agent-ecosystem/.claude/commands/ccc/navigation-scroll.md

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---
name: ccc:navigation-scroll
description: Navigation and scroll orchestration — tab navigation, error highlights, search scrolling, auto-scroll coordination, and common bug patterns. Use when working on useTabNavigationController, scroll restore, or navigation requests.
---
# Navigation & Scroll Orchestration
How tab navigation (error highlights, search scrolling, auto-scroll) works end-to-end.
## Architecture
### Navigation Request Model (Nonce-Based)
```typescript
// src/renderer/types/tabs.ts
interface TabNavigationRequest {
id: string; // crypto.randomUUID() — fresh nonce per click
kind: 'error' | 'search' | 'autoBottom';
highlight: 'red' | 'yellow' | 'none';
payload: ErrorNavigationPayload | SearchNavigationPayload | {};
source: 'notification' | 'triggerPreview' | 'commandPalette' | 'sessionOpen';
}
// Stored on Tab:
interface Tab {
pendingNavigation?: TabNavigationRequest; // Set by enqueue, cleared by consume
lastConsumedNavigationId?: string; // Tracks last processed request
}
```
### Store Actions (tabSlice.ts)
| Action | Purpose |
|--------|---------|
| `enqueueTabNavigation(tabId, request)` | Set `pendingNavigation` on a tab |
| `consumeTabNavigation(tabId, requestId)` | Clear `pendingNavigation`, record `lastConsumedNavigationId` |
### Navigation Sources
| Source | Slice | Creates |
|--------|-------|---------|
| Notification click / test trigger | `notificationSlice.navigateToError()` | `ErrorNavigationRequest` (red) |
| CommandPalette search result | `tabSlice.navigateToSession()` | `SearchNavigationRequest` (yellow) |
### Controller Hook: `useTabNavigationController`
**Location:** `src/renderer/hooks/useTabNavigationController.ts`
Phase state machine:
```
idle → pending → expanding → scrolling → highlighting → complete → idle
```
Key behaviors:
- **Active-tab-only:** Ignores `!isActiveTab` to prevent cross-tab races
- **Nonce dedup:** `activeRequestIdRef.current === pendingNavigation.id` prevents reprocessing
- **Failure debounce:** 500ms cooldown after failed navigation (`lastFailureAtRef`)
- **Abort support:** New navigation aborts in-progress one via `AbortController`
- **Highlight-first:** Highlight is set BEFORE scroll (best-effort scroll, guaranteed highlight)
### Scroll Precedence (ChatHistory.tsx)
Three scroll systems compete — navigation wins:
| System | Guard | Priority |
|--------|-------|----------|
| Navigation scroll | Controller's `executeNavigation` | Highest |
| Scroll restore (tab switch) | `!shouldDisableAutoScroll` | Medium |
| Auto-scroll to bottom | `disabled: shouldDisableAutoScroll` | Lowest |
`shouldDisableAutoScroll` is `true` during ANY navigation phase or when `pendingNavigation` exists.
## Key Files
| File | Role |
|------|------|
| `src/renderer/hooks/useTabNavigationController.ts` | Unified navigation controller |
| `src/renderer/hooks/navigation/utils.ts` | Shared helpers (scroll calc, element lookup, visibility) |
| `src/renderer/components/chat/ChatHistory.tsx` | Scroll restore + auto-scroll coordination |
| `src/renderer/store/slices/tabSlice.ts` | `enqueueTabNavigation`, `consumeTabNavigation`, `navigateToSession` |
| `src/renderer/store/slices/notificationSlice.ts` | `navigateToError` |
| `src/renderer/store/slices/sessionDetailSlice.ts` | `fetchSessionDetail` (sets `conversationLoading`) |
| `src/renderer/types/tabs.ts` | `TabNavigationRequest` types + factory helpers |
## Common Bug Patterns
### 1. Scroll Restore Overrides Navigation
**Symptom:** Scrolls to target, then snaps back to top/previous position.
**Root cause:** The scroll restore effect fires after `consumeTabNavigation` clears `pendingNavigation`. If the guard only checks `!pendingNavigation`, it triggers while navigation highlight is still active.
**Fix pattern:** Guard scroll restore with `!shouldDisableAutoScroll` instead of `!pendingNavigation`. The controller's `shouldDisableAutoScroll` covers the FULL lifecycle (pending → complete), not just while `pendingNavigation` exists.
**Additional:** Save scroll position when `shouldDisableAutoScroll` transitions true→false (navigation completed) to prevent stale `savedScrollTop` from being restored later.
```typescript
// ChatHistory.tsx — scroll restore effect
useEffect(() => {
const wasDisabled = prevShouldDisableRef.current;
prevShouldDisableRef.current = shouldDisableAutoScroll;
// Navigation just completed — save current position, skip restore
if (wasDisabled && !shouldDisableAutoScroll && scrollContainerRef.current) {
saveScrollPosition(scrollContainerRef.current.scrollTop);
return;
}
if (isThisTabActive && savedScrollTop !== undefined && !conversationLoading && !shouldDisableAutoScroll) {
// ... restore logic
}
}, [isThisTabActive, savedScrollTop, conversationLoading, shouldDisableAutoScroll, saveScrollPosition]);
```
### 2. Redundant `fetchSessionDetail` Unmounts ChatHistory
**Symptom:** Navigation doesn't scroll at all, or session "reloads" unnecessarily.
**Root cause:** `navigateToSession` or `navigateToError` calls `fetchSessionDetail` even when the session is already loaded in an existing tab. This sets `conversationLoading: true`, causing ChatHistory to unmount (show loading spinner) and remount — losing scroll container and controller state.
