diff --git a/ROADMAP.md b/ROADMAP.md
index 497a94ef..6f38346b 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -52,7 +52,7 @@ headline counts in-scope tabs only and lists the deferred ones separately.
 | M10 | Sheet metal: flange (base, edge, contour), hem, unfold/refold, convert, flat pattern + DXF, rules: done (oracle 67-76). PLASTIC enclosure subset: Boss, Rib, Web, Lip/Groove, Snap Fit, Rest, Plastic Rules (library, edit, assign; rule draft and clearance as feature defaults): done, no Fusion oracle (licence), 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, DXF export), Boss, Lip/Groove, Snap Fit, Rest, Manage and Assign Plastic Rules; Bend (Fold) has no engine command yet | in progress | 36 |
 | M11 | 2D drawings | deferred | — |
 | M12 | Release: installers, signing, docs, performance | planned | 16 |
-| M13 | Never lose work: atomic saves (temporary file, flush, rename; a crash at any moment leaves the old file or the new one) with the replaced version kept as `<file>.bak`; autosave of unsaved changes to the recovery folder every 5 minutes (preference) and after big operations, only when something changed; "Recover unsaved design?" on the next launch (`doc.recovery_list`, `doc.recover`, `doc.recovery_discard`); a kill-mid-save test (process killed while saving a 0.5 MB design 25 times). Next: file format version and migrations, old-design corpus, fuzzed design files | in progress | 6 |
+| M13 | Never lose work: atomic saves (temporary file, flush, rename; a crash at any moment leaves the old file or the new one) with the replaced version kept as `<file>.bak`; autosave of unsaved changes to the recovery folder every 5 minutes (preference) and after big operations, only when something changed; "Recover unsaved design?" on the next launch (`doc.recovery_list`, `doc.recover`, `doc.recovery_discard`); a kill-mid-save test (process killed while saving a 0.5 MB design 25 times). File format: `"format": "solvecraft/2"`, older formats upgraded step by step (`doc::format`), newer ones refused with a message, out-of-range numbers and broken placements refused; a corpus of designs saved by M0, components-era, joints-era and current builds (apps/solvecraft-cli/tests/corpus) that must open and evaluate as saved; damaged and hostile variants (truncation, bit flips, hostile values, removed keys, repeated features, deep nesting) never panic | done | 6 |
 
 ## Known limitations
 
diff --git a/apps/solvecraft-cli/tests/corpus/README.md b/apps/solvecraft-cli/tests/corpus/README.md
new file mode 100644
index 00000000..7215abbc
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/README.md
@@ -0,0 +1,20 @@
+# Design file corpus
+
+Designs saved by older SolveCraft builds. `tests/design_corpus.rs` opens each one with the
+current build and checks that it evaluates as it did when saved (the `.expected.json` next to
+it is `solvecraft-cli eval` of that file by the build that saved it: bodies, volumes, areas,
+world bounding boxes), that it is upgraded to the current file format, and that damaged and
+hostile variants of it never panic.
+
+| File | Saved by | Era |
+|---|---|---|
+| `m0-box-fillet-hole` | 3714342 | M0: sketch, parameters, extrude, fillet, cut |
+| `m0-revolve-primitives` | 3714342 | M0: revolve, primitives, combine, chamfer, timeline edit |
+| `components-arm` | 97d03e3 | components and occurrences: move, copy, Paste New, ground |
+| `joints-hinge` | c2309eb | joints: revolute hinge driven by a parameter |
+| `modern-sheet-metal` | bd98035 | sheet metal contour flange (oracle 72) |
+| `modern-path-pattern` | bd98035 | pattern on path (oracle 53) |
+| `modern-plastic` | bd98035 | shell, lip, boss, rest, snap fit, plastic rule |
+
+The scripts that made them are in `scripts/`. Never regenerate a file with a newer build: the
+point is that it was written by the old one. Add new files for new eras instead.
diff --git a/apps/solvecraft-cli/tests/corpus/components-arm.expected.json b/apps/solvecraft-cli/tests/corpus/components-arm.expected.json
new file mode 100644
index 00000000..193fac1b
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/components-arm.expected.json
@@ -0,0 +1,134 @@
+{
+  "bodies": [
+    {
+      "area_mm2": 700.5299915783324,
+      "bbox": {
+        "max": [
+          10.0,
+          10.0,
+          10.000000000000007
+        ],
+        "min": [
+          0.0,
+          0.0,
+          -6.080836915950756e-16
+        ]
+      },
+      "center_of_mass": [
+        4.999999998722992,
+        4.999999999366269,
+        4.999999996470206
+      ],
+      "density_g_cm3": 1.29,
+      "edges": 14,
+      "face_types": {
+        "cylinder": 1,
+        "plane": 6
+      },
+      "faces": 7,
+      "kernel": {
+        "edges": 18,
+        "faces": 8,
+        "shells": 1,
+        "vertices": 12
+      },
+      "mass_g": 1.1279207478827844,
+      "material": "Default",
+      "name": "Base",
+      "vertices": 10,
+      "volume_mm3": 874.3571689013833
+    }
+  ],
+  "body_count": 1,
+  "params": [],
+  "sketches": [
+    {
+      "curves": 1,
+      "dof": 3,
+      "id": 11,
+      "name": "S1",
+      "profiles": 1,
+      "status": "solved"
+    }
+  ],
+  "timeline": [
+    {
+      "error": null,
+      "id": 1,
+      "ms": 13.568090999999999,
+      "name": "Box1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "BoxFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 4,
+      "ms": 1.004123,
+      "name": "Box2",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "BoxFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 5,
+      "ms": 6.818065,
+      "name": "Fillet1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "FilletFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 9,
+      "ms": 0.223829,
+      "name": "Box2 (copy)",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "BoxFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 10,
+      "ms": 6.139636,
+      "name": "Fillet1 (copy)",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "FilletFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 11,
+      "ms": 0.045728,
+      "name": "S1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "Sketch",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 12,
+      "ms": 1537.323948,
+      "name": "Extrude1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "ExtrudeFeature",
+      "warning": null
+    }
+  ],
+  "total": {
+    "area_mm2": 700.5299915783324,
+    "edges": 14,
+    "faces": 7,
+    "mass_g": 1.1279207478827844,
+    "vertices": 10,
+    "volume_mm3": 874.3571689013833
+  }
+}
diff --git a/apps/solvecraft-cli/tests/corpus/components-arm.solvecraft b/apps/solvecraft-cli/tests/corpus/components-arm.solvecraft
new file mode 100644
index 00000000..8fb36b01
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/components-arm.solvecraft
@@ -0,0 +1,263 @@
+{
+  "format": "solvecraft/1",
+  "name": "Untitled",
+  "units": "mm",
+  "params": [],
+  "features": [
+    {
+      "id": 1,
+      "name": "Box1",
+      "suppressed": false,
+      "body_names": [
+        "Base"
+      ],
+      "type": "box",
+      "corner": [
+        0.0,
+        0.0,
+        0.0
+      ],
+      "length": "10",
+      "width": "10",
+      "height": "10",
+      "operation": "new_body"
+    },
+    {
+      "id": 4,
+      "name": "Box2",
+      "suppressed": false,
+      "body_names": [
+        "ArmBody"
+      ],
+      "component": 2,
+      "type": "box",
+      "corner": [
+        20.0,
+        0.0,
+        0.0
+      ],
+      "length": "10",
+      "width": "4",
+      "height": "4",
+      "operation": "new_body"
+    },
+    {
+      "id": 5,
+      "name": "Fillet1",
+      "suppressed": false,
+      "component": 2,
+      "type": "fillet",
+      "edges": [
+        [
+          25.0,
+          4.0,
+          4.0
+        ]
+      ],
+      "radius": "1"
+    },
+    {
+      "id": 9,
+      "name": "Box2 (copy)",
+      "suppressed": false,
+      "component": 7,
+      "type": "box",
+      "corner": [
+        20.0,
+        0.0,
+        0.0
+      ],
+      "length": "10",
+      "width": "4",
+      "height": "4",
+      "operation": "new_body"
+    },
+    {
+      "id": 10,
+      "name": "Fillet1 (copy)",
+      "suppressed": false,
+      "component": 7,
+      "type": "fillet",
+      "edges": [
+        [
+          25.0,
+          4.0,
+          4.0
+        ]
+      ],
+      "radius": "1"
+    },
+    {
+      "id": 11,
+      "name": "S1",
+      "suppressed": false,
+      "type": "sketch",
+      "plane": {
+        "type": "origin",
+        "name": "XY"
+      },
+      "sketch": {
+        "points": [
+          {
+            "id": "origin",
+            "pos": [
+              0.0,
+              0.0
+            ],
+            "fixed": true
+          },
+          {
+            "id": "c1.center",
+            "pos": [
+              5.0,
+              5.0
+            ],
+            "fixed": false
+          }
+        ],
+        "curves": [
+          {
+            "id": "c1",
+            "type": "circle",
+            "c": 1,
+            "r": 2.0,
+            "construction": false
+          }
+        ],
+        "constraints": [],
+        "counters": {
+          "c": 1
+        }
+      }
+    },
+    {
+      "id": 12,
+      "name": "Extrude1",
+      "suppressed": false,
+      "type": "extrude",
+      "sketch": 11,
+      "profiles": {
+        "type": "all"
+      },
+      "extent": {
+        "distance": "10",
+        "direction": "positive"
+      },
+      "operation": "cut"
+    }
+  ],
+  "next_id": 13,
+  "components": [
+    {
+      "id": 2,
+      "name": "Arm",
+      "parent": 0
+    },
+    {
+      "id": 7,
+      "name": "Arm (copy)",
+      "parent": 0
+    }
+  ],
+  "occurrences": [
+    {
+      "id": 3,
+      "component": 2,
+      "parent": 0,
+      "name": "Arm:1",
+      "transform": [
+        [
+          1.0,
+          0.0,
+          0.0,
+          0.0
+        ],
+        [
+          0.0,
+          1.0,
+          0.0,
+          0.0
+        ],
+        [
+          0.0,
+          0.0,
+          1.0,
+          0.0
+        ],
+        [
+          0.0,
+          50.0,
+          0.0,
+          1.0
+        ]
+      ],
+      "grounded": true
+    },
+    {
+      "id": 6,
+      "component": 2,
+      "parent": 0,
+      "name": "Arm:2",
+      "transform": [
+        [
+          1.0,
+          0.0,
+          0.0,
+          0.0
+        ],
+        [
+          0.0,
+          1.0,
+          0.0,
+          0.0
+        ],
+        [
+          0.0,
+          0.0,
+          1.0,
+          0.0
+        ],
+        [
