diff --git a/internal/db/db.go b/internal/db/db.go
index 751ad45..e6901e1 100644
--- a/internal/db/db.go
+++ b/internal/db/db.go
@@ -137,6 +137,7 @@ func runMigrations(d *sql.DB) error {
 		`ALTER TABLE adventure_characters ADD COLUMN streak_decayed INTEGER NOT NULL DEFAULT 0`,
 		`ALTER TABLE coop_dungeon_runs ADD COLUMN last_resolved_day INTEGER NOT NULL DEFAULT 0`,
 		`ALTER TABLE coop_dungeon_members ADD COLUMN member_payout INTEGER`,
+		`ALTER TABLE coop_dungeon_runs ADD COLUMN invite_post_id TEXT NOT NULL DEFAULT ''`,
 	}
 	for _, stmt := range columnMigrations {
 		if _, err := d.Exec(stmt); err != nil {
@@ -1387,6 +1388,7 @@ CREATE TABLE IF NOT EXISTS coop_dungeon_runs (
     gold_pool         INTEGER NOT NULL DEFAULT 0,    -- accumulated funding
     reward_total      INTEGER NOT NULL DEFAULT 0,    -- final reward (set on completion)
     last_resolved_day INTEGER NOT NULL DEFAULT 0,    -- crash-resume guard: highest day whose floor outcome is final
+    invite_post_id    TEXT NOT NULL DEFAULT '',      -- Matrix event ID of the games-room invite (for pin/unpin)
     created_at        DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
     locked_at         DATETIME,
     completed_at      DATETIME
diff --git a/internal/plugin/coop_dungeon.go b/internal/plugin/coop_dungeon.go
index 1e3f92e..cfcbb4a 100644
--- a/internal/plugin/coop_dungeon.go
+++ b/internal/plugin/coop_dungeon.go
@@ -174,7 +174,11 @@ func (p *AdventurePlugin) handleCoopStart(ctx MessageContext, tierArg string) er
 
 	gr := gamesRoom()
 	if gr != "" {
-		_ = p.SendMessage(gr, renderCoopInvite(run, []CoopMember{{UserID: ctx.Sender, TurnOrder: 0}}, char.DisplayName))
+		postID, err := p.SendMessageID(gr, renderCoopInvite(run, []CoopMember{{UserID: ctx.Sender, TurnOrder: 0}}, char.DisplayName))
+		if err == nil {
+			_ = setCoopRunInvitePostID(run.ID, postID)
+			_ = p.PinEvent(gr, postID)
+		}
 	}
 	return p.SendDM(ctx.Sender, fmt.Sprintf("⚔️ Tier %d co-op invite opened (#%d). Locks in 24h. Recruit your party.", tier, run.ID))
 }
@@ -353,6 +357,9 @@ func (p *AdventurePlugin) handleCoopCancel(ctx MessageContext) error {
 	}
 	gr := gamesRoom()
 	if gr != "" {
+		if run.InvitePostID != "" {
+			_ = p.UnpinEvent(gr, run.InvitePostID)
+		}
 		_ = p.SendMessage(gr, fmt.Sprintf("⚔️ Tier %d Co-op #%d cancelled by the leader.", run.Tier, run.ID))
 	}
 	return p.SendDM(ctx.Sender, fmt.Sprintf("Run #%d cancelled.", run.ID))
diff --git a/internal/plugin/coop_dungeon_db.go b/internal/plugin/coop_dungeon_db.go
index 4a4e435..38a60a5 100644
--- a/internal/plugin/coop_dungeon_db.go
+++ b/internal/plugin/coop_dungeon_db.go
@@ -24,6 +24,7 @@ type CoopRun struct {
 	GoldPool        int
 	RewardTotal     int
 	LastResolvedDay int
+	InvitePostID    id.EventID
 	CreatedAt       time.Time
 	LockedAt        *time.Time
 	CompletedAt     *time.Time
@@ -55,10 +56,11 @@ func loadCoopRun(runID int) (*CoopRun, error) {
 	var leader string
 	var lockedAt, completedAt sql.NullTime
 	err := d.QueryRow(`SELECT id, tier, status, leader_id, current_day, total_days,
-		base_difficulty, gold_pool, reward_total, last_resolved_day, created_at, locked_at, completed_at
+		base_difficulty, gold_pool, reward_total, last_resolved_day, invite_post_id, created_at, locked_at, completed_at
 		FROM coop_dungeon_runs WHERE id = ?`, runID).Scan(
 		&r.ID, &r.Tier, &r.Status, &leader, &r.CurrentDay, &r.TotalDays,
 		&r.BaseDifficulty, &r.GoldPool, &r.RewardTotal, &r.LastResolvedDay,
+		(*string)(&r.InvitePostID),
 		&r.CreatedAt, &lockedAt, &completedAt)
 	if err != nil {
 		return nil, err
@@ -94,7 +96,7 @@ func loadMostRecentOpenCoopRun() (*CoopRun, error) {
 func queryCoopRuns(whereClause string) ([]*CoopRun, error) {
 	d := db.Get()
 	rows, err := d.Query(`SELECT id, tier, status, leader_id, current_day, total_days,
-		base_difficulty, gold_pool, reward_total, last_resolved_day, created_at, locked_at, completed_at
+		base_difficulty, gold_pool, reward_total, last_resolved_day, invite_post_id, created_at, locked_at, completed_at
 		FROM coop_dungeon_runs WHERE ` + whereClause)
 	if err != nil {
 		return nil, err
@@ -108,6 +110,7 @@ func queryCoopRuns(whereClause string) ([]*CoopRun, error) {
 		var lockedAt, completedAt sql.NullTime
 		if err := rows.Scan(&r.ID, &r.Tier, &r.Status, &leader, &r.CurrentDay, &r.TotalDays,
 			&r.BaseDifficulty, &r.GoldPool, &r.RewardTotal, &r.LastResolvedDay,
+			(*string)(&r.InvitePostID),
 			&r.CreatedAt, &lockedAt, &completedAt); err != nil {
 			return nil, err
 		}
@@ -169,6 +172,12 @@ func completeCoopRun(runID int, status string, reward int) error {
 	return err
 }
 
