# M10-09 Status

status: done
task: Preserve the previous usable material pipeline on compile failure
updated: 2026-08-16 America/New_York

## Scope

`PBRMaterialPipeline` makes material replacement transactional. A successfully
compiled candidate becomes current only after compilation; the previous material
is disposed exactly once after replacement. A blocked candidate is disposed and
the current material remains usable, with the failed report stored as
`shaderCompileFailure` for diagnostics. This does not claim arbitrary Shader Node
support or a WebGPU pipeline.

The Engine Worker independently rejects blocked `setShaderGraph` requests before
the Blender Main transaction, so a failed graph cannot publish a new SceneIR
snapshot in addition to the viewport-side rollback.

## Evidence

- `WEB_TEST_PORT=5525 npm --prefix web run test:shader-pipeline`: Chromium 1/1.
  The test confirms the failed candidate reports `SHADER_NODE_UNSUPPORTED`, keeps
  object identity and the previous compiled report, and that a later successful
  compile replaces the material.
- `npm --prefix web run typecheck` and `npm --prefix web run lint` passed after the
  pipeline helper was added.
- `tests/golden/M10-09/shader-pipeline.json` fixes the rollback invariants.

## Implementation Hashes

- PBR adapter: `8a9cb52c8e7b1481096017cc659d93541c21724c1203d22755e37e1e3c365250`.
- Chromium spec: `e6771f672e885250db199cbf97a0a3866084ab9bb3f2ad25d17f5c53edaa99af`.
- Golden: `5dbb916e512935a76dacde37242b123707897f54ab10d7b99e246f57afbc94ac`.

## Rollback

Remove `PBRMaterialPipeline`, its Chromium test/golden and this status file. Keep
the M10-08 compile key and Engine Worker pre-transaction gate, and restore the M10
count to 8/15.