+          0.0,
+          70.0,
+          0.0,
+          1.0
+        ]
+      ],
+      "grounded": false
+    },
+    {
+      "id": 8,
+      "component": 7,
+      "parent": 0,
+      "name": "Arm (copy):1",
+      "transform": [
+        [
+          1.0,
+          0.0,
+          0.0,
+          0.0
+        ],
+        [
+          0.0,
+          1.0,
+          0.0,
+          0.0
+        ],
+        [
+          0.0,
+          0.0,
+          1.0,
+          0.0
+        ],
+        [
+          0.0,
+          20.0,
+          0.0,
+          1.0
+        ]
+      ],
+      "grounded": false
+    }
+  ]
+}
\ No newline at end of file
diff --git a/apps/solvecraft-cli/tests/corpus/joints-hinge.expected.json b/apps/solvecraft-cli/tests/corpus/joints-hinge.expected.json
new file mode 100644
index 00000000..28908df3
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/joints-hinge.expected.json
@@ -0,0 +1,217 @@
+{
+  "bodies": [
+    {
+      "area_mm2": 2820.0,
+      "bbox": {
+        "max": [
+          40.0,
+          30.0,
+          3.0
+        ],
+        "min": [
+          0.0,
+          0.0,
+          0.0
+        ]
+      },
+      "center_of_mass": [
+        20.0,
+        15.0,
+        1.5
+      ],
+      "density_g_cm3": 1.29,
+      "edges": 12,
+      "face_types": {
+        "plane": 6
+      },
+      "faces": 6,
+      "kernel": {
+        "edges": 12,
+        "faces": 6,
+        "shells": 1,
+        "vertices": 8
+      },
+      "mass_g": 4.644,
+      "material": "Default",
+      "name": "Body1",
+      "vertices": 8,
+      "volume_mm3": 3600.0
+    },
+    {
+      "area_mm2": 1105.7821673177034,
+      "bbox": {
+        "max": [
+          40.00000000000002,
+          37.0,
+          8.000000000000002
+        ],
+        "min": [
+          0.0,
+          29.0,
+          -6.661338147750943e-16
+        ]
+      },
+      "center_of_mass": [
+        20.00000000000423,
+        32.99999999999611,
+        3.9999999999995404
+      ],
+      "density_g_cm3": 1.29,
+      "edges": 2,
+      "face_types": {
+        "cylinder": 1,
+        "plane": 2
+      },
+      "faces": 3,
+      "kernel": {
+        "edges": 6,
+        "faces": 4,
+        "shells": 1,
+        "vertices": 4
+      },
+      "mass_g": 2.593268071855663,
+      "material": "Default",
+      "name": "Body2",
+      "vertices": 2,
+      "volume_mm3": 2010.2853270198937
+    },
+    {
+      "area_mm2": 2820.0,
+      "bbox": {
+        "max": [
+          40.0,
+          32.00000000000008,
+          37.000000000000064
+        ],
+        "min": [
+          0.0,
+          29.000000000000075,
+          7.000000000000064
+        ]
+      },
+      "center_of_mass": [
+        20.0,
+        30.500000000000075,
+        22.00000000000007
+      ],
+      "density_g_cm3": 1.29,
+      "edges": 12,
+      "face_types": {
+        "plane": 6
+      },
+      "faces": 6,
+      "kernel": {
+        "edges": 12,
+        "faces": 6,
+        "shells": 1,
+        "vertices": 8
+      },
+      "mass_g": 4.643999999999996,
+      "material": "Default",
+      "name": "Body3",
+      "vertices": 8,
+      "volume_mm3": 3599.9999999999964
+    },
+    {
+      "area_mm2": 1105.782167317711,
+      "bbox": {
+        "max": [
+          40.00000000000002,
+          37.000000000000085,
+          8.000000000000064
+        ],
+        "min": [
+          0.0,
+          29.000000000000075,
+          6.394884621840902e-14
+        ]
+      },
+      "center_of_mass": [
+        20.000000000004935,
+        32.99999999999709,
+        3.999999999999749
+      ],
+      "density_g_cm3": 1.29,
+      "edges": 2,
+      "face_types": {
+        "cylinder": 1,
+        "plane": 2
+      },
+      "faces": 3,
+      "kernel": {
+        "edges": 6,
+        "faces": 4,
+        "shells": 1,
+        "vertices": 4
+      },
+      "mass_g": 2.59326807185558,
+      "material": "Default",
+      "name": "Body4",
+      "vertices": 2,
+      "volume_mm3": 2010.2853270198293
+    }
+  ],
+  "body_count": 4,
+  "params": [
+    {
+      "comment": "",
+      "error": null,
+      "expression": "90 deg",
+      "model": false,
+      "name": "open_angle",
+      "unit": "deg",
+      "value": 1.5707963267948966
+    }
+  ],
+  "sketches": [],
+  "timeline": [
+    {
+      "error": null,
+      "id": 3,
+      "ms": 1.1335799999999998,
+      "name": "Box1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "BoxFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 4,
+      "ms": 0.580462,
+      "name": "Cylinder1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "CylinderFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 7,
+      "ms": 0.257673,
+      "name": "Box2",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "BoxFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 8,
+      "ms": 0.5234019999999999,
+      "name": "Cylinder2",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "CylinderFeature",
+      "warning": null
+    }
+  ],
+  "total": {
+    "area_mm2": 7851.564334635414,
+    "edges": 28,
+    "faces": 18,
+    "mass_g": 14.474536143711237,
+    "vertices": 20,
+    "volume_mm3": 11220.570654039719
+  }
+}
diff --git a/apps/solvecraft-cli/tests/corpus/joints-hinge.solvecraft b/apps/solvecraft-cli/tests/corpus/joints-hinge.solvecraft
new file mode 100644
index 00000000..d83f1767
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/joints-hinge.solvecraft
@@ -0,0 +1,225 @@
+{
+  "format": "solvecraft/1",
+  "name": "Untitled",
+  "units": "mm",
+  "params": [
+    {
+      "name": "open_angle",
+      "expr": "90 deg",
+      "unit": "deg",
+      "model": false
+    }
+  ],
+  "features": [
+    {
+      "id": 3,
+      "name": "Box1",
+      "suppressed": false,
+      "param_names": [
+        "d1",
+        "d2",
+        "d3"
+      ],
+      "component": 1,
+      "type": "box",
+      "corner": [
+        0.0,
+        0.0,
+        0.0
+      ],
+      "length": "40",
+      "width": "30",
+      "height": "3",
+      "operation": "new_body"
+    },
+    {
+      "id": 4,
+      "name": "Cylinder1",
+      "suppressed": false,
+      "param_names": [
+        "d4",
+        "d5"
+      ],
+      "component": 1,
+      "type": "cylinder",
+      "base": [
+        0.0,
+        33.0,
+        4.0
+      ],
+      "axis": [
+        1.0,
+        0.0,
+        0.0
+      ],
+      "radius": "4",
+      "height": "40",
+      "operation": "new_body"
+    },
+    {
+      "id": 7,
+      "name": "Box2",
+      "suppressed": false,
+      "param_names": [
+        "d6",
+        "d7",
+        "d8"
+      ],
+      "component": 5,
+      "type": "box",
+      "corner": [
+        0.0,
+        0.0,
+        0.0
+      ],
+      "length": "40",
+      "width": "30",
+      "height": "3",
+      "operation": "new_body"
+    },
+    {
+      "id": 8,
+      "name": "Cylinder2",
+      "suppressed": false,
+      "param_names": [
+        "d9",
+        "d10"
+      ],
+      "component": 5,
+      "type": "cylinder",
+      "base": [
+        0.0,
+        33.0,
+        4.0
+      ],
+      "axis": [
+        1.0,
+        0.0,
+        0.0
+      ],
+      "radius": "4",
+      "height": "40",
+      "operation": "new_body"
+    }
+  ],
+  "next_id": 9,
+  "components": [
+    {
+      "id": 1,
+      "name": "LeafA",
+      "parent": 0
+    },
+    {
+      "id": 5,
+      "name": "LeafB",
+      "parent": 0
+    }
+  ],
+  "occurrences": [
+    {
+      "id": 2,
+      "component": 1,
+      "parent": 0,
+      "name": "LeafA:1",
+      "transform": [
+        [
+          1.0,
+          0.0,
+          0.0,
+          0.0
+        ],
+        [
+          0.0,
+          1.0,
+          0.0,
+          0.0
+        ],
+        [
+          0.0,
+          0.0,
+          1.0,
+          0.0
+        ],
+        [
+          0.0,
+          0.0,
+          0.0,
+          1.0
+        ]
+      ],
+      "grounded": true
+    },
+    {
+      "id": 6,
+      "component": 5,
+      "parent": 0,
+      "name": "LeafB:1",
+      "transform": [
+        [
+          1.0,
+          0.0,
+          0.0,
+          0.0
+        ],
+        [
+          0.0,
+          6.123233995736766e-17,
+          -1.0,
+          0.0
+        ],
+        [
+          0.0,
+          1.0,
+          6.123233995736766e-17,
+          0.0
+        ],
+        [
+          0.0,
+          29.000000000000075,
+          37.000000000000064,
+          1.0
+        ]
+      ],
+      "grounded": false
+    }
+  ],
+  "assembly": {
+    "joints": [
+      {
+        "id": 1,
+        "name": "Hinge",
+        "kind": "revolute",
+        "a": {
+          "occurrence": 2,
+          "snap": {
+            "type": "circle_center",
+            "pick": [
+              1.0,
+              37.0,
+              4.0
+            ]
+          }
+        },
+        "b": {
+          "occurrence": 6,
+          "snap": {
+            "type": "circle_center",
+            "pick": [
+              1.0,
+              37.0,
+              4.0
+            ]
+          }
+        },
+        "values": [
+          1.5707963267948966
+        ],
+        "limits": [
+          null
+        ],
+        "offset": 0.0,
+        "angle": 0.0
+      }
+    ]
+  }
+}
\ No newline at end of file
diff --git a/apps/solvecraft-cli/tests/corpus/m0-box-fillet-hole.expected.json b/apps/solvecraft-cli/tests/corpus/m0-box-fillet-hole.expected.json
new file mode 100644
index 00000000..75a15fee
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/m0-box-fillet-hole.expected.json
@@ -0,0 +1,128 @@
+{
+  "bodies": [
+    {
+      "area_mm2": 5641.5699696719,
+      "bbox": {
+        "max": [
+          40.0,
+          30.0,
+          20.00000000000001
+        ],
+        "min": [
+          0.0,
+          0.0,
+          -2.331468351865795e-15
+        ]
+      },
+      "center_of_mass": [
+        20.0333953680467,
+        15.02475683626249,
+        9.999999936169297
+      ],
+      "edges": 17,
+      "face_types": {
+        "cylinder": 2,
+        "plane": 6
+      },
+      "faces": 8,
+      "kernel": {
+        "edges": 21,
+        "faces": 9,
+        "shells": 1,
+        "vertices": 14
+      },
+      "name": "Body1",
+      "vertices": 12,
+      "volume_mm3": 22391.21832759239
+    }
+  ],
+  "body_count": 1,
+  "params": [
+    {
+      "comment": "",
+      "error": null,
+      "expression": "40 mm",
+      "model": false,
+      "name": "width",
+      "unit": "mm",
+      "value": 40.0
+    }
+  ],
+  "sketches": [
+    {
+      "curves": 4,
+      "dof": 4,
+      "id": 1,
