Efficiency playbook: position parts, add joints only when the human asks - Fusion - the Fusion 360 Bridge

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Efficiency playbook: position parts, add joints only when the human asks #34

Merged Released in 1.13.61 on 3 Nov 2026 Approved opened by Drew Owens 2026-11-03

Merges docs/position-dont-joint → master

Drew's rule for Fusion assemblies, written into the efficiency playbook that steers every AI building through the bridge: position parts in place and stop there; add joints only when the human asks.

Why. Joints, rigid groups and motion links are solved again on every compute, and Autodesk lists joint solving as a large-assembly slowdown. Parts placed with their transforms stay put unless someone drags them, so for a static assembly the joints cost time and add nothing. The old wording ("use joints only where motion matters") still invited them.

Change. One paragraph in skills/fusion-design-efficiency/SKILL.md, item 4. No code, ops or schema change: joint_create, regular_joint_create and the rigid group ops are untouched for when a person does ask for motion.

The assembly-instructions planner (adom/assembly-instructions) already works without joints: it orders a positioned-only assembly from what each part seats on, and reads joints only when a design already has them.

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Diff Skip to comments (1)

skills/fusion-design-efficiency/SKILL.md+5−2

@@ -49,8 +49,11 @@ Run it before and after a change, and before calling a build done.      `method: "capture"` gave 9 snapshots and 21 items. 3. **Ground static parts to their parent** (`groundedToParent: true`) once placed. Later position    changes then cannot drift them.-4. **Use joints only where motion matters.** Rigid groups beat many rigid joints. Autodesk lists joint-   solving as a large-assembly slowdown.+4. **Position parts; add joints only when the human asks.** Place every occurrence with its transform+   (the pose at insert, or `occurrence_update`) and stop there. Positioned parts stay put unless+   someone drags them. Joints, rigid groups and motion links are solved again on every compute, and+   Autodesk lists joint solving as a large-assembly slowdown, so add one only for motion or a+   mechanism the human asked to drive. When one is asked for, a rigid group beats many rigid joints.  ## Repeated parts

Reviews

Colby Knox approved · 8d ago

Docs only, reads well.

Comments

Colby Knox · 8d ago

Agree with the default. One addition to item 4: positioned parts don't follow when the part they sit on changes size. So if the assembly is meant to be driven by parameters, mention that and offer joints for those parts, rather than adding them silently or leaving them out silently.

Merging this and adding that sentence on master, so nothing more is needed from you.