Pause chat auto-scroll on upward wheel over nested content

[imanolmzd-svg]

Part of #11030

Why

Scrolling within a nested container in the chat would create a quick moveup and down, disrupting the user scroll intention.

Implementation

We changed chat auto-scroll to prioritize explicit user intent (As opposed to position based).

Any upward wheel gesture within the conversation—including over nested tool outputs or code blocks—immediately pauses “follow bottom” via the existing stop() state.

We removed the previous data-scrollable exception and geometry-based ownership checks, because nested containers may not currently overflow or may be at a boundary. Auto-scroll resumes only through the existing resume action.

Screenshots / Video

Before

wiggle.mov

After

wiggle-fix.mov

Testing

• Manual, as shown above
• Unit tests
• Typecheck

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (3 files)

• .changeset/fix-nested-chat-scroll.md
• packages/kilo-ui/src/hooks/auto-scroll.ts
• packages/kilo-ui/src/hooks/create-auto-scroll.tsx

Notes:

The fix is well-reasoned and the implementation is correct:

• handleWheel now runs in capture phase ({ passive: true, capture: true }), ensuring it intercepts upward wheel events even when a nested element would stop propagation. The removeEventListener cleanup correctly mirrors the { capture: true } option.
• markUser now early-returns for all WheelEvents. Wheel-driven pausing is handled exclusively by handleWheel → stop(), which sets userScrolled = true synchronously. Subsequent resize observer and handleScroll callbacks both check store.userScrolled before any recentlyInteracted() path, so the removal of wheel events from lastInteraction tracking is safe.
• Deletion of isNested / data-scrollable opt-in logic is intentional and removes the footgun described in the PR — nested containers may not overflow or may be at a boundary, making geometry checks unreliable.
• Changeset is present and user-facing description is appropriate.

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_{Reviewed by claude-4.6-sonnet-20260217 · 207,875 tokens}

_{Review guidance: REVIEW.md from base branch main}