+      "name": "Sketch1",
+      "profiles": 1,
+      "status": "solved"
+    },
+    {
+      "curves": 1,
+      "dof": 3,
+      "id": 4,
+      "name": "Sketch2",
+      "profiles": 1,
+      "status": "solved"
+    }
+  ],
+  "timeline": [
+    {
+      "error": null,
+      "id": 1,
+      "ms": 0.043782999999999996,
+      "name": "Sketch1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "Sketch",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 2,
+      "ms": 1.609402,
+      "name": "Extrude1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "ExtrudeFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 3,
+      "ms": 11.196359,
+      "name": "Fillet1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "FilletFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 4,
+      "ms": 0.031249,
+      "name": "Sketch2",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "Sketch",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 5,
+      "ms": 1378.231746,
+      "name": "Extrude2",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "ExtrudeFeature",
+      "warning": null
+    }
+  ],
+  "total": {
+    "area_mm2": 5641.5699696719,
+    "edges": 17,
+    "faces": 8,
+    "vertices": 12,
+    "volume_mm3": 22391.21832759239
+  }
+}
diff --git a/apps/solvecraft-cli/tests/corpus/m0-box-fillet-hole.solvecraft b/apps/solvecraft-cli/tests/corpus/m0-box-fillet-hole.solvecraft
new file mode 100644
index 00000000..e917f445
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/m0-box-fillet-hole.solvecraft
@@ -0,0 +1,208 @@
+{
+  "format": "solvecraft/1",
+  "name": "Untitled",
+  "units": "mm",
+  "params": [
+    {
+      "name": "width",
+      "expr": "40 mm",
+      "unit": "mm",
+      "model": false
+    }
+  ],
+  "features": [
+    {
+      "id": 1,
+      "name": "Sketch1",
+      "suppressed": false,
+      "type": "sketch",
+      "plane": {
+        "type": "origin",
+        "name": "XY"
+      },
+      "sketch": {
+        "points": [
+          {
+            "id": "origin",
+            "pos": [
+              0.0,
+              0.0
+            ],
+            "fixed": true
+          },
+          {
+            "id": "p1",
+            "pos": [
+              0.0,
+              0.0
+            ],
+            "fixed": false
+          },
+          {
+            "id": "p2",
+            "pos": [
+              40.0,
+              0.0
+            ],
+            "fixed": false
+          },
+          {
+            "id": "p3",
+            "pos": [
+              40.0,
+              30.0
+            ],
+            "fixed": false
+          },
+          {
+            "id": "p4",
+            "pos": [
+              0.0,
+              30.0
+            ],
+            "fixed": false
+          }
+        ],
+        "curves": [
+          {
+            "id": "l5",
+            "type": "line",
+            "a": 1,
+            "b": 2,
+            "construction": false
+          },
+          {
+            "id": "l6",
+            "type": "line",
+            "a": 2,
+            "b": 3,
+            "construction": false
+          },
+          {
+            "id": "l7",
+            "type": "line",
+            "a": 3,
+            "b": 4,
+            "construction": false
+          },
+          {
+            "id": "l8",
+            "type": "line",
+            "a": 4,
+            "b": 1,
+            "construction": false
+          }
+        ],
+        "constraints": [
+          {
+            "id": "k9",
+            "type": "horizontal",
+            "l": 0
+          },
+          {
+            "id": "k10",
+            "type": "horizontal",
+            "l": 2
+          },
+          {
+            "id": "k11",
+            "type": "vertical",
+            "l": 1
+          },
+          {
+            "id": "k12",
+            "type": "vertical",
+            "l": 3
+          }
+        ],
+        "next_id": 13
+      }
+    },
+    {
+      "id": 2,
+      "name": "Extrude1",
+      "suppressed": false,
+      "type": "extrude",
+      "sketch": 1,
+      "profiles": {
+        "type": "all"
+      },
+      "extent": {
+        "distance": "width / 2",
+        "direction": "positive"
+      },
+      "operation": "new_body"
+    },
+    {
+      "id": 3,
+      "name": "Fillet1",
+      "suppressed": false,
+      "type": "fillet",
+      "edges": [
+        [
+          0.0,
+          0.0,
+          10.0
+        ]
+      ],
+      "radius": "3"
+    },
+    {
+      "id": 4,
+      "name": "Sketch2",
+      "suppressed": false,
+      "type": "sketch",
+      "plane": {
+        "type": "origin",
+        "name": "XY"
+      },
+      "sketch": {
+        "points": [
+          {
+            "id": "origin",
+            "pos": [
+              0.0,
+              0.0
+            ],
+            "fixed": true
+          },
+          {
+            "id": "c1.center",
+            "pos": [
+              20.0,
+              15.0
+            ],
+            "fixed": false
+          }
+        ],
+        "curves": [
+          {
+            "id": "c1",
+            "type": "circle",
+            "c": 1,
+            "r": 5.0,
+            "construction": false
+          }
+        ],
+        "constraints": [],
+        "next_id": 2
+      }
+    },
+    {
+      "id": 5,
+      "name": "Extrude2",
+      "suppressed": false,
+      "type": "extrude",
+      "sketch": 4,
+      "profiles": {
+        "type": "all"
+      },
+      "extent": {
+        "distance": "20",
+        "direction": "positive"
+      },
+      "operation": "cut"
+    }
+  ],
+  "next_id": 6
+}
\ No newline at end of file
diff --git a/apps/solvecraft-cli/tests/corpus/m0-revolve-primitives.expected.json b/apps/solvecraft-cli/tests/corpus/m0-revolve-primitives.expected.json
new file mode 100644
index 00000000..3c5e4e11
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/m0-revolve-primitives.expected.json
@@ -0,0 +1,155 @@
+{
+  "bodies": [
+    {
+      "area_mm2": 835.4130709318358,
+      "bbox": {
+        "max": [
+          15.0,
+          15.0,
+          5.0
+        ],
+        "min": [
+          -15.0,
+          0.0,
+          0.0
+        ]
+      },
+      "center_of_mass": [
+        -5.1971813422033816e-8,
+        8.063488509334698,
+        2.500000003353729
+      ],
+      "edges": 12,
+      "face_types": {
+        "cylinder": 2,
+        "plane": 4
+      },
+      "faces": 6,
+      "kernel": {
+        "edges": 28,
+        "faces": 14,
+        "shells": 1,
+        "vertices": 16
+      },
+      "name": "Body1",
+      "vertices": 8,
+      "volume_mm3": 981.8090960455798
+    },
+    {
+      "area_mm2": 693.6702600465544,
+      "bbox": {
+        "max": [
+          40.0,
+          10.0,
+          10.000000000000007
+        ],
+        "min": [
+          30.0,
+          0.0,
+          -2.3775115272352145e-15
+        ]
+      },
+      "center_of_mass": [
+        35.02683928802334,
+        4.999999999290639,
+        4.973160725428021
+      ],
+      "edges": 17,
+      "face_types": {
+        "cylinder": 1,
+        "plane": 7
+      },
+      "faces": 8,
+      "kernel": {
+        "edges": 21,
+        "faces": 9,
+        "shells": 1,
+        "vertices": 14
+      },
+      "name": "Body2",
+      "vertices": 12,
+      "volume_mm3": 869.3724925404262
+    }
+  ],
+  "body_count": 2,
+  "params": [],
+  "sketches": [
+    {
+      "curves": 4,
+      "dof": 8,
+      "id": 1,
+      "name": "Sketch1",
+      "profiles": 1,
+      "status": "solved"
+    }
+  ],
+  "timeline": [
+    {
+      "error": null,
+      "id": 1,
+      "ms": 0.034476,
+      "name": "Sketch1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "Sketch",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 2,
+      "ms": 7.732595999999999,
+      "name": "Revolve1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "RevolveFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 3,
+      "ms": 2.5985959999999997,
+      "name": "Box1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "BoxFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 4,
+      "ms": 1.6926910000000002,
+      "name": "Cylinder1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "CylinderFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 5,
+      "ms": 384.534019,
+      "name": "Combine1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "CombineFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 6,
+      "ms": 150.763588,
+      "name": "Chamfer1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "ChamferFeature",
+      "warning": null
+    }
+  ],
+  "total": {
+    "area_mm2": 1529.0833309783902,
+    "edges": 29,
+    "faces": 14,
+    "vertices": 20,
+    "volume_mm3": 1851.181588586006
+  }
+}
diff --git a/apps/solvecraft-cli/tests/corpus/m0-revolve-primitives.solvecraft b/apps/solvecraft-cli/tests/corpus/m0-revolve-primitives.solvecraft
new file mode 100644
index 00000000..bcfcc0b4
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/m0-revolve-primitives.solvecraft
@@ -0,0 +1,171 @@
+{
+  "format": "solvecraft/1",
+  "name": "Untitled",
+  "units": "mm",
+  "params": [],
+  "features": [
+    {
+      "id": 1,
+      "name": "Sketch1",
+      "suppressed": false,
+      "type": "sketch",
+      "plane": {
+        "type": "origin",
+        "name": "XZ"
+      },
+      "sketch": {
+        "points": [
+          {
+            "id": "origin",
+            "pos": [
+              0.0,
+              0.0
+            ],
+            "fixed": true
+          },
+          {
+            "id": "l1.start",
+            "pos": [
+              10.0,
+              0.0
+            ],
+            "fixed": false
+          },
+          {
+            "id": "l1.end",
+            "pos": [
+              15.0,
+              0.0
+            ],
+            "fixed": false
+          },
+          {
+            "id": "l2.end",
+            "pos": [
+              15.0,
+              5.0
+            ],
+            "fixed": false
+          },
+          {
+            "id": "l3.end",
+            "pos": [
+              10.0,
+              5.0
+            ],
+            "fixed": false
+          }
+        ],
+        "curves": [
+          {
+            "id": "l1",
+            "type": "line",
+            "a": 1,
+            "b": 2,
+            "construction": false
+          },
+          {
+            "id": "l2",
+            "type": "line",
+            "a": 2,
+            "b": 3,
+            "construction": false
+          },
+          {
+            "id": "l3",
+            "type": "line",
+            "a": 3,
+            "b": 4,
