Fix: pin the ADK test log level inside the vitest workers

core/test/utils/log_level_pin_test.ts

@@ -0,0 +1,58 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {getLogger} from '@google/adk';
+import {Console} from 'node:console';
+import {Writable} from 'node:stream';
+import {describe, expect, it} from 'vitest';
+
+/**
+ * Returns everything `fn` writes through the global console.
+ *
+ * The winston Console transport backing the ADK logger writes to the streams
+ * of whatever `globalThis.console` is at log time, so swapping in a `Console`
+ * bound to an in-memory stream captures it. Vitest installs its own `Console`
+ * in the worker, which is why spying on `process.stdout.write` or
+ * `console.log` captures nothing here.
+ */
+function captureConsoleOutput(fn: () => void): string {
+  const chunks: string[] = [];
+  const stream = new Writable({
+    write(chunk: unknown, _encoding: string, callback: () => void) {
+      chunks.push(String(chunk));
+      callback();
+    },
+  });
+  const original = globalThis.console;
+  globalThis.console = new Console({stdout: stream, stderr: stream});
+  try {
+    fn();
+  } finally {
+    globalThis.console = original;
+  }
+  return chunks.join('');
+}
+
+/**
+ * Pins the `setupFiles` wiring in `vitest.config.ts`. The log level is
+ * module-level state, so a `globalSetup` file running in the Vitest main
+ * process cannot reach the worker this test runs in; only a setup file can.
+ * There is no public accessor for the effective level, so these assert on what
+ * the logger writes.
+ */
+describe('test worker log level', () => {
+  it('suppresses info logs', () => {
+    expect(captureConsoleOutput(() => getLogger().info('info-pin-probe'))).toBe(
+      '',
+    );
+  });
+
+  it('still emits error logs', () => {
+    expect(
+      captureConsoleOutput(() => getLogger().error('error-pin-probe')),
+    ).toContain('error-pin-probe');
+  });
+});

tests/setup_log_level.ts

@@ -0,0 +1,16 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {LogLevel, setLogLevel} from '../core/src/utils/logger.js';
+
+// Must run inside the test worker: vitest `globalSetup` executes in the main
+// process, and the log level is module-level state a worker never inherits.
+//
+// Import the logger module directly, not the `@google/adk` barrel. Only the
+// per-project `alias` maps that specifier to `core/src`; from here it resolves
+// through the workspace symlink to the built `core/dist` bundle, which is a
+// second module instance with its own log level (and need not exist yet).
+setLogLevel(LogLevel.ERROR);

vitest.config.ts

@@ -35,6 +35,7 @@ export default defineConfig({
         test: {
           name: 'unit:core',
           environment: 'node',
+          setupFiles: ['./tests/setup_log_level.ts'],
           alias: {
             '@google/adk': path.resolve(__dirname, './core/src'),
             '@google/adk-integrations': path.resolve(
@@ -49,6 +50,7 @@ export default defineConfig({
         test: {
           name: 'unit:dev',
           environment: 'node',
+          setupFiles: ['./tests/setup_log_level.ts'],
           alias: {
             '@google/adk': path.resolve(__dirname, './core/src'),
             '@google/adk-integrations': path.resolve(
@@ -63,6 +65,7 @@ export default defineConfig({
         test: {
           name: 'unit:integrations',
           environment: 'node',
+          setupFiles: ['./tests/setup_log_level.ts'],
           alias: {
             '@google/adk': path.resolve(__dirname, './core/src'),
             '@google/adk-integrations': path.resolve(
@@ -77,6 +80,7 @@ export default defineConfig({
         test: {
           name: 'integration',
           environment: 'node',
+          setupFiles: ['./tests/setup_log_level.ts'],
           hookTimeout: INTEGRATION_HOOK_TIMEOUT_MS,
           testTimeout: INTEGRATION_TEST_TIMEOUT_MS,
           alias: {
@@ -93,6 +97,7 @@ export default defineConfig({
         test: {
           name: 'e2e',
           environment: 'node',
+          setupFiles: ['./tests/setup_log_level.ts'],
           alias: {
             '@google/adk': path.resolve(__dirname, './core/src'),
             '@google/adk-integrations': path.resolve(
@@ -107,6 +112,7 @@ export default defineConfig({
         test: {
           name: 'cross-language',
           environment: 'node',
+          setupFiles: ['./tests/setup_log_level.ts'],
           alias: {
             '@google/adk': path.resolve(__dirname, './core/src'),
             '@google/adk-integrations': path.resolve(
@@ -136,6 +142,5 @@ export default defineConfig({
         lines: 86,
       },
     },
-    globalSetup: ['./tests/global_setup.ts'],
   },
 });