Hydration oracle: observer shows no rows after cleanup, restart, and a new write (granular mode) #2334

Summary

A random campaign of live-query-observer-hydration-oracle.property.test.ts found a counterexample in CI. It reproduces on main at a2c3854c3 and at a3c4d0676. It still reproduces after a merge of 9be51e037 (#2333). This report does not establish whether production or the oracle's model is wrong.

Counterexample

CI run: https://github.com/TanStack/db/actions/runs/41516335355/job/125520732865 (PR #2302, which does not change this oracle or the observer).

{ seed: 2087400494, path: "4:0:2:3", endOnFailure: true }
Counterexample: [{"mode":"granular","seed":[],"events":[{"type":"attach"},{"type":"ready"},{"type":"write","key":"b","version":0},{"type":"cleanup"},{"type":"restart"},{"type":"write","key":"b","version":0}]}]
AssertionError: ... "step":5}: expected [] to deeply equal [ [ 'b', +0 ] ]
    at check (tests/live-query-observer-hydration-oracle.property.test.ts:314:51)

The history attaches a granular observer with no hydration seed and marks the Collection ready. It writes row b, cleans the Collection up, restarts it, and writes row b again. After the last write, the model expects the observer view to show b. The view shows no rows.

Reproduce

This property is not in the oracle-config.ts path-replay registry, so the replay environment variables do not select it. Pin the seed in the random campaign (generated histories refine the hydration model with a random or replayed seed): replace oraclePropertyOptions(100) with { seed: 2087400494, path: '4:0:2:3', endOnFailure: true }. Then run from packages/db:

pnpm exec vitest run tests/live-query-observer-hydration-oracle.property.test.ts --coverage.enabled=false --typecheck.enabled=false -t "random or replayed seed"

Next step

Determine which account fails: the observer after a cleanup and restart, or the model's expected rows for a restarted Collection. Keep this trace as a replay of the shared model and comparison. The property's absence from the path-replay registry is a separate coverage-map limit.