feat(core): Add generalist agent. (#16638)

packages/cli/src/config/settingsSchema.ts

@@ -2093,6 +2093,10 @@ export const SETTINGS_SCHEMA_DEFINITIONS: Record<
           },
         },
       },
+      enabled: {
+        type: 'boolean',
+        description: 'Whether to enable the agent.',
+      },
       disabled: {
         type: 'boolean',
         description: 'Whether to disable the agent.',

packages/core/src/agents/generalist-agent.test.ts

@@ -0,0 +1,36 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi } from 'vitest';
+import { GeneralistAgent } from './generalist-agent.js';
+import { makeFakeConfig } from '../test-utils/config.js';
+import { DELEGATE_TO_AGENT_TOOL_NAME } from '../tools/tool-names.js';
+import type { ToolRegistry } from '../tools/tool-registry.js';
+import type { AgentRegistry } from './registry.js';
+
+describe('GeneralistAgent', () => {
+  it('should create a valid generalist agent definition', () => {
+    const config = makeFakeConfig();
+    vi.spyOn(config, 'getToolRegistry').mockReturnValue({
+      getAllToolNames: () => ['tool1', 'tool2', DELEGATE_TO_AGENT_TOOL_NAME],
+    } as unknown as ToolRegistry);
+    vi.spyOn(config, 'getAgentRegistry').mockReturnValue({
+      getDirectoryContext: () => 'mock directory context',
+    } as unknown as AgentRegistry);
+
+    const agent = GeneralistAgent(config);
+
+    expect(agent.name).toBe('generalist');
+    expect(agent.kind).toBe('local');
+    expect(agent.modelConfig.model).toBe('inherit');
+    expect(agent.toolConfig?.tools).toBeDefined();
+    expect(agent.toolConfig?.tools).not.toContain(DELEGATE_TO_AGENT_TOOL_NAME);
+    expect(agent.toolConfig?.tools).toContain('tool1');
+    expect(agent.promptConfig.systemPrompt).toContain('CLI agent');
+    // Ensure it's non-interactive
+    expect(agent.promptConfig.systemPrompt).toContain('non-interactive');
+  });
+});

packages/core/src/agents/generalist-agent.ts

@@ -0,0 +1,71 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { z } from 'zod';
+import type { Config } from '../config/config.js';
+import { getCoreSystemPrompt } from '../core/prompts.js';
+import type { LocalAgentDefinition } from './types.js';
+import { DELEGATE_TO_AGENT_TOOL_NAME } from '../tools/tool-names.js';
+
+const GeneralistAgentSchema = z.object({
+  response: z.string().describe('The final response from the agent.'),
+});
+
+/**
+ * A general-purpose AI agent with access to all tools.
+ * It uses the same core system prompt as the main agent but in a non-interactive mode.
+ */
+export const GeneralistAgent = (
+  config: Config,
+): LocalAgentDefinition<typeof GeneralistAgentSchema> => ({
+  kind: 'local',
+  name: 'generalist',
+  displayName: 'Generalist Agent',
+  description:
+    "A general-purpose AI agent with access to all tools. Use it for complex tasks that don't fit into other specialized agents.",
+  experimental: true,
+  inputConfig: {
+    inputs: {
+      request: {
+        description: 'The task or question for the generalist agent.',
+        type: 'string',
+        required: true,
+      },
+    },
+  },
+  outputConfig: {
+    outputName: 'result',
+    description: 'The final answer or results of the task.',
+    schema: GeneralistAgentSchema,
+  },
+  modelConfig: {
+    model: 'inherit',
+  },
+  get toolConfig() {
+    // TODO(15179): Support recursive agent invocation.
+    const tools = config
+      .getToolRegistry()
+      .getAllToolNames()
+      .filter((name) => name !== DELEGATE_TO_AGENT_TOOL_NAME);
+    return {
+      tools,
+    };
+  },
+  get promptConfig() {
+    return {
+      systemPrompt: getCoreSystemPrompt(
+        config,
+        /*useMemory=*/ undefined,
+        /*interactiveOverride=*/ false,
+      ),
+      query: '${request}',
+    };
+  },
+  runConfig: {
+    maxTimeMinutes: 10,
+    maxTurns: 20,
+  },
+});

