feat: enable subagents (#22386)

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

@@ -1246,7 +1246,7 @@ describe('Server Config (config.ts)', () => {
       const config = new Config(params);
 
       const mockAgentDefinition = {
-        name: 'codebase-investigator',
+        name: 'codebase_investigator',
         description: 'Agent 1',
         instructions: 'Inst 1',
       };
@@ -1294,7 +1294,7 @@ describe('Server Config (config.ts)', () => {
     it('should register subagents as tools even when they are not in allowedTools', async () => {
       const params: ConfigParameters = {
         ...baseParams,
-        allowedTools: ['read_file'], // codebase-investigator is NOT here
+        allowedTools: ['read_file'], // codebase_investigator is NOT here
         agents: {
           overrides: {
             codebase_investigator: { enabled: true },
@@ -1304,7 +1304,7 @@ describe('Server Config (config.ts)', () => {
       const config = new Config(params);
 
       const mockAgentDefinition = {
-        name: 'codebase-investigator',
+        name: 'codebase_investigator',
         description: 'Agent 1',
         instructions: 'Inst 1',
       };

packages/core/src/config/config.ts

@@ -948,7 +948,7 @@ export class Config implements McpContext, AgentLoopContext {
     this.model = params.model;
     this.disableLoopDetection = params.disableLoopDetection ?? false;
     this._activeModel = params.model;
-    this.enableAgents = params.enableAgents ?? false;
+    this.enableAgents = params.enableAgents ?? true;
     this.agents = params.agents ?? {};
     this.disableLLMCorrection = params.disableLLMCorrection ?? true;
     this.planEnabled = params.plan ?? true;
@@ -3147,22 +3147,23 @@ export class Config implements McpContext, AgentLoopContext {
    */
   private registerSubAgentTools(registry: ToolRegistry): void {
     const agentsOverrides = this.getAgentsSettings().overrides ?? {};
-    if (
-      this.isAgentsEnabled() ||
-      agentsOverrides['codebase_investigator']?.enabled !== false ||
-      agentsOverrides['cli_help']?.enabled !== false
-    ) {
-      const definitions = this.agentRegistry.getAllDefinitions();
+    const definitions = this.agentRegistry.getAllDefinitions();
 
-      for (const definition of definitions) {
-        try {
-          const tool = new SubagentTool(definition, this, this.messageBus);
-          registry.registerTool(tool);
-        } catch (e: unknown) {
-          debugLogger.warn(
-            `Failed to register tool for agent ${definition.name}: ${getErrorMessage(e)}`,
-          );
+    for (const definition of definitions) {
+      try {
+        if (
+          !this.isAgentsEnabled() ||
+          agentsOverrides[definition.name]?.enabled === false
+        ) {
+          continue;
         }
+
+        const tool = new SubagentTool(definition, this, this.messageBus);
+        registry.registerTool(tool);
+      } catch (e: unknown) {
+        debugLogger.warn(
+          `Failed to register tool for agent ${definition.name}: ${getErrorMessage(e)}`,
+        );
       }
     }
   }

packages/core/src/services/FolderTrustDiscoveryService.test.ts

@@ -42,6 +42,11 @@ describe('FolderTrustDiscoveryService', () => {
     await fs.mkdir(path.join(skillsDir, 'test-skill'), { recursive: true });
     await fs.writeFile(path.join(skillsDir, 'test-skill', 'SKILL.md'), 'body');
 
+    // Mock agents
+    const agentsDir = path.join(geminiDir, 'agents');
+    await fs.mkdir(agentsDir);
+    await fs.writeFile(path.join(agentsDir, 'test-agent.md'), 'body');
+
     // Mock settings (MCPs, Hooks, and general settings)
     const settings = {
       mcpServers: {
@@ -62,6 +67,7 @@ describe('FolderTrustDiscoveryService', () => {
 
