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Enforce session-mirror retention after short-lived visits #1499
Description
Important
Problem — Session-mirror retention is only enforced by a delayed in-page task. Closing a page before that task runs can leave a scope above its cap across repeated short visits. The current test fixture can also leak a cached IndexedDB handle and timer state into other tests.
Approach — Preserve deferred pruning after writes, but ensure a previously over-cap scope receives bounded cleanup after the mirror database is available on a later visit. Add a test-only reset seam that restores module-level mirror state as well as the global IndexedDB override.
Scope — in: mirror-cap enforcement and mirror-test isolation · out: mirror schema migration, retention-policy changes, and session warming
Assumptions — Full-store pruning remains too expensive to perform after every completed save; per-scope behavior must remain independent.
Acceptance Criteria
- Normal completed saves continue to defer full-store pruning rather than scanning the store after every write.
- A scope left above the retention cap by a short-lived prior visit is pruned on a subsequent use without requiring the abandoned timer to fire.
- Cleanup preserves records for other scopes and continues to enforce the existing per-scope retention cap.
- Test setup and teardown restore IndexedDB and reset cached database, pending-save, and pending-prune state so no mirror fixture leaks across test files.
Testing Decisions
Extend the existing mirror unit harness with a reopen-after-short-visit scenario, cross-scope preservation, and sequential-test isolation coverage. Retain the current deferred-prune assertions.
Key Decisions
- Use an amortized cleanup trigger tied to later database availability rather than turning every save into a full-store scan.
- Expose reset capability only to tests; production code retains encapsulated mirror state.
Constraints & Invariants
- Do not change the persisted mirror record format.
- Do not regress debounced write behavior or scope isolation.
- Keep the change independently reviewable from session warming and landing-page work.
Prior Art
The existing session-mirror persistence layer, retention helper, and IndexedDB test harness.
Source
Follow-up to the six CodeRabbit findings attached to #1473; the behavior originated in the current-main reliability recovery delivered by #1472.
Activity