fix: debounce chat session persistence to prevent excessive localStor…

[priyanshu5ingh]

🔀 Pull Request

📌 Issue Reference

Closes #431

---

📝 Summary

Problem: The chat page persisted the entire conversation to localStorage on every messages state change via useEffect at ChatbotPage.tsx:128-132. During AI streaming responses, setMessages was called on each received chunk (dozens of times per response), each triggering a full synchronous localStorage.setItem that blocked the main thread and degraded UI responsiveness.

Solution: Debounced the persistence effect using a generic useDebounce hook with a 1500ms delay, so localStorage is only written after a quiet period. Added unmount-flush logic via refs to ensure no data is lost when navigating away mid-stream.

Major Changes

File	Change
src/hooks/useDebounce.ts	New — Generic useDebounce<T>(value, delay) hook that returns a debounced value, updating only after delay ms of inactivity
src/pages/ChatbotPage.tsx	Added useDebounce import; replaced [messages, uploadedDoc] persist effect with debounced variant; added refs (latestMessagesRef, latestDocRef, latestSessionIdRef) for unmount flush; added cleanup effect that persists latest messages synchronously on unmount
src/test/hooks/useDebounce.test.ts	New — 6 unit tests covering initial value, delay gating, timer reset on rapid changes, numeric types, and zero-delay edge case

---

📸 Screenshots

N/A — performance improvement, no visual change.

---

✅ Checklist

• My code follows the project's coding conventions
• I have tested all impacted features
• I have updated or added necessary documentation

---

🏅 Open Source Program Participation

Program Name: GSSoC 2026

---

💬 Additional Notes

• Debounce delay (1500ms): Long enough to batch all stream chunks into a single write, short enough to feel responsive after sending a message.
• Unmount safety: Refs (latestMessagesRef, latestDocRef, latestSessionIdRef) are updated on every render so the useEffect cleanup (which has empty deps) can access the absolute latest values — not stale closure values.
• Testing: All 148 tests pass (13 suites, +6 new hook tests, 0 regressions).
• Streaming behavior: Before this fix, a response with 50 chunks would trigger 50+ synchronous localStorage writes on the main thread. After this fix, only 1 write fires 1.5s after the stream completes.

[vercel]

Someone is attempting to deploy a commit to the WizardKing's projects Team on Vercel.

A member of the Team first needs to authorize it.

[AnuranjanJain]

@priyanshu5ingh can you look for the merge conflicts

[github-actions]

This PR has been inactive for 7 days. Please update the PR to keep it open. It will be closed in 3 days if there is no further activity.

[priyanshu5ingh]

@AnuranjanJain i have committed the conflicts

[github-actions]

This PR has been inactive for 7 days. Please update the PR to keep it open. It will be closed in 3 days if there is no further activity.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
legal-ease	Ready	Preview	Aug 2, 2026 1:23pm