diff --git a/COMPLETED.md b/COMPLETED.md
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@@ -8,6 +8,22 @@ Newest entries at the top. Group by phase/wave header (mirroring `PLAN.md` / `CM
 
 ## Phase 8 — CMS Track Browser
 
+### 8.6 CMS cache invalidation + orphaned release deletion (Wave 6)
+
+**Landed:** 2026-06-12 on dev.
+
+Three linked CMS bug fixes discovered during Phase 8 browser work:
+
+1. **Cache invalidation on mutations** — Added `CmsTrackBrowserViewModel.Invalidate()` method called from `TrackEdit`, `BatchEdit`, and `TrackList.OnAlbumsChanged` after any track/release mutation. Ensures the album/genre browse cache is never stale when tracks are added, edited, or deleted.
+
+2. **Orphaned release handling** — `CmsAlbumBrowser` now handles 0-track (orphaned) releases with a confirmation dialog + `DeleteReleaseAsync` via a new `DELETE api/track/release/{id}` endpoint. Partial-failure album-delete path also invalidates the cache. Admin can now clean up releases that have lost all their tracks.
+
+3. **Cascade-delete on last-track removal** — EF migration `SoftDeleteOrphanedReleases` (data-only, raw SQL) backfills orphaned release rows with soft-delete markers. `UnifiedTrackService.DeleteAsync` now cascades a release soft-delete when the last live track in a release is deleted (non-fatal; orphaned releases do not block track deletion).
+
+**Completion note:** `CmsTrackBrowserViewModel.Invalidate()` added and wired into mutation paths. New `DELETE api/track/release/{id}` endpoint implemented on `UnifiedTrackService`. `CmsAlbumBrowser` updated with orphaned release confirmation + delete. `SoftDeleteOrphanedReleases` migration authored and applied. All three fixes integrated; Phase 8 browse modes remain stable with correct cache coherence and release cleanup semantics.
+
+---
+
 ### 8.0 `TrackEntity` normalization
 
 **Landed:** 2026-06-11 on dev.