packages/core/src/agents/registry.test.ts

@@ -21,6 +21,8 @@ import {
 } from '../config/models.js';
 import * as tomlLoader from './agentLoader.js';
 import { SimpleExtensionLoader } from '../utils/extensionLoader.js';
+import type { ConfigParameters } from '../config/config.js';
+import type { ToolRegistry } from '../tools/tool-registry.js';
 
 vi.mock('./agentLoader.js', () => ({
   loadAgentsFromDirectory: vi
@@ -34,6 +36,17 @@ vi.mock('./a2a-client-manager.js', () => ({
   },
 }));
 
+function makeMockedConfig(params?: Partial<ConfigParameters>): Config {
+  const config = makeFakeConfig(params);
+  vi.spyOn(config, 'getToolRegistry').mockReturnValue({
+    getAllToolNames: () => ['tool1', 'tool2'],
+  } as unknown as ToolRegistry);
+  vi.spyOn(config, 'getAgentRegistry').mockReturnValue({
+    getDirectoryContext: () => 'mock directory context',
+  } as unknown as AgentRegistry);
+  return config;
+}
+
 // A test-only subclass to expose the protected `registerAgent` method.
 class TestableAgentRegistry extends AgentRegistry {
   async testRegisterAgent(definition: AgentDefinition): Promise<void> {
@@ -73,7 +86,7 @@ describe('AgentRegistry', () => {
 
   beforeEach(() => {
     // Default configuration (debugMode: false)
-    mockConfig = makeFakeConfig();
+    mockConfig = makeMockedConfig();
     registry = new TestableAgentRegistry(mockConfig);
     vi.mocked(tomlLoader.loadAgentsFromDirectory).mockResolvedValue({
       agents: [],
@@ -97,7 +110,7 @@ describe('AgentRegistry', () => {
     // });
 
     it('should log the count of loaded agents in debug mode', async () => {
-      const debugConfig = makeFakeConfig({
+      const debugConfig = makeMockedConfig({
         debugMode: true,
         enableAgents: true,
       });
@@ -115,7 +128,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should use preview flash model for codebase investigator if main model is preview pro', async () => {
-      const previewConfig = makeFakeConfig({
+      const previewConfig = makeMockedConfig({
         model: PREVIEW_GEMINI_MODEL,
         codebaseInvestigatorSettings: {
           enabled: true,
@@ -136,7 +149,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should use preview flash model for codebase investigator if main model is preview auto', async () => {
-      const previewConfig = makeFakeConfig({
+      const previewConfig = makeMockedConfig({
         model: PREVIEW_GEMINI_MODEL_AUTO,
         codebaseInvestigatorSettings: {
           enabled: true,
@@ -157,7 +170,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should use the model from the investigator settings', async () => {
-      const previewConfig = makeFakeConfig({
+      const previewConfig = makeMockedConfig({
         model: PREVIEW_GEMINI_MODEL,
         codebaseInvestigatorSettings: {
           enabled: true,
@@ -178,7 +191,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should load agents from user and project directories with correct precedence', async () => {
-      mockConfig = makeFakeConfig({ enableAgents: true });
+      mockConfig = makeMockedConfig({ enableAgents: true });
       registry = new TestableAgentRegistry(mockConfig);
 
       const userAgent = {
@@ -217,7 +230,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should NOT load TOML agents when enableAgents is false', async () => {
-      const disabledConfig = makeFakeConfig({
+      const disabledConfig = makeMockedConfig({
         enableAgents: false,
         codebaseInvestigatorSettings: { enabled: false },
         cliHelpAgentSettings: { enabled: false },
@@ -233,7 +246,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should register CLI help agent by default', async () => {
-      const config = makeFakeConfig();
+      const config = makeMockedConfig();
       const registry = new TestableAgentRegistry(config);
 
       await registry.initialize();
@@ -242,7 +255,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should register CLI help agent if disabled', async () => {
-      const config = makeFakeConfig({
+      const config = makeMockedConfig({
         cliHelpAgentSettings: { enabled: false },
       });
       const registry = new TestableAgentRegistry(config);
@@ -252,6 +265,61 @@ describe('AgentRegistry', () => {
       expect(registry.getDefinition('cli_help')).toBeUndefined();
     });
 
