# P0-002: Session Loop Bug (Returned)

**Priority:** P0 (Critical)
**Source Reference:** From SessionLoopBug.md line 4
**Date Identified:** 2025-11-12
**Previous Fix Attempt:** Commit 7b77641 - "fix: resolve 401 session refresh loop"

## Problem Description

The session refresh loop bug has returned. After completing setup and the server restarts, the UI flashes/loops rapidly if you're on the dashboard, agents, or settings pages. Users must manually logout and log back in to stop the loop.

## Reproduction Steps

1. Complete setup wizard in fresh installation
2. Click "Restart Server" button (or restart manually via `docker-compose restart server`)
3. Server goes down, Docker components restart
4. UI automatically redirects from setup to dashboard
5. **BUG:** Screen starts flashing/rapid refresh loop
6. Clicking Logout stops the loop
7. Logging back in works fine

## Root Cause Analysis

The issue is in the `SetupCompletionChecker` component which has a dependency array problem in its `useEffect` hook:

```typescript
useEffect(() => {
  const checkSetupStatus = async () => { ... }
  checkSetupStatus();
  const interval = setInterval(checkSetupStatus, 3000);
  return () => clearInterval(interval);
}, [wasInSetupMode, location.pathname, navigate]);  // ← Problem here
```

**Issue:** `wasInSetupMode` is in the dependency array. When it changes from `false` to `true` to `false`, it triggers new effect runs, creating multiple overlapping intervals without properly cleaning up the old ones.

**During Docker Restart Sequence:**
1. Initial render: creates interval 1
2. Server goes down: can't fetch health, sets `wasInSetupMode`
3. Effect re-runs: interval 1 still running, creates interval 2
4. Server comes back: detects not in setup mode
5. Effect re-runs again: interval 1 & 2 still running, creates interval 3
6. Result: 3+ intervals all polling every 3 seconds = rapid flashing

## Proposed Solution

**Option 1: Remove wasInSetupMode from dependencies (Recommended)**
```typescript
useEffect(() => {
  let wasInSetup = false;

  const checkSetupStatus = async () => {
    // Use local wasInSetup variable instead of state dependency
    // ... existing logic using wasInSetup local variable
  };

  checkSetupStatus();
  const interval = setInterval(checkSetupStatus, 3000);
  return () => clearInterval(interval);
}, [location.pathname, navigate]);  // Only pathname and navigate
```

**Option 2: Add interval guard**
```typescript
const [intervalId, setIntervalId] = useState<number | null>(null);

useEffect(() => {
  // Clear any existing interval first
  if (intervalId) {
    clearInterval(intervalId);
  }

  const checkSetupStatus = async () => { ... };
  checkSetupStatus();
  const newInterval = setInterval(checkSetupStatus, 3000);
  setIntervalId(newInterval);

  return () => clearInterval(newInterval);
}, [wasInSetupMode, location.pathname, navigate]);
```

## Definition of Done

- [ ] No screen flashing/looping after server restart
- [ ] Single polling interval active at any time
- [ ] Clean redirect to login page after setup completion
- [ ] No memory leaks from uncleared intervals
- [ ] Setup completion checker continues to work normally

## Test Plan

1. **Fresh Setup Test:**
   ```bash
   # Clean start
   docker-compose down -v --remove-orphans
   rm config/.env
   docker-compose build --no-cache
   cp config/.env.bootstrap.example config/.env
   docker-compose up -d

   # Complete setup wizard through UI
   # Verify dashboard loads normally
   ```

2. **Server Restart Test:**
   ```bash
   # Restart server manually
   docker-compose restart server

   # Watch browser for:
   # - No multiple "checking setup status" logs
   # - No 401 errors spamming console
   # - No rapid API calls to /health endpoint
   # - Clean behavior (either stays on page or redirects properly)
   ```

3. **Console Monitoring Test:**
   - Open browser developer tools before server restart
   - Watch console for multiple interval creation logs
   - Monitor Network tab for duplicate /health requests
   - Verify only one active polling interval after restart

4. **Memory Leak Test:**
   - Open browser task manager (Shift+Esc)
   - Monitor memory usage during multiple server restarts
   - Verify memory doesn't grow continuously (indicating uncleared intervals)

## Files to Modify

- `aggregator-web/src/components/SetupCompletionChecker.tsx` (main component)
- Potentially related: `aggregator-web/src/lib/store.ts` (auth store)
- Potentially related: `aggregator-web/src/pages/Setup.tsx` (calls logout before configure)

## Impact

- **Critical User Experience:** UI becomes unusable after normal server operations
- **Production Impact:** Server maintenance/restarts break user experience
- **Perceived Reliability:** System appears broken/unstable
- **Support Burden:** Users require manual intervention (logout/login) after server restarts

## Technical Notes

- This bug only manifests during server restart after setup completion
- Previous fix (commit 7b77641) addressed 401 loop but didn't solve interval cleanup
- The issue is specific to React effect dependency management
- Multiple overlapping intervals cause the rapid flashing behavior

## Verification Commands

After implementing fix:

```bash
# Monitor browser console during restart
# Should see only ONE "checking setup status" log every 3 seconds

# Test multiple restarts in succession
docker-compose restart server
# Wait 10 seconds
docker-compose restart server
# Wait 10 seconds
docker-compose restart server

# UI should remain stable throughout
```