## Summary
- Fix scroll behavior when switching between chats with existing
messages
- Use double `requestAnimationFrame` to wait for Virtuoso to render
before scrolling to bottom when switching chats
- Distinguish between chat switches and new message sends to handle
scrolling appropriately
- Avoid premature scrolling when switching to chats where messages
haven't been fetched yet

## Test plan
1. Open Dyad and start a chat with some messages
2. Start another chat with messages
3. Switch between chats and verify scroll position stays at the bottom
4. Send a new message and verify it scrolls to show the new message

🤖 Generated with [Claude Code](https://claude.com/claude-code)
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<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Fixes chat auto-scroll to keep the view anchored at the bottom when
switching chats or sending messages. Prevents flicker and jumps before
messages render.

- **Bug Fixes**
- Distinguish chat switches vs new sends; adjust scroll timing
accordingly.
- On chat switch with existing messages, wait for Virtuoso to render
(double requestAnimationFrame), then scroll to bottom instantly.
- On new message send, wait for the placeholder to render (double
requestAnimationFrame) before scrolling; skip auto-scroll when switching
to a chat with no messages yet.

<sup>Written for commit 8814a601a9615b60efbfbff0aff5b7150a75fa63.
Summary will update on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Scoped to `ChatPanel` scroll timing logic; risk is limited to possible
UI regressions (missed/extra scroll) when switching chats or starting
streams.
> 
> **Overview**
> Fixes `ChatPanel` auto-scroll behavior by **distinguishing chat
switches from new stream starts** and delaying the scroll until after
Virtuoso has rendered.
> 
> On chat switch, it now scrolls to bottom *only after messages exist*
(avoiding premature scroll before fetch/render) and uses a double
`requestAnimationFrame` with `instant` scrolling; on new message sends
(`streamCount` changes), it similarly waits for render before scrolling
with the default behavior.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
8814a601a9615b60efbfbff0aff5b7150a75fa63. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>