diff --git a/docs/Engineering_Reference_Manual.md b/docs/Engineering_Reference_Manual.md
index 11b54c18..b2526d5c 100644
--- a/docs/Engineering_Reference_Manual.md
+++ b/docs/Engineering_Reference_Manual.md
@@ -933,7 +933,9 @@ The `EntitlementChecker.isPremium()` Flow is collected by feature-level ViewMode
 
 - AI-assisted question suggestions (mentioned in the v0.1.0 plan; no source yet).
 
-If you add a new premium feature, mirror the established pattern: inject `CouplePremiumChecker` (or `EntitlementChecker` for the rare per-user gate), collect `isPremium()` in the VM, navigate to `paywallScreen()` on `false`. Server-side: any new premium-only Cloud Function must verify `users/{uid}/entitlements/premium` before doing work. Do not trust the client flag for server-side gating.**How to gate a new feature:**
+If you add a new premium feature, mirror the established pattern: inject `CouplePremiumChecker` (or `EntitlementChecker` for the rare per-user gate), collect `isPremium()` in the VM, navigate to `paywallScreen()` on `false`. Server-side: any new premium-only Cloud Function must verify `users/{uid}/entitlements/premium` before doing work. Do not trust the client flag for server-side gating.
+
+**How to gate a new feature:**
 
 1. Inject `EntitlementChecker` into the relevant ViewModel or Repository.
 2. On entry, collect `isPremium()`. If `false`, navigate to the paywall route (`paywallScreen()` in `AppNavigation`) with a returnTo argument. Do not silently fail or render empty state.
@@ -998,7 +1000,7 @@ The notification is both an FCM push (for the system tray) and an entry in `user
 
 ### Game session push semantics (idempotent flag-claim)
 
-The Cloud Function `functions/src/games/onGameSessionUpdate.ts` is the hub for every partner-facing push derived from a game session. The original implementation diffed `status` fields to decide whether to send a push, which produced duplicate notifications when both partners updated the doc close together. The current implementation uses an **idempotent flag-claim** pattern: a single `notificationsSent` map on the session doc records each notification type the moment it's dispatched. The trigger checks the flag, sends if absent, writes the flag. Re-running the trigger is a no-op.
+The Cloud Function `functions/src/games/onGameSessionUpdate.ts` is the hub for every partner-facing push derived from a game session. The original implementation diffed `status` fields to decide whether to send a push, which produced duplicate notifications when both partners updated the doc close together. The current implementation uses an **idempotent flag-claim** pattern: a separate server-only Timestamp per notification type on the session doc (`startNotifiedAt`, `joinNotifiedAt`, `partFinishNotifiedAt`, `finishNotifiedAt`) is claimed in a transaction the moment the corresponding push is dispatched. The trigger checks the flag, sends if absent, writes the flag. Re-running the trigger is a no-op.
 
 B6c split the same file into **four per-game part-finished triggers** plus the main `onGameSessionUpdate`:
 
@@ -1009,7 +1011,7 @@ B6c split the same file into **four per-game part-finished triggers** plus the m
 
 Each fires when its session's `answers` subcollection has exactly one key (one partner finished, the other hasn't) and idempotently claims `partFinishNotifiedAt` on the session doc before sending `partner_completed_part` to the other member. Replacing the old single "if both answers exist, notify finished" pattern. See E-GAME-003 below.
 
-This pattern is the rule for any partner-facing push derived from a game session - **never diff, always claim**. The flag keys are stable strings like `'start'`, `'join'`, `'finish'`, `'partner_answered'` (game-specific).
+This pattern is the rule for any partner-facing push derived from a game session - **never diff, always claim**. The flag keys are per-push-type Timestamps: `startNotifiedAt` (started), `joinNotifiedAt` (partner joined), `partFinishNotifiedAt` (one partner finished, the other hasn't), `finishNotifiedAt` (both completed).
 
 ### Foreground game-alert banner (R10+)