47 lines
2.2 KiB
Markdown
47 lines
2.2 KiB
Markdown
# M12-02C Status
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status: done
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task: enforce MIME, pixel, byte, and compression-ratio budgets before preview decode
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updated: 2026-08-17 America/New_York
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enablingTask: true
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parityStateChange: false
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## Scope
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The schema 1 pre-decode planner accepts only the M12-02B content identity and an exact
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`ArrayBuffer` payload. It checks the 16 MiB encoded-byte limit before hashing, then binds the
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content SHA-256, declared MIME to the PNG/WebP container header, header dimensions to the identity,
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and dimensions to pixel and RGBA8 decoded-byte budgets. The final gate limits decoded-to-encoded
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compression ratio to 100 before any browser image decoder or decoded allocation is invoked.
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PNG dimensions come only from a valid signature and first IHDR header. WebP dimensions come only
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from a size-bound RIFF/WEBP VP8X, VP8L, or VP8 header. Unsupported headers, content drift, and
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dimension drift fail closed; a rejected input does not affect a following valid preview plan.
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## Evidence
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- `npm --prefix web run test:asset-preview-decode-budget` passed 5/5 M12-02B/C protocol tests.
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- The positive 513-byte Blender-generated PNG plans 64 pixels and 256 decoded RGBA8 bytes without
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calling a decoder.
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- Eight negative cases cover payload hash/length drift, MIME mismatch, dimension mismatch,
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over-width/height and decoded-byte budget, compression ratio, encoded-byte budget, and corrupt
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container signature. The checked-in small preview passes immediately after each rejection.
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- `npm --prefix web run typecheck`, `npm --prefix web run lint`, and `git diff --check` passed.
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## Artifact Hashes
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- decode protocol: `3d1c491af2503a7a6012541ed43400d680f8e666cc12a54db284aeb6ac18ff63`
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- unit suite: `1a65df86d568ae8defd7cd9242f426ac900d92637eb3bed2cbb4a0fae2e86c20`
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- package commands: `8563916637fc3cb29b53432ae9b80d1dcf6269f2f5c092b595e72c6b0ada55ab`
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- manifest: `934b3ca29d905ad2f5c46f35acff4cf4b9ea291c423fb3aad4afe7e9f10e6244`
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## Next Task
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`M12-02D`: commit a catalog preview reference only after its content-addressed payload is durably
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written to OPFS.
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## Rollback
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Remove the preview decode planner, unit suite, M12-02C manifest, package command, and this status
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entry. Restore M12-02C to pending and `nextTask` to M12-02C. No parity ledger rollback is required.
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