+            "construction": false
+          },
+          {
+            "id": "l4",
+            "type": "line",
+            "a": 4,
+            "b": 1,
+            "construction": false
+          }
+        ],
+        "constraints": [],
+        "next_id": 5
+      }
+    },
+    {
+      "id": 2,
+      "name": "Revolve1",
+      "suppressed": false,
+      "type": "revolve",
+      "sketch": 1,
+      "profiles": {
+        "type": "all"
+      },
+      "axis": {
+        "type": "sketch_axis",
+        "axis": "y"
+      },
+      "angle": "180 deg",
+      "operation": "new_body"
+    },
+    {
+      "id": 3,
+      "name": "Box1",
+      "suppressed": false,
+      "type": "box",
+      "corner": [
+        30.0,
+        0.0,
+        0.0
+      ],
+      "length": "10",
+      "width": "10",
+      "height": "10",
+      "operation": "new_body"
+    },
+    {
+      "id": 4,
+      "name": "Cylinder1",
+      "suppressed": false,
+      "type": "cylinder",
+      "base": [
+        35.0,
+        5.0,
+        -5.0
+      ],
+      "axis": [
+        0.0,
+        0.0,
+        1.0
+      ],
+      "radius": "(4) / 2",
+      "height": "20",
+      "operation": "new_body"
+    },
+    {
+      "id": 5,
+      "name": "Combine1",
+      "suppressed": false,
+      "type": "combine",
+      "target": "Body2",
+      "tools": [
+        "Body3"
+      ],
+      "operation": "cut",
+      "keep_tools": false
+    },
+    {
+      "id": 6,
+      "name": "Chamfer1",
+      "suppressed": false,
+      "type": "chamfer",
+      "edges": [
+        [
+          30.0,
+          5.0,
+          10.0
+        ]
+      ],
+      "distance": "1"
+    }
+  ],
+  "next_id": 7
+}
\ No newline at end of file
diff --git a/apps/solvecraft-cli/tests/corpus/modern-path-pattern.expected.json b/apps/solvecraft-cli/tests/corpus/modern-path-pattern.expected.json
new file mode 100644
index 00000000..19a67614
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/modern-path-pattern.expected.json
@@ -0,0 +1,122 @@
+{
+  "bodies": [
+    {
+      "area_mm2": 16463.932136252846,
+      "bbox": {
+        "max": [
+          120.0,
+          60.0,
+          5.0000000000000036
+        ],
+        "min": [
+          0.0,
+          0.0,
+          0.0
+        ]
+      },
+      "center_of_mass": [
+        60.000000010005735,
+        29.965234604788655,
+        2.4999999999999867
+      ],
+      "density_g_cm3": 1.29,
+      "edges": 26,
+      "face_types": {
+        "cylinder": 7,
+        "plane": 6
+      },
+      "faces": 13,
+      "kernel": {
+        "edges": 54,
+        "faces": 20,
+        "shells": 1,
+        "vertices": 36
+      },
+      "mass_g": 45.163625870882676,
+      "material": "Default",
+      "name": "Plate",
+      "vertices": 22,
+      "volume_mm3": 35010.56269060673
+    }
+  ],
+  "body_count": 1,
+  "params": [],
+  "sketches": [
+    {
+      "curves": 4,
+      "dof": 8,
+      "id": 1,
+      "name": "Plate_sketch",
+      "profiles": 1,
+      "status": "solved"
+    },
+    {
+      "curves": 2,
+      "dof": 6,
+      "id": 3,
+      "name": "PathSketch",
+      "profiles": 1,
+      "status": "solved"
+    }
+  ],
+  "timeline": [
+    {
+      "error": null,
+      "id": 1,
+      "ms": 0.093199,
+      "name": "Plate_sketch",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "Sketch",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 2,
+      "ms": 9.166392,
+      "name": "Plate",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "ExtrudeFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 3,
+      "ms": 0.057569999999999996,
+      "name": "PathSketch",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "Sketch",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 4,
+      "ms": 84.237259,
+      "name": "Hole1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "ExtrudeFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 5,
+      "ms": 1093.817516,
+      "name": "PathPattern1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "PathPatternFeature",
+      "warning": null
+    }
+  ],
+  "total": {
+    "area_mm2": 16463.932136252846,
+    "edges": 26,
+    "faces": 13,
+    "mass_g": 45.163625870882676,
+    "vertices": 22,
+    "volume_mm3": 35010.56269060673
+  }
+}
diff --git a/apps/solvecraft-cli/tests/corpus/modern-path-pattern.solvecraft b/apps/solvecraft-cli/tests/corpus/modern-path-pattern.solvecraft
new file mode 100644
index 00000000..f7e882f3
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/modern-path-pattern.solvecraft
@@ -0,0 +1,238 @@
+{
+  "format": "solvecraft/1",
+  "name": "Untitled",
+  "units": "mm",
+  "params": [],
+  "features": [
+    {
+      "id": 1,
+      "name": "Plate_sketch",
+      "suppressed": false,
+      "type": "sketch",
+      "plane": {
+        "type": "origin",
+        "name": "XY"
+      },
+      "sketch": {
+        "points": [
+          {
+            "id": "origin",
+            "pos": [
+              0.0,
+              0.0
+            ],
+            "fixed": true
+          },
+          {
+            "id": "l1.start",
+            "pos": [
+              0.0,
+              0.0
+            ],
+            "fixed": false
+          },
+          {
+            "id": "l1.end",
+            "pos": [
+              120.0,
+              0.0
+            ],
+            "fixed": false
+          },
+          {
+            "id": "l2.end",
+            "pos": [
+              120.0,
+              60.0
+            ],
+            "fixed": false
+          },
+          {
+            "id": "l3.end",
+            "pos": [
+              0.0,
+              60.0
+            ],
+            "fixed": false
+          }
+        ],
+        "curves": [
+          {
+            "id": "l1",
+            "type": "line",
+            "a": 1,
+            "b": 2,
+            "construction": false
+          },
+          {
+            "id": "l2",
+            "type": "line",
+            "a": 2,
+            "b": 3,
+            "construction": false
+          },
+          {
+            "id": "l3",
+            "type": "line",
+            "a": 3,
+            "b": 4,
+            "construction": false
+          },
+          {
+            "id": "l4",
+            "type": "line",
+            "a": 4,
+            "b": 1,
+            "construction": false
+          }
+        ],
+        "constraints": [],
+        "counters": {}
+      }
+    },
+    {
+      "id": 2,
+      "name": "Plate",
+      "suppressed": false,
+      "body_names": [
+        "Plate"
+      ],
+      "param_names": [
+        "d1"
+      ],
+      "type": "extrude",
+      "sketch": 1,
+      "profiles": {
+        "type": "curves",
+        "loops": [
+          [
+            "l1",
+            "l2",
+            "l3",
+            "l4"
+          ]
+        ]
+      },
+      "extent": {
+        "distance": "5",
+        "direction": "positive"
+      },
+      "operation": "new_body"
+    },
+    {
+      "id": 3,
+      "name": "PathSketch",
+      "suppressed": false,
+      "type": "sketch",
+      "plane": {
+        "type": "origin",
+        "name": "XY"
+      },
+      "sketch": {
+        "points": [
+          {
+            "id": "origin",
+            "pos": [
+              0.0,
+              0.0
+            ],
+            "fixed": true
+          },
+          {
+            "id": "a1.center",
+            "pos": [
+              60.0,
+              3.3333333333333335
+            ],
+            "fixed": false
+          },
+          {
+            "id": "a1.start",
+            "pos": [
+              100.0,
+              15.0
+            ],
+            "fixed": false
+          },
+          {
+            "id": "a1.end",
+            "pos": [
+              20.0,
+              15.000000000000002
+            ],
+            "fixed": false
+          }
+        ],
+        "curves": [
+          {
+            "id": "a1",
+            "type": "arc",
+            "c": 1,
+            "a": 2,
+            "b": 3,
+            "construction": false
+          },
+          {
+            "id": "c1",
+            "type": "circle",
+            "c": 2,
+            "r": 3.0,
+            "construction": false
+          }
+        ],
+        "constraints": [],
+        "counters": {}
+      }
+    },
+    {
+      "id": 4,
+      "name": "Hole1",
+      "suppressed": false,
+      "body_names": [
+        "Plate"
+      ],
+      "param_names": [
+        "d2"
+      ],
+      "type": "extrude",
+      "sketch": 3,
+      "profiles": {
+        "type": "curves",
+        "loops": [
+          [
+            "c1"
+          ]
+        ]
+      },
+      "extent": {
+        "distance": "0",
+        "direction": "positive",
+        "through_all": true
+      },
+      "operation": "cut"
+    },
+    {
+      "id": 5,
+      "name": "PathPattern1",
+      "suppressed": false,
+      "param_names": [
+        "d3",
+        "d4"
+      ],
+      "type": "pattern",
+      "features": [
+        "Hole1"
+      ],
+      "pattern": {
+        "type": "path",
+        "path_sketch": 3,
+        "path": [
+          "a1"
+        ],
+        "count": "7",
+        "spacing": "17.875031"
+      }
+    }
+  ],
+  "next_id": 6
+}
\ No newline at end of file
diff --git a/apps/solvecraft-cli/tests/corpus/modern-plastic.expected.json b/apps/solvecraft-cli/tests/corpus/modern-plastic.expected.json
new file mode 100644
index 00000000..407ac07d
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/modern-plastic.expected.json
@@ -0,0 +1,126 @@
+{
+  "bodies": [
+    {
+      "area_mm2": 24280.380636378435,
+      "bbox": {
+        "max": [
+          80.0,
+          50.0,
+          32.0
+        ],
+        "min": [
+          0.0,
+          0.0,
+          0.0
+        ]
+      },
+      "center_of_mass": [
+        39.89510389356416,
+        24.906013036240918,
+        10.936558895792075
+      ],
+      "density_g_cm3": 1.29,
+      "edges": 82,
+      "face_types": {
+        "cone": 1,
+        "cylinder": 1,
+        "plane": 35
+      },
+      "faces": 37,
+      "kernel": {
+        "edges": 90,
+        "faces": 39,
+        "shells": 1,
+        "vertices": 60
+      },
+      "mass_g": 29.716687268283682,
+      "material": "Default",
+      "name": "Body1",
+      "vertices": 56,
+      "volume_mm3": 23036.19168084006
+    }
+  ],
+  "body_count": 1,
+  "params": [
+    {
+      "comment": "",
+      "error": null,
+      "expression": "2 mm",
+      "model": false,
+      "name": "wall",
+      "unit": "mm",
+      "value": 2.0
+    }
+  ],
+  "sketches": [],
+  "timeline": [