+    it('should NOT register generalist agent by default (because it is experimental)', async () => {
+      const config = makeMockedConfig();
+      const registry = new TestableAgentRegistry(config);
+
+      await registry.initialize();
+
+      expect(registry.getDefinition('generalist')).toBeUndefined();
+    });
+
+    it('should register generalist agent if explicitly enabled via override', async () => {
+      const config = makeMockedConfig({
+        agents: {
+          overrides: {
+            generalist: { enabled: true },
+          },
+        },
+      });
+      const registry = new TestableAgentRegistry(config);
+
+      await registry.initialize();
+
+      expect(registry.getDefinition('generalist')).toBeDefined();
+    });
+
+    it('should NOT register a non-experimental agent if enabled is false', async () => {
+      // CLI help is NOT experimental, but we explicitly disable it via enabled: false
+      const config = makeMockedConfig({
+        agents: {
+          overrides: {
+            cli_help: { enabled: false },
+          },
+        },
+      });
+      const registry = new TestableAgentRegistry(config);
+
+      await registry.initialize();
+
+      expect(registry.getDefinition('cli_help')).toBeUndefined();
+    });
+
+    it('should respect disabled override over enabled override', async () => {
+      const config = makeMockedConfig({
+        agents: {
+          overrides: {
+            generalist: { enabled: true, disabled: true },
+          },
+        },
+      });
+      const registry = new TestableAgentRegistry(config);
+
+      await registry.initialize();
+
+      expect(registry.getDefinition('generalist')).toBeUndefined();
+    });
+
     it('should load agents from active extensions', async () => {
       const extensionAgent = {
         ...MOCK_AGENT_V1,
@@ -268,7 +336,7 @@ describe('AgentRegistry', () => {
           id: 'test-extension-id',
         },
       ];
-      const mockConfig = makeFakeConfig({
+      const mockConfig = makeMockedConfig({
         extensionLoader: new SimpleExtensionLoader(extensions),
         enableAgents: true,
       });
@@ -295,7 +363,7 @@ describe('AgentRegistry', () => {
           id: 'test-extension-id',
         },
       ];
-      const mockConfig = makeFakeConfig({
+      const mockConfig = makeMockedConfig({
         extensionLoader: new SimpleExtensionLoader(extensions),
       });
       const registry = new TestableAgentRegistry(mockConfig);
@@ -391,7 +459,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should log remote agent registration in debug mode', async () => {
-      const debugConfig = makeFakeConfig({ debugMode: true });
+      const debugConfig = makeMockedConfig({ debugMode: true });
       const debugRegistry = new TestableAgentRegistry(debugConfig);
       const debugLogSpy = vi
         .spyOn(debugLogger, 'log')
@@ -469,7 +537,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should log overwrites when in debug mode', async () => {
-      const debugConfig = makeFakeConfig({ debugMode: true });
+      const debugConfig = makeMockedConfig({ debugMode: true });
       const debugRegistry = new TestableAgentRegistry(debugConfig);
       const debugLogSpy = vi
         .spyOn(debugLogger, 'log')
@@ -511,7 +579,7 @@ describe('AgentRegistry', () => {
 
   describe('reload', () => {
     it('should clear existing agents and reload from directories', async () => {
-      const config = makeFakeConfig({ enableAgents: true });
+      const config = makeMockedConfig({ enableAgents: true });
       const registry = new TestableAgentRegistry(config);
 
       const initialAgent = { ...MOCK_AGENT_V1, name: 'InitialAgent' };
@@ -542,7 +610,7 @@ describe('AgentRegistry', () => {
 
   describe('inheritance and refresh', () => {
     it('should resolve "inherit" to the current model from configuration', async () => {
-      const config = makeFakeConfig({ model: 'current-model' });
+      const config = makeMockedConfig({ model: 'current-model' });
       const registry = new TestableAgentRegistry(config);
 
       const agent: AgentDefinition = {
@@ -559,7 +627,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should update inherited models when the main model changes', async () => {
-      const config = makeFakeConfig({ model: 'initial-model' });
+      const config = makeMockedConfig({ model: 'initial-model' });
       const registry = new TestableAgentRegistry(config);
       await registry.initialize();
 
