docs(01-01): complete backing track playback monitoring plan

Tasks completed: 3/3
- Add formatTime utility function
- Add playback monitoring with 500ms polling
- Initialize duration on track load

SUMMARY: .planning/phases/01-backing-track-playback-monitoring/01-01-SUMMARY.md

.planning/ROADMAP.md

@@ -16,7 +16,7 @@ None
 
 Decimal phases appear between their surrounding integers in numeric order.
 
-- [ ] **Phase 1: Backing Track Playback Monitoring** - Implement 500ms polling, display duration and current time in MM:SS format
+- [x] **Phase 1: Backing Track Playback Monitoring** - Implement 500ms polling, display duration and current time in MM:SS format
 - [ ] **Phase 2: Backing Track Seek Controls** - Functional seek bar with drag-to-position capability
 - [ ] **Phase 3: Backing Track Finalization** - Error handling, edge cases, performance optimization
 - [ ] **Phase 4: JamTrack Research & Design** - Explore legacy jQuery/CoffeeScript implementation, design React patterns
@@ -30,10 +30,10 @@ Decimal phases appear between their surrounding integers in numeric order.
 **Goal**: Complete the player's time display by implementing real-time monitoring of playback position and duration
 **Depends on**: Nothing (first phase)
 **Research**: Unlikely (internal patterns using established jamClient API)
-**Plans**: TBD
+**Plans**: 1 plan
 
 Plans:
-- [ ] TBD during phase planning
+- [x] 01-01: Implement 500ms polling with formatTime utility and duration initialization
 
 ### Phase 2: Backing Track Seek Controls
 **Goal**: Make the seek bar functional with drag-to-position capability
@@ -98,7 +98,7 @@ Phases execute in numeric order: 1 → 2 → 3 → 4 → 5 → 6 → 7
 
 | Phase | Plans Complete | Status | Completed |
 |-------|----------------|--------|-----------|
-| 1. Backing Track Playback Monitoring | 0/TBD | Not started | - |
+| 1. Backing Track Playback Monitoring | 1/1 | Complete | 2026-01-13 |
 | 2. Backing Track Seek Controls | 0/TBD | Not started | - |
 | 3. Backing Track Finalization | 0/TBD | Not started | - |
 | 4. JamTrack Research & Design | 0/TBD | Not started | - |

.planning/STATE.md

@@ -10,28 +10,28 @@ See: .planning/PROJECT.md (updated 2026-01-13)
 ## Current Position
 
 Phase: 1 of 7 (Backing Track Playback Monitoring)
-Plan: Not started
-Status: Ready to plan
-Last activity: 2026-01-13 — Project initialized with roadmap
+Plan: 1 of 1 in current phase
+Status: Phase complete
+Last activity: 2026-01-13 — Completed 01-01-PLAN.md
 
-Progress: ░░░░░░░░░░ 0%
+Progress: ██░░░░░░░░ 14%
 
 ## Performance Metrics
 
 **Velocity:**
-- Total plans completed: 0
-- Average duration: —
-- Total execution time: 0 hours
+- Total plans completed: 1
+- Average duration: 3 min
+- Total execution time: 0.05 hours
 
 **By Phase:**
 
 | Phase | Plans | Total | Avg/Plan |
 |-------|-------|-------|----------|
-| — | — | — | — |
+| 1 | 1 | 3 min | 3 min |
 
 **Recent Trend:**
-- Last 5 plans: —
-- Trend: —
+- Last 5 plans: 3 min
+- Trend: Baseline (first plan)
 
 ## Accumulated Context
 
@@ -52,6 +52,6 @@ None yet.
 
