feat(subagent): support agent_id on sync subagent

pkg/agent/agent_init.go

@@ -329,6 +329,18 @@ func registerSharedTools(
 				// Also register the synchronous subagent tool
 				subagentTool := tools.NewSubagentTool(subagentManager)
 				subagentTool.SetSpawner(NewSubTurnSpawner(al))
+				subagentTool.SetAllowlistChecker(func(targetAgentID string) bool {
+					return registry.CanSpawnSubagent(currentAgentID, targetAgentID)
+				})
+				subagentTool.SetTargetModelResolver(func(targetAgentID string) string {
+					if targetAgentID == "" {
+						return agent.Model
+					}
+					if targetAgent, ok := al.GetRegistry().GetAgent(targetAgentID); ok {
+						return targetAgent.Model
+					}
+					return agent.Model
+				})
 				agent.Tools.Register(subagentTool)
 			}
 			if spawnStatusEnabled {

pkg/tools/subagent.go

@@ -337,10 +337,12 @@ func (sm *SubagentManager) ListTaskCopies() []SubagentTask {
 // SubagentTool executes a subagent task synchronously and returns the result.
 // It directly calls SubTurnSpawner with Async=false for synchronous execution.
 type SubagentTool struct {
-	spawner      SubTurnSpawner
-	defaultModel string
-	maxTokens    int
-	temperature  float64
+	spawner             SubTurnSpawner
+	defaultModel        string
+	maxTokens           int
+	temperature         float64
+	allowlistCheck      func(targetAgentID string) bool
+	targetModelResolver func(targetAgentID string) string
 }
 
 func NewSubagentTool(manager *SubagentManager) *SubagentTool {
@@ -359,6 +361,14 @@ func (t *SubagentTool) SetSpawner(spawner SubTurnSpawner) {
 	t.spawner = spawner
 }
 
+func (t *SubagentTool) SetAllowlistChecker(check func(targetAgentID string) bool) {
+	t.allowlistCheck = check
+}
+
+func (t *SubagentTool) SetTargetModelResolver(resolver func(targetAgentID string) string) {
+	t.targetModelResolver = resolver
+}
+
 func (t *SubagentTool) Name() string {
 	return "subagent"
 }
@@ -379,6 +389,10 @@ func (t *SubagentTool) Parameters() map[string]any {
 				"type":        "string",
 				"description": "Optional short label for the task (for display)",
 			},
+			"agent_id": map[string]any{
+				"type":        "string",
+				"description": "Optional target agent ID to delegate the task to",
+			},
 		},
 		"required": []string{"task"},
 	}
@@ -391,6 +405,17 @@ func (t *SubagentTool) Execute(ctx context.Context, args map[string]any) *ToolRe
 	}
 
 	label, _ := args["label"].(string)
+	agentID, _ := args["agent_id"].(string)
+	if agentID != "" && t.allowlistCheck != nil && !t.allowlistCheck(agentID) {
+		return ErrorResult(fmt.Sprintf("Not allowed to target agent '%s'", agentID))
+	}
+
+	modelToUse := t.defaultModel
+	if agentID != "" && t.targetModelResolver != nil {
+		if resolved := t.targetModelResolver(agentID); resolved != "" {
+			modelToUse = resolved
+		}
+	}
 
 	// Build system prompt for subagent
 	systemPrompt := fmt.Sprintf(
@@ -413,7 +438,7 @@ Task: %s`,
 	// Use spawner if available (direct SpawnSubTurn call)
 	if t.spawner != nil {
 		result, err := t.spawner.SpawnSubTurn(ctx, SubTurnConfig{
-			Model:        t.defaultModel,
+			Model:        modelToUse,
 			Tools:        nil, // Will inherit from parent via context
 			SystemPrompt: systemPrompt,
 			MaxTokens:    t.maxTokens,

pkg/tools/subagent_targeting_test.go

@@ -0,0 +1,75 @@
+package tools
+
+import (
+	"context"
+	"testing"
+)
+
+type capturingSubTurnSpawner struct {
+	lastCfg SubTurnConfig
+}
+
+func (s *capturingSubTurnSpawner) SpawnSubTurn(_ context.Context, cfg SubTurnConfig) (*ToolResult, error) {
+	s.lastCfg = cfg
+	return &ToolResult{ForLLM: "ok", ForUser: "ok"}, nil
+}
+
+func TestSubagentToolRejectsDisallowedAgentID(t *testing.T) {
+	tool := &SubagentTool{defaultModel: "main-model"}
+	tool.SetAllowlistChecker(func(targetAgentID string) bool {
+		return targetAgentID != "code"
+	})
+
+	result := tool.Execute(context.Background(), map[string]any{
+		"task":     "do something",
+		"agent_id": "code",
+	})
+
+	if result == nil || !result.IsError {
+		t.Fatalf("expected error result, got %#v", result)
+	}
+}
+
+func TestSubagentToolUsesResolvedTargetModelForAgentID(t *testing.T) {
+	spawner := &capturingSubTurnSpawner{}
+	tool := &SubagentTool{defaultModel: "main-model"}
+	tool.SetSpawner(spawner)
+	tool.SetAllowlistChecker(func(targetAgentID string) bool {
+		return targetAgentID == "code"
+	})
+	tool.SetTargetModelResolver(func(targetAgentID string) string {
+		if targetAgentID == "code" {
+			return "code-model"
+		}
+		return ""
+	})
+
+	result := tool.Execute(context.Background(), map[string]any{
+		"task":     "do something",
+		"agent_id": "code",
+	})
+
+	if result == nil || result.IsError {
+		t.Fatalf("expected success result, got %#v", result)
+	}
+	if spawner.lastCfg.Model != "code-model" {
+		t.Fatalf("expected model code-model, got %q", spawner.lastCfg.Model)
+	}
+}
+
+func TestSubagentToolFallsBackToDefaultModelWithoutAgentID(t *testing.T) {
+	spawner := &capturingSubTurnSpawner{}
+	tool := &SubagentTool{defaultModel: "main-model"}
+	tool.SetSpawner(spawner)
+
+	result := tool.Execute(context.Background(), map[string]any{
+		"task": "do something",
+	})
+
+	if result == nil || result.IsError {
+		t.Fatalf("expected success result, got %#v", result)
+	}
+	if spawner.lastCfg.Model != "main-model" {
+		t.Fatalf("expected model main-model, got %q", spawner.lastCfg.Model)
+	}
+}