fix(acp): run exit cleanup when stdin closes (#14953)

Signed-off-by: Adrian Cole <adrian@tetrate.io>
Co-authored-by: Allen Hutchison <adh@google.com>
Co-authored-by: Allen Hutchison <allen@hutchison.org>

integration-tests/acp-telemetry.test.ts

@@ -0,0 +1,116 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { TestRig } from './test-helper.js';
+import { spawn, ChildProcess } from 'node:child_process';
+import { join } from 'node:path';
+import { readFileSync, existsSync } from 'node:fs';
+import { Writable, Readable } from 'node:stream';
+import { env } from 'node:process';
+import * as acp from '@agentclientprotocol/sdk';
+
+// Skip in sandbox mode - test spawns CLI directly which behaves differently in containers
+const sandboxEnv = env['GEMINI_SANDBOX'];
+const itMaybe = sandboxEnv && sandboxEnv !== 'false' ? it.skip : it;
+
+// Reuse existing fake responses that return a simple "Hello" response
+const SIMPLE_RESPONSE_PATH = 'hooks-system.session-startup.responses';
+
+class SessionUpdateCollector implements acp.Client {
+  updates: acp.SessionNotification[] = [];
+
+  sessionUpdate = async (params: acp.SessionNotification) => {
+    this.updates.push(params);
+  };
+
+  requestPermission = async (): Promise<acp.RequestPermissionResponse> => {
+    throw new Error('unexpected');
+  };
+}
+
+describe('ACP telemetry', () => {
+  let rig: TestRig;
+  let child: ChildProcess | undefined;
+
+  beforeEach(() => {
+    rig = new TestRig();
+  });
+
+  afterEach(async () => {
+    child?.kill();
+    child = undefined;
+    await rig.cleanup();
+  });
+
+  itMaybe('should flush telemetry when connection closes', async () => {
+    rig.setup('acp-telemetry-flush', {
+      fakeResponsesPath: join(import.meta.dirname, SIMPLE_RESPONSE_PATH),
+    });
+
+    const telemetryPath = join(rig.homeDir!, 'telemetry.log');
+    const bundlePath = join(import.meta.dirname, '..', 'bundle/gemini.js');
+
+    child = spawn(
+      'node',
+      [
+        bundlePath,
+        '--experimental-acp',
+        '--fake-responses',
+        join(rig.testDir!, 'fake-responses.json'),
+      ],
+      {
+        cwd: rig.testDir!,
+        stdio: ['pipe', 'pipe', 'inherit'],
+        env: {
+          ...process.env,
+          GEMINI_API_KEY: 'fake-key',
+          GEMINI_CLI_HOME: rig.homeDir!,
+          GEMINI_TELEMETRY_ENABLED: 'true',
+          GEMINI_TELEMETRY_TARGET: 'local',
+          GEMINI_TELEMETRY_OUTFILE: telemetryPath,
+          // GEMINI_DEV_TRACING not set: fake responses aren't instrumented for spans
+        },
+      },
+    );
+
+    const input = Writable.toWeb(child.stdin!);
+    const output = Readable.toWeb(child.stdout!) as ReadableStream<Uint8Array>;
+    const testClient = new SessionUpdateCollector();
+    const stream = acp.ndJsonStream(input, output);
+    const connection = new acp.ClientSideConnection(() => testClient, stream);
+
+    await connection.initialize({
+      protocolVersion: acp.PROTOCOL_VERSION,
+      clientCapabilities: { fs: { readTextFile: false, writeTextFile: false } },
+    });
+
+    const { sessionId } = await connection.newSession({
+      cwd: rig.testDir!,
+      mcpServers: [],
+    });
+
+    await connection.prompt({
+      sessionId,
+      prompt: [{ type: 'text', text: 'Say hello' }],
+    });
+
+    expect(JSON.stringify(testClient.updates)).toContain('Hello');
+
+    // Close stdin to trigger telemetry flush via runExitCleanup()
+    child.stdin!.end();
+    await new Promise<void>((resolve) => {
+      child!.on('close', () => resolve());
+    });
+    child = undefined;
+
+    // gen_ai.output.messages is the last OTEL log emitted (after prompt response)
+    expect(existsSync(telemetryPath)).toBe(true);
+    expect(readFileSync(telemetryPath, 'utf-8')).toContain(
+      'gen_ai.output.messages',
+    );
+  });
+});