buzz/perf/THREAD_NAVIGATION.md

Thread navigation: abandon obsolete history, fetch fresh on return

Behavior and scope

Leaving a thread previously left its history request running. A return before that request finished reused its old snapshot. Replies committed while the channel was closed could be newer than that snapshot but older than the returning live subscription's since, so the thread never displayed them. Abandoned queries also kept dispatching serial history pages after navigation.

Consume TanStack Query's existing AbortSignal in both single-root and multi-root thread hooks. Check cancellation before and after each page. The last observer leaving cancels the query; a remaining observer keeps its pagination alive. An already-dispatched Tauri invoke cannot be canceled: its result is discarded, and further pages stop. Returning starts fresh without waiting for the old IPC. No new timers, caches, schedulers, transport contracts, page sizes, or loading UI. Production diff: useThreadReplies.ts, 20 additions / 2 deletions.

Before/after evidence (2026-09-20)

Control thread implementation: 9fff1acca9b357b1209532de3c502e5d402a3484 (and identical at 9e5a9518e7f3fb62cdf14dc735d1092ed5844a85). Control source SHA-256: 353bcf814d462b50ba9459d43dd082b7bb92e1e7e5c58cbb727a5a05478becfe. Candidate source SHA-256: 97b46bc7ba48b237585615554d6d73555dbbd6e82577ef428f62d4b00b8b0cea. Dependency inspected: actual installed @tanstack/query-core 5.100.14, src/query.ts:362-375 (last-observer handling).

Controlled workflow	Before	After
Return while obsolete snapshot remains pending	Reuses old request; latest reply missing	Fresh request completes independently; latest reply present
Leave after dispatching page 1 of a five-page thread	5 history reads	1 history read
Leave multi-root reader after page 1 of two	2 history reads	1 history read
Another reader remains	All pages delivered	All pages delivered
Cancel refresh after live cache update	Replies retained	Replies retained

The six new real-hook tests use QueryClient, RelayClient, channel subscription, and Tauri API adapter with controlled IPC responses. Both return tests explicitly assert that the returning live filter starts at 202 and the missing reply is at 201. Four fail on the control for the expected fresh-fetch / page-count assertions; all six pass on the candidate. Nine existing thread tests pass too, including missing-target retries and cold-fetch target changes. Existing tests emit React act warnings. A first negative-control cleanup leaked a timer after an assertion failure; cleanup now flushes the held response before clearing the client. The final negative control terminates with four failures and two passes.

The new Playwright regression drives the full rendered app: open thread, hold its IPC snapshot, switch channels, commit reply, return, release snapshots, assert reply text in the panel. It fails on the isolated old build because the reply element is absent, and passes on the candidate. It uses the existing mock bridge gate, not new production test hooks. The old source/build directory has separate dependencies and outputs and no shared Git metadata.

Final browser run at 56f20586b6188696fca447f73052f16f6dc4b746, after reverting the cosmetic splash removal: 131 passed, 1 skipped, adding the original boot-splash checks to the 129-test thread/navigation run. Loading UI is retained. The existing skipped case is direct forum thread links in navigation.spec.ts. Desktop lint/format checks and both E2E and production frontend builds passed, with existing style/bundle-size warnings.

Reproduce

Activate repo Hermit, then from desktop/:

node --import ./test-loader.mjs --experimental-strip-types --test \
  src/features/messages/threadNavigationFreshness.test.mjs \
  src/features/messages/useThreadReplies.test.mjs
pnpm test:e2e:smoke thread-navigation-freshness.spec.ts \
  thread-head-stale-edit.spec.ts thread-unread.spec.ts thread-load-failure.spec.ts \
  project-conversation-load-failure.spec.ts huddle-thread-load-failure.spec.ts \
  navigation.spec.ts messaging.spec.ts

For a negative control, copy only the new tests / Playwright registration into an isolated old-code checkout; rebuild its E2E bundle. Verify port 4173 isn't serving another checkout. Do not change a live application or its caches.

Boundaries

This demonstrates missing-message recovery and less obsolete work, not a measured startup/channel-switch latency improvement or a diagnosis of a specific live session. Active long threads still load serially oldest-first. The initial startup subscription workload is unchanged. Transport errors retain existing retry/error UI. The abort primitive matches the existing channel-history path; this work does not establish compatibility on every supported native WebKit. No native launch, live-relay navigation run, or repository-wide just ci has been claimed. Package-wide tests run through the normal push hook, separately from the focused evidence above. Nothing is merged or deployed by these checks.