diff --git a/.planning/REQUIREMENTS.md b/.planning/REQUIREMENTS.md
index cadf21236..542502354 100644
--- a/.planning/REQUIREMENTS.md
+++ b/.planning/REQUIREMENTS.md
@@ -9,10 +9,10 @@ Requirements for polishing media player features. Each maps to roadmap phases.
 
 ### JamTrack Fixes
 
-- [ ] **JT-01**: Defer stem/player UI rendering until backend processing completes
-- [ ] **JT-02**: Fix WindowPortal sizing to match player content (460x350)
-- [ ] **JT-03**: Implement "Create custom mix" navigation to `/jamtracks/{id}` in new tab
-- [ ] **JT-04**: Add callback cleanup for window.jamTrackDownload* in mediaSlice
+- [x] **JT-01**: Defer stem/player UI rendering until backend processing completes ✓
+- [x] **JT-02**: Fix WindowPortal sizing to match player content (460x350) ✓
+- [x] **JT-03**: Implement "Create custom mix" navigation to `/jamtracks/{id}` in new tab ✓
+- [x] **JT-04**: Add callback cleanup for window.jamTrackDownload* in mediaSlice ✓
 
 ### Backing Track Fixes
 
@@ -46,10 +46,10 @@ Explicitly excluded for this milestone.
 
 | Requirement | Phase | Status |
 |-------------|-------|--------|
-| JT-01 | Phase 26 | Pending |
-| JT-02 | Phase 26 | Pending |
-| JT-03 | Phase 26 | Pending |
-| JT-04 | Phase 26 | Pending |
+| JT-01 | Phase 26 | Complete |
+| JT-02 | Phase 26 | Complete |
+| JT-03 | Phase 26 | Complete |
+| JT-04 | Phase 26 | Complete |
 | BT-01 | Phase 27 | Pending |
 | BT-02 | Phase 27 | Pending |
 | MET-01 | Phase 28 | Pending |
diff --git a/.planning/ROADMAP.md b/.planning/ROADMAP.md
index 3aeea8f7c..292dbb642 100644
--- a/.planning/ROADMAP.md
+++ b/.planning/ROADMAP.md
@@ -16,7 +16,7 @@ v1.6 addresses usability issues reported in three media features: JamTrack (load
 
 ## Phases
 
-- [ ] **Phase 26: JamTrack Polish** - Fix loading sequence, sizing, navigation, and cleanup
+- [x] **Phase 26: JamTrack Polish** - Fix loading sequence, sizing, navigation, and cleanup ✓
 - [ ] **Phase 27: Backing Track Sync** - Enable track sync and async cleanup
 - [ ] **Phase 28: Metronome Responsiveness** - Debounce controls and cleanup timers
 
@@ -34,8 +34,8 @@ v1.6 addresses usability issues reported in three media features: JamTrack (load
 **Plans**: 2 plans
 
 Plans:
-- [ ] 26-01-PLAN.md - Fix window sizing and create custom mix navigation
-- [ ] 26-02-PLAN.md - Add callback cleanup and defer controls rendering
+- [x] 26-01-PLAN.md - Fix window sizing and create custom mix navigation ✓
+- [x] 26-02-PLAN.md - Add callback cleanup and defer controls rendering ✓
 
 ### Phase 27: Backing Track Sync
 **Goal**: Backing Track appears in session screen when opened
@@ -68,7 +68,7 @@ Plans:
 
 | Phase | Milestone | Plans Complete | Status | Completed |
 |-------|-----------|----------------|--------|-----------|
-| 26. JamTrack Polish | v1.6 | 0/2 | Planned | - |
+| 26. JamTrack Polish | v1.6 | 2/2 | Complete | 2026-02-25 |
 | 27. Backing Track Sync | v1.6 | 0/TBD | Not started | - |
 | 28. Metronome Responsiveness | v1.6 | 0/TBD | Not started | - |
 