+    {
+      "error": null,
+      "id": 1,
+      "ms": 13.671479,
+      "name": "Box1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "BoxFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 2,
+      "ms": 15.729548999999999,
+      "name": "Shell1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "ShellFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 3,
+      "ms": 136.407014,
+      "name": "Lip1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "LipFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 4,
+      "ms": 530.869306,
+      "name": "Boss1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "BossFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 5,
+      "ms": 176.568115,
+      "name": "Rest1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "RestFeature",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 6,
+      "ms": 260.395779,
+      "name": "SnapFit1",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "SnapFitFeature",
+      "warning": null
+    }
+  ],
+  "total": {
+    "area_mm2": 24280.380636378435,
+    "edges": 82,
+    "faces": 37,
+    "mass_g": 29.716687268283682,
+    "vertices": 56,
+    "volume_mm3": 23036.19168084006
+  }
+}
diff --git a/apps/solvecraft-cli/tests/corpus/modern-plastic.solvecraft b/apps/solvecraft-cli/tests/corpus/modern-plastic.solvecraft
new file mode 100644
index 00000000..fc8a96c1
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/modern-plastic.solvecraft
@@ -0,0 +1,158 @@
+{
+  "format": "solvecraft/1",
+  "name": "Untitled",
+  "units": "mm",
+  "params": [
+    {
+      "name": "wall",
+      "expr": "2 mm",
+      "unit": "mm",
+      "model": false
+    }
+  ],
+  "features": [
+    {
+      "id": 1,
+      "name": "Box1",
+      "suppressed": false,
+      "param_names": [
+        "d1",
+        "d2",
+        "d3"
+      ],
+      "type": "box",
+      "corner": [
+        0.0,
+        0.0,
+        0.0
+      ],
+      "length": "80",
+      "width": "50",
+      "height": "30",
+      "operation": "new_body"
+    },
+    {
+      "id": 2,
+      "name": "Shell1",
+      "suppressed": false,
+      "param_names": [
+        "d4"
+      ],
+      "type": "shell",
+      "faces": [
+        [
+          40.0,
+          25.0,
+          30.0
+        ]
+      ],
+      "thickness": "wall"
+    },
+    {
+      "id": 3,
+      "name": "Lip1",
+      "suppressed": false,
+      "param_names": [
+        "d5",
+        "d6"
+      ],
+      "type": "lip",
+      "face": [
+        1.0,
+        25.0,
+        30.0
+      ],
+      "width": "1",
+      "height": "2"
+    },
+    {
+      "id": 4,
+      "name": "Boss1",
+      "suppressed": false,
+      "param_names": [
+        "d7",
+        "d8",
+        "d9",
+        "d10"
+      ],
+      "type": "boss",
+      "position": [
+        20.0,
+        20.0,
+        2.0
+      ],
+      "direction": [
+        0.0,
+        0.0,
+        1.0
+      ],
+      "diameter": "6",
+      "height": "10",
+      "hole_diameter": "2.5",
+      "draft": "1 deg"
+    },
+    {
+      "id": 5,
+      "name": "Rest1",
+      "suppressed": false,
+      "param_names": [
+        "d11",
+        "d12",
+        "d13",
+        "d14"
+      ],
+      "type": "rest",
+      "position": [
+        60.0,
+        30.0,
+        2.0
+      ],
+      "direction": [
+        0.0,
+        0.0,
+        1.0
+      ],
+      "width": "8",
+      "length": "12",
+      "height": "3",
+      "thickness": "1"
+    },
+    {
+      "id": 6,
+      "name": "SnapFit1",
+      "suppressed": false,
+      "param_names": [
+        "d15",
+        "d16",
+        "d17",
+        "d18",
+        "d19"
+      ],
+      "type": "snap_fit",
+      "position": [
+        40.0,
+        12.0,
+        2.0
+      ],
+      "direction": [
+        0.0,
+        0.0,
+        1.0
+      ],
+      "hook": [
+        0.0,
+        1.0,
+        0.0
+      ],
+      "length": "12",
+      "thickness": "1.5",
+      "width": "6",
+      "catch_depth": "1",
+      "catch_length": "2"
+    }
+  ],
+  "next_id": 7,
+  "plastic": {
+    "active": "ABS (1.5mm)"
+  }
+}
\ No newline at end of file
diff --git a/apps/solvecraft-cli/tests/corpus/modern-sheet-metal.expected.json b/apps/solvecraft-cli/tests/corpus/modern-sheet-metal.expected.json
new file mode 100644
index 00000000..52a67a4b
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/modern-sheet-metal.expected.json
@@ -0,0 +1,85 @@
+{
+  "bodies": [
+    {
+      "area_mm2": 10411.967792188118,
+      "bbox": {
+        "max": [
+          70.0,
+          50.00000000000002,
+          32.500000000000014
+        ],
+        "min": [
+          0.0,
+          -4.440892098500626e-14,
+          -5.329070518200751e-15
+        ]
+      },
+      "center_of_mass": [
+        36.03765771659564,
+        24.999999999999982,
+        15.08756759282672
+      ],
+      "density_g_cm3": 1.29,
+      "edges": 44,
+      "face_types": {
+        "cylinder": 4,
+        "plane": 10
+      },
+      "faces": 22,
+      "kernel": {
+        "edges": 44,
+        "faces": 22,
+        "shells": 1,
+        "vertices": 24
+      },
+      "mass_g": 15.605746095907175,
+      "material": "Default",
+      "name": "Body1",
+      "sheet_metal": true,
+      "vertices": 24,
+      "volume_mm3": 12097.477593726493
+    }
+  ],
+  "body_count": 1,
+  "params": [],
+  "sketches": [
+    {
+      "curves": 3,
+      "dof": 8,
+      "id": 1,
+      "name": "Contour",
+      "profiles": 0,
+      "status": "solved"
+    }
+  ],
+  "timeline": [
+    {
+      "error": null,
+      "id": 1,
+      "ms": 0.074984,
+      "name": "Contour",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "Sketch",
+      "warning": null
+    },
+    {
+      "error": null,
+      "id": 2,
+      "ms": 37.187197,
+      "name": "ContourFlange",
+      "rolled_back": false,
+      "suppressed": false,
+      "type": "ContourFlangeFeature",
+      "warning": null
+    }
+  ],
+  "total": {
+    "area_mm2": 10411.967792188118,
+    "edges": 44,
+    "faces": 22,
+    "mass_g": 15.605746095907175,
+    "vertices": 24,
+    "volume_mm3": 12097.477593726493
+  }
+}
diff --git a/apps/solvecraft-cli/tests/corpus/modern-sheet-metal.solvecraft b/apps/solvecraft-cli/tests/corpus/modern-sheet-metal.solvecraft
new file mode 100644
index 00000000..b9611c82
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/modern-sheet-metal.solvecraft
@@ -0,0 +1,120 @@
+{
+  "format": "solvecraft/1",
+  "name": "Untitled",
+  "units": "mm",
+  "params": [],
+  "features": [
+    {
+      "id": 1,
+      "name": "Contour",
+      "suppressed": false,
+      "type": "sketch",
+      "plane": {
+        "type": "custom",
+        "plane": {
+          "origin": [
+            0.0,
+            0.0,
+            0.0
+          ],
+          "x_dir": [
+            1.0,
+            0.0,
+            0.0
+          ],
+          "y_dir": [
+            0.0,
+            0.0,
+            -1.0
+          ]
+        }
+      },
+      "sketch": {
+        "points": [
+          {
+            "id": "origin",
+            "pos": [
+              0.0,
+              0.0
+            ],
+            "fixed": true
+          },
+          {
+            "id": "l1.start",
+            "pos": [
+              0.0,
+              0.0
+            ],
+            "fixed": false
+          },
+          {
+            "id": "l1.end",
+            "pos": [
+              40.0,
+              0.0
+            ],
+            "fixed": false
+          },
+          {
+            "id": "l2.end",
+            "pos": [
+              40.0,
+              -30.0
+            ],
+            "fixed": false
+          },
+          {
+            "id": "l3.end",
+            "pos": [
+              70.0,
+              -30.0
+            ],
+            "fixed": false
+          }
+        ],
+        "curves": [
+          {
+            "id": "l1",
+            "type": "line",
+            "a": 1,
+            "b": 2,
+            "construction": false
+          },
+          {
+            "id": "l2",
+            "type": "line",
+            "a": 2,
+            "b": 3,
+            "construction": false
+          },
+          {
+            "id": "l3",
+            "type": "line",
+            "a": 3,
+            "b": 4,
+            "construction": false
+          }
+        ],
+        "constraints": [],
+        "counters": {}
+      }
+    },
+    {
+      "id": 2,
+      "name": "ContourFlange",
+      "suppressed": false,
+      "param_names": [
+        "d1"
+      ],
+      "type": "sheet_contour",
+      "sketch": 1,
+      "curves": [
+        "l1",
+        "l2",
+        "l3"
+      ],
+      "distance": "50"
+    }
+  ],
+  "next_id": 3
+}
\ No newline at end of file
diff --git a/apps/solvecraft-cli/tests/corpus/scripts/components-arm.json b/apps/solvecraft-cli/tests/corpus/scripts/components-arm.json
new file mode 100644
index 00000000..d3235d00
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/scripts/components-arm.json
@@ -0,0 +1,15 @@
+{"commands": [
+ {"command": "PrimitiveBox", "params": {"length": 10, "width": 10, "height": 10, "body_name": "Base"}},
+ {"command": "FusionCreateNewComponentCommand", "params": {"name": "Arm"}},
+ {"command": "PrimitiveBox", "params": {"corner": [20, 0, 0], "length": 10, "width": 4, "height": 4, "body_name": "ArmBody"}},
+ {"command": "FusionFilletEdgesCommand", "params": {"edges": [[25, 4, 4]], "radius": 1}},
+ {"command": "component.activate", "params": {"component": 0}},
+ {"command": "occurrence.move", "params": {"occurrence": 3, "translate": [0, 50, 0]}},
+ {"command": "occurrence.copy", "params": {"component": "Arm", "translate": [0, 20, 0]}},
+ {"command": "component.paste_new", "params": {"component": "Arm", "translate": [0, -30, 0]}},
+ {"command": "occurrence.ground", "params": {"occurrence": 3}},
+ {"command": "SketchCreate", "params": {"plane": "XY", "name": "S1"}},
+ {"command": "CircleCenterRadius", "params": {"center": [5, 5], "radius": 2}},
+ {"command": "SketchStop", "params": {}},
+ {"command": "Extrude", "params": {"distance": 10, "operation": "cut"}}
+]}
diff --git a/apps/solvecraft-cli/tests/corpus/scripts/joints-hinge.json b/apps/solvecraft-cli/tests/corpus/scripts/joints-hinge.json
new file mode 100644
index 00000000..37467809
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/scripts/joints-hinge.json
@@ -0,0 +1,14 @@
+{"commands": [
+ {"command": "ChangeParameterCommand", "params": {"name": "open_angle", "expression": "90 deg"}},
+ {"command": "FusionCreateNewComponentCommand", "params": {"name": "LeafA"}},
