fix(app): eliminate session switch latency — deferRender, Suspense flash, instant rendering#27912
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BYK wants to merge 3 commits into
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fix(app): eliminate session switch latency — deferRender, Suspense flash, instant rendering#27912BYK wants to merge 3 commits into
BYK wants to merge 3 commits into
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…poser timeout Remove the deferRender mechanism that blanked the review panel and composer for one animation frame on every session switch. Remove the 140ms artificial setTimeout in session-composer-region that stacked on top, causing a total ~170ms gap where the composer was invisible. The composer now re-shows after a single rAF yield (~16ms).
The sessionSync createResource was read in JSX ({sessionSync() ?? ""}),
which triggered the nearest <Suspense> boundary (the app-level splash
screen) on every session switch while the sync Promise was pending.
Since the resource returns void (contributes nothing to the DOM), remove
the JSX read entirely — the fetcher still runs reactively from its
source signal regardless.
…session data Widen the messagesReady gate to allow rendering when the session exists in the session list, even before messages have loaded. This eliminates the blank screen on session switch over slow connections. A spinner is shown in the timeline while messages load in the background.
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Issue for this PR
Closes #27910, closes #19793
Type of change
What does this PR do?
Fixes three compounding session-switch responsiveness issues:
Remove deferRender mechanism — eliminates the one-frame blank + 140ms
setTimeoutinsession-composer-regionthat caused a ~170ms gap where the composer was invisible on every session switch. The composer now re-shows after a single rAF yield (~16ms).Remove sessionSync JSX read —
{sessionSync() ?? ""}was read in JSX, triggering the app-level<Suspense>boundary (splash screen) on every session switch. Since the resource returns void, the read is removed entirely — the fetcher still runs reactively from its source signal.Widen messagesReady gate — allow rendering when the session exists in the session list, even before messages have loaded. Shows a spinner in the timeline while messages load in the background, eliminating the blank screen on session switch.
How did you verify your code works?
Tested locally by rapidly switching between sessions in the web UI. Verified no blank flashes, no splash screen flicker, and the composer appears instantly. Messages load in the background with a spinner shown during loading.
Screenshots / recordings
N/A — performance/latency improvement.
Checklist