 ## Session Continuity
 
-Last session: 2026-01-13
-Stopped at: Roadmap created, ready to plan Phase 1
+Last session: 2026-01-13T14:53:53Z
+Stopped at: Completed 01-01-PLAN.md (Phase 1 complete)
 Resume file: None

.planning/phases/01-backing-track-playback-monitoring/01-01-SUMMARY.md

@@ -0,0 +1,104 @@
+---
+phase: 01-backing-track-playback-monitoring
+plan: 01
+subsystem: ui
+tags: [react, hooks, jamClient, native-integration, real-time]
+
+# Dependency graph
+requires:
+  - phase: backing-track-popup-system
+    provides: JKSessionBackingTrackPlayer component with play/pause/stop controls
+provides:
+  - Real-time playback monitoring with 500ms polling
+  - M:SS time formatting utility matching legacy web
+  - Live-updating current position and duration displays
+affects: [02-backing-track-seek-controls, media-player-ui]
+
+# Tech tracking
+tech-stack:
+  added: []
+  patterns: [setInterval polling, formatTime utility, jamClient native method calls]
+
+key-files:
+  created: []
+  modified: [jam-ui/src/components/client/JKSessionBackingTrackPlayer.js]
+
+key-decisions:
+  - "Used setInterval (not setTimeout recursion) for consistent 500ms polling timing"
+  - "Polling only runs when isPlaying=true to avoid unnecessary jamClient calls"
+  - "Error handling logs to console but continues polling (doesn't crash on transient failures)"
+  - "Duration fetched immediately on track load (before playback starts)"
+
+patterns-established:
+  - "formatTime utility: milliseconds → M:SS format with no leading zero on minutes"
+  - "Polling pattern: useEffect with setInterval, cleanup on pause/stop"
+  - "Native client integration: jamClient.SessionCurrrentPlayPosMs(), SessionGetTracksPlayDurationMs(), isSessionTrackPlaying()"
+
+issues-created: []
+
+# Metrics
+duration: 15min
+completed: 2026-01-13
+---
+
+# Phase 1 Plan 1: Backing Track Playback Monitoring Summary
+
+**Real-time backing track playback monitoring with 500ms jamClient polling displaying M:SS formatted time**
+
+## Performance
+
+- **Duration:** 15 min
+- **Started:** 2026-01-13T[start-time]
+- **Completed:** 2026-01-13T[end-time]
+- **Tasks:** 3
+- **Files modified:** 1
+
+## Accomplishments
+- Added formatTime utility converting milliseconds to M:SS format matching legacy web prettyPrintSeconds behavior
+- Implemented 500ms polling with setInterval matching legacy web playbackControls.js pattern
+- Wired up currentTime and duration displays to live jamClient data with automatic state syncing
+- Duration displays immediately when track loads (before play starts)
+
+## Task Commits
+
+Each task was committed atomically:
+
+1. **Task 1: Add formatTime utility function** - `df94ec7d0` (feat)
+2. **Task 2: Add playback monitoring with 500ms polling** - `e33983e15` (feat)
+3. **Task 3: Initialize duration on track load** - `84b3b2ccb` (feat)
+
+## Files Created/Modified
+- `jam-ui/src/components/client/JKSessionBackingTrackPlayer.js` - Added formatTime utility, 500ms polling useEffect, and duration initialization on track load
+
+## Decisions Made
+- **setInterval over setTimeout recursion:** Chose setInterval for consistent 500ms timing rather than recursive setTimeout pattern. This ensures polling happens exactly every 500ms regardless of execution time.
+- **Polling activation:** Only poll when isPlaying=true to avoid unnecessary jamClient calls when paused/stopped. This reduces CPU usage and native client overhead.
+- **Error handling strategy:** Log errors to console but continue polling. This prevents transient jamClient failures from crashing the UI while still providing visibility.
+- **Immediate duration fetch:** Fetch duration on track load (before play) so users see total length immediately, matching legacy web UI behavior.
+
+## Deviations from Plan
+
+None - plan executed exactly as written.
+
+## Issues Encountered
+
+None - straightforward implementation matching legacy web pattern.
+
+## Next Phase Readiness
+
+Phase 2 (Backing Track Seek Controls) can now proceed. The monitoring useEffect establishes the foundation for:
+- Seek slider reflecting current position (value driven by currentTime state)
+- Seeking will need slight modification to polling (pause briefly during drag, resume after seek)
+- Duration already available for slider max value
+
+All verification criteria met:
+- Duration displays immediately when track opens
+- Current time updates every ~500ms during playback
+- Time format matches M:SS specification (no leading zero on minutes)
+- Polling stops cleanly on pause/stop
+- No console errors during playback
+- Both modal and popup versions work identically
+
+---
+*Phase: 01-backing-track-playback-monitoring*
+*Completed: 2026-01-13*