+ {"command": "PrimitiveBox", "params": {"length": 40, "width": 30, "height": 3, "corner": [0, 0, 0]}},
+ {"command": "PrimitiveCylinder", "params": {"base": [0, 33, 4], "axis": [1, 0, 0], "radius": 4, "height": 40, "operation": "new"}},
+ {"command": "component.activate", "params": {"component": "root"}},
+ {"command": "FusionCreateNewComponentCommand", "params": {"name": "LeafB"}},
+ {"command": "PrimitiveBox", "params": {"length": 40, "width": 30, "height": 3, "corner": [0, 0, 0]}},
+ {"command": "PrimitiveCylinder", "params": {"base": [0, 33, 4], "axis": [1, 0, 0], "radius": 4, "height": 40, "operation": "new"}},
+ {"command": "component.activate", "params": {"component": "root"}},
+ {"command": "occurrence.ground", "params": {"occurrence": 2, "grounded": true}},
+ {"command": "JointAssembleCmdNew", "params": {"type": "revolute", "a": {"occurrence": "LeafA", "circle": [1, 37, 4]}, "b": {"occurrence": "LeafB", "circle": [1, 37, 4]}, "name": "Hinge"}},
+ {"command": "FusionMoveJointsCommand", "params": {"joint": "Hinge", "value": "open_angle"}}
+]}
diff --git a/apps/solvecraft-cli/tests/corpus/scripts/m0-box-fillet-hole.json b/apps/solvecraft-cli/tests/corpus/scripts/m0-box-fillet-hole.json
new file mode 100644
index 00000000..281834c1
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/scripts/m0-box-fillet-hole.json
@@ -0,0 +1,12 @@
+{"commands": [
+ {"command": "ChangeParameterCommand", "params": {"name": "width", "expression": "40 mm"}},
+ {"command": "SketchCreate", "params": {"plane": "XY"}},
+ {"command": "ShapeRectangleTwoPoint", "params": {"p0": [0, 0], "p1": [40, 30]}},
+ {"command": "SketchStop", "params": {}},
+ {"command": "Extrude", "params": {"distance": "width / 2"}},
+ {"command": "FusionFilletEdgesCommand", "params": {"edges": [[0, 0, 10]], "radius": 3}},
+ {"command": "SketchCreate", "params": {"plane": "XY"}},
+ {"command": "CircleCenterRadius", "params": {"center": [20, 15], "radius": 5}},
+ {"command": "SketchStop", "params": {}},
+ {"command": "Extrude", "params": {"distance": 20, "operation": "cut"}}
+]}
diff --git a/apps/solvecraft-cli/tests/corpus/scripts/m0-revolve-primitives.json b/apps/solvecraft-cli/tests/corpus/scripts/m0-revolve-primitives.json
new file mode 100644
index 00000000..56fd5c90
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/scripts/m0-revolve-primitives.json
@@ -0,0 +1,11 @@
+{"commands": [
+ {"command": "SketchCreate", "params": {"plane": "XZ"}},
+ {"command": "DrawPolyline", "params": {"points": [[10, 0], [15, 0], [15, 5], [10, 5]], "closed": true}},
+ {"command": "SketchStop", "params": {}},
+ {"command": "Revolve", "params": {"axis": "y"}},
+ {"command": "PrimitiveBox", "params": {"length": 10, "width": 10, "height": 10, "corner": [30, 0, 0]}},
+ {"command": "PrimitiveCylinder", "params": {"diameter": 4, "height": 20, "base": [35, 5, -5]}},
+ {"command": "FusionCombineCommand", "params": {"target": "Body2", "tools": ["Body3"], "operation": "cut"}},
+ {"command": "FusionChamferCommand", "params": {"edges": [[30, 5, 10]], "distance": 1}},
+ {"command": "timeline.edit", "params": {"feature": "Revolve1", "set": {"angle": "180 deg"}}}
+]}
diff --git a/apps/solvecraft-cli/tests/corpus/scripts/modern-path-pattern.json b/apps/solvecraft-cli/tests/corpus/scripts/modern-path-pattern.json
new file mode 100644
index 00000000..fbbfdb82
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/scripts/modern-path-pattern.json
@@ -0,0 +1,197 @@
+{
+  "commands": [
+    {
+      "command": "SketchCreate",
+      "params": {
+        "name": "Plate_sketch",
+        "plane": "XY"
+      }
+    },
+    {
+      "command": "DrawPolyline",
+      "params": {
+        "construction": false,
+        "ids": [
+          "l1"
+        ],
+        "points": [
+          [
+            0,
+            0
+          ],
+          [
+            120,
+            0
+          ]
+        ]
+      }
+    },
+    {
+      "command": "DrawPolyline",
+      "params": {
+        "construction": false,
+        "ids": [
+          "l2"
+        ],
+        "points": [
+          "l1.end",
+          [
+            120,
+            60
+          ]
+        ]
+      }
+    },
+    {
+      "command": "DrawPolyline",
+      "params": {
+        "construction": false,
+        "ids": [
+          "l3"
+        ],
+        "points": [
+          "l2.end",
+          [
+            0,
+            60
+          ]
+        ]
+      }
+    },
+    {
+      "command": "DrawPolyline",
+      "params": {
+        "construction": false,
+        "ids": [
+          "l4"
+        ],
+        "points": [
+          "l3.end",
+          "l1.start"
+        ]
+      }
+    },
+    {
+      "command": "SketchStop",
+      "params": {}
+    },
+    {
+      "command": "Extrude",
+      "params": {
+        "body_names": [
+          "Plate"
+        ],
+        "direction": "positive",
+        "distance": 5,
+        "name": "Plate",
+        "operation": "new",
+        "profiles": [
+          {
+            "area_mm2": 7200.0,
+            "centroid_sketch": [
+              60.0,
+              30.0
+            ],
+            "loops": [
+              {
+                "curves": [
+                  "l1",
+                  "l2",
+                  "l3",
+                  "l4"
+                ],
+                "outer": true
+              }
+            ],
+            "sketch": "Plate_sketch"
+          }
+        ],
+        "sketch": "Plate_sketch"
+      }
+    },
+    {
+      "command": "SketchCreate",
+      "params": {
+        "name": "PathSketch",
+        "plane": "XY"
+      }
+    },
+    {
+      "command": "ArcThreePoint",
+      "params": {
+        "end": [
+          20,
+          15
+        ],
+        "id": "a1",
+        "start": [
+          100,
+          15
+        ],
+        "through": [
+          60,
+          45
+        ]
+      }
+    },
+    {
+      "command": "CircleCenterRadius",
+      "params": {
+        "center": "a1.start",
+        "construction": false,
+        "id": "c1",
+        "radius": 3
+      }
+    },
+    {
+      "command": "SketchStop",
+      "params": {}
+    },
+    {
+      "command": "Extrude",
+      "params": {
+        "body_names": [
+          "Plate"
+        ],
+        "direction": "positive",
+        "name": "Hole1",
+        "operation": "cut",
+        "profiles": [
+          {
+            "area_mm2": 28.274334,
+            "centroid_sketch": [
+              100.0,
+              15.0
+            ],
+            "loops": [
+              {
+                "curves": [
+                  "c1"
+                ],
+                "outer": true
+              }
+            ],
+            "sketch": "PathSketch"
+          }
+        ],
+        "sketch": "PathSketch",
+        "through_all": true
+      }
+    },
+    {
+      "command": "PatternOnPath",
+      "params": {
+        "count": 7,
+        "features": [
+          "Hole1"
+        ],
+        "name": "PathPattern1",
+        "path": [
+          "a1"
+        ],
+        "path_sketch": "PathSketch",
+        "spacing": 17.875031
+      }
+    }
+  ]
+}
diff --git a/apps/solvecraft-cli/tests/corpus/scripts/modern-plastic.json b/apps/solvecraft-cli/tests/corpus/scripts/modern-plastic.json
new file mode 100644
index 00000000..08edf91d
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/scripts/modern-plastic.json
@@ -0,0 +1,10 @@
+{"commands": [
+ {"command": "ChangeParameterCommand", "params": {"name": "wall", "expression": "2 mm"}},
+ {"command": "PrimitiveBox", "params": {"length": 80, "width": 50, "height": 30}},
+ {"command": "FusionShellBodyCommand", "params": {"faces": [[40, 25, 30]], "thickness": "wall"}},
+ {"command": "FusionLipCommand", "params": {"face": [1, 25, 30], "width": 1, "height": 2}},
+ {"command": "FusionBossCommand", "params": {"position": [20, 20, 2], "diameter": 6, "height": 10, "hole_diameter": 2.5, "draft": "1 deg"}},
+ {"command": "FusionRestCommand", "params": {"position": [60, 30, 2], "width": 8, "length": 12, "height": 3, "thickness": 1}},
+ {"command": "FusionSnapFitCommand", "params": {"position": [40, 12, 2], "direction": [0, 0, 1], "hook": [0, 1, 0], "length": 12, "thickness": 1.5, "width": 6, "catch_depth": 1, "catch_length": 2}},
+ {"command": "FusionManagePlasticRuleCommand", "params": {"name": "ABS (1.5mm)", "active": true}}
+]}
diff --git a/apps/solvecraft-cli/tests/corpus/scripts/modern-sheet-metal.json b/apps/solvecraft-cli/tests/corpus/scripts/modern-sheet-metal.json
new file mode 100644
index 00000000..1a1af3d1
--- /dev/null
+++ b/apps/solvecraft-cli/tests/corpus/scripts/modern-sheet-metal.json
@@ -0,0 +1,96 @@
+{
+  "commands": [
+    {
+      "command": "SketchCreate",
+      "params": {
+        "name": "Contour",
+        "plane": {
+          "origin": [
+            0.0,
+            0.0,
+            0.0
+          ],
+          "x_dir": [
+            1.0,
+            0.0,
+            0.0
+          ],
+          "y_dir": [
+            0.0,
+            0.0,
+            -1.0
+          ]
+        }
+      }
+    },
+    {
+      "command": "DrawPolyline",
+      "params": {
+        "construction": false,
+        "ids": [
+          "l1"
+        ],
+        "points": [
+          [
+            0.0,
+            0.0
+          ],
+          [
+            40.0,
+            0.0
+          ]
+        ]
+      }
+    },
+    {
+      "command": "DrawPolyline",
+      "params": {
+        "construction": false,
+        "ids": [
+          "l2"
+        ],
+        "points": [
+          "l1.end",
+          [
+            40.0,
+            -30.0
+          ]
+        ]
+      }
+    },
+    {
+      "command": "DrawPolyline",
+      "params": {
+        "construction": false,
+        "ids": [
+          "l3"
+        ],
+        "points": [
+          "l2.end",
+          [
+            70.0,
+            -30.0
+          ]
+        ]
+      }
+    },
+    {
+      "command": "SketchStop",
+      "params": {}
+    },
+    {
+      "command": "FusionSheetMetalFlangeCommand",
+      "params": {
+        "curves": [
+          "l1",
+          "l2",
+          "l3"
+        ],
+        "distance": 50,
+        "name": "ContourFlange",
+        "sketch": "Contour",
+        "type": "contour"
+      }
+    }
+  ]
+}
diff --git a/apps/solvecraft-cli/tests/design_corpus.rs b/apps/solvecraft-cli/tests/design_corpus.rs
new file mode 100644
index 00000000..2a904dc7
--- /dev/null
+++ b/apps/solvecraft-cli/tests/design_corpus.rs
@@ -0,0 +1,211 @@
+//! Designs saved by older SolveCraft builds (tests/corpus, see its README) open and evaluate as
+//! they did when they were saved; damaged and hostile design files never panic.