     expect(results.commands).toContain('test-cmd');
     expect(results.skills).toContain('test-skill');
+    expect(results.agents).toContain('test-agent');
     expect(results.mcps).toContain('test-mcp');
     expect(results.hooks).toContain('test-hook');
     expect(results.settings).toContain('general');
@@ -79,9 +85,6 @@ describe('FolderTrustDiscoveryService', () => {
         allowed: ['git'],
         sandbox: false,
       },
-      experimental: {
-        enableAgents: true,
-      },
       security: {
         folderTrust: {
           enabled: false,
@@ -98,9 +101,6 @@ describe('FolderTrustDiscoveryService', () => {
     expect(results.securityWarnings).toContain(
       'This project auto-approves certain tools (tools.allowed).',
     );
-    expect(results.securityWarnings).toContain(
-      'This project enables autonomous agents (enableAgents).',
-    );
     expect(results.securityWarnings).toContain(
       'This project attempts to disable folder trust (security.folderTrust.enabled).',
     );
@@ -158,4 +158,20 @@ describe('FolderTrustDiscoveryService', () => {
     expect(results.discoveryErrors).toHaveLength(0);
     expect(results.settings).toHaveLength(0);
   });
+
+  it('should flag security warning for custom agents', async () => {
+    const geminiDir = path.join(tempDir, GEMINI_DIR);
+    await fs.mkdir(geminiDir, { recursive: true });
+
+    const agentsDir = path.join(geminiDir, 'agents');
+    await fs.mkdir(agentsDir);
+    await fs.writeFile(path.join(agentsDir, 'test-agent.md'), 'body');
+
+    const results = await FolderTrustDiscoveryService.discover(tempDir);
+
+    expect(results.agents).toContain('test-agent');
+    expect(results.securityWarnings).toContain(
+      'This project contains custom agents.',
+    );
+  });
 });

packages/core/src/services/FolderTrustDiscoveryService.ts

@@ -16,6 +16,7 @@ export interface FolderDiscoveryResults {
   mcps: string[];
   hooks: string[];
   skills: string[];
+  agents: string[];
   settings: string[];
   securityWarnings: string[];
   discoveryErrors: string[];
@@ -37,6 +38,7 @@ export class FolderTrustDiscoveryService {
       mcps: [],
       hooks: [],
       skills: [],
+      agents: [],
       settings: [],
       securityWarnings: [],
       discoveryErrors: [],
@@ -50,6 +52,7 @@ export class FolderTrustDiscoveryService {
     await Promise.all([
       this.discoverCommands(geminiDir, results),
       this.discoverSkills(geminiDir, results),
+      this.discoverAgents(geminiDir, results),
       this.discoverSettings(geminiDir, results),
     ]);
 
@@ -99,6 +102,34 @@ export class FolderTrustDiscoveryService {
     }
   }
 
+  private static async discoverAgents(
+    geminiDir: string,
+    results: FolderDiscoveryResults,
+  ) {
+    const agentsDir = path.join(geminiDir, 'agents');
+    if (await this.exists(agentsDir)) {
+      try {
+        const entries = await fs.readdir(agentsDir, { withFileTypes: true });
+        for (const entry of entries) {
+          if (
+            entry.isFile() &&
+            entry.name.endsWith('.md') &&
+            !entry.name.startsWith('_')
+          ) {
+            results.agents.push(path.basename(entry.name, '.md'));
+          }
+        }
+        if (results.agents.length > 0) {
+          results.securityWarnings.push('This project contains custom agents.');
+        }
+      } catch (e) {
+        results.discoveryErrors.push(
+          `Failed to discover agents: ${e instanceof Error ? e.message : String(e)}`,
+        );
+      }
+    }
+  }
+
   private static async discoverSettings(
     geminiDir: string,
     results: FolderDiscoveryResults,
@@ -119,7 +150,7 @@ export class FolderTrustDiscoveryService {
         (key) => !['mcpServers', 'hooks', '$schema'].includes(key),
       );
 
-      results.securityWarnings = this.collectSecurityWarnings(settings);
+      results.securityWarnings.push(...this.collectSecurityWarnings(settings));
 
       const mcpServers = settings['mcpServers'];
       if (this.isRecord(mcpServers)) {
@@ -159,10 +190,6 @@ export class FolderTrustDiscoveryService {
       ? settings['tools']
       : undefined;
 
-    const experimental = this.isRecord(settings['experimental'])
-      ? settings['experimental']
-      : undefined;
-
     const security = this.isRecord(settings['security'])
       ? settings['security']
       : undefined;
@@ -179,10 +206,6 @@ export class FolderTrustDiscoveryService {
         condition: Array.isArray(allowedTools) && allowedTools.length > 0,
         message: 'This project auto-approves certain tools (tools.allowed).',
       },
-      {
-        condition: experimental?.['enableAgents'] === true,
-        message: 'This project enables autonomous agents (enableAgents).',
-      },
       {
         condition: folderTrust?.['enabled'] === false,
         message: