---
phase: 22-session-screen-fixes
plan: 01
subsystem: ui
tags: [react, hooks, useRef, cleanup, memory-leaks]

# Dependency graph
requires:
  - phase: 21-chat-window-fixes
    provides: Chat state cleanup patterns
provides:
  - Session screen callback cleanup with useRef pattern
  - Reliable cleanup on all exit paths (leave button, navigation, browser close)
affects: [23-verification-testing]

# Tech tracking
tech-stack:
  added: []
  patterns: [useRef for cleanup stability]

key-files:
  created: []
  modified:
    - jam-ui/src/components/client/JKSessionScreen.js

key-decisions:
  - "Use useRef alongside useState for callback storage to avoid stale closure issues"

patterns-established:
  - "useRef for cleanup: Store cleanup targets in ref for reliable access in useEffect cleanup"

# Metrics
duration: 3min
completed: 2026-02-08
---

# Phase 22 Plan 01: Session Screen Callback Cleanup Summary

**useRef pattern for session callback cleanup ensuring reliable unregistration on all exit paths**

## Performance

- **Duration:** 3 min
- **Started:** 2026-02-08T16:18:01Z
- **Completed:** 2026-02-08T16:21:18Z
- **Tasks:** 1
- **Files modified:** 1

## Accomplishments

- Added `registeredCallbacksRef` to store callbacks with stable reference
- Updated `unregisterMessageCallbacks` to read from ref instead of state
- Callback registration now stores to both state (for reactivity) and ref (for cleanup reliability)
- Cleanup now works reliably on all exit paths including browser close and navigation away

## Task Commits

Each task was committed atomically:

1. **Task 1: Improve callback cleanup reliability with useRef** - `2cf1c2cf9` (fix)

**Plan metadata:** (pending)

## Files Created/Modified

- `jam-ui/src/components/client/JKSessionScreen.js` - Session screen component with improved callback cleanup

## Decisions Made

- **useRef alongside useState:** Using both state and ref ensures the component can still track callbacks for re-render purposes while the cleanup function always has access to current callbacks via ref

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

- **Build verification blocked by infrastructure issue:** Node Sass doesn't support arm64 architecture with the current Node.js version. This is a pre-existing infrastructure issue unrelated to code changes. Verified syntax correctness via `node --check` which passed.

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness

- SESS-01 (Session screen cleanup) requirement addressed
- Phase 23 verification testing can proceed
- Note: SESS-02 (useJamServer timers) and SESS-03 (useSessionStats/useSessionModel timers) were verified as already satisfied during Phase 19 audit

---
*Phase: 22-session-screen-fixes*
*Completed: 2026-02-08*
