M12-02B Status

status: done task: define preview source, content, dimensions, MIME, and generator identity updated: 2026-08-17 America/New_York enablingTask: true parityStateChange: false

Scope

The schema binds source bytes and encoded content as separate SHA-256/length/MIME identities. Encoded content additionally binds width, height, RGBA8, explicit sRGB, and alpha mode. Generator identity binds name, Blender version, executable hash, generator script hash, and canonical settings hash. A domain-separated canonical hash covers the complete record.

The locked Blender 5.2 generator re-encodes a real 8x8 PNG with explicit PNG RGBA8, compression, display, view-transform, exposure, and gamma settings. The source and content encodings have different hashes and lengths while a second Blender process confirms decoded pixels are exact.

Evidence

npm --prefix web run test:asset-preview-identity passed 3/3 protocol tests and the locked Blender generator checker.
Two independent generation runs matched the checked-in 513-byte content SHA-256 exactly; the 261-byte source has a different SHA-256, and decoded pixel maximum error is zero.
Source bytes, content bytes, generator settings, dimensions, identity hash, and unknown fields each have fail-closed negative coverage.
Typecheck and git diff --check passed.

Artifact Hashes

protocol: 2a1d877af42424014097c669e9d44c21b27e3171be185320554693cbefcd7438
generator: 753a26be90f7d97828737ebc3a4ab88275a7c655b4f9992406c7c35fba6535ce
checker: 4d8ece1a5440d202f4e79a48f1f26bc75b3fb11a02d821b8ebc5aee14b11e41a
unit suite: 5b7b3ccaf410d627365579fa82bf2b48fed9ef17144aad963cdbd4bb7fbd4b5a
identity golden: 1b1eb8416ce4aa4d83b0dc42b9cb375f1da965e3f0cb9650991289fc619a0a7b
content PNG: ff139c4a1c5d388c78c5168dfd3272e80ea0d1b15b3743e29a38cd908e8c70e7
manifest: 096f125461b963ee2c414f98f6bb00f02034a380a0cc9c43e0d84754324adb17

Next Task

M12-02C: enforce MIME, pixel, byte, and compression-ratio budgets before preview decode.

Rollback

Remove the preview identity protocol, generator/checker, unit suite, M12-02B goldens, package command, error code, and this status entry. Restore M12-02B to pending and nextTask to M12-02B. No parity ledger rollback is required.

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