GR-004 — a gallery built with one embedding model is meaningless with another.
Cosine similarities across models are garbage but look entirely plausible, so
this fails silently and expensively; every measurement taken against a
mismatched pair would have been quietly wrong.
The stamp is the model basename plus a SHA-256 of its bytes, with embed_dim as
a cheap extra guard. The hash decides and the name explains, because neither
works alone: a name is a promise rather than a fact — models get re-exported in
place under an unchanged filename, which is exactly the case where the weights
differ and nothing else does — while a bare hash mismatch tells an operator
nothing actionable.
Mismatch is fatal in every mode with no bypass. Unstamped only warns, because
unstamped is unknown rather than known-bad, and an error firing on every legacy
gallery trains people to reach for the bypass reflexively. scripts/stamp_gallery.py
binds an existing gallery in place with no re-embedding, so the warning is a
migration step rather than a permanent state; --require-gallery-stamp promotes
it to an error once a site has migrated.
Two gaps found that would have defeated the requirement outright:
- Embedding dumps carried no stamp, so a replay — which has no live embedder —
had nothing to check the gallery against. Dumps now carry embedder_model and
embedder_sha256 as root attributes. Additive; schema_version stays 1. This is
the same gap the dump audit identified independently.
- --merge produced one file holding two embedding spaces, which no later check
can untangle. Merge paths now verify before writing.
The stamp also survives identity_matcher's calibration write-back, which would
otherwise have stripped it on the first analysis run — the check would have
worked exactly once.
Conflicts resolved additively: both branches appended a source to sae_gallery
and to the test target, and both edited the GR-004 register row.
Merged suite: 64 cases, 3199 assertions, passing on CPU with no GPU.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
TRACES: GR-004, VR-001 | SR-001
dtourolleandClaude Opus 5
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