diff --git a/internal/db/queries.go b/internal/db/queries.go
index 60e409e..d6fbb91 100644
--- a/internal/db/queries.go
+++ b/internal/db/queries.go
@@ -796,8 +796,8 @@ func (database *Database) DeleteClient(
 	return nil
 }
 
-// GetSessionCount returns the number of active sessions.
-func (database *Database) GetSessionCount(
+// GetUserCount returns the number of active users.
+func (database *Database) GetUserCount(
 	ctx context.Context,
 ) (int64, error) {
 	var count int64
@@ -808,7 +808,7 @@ func (database *Database) GetSessionCount(
 	).Scan(&count)
 	if err != nil {
 		return 0, fmt.Errorf(
-			"get session count: %w", err,
+			"get user count: %w", err,
 		)
 	}
 
@@ -838,9 +838,9 @@ func (database *Database) ClientCountForSession(
 	return count, nil
 }
 
-// DeleteStaleSessions removes clients not seen since the
-// cutoff and cleans up orphaned sessions.
-func (database *Database) DeleteStaleSessions(
+// DeleteStaleUsers removes clients not seen since the
+// cutoff and cleans up orphaned users (sessions).
+func (database *Database) DeleteStaleUsers(
 	ctx context.Context,
 	cutoff time.Time,
 ) (int64, error) {
diff --git a/internal/handlers/api.go b/internal/handlers/api.go
index 47923f4..b963f9b 100644
--- a/internal/handlers/api.go
+++ b/internal/handlers/api.go
@@ -1361,20 +1361,23 @@ func (hdlr *Handlers) canAccessChannelHistory(
 	return true
 }
 
-// HandleLogout deletes the authenticated client's token.
+// HandleLogout deletes the authenticated client's token
+// and cleans up the user (session) if no clients remain.
 func (hdlr *Handlers) HandleLogout() http.HandlerFunc {
 	return func(
 		writer http.ResponseWriter,
 		request *http.Request,
 	) {
-		_, clientID, _, ok :=
+		sessionID, clientID, nick, ok :=
 			hdlr.requireAuth(writer, request)
 		if !ok {
 			return
 		}
 
+		ctx := request.Context()
+
 		err := hdlr.params.Database.DeleteClient(
-			request.Context(), clientID,
+			ctx, clientID,
 		)
 		if err != nil {
 			hdlr.log.Error(
@@ -1389,12 +1392,79 @@ func (hdlr *Handlers) HandleLogout() http.HandlerFunc {
 			return
 		}
 
+		// If no clients remain, clean up the user fully:
+		// part all channels (notifying members) and
+		// delete the session.
+		remaining, err := hdlr.params.Database.
+			ClientCountForSession(ctx, sessionID)
+		if err != nil {
+			hdlr.log.Error(
+				"client count check failed", "error", err,
+			)
+		}
+
+		if remaining == 0 {
+			hdlr.cleanupUser(
+				request, sessionID, nick,
+			)
+		}
+
 		hdlr.respondJSON(writer, request,
 			map[string]string{"status": "ok"},
 			http.StatusOK)
 	}
 }
 
+// cleanupUser parts the user from all channels (notifying
+// members) and deletes the session.
+func (hdlr *Handlers) cleanupUser(
+	request *http.Request,
+	sessionID int64,
+	nick string,
+) {
+	ctx := request.Context()
+
+	channels, _ := hdlr.params.Database.
+		GetSessionChannels(ctx, sessionID)
+
+	notified := map[int64]bool{}
+
+	var quitDBID int64
+
+	if len(channels) > 0 {
+		quitDBID, _, _ = hdlr.params.Database.InsertMessage(
+			ctx, "QUIT", nick, "", nil, nil,
+		)
+	}
+
+	for _, chanInfo := range channels {
+		memberIDs, _ := hdlr.params.Database.
+			GetChannelMemberIDs(ctx, chanInfo.ID)
+
+		for _, mid := range memberIDs {
+			if mid != sessionID && !notified[mid] {
+				notified[mid] = true
+
+				_ = hdlr.params.Database.EnqueueToSession(
+					ctx, mid, quitDBID,
+				)
+
+				hdlr.broker.Notify(mid)
+			}
+		}
+
+		_ = hdlr.params.Database.PartChannel(
+			ctx, chanInfo.ID, sessionID,
+		)
+
+		_ = hdlr.params.Database.DeleteChannelIfEmpty(
+			ctx, chanInfo.ID,
+		)
+	}
+
+	_ = hdlr.params.Database.DeleteSession(ctx, sessionID)
+}
+
 // HandleUsersMe returns the current user's session info.
 func (hdlr *Handlers) HandleUsersMe() http.HandlerFunc {
 	return hdlr.HandleState()
@@ -1406,12 +1476,12 @@ func (hdlr *Handlers) HandleServerInfo() http.HandlerFunc {
 		writer http.ResponseWriter,
 		request *http.Request,
 	) {
-		users, err := hdlr.params.Database.GetSessionCount(
+		users, err := hdlr.params.Database.GetUserCount(
 			request.Context(),
 		)
 		if err != nil {
 			hdlr.log.Error(
-				"get session count failed", "error", err,
+				"get user count failed", "error", err,
 			)
 			hdlr.respondError(
 				writer, request,
diff --git a/internal/handlers/handlers.go b/internal/handlers/handlers.go
index 763edf1..7ce952e 100644
--- a/internal/handlers/handlers.go
+++ b/internal/handlers/handlers.go
@@ -124,8 +124,16 @@ func (hdlr *Handlers) idleTimeout() time.Duration {
 	return dur
 }
 
-func (hdlr *Handlers) startCleanup(ctx context.Context) {
-	cleanupCtx, cancel := context.WithCancel(ctx)
+// startCleanup launches the idle-user cleanup goroutine.
+// We use context.Background rather than the OnStart ctx
+// because the OnStart context is startup-scoped and would
+// cancel the goroutine once all start hooks complete.
+//
+//nolint:contextcheck // intentional Background ctx
+func (hdlr *Handlers) startCleanup(_ context.Context) {
+	cleanupCtx, cancel := context.WithCancel(
+		context.Background(),
+	)
 	hdlr.cancelCleanup = cancel
 
 	go hdlr.cleanupLoop(cleanupCtx)
@@ -161,12 +169,12 @@ func (hdlr *Handlers) runCleanup(
 ) {
 	cutoff := time.Now().Add(-timeout)
 
-	deleted, err := hdlr.params.Database.DeleteStaleSessions(
+	deleted, err := hdlr.params.Database.DeleteStaleUsers(
 		ctx, cutoff,
 	)
 	if err != nil {
 		hdlr.log.Error(
-			"session cleanup failed", "error", err,
+			"user cleanup failed", "error", err,
 		)
 
 		return
@@ -174,7 +182,7 @@ func (hdlr *Handlers) runCleanup(
 
 	if deleted > 0 {
 		hdlr.log.Info(
-			"cleaned up stale clients",
+			"cleaned up stale users",
 			"deleted", deleted,
 		)
 	}