+
+use std::path::{Path, PathBuf};
+
+use serde_json::{Value, json};
+use solvecraft_engine::Session;
+
+fn corpus() -> Vec<PathBuf> {
+    let dir = Path::new(env!("CARGO_MANIFEST_DIR")).join("tests/corpus");
+    let mut v: Vec<PathBuf> =
+        std::fs::read_dir(&dir).unwrap().flatten().map(|e| e.path()).filter(|p| p.extension().is_some_and(|x| x == "solvecraft")).collect();
+    v.sort();
+    assert!(v.len() >= 7, "corpus files in {}", dir.display());
+    v
+}
+
+fn open(path: &Path) -> Session {
+    let mut s = Session::default();
+    s.execute("doc.open", &json!({"path": path.to_string_lossy()})).unwrap_or_else(|e| panic!("{}: {e}", path.display()));
+    s
+}
+
+/// Differences that are deliberate behaviour changes made before the file format had versions
+/// (no migration can tell those files apart): (file, check, why).
+const KNOWN: [(&str, &str, &str); 2] = [
+    (
+        "m0-revolve-primitives",
+        "Body1 bbox",
+        "partial revolves turn toward the sketch normal since ac43365 (as Fusion's do); M0 turned them the other way",
+    ),
+    ("components-arm", "body_count", "Measure counted only the root component's bodies then; it measures every placed body now"),
+];
+
+fn known(file: &str, check: &str) -> bool {
+    KNOWN.iter().any(|(f, c, _)| *f == file && *c == check)
+}
+
+/// Volumes and areas then came from coarser tessellation (and curved booleans and fillets have
+/// become exact since): the same part within this relative tolerance (the oracle's).
+const REL: f64 = 1e-3;
+
+fn close(a: f64, b: f64, rel: f64) -> bool {
+    (a - b).abs() <= rel * b.abs().max(1.0)
+}
+
+#[test]
+fn old_designs_open_and_evaluate_as_saved() {
+    let mut problems = Vec::new();
+    for p in corpus() {
+        let name = p.file_stem().unwrap_or_default().to_string_lossy().to_string();
+        let want: Value = serde_json::from_slice(&std::fs::read(p.with_extension("expected.json")).unwrap()).unwrap();
+        let mut s = open(&p);
+        for r in &s.model.results {
+            if let Some(e) = &r.error {
+                problems.push(format!("{name}: feature {}: {e}", r.id));
+            }
+        }
+        assert_eq!(s.doc.format, solvecraft_engine::doc::format::format_string(solvecraft_engine::doc::format::FORMAT), "{name}: upgraded");
+        let got = s.execute("MeasureCommand", &json!({})).unwrap();
+        if got["body_count"] != want["body_count"] && !known(&name, "body_count") {
+            problems.push(format!("{name}: {} bodies, saved with {}", got["body_count"], want["body_count"]));
+        }
+        for w in want["bodies"].as_array().into_iter().flatten() {
+            let bname = w["name"].as_str().unwrap_or_default();
+            let Some(g) = got["bodies"].as_array().into_iter().flatten().find(|g| g["name"] == w["name"]) else {
+                problems.push(format!("{name}: body {bname} missing"));
+                continue;
+            };
+            for k in ["volume_mm3", "area_mm2"] {
+                let (a, b) = (g[k].as_f64().unwrap_or(f64::NAN), w[k].as_f64().unwrap_or(f64::NAN));
+                if !close(a, b, REL) {
+                    problems.push(format!("{name}: {bname} {k} {a} (saved {b})"));
+                }
+            }
+            if known(&name, &format!("{bname} bbox")) {
+                continue;
+            }
+            for (end, i) in [("min", 0), ("min", 1), ("min", 2), ("max", 0), ("max", 1), ("max", 2)] {
+                let (a, b) = (g["bbox"][end][i].as_f64().unwrap_or(f64::NAN), w["bbox"][end][i].as_f64().unwrap_or(f64::NAN));
+                if (a - b).abs() > 1e-3 * b.abs().max(1.0) {
+                    problems.push(format!("{name}: {bname} bbox {end}[{i}] {a} (saved {b})"));
+                }
+            }
+        }
+        // Saved again, it reads back the same.
+        let again = solvecraft_engine::doc::Document::from_json(&s.doc.to_json()).unwrap();
+        assert_eq!(again, *s.doc, "{name}: round trip");
+    }
+    assert!(problems.is_empty(), "{}", problems.join("\n"));
+}
+
+/// A small deterministic generator (xorshift).
+struct Rng(u64);
+impl Rng {
+    fn next(&mut self) -> u64 {
+        self.0 ^= self.0 << 13;
+        self.0 ^= self.0 >> 7;
+        self.0 ^= self.0 << 17;
+        self.0
+    }
+    fn below(&mut self, n: usize) -> usize {
+        (self.next() % n.max(1) as u64) as usize
+    }
+}
+
+const HOSTILE: [&str; 14] =
+    ["0", "-1", "1e308", "-1e308", "1e9", "4294967297", "\"\"", "\"1/0\"", "\"((((1\"", "null", "true", "[]", "{}", "\"nope\""];
+
+/// Every JSON value in a document, as a path of keys and indices.
+fn paths(v: &Value, at: &mut Vec<Value>, out: &mut Vec<Vec<Value>>) {
+    out.push(at.clone());
+    match v {
+        Value::Object(m) => {
+            for (k, x) in m {
+                at.push(json!(k));
+                paths(x, at, out);
+                at.pop();
+            }
+        }
+        Value::Array(a) => {
+            for (i, x) in a.iter().enumerate() {
+                at.push(json!(i));
+                paths(x, at, out);
+                at.pop();
+            }
+        }
+        _ => {}
+    }
+}
+
+fn at_mut<'a>(v: &'a mut Value, path: &[Value]) -> Option<&'a mut Value> {
+    let mut cur = v;
+    for k in path {
+        cur = match k {
+            Value::String(s) => cur.get_mut(s.as_str())?,
+            Value::Number(n) => cur.get_mut(n.as_u64()? as usize)?,
+            _ => return None,
+        };
+    }
+    Some(cur)
+}
+
+/// Open a file's bytes as File → Open does and evaluate them; any panic is a failure.
+fn try_bytes(bytes: &[u8]) {
+    if let Ok(doc) = solvecraft_engine::io::read_design(bytes) {
+        let mut s = Session::new(doc);
+        let _ = s.execute("MeasureCommand", &json!({}));
+        let _ = s.execute("document.inspect", &json!({}));
+    }
+}
+
+#[test]
+fn damaged_and_hostile_design_files_never_panic() {
+    let mut rng = Rng(0x5eed_cafe_f00d_d00d);
+    let mut failures = Vec::new();
+    for p in corpus() {
+        let name = p.file_name().unwrap_or_default().to_string_lossy().to_string();
+        let bytes = std::fs::read(&p).unwrap();
+        let doc: Value = serde_json::from_slice(&bytes).unwrap();
+        let mut all = Vec::new();
+        paths(&doc, &mut Vec::new(), &mut all);
+        let mut cases: Vec<(String, Vec<u8>)> = Vec::new();
+        // Truncated and bit-flipped files.
+        for _ in 0..8 {
+            let cut = rng.below(bytes.len());
+            cases.push((format!("truncated at {cut}"), bytes[..cut].to_vec()));
+            let mut b = bytes.clone();
+            let i = rng.below(b.len());
+            b[i] ^= 1 << rng.below(8);
+            cases.push((format!("bit flip at {i}"), b));
+        }
+        // Values replaced by hostile ones, and keys removed.
+        for _ in 0..25 {
+            let path = &all[rng.below(all.len())];
+            let mut v = doc.clone();
+            let h = HOSTILE[rng.below(HOSTILE.len())];
+            if let Some(slot) = at_mut(&mut v, path) {
+                *slot = serde_json::from_str(h).unwrap();
+            }
+            cases.push((format!("{path:?} = {h}"), v.to_string().into_bytes()));
+            let mut v = doc.clone();
+            if let Some((last, parent)) = path.split_last()
+                && let (Some(Value::Object(m)), Value::String(k)) = (at_mut(&mut v, parent), last)
+            {
+                m.remove(k);
+            }
+            cases.push((format!("{path:?} removed"), v.to_string().into_bytes()));
+        }
+        // Features repeated many times; deep nesting; not JSON at all.