@@ -633,7 +701,7 @@ describe('AgentRegistry', () => {
 
   describe('overrides', () => {
     it('should skip registration if agent is disabled in settings', async () => {
-      const config = makeFakeConfig({
+      const config = makeMockedConfig({
         agents: {
           overrides: {
             MockAgent: { disabled: true },
@@ -648,7 +716,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should skip remote agent registration if disabled in settings', async () => {
-      const config = makeFakeConfig({
+      const config = makeMockedConfig({
         agents: {
           overrides: {
             RemoteAgent: { disabled: true },
@@ -671,7 +739,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should merge runConfig overrides', async () => {
-      const config = makeFakeConfig({
+      const config = makeMockedConfig({
         agents: {
           overrides: {
             MockAgent: {
@@ -692,7 +760,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should apply modelConfig overrides', async () => {
-      const config = makeFakeConfig({
+      const config = makeMockedConfig({
         agents: {
           overrides: {
             MockAgent: {
@@ -721,7 +789,7 @@ describe('AgentRegistry', () => {
     });
 
     it('should deep merge generateContentConfig (e.g. thinkingConfig)', async () => {
-      const config = makeFakeConfig({
+      const config = makeMockedConfig({
         agents: {
           overrides: {
             MockAgent: {
@@ -749,6 +817,40 @@ describe('AgentRegistry', () => {
         thinkingBudget: 16384, // Overridden
       });
     });
+
+    it('should preserve lazy getters when applying overrides', async () => {
+      let getterCalled = false;
+      const agentWithGetter: LocalAgentDefinition = {
+        ...MOCK_AGENT_V1,
+        name: 'GetterAgent',
+        get toolConfig() {
+          getterCalled = true;
+          return { tools: ['lazy-tool'] };
+        },
+      };
+
+      const config = makeMockedConfig({
+        agents: {
+          overrides: {
+            GetterAgent: {
+              runConfig: { maxTurns: 100 },
+            },
+          },
+        },
+      });
+      const registry = new TestableAgentRegistry(config);
+
+      await registry.testRegisterAgent(agentWithGetter);
+
+      const registeredDef = registry.getDefinition(
+        'GetterAgent',
+      ) as LocalAgentDefinition;
+
+      expect(registeredDef.runConfig.maxTurns).toBe(100);
+      expect(getterCalled).toBe(false); // Getter should not have been called yet
+      expect(registeredDef.toolConfig?.tools).toEqual(['lazy-tool']);
+      expect(getterCalled).toBe(true); // Getter should have been called now
+    });
   });
 
   describe('getToolDescription', () => {

packages/core/src/agents/registry.ts

@@ -11,6 +11,7 @@ import type { AgentDefinition, LocalAgentDefinition } from './types.js';
 import { loadAgentsFromDirectory } from './agentLoader.js';
 import { CodebaseInvestigatorAgent } from './codebase-investigator.js';
 import { CliHelpAgent } from './cli-help-agent.js';
+import { GeneralistAgent } from './generalist-agent.js';
 import { A2AClientManager } from './a2a-client-manager.js';
 import { ADCHandler } from './remote-invocation.js';
 import { type z } from 'zod';
@@ -203,6 +204,9 @@ export class AgentRegistry {
     ) {
       this.registerLocalAgent(CliHelpAgent(this.config));
     }
+
+    // Register the generalist agent.
+    this.registerLocalAgent(GeneralistAgent(this.config));
   }
 
   private async refreshAgents(): Promise<void> {
@@ -249,7 +253,8 @@ export class AgentRegistry {
 
     const settingsOverrides =
       this.config.getAgentsSettings().overrides?.[definition.name];
-    if (settingsOverrides?.disabled) {
+
+    if (!this.isAgentEnabled(definition, settingsOverrides)) {
       if (this.config.getDebugMode()) {
         debugLogger.log(
           `[AgentRegistry] Skipping disabled agent '${definition.name}'`,
@@ -268,6 +273,24 @@ export class AgentRegistry {
     this.registerModelConfigs(mergedDefinition);
   }
 
