# Story 22: Smart Auto-Scroll (Respects User Scrolling)

## User Story
As a user, I want to be able to scroll up to review previous messages while the AI is streaming or adding new content, without being constantly dragged back to the bottom.

## Acceptance Criteria
- [ ] When I scroll up in the chat, auto-scroll is temporarily disabled
- [ ] Auto-scroll resumes when I scroll back to (or near) the bottom
- [ ] There's a visual indicator when auto-scroll is paused (optional)
- [ ] Clicking a "Jump to Bottom" button (if added) re-enables auto-scroll
- [ ] Auto-scroll works normally when I'm already at the bottom
- [ ] The detection works smoothly without flickering
- [ ] Works during both streaming responses and tool execution

## Out of Scope
- Manual scroll position restoration after page refresh
- Scroll position memory across sessions
- Keyboard shortcuts for scrolling
- Custom scroll speed or animation settings

## Technical Notes
- Detect if user is scrolled to bottom: `scrollHeight - scrollTop === clientHeight` (with small threshold)
- Only auto-scroll if user is at/near bottom (e.g., within 100px)
- Track scroll position in state or ref
- Add scroll event listener to detect when user manually scrolls
- Consider debouncing the scroll detection for performance

## Design Considerations
- Threshold for "near bottom": 100-150px is typical
- Optional: Show a "↓ New messages" badge when auto-scroll is paused
- Should feel natural and not interfere with reading
- Balance between auto-scroll convenience and user control

## Implementation Approach
```tsx
const isScrolledToBottom = () => {
  const element = scrollContainerRef.current;
  if (!element) return true;
  const threshold = 150; // pixels from bottom
  return element.scrollHeight - element.scrollTop - element.clientHeight < threshold;
};

useEffect(() => {
  if (isScrolledToBottom()) {
    scrollToBottom();
  }
}, [messages, streamingContent]);
```