fix(web): stop chat composer lag on long chats#196
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Typing in the composer stalled on long chats: dozens of keystrokes would surface seconds later. Two things compounded: - Every keystroke wrote the draft into the global store (setDraft), and ChatPage subscribes to the whole store, so each character re-rendered ChatPage. - MessageList was not memoized, so it re-rendered the entire message list on every ChatPage render. Memoize MessageList (all its props are stable store slices, unchanged while typing) and debounce the draft write (400ms, flushed on blur and on send). The composer stays responsive and drafts still persist across session switches.
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Summary
Typing in the chat composer lags badly on long chats: dozens of keystrokes surface seconds later. This fixes it with two small, localized changes.
Root cause
The draft-persistence feature writes the composer draft into the global store on every keystroke (
setDraftinChatInput).ChatPagesubscribes to the whole store with a no-selectoruseChatStore(), andMessageListis not memoized, so every keystroke re-renders the entire message list. On a short chat it is invisible; on a long one each render is expensive enough that input visibly stalls.Fix
MessageList. Its props (messages,streamingBlocks,isStreaming) are stable store slices that do not change while typing, so the list no longer re-renders when unrelated state (the draft) updates.setDraft(400ms), flushed on blur and on send, and cancelled on send. The local textarea state still updates instantly, so the composer stays responsive; drafts still persist across session switches.Test plan
npm run buildpasses (tsc + vite).Performance only, no visual change.
[ui-check: allow]