fix(tools): propagate tool registry to subagents

pkg/agent/loop.go

@@ -239,6 +239,11 @@ func registerSharedTools(
 		if (spawnEnabled || spawnStatusEnabled) && cfg.Tools.IsToolEnabled("subagent") {
 			subagentManager := tools.NewSubagentManager(provider, agent.Model, agent.Workspace)
 			subagentManager.SetLLMOptions(agent.MaxTokens, agent.Temperature)
+			// Clone the parent's tool registry so subagents can use all
+			// tools registered so far (file, web, etc.) but NOT spawn/
+			// spawn_status which are added below — preventing recursive
+			// subagent spawning.
+			subagentManager.SetTools(agent.Tools.Clone())
 			if spawnEnabled {
 				spawnTool := tools.NewSpawnTool(subagentManager)
 				currentAgentID := agentID

pkg/tools/registry.go

@@ -303,6 +303,27 @@ func (r *ToolRegistry) List() []string {
 	return r.sortedToolNames()
 }
 
+// Clone creates an independent copy of the registry containing the same tool
+// entries (shallow copy of each ToolEntry). This is used to give subagents a
+// snapshot of the parent agent's tools without sharing the same registry —
+// tools registered on the parent after cloning (e.g. spawn, spawn_status)
+// will NOT be visible to the clone, preventing recursive subagent spawning.
+func (r *ToolRegistry) Clone() *ToolRegistry {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	clone := &ToolRegistry{
+		tools: make(map[string]*ToolEntry, len(r.tools)),
+	}
+	for name, entry := range r.tools {
+		clone.tools[name] = &ToolEntry{
+			Tool:   entry.Tool,
+			IsCore: entry.IsCore,
+			TTL:    entry.TTL,
+		}
+	}
+	return clone
+}
+
 // Count returns the number of registered tools.
 func (r *ToolRegistry) Count() int {
 	r.mu.RLock()

pkg/tools/registry_test.go

@@ -335,6 +335,71 @@ func TestToolToSchema(t *testing.T) {
 	}
 }
 
+func TestToolRegistry_Clone(t *testing.T) {
+	r := NewToolRegistry()
+	r.Register(newMockTool("read_file", "reads files"))
+	r.Register(newMockTool("exec", "runs commands"))
+	r.Register(newMockTool("web_search", "searches the web"))
+
+	clone := r.Clone()
+
+	// Clone should have the same tools
+	if clone.Count() != 3 {
+		t.Errorf("expected clone to have 3 tools, got %d", clone.Count())
+	}
+	for _, name := range []string{"read_file", "exec", "web_search"} {
+		if _, ok := clone.Get(name); !ok {
+			t.Errorf("expected clone to have tool %q", name)
+		}
+	}
+
+	// Registering on parent should NOT affect clone
+	r.Register(newMockTool("spawn", "spawns subagent"))
+	if r.Count() != 4 {
+		t.Errorf("expected parent to have 4 tools, got %d", r.Count())
+	}
+	if clone.Count() != 3 {
+		t.Errorf("expected clone to still have 3 tools after parent mutation, got %d", clone.Count())
+	}
+	if _, ok := clone.Get("spawn"); ok {
+		t.Error("expected clone NOT to have 'spawn' tool registered on parent after cloning")
+	}
+
+	// Registering on clone should NOT affect parent
+	clone.Register(newMockTool("custom", "custom tool"))
+	if clone.Count() != 4 {
+		t.Errorf("expected clone to have 4 tools, got %d", clone.Count())
+	}
+	if _, ok := r.Get("custom"); ok {
+		t.Error("expected parent NOT to have 'custom' tool registered on clone")
+	}
+}
+
+func TestToolRegistry_Clone_Empty(t *testing.T) {
+	r := NewToolRegistry()
+	clone := r.Clone()
+	if clone.Count() != 0 {
+		t.Errorf("expected empty clone, got count %d", clone.Count())
+	}
+}
+
+func TestToolRegistry_Clone_PreservesHiddenToolState(t *testing.T) {
+	r := NewToolRegistry()
+	r.RegisterHidden(newMockTool("mcp_tool", "dynamic MCP tool"))
+
+	clone := r.Clone()
+
+	// Hidden tools with TTL=0 should not be gettable (same behavior as parent)
+	if _, ok := clone.Get("mcp_tool"); ok {
+		t.Error("expected hidden tool with TTL=0 to be invisible in clone")
+	}
+
+	// But the entry should exist (count includes hidden tools)
+	if clone.Count() != 1 {
+		t.Errorf("expected clone count 1 (hidden entry exists), got %d", clone.Count())
+	}
+}
+
 func TestToolRegistry_ConcurrentAccess(t *testing.T) {
 	r := NewToolRegistry()
 	var wg sync.WaitGroup