fix tool-call 400: enforce per-session run lock across all entry paths

pkg/agent/loop.go

@@ -55,6 +55,8 @@ type AgentLoop struct {
 	running                 bool
 	intentMu                sync.RWMutex
 	intentHints             map[string]string
+	sessionRunMu            sync.Mutex
+	sessionRunLocks         map[string]*sync.Mutex
 }
 
 type executionTxnState struct {
@@ -236,6 +238,7 @@ func NewAgentLoop(cfg *config.Config, msgBus *bus.MessageBus, provider providers
 		audit:                 newTriggerAudit(workspace),
 		running:               false,
 		intentHints:           map[string]string{},
+		sessionRunLocks:       map[string]*sync.Mutex{},
 	}
 
 	// 注入递归运行逻辑，使 subagent 具备 full tool-calling 能力
@@ -295,6 +298,22 @@ func (al *AgentLoop) buildSessionShards(ctx context.Context) []chan bus.InboundM
 	return shards
 }
 
+func (al *AgentLoop) lockSessionRun(sessionKey string) func() {
+	key := strings.TrimSpace(sessionKey)
+	if key == "" {
+		key = "default"
+	}
+	al.sessionRunMu.Lock()
+	mu, ok := al.sessionRunLocks[key]
+	if !ok {
+		mu = &sync.Mutex{}
+		al.sessionRunLocks[key] = mu
+	}
+	al.sessionRunMu.Unlock()
+	mu.Lock()
+	return func() { mu.Unlock() }
+}
+
 func (al *AgentLoop) processInbound(ctx context.Context, msg bus.InboundMessage) {
 	response, err := al.processMessage(ctx, msg)
 	if err != nil {
@@ -419,6 +438,8 @@ func (al *AgentLoop) ProcessDirect(ctx context.Context, content, sessionKey stri
 }
 
 func (al *AgentLoop) processMessage(ctx context.Context, msg bus.InboundMessage) (string, error) {
+	unlock := al.lockSessionRun(msg.SessionKey)
+	defer unlock()
 	// Add message preview to log
 	preview := truncate(msg.Content, 80)
 	logger.InfoCF("agent", fmt.Sprintf("Processing message from %s:%s: %s", msg.Channel, msg.SenderID, preview),