+func setCoopRunInvitePostID(runID int, postID id.EventID) error {
+	d := db.Get()
+	_, err := d.Exec(`UPDATE coop_dungeon_runs SET invite_post_id = ? WHERE id = ?`, string(postID), runID)
+	return err
+}
+
 // setCoopRunLastResolvedDay marks a day as resolved for crash-resume idempotency.
 // Resolution is idempotent: re-entering coopResolveFloor for the same day is a no-op.
 func setCoopRunLastResolvedDay(runID, day int) error {
diff --git a/internal/plugin/coop_dungeon_scheduler.go b/internal/plugin/coop_dungeon_scheduler.go
index 23fee7d..e9bfdc3 100644
--- a/internal/plugin/coop_dungeon_scheduler.go
+++ b/internal/plugin/coop_dungeon_scheduler.go
@@ -68,6 +68,9 @@ func (p *AdventurePlugin) coopProcessLocks() {
 			_ = setCoopRunStatus(run.ID, "cancelled")
 			gr := gamesRoom()
 			if gr != "" {
+				if run.InvitePostID != "" {
+					_ = p.UnpinEvent(gr, run.InvitePostID)
+				}
 				_ = p.SendMessage(gr, fmt.Sprintf("⚔️ Tier %d Co-op #%d expired with no party. Cancelled.", run.Tier, run.ID))
 			}
 			_ = p.SendDM(run.LeaderID, fmt.Sprintf("Co-op #%d expired before anyone joined. No party, no run.", run.ID))
@@ -94,6 +97,9 @@ func (p *AdventurePlugin) coopProcessLocks() {
 		fresh, _ := loadCoopRun(run.ID)
 		gr := gamesRoom()
 		if gr != "" {
+			if run.InvitePostID != "" {
+				_ = p.UnpinEvent(gr, run.InvitePostID)
+			}
 			_ = p.SendMessage(gr, renderCoopLock(fresh, members, p))
 		}
 		// Per-player DM with funding instructions.
diff --git a/internal/plugin/plugin.go b/internal/plugin/plugin.go
index eb097ce..1638101 100644
--- a/internal/plugin/plugin.go
+++ b/internal/plugin/plugin.go
@@ -37,6 +37,10 @@ type MessageContext struct {
 	Body      string
 	IsCommand bool // true if the message starts with the command prefix
 	Event     *event.Event
+	// OriginRoomID is set by plugins that rewrite RoomID for dispatch (e.g. holdem
+	// routes DM commands to the player's game room). When set, sender-private
+	// replies should go here instead of the rewritten RoomID.
+	OriginRoomID id.RoomID
 }
 
 // ReactionContext holds the context for a reaction event.
@@ -703,6 +707,61 @@ func (b *Base) SendDMID(userID id.UserID, text string) (id.EventID, error) {
 	return b.SendMessageID(roomID, text)
 }
 
+// PinEvent appends the given event ID to the room's m.room.pinned_events
+// state. No-op if already pinned. Requires the bot to have power level for
+// state events; failures are logged and returned without retry.
+func (b *Base) PinEvent(roomID id.RoomID, eventID id.EventID) error {
+	var content event.PinnedEventsEventContent
+	err := b.Client.StateEvent(context.Background(), roomID, event.StatePinnedEvents, "", &content)
+	if err != nil && !strings.Contains(err.Error(), "M_NOT_FOUND") {
+		slog.Error("pin: read state", "room", roomID, "err", err)
+		return err
+	}
+	for _, id := range content.Pinned {
+		if id == eventID {
+			return nil // already pinned
+		}
+	}
+	content.Pinned = append(content.Pinned, eventID)
+	_, err = b.Client.SendStateEvent(context.Background(), roomID, event.StatePinnedEvents, "", content)
+	if err != nil {
+		slog.Error("pin: write state", "room", roomID, "event", eventID, "err", err)
+	}
+	return err
+}
+
+// UnpinEvent removes the given event ID from the room's pinned events.
+// No-op if not currently pinned.
+func (b *Base) UnpinEvent(roomID id.RoomID, eventID id.EventID) error {
+	var content event.PinnedEventsEventContent
+	err := b.Client.StateEvent(context.Background(), roomID, event.StatePinnedEvents, "", &content)
+	if err != nil {
+		if strings.Contains(err.Error(), "M_NOT_FOUND") {
+			return nil
+		}
+		slog.Error("unpin: read state", "room", roomID, "err", err)
+		return err
+	}
+	out := content.Pinned[:0]
+	found := false
+	for _, id := range content.Pinned {
+		if id == eventID {
+			found = true
+			continue
+		}
+		out = append(out, id)
+	}
+	if !found {
+		return nil
+	}
+	content.Pinned = out
+	_, err = b.Client.SendStateEvent(context.Background(), roomID, event.StatePinnedEvents, "", content)
+	if err != nil {
+		slog.Error("unpin: write state", "room", roomID, "event", eventID, "err", err)
+	}
+	return err
+}
+
 // EditMessage edits an existing message using Matrix m.replace relation.
 func (b *Base) EditMessage(roomID id.RoomID, eventID id.EventID, newText string) error {
 	newContent := textContent(newText)