diff --git a/CHANGELOG.md b/CHANGELOG.md
index 67896db1..d048426b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,12 @@
 
 ## [Unreleased]
 
+## [v0.51.680] — 2026-06-26 — Release YJ (session-index rebuild can't be clobbered by a late worker)
+
+### Fixed
+
+- **A late-finishing background session-index rebuild can no longer clobber a newer rebuild's state.** When a session-index rebuild worker finished, it cleared the rebuild bookkeeping globals if only the target tuple matched — so an older worker completing after a newer rebuild had already taken over could wipe the newer owner's registration. The cleanup now also requires that the finishing worker is still the registered owner thread (`_SESSION_INDEX_REBUILD_THREAD is current_thread`, checked under the rebuild lock), so an out-of-order older worker leaves the newer owner's state intact while the genuine owner still clears normally. Thanks @rodboev. (#4993, #3894)
+
 ## [v0.51.679] — 2026-06-26 — Release YI (faster fresh sidebar boot — parallel session/project fetches)
 
 ### Fixed