diff --git a/.planning/phases/26-jamtrack-polish/26-VERIFICATION.md b/.planning/phases/26-jamtrack-polish/26-VERIFICATION.md
new file mode 100644
index 000000000..eb2919499
--- /dev/null
+++ b/.planning/phases/26-jamtrack-polish/26-VERIFICATION.md
@@ -0,0 +1,95 @@
+---
+phase: 26-jamtrack-polish
+verified: 2026-02-25T13:47:04Z
+status: passed
+score: 4/4 must-haves verified
+re_verification: false
+---
+
+# Phase 26: JamTrack Polish Verification Report
+
+**Phase Goal:** JamTrack player works correctly from selection through playback without freezes
+**Verified:** 2026-02-25T13:47:04Z
+**Status:** passed
+**Re-verification:** No - initial verification
+
+## Goal Achievement
+
+### Observable Truths
+
+| # | Truth | Status | Evidence |
+|---|-------|--------|----------|
+| 1 | User sees loading indicator while backend processes track (not premature stem UI) | VERIFIED | Line 598-715: Download state banner shows for 'checking', 'packaging', 'downloading', 'keying' states. Line 718-722: Loading indicator shown when isLoadingSync is true. Line 725: Controls only render when downloadState is 'idle' or 'synchronized' AND not isLoadingSync |
+| 2 | JamTrack player fits properly in popup window without scrollbars | VERIFIED | JKSessionScreen.js line 1750: WindowPortal has `width=460,height=350` with `scrollbars=no` |
+| 3 | "Create custom mix" button opens JamTrack editor in new tab | VERIFIED | JKSessionJamTrackPlayer.js line 857: `window.open(\`/jamtracks/${jamTrack?.id}\`, '_blank', 'noopener,noreferrer')` |
+| 4 | No console warnings about leaked callbacks when closing JamTrack or navigating away | VERIFIED | mediaSlice.js lines 635-641: cleanupJamTrackCallbacks() deletes window.jamTrackDownloadProgress/Success/Fail. JKSessionJamTrackPlayer.js line 174: Called in useEffect cleanup |
+
+**Score:** 4/4 truths verified
+
+### Required Artifacts
+
+| Artifact | Expected | Status | Details |
+|----------|----------|--------|---------|
+| `jam-ui/src/components/client/JKSessionScreen.js` | Corrected WindowPortal dimensions | VERIFIED | Line 1750: `width=460,height=350,scrollbars=no` (1801 lines, substantive) |
+| `jam-ui/src/components/client/JKSessionJamTrackPlayer.js` | Working create custom mix navigation, callback cleanup, deferred controls | VERIFIED | Line 857: window.open for custom mix. Line 9: imports cleanupJamTrackCallbacks. Line 174: calls cleanup on unmount. Line 725: deferred controls render (898 lines, substantive) |
+| `jam-ui/src/store/features/mediaSlice.js` | cleanupJamTrackCallbacks function | VERIFIED | Lines 635-641: Exports function that deletes window.jamTrackDownload* globals (650 lines, substantive) |
+
+### Key Link Verification
+
+| From | To | Via | Status | Details |
+|------|-----|-----|--------|---------|
+| JKSessionJamTrackPlayer.js | /jamtracks/{id} | window.open on create custom mix click | WIRED | Line 857: `window.open(\`/jamtracks/${jamTrack?.id}\`, '_blank', 'noopener,noreferrer')` |
+| JKSessionJamTrackPlayer.js | mediaSlice.js | dispatch(cleanupJamTrackCallbacks()) in useEffect cleanup | WIRED | Line 9: import. Line 174: cleanup call in useEffect return |
+| JKSessionJamTrackPlayer.js render | downloadState.state | conditional rendering of controls | WIRED | Line 598, 725: Controls hidden during loading states, shown only when 'idle' or 'synchronized' |
+| JKSessionScreen.js | JKSessionJamTrackPlayer | WindowPortal wrapper | WIRED | Line 79: import. Lines 1747-1761: WindowPortal with correct sizing wraps JKSessionJamTrackPlayer |
+
+### Requirements Coverage
+
+| Requirement | Status | Blocking Issue |
+|-------------|--------|----------------|
+| JT-01: Loading indicator during processing | SATISFIED | - |
+| JT-02: Proper popup sizing | SATISFIED | - |
+| JT-03: Create custom mix navigation | SATISFIED | - |
+| JT-04: No leaked callbacks | SATISFIED | - |
+
+### Anti-Patterns Found
+
+| File | Line | Pattern | Severity | Impact |
+|------|------|---------|----------|--------|
+| - | - | - | - | No TODO/FIXME/placeholder patterns found in modified files |
+
+### Human Verification Required
+
+### 1. Visual Sizing Check
+**Test:** Open a JamTrack in session screen, observe the popup window
+**Expected:** Popup fits content without scrollbars, dimensions approximately 460x350
+**Why human:** Visual appearance cannot be verified programmatically
+
+### 2. Create Custom Mix Flow
+**Test:** Click "create custom mix" link in JamTrack player
+**Expected:** New browser tab opens at /jamtracks/{id} with JamTrack editor
+**Why human:** Browser navigation behavior needs manual verification
+
+### 3. Loading State Flow
+**Test:** Select a JamTrack that needs downloading
+**Expected:** See loading/download progress first, controls appear only after completion
+**Why human:** Temporal behavior and state transitions need visual confirmation
+
+### 4. No Console Warnings on Close
+**Test:** Open JamTrack player, close it, check browser console
+**Expected:** No warnings about leaked callbacks or unmounted component state updates
+**Why human:** Console warnings require browser developer tools
+
+### Gaps Summary
+
+No gaps found. All must-haves verified:
+
+1. **Window sizing** - Confirmed width=460,height=350 with scrollbars=no in WindowPortal
+2. **Create custom mix** - Confirmed window.open to /jamtracks/{id} with proper security attributes
+3. **Callback cleanup** - Confirmed cleanupJamTrackCallbacks exists and is called on unmount
+4. **Deferred controls** - Confirmed controls render only when downloadState is 'idle' or 'synchronized'
+
+---
+
+*Verified: 2026-02-25T13:47:04Z*
+*Verifier: Claude (gsd-verifier)*