fix(app): make session navigation stable and fast#33569
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Pull request overview
This PR focuses on improving session navigation paint stability and latency in the app by caching session “placement” (server + directory + root) to avoid cold route work, switching history pagination to single opaque-cursor pages, and adding performance benchmarks to guard the new behavior.
Changes:
- Add a bounded session placement cache and wire it into home/session navigation and titlebar tab metadata to reduce cold navigations.
- Adjust timeline history paging to consume exactly one opaque cursor page per action, with controlled continuation when the user is already at the top.
- Add/expand e2e performance probes + fixtures to measure first/stable paints for navigation milestones and first navigation blank-frame behavior.
Reviewed changes
Copilot reviewed 26 out of 26 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| packages/app/src/utils/session-placement.ts | New bounded placement store used to resolve directory/root quickly across navigations. |
| packages/app/src/utils/session-placement.test.ts | Unit tests for placement aliasing, inheritance, and bounding behavior. |
| packages/app/src/pages/session/timeline/model.ts | Simplifies “load older” to a single page per call (opaque cursor semantics). |
| packages/app/src/pages/session/timeline/model.test.ts | Updates tests to reflect single-page history loading behavior. |
| packages/app/src/pages/session.tsx | Adds request/continuation coordination for history paging and cleanup for scheduled frames. |
| packages/app/src/pages/session-module.ts | Adds shared dynamic import wrapper for session module preloading. |
| packages/app/src/pages/home.tsx | Preloads session module; prefetches top sessions; sets placement before navigation; adds tabs usage. |
| packages/app/src/pages/home-module.ts | Adds shared dynamic import wrapper for home module preloading. |
| packages/app/src/pages/directory-layout.tsx | Inherits placement for child-session navigation to keep destination placement ready. |
| packages/app/src/context/global.tsx | Registers the global sessionPlacement store alongside existing global contexts. |
| packages/app/src/context/directory-sync.ts | Reduces initial message page size to support small-page navigation/pagination strategy. |
| packages/app/src/components/titlebar.tsx | Uses cached placement + local sync data for tab titles before falling back to network; preloads home module. |
| packages/app/src/app.tsx | Switches session-route resolution from query placeholdering to resource + placement cache. |
| packages/app/e2e/utils/mock-server.ts | Introduces opaque cursor tokens for message pagination in e2e mock server. |
| packages/app/e2e/smoke/session-timeline.spec.ts | Makes timeline key sampling robust by collecting currently visible timeline part IDs. |
| packages/app/e2e/performance/unit/timeline-test-helpers.test.ts | Adds unit test for stress-session link builder. |
| packages/app/e2e/performance/unit/navigation-milestones.test.ts | Adds unit test for milestone first/stable paint summarization. |
| packages/app/e2e/performance/unit/first-navigation-metrics.test.ts | Adds unit tests for first-navigation blank-frame/stability summarization. |
| packages/app/e2e/performance/timeline/timeline-test-helpers.ts | Updates stress helpers for server-scoped routes, draft tabs, and fixture paging. |
| packages/app/e2e/performance/timeline/session-timeline-stress.fixture.ts | Extends fixture with child session + tool metadata to exercise child navigation. |
| packages/app/e2e/performance/timeline/navigation-milestones.ts | Adds probe + summarizer for content/tab/home/tab-removed milestone paints. |
| packages/app/e2e/performance/timeline/home-tab-navigation-benchmark.spec.ts | Adds benchmarks for home→session and close-only-tab→home milestone paints. |
| packages/app/e2e/performance/timeline/first-navigation-probe.ts | Adds probe for detecting blank frames during first navigation to destination. |
| packages/app/e2e/performance/timeline/first-navigation-metrics.ts | Adds summarizer for first navigation samples (blank/source/destination). |
| packages/app/e2e/performance/timeline/first-navigation-benchmark.spec.ts | Adds benchmarks for unvisited tab, new-session draft, and child session first-navigation paint. |
| packages/app/e2e/performance/README.md | Documents additional benchmark scenarios covered by the suite. |
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| @@ -0,0 +1,41 @@ | |||
| import { ServerConnection } from "@/context/server" | |||
| } | ||
| const absolute = (path: string) => (current()[0].path.directory + "/" + path).replace("//", "/") | ||
| const initialMessagePageSize = 80 | ||
| const initialMessagePageSize = 2 |
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| const stable = samples.findIndex( | ||
| (sample, index) => matches(sample) && matches(samples[index + 1]!) && matches(samples[index + 2]!), | ||
| ) |
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# Conflicts: # packages/app/src/app.tsx # packages/app/src/pages/home.tsx
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Summary
Performance
Production Chromium, native speed, one worker. Painted-frame benchmarks sample with
requestAnimationFramefollowed bysetTimeout(0). Baseline is currentupstream/devate8610d821; branch is the PR head. First-navigation and home/close values are medians of 3 runs. Cold/hot tab values are medians of 15 trials (3 benchmark repetitions, each containing 5 trials).Windows
macOS
Home And Tab Milestones
Home-to-session records session content and titlebar-tab visibility independently. Closing measures home shell, restored session row, and tab removal.
Visual Stability
Chrome Trace Attribution
Full Chrome Performance traces include V8 sampling and timeline-stack overhead, so these values are reported separately from the native-speed medians above. User Timing marks delimit click, first paint, and stable paint inside each trace.
The remaining traced cost is dominated by final Solid/DOM construction and layout rather than network or Markdown parsing. Review-shell geometry remains immediate; only its internal body is staged after the first session-content paint.
Verification
bun turbo typecheckacross 23 packagesbun run test:unit: 415 passedbun test ./e2e/performance/unit: 15 passedbun run test:e2e: 16 passedupstream/devand rebased branch refsNotes
bun run test:benchdiscovers all navigation scenarios above for future baseline comparisons