diff --git a/pkg/agent/loop.go b/pkg/agent/loop.go
index 9ce5480..90e6659 100644
--- a/pkg/agent/loop.go
+++ b/pkg/agent/loop.go
@@ -19,6 +19,7 @@ import (
 
 	"github.com/sipeed/picoclaw/pkg/bus"
 	"github.com/sipeed/picoclaw/pkg/config"
+	"github.com/sipeed/picoclaw/pkg/constants"
 	"github.com/sipeed/picoclaw/pkg/logger"
 	"github.com/sipeed/picoclaw/pkg/providers"
 	"github.com/sipeed/picoclaw/pkg/session"
@@ -281,8 +282,7 @@ func (al *AgentLoop) processSystemMessage(ctx context.Context, msg bus.InboundMe
 	}
 
 	// Skip internal channels - only log, don't send to user
-	internalChannels := map[string]bool{"cli": true, "system": true, "subagent": true}
-	if internalChannels[originChannel] {
+	if constants.IsInternalChannel(originChannel) {
 		logger.InfoCF("agent", "Subagent completed (internal channel)",
 			map[string]interface{}{
 				"sender_id":    msg.SenderID,
@@ -311,8 +311,7 @@ func (al *AgentLoop) runAgentLoop(ctx context.Context, opts processOptions) (str
 	// 0. Record last channel for heartbeat notifications (skip internal channels)
 	if opts.Channel != "" && opts.ChatID != "" {
 		// Don't record internal channels (cli, system, subagent)
-		internalChannels := map[string]bool{"cli": true, "system": true, "subagent": true}
-		if !internalChannels[opts.Channel] {
+		if !constants.IsInternalChannel(opts.Channel) {
 			channelKey := fmt.Sprintf("%s:%s", opts.Channel, opts.ChatID)
 			if err := al.RecordLastChannel(channelKey); err != nil {
 				logger.WarnCF("agent", "Failed to record last channel: %v", map[string]interface{}{"error": err.Error()})
@@ -402,18 +401,7 @@ func (al *AgentLoop) runLLMIteration(ctx context.Context, messages []providers.M
 			})
 
 		// Build tool definitions
-		toolDefs := al.tools.GetDefinitions()
-		providerToolDefs := make([]providers.ToolDefinition, 0, len(toolDefs))
-		for _, td := range toolDefs {
-			providerToolDefs = append(providerToolDefs, providers.ToolDefinition{
-				Type: td["type"].(string),
-				Function: providers.ToolFunctionDefinition{
-					Name:        td["function"].(map[string]interface{})["name"].(string),
-					Description: td["function"].(map[string]interface{})["description"].(string),
-					Parameters:  td["function"].(map[string]interface{})["parameters"].(map[string]interface{}),
-				},
-			})
-		}
+		providerToolDefs := al.tools.ToProviderDefs()
 
 		// Log LLM request details
 		logger.DebugCF("agent", "LLM request",
diff --git a/pkg/channels/manager.go b/pkg/channels/manager.go
index 06e746c..772551a 100644
--- a/pkg/channels/manager.go
+++ b/pkg/channels/manager.go
@@ -13,6 +13,7 @@ import (
 
 	"github.com/sipeed/picoclaw/pkg/bus"
 	"github.com/sipeed/picoclaw/pkg/config"
+	"github.com/sipeed/picoclaw/pkg/constants"
 	"github.com/sipeed/picoclaw/pkg/logger"
 )
 
@@ -218,9 +219,6 @@ func (m *Manager) StopAll(ctx context.Context) error {
 func (m *Manager) dispatchOutbound(ctx context.Context) {
 	logger.InfoC("channels", "Outbound dispatcher started")
 
-	// Internal channels that don't have actual handlers
-	internalChannels := map[string]bool{"cli": true, "system": true, "subagent": true}
-
 	for {
 		select {
 		case <-ctx.Done():
@@ -233,7 +231,7 @@ func (m *Manager) dispatchOutbound(ctx context.Context) {
 			}
 
 			// Silently skip internal channels
-			if internalChannels[msg.Channel] {
+			if constants.IsInternalChannel(msg.Channel) {
 				continue
 			}
 
diff --git a/pkg/constants/channels.go b/pkg/constants/channels.go
new file mode 100644
index 0000000..3e3df38
--- /dev/null
+++ b/pkg/constants/channels.go
@@ -0,0 +1,15 @@
+// Package constants provides shared constants across the codebase.
+package constants
+
+// InternalChannels defines channels that are used for internal communication
+// and should not be exposed to external users or recorded as last active channel.
+var InternalChannels = map[string]bool{
+	"cli":      true,
+	"system":   true,
+	"subagent": true,
+}
+
+// IsInternalChannel returns true if the channel is an internal channel.
+func IsInternalChannel(channel string) bool {
+	return InternalChannels[channel]
+}
diff --git a/pkg/heartbeat/service.go b/pkg/heartbeat/service.go
index abe8925..a090cda 100644
--- a/pkg/heartbeat/service.go
+++ b/pkg/heartbeat/service.go
@@ -15,6 +15,7 @@ import (
 	"time"
 
 	"github.com/sipeed/picoclaw/pkg/bus"
+	"github.com/sipeed/picoclaw/pkg/constants"
 	"github.com/sipeed/picoclaw/pkg/logger"
 	"github.com/sipeed/picoclaw/pkg/state"
 	"github.com/sipeed/picoclaw/pkg/tools"
@@ -332,8 +333,7 @@ func (hs *HeartbeatService) parseLastChannel(lastChannel string) (platform, user
 	platform, userID = parts[0], parts[1]
 
