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fix: prevent auto-scroll when LLM finishes generating response #163

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marksftw wants to merge 2 commits into from
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fix: prevent auto-scroll when LLM finishes generating response #163

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4fd33a9
fix: prevent auto-scroll when LLM finishes generating response
claude[bot] Jul 21, 2025
649ef32
fix: prevent auto-scroll when streaming completes
claude[bot] Aug 5, 2025
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35 changes: 31 additions & 4 deletions frontend/src/routes/_auth.chat.$chatId.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -327,17 +327,44 @@ function ChatComponent() {
const isLoading = phase === "streaming";
const isPersisting = phase === "persisting";

// Auto-scroll when new messages appear (user message or start of streaming)
// Auto-scroll when user messages are added or streaming starts
const prevMessageCountRef = useRef(localChat.messages.length);
const prevStreamingRef = useRef(false);
const streamStartedRef = useRef(false);

useEffect(() => {
const messageCount = localChat.messages.length;
const hasNewMessage = messageCount > prevMessageCountRef.current;
const justStartedStreaming = isLoading && !prevStreamingRef.current;
const justStoppedStreaming = !isLoading && prevStreamingRef.current;

if (hasNewMessage || justStartedStreaming) {
// Always scroll for new user messages or when streaming starts
// Track when streaming actually starts
if (justStartedStreaming) {
streamStartedRef.current = true;
}

// Only auto-scroll for user messages or when streaming starts
// Don't auto-scroll when assistant messages are added (streaming completion)
let shouldAutoScroll = false;

if (justStartedStreaming) {
// Always scroll when streaming starts
shouldAutoScroll = true;
} else if (hasNewMessage && !justStoppedStreaming) {
// Only scroll for new user messages, not assistant messages
// Also don't scroll if we just stopped streaming (assistant message completion)
const latestMessage = localChat.messages[localChat.messages.length - 1];
if (latestMessage?.role === "user") {
shouldAutoScroll = true;
}
}

// Reset stream tracking when streaming stops
if (justStoppedStreaming) {
streamStartedRef.current = false;
}

if (shouldAutoScroll) {
const container = chatContainerRef.current;
if (container) {
requestAnimationFrame(() => {
Expand All @@ -351,7 +378,7 @@ function ChatComponent() {

prevMessageCountRef.current = messageCount;
prevStreamingRef.current = isLoading;
}, [localChat.messages.length, isLoading]);
}, [localChat.messages.length, isLoading, localChat.messages]);

@greptile-apps greptile-apps Bot Aug 5, 2025

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style: Adding localChat.messages as a dependency may cause unnecessary re-renders since the array reference changes on every message update, even when length hasn't changed. Consider removing this dependency since localChat.messages.length already triggers the effect when needed.

Suggested change
}, [localChat.messages.length, isLoading, localChat.messages]);
}, [localChat.messages.length, isLoading]);


const sendMessage = useCallback(
async (
Expand Down