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c856f36459
Follow-up to #65890 (router transitions off) and #65898 (structural compare + first-paint budget): profiling the switch path on real 1000+- message sessions with a new CDP harness showed the remaining freeze is NOT markdown rendering — it's a forced-reflow cascade from mount-time layout reads interleaved with style writes across the transcript's layout effects, plus the first-paint budget cut landing too late to stop the full-budget commit. Measured on the two largest local sessions (996 and 1363 messages), main-thread longtask totals per switch: warm 2450ms -> 557ms and 1158ms -> 194ms; first paint 1690ms -> 444ms. Harness: scripts/profile-session-switch.mjs (same CDP family as profile-real-stream.mjs). - use-resize-observer: drop the synchronous initial callback and ride the observer's spec-guaranteed first delivery instead (same frame, after layout, before paint). The sync call ran while the commit's layout was dirty, so every size read in a callback forced a full reflow — with one instance per user bubble (measureClamp read scrollHeight, then WROTE --human-msg-full, re-dirtying layout for the next bubble), the switch commit thrashed for over a second. Inside RO timing the same reads are free. Composer metrics (2x getBoundingClientRect + documentElement style writes) rides the same fix. - Same class, same fix at the remaining call sites profiling surfaced: ExpandableBlock and TerminalOutput (dozens per tool-heavy transcript) now measure/pin via RO initial delivery; the tool-window and thinking-preview pins drop their sync pin() call; the thread timeline's initial active-tick compute joins its existing scroll-time rAF batching so back-to-back transcript updates coalesce. - thread/list: cut the render budget in the RENDER phase (state-from- props adjustment) instead of the post-commit layout effect. The effect-time cut was too late — on a warm switch React first built and committed the full 300-part tree, then re-rendered at 60, then bumped back to 300, so the expensive commit still happened (and on a cold switch the bump rAF usually fired while the transcript was still empty, so the prefetched messages rendered at full budget anyway). The render-phase cut restarts the component before any child renders; a second trigger handles the cold path where messages land later under the same sessionKey. - thread/list: backfill 60 -> 300 inside startTransition so the older turns' markdown+shiki render is interruptible background work instead of a synchronous freeze one frame after the switch paints. Functional Math.max so an urgent "Show earlier" click can't be rebased back down. - composer focus: skip the rAF/timeout focus retries when the element is already focused — focus() runs the full focusing steps (forcing layout) even on the active element, ~585ms per switch on a large dirty DOM. - Replace the tautological render-budget test (it re-declared the constants locally and asserted 60 < 300) with behavior tests of the now-exported buildGroups + firstVisibleGroupIndex. Verification: apps/desktop `npx tsc --noEmit` clean; full `npx vitest run` 210 files / 1763 passed; manual CDP check confirms the deferred backfill commits the full transcript, stays pinned to bottom, and "Show earlier" still pages. |
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| app | ||
| components | ||
| contrib | ||
| fonts | ||
| hooks | ||
| i18n | ||
| lib | ||
| plugins | ||
| sdk | ||
| store | ||
| themes | ||
| types | ||
| global.d.ts | ||
| hermes-parity.test.ts | ||
| hermes-profile-scope.test.ts | ||
| hermes.test.ts | ||
| hermes.ts | ||
| main.tsx | ||
| styles.css | ||
| vite-env.d.ts | ||