fix(patch): cherry-pick b2d6dc4 to release/v0.35.0-preview.4-pr-23546 [CONFLICTS] (#23585)

Co-authored-by: Abhi <43648792+abhipatel12@users.noreply.github.com>
Co-authored-by: Abhi <abhipatel@google.com>

packages/core/src/agents/registry.ts

@@ -44,6 +44,7 @@ export class AgentRegistry {
   private readonly agents = new Map<string, AgentDefinition<any>>();
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   private readonly allDefinitions = new Map<string, AgentDefinition<any>>();
+  private readonly builtInAgents = new Set<string>();
 
   constructor(private readonly config: Config) {}
 
@@ -56,6 +57,13 @@ export class AgentRegistry {
     await this.loadAgents();
   }
 
+  /**
+   * Returns true if the agent is a built-in agent.
+   */
+  isBuiltIn(name: string): boolean {
+    return this.builtInAgents.has(name);
+  }
+
   private onModelChanged = () => {
     this.refreshAgents().catch((e) => {
       debugLogger.error(
@@ -240,15 +248,25 @@ export class AgentRegistry {
   }
 
   private loadBuiltInAgents(): void {
-    this.registerLocalAgent(CodebaseInvestigatorAgent(this.config));
-    this.registerLocalAgent(CliHelpAgent(this.config));
-    this.registerLocalAgent(GeneralistAgent(this.config));
+    const codebaseAgent = CodebaseInvestigatorAgent(this.config);
+    this.builtInAgents.add(codebaseAgent.name);
+    this.registerLocalAgent(codebaseAgent);
+
+    const helpAgent = CliHelpAgent(this.config);
+    this.builtInAgents.add(helpAgent.name);
+    this.registerLocalAgent(helpAgent);
+
+    const generalistAgent = GeneralistAgent(this.config);
+    this.builtInAgents.add(generalistAgent.name);
+    this.registerLocalAgent(generalistAgent);
 
     // Register the browser agent if enabled in settings.
     // Tools are configured dynamically at invocation time via browserAgentFactory.
     const browserConfig = this.config.getBrowserAgentConfig();
     if (browserConfig.enabled) {
-      this.registerLocalAgent(BrowserAgentDefinition(this.config));
+      const browserAgent = BrowserAgentDefinition(this.config);
+      this.builtInAgents.add(browserAgent.name);
+      this.registerLocalAgent(browserAgent);
     }
   }
 

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

@@ -185,6 +185,7 @@ vi.mock('../agents/registry.js', () => {
   AgentRegistryMock.prototype.initialize = vi.fn();
   AgentRegistryMock.prototype.getAllDefinitions = vi.fn(() => []);
   AgentRegistryMock.prototype.getDefinition = vi.fn();
+  AgentRegistryMock.prototype.isBuiltIn = vi.fn();
   return { AgentRegistry: AgentRegistryMock };
 });
 
@@ -1262,6 +1263,9 @@ describe('Server Config (config.ts)', () => {
       AgentRegistryMock.prototype.getAllDefinitions.mockReturnValue([
         mockAgentDefinition,
       ]);
+      AgentRegistryMock.prototype.isBuiltIn.mockImplementation(
+        (name: string) => name === 'codebase_investigator',
+      );
 
       const SubAgentToolMock = (
         (await vi.importMock('../agents/subagent-tool.js')) as {
@@ -1317,6 +1321,9 @@ describe('Server Config (config.ts)', () => {
       AgentRegistryMock.prototype.getAllDefinitions.mockReturnValue([
         mockAgentDefinition,
       ]);
+      AgentRegistryMock.prototype.isBuiltIn.mockImplementation(
+        (name: string) => name === 'codebase_investigator',
+      );
 
       const SubAgentToolMock = (
         (await vi.importMock('../agents/subagent-tool.js')) as {

packages/core/src/config/config.ts

@@ -951,7 +951,7 @@ export class Config implements McpContext, AgentLoopContext {
     this.model = params.model;
     this.disableLoopDetection = params.disableLoopDetection ?? false;
     this._activeModel = params.model;
-    this.enableAgents = params.enableAgents ?? true;
+    this.enableAgents = params.enableAgents ?? false;
     this.agents = params.agents ?? {};
     this.disableLLMCorrection = params.disableLLMCorrection ?? true;
     this.planEnabled = params.plan ?? true;
@@ -3196,7 +3196,8 @@ export class Config implements McpContext, AgentLoopContext {
     for (const definition of definitions) {
       try {
         if (
-          !this.isAgentsEnabled() ||
+          (!this.isAgentsEnabled() &&
+            !this.agentRegistry.isBuiltIn(definition.name)) ||
           agentsOverrides[definition.name]?.enabled === false
         ) {
           continue;