record| record.id == output || record.roles.iter().any(|role| role.output == output));
+        if record.is_none() && !topology {
+            return Err(bad(cmd, "curve is not an offset output"));
+        }
         // A parameter edit may have changed the evaluated source without
         // rewriting the stored fit points. Break must freeze the displayed,
         // current dimensioned geometry, rather than its stale stored predecessor.
@@ -1102,6 +1147,19 @@ fn break_offset(s: &mut Session, p: &Value) -> Result<Value> {
             return Err(bad(cmd, "cannot break an offset with conflicting derived dimensions"));
         }
         sk.validate_periodic_splines()?;
+        if let Some(association) = sk
+            .offsets
+            .iter()
+            .filter_map(|record| record.topology.as_ref())
+            .find(|record| record.id == output || record.roles.iter().any(|role| role.output == output))
+            .map(|record| record.id.clone())
+        {
+            freeze_offset_profiles(doc, sketch, sk, &association)?;
+        }
+        if let Some(curves) = sk.break_offset_topology(output)? {
+            return Ok((output.to_string(), Some(curves)));
+        }
+        let record = record.ok_or_else(|| bad(cmd, "offset association changed while materializing its current geometry"))?;
         let ci = sk.curve_index(output).ok_or_else(|| bad(cmd, "missing offset output"))?;
         let indices = sk.curves[ci].kind.point_ids();
         sk.freeform_offsets.remove(record);
@@ -1110,9 +1168,74 @@ fn break_offset(s: &mut Session, p: &Value) -> Result<Value> {
                 point.fixed = false;
             }
         }
-        Ok(output.to_string())
+        Ok((output.to_string(), None))
     })?;
-    Ok(json!({"curve":out,"sketch":info}))
+    let mut response = json!({"curve":out.0,"sketch":info});
+    if let Some(curves) = out.1 {
+        response["curves"] = json!(curves);
+    }
+    Ok(response)
+}
+
+/// A broken logical boundary becomes ordinary geometry. Keep downstream features
+/// on that exact current boundary while other associations retain their full roles.
+fn freeze_offset_profiles(doc: &mut solvecraft_doc::Document, sketch: u64, boundary: &Sketch, association: &str) -> Result<()> {
+    let cmd = "sketch.offset.break";
+    let mut groups = std::collections::BTreeMap::new();
+    let mut work = 0usize;
+    for offset in &boundary.offsets {
+        let Some(topology) = &offset.topology else { continue };
+        work = work.saturating_add(topology.roles.len());
+        if groups.len() >= 128 || topology.roles.len() > 512 || work > 1_000_000 {
+            return Err(bad(cmd, "too many offset roles to freeze safely"));
+        }
+        let reserved = topology.roles.iter().map(|role| role.output.clone()).collect::<Vec<_>>();
+        if groups.insert(topology.id.clone(), (offset.outputs.clone(), reserved)).is_some() {
+            return Err(bad(cmd, "ambiguous offset association identity"));
+        }
+    }
+    let (active, reserved) = groups.get(association).ok_or_else(|| bad(cmd, "offset association disappeared before freezing"))?;
+    let mut reserved_sorted = reserved.clone();
+    reserved_sorted.sort();
+    for feature in &mut doc.features {
+        for (source, selection) in feature.kind.profile_sels_mut() {
+            if source != sketch {
+                continue;
+            }
+            match selection {
+                ProfileSel::OffsetBoundaries { associations } if associations.iter().any(|id| id == association) => {
+                    let mut loops = Vec::with_capacity(associations.len());
+                    for id in associations.iter() {
+                        let (current, all_roles) = groups.get(id).ok_or_else(|| bad(cmd, format!("cannot freeze missing offset boundary `{id}`")))?;
+                        let roles = if id == association { current } else { all_roles };
+                        work = work.saturating_add(roles.len());
+                        if work > 1_000_000 {
+                            return Err(bad(cmd, "too many downstream offset references to freeze safely"));
+                        }
+                        loops.push(roles.clone());
+                    }
+                    *selection = ProfileSel::Curves { loops };
+                }
+                ProfileSel::Curves { loops } => {
+                    for ids in loops {
+                        work = work.saturating_add(ids.len());
+                        if work > 1_000_000 {
+                            return Err(bad(cmd, "too many downstream curve references to freeze safely"));
+                        }
+                        if ids.len() == reserved_sorted.len() {
+                            let mut sorted = ids.clone();
+                            sorted.sort();
+                            if sorted == reserved_sorted {
+                                *ids = active.clone();
+                            }
+                        }
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+    Ok(())
 }
 
