# Plan: Fix GLB Export Pipeline + Viewer Staleness

## Root Cause Analysis

### Bug 1 — `export_colors` not valid in Blender 5.0 (CRITICAL)
**File**: `render-worker/scripts/export_gltf.py`
`bpy.ops.export_scene.gltf(export_colors=False)` → Blender exits code 1:
`keyword "export_colors" unrecognized`
→ Blender path always fails → always falls back to trimesh → no materials, no sharp edges, faceted mesh.
This is confirmed in every single log entry. Blender has never successfully exported a GLB.

### Bug 2 — `GlbModel` `cloned` ref never resets on URL change (CRITICAL)
**File**: `frontend/src/components/cad/InlineCadViewer.tsx`
`cloned = useRef<THREE.Group | null>(null)` with guard `if (!cloned.current)` only clones once.
When `glbBlobUrl` changes (new GLB generated), React does NOT remount `GlbModel` (same position in tree),
so `cloned.current` still holds the old geometry → old mesh shown forever.
Fix: add `key={glbBlobUrl}` to `<GlbModel>` → forces remount on each new URL.

### Bug 3 — `glbBlobUrl` not cleared between fetches (UX)
**File**: `frontend/src/components/cad/InlineCadViewer.tsx`
When `downloadUrl` changes, cleanup revokes the old blob URL, but `glbBlobUrl` state still holds
the (now revoked) old URL → `GlbModel` tries to render a revoked URL for the duration of the new fetch.
Fix: `setGlbBlobUrl(null)` at the start of the effect before fetching.

### Bug 4 — `staleTime: 30_000` delays detecting new GLB (UX)
**File**: `frontend/src/components/cad/InlineCadViewer.tsx`
After "Generate GLB" the task completes and a new MediaAsset is written to DB,
but the assets query is cached for 30 seconds → `downloadUrl` stays stale → viewer fetches old GLB.
Fix: reduce `staleTime` to `0` so the query always refetches on focus/mount after invalidation.

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## Affected Files

| File | Change | Bug |
|------|--------|-----|
| `render-worker/scripts/export_gltf.py` | Remove invalid `export_colors=False` | 1 |
| `frontend/src/components/cad/InlineCadViewer.tsx` | key={glbBlobUrl} on GlbModel + clear state + staleTime=0 | 2, 3, 4 |

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## Tasks

### Task 1: Fix Blender GLTF export parameters
**File**: `render-worker/scripts/export_gltf.py`
Remove `export_colors=False` from `bpy.ops.export_scene.gltf()` call.
Keep `export_materials="EXPORT"` and `export_image_format="AUTO"` — these are valid in Blender 5.0.
**Acceptance**: Blender exits 0, GLB file is created with materials.
**Requires rebuild**: yes — scripts are COPY'd into container.

### Task 2: Fix GlbModel stale mesh on regeneration
**File**: `frontend/src/components/cad/InlineCadViewer.tsx`
Add `key={glbBlobUrl}` on the `<GlbModel>` element inside the Canvas.
This forces React to unmount+remount GlbModel whenever the blob URL changes,
resetting the `cloned` ref and loading the fresh geometry.
**Acceptance**: After generating a new GLB, the viewer shows the new mesh, not the old one.

### Task 3: Clear stale blob URL before new fetch
**File**: `frontend/src/components/cad/InlineCadViewer.tsx`
At the top of the `useEffect([downloadUrl, token])` body, add `setGlbBlobUrl(null)` before the fetch.
This shows the loading spinner instead of a broken/stale model during re-fetch.
**Acceptance**: After regeneration, viewer shows spinner while new GLB loads.

### Task 4: Remove staleTime delay on asset query
**File**: `frontend/src/components/cad/InlineCadViewer.tsx`
Change `staleTime: 30_000` → `staleTime: 0` on the `gltf_geometry` assets query.
The `qc.invalidateQueries()` call after generating already forces a refetch,
but staleTime=0 also ensures refetch on window focus/tab return.
**Acceptance**: New MediaAsset is picked up within seconds of task completion.

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## Reihenfolge
Task 1 (rebuild) + Tasks 2/3/4 (frontend hot-reload) in parallel.

## Risiken
- `export_materials="EXPORT"` and `export_image_format="AUTO"` may also be invalid in Blender 5.0.
  If so, remove them too and test with bare minimum params (format + apply only).
- If the Schaeffler .blend library materials use custom node groups instead of Principled BSDF,
  the GLTF exporter will still export flat grey — that requires material baking, out of scope here.