[ManuelStaggl]

Fixes the severity-A findings of the full audit (2026-11-12) in the mechanism tool (mechanisms.ts, mechanismTool.ts) and the hinged box template (templates.ts). Built on #353: every number below is measured with that print check (PLA, 0.4 mm nozzle, 45°) on SolidCraft 0.40.1 through the audit harness (tools/audit, cases mechanik-hinge and mechanik-others, 100 scenes), before and after.

Findings

Finding	Before	After
H-02 a failure after the build is reported as "Not built" while the geometry stays	joint refused: 2 → 11 features, Base 4800 → 5333.7 mm³; same call again: 20 features	2 → 2 → 2 features, volumes unchanged; every step since the undo depth read before the build is undone with edit.undo in one batch
N-mechanik-17 SolidCraft's JSON reaches the model raw	Not built: {\n "applied": [], …	Not built: SolidCraft refused joint.as_built: <failed.error>. Everything was taken back.
N-mechanik-3 second hinge with the default name	answer gives the first joint's limits, second joint limits: null, third call builds a third joint	second joint Hinge (2) with its own limits [-67, 145]; the repeated call is refused before anything is built (2 joints, bodies unchanged)
N-mechanik-2 bead of a lid with walls	reach past the box's wall 0.000 mm (also in the template)	0.250 mm in all eight scenes (walls 1.6 / 2 / 10, rooms 56×36 and 20×12, radius 0 / 2 / 8, flat lid, template); no shared volume
T5 level ceiling of the guide's groove	13.932 mm wide at the defaults, check warn 418 mm² (dovetail to plug: 389 mm²)	roof at 45° with a 5 mm ridge where the moving body stands 8.8 mm over the rail's face: ready for both. Lower bodies and wider rails keep the flat ceiling (width 20: 838 mm², 60 × 20: 3058 mm², as before) and the answer says so, with how to lay the part
N-mechanik-6 "printed in one piece without support" for the guide	in the description of every mechanism	gone; description and answer say the two parts print apart
N-mechanik-4 "stand on webs …, so they print without support"	check warn 90 mm² (barrel 6), 121 mm² (8), 619 mm² (40), up to 89.5°; on the template's shells 174 mm²	ready in all four
N-mechanik-5 web drawn to the wall's plane where the wall has ended	web foot 4.64 mm under a 3 mm lid plate, in the air	no web for that body (its lowest point is the barrel again), and the answer names the body and what it needs
T3 template hingedBox without webs	knuckles start 12.0 mm above the bed, check warn 189 mm² up to 87°	ready; still no overhang finding after length 80, height 24; lid closes to the bead's snap at 175.6° as before

Along the way: the pin is flat underneath inside each moving knuckle (a level bridge from one fixed knuckle to the next), which also takes about 25 mm² off every hinge lying on the bed (default hinge 156 → 127 mm²). To keep that bridge at 10 mm or less, a lying hinge on 30 mm of line now gets 5 knuckles by default instead of 3; upright hinges keep the old rule.

Nothing got worse in the other scenes: 78 of 100 are unchanged in body count, shells, smallest gap, shared volume, limits and check; the 22 that differ are the ones above plus lying hinges with less overhang. One scene needs a word: a lid block whose wall ends 6.5 mm under the line (g1-lid-underside-lowest) had a web that just fitted and now gets none, since the full web needs 6.74 mm (check 25 → 50 mm²); the answer says so.

What the assistant is told now

• Description, first sentence: "Build a mechanism between two bodies that exist, with the same gap everywhere; the answer says how it prints."
• Description, hinge: "… printed in place as one piece." and "… carries knuckles that start above the bed on webs at 45° down to their own walls, where the wall reaches about one and a quarter barrel diameters below the line (the answer says where it does not, and what then needs support): add no supports of your own."
• Description, slide: "The two print apart and the moving body is pushed onto the rail from an end. Where the moving body stands high enough over that face (8.8 mm at the defaults; the answer names it) the groove gets a roof at 45° and prints as it stands; otherwise its ceiling is flat and the answer says how to lay the part."
• Hinge answer, all knuckles carried: "All 5 knuckles start above the bed and stand on webs at 45° that run from under the barrel down to their own wall, and the pin is flat underneath where it bridges from knuckle to knuckle, so the hinge prints as it stands, without support."
• Hinge answer, a wall missing: "The knuckles start above the bed, and the 2 of Lid got no web: a web meets its wall 6.743 mm below the line at the most, and there is no wall there. They need support, or a wall that reaches down that far before the hinge is built. The 3 knuckles of Box stand on webs …"
• Hinge answer, long bridge: "The pin bridges 13.9 mm inside each knuckle of Flap, more than prints clean (10 mm): use more knuckles."
• Guide and dovetail answer, roofed: "The two print apart, each with up pointing up, and Stop is then pushed onto the rail from an end. Neither needs support: the rail's flanks and the roof over the groove lean 45°, and the roof's ridge is a bridge of 5 mm."
• Guide and dovetail answer, flat: "… The groove's ceiling is flat and 13.9 mm wide, more than prints as a bridge (10 mm): a roof at 45° over it needs Carriage to stand 8.8 mm high over the face the rail is on, and it stands 6.4 mm. Print Carriage turned over instead, lying on its top with the groove open upwards (set that face as its print face), or make it higher and build this again."
• Refusals: "… Everything was taken back." after a failure past the first step (or "What was begun could not be taken back: undo it before you call again." where SolidCraft's undo depth cannot be read); "the joint "Hinge" already joins Base and Flap as a hinge, and a second hinge between the same two bodies would bind it. Change that one instead: take it back with undo, or delete its features and its joint, then call again".
• MECHANISM_GUIDANCE: "it builds the geometry with the right gaps" (was "the print-in-place geometry").

Contract test expectations changed (not run here)

apps/desktop/e2e/solidcraft.contract.spec.ts, each scene rebuilt in the harness to read the new answer:

• hinged case: 3 knuckles → 5 knuckles; the web sentence → the new one; overhang … 25 mm² → no overhang finding.
• hinged flap: 3 knuckles, barrel 6 mm → 5 knuckles, barrel 6 mm (limits -145° to 67° unchanged).
• flap out of reach: Not built: 3 piece(s) … Everything was taken back; call again with the line moved. → Not built: 5 piece(s) … Everything was taken back.

Checked

• pnpm run typecheck, eslint, vitest run in apps/desktop (720 passed).
• Unit tests per finding in test/mechanism.test.ts and test/templates.test.ts, each with its counter-case.
• Both mechanism cases of the audit harness, all 100 scenes, before and after, plus the scenes of the contract tests and the template after a change of its sizes.

Left open

• The contract tests themselves were not run (no app, no window).
• A hinge lying on the bed still shows the undersides of its barrels in the check (127 mm² at the defaults, T11), and webs at 45° are over the limit of a 40° material.
• B and C findings of the same report that are not part of this change: N-mechanik-7 to -16, -18 to -20, W4 to W9, G1.
• Template hingedBox with wall 3 mm: thin wall 0.26 mm between the knuckles' rooms and the lip's foot, as before this change (108 → 93 mm²).

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