 	// Skip internal channels
-	internalChannels := map[string]bool{"cli": true, "system": true, "subagent": true}
-	if internalChannels[platform] {
+	if constants.IsInternalChannel(platform) {
 		hs.logInfo("Skipping internal channel: %s", platform)
 		return "", ""
 	}
diff --git a/pkg/tools/registry.go b/pkg/tools/registry.go
index 5dea7d3..c8cf928 100644
--- a/pkg/tools/registry.go
+++ b/pkg/tools/registry.go
@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/sipeed/picoclaw/pkg/logger"
+	"github.com/sipeed/picoclaw/pkg/providers"
 )
 
 type ToolRegistry struct {
@@ -111,6 +112,38 @@ func (r *ToolRegistry) GetDefinitions() []map[string]interface{} {
 	return definitions
 }
 
+// ToProviderDefs converts tool definitions to provider-compatible format.
+// This is the format expected by LLM provider APIs.
+func (r *ToolRegistry) ToProviderDefs() []providers.ToolDefinition {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	definitions := make([]providers.ToolDefinition, 0, len(r.tools))
+	for _, tool := range r.tools {
+		schema := ToolToSchema(tool)
+
+		// Safely extract nested values with type checks
+		fn, ok := schema["function"].(map[string]interface{})
+		if !ok {
+			continue
+		}
+
+		name, _ := fn["name"].(string)
+		desc, _ := fn["description"].(string)
+		params, _ := fn["parameters"].(map[string]interface{})
+
+		definitions = append(definitions, providers.ToolDefinition{
+			Type: "function",
+			Function: providers.ToolFunctionDefinition{
+				Name:        name,
+				Description: desc,
+				Parameters:  params,
+			},
+		})
+	}
+	return definitions
+}
+
 // List returns a list of all registered tool names.
 func (r *ToolRegistry) List() []string {
 	r.mu.RLock()
diff --git a/pkg/tools/subagent.go b/pkg/tools/subagent.go
index 731d136..97b1303 100644
--- a/pkg/tools/subagent.go
+++ b/pkg/tools/subagent.go
@@ -264,7 +264,7 @@ func (t *SubagentTool) Execute(ctx context.Context, args map[string]interface{})
 		return ErrorResult("Subagent manager not configured").WithError(fmt.Errorf("manager is nil"))
 	}
 
-	// Execute subagent task synchronously via direct provider call
+	// Build messages for subagent
 	messages := []providers.Message{
 		{
 			Role:    "system",
@@ -276,36 +276,48 @@ func (t *SubagentTool) Execute(ctx context.Context, args map[string]interface{})
 		},
 	}
 
-	response, err := t.manager.provider.Chat(ctx, messages, nil, t.manager.defaultModel, map[string]interface{}{
-		"max_tokens": 4096,
-	})
+	// Use RunToolLoop to execute with tools (same as async SpawnTool)
+	sm := t.manager
+	sm.mu.RLock()
+	tools := sm.tools
+	maxIter := sm.maxIterations
+	sm.mu.RUnlock()
+
+	loopResult, err := RunToolLoop(ctx, ToolLoopConfig{
+		Provider:      sm.provider,
+		Model:         sm.defaultModel,
+		Tools:         tools,
+		MaxIterations: maxIter,
+		LLMOptions: map[string]any{
+			"max_tokens":  4096,
+			"temperature": 0.7,
+		},
+	}, messages, t.originChannel, t.originChatID)
 
 	if err != nil {
 		return ErrorResult(fmt.Sprintf("Subagent execution failed: %v", err)).WithError(err)
 	}
 
 	// ForUser: Brief summary for user (truncated if too long)
-	userContent := response.Content
+	userContent := loopResult.Content
 	maxUserLen := 500
 	if len(userContent) > maxUserLen {
 		userContent = userContent[:maxUserLen] + "..."
 	}
 
 	// ForLLM: Full execution details
-	llmContent := fmt.Sprintf("Subagent task completed:\nLabel: %s\nResult: %s",
-		func() string {
-			if label != "" {
-				return label
-			}
-			return "(unnamed)"
-		}(),
-		response.Content)
+	labelStr := label
+	if labelStr == "" {
+		labelStr = "(unnamed)"
+	}
+	llmContent := fmt.Sprintf("Subagent task completed:\nLabel: %s\nIterations: %d\nResult: %s",
+		labelStr, loopResult.Iterations, loopResult.Content)
 
 	return &ToolResult{
 		ForLLM:  llmContent,
-		ForUser:  userContent,
-		Silent:    false,
-		IsError:   false,
-		Async:     false,
+		ForUser: userContent,
+		Silent:  false,
+		IsError: false,
+		Async:   false,
 	}
 }
diff --git a/pkg/tools/toolloop.go b/pkg/tools/toolloop.go
index 4755ddc..1302079 100644
--- a/pkg/tools/toolloop.go
+++ b/pkg/tools/toolloop.go
@@ -49,18 +49,7 @@ func RunToolLoop(ctx context.Context, config ToolLoopConfig, messages []provider
 		// 1. Build tool definitions
 		var providerToolDefs []providers.ToolDefinition
 		if config.Tools != nil {
-			toolDefs := config.Tools.GetDefinitions()
-			providerToolDefs = make([]providers.ToolDefinition, 0, len(toolDefs))
-			for _, td := range toolDefs {
-				providerToolDefs = append(providerToolDefs, providers.ToolDefinition{
-					Type: td["type"].(string),
-					Function: providers.ToolFunctionDefinition{
-						Name:        td["function"].(map[string]any)["name"].(string),
-						Description: td["function"].(map[string]any)["description"].(string),
-						Parameters:  td["function"].(map[string]any)["parameters"].(map[string]any),
-					},
-				})
-			}
+			providerToolDefs = config.Tools.ToProviderDefs()
 		}
 
 		// 2. Set default LLM options