+  private isAgentEnabled<TOutput extends z.ZodTypeAny>(
+    definition: AgentDefinition<TOutput>,
+    overrides?: AgentOverride,
+  ): boolean {
+    const isExperimental = definition.experimental === true;
+    let isEnabled = !isExperimental;
+
+    if (overrides) {
+      if (overrides.disabled !== undefined) {
+        isEnabled = !overrides.disabled;
+      } else if (overrides.enabled !== undefined) {
+        isEnabled = overrides.enabled;
+      }
+    }
+
+    return isEnabled;
+  }
+
   /**
    * Registers a remote agent definition asynchronously.
    */
@@ -288,7 +311,8 @@ export class AgentRegistry {
 
     const overrides =
       this.config.getAgentsSettings().overrides?.[definition.name];
-    if (overrides?.disabled) {
+
+    if (!this.isAgentEnabled(definition, overrides)) {
       if (this.config.getDebugMode()) {
         debugLogger.log(
           `[AgentRegistry] Skipping disabled remote agent '${definition.name}'`,
@@ -341,17 +365,24 @@ export class AgentRegistry {
       return definition;
     }
 
-    return {
-      ...definition,
-      runConfig: {
+    // Use Object.create to preserve lazy getters on the definition object
+    const merged: LocalAgentDefinition<TOutput> = Object.create(definition);
+
+    if (overrides.runConfig) {
+      merged.runConfig = {
         ...definition.runConfig,
         ...overrides.runConfig,
-      },
-      modelConfig: ModelConfigService.merge(
+      };
+    }
+
+    if (overrides.modelConfig) {
+      merged.modelConfig = ModelConfigService.merge(
         definition.modelConfig,
-        overrides.modelConfig ?? {},
-      ),
-    };
+        overrides.modelConfig,
+      );
+    }
+
+    return merged;
   }
 
   private registerModelConfigs<TOutput extends z.ZodTypeAny>(

packages/core/src/agents/types.ts

@@ -65,6 +65,7 @@ export interface BaseAgentDefinition<
   name: string;
   displayName?: string;
   description: string;
+  experimental?: boolean;
   inputConfig: InputConfig;
   outputConfig?: OutputConfig<TOutput>;
 }

packages/core/src/config/config.ts

@@ -171,6 +171,7 @@ export interface AgentOverride {
   modelConfig?: ModelConfig;
   runConfig?: AgentRunConfig;
   disabled?: boolean;
+  enabled?: boolean;
 }
 
 export interface AgentSettings {

packages/core/src/core/prompts.ts

@@ -80,6 +80,7 @@ export function resolvePathFromEnv(envVar?: string): {
 export function getCoreSystemPrompt(
   config: Config,
   userMemory?: string,
+  interactiveOverride?: boolean,
 ): string {
   // A flag to indicate whether the system prompt override is active.
   let systemMdEnabled = false;
@@ -128,7 +129,7 @@ export function getCoreSystemPrompt(
     .getAllToolNames()
     .includes(WriteTodosTool.Name);
 
-  const interactiveMode = config.isInteractive();
+  const interactiveMode = interactiveOverride ?? config.isInteractive();
 
   const skills = config.getSkillManager().getSkills();
   let skillsPrompt = '';

schemas/settings.schema.json

@@ -1929,6 +1929,10 @@
             }
           }
         },
+        "enabled": {
+          "type": "boolean",
+          "description": "Whether to enable the agent."
+        },
         "disabled": {
           "type": "boolean",
           "description": "Whether to disable the agent."