diff --git a/pkg/channels/pico/pico.go b/pkg/channels/pico/pico.go
index fda65a7a9..d6e333725 100644
--- a/pkg/channels/pico/pico.go
+++ b/pkg/channels/pico/pico.go
@@ -20,13 +20,72 @@ import (
 	"github.com/sipeed/picoclaw/pkg/logger"
 )
 
-// picoConn represents a single WebSocket connection.
+// picoConn represents a single WebSocket connection with session tracking.
 type picoConn struct {
-	id        string
-	conn      *websocket.Conn
-	sessionID string
-	writeMu   sync.Mutex
-	closed    atomic.Bool
+	id         string
+	conn       *websocket.Conn
+	sessionID  string              // Primary session ID (from connection establishment)
+	sessions   map[string]struct{} // All session IDs this connection participates in
+	sessionsMu sync.RWMutex        // Protects sessions map
+	writeMu    sync.Mutex
+	closed     atomic.Bool
+}
+
+// addSession adds a session ID to this connection.
+func (pc *picoConn) addSession(sessionID string) {
+	if sessionID == "" || sessionID == pc.sessionID {
+		return
+	}
+
+	pc.sessionsMu.Lock()
+	defer pc.sessionsMu.Unlock()
+
+	pc.sessions[sessionID] = struct{}{}
+}
+
+// removeSession removes a session ID from this connection.
+func (pc *picoConn) removeSession(sessionID string) {
+	if sessionID == "" || sessionID == pc.sessionID {
+		return
+	}
+
+	pc.sessionsMu.Lock()
+	defer pc.sessionsMu.Unlock()
+
+	delete(pc.sessions, sessionID)
+}
+
+// hasSession checks if this connection belongs to a session.
+func (pc *picoConn) hasSession(sessionID string) bool {
+	if sessionID == "" {
+		return false
+	}
+
+	pc.sessionsMu.RLock()
+	defer pc.sessionsMu.RUnlock()
+
+	_, ok := pc.sessions[sessionID]
+	return ok
+}
+
+// getSessions returns all session IDs this connection participates in.
+func (pc *picoConn) getSessions() []string {
+	pc.sessionsMu.RLock()
+	defer pc.sessionsMu.RUnlock()
+
+	result := make([]string, 0, len(pc.sessions))
+	for sessionID := range pc.sessions {
+		result = append(result, sessionID)
+	}
+	return result
+}
+
+// getSessionCount returns the number of sessions this connection participates in.
+func (pc *picoConn) getSessionCount() int {
+	pc.sessionsMu.RLock()
+	defer pc.sessionsMu.RUnlock()
+
+	return len(pc.sessions)
 }
 
 // writeJSON sends a JSON message to the connection with write locking.
@@ -197,7 +256,7 @@ func (c *PicoChannel) SendPlaceholder(ctx context.Context, chatID string) (strin
 	return msgID, nil
 }
 
-// broadcastToSession sends a message to all connections with a matching session.
+// broadcastToSession sends a message to the connection with a matching session.
 func (c *PicoChannel) broadcastToSession(chatID string, msg PicoMessage) error {
 	// chatID format: "pico:<sessionID>"
 	sessionID := strings.TrimPrefix(chatID, "pico:")
@@ -209,21 +268,30 @@ func (c *PicoChannel) broadcastToSession(chatID string, msg PicoMessage) error {
 		if !ok {
 			return true
 		}
-		if key == sessionID {
+		// Use hasSession to check if connection belongs to this session
+		if pc.hasSession(sessionID) {
 			if err := pc.writeJSON(msg); err != nil {
 				logger.DebugCF("pico", "Write to connection failed", map[string]any{
 					"conn_id": pc.id,
+					"session": sessionID,
 					"error":   err.Error(),
 				})
 			} else {
 				sent = true
+				return false // Session found and message sent, stop iterating
 			}
 		}
 		return true
 	})
 
+	logger.DebugCF("pico", "Message sent to session",
+		map[string]any{
+			"session": sessionID,
+			"sent":    sent,
+		})
+
 	if !sent {
-		return fmt.Errorf("no active connections for session %s: %w", sessionID, channels.ErrSendFailed)
+		return fmt.Errorf("no active connection for session %s: %w", sessionID, channels.ErrSendFailed)
 	}
 	return nil
 }
@@ -269,14 +337,16 @@ func (c *PicoChannel) handleWebSocket(w http.ResponseWriter, r *http.Request) {
 		id:        uuid.New().String(),
 		conn:      conn,
 		sessionID: sessionID,
+		sessions:  map[string]struct{}{sessionID: {}}, // Initialize with primary session
 	}
 
 	c.connections.Store(pc.id, pc)
 	c.connCount.Add(1)
 
 	logger.InfoCF("pico", "WebSocket client connected", map[string]any{
-		"conn_id":    pc.id,
-		"session_id": sessionID,
+		"conn_id":       pc.id,
+		"session_id":    sessionID,
+		"session_count": pc.getSessionCount(),
 	})
 
 	go c.readLoop(pc)
@@ -312,11 +382,19 @@ func (c *PicoChannel) authenticate(r *http.Request) bool {
 func (c *PicoChannel) readLoop(pc *picoConn) {
 	defer func() {
 		pc.close()
+
+		// Get all sessions for logging before cleanup
+		sessions := pc.getSessions()
+
 		c.connections.Delete(pc.id)
 		c.connCount.Add(-1)
+
+		// Sessions will be automatically cleaned up when picoConn is GC'd
 		logger.InfoCF("pico", "WebSocket client disconnected", map[string]any{
-			"conn_id":    pc.id,
-			"session_id": pc.sessionID,
+			"conn_id":       pc.id,
+			"session_id":    pc.sessionID,
+			"sessions":      sessions,
+			"session_count": len(sessions),
 		})
 	}()
 
@@ -421,11 +499,16 @@ func (c *PicoChannel) handleMessageSend(pc *picoConn, msg PicoMessage) {
 	sessionID := msg.SessionID
 	if sessionID == "" {
 		sessionID = pc.sessionID
-	} else {
-		// Check if sessionID already exists
-		if _, ok := c.connections.Load(sessionID); !ok {
-			c.connections.Store(sessionID, pc)
-		}
+	} else if sessionID != pc.sessionID {
+		// Add new sessionID to connection's session set
+		pc.addSession(sessionID)
+
+		logger.DebugCF("pico", "Session added to connection",
+			map[string]any{
+				"conn_id":       pc.id,
+				"session_id":    sessionID,
+				"session_count": pc.getSessionCount(),
+			})
 	}
 
 	chatID := "pico:" + sessionID