refactor: implement DelegateToAgentTool with discriminated union (#14769)

packages/core/src/config/config.test.ts

@@ -138,8 +138,12 @@ vi.mock('../agents/registry.js', () => {
   return { AgentRegistry: AgentRegistryMock };
 });
 
-vi.mock('../agents/subagent-tool-wrapper.js', () => ({
-  SubagentToolWrapper: vi.fn(),
+vi.mock('../agents/delegate-to-agent-tool.js', () => ({
+  DelegateToAgentTool: vi.fn(),
+}));
+
+vi.mock('../resources/resource-registry.js', () => ({
+  ResourceRegistry: vi.fn(),
 }));
 
 const mockCoreEvents = vi.hoisted(() => ({
@@ -842,11 +846,11 @@ describe('Server Config (config.ts)', () => {
         mockAgentDefinition,
       );
 
-      const SubagentToolWrapperMock = (
-        (await vi.importMock('../agents/subagent-tool-wrapper.js')) as {
-          SubagentToolWrapper: Mock;
+      const DelegateToAgentToolMock = (
+        (await vi.importMock('../agents/delegate-to-agent-tool.js')) as {
+          DelegateToAgentTool: Mock;
         }
-      ).SubagentToolWrapper;
+      ).DelegateToAgentTool;
 
       await config.initialize();
 
@@ -856,16 +860,16 @@ describe('Server Config (config.ts)', () => {
         }
       ).ToolRegistry.prototype.registerTool;
 
-      expect(SubagentToolWrapperMock).toHaveBeenCalledTimes(1);
-      expect(SubagentToolWrapperMock).toHaveBeenCalledWith(
-        mockAgentDefinition,
+      expect(DelegateToAgentToolMock).toHaveBeenCalledTimes(1);
+      expect(DelegateToAgentToolMock).toHaveBeenCalledWith(
+        expect.anything(), // AgentRegistry
         config,
         undefined,
       );
 
       const calls = registerToolMock.mock.calls;
       const registeredWrappers = calls.filter(
-        (call) => call[0] instanceof SubagentToolWrapperMock,
+        (call) => call[0] instanceof DelegateToAgentToolMock,
       );
       expect(registeredWrappers).toHaveLength(1);
     });
@@ -877,15 +881,15 @@ describe('Server Config (config.ts)', () => {
       };
       const config = new Config(params);
 
-      const SubagentToolWrapperMock = (
-        (await vi.importMock('../agents/subagent-tool-wrapper.js')) as {
-          SubagentToolWrapper: Mock;
+      const DelegateToAgentToolMock = (
+        (await vi.importMock('../agents/delegate-to-agent-tool.js')) as {
+          DelegateToAgentTool: Mock;
         }
-      ).SubagentToolWrapper;
+      ).DelegateToAgentTool;
 
       await config.initialize();
 
-      expect(SubagentToolWrapperMock).not.toHaveBeenCalled();
+      expect(DelegateToAgentToolMock).not.toHaveBeenCalled();
     });
 
     it('should not set default codebase investigator model in config (defaults in registry)', () => {

packages/core/src/config/config.ts

@@ -84,7 +84,8 @@ import { getCodeAssistServer } from '../code_assist/codeAssist.js';
 import type { Experiments } from '../code_assist/experiments/experiments.js';
 import { AgentRegistry } from '../agents/registry.js';
 import { setGlobalProxy } from '../utils/fetch.js';
-import { SubagentToolWrapper } from '../agents/subagent-tool-wrapper.js';
+import { DelegateToAgentTool } from '../agents/delegate-to-agent-tool.js';
+import { DELEGATE_TO_AGENT_TOOL_NAME } from '../tools/tool-names.js';
 import { getExperiments } from '../code_assist/experiments/experiments.js';
 import { ExperimentFlags } from '../code_assist/experiments/flagNames.js';
 import { debugLogger } from '../utils/debugLogger.js';
@@ -1571,26 +1572,24 @@ export class Config {
     }
 
     // Register Subagents as Tools
-    if (this.getCodebaseInvestigatorSettings().enabled) {
-      const definition = this.agentRegistry.getDefinition(
-        'codebase_investigator',
-      );
-      if (definition) {
-        // We must respect the main allowed/exclude lists for agents too.
-        const allowedTools = this.getAllowedTools();
+    // Register DelegateToAgentTool if agents are enabled
+    if (
+      this.isAgentsEnabled() ||
+      this.getCodebaseInvestigatorSettings().enabled
+    ) {
+      // Check if the delegate tool itself is allowed (if allowedTools is set)
+      const allowedTools = this.getAllowedTools();
+      const isAllowed =
+        !allowedTools || allowedTools.includes(DELEGATE_TO_AGENT_TOOL_NAME);
 
-        const isAllowed =
-          !allowedTools || allowedTools.includes(definition.name);
-
-        if (isAllowed) {
-          const messageBusEnabled = this.getEnableMessageBusIntegration();
-          const wrapper = new SubagentToolWrapper(
-            definition,
-            this,
-            messageBusEnabled ? this.getMessageBus() : undefined,
-          );
-          registry.registerTool(wrapper);
-        }
+      if (isAllowed) {
+        const messageBusEnabled = this.getEnableMessageBusIntegration();
+        const delegateTool = new DelegateToAgentTool(
+          this.agentRegistry,
+          this,
+          messageBusEnabled ? this.getMessageBus() : undefined,
+        );
+        registry.registerTool(delegateTool);
       }
     }