 // ---------------------------------------------------------------------------------------------
@@ -1199,7 +1322,7 @@ fn copy_through(
                 }
             }
         };
-        let id = sk.fresh(prefix);
+        let id = sk.fresh(prefix)?;
         sk.curves.push(Curve {
             id,
             kind,

crates/engine/src/cmd/sketch_modify_tests.rs

@@ -826,3 +826,88 @@ fn analytic_offset_partial_delete_releases_survivors_preserves_source_and_undo()
     run(&mut s, "edit.undo", json!({}));
     assert_eq!(s.doc.to_json(), before);
 }
+
+#[test]
+fn periodic_offset_extrusion_survives_post_extrude_span_changes_and_cold_reopen() {
+    let mut s = new_sketch();
+    run(&mut s, "sketch.ellipse", json!({"center":[0,0],"major":[10,0],"minor_radius":5}));
+    run(&mut s, "sketch.dimension", json!({"entities":["e1"],"type":"major","value":10}));
+    let a = run(&mut s, "sketch.offset", json!({"curves":["e1"],"distance":-1,"chain":false}))["curves"][0].as_str().unwrap().to_string();
+    run(&mut s, "sketch.offset", json!({"curves":[a],"distance":-0.5,"chain":false}));
+    let sk_id = s.active_sketch.unwrap();
+    let initial = solvecraft_sketch::find_profiles(&sketch(&s));
+    let (index, ring) = initial.iter().enumerate().min_by(|(_, a), (_, b)| a.area.total_cmp(&b.area)).unwrap();
+    let initial_count = ring.outer_curves.len();
+    let boundary = ring.whole_curve_boundaries().unwrap();
+    run(&mut s, "sketch.finish", json!({}));
+    run(&mut s, "solid.extrude", json!({"sketch":sk_id,"profiles":[index],"distance":3,"operation":"new"}));
+    let initial_doc = s.doc.to_json();
+    for major in [12.0, 16.0, 20.0] {
+        run(&mut s, "parameters.change", json!({"name":"d1","expression":major}));
+        let state = s.world_state();
+        let sk = state.sketch(sk_id).unwrap();
+        let ring = sk.profiles.iter().find(|p| p.whole_curve_boundaries().as_ref() == Some(&boundary)).unwrap();
+        assert_ne!(ring.outer_curves.len(), initial_count, "the repro must actually change graph span multiplicity");
+        // Length-only intent leaves the centre and axis pose free. Measure that rigid frame,
+        // then derive independent ellipse normal probes (not fitted-output points).
+        let CurveKind::Ellipse { c, m, r } = sk.sketch.curves[sk.sketch.curve_index("e1").unwrap()].kind else { panic!("ellipse") };
+        let centre = sk.sketch.point(c).unwrap();
+        let axis = sk.sketch.point(m).unwrap() - centre;
+        assert!((axis.len() - major).abs() < 1e-6);
+        assert!((r - 5.0).abs() < 1e-6);
+        let u = axis / axis.len();
+        let v = Vec2::new(-u.y, u.x);
+        let t: f64 = 0.2;
+        let ellipse = centre + u * (major * t.cos()) + v * (5.0 * t.sin());
+        let gradient = u * (t.cos() / major) + v * (t.sin() / 5.0);
+        let normal = gradient / gradient.len();
+        eprintln!("major={major} centre={centre:?} axis={axis:?}");
+        assert!(ring.region.contains(ellipse + normal * 1.25), "major={major}, ring area={}", ring.area);
+        assert!(!ring.region.contains(ellipse + normal * 0.5));
+        assert!(!ring.region.contains(ellipse + normal * 1.75));
+        let n = 4096;
+        let h = std::f64::consts::TAU / n as f64;
+        let perimeter = (0..=n)
+            .map(|i| {
+                let t = i as f64 * h;
+                (major * major * t.sin().powi(2) + 25.0 * t.cos().powi(2)).sqrt()
+                    * if i == 0 || i == n {
+                        1.0
+                    } else if i % 2 == 0 {
+                        2.0
+                    } else {
+                        4.0
+                    }
+            })
+            .sum::<f64>()
+            * h
+            / 3.0;
+        let expected = (0.5 * perimeter + 1.25 * std::f64::consts::PI) * 3.0;
+        assert_eq!(state.bodies.len(), 1);
+        let body = &state.bodies[0].body;
+        for (distance, material) in [(1.25, true), (0.5, false), (1.75, false)] {
+            let point = ellipse + normal * distance;
+            assert_eq!(body.contains(solvecraft_geom::Vec3::new(point.x, point.y, 1.5)), material);
+        }
+        // Repeat at the exact major-axis seam as a physical material control.
+        for (distance, material) in [(1.25, true), (0.5, false), (1.75, false)] {
+            let point = centre + u * (major + distance);
+            assert_eq!(ring.region.contains(point), material);
+            assert_eq!(body.contains(solvecraft_geom::Vec3::new(point.x, point.y, 1.5)), material);
+        }
+        let volume = solvecraft_kernel::measure(body).unwrap().volume;
+        assert!((volume - expected).abs() < 0.05, "{major}: {volume} vs independent {expected}");
+        let mut cold = Session { doc: solvecraft_doc::format::read(&s.doc.to_json()).unwrap().into(), ..Default::default() };
+        cold.refresh();
+        let cold_state = cold.world_state();
+        assert_eq!(cold_state.bodies.len(), 1);
+        let cold_volume = solvecraft_kernel::measure(&cold_state.bodies[0].body).unwrap().volume;
+        assert!((cold_volume - volume).abs() < 1e-8);
+        let edited = s.doc.to_json();
+        run(&mut s, "edit.undo", json!({}));
+        assert_eq!(s.doc.to_json(), initial_doc);
+        run(&mut s, "edit.redo", json!({}));
+        assert_eq!(s.doc.to_json(), edited);
+        run(&mut s, "edit.undo", json!({}));
+    }
+}