test(evals): add subagent delegation evaluation tests

evals/subtask_delegation.eval.ts

@@ -0,0 +1,130 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, expect } from 'vitest';
+import {
+  TRACKER_CREATE_TASK_TOOL_NAME,
+  TRACKER_UPDATE_TASK_TOOL_NAME,
+} from '@google/gemini-cli-core';
+import { evalTest, TEST_AGENTS } from './test-helper.js';
+
+describe('subtask delegation eval test cases', () => {
+  /**
+   * Checks that the main agent can correctly decompose a complex, sequential
+   * task into subtasks using the task tracker and delegate each to the appropriate expert subagent.
+   *
+   * The task requires:
+   * 1. Reading requirements (researcher)
+   * 2. Implementing logic (developer)
+   * 3. Documenting (doc expert)
+   */
+  evalTest('USUALLY_PASSES', {
+    name: 'should delegate sequential subtasks to relevant experts using the task tracker',
+    params: {
+      settings: {
+        experimental: {
+          enableAgents: true,
+          taskTracker: true,
+        },
+      },
+    },
+    prompt:
+      'Please read the requirements in requirements.txt using a researcher, then implement the requested logic in src/logic.ts using a developer, and finally document the implementation in docs/logic.md using a documentation expert.',
+    files: {
+      '.gemini/agents/researcher.md': `---
+name: researcher
+description: Expert in reading files and extracting requirements.
+tools:
+  - read_file
+---
+You are the researcher. Read the provided file and extract requirements.`,
+      '.gemini/agents/developer.md': `---
+name: developer
+description: Expert in implementing logic in TypeScript.
+tools:
+  - write_file
+---
+You are the developer. Implement the requested logic in the specified file.`,
+      '.gemini/agents/doc-expert.md': `---
+name: doc-expert
+description: Expert in writing technical documentation.
+tools:
+  - write_file
+---
+You are the doc expert. Document the provided implementation clearly.`,
+      'requirements.txt':
+        'Implement a function named "calculateSum" that adds two numbers.',
+    },
+    assert: async (rig, _result) => {
+      // Verify tracker tasks were created
+      const wasCreateCalled = await rig.waitForToolCall(
+        TRACKER_CREATE_TASK_TOOL_NAME,
+      );
+      expect(wasCreateCalled).toBe(true);
+
+      const toolLogs = rig.readToolLogs();
+      const createCalls = toolLogs.filter(
+        (l) => l.toolRequest.name === TRACKER_CREATE_TASK_TOOL_NAME,
+      );
+      expect(createCalls.length).toBeGreaterThanOrEqual(3);
+
+      await rig.expectToolCallSuccess([
+        'researcher',
+        'developer',
+        'doc-expert',
+      ]);
+
+      const logicFile = rig.readFile('src/logic.ts');
+      const docFile = rig.readFile('docs/logic.md');
+
+      expect(logicFile).toContain('calculateSum');
+      expect(docFile).toBeTruthy();
+    },
+  });
+
+  /**
+   * Checks that the main agent can delegate a batch of independent subtasks
+   * to multiple subagents in parallel using the task tracker to manage state.
+   */
+  evalTest('USUALLY_PASSES', {
+    name: 'should delegate independent subtasks to specialists using the task tracker',
+    params: {
+      settings: {
+        experimental: {
+          enableAgents: true,
+          taskTracker: true,
+        },
+      },
+    },
+    prompt:
+      'Please update the project for internationalization (i18n), audit the security of the current code, and update the CSS to use a blue theme. Use specialized experts for each task.',
+    files: {
+      ...TEST_AGENTS.I18N_AGENT.asFile(),
+      ...TEST_AGENTS.SECURITY_AGENT.asFile(),
+      ...TEST_AGENTS.CSS_AGENT.asFile(),
+      'index.ts': 'console.log("Hello World");',
+    },
+    assert: async (rig, _result) => {
+      // Verify tracker tasks were created
+      const wasCreateCalled = await rig.waitForToolCall(
+        TRACKER_CREATE_TASK_TOOL_NAME,
+      );
+      expect(wasCreateCalled).toBe(true);
+
+      const toolLogs = rig.readToolLogs();
+      const createCalls = toolLogs.filter(
+        (l) => l.toolRequest.name === TRACKER_CREATE_TASK_TOOL_NAME,
+      );
+      expect(createCalls.length).toBeGreaterThanOrEqual(3);
+
+      await rig.expectToolCallSuccess([
+        TEST_AGENTS.I18N_AGENT.name,
+        TEST_AGENTS.SECURITY_AGENT.name,
+        TEST_AGENTS.CSS_AGENT.name,
+      ]);
+    },
+  });
+});