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perf(web): reuse work log rows during streaming - #8006

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maria-rcks merged 1 commit into
pingdotgg:mainfrom
Bil0000:t3code/perf-benchmarks-and-improvements
Aug 23, 2026
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perf(web): reuse work log rows during streaming#8006
maria-rcks merged 1 commit into
pingdotgg:mainfrom
Bil0000:t3code/perf-benchmarks-and-improvements

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@Bil0000

@Bil0000 Bil0000 commented Aug 23, 2026 •
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Long threads rebuild their full work log for every streamed activity update. That reparsed unchanged activity payloads, cloned every output row, and changed row identities even when the source activities had not changed.

This change caches each immutable activity's derived work-log entry in a WeakMap, keeps collapse metadata private with a symbol, and returns collapsed entries without a second cloning pass. Unchanged activity rows now keep stable identities across append updates.

Benchmark

  • Scenario: derive 20,000 ordered command activities, append one activity, then derive again.
  • Before median: 163.6 ms.
  • After median: 10.1 ms.
  • Median change: 93.8% less time.
  • Before p95: 275.5 ms.
  • After p95: 22.9 ms.
  • The committed regression requires the append update to finish within 100 ms and checks stable entry identity.

Verification

  • pnpm --filter @t3tools/web typecheck
  • vp lint apps/web/src/session-logic.ts apps/web/src/session-logic.test.ts --report-unused-disable-directives
  • vp fmt --check apps/web/src/session-logic.ts apps/web/src/session-logic.test.ts
  • vp test run src/session-logic.test.ts --project unit (77 tests)
  • vp test run src/components/chat/MessagesTimeline.logic.test.ts src/components/chat/MessagesTimeline.test.tsx --project unit (77 tests)

Note

Memoize DerivedWorkLogEntry via WeakMap to reuse work log rows during streaming

  • Caches the result of toDerivedWorkLogEntry in a module-level WeakMap keyed by activity object, so repeated derivations for the same activity return the same entry instance
  • Moves the collapse key from the string field collapseKey to a symbol-keyed property [workLogCollapseKey], eliminating the final mapping step in deriveWorkLogEntries that previously stripped internal fields
  • Renames activityKind to sourceActivityKind on DerivedWorkLogEntry; updates all readers in toolLifecycleCollapseMapKey, collapseDerivedWorkLogEntries, shouldCollapseToolLifecycleEntries, and deriveToolLifecycleCollapseKey
  • Adds performance tests in session-logic.test.ts verifying identity reuse for unchanged entries and 20k-entry derivation within 100 ms
  • Behavioral Change: DerivedWorkLogEntry no longer exposes activityKind or collapseKey; any external reader of these fields must switch to sourceActivityKind and [workLogCollapseKey]

Macroscope summarized 647e760.

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@github-actions github-actions Bot added vouch:trusted PR author is trusted by repo permissions or the VOUCHED list. size:M 30-99 changed lines (additions + deletions). labels Aug 23, 2026
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Verdict: Skipped

Macroscope did not run approvability analysis for this PR. Macroscope could not determine whether this PR modifies its approvability configuration, so the PR was not approved automatically. A PR that may change the rules that govern approval is never approved automatically.

@maria-rcks
maria-rcks merged commit fa21900 into pingdotgg:main Aug 23, 2026
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github-actions Bot added a commit to omarcresp/t3code-flake that referenced this pull request Aug 23, 2026
@github-actions
nightly: 0.0.34-nightly.20260823.1171
a71d9eb 
## What's Changed
* feat(web): redesign skills in `$` menu and in `/` menu by @extoci in pingdotgg/t3code#8009
* fix(web): restore right panel toggle clicks after closing on desktop by @UtkarshUsername in pingdotgg/t3code#8016
* fix(web): keep server update banners flush with the composer by @t3dotgg in pingdotgg/t3code#8000
* perf(web): reuse work log rows during streaming by @Bil0000 in pingdotgg/t3code#8006
* fix(web): keep provider badge legible in dark themes by @RakshithBhat03 in pingdotgg/t3code#7968


**Full Changelog**: pingdotgg/t3code@v0.0.34-nightly.20260823.1170...v0.0.34-nightly.20260823.1171

Upstream release: https://github.com/pingdotgg/t3code/releases/tag/v0.0.34-nightly.20260823.1171
frankdavidcorona pushed a commit to frankdavidcorona/t3code that referenced this pull request Aug 23, 2026
@Bil0000 @frankdavidcorona
perf(web): reuse work log rows during streaming (pingdotgg#8006)
f80c068
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@Bil0000 @maria-rcks