diff --git a/TODO.md b/TODO.md
index 184959b..af1f2fa 100644
--- a/TODO.md
+++ b/TODO.md
@@ -60,6 +60,14 @@
   duplicate id' — GREEN.
 
 ### BUG-4: hide-player-HP breaks display view (preexisting)
+- **Broader than hide-HP**: ALL 5 `storage.setDoc(getPath.activeDisplay(), ...)` calls
+  use `{merge:true}` which is IGNORED (setDoc = replace per contract).
+  Each write clobbers other fields on activeDisplay/status doc.
+  - line 1619: hide-HP toggle → clobbers campaignId+encounterId (display paused)
+  - line 1648: start combat → clobbers hidePlayerHp
+  - line 1779: end combat → clobbers hidePlayerHp
+  - line 1997: deactivate → clobbers hidePlayerHp
+  - line 2002: activate → clobbers hidePlayerHp
 - Toggle "hide player HP" in admin → display view flips to "Game Session Paused".
 - Toggling back does NOT recover. Must re-activate encounter in encounters
   panel to restore display.