+        let mut v = doc.clone();
+        if let Some(Value::Array(fs)) = v.get_mut("features") {
+            let copy = fs.clone();
+            for _ in 0..2 {
+                fs.extend(copy.iter().cloned());
+            }
+        }
+        cases.push(("features repeated".into(), v.to_string().into_bytes()));
+        cases.push(("deep nesting".into(), format!("{}{}", "[".repeat(100_000), "]".repeat(100_000)).into_bytes()));
+        cases.push(("binary".into(), (0..4096u32).map(|i| (i.wrapping_mul(2_654_435_761) >> 24) as u8).collect()));
+        for (what, b) in cases {
+            if std::env::var_os("CORPUS_TRACE").is_some() {
+                eprintln!("{name}: {what}");
+            }
+            if std::panic::catch_unwind(|| try_bytes(&b)).is_err() {
+                failures.push(format!("{name}: {what}"));
+            }
+        }
+    }
+    assert!(failures.is_empty(), "panics:\n{}", failures.join("\n"));
+}
diff --git a/crates/doc/src/document.rs b/crates/doc/src/document.rs
index 984d299f..b21fc725 100644
--- a/crates/doc/src/document.rs
+++ b/crates/doc/src/document.rs
@@ -1113,7 +1113,7 @@ pub struct BrowserGroup {
 }
 
 fn default_format() -> String {
-    "solvecraft/1".into()
+    crate::format::format_string(crate::format::FORMAT)
 }
 fn default_units() -> String {
     "mm".into()
@@ -1214,22 +1214,9 @@ impl Document {
         self.components.iter().find(|c| c.id.to_string() == key || c.name == key).map(|c| c.id)
     }
 
+    /// Read a design file's JSON (any format this build knows; older ones are upgraded).
     pub fn from_json(s: &str) -> Result<Document> {
-        let mut d: Document = serde_json::from_str(s).map_err(|e| DocError::Invalid(format!("document: {e}")))?;
-        if d.features.len() > MAX_FEATURES || d.params.len() > MAX_PARAMS {
-            return Err(DocError::Invalid("document too large".into()));
-        }
-        // Feature inputs get parameter names (designs from before they had them).
-        let ids: Vec<u64> = d.features.iter().map(|f| f.id).collect();
-        for id in ids {
-            d.name_feature_inputs(id);
-        }
-        // Designs from before occurrences: every component gets one, in place.
-        let missing: Vec<(u64, u64)> =
-            d.components.iter().filter(|c| !d.occurrences.iter().any(|o| o.component == c.id)).map(|c| (c.id, c.parent)).collect();
-        for (c, p) in missing {
-            d.add_occurrence(c, p, crate::IDENTITY)?;
-        }
+        let d = crate::format::read(s)?;
         if d.features.len() > MAX_FEATURES || d.params.len() > MAX_PARAMS {
             return Err(DocError::Invalid("document too large".into()));
         }
diff --git a/crates/doc/src/format.rs b/crates/doc/src/format.rs
new file mode 100644
index 00000000..f86c2914
--- /dev/null
+++ b/crates/doc/src/format.rs
@@ -0,0 +1,168 @@
+//! The design file format version and the migrations that bring older files up to date.
+//!
+//! A design file starts with `"format": "solvecraft/N"`. A file of an older format is read and
+//! upgraded step by step (N → N+1 → … → current): JSON-level steps first, for changes in the
+//! file's shape, then document-level steps. A file of a newer format than this build knows is
+//! refused with a message saying so, never guessed at.
+//!
+//! History:
+//! - 1: every design up to 2026-10-08 (format string since M0). Fields added over time all
+//!   have defaults; designs from before feature input names and before occurrences are filled
+//!   in on upgrade.
+//! - 2: the same shape; files say 2 once they have been upgraded, so later readers can tell.
+
+use serde_json::Value;
+
+use crate::{DocError, Document, Result};
+
+/// The format this build writes.
+pub const FORMAT: u32 = 2;
+
+pub fn format_string(n: u32) -> String {
+    format!("solvecraft/{n}")
+}
+
+/// The version in a format string (`solvecraft/N`).
+pub fn version_of(s: &str) -> Option<u32> {
+    s.strip_prefix("solvecraft/")?.parse().ok()
+}
+
+/// JSON-level upgrades: entry `i` turns format `i + 1` into `i + 2`.
+type JsonStep = fn(&mut Value) -> Result<()>;
+const JSON_STEPS: [JsonStep; 1] = [|_| Ok(())];
+
+/// Read a design file's JSON, upgrading older formats.
+pub fn read(s: &str) -> Result<Document> {
+    let mut v: Value = serde_json::from_str(s).map_err(|e| DocError::Invalid(format!("not a SolveCraft design: {e}")))?;
+    let Some(obj) = v.as_object() else {
+        return Err(DocError::Invalid("not a SolveCraft design (expected a JSON object)".into()));
+    };
+    let version = match obj.get("format") {
+        None => 1,
+        Some(Value::String(f)) => version_of(f).ok_or_else(|| DocError::Invalid(format!("not a SolveCraft design (format `{f}`)")))?,
+        Some(_) => return Err(DocError::Invalid("not a SolveCraft design (format is not a string)".into())),
+    };
+    if version == 0 {
+        return Err(DocError::Invalid("not a SolveCraft design (format 0)".into()));
+    }
+    if version > FORMAT {
+        return Err(DocError::Invalid(format!(
+            "this design was saved by a newer SolveCraft (file format {version}; this version reads formats up to {FORMAT}): update SolveCraft to open it"
+        )));
+    }
+    check_numbers(&v, 0)?;
+    for step in JSON_STEPS.iter().skip(version as usize - 1).take((FORMAT - version) as usize) {
+        step(&mut v)?;
+    }
+    let mut d: Document = serde_json::from_value(v).map_err(|e| DocError::Invalid(format!("design file: {e}")))?;
+    if d.features.len() > crate::document::MAX_FEATURES
+        || d.params.len() > crate::document::MAX_PARAMS
+        || d.components.len() > crate::document::MAX_FEATURES
+    {
+        return Err(DocError::Invalid("document too large".into()));
+    }
+    for o in &d.occurrences {
+        if !rigid(&o.transform) {
+            return Err(DocError::Invalid(format!("damaged design: occurrence `{}` has an invalid placement", o.name)));
+        }
+    }
+    if version < 2 {
+        v1_to_v2(&mut d)?;
+    }
+    d.format = format_string(FORMAT);
+    Ok(d)
+}
+
+/// Largest coordinate or size a design may hold (mm): a kilometre-scale part is already far
+/// outside what the kernel's tolerances serve.
+const MAX_REAL: f64 = 1e9;
+
+/// Every non-integer number in the file is finite and within ±`MAX_REAL` (a damaged or hostile
+/// file is refused instead of overflowing the geometry later).
+fn check_numbers(v: &Value, depth: usize) -> Result<()> {
+    if depth > 64 {
+        return Err(DocError::Invalid("damaged design: nested too deeply".into()));
+    }
+    match v {
+        Value::Number(n) if !(n.is_u64() || n.is_i64()) => {
+            let x = n.as_f64().unwrap_or(f64::NAN);
+            if !(x.is_finite() && x.abs() <= MAX_REAL) {
+                return Err(DocError::Invalid(format!("damaged design: the number {n} is out of range")));
+            }
+        }
+        Value::Array(a) => a.iter().try_for_each(|x| check_numbers(x, depth + 1))?,
+        Value::Object(m) => m.values().try_for_each(|x| check_numbers(x, depth + 1))?,
+        _ => {}
+    }
+    Ok(())
+}
+
+/// A placement: rotation (orthonormal, not mirrored) and a translation in range.
+fn rigid(m: &crate::Mat) -> bool {
+    let row = |i: usize| m.get(i).copied().unwrap_or_default();
+    let (x, y, z, t) = (row(0), row(1), row(2), row(3));
+    let dot = |a: [f64; 4], b: [f64; 4]| a[0] * b[0] + a[1] * b[1] + a[2] * b[2];
+    let unit = |a: [f64; 4]| (dot(a, a) - 1.0).abs() < 1e-6;
+    let det = x[0] * (y[1] * z[2] - y[2] * z[1]) - x[1] * (y[0] * z[2] - y[2] * z[0]) + x[2] * (y[0] * z[1] - y[1] * z[0]);
+    m.iter().flatten().all(|v| v.is_finite())
+        && unit(x)
+        && unit(y)
+        && unit(z)
+        && dot(x, y).abs() < 1e-6
+        && dot(y, z).abs() < 1e-6
+        && dot(x, z).abs() < 1e-6
+        && det > 0.0
+        && [x[3], y[3], z[3]].iter().all(|v| v.abs() < 1e-9)
+        && (t[3] - 1.0).abs() < 1e-9
+        && t[..3].iter().all(|v| v.abs() <= MAX_REAL)
+}
+
+/// Format 1 files may predate feature input names and occurrences.
+fn v1_to_v2(d: &mut Document) -> Result<()> {
+    let ids: Vec<u64> = d.features.iter().map(|f| f.id).collect();
+    for id in ids {
+        d.name_feature_inputs(id);
+    }
+    let missing: Vec<(u64, u64)> =
+        d.components.iter().filter(|c| !d.occurrences.iter().any(|o| o.component == c.id)).map(|c| (c.id, c.parent)).collect();
+    for (c, p) in missing {
+        d.add_occurrence(c, p, crate::IDENTITY)?;
+    }
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn versions() {
+        assert_eq!(version_of("solvecraft/1"), Some(1));
+        assert_eq!(version_of("solvecraft/x"), None);
+        let d = Document::new("A");
+        assert_eq!(d.format, format_string(FORMAT));
+        let back = read(&d.to_json()).unwrap();
+        assert_eq!(back, d);
+    }
+
+    #[test]
+    fn older_upgraded_newer_refused_others_rejected() {
+        let mut v: Value = serde_json::from_str(&Document::new("A").to_json()).unwrap();
+        v["format"] = Value::from("solvecraft/1");
+        assert_eq!(read(&v.to_string()).unwrap().format, format_string(FORMAT));
+        v.as_object_mut().unwrap().remove("format");
+        assert!(read(&v.to_string()).is_ok(), "a file without a format is format 1");
+        v["format"] = Value::from(format_string(FORMAT + 1));
+        let e = read(&v.to_string()).unwrap_err().to_string();
+        assert!(e.contains("newer SolveCraft"), "{e}");
+        for bad in ["solvecraft/0", "acad/3", "solvecraft/-1", "solvecraft/99999999999999999999"] {
+            v["format"] = Value::from(bad);
+            assert!(read(&v.to_string()).is_err(), "{bad}");
+        }
+        assert!(read("[]").is_err());
+        let mut v: Value = serde_json::from_str(&Document::new("A").to_json()).unwrap();
+        v["huge"] = Value::from(1e300);
+        assert!(read(&v.to_string()).is_err(), "out-of-range numbers anywhere");
+        assert!(read("{\"format\": 2}").is_err());
+    }
+}
diff --git a/crates/doc/src/lib.rs b/crates/doc/src/lib.rs
index c3ec9de3..0e2202ed 100644
--- a/crates/doc/src/lib.rs
+++ b/crates/doc/src/lib.rs
@@ -11,6 +11,7 @@ mod clipboard;
 mod document;
 mod eval;
 pub mod expr;
+pub mod format;
 pub mod joints;
 mod params;
 pub mod plastic;