diff --git a/multiplayer-todo.md b/multiplayer-todo.md
index 88a3dfce..afbc0383 100644
--- a/multiplayer-todo.md
+++ b/multiplayer-todo.md
@@ -1195,7 +1195,7 @@ the local/CI/community transport, not a silent production fallback.
 | 8.15 `[D:7.8,8.3]` | **IN PROGRESS.** Pure Go probe validation treats Steam location as opaque, requires nonce/freshness/region and server-computed RTT, and implements discrepancy quarantine/release; authenticated HTTP now accepts only opaque location/nonce input through a server-owned probe provider | `server/domain/probes.go`, adversarial fixtures and `server/api/service.go` cover stale/wrong/forged evidence, the 25 ms/30% threshold, three-sample quarantine, five-clean release, authenticated provider arguments and rejection of client RTT fields; Steam coordinator and regional probe adapters remain |
 | 8.16 `[D:8.14,8.15]` | **IN PROGRESS.** Pure Go candidate/team selection implements the <=100 ms ceiling, pairwise widening tolerance, anchor inclusion, deterministic set/region scoring and balanced team partitioning; queue-backed formation now consumes the server-owned projection, fences duplicate player identities and rejects playlist/build/protocol mixing | `server/domain/matcher.go`, `teams.go` and adversarial fixtures cover no-common-region, tolerance boundaries, lexical ties, mean-rating balance, malformed candidates, duplicate identities, compatibility mismatches and queue-backed oldest-anchor formation; full population fixtures and durable matcher claim integration remain |
 | 8.17 `[D:8.14,8.16]` | **IN PROGRESS.** Pure Go proposal policy sends a 10-second response window to every selected human, requires unanimous acceptance, applies exact decline/timeout cooldowns and ranked escalation; authenticated API exposes revisioned accept/decline mutations; formed matches now pass through a playlist-aware proposal boundary | `server/domain/proposal.go`, `formation.go` and `server/api/service.go` plus adversarial fixtures cover partial/unanimous response, expiry, replay/conflict, stale API revision, casual lineup preparation and ranked metadata validation; queue precedence and allocation integration remain |
-| 8.18 `[D:8.5,8.14,8.17]` | **IN PROGRESS.** Go store layer defines PostgreSQL SERIALIZABLE whole-transaction retries and queue candidate/proposal claim SQL using `FOR UPDATE SKIP LOCKED` plus durable uniqueness/revision fences; proposal creation now inserts proposal/participants and promotes every ticket in one rollback-safe transaction with player- and playlist-bound claim predicates, queue creation has a durable idempotency/owner-read adapter, participant-scoped proposal recovery now expires OPEN proposals and pending participants transactionally at read time, and proposal accept/decline now uses participant/proposal locks, revision fencing and durable idempotency | `server/store/serializable.go`, `queue_sql.go`, `proposal_sql.go`, `proposal_recovery_sql.go` and tests cover retry classification, claim-boundary invariants, player/ticket/playlist mapping, durable queue replay/conflict, owner-scoped queue/proposal recovery, expiry/read boundaries, response replay/conflict, stale revisions, zero-row claim aborts and atomic statement ordering; live PostgreSQL adapter execution, Redis candidate index/repair, worker-failure and concurrent two-matcher integration tests remain |
+| 8.18 `[D:8.5,8.14,8.17]` | **IN PROGRESS.** Go store layer defines PostgreSQL SERIALIZABLE whole-transaction retries and queue candidate/proposal claim SQL using `FOR UPDATE SKIP LOCKED` plus durable uniqueness/revision fences; proposal creation now inserts proposal/participants and promotes every ticket in one rollback-safe transaction with player- and playlist-bound claim predicates, queue creation has a durable idempotency/owner-read adapter, participant-scoped proposal recovery now expires OPEN proposals and pending participants transactionally at read time, and proposal accept/decline now uses participant/proposal locks, revision fencing and durable idempotency; response attempts also advance expired proposals and pending participants before returning closed | `server/store/serializable.go`, `queue_sql.go`, `proposal_sql.go`, `proposal_recovery_sql.go` and tests cover retry classification, claim-boundary invariants, player/ticket/playlist mapping, durable queue replay/conflict, owner-scoped queue/proposal recovery, expiry at read and mutation boundaries, response replay/conflict, stale revisions, zero-row claim aborts and atomic statement ordering; live PostgreSQL adapter execution, Redis candidate index/repair, worker-failure and concurrent two-matcher integration tests remain |
 | 8.19 `[D:8.18]` | **IN PROGRESS.** Pure Go casual lineup requires 2–6 humans with at least one per team, fills missing slots with explicit bots, permits kickoff-only bot-slot backfill and assigns no backfill penalty/rating update; proposal preparation now derives the lineup from formed teams | `server/domain/casual.go`, `formation.go` cover both-team minimum, bot shape, live-play rejection, zero-penalty backfill and casual proposal composition; queue candidate selection, opt-in 10 s backfill proposals, reconnect/leave penalties and live integration remain |
 | 8.20 `[D:8.18]` | **IN PROGRESS.** Pure Go ranked admission requires six unique verified solo humans, rejects bots/backfill/parties, and allows only random-enabled non-elevated arenas; proposal preparation requires matching metadata for every formed player | `server/domain/ranked.go`, `formation.go` cover count, identity, party, bot/backfill, arena eligibility and formed-player metadata rejection; `ArenaRegistry` integration, allocation wiring and innocent-ticket restoration remain |
 | 8.21 `[D:8.5,8.20]` | **IN PROGRESS.** Pure Go rating core implements canonical Glicko-2, daily inactivity, ranked 1/3 and casual 1/N human-opponent weights, deterministic opponent ordering, and authoritative draw/overtime/abandon scoring | `server/domain/rating.go` has canonical/inactivity/weight/invalid-input plus draw/OT/abandon fixtures; PostgreSQL snapshot locking, rating transaction integration, seasons and concurrent result transaction tests remain |
diff --git a/server/store/proposal_recovery_sql.go b/server/store/proposal_recovery_sql.go
index bdc25249..a19006c2 100644
--- a/server/store/proposal_recovery_sql.go
+++ b/server/store/proposal_recovery_sql.go
@@ -161,6 +161,20 @@ func RespondToProposal(ctx context.Context, db *sql.DB, playerID, proposalID, id
 		if err := tx.QueryRowContext(ctx, ProposalLockSQL, proposalID).Scan(&playlist, &state, &revision, &expiresAt); err != nil {
 			return err
 		}
+		// A mutation is also a recovery boundary. If the response arrives after
+		// the window, advance both the proposal and its pending participants in
+		// this same transaction before returning the closed error. Otherwise a
+		// client that missed the expiry event could observe OPEN/PENDING forever
+		// when its first durable interaction is an accept/decline.
+		if _, err := tx.ExecContext(ctx, ProposalExpireSQL, proposalID, now); err != nil {
+			return err
+		}
+		if _, err := tx.ExecContext(ctx, ProposalParticipantExpireSQL, proposalID, now); err != nil {
+			return err
+		}
+		if !now.Before(expiresAt) {
+			return domain.ErrProposalClosed
+		}
 		if state != string(domain.Open) || !now.Before(expiresAt) {
 			return domain.ErrProposalClosed
 		}