**Fix pattern:** Only call `fetchSessionDetail` for NEW tabs. For existing tabs, `setActiveTab` already handles the fetch when `sessionChanged` is true.
```typescript
// tabSlice.ts — navigateToSession
if (existingTab) {
state.setActiveTab(existingTab.id);
// NO fetchSessionDetail — setActiveTab handles it
} else {
state.openTab({ ... });
void state.fetchSessionDetail(projectId, sessionId); // Only for new tabs
}
```
### 3. Highlight Not Showing (Strict Post-Scroll Gates)
**Symptom:** Scrolls to correct location but no red/yellow highlight ring appears.
**Root cause:** `executeErrorNavigation` / `executeSearchNavigation` returns `false` after scroll due to strict gates:
- `userInterrupted` — any accidental wheel/touch event during smooth scroll
- `isElementVisibleInContainer` — element partially off-screen after centering (tall elements)
- Element not found within 600ms timeout
When `success = false`, `executeNavigation` clears all highlight state (`setHighlightedGroupId(null)`).
**Fix pattern:** Set highlight BEFORE scroll attempt. Make scroll best-effort. Always return `true` once target group is found.
```typescript
// In executeErrorNavigation:
// 1. Find target group
// 2. Expand group
// 3. SET HIGHLIGHT HERE (before scroll)
setHighlightedGroupId(targetGroupId);
setIsSearchHighlight(false);
if (toolUseId) setCurrentToolUseId(toolUseId);
// 4. Best-effort scroll (don't gate highlight on scroll outcome)
// 5. Return true (highlight already visible)
```
### 4. Test Trigger Shows No Highlight
**Symptom:** "Test trigger" creates an error with a timestamp that doesn't match any AI group. Navigation scrolls but nothing is highlighted.
**Root cause:** Same as #3. The error timestamp doesn't match, so `findAIGroupByTimestamp` falls back to closest/last group. But post-scroll gates prevent the highlight from being applied.
**Fix:** Same as #3 — highlight-first pattern.
### 5. `conversationLoading` Race During Tab Switch
**Symptom:** Navigation queued on tab, but when switching to that tab, loading state causes ChatHistory unmount. Navigation controller state is lost.
**Root cause:** `fetchSessionDetail` immediately sets `conversationLoading: true`. ChatHistory returns `<ChatHistoryLoadingState />`, unmounting the controller hook.
**Recovery:** The controller is designed to survive remount — when ChatHistory remounts with `pendingNavigation` still set and `conversationLoading: false`, the detection effect starts fresh navigation. BUT scroll restore can race with it (see #1).
## Debugging Checklist
When navigation isn't working:
1. **Check `pendingNavigation` exists on the tab** — is `enqueueTabNavigation` called?
2. **Check `isActiveTab` is true** — controller ignores inactive tabs
3. **Check `conversationLoading`** — if true, controller waits in `pending` phase
4. **Check `conversation` exists** — if null, controller waits
5. **Check timestamp matching** — does `findAIGroupByTimestamp` find the right group?
6. **Check element refs** — are `aiGroupRefs` / `chatItemRefs` populated?
7. **Check `shouldDisableAutoScroll`** — is scroll restore racing with navigation?
8. **Check for double `fetchSessionDetail`** — is ChatHistory unmounting unnecessarily?
9. **Check `phase` progression** — is it stuck in `pending` or failing at `scrolling`?
## Navigation Helper Functions (navigation/utils.ts)
| Function | Purpose |
|----------|---------|
| `findAIGroupByTimestamp(items, timestamp)` | Find AI group containing/closest to timestamp |
| `findChatItemByTimestamp(items, timestamp)` | Find any chat item by timestamp |
| `findAIGroupBySubagentId(items, subagentId)` | Find AI group by subagent ID |
| `calculateCenteredScrollTop(element, container, offset)` | Calculate scroll position to center element |
| `waitForElementStability(element, timeout, stableFrames)` | Wait for element size to stop changing |
| `waitForScrollEnd(container, timeout)` | Wait for smooth scroll to finish |
| `isElementVisibleInContainer(element, container, offset)` | Check if element is in viewport |
| `findCurrentSearchResultInContainer(container)` | Find `[data-search-result="current"]` element |
## Factory Helpers (tabs.ts)
```typescript
createErrorNavigationRequest({ errorId, errorTimestamp, toolUseId, lineNumber })
createSearchNavigationRequest({ query, messageTimestamp, matchedText })
isErrorPayload(request) // type guard
isSearchPayload(request) // type guard
```
## Tests
Related test files:
- `test/renderer/store/tabSlice.test.ts``enqueueTabNavigation` / `consumeTabNavigation`
- `test/renderer/store/notificationSlice.test.ts``navigateToError` behavior
- `test/renderer/hooks/navigationUtils.test.ts` — Navigation utility functions
- `test/renderer/hooks/useSearchContextNavigation.test.ts` — Search result finding
Test patterns:
```typescript
// Mock crypto for predictable nonces
vi.stubGlobal('crypto', { randomUUID: () => `test-uuid-${++counter}` });
// Verify navigation request shape
expect(tab.pendingNavigation?.kind).toBe('error');
expect(tab.pendingNavigation?.highlight).toBe('red');
// Verify nonce uniqueness on repeated clicks
store.getState().navigateToError(error);
const firstId = store.getState().openTabs[0].pendingNavigation?.id;
store.getState().navigateToError(error);
const secondId = store.getState().openTabs[0].pendingNavigation?.id;
expect(firstId).not.toBe(secondId);
```