[Bug]: Schema registry ignores committed cache within a transaction

[morluto]

Summary

When transaction_identity is set (inside a transaction), the schema registry resolves registrations to the pending set only. If the pending set is empty (first registration in this transaction), a schema already committed in self._registrations is NOT checked, so the schema is re-registered via register_descriptor, producing a redundant write and potentially a different URI.

Evidence

src/jacobian/schema_registry.py L134-141:

        if transaction_identity is None:
            registrations = self._registrations
        else:
            pending = self._pending.get(transaction_identity)
            registrations = pending.registrations if pending is not None else {}
        cached_uri = registrations.get(registration)
        if cached_uri is not None:
            return cached_uri

Root cause

The cache lookup at L139 only checks the active transaction's pending registrations, not the committed _registrations cache. Within a transaction, previously committed schemas are invisible.

Scope

The lookup should fall through to self._registrations when the pending set does not contain the registration, or maintain a merged view of pending + committed.

Source

• fix(schema): preserve schema registry transaction invariants #804 (comment)

Generated with Devin

[morluto]

Triaged as a transaction-view coherence child of #1019. The immediate invariant is that an active schema-registration transaction must read a merged view of committed registrations plus its own pending writes; it must not treat pending state as a replacement for committed state or emit redundant/conflicting descriptors. The complete fix belongs with atomic registration of the structural schema, semantic/model contract, publication policy, and validator identity. Add commit/rollback/retry/concurrent-registration tests that prove one canonical URI and no cache divergence across transaction boundaries.

[morluto]

Canonical owner: #1019. This remains the concrete transaction-view regression: schema registration inside a transaction must resolve against a merged immutable view of committed registrations plus transaction-local additions, with pending values shadowing only when identity-compatible. Re-registering a committed descriptor is unnecessary write churn and can expose URI/identity divergence. The durable complete-contract registry should make this one atomic lookup/registration plan rather than separate committed and pending caches with ad hoc fallthrough.

[morluto]

Closing as superseded by #1513/#1514. The mutable schema registry, cache, state directory, and restart reload path were removed. Current operation schemas are immutable Pydantic model schemas compiled into the built-in catalog, so there is no registry cache that can preserve stale identities.