User raised a backward-compat concern: integer "schema version"
semantically implies a family of coexisting versions with upgrade
paths between them, inviting the forbidden pattern
(feedback_no_legacy_aliases.md, feedback_no_partial_refactor.md).
Replace with a compile-time structural fingerprint:
- ISV[0..2) stores a u64 FNV-1a hash of the slot layout (split across
two f32 lanes preserving raw bits).
- The hash is computed by a const fn over the slot list; any slot
change automatically updates the fingerprint. No human decides
"what version is this now".
- Checkpoint load is fail-fast only. Error message does NOT mention
migration as an option.
- Pre-commit hook rejects any `fn migrate_isv|upgrade_isv` to make
the no-migration rule structurally enforced (landed as part of
Plan 1 Task 5 hook extension).
- StateResetRegistry entry renamed ISV_SCHEMA_VERSION →
ISV_LAYOUT_FINGERPRINT (Task 2's landed code touched in Task 5's
commit per no-partial-refactor).
Updated:
- spec §4.A.2 (fingerprint design + rationale)
- spec §5 landing-order note (fingerprint auto-updates on layout change)
- Plan 1 architecture line
- Plan 1 Task 2 StateResetRegistry test + entry naming
- Plan 1 Task 5 — full rewrite of implementation steps
- Plan 1 exit criteria #6
- Plan 2 pre-plan verification (grep fingerprint constants, not version==0)
- Plan 2 Task 6D.1 (update fingerprint seed, not bump version)
- Plan 2 Task 6D exit criteria #7
- Plan 3 pre-plan verification
- docs/isv-slots.md ISV[0..2) row
No code changed. Plan 1 Task 5 is not yet implemented — this commit
realigns the spec + plans so the implementer subagent works from the
corrected design.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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