diff --git a/pkg/channels/pico/pico.go b/pkg/channels/pico/pico.go
index c948f9d4a..f3ba55a92 100644
--- a/pkg/channels/pico/pico.go
+++ b/pkg/channels/pico/pico.go
@@ -59,7 +59,6 @@ type PicoChannel struct {
 	connections        map[string]*picoConn            // connID -> *picoConn
 	sessionConnections map[string]map[string]*picoConn // sessionID -> connID -> *picoConn
 	connsMu            sync.RWMutex
-	connCount          int
 	ctx                context.Context
 	cancel             context.CancelFunc
 }
@@ -103,8 +102,8 @@ func NewPicoChannel(cfg config.PicoConfig, messageBus *bus.MessageBus) (*PicoCha
 func (c *PicoChannel) createAndAddConnection(conn *websocket.Conn, sessionID string, maxConns int) (*picoConn, error) {
 	c.connsMu.Lock()
 	defer c.connsMu.Unlock()
-	if c.connCount >= maxConns {
-		return nil, channels.ErrSendFailed
+	if len(c.connections) >= maxConns {
+		return nil, channels.ErrTemporary
 	}
 
 	var connID string
@@ -128,7 +127,6 @@ func (c *PicoChannel) createAndAddConnection(conn *websocket.Conn, sessionID str
 		c.sessionConnections[pc.sessionID] = bySession
 	}
 	bySession[pc.id] = pc
-	c.connCount++
 
 	return pc, nil
 }
@@ -150,7 +148,6 @@ func (c *PicoChannel) removeConnection(connID string) *picoConn {
 			delete(c.sessionConnections, pc.sessionID)
 		}
 	}
-	c.connCount--
 
 	return pc
 }
@@ -166,7 +163,6 @@ func (c *PicoChannel) takeAllConnections() []*picoConn {
 	}
 	clear(c.connections)
 	clear(c.sessionConnections)
-	c.connCount = 0
 
 	return all
 }
@@ -192,7 +188,7 @@ func (c *PicoChannel) sessionConnectionsSnapshot(sessionID string) []*picoConn {
 func (c *PicoChannel) currentConnCount() int {
 	c.connsMu.RLock()
 	defer c.connsMu.RUnlock()
-	return c.connCount
+	return len(c.connections)
 }
 
 // Start implements Channel.
diff --git a/pkg/channels/pico/pico_test.go b/pkg/channels/pico/pico_test.go
new file mode 100644
index 000000000..e712767ad
--- /dev/null
+++ b/pkg/channels/pico/pico_test.go
@@ -0,0 +1,144 @@
+package pico
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sync"
+	"testing"
+
+	"github.com/sipeed/picoclaw/pkg/bus"
+	"github.com/sipeed/picoclaw/pkg/channels"
+	"github.com/sipeed/picoclaw/pkg/config"
+)
+
+func newTestPicoChannel(t *testing.T) *PicoChannel {
+	t.Helper()
+
+	cfg := config.PicoConfig{}
+	cfg.SetToken("test-token")
+	ch, err := NewPicoChannel(cfg, bus.NewMessageBus())
+	if err != nil {
+		t.Fatalf("NewPicoChannel: %v", err)
+	}
+
+	ch.ctx = context.Background()
+	return ch
+}
+
+func TestCreateAndAddConnection_RespectsMaxConnectionsConcurrently(t *testing.T) {
+	ch := newTestPicoChannel(t)
+
+	const (
+		maxConns   = 5
+		goroutines = 64
+		sessionID  = "session-a"
+	)
+
+	var wg sync.WaitGroup
+	var mu sync.Mutex
+	successCount := 0
+	errCount := 0
+
+	wg.Add(goroutines)
+	for i := 0; i < goroutines; i++ {
+		go func() {
+			defer wg.Done()
+
+			pc, err := ch.createAndAddConnection(nil, sessionID, maxConns)
+			mu.Lock()
+			defer mu.Unlock()
+
+			if err == nil {
+				successCount++
+				if pc == nil {
+					t.Errorf("pc is nil on success")
+				}
+				return
+			}
+			if !errors.Is(err, channels.ErrTemporary) {
+				t.Errorf("unexpected error: %v", err)
+				return
+			}
+			errCount++
+		}()
+	}
+	wg.Wait()
+
+	if successCount > maxConns {
+		t.Fatalf("successCount=%d > maxConns=%d", successCount, maxConns)
+	}
+	if successCount+errCount != goroutines {
+		t.Fatalf("success=%d err=%d total=%d want=%d", successCount, errCount, successCount+errCount, goroutines)
+	}
+	if got := ch.currentConnCount(); got != maxConns {
+		t.Fatalf("currentConnCount=%d want=%d", got, maxConns)
+	}
+}
+
+func TestRemoveConnection_CleansBothIndexes(t *testing.T) {
+	ch := newTestPicoChannel(t)
+
+	pc, err := ch.createAndAddConnection(nil, "session-cleanup", 10)
+	if err != nil {
+		t.Fatalf("createAndAddConnection: %v", err)
+	}
+
+	removed := ch.removeConnection(pc.id)
+	if removed == nil {
+		t.Fatal("removeConnection returned nil")
+	}
+
+	ch.connsMu.RLock()
+	defer ch.connsMu.RUnlock()
+
+	if _, ok := ch.connections[pc.id]; ok {
+		t.Fatalf("connID %s still exists in connections", pc.id)
+	}
+	if _, ok := ch.sessionConnections[pc.sessionID]; ok {
+		t.Fatalf("session %s still exists in sessionConnections", pc.sessionID)
+	}
+	if got := len(ch.connections); got != 0 {
+		t.Fatalf("len(connections)=%d want=0", got)
+	}
+}
+
+func TestBroadcastToSession_TargetsOnlyRequestedSession(t *testing.T) {
+	ch := newTestPicoChannel(t)
+
+	target := &picoConn{id: "target", sessionID: "s-target"}
+	target.closed.Store(true)
+	ch.addConnForTest(target)
+
+	other := &picoConn{id: "other", sessionID: "s-other"}
+	ch.addConnForTest(other)
+
+	err := ch.broadcastToSession("pico:s-target", newMessage(TypeMessageCreate, map[string]any{"content": "hello"}))
+	if err == nil {
+		t.Fatal("expected send failure due to closed target connection")
+	}
+	if !errors.Is(err, channels.ErrSendFailed) {
+		t.Fatalf("expected ErrSendFailed, got %v", err)
+	}
+}
+
+func (c *PicoChannel) addConnForTest(pc *picoConn) {
+	c.connsMu.Lock()
+	defer c.connsMu.Unlock()
+	if c.connections == nil {
+		c.connections = make(map[string]*picoConn)
+	}
+	if c.sessionConnections == nil {
+		c.sessionConnections = make(map[string]map[string]*picoConn)
+	}
+	if _, exists := c.connections[pc.id]; exists {
+		panic(fmt.Sprintf("duplicate conn id in test: %s", pc.id))
+	}
+	c.connections[pc.id] = pc
+	bySession, ok := c.sessionConnections[pc.sessionID]
+	if !ok {
+		bySession = make(map[string]*picoConn)
+		c.sessionConnections[pc.sessionID] = bySession
+	}
+	bySession[pc.id] = pc
+}