diff --git a/dev/src/utils/agent_loader.ts b/dev/src/utils/agent_loader.ts
index 448a32aeb..9f60fdede 100644
--- a/dev/src/utils/agent_loader.ts
+++ b/dev/src/utils/agent_loader.ts
@@ -22,7 +22,7 @@ import {
   isFolderExists,
   loadFileData,
   removeFolder,
-  tryToFindFileRecursively,
+  tryToFindFolderRecursively,
 } from './file_utils.js';
 import {AdkLogger} from './logger.js';
 
@@ -33,6 +33,11 @@ const logger = new AdkLogger({label: 'AgentLoader', colorize: {all: true}});
  */
 const JS_FILES_EXTENSIONS = ['.js', '.cjs', '.mjs', '.ts', '.mts', '.cts'];
 
+/**
+ * How many ancestor directories to search for a project's `node_modules`.
+ */
+const MAX_NODE_MODULES_LOOKUP_LEVELS = 10;
+
 /**
  * Supported JS/TS file module types.
  */
@@ -640,21 +645,23 @@ async function linkProjectNodeModules(
   }
 }
 
+/**
+ * Find the `node_modules` a bundled agent should resolve its externals from.
+ *
+ * Mirrors Node's own upward `node_modules` walk, so a project whose own
+ * directory has a `package.json` but no `node_modules` — the npm/pnpm
+ * workspace layout, where dependencies are hoisted to the workspace root —
+ * still resolves. Returns `undefined` when nothing is found within the bound.
+ */
 async function getProjectNodeModulesDir(
   sourceDir: string,
 ): Promise<string | undefined> {
   try {
-    const packageJsonPath = await tryToFindFileRecursively(
+    return await tryToFindFolderRecursively(
       sourceDir,
-      'package.json',
-      10,
-    );
-    const nodeModulesDir = path.join(
-      path.dirname(packageJsonPath),
       'node_modules',
+      MAX_NODE_MODULES_LOOKUP_LEVELS,
     );
-
-    return (await isFolderExists(nodeModulesDir)) ? nodeModulesDir : undefined;
   } catch {
     return undefined;
   }
diff --git a/dev/src/utils/file_utils.ts b/dev/src/utils/file_utils.ts
index 43998bcc6..348e8d5b8 100644
--- a/dev/src/utils/file_utils.ts
+++ b/dev/src/utils/file_utils.ts
@@ -116,35 +116,75 @@ export function getTempDir(prefix?: string): string {
   return path.join(...pathParts);
 }
 
-/**
- * Try to find a file recursively in the given folder.
- * @param sourceFolder The folder to search in.
- * @param fileName The name of the file to find.
- * @param maxIterations The maximum number of iterations to perform.
- * @returns The absolute path of the found file.
- * @throws Error if the file is not found after the maximum number of
- *     iterations.
- */
-export async function tryToFindFileRecursively(
+/** Walk `sourceFolder` and its ancestors looking for an entry named `entryName`. */
+async function tryToFindEntryRecursively(
   sourceFolder: string,
-  fileName: string,
+  entryName: string,
   maxIterations: number,
+  exists: (entryPath: string) => Promise<boolean>,
 ): Promise<string> {
   let currentFolder = sourceFolder;
 
   for (let i = 0; i < maxIterations; i++) {
-    const filePath = path.join(currentFolder, fileName);
+    const entryPath = path.join(currentFolder, entryName);
 
-    if (await isFileExists(filePath)) {
-      return filePath;
+    if (await exists(entryPath)) {
+      return entryPath;
     }
 
     currentFolder = path.dirname(currentFolder);
   }
 
   throw new Error(
-    `No ${fileName} found in ${
+    `No ${entryName} found in ${
       sourceFolder
     } or its parent folders up to ${maxIterations} levels.`,
   );
 }
+
+/**
+ * Try to find a file recursively in the given folder.
+ * @param sourceFolder The folder to search in.
+ * @param fileName The name of the file to find.
+ * @param maxIterations The maximum number of iterations to perform.
+ * @returns The absolute path of the found file.
+ * @throws Error if the file is not found after the maximum number of
+ *     iterations.
+ */
+export async function tryToFindFileRecursively(
+  sourceFolder: string,
+  fileName: string,
+  maxIterations: number,
+): Promise<string> {
+  return tryToFindEntryRecursively(
+    sourceFolder,
+    fileName,
+    maxIterations,
+    isFileExists,
+  );
+}
+
+/**
+ * Try to find a folder recursively in the given folder.
+ *
+ * Directories named `folderName` match; a plain file with the same name does
+ * not, and the walk continues into the parent folder.
+ * @param sourceFolder The folder to search in.
+ * @param folderName The name of the folder to find.
+ * @param maxIterations The maximum number of iterations to perform.
+ * @returns The absolute path of the found folder.
+ * @throws Error if the folder is not found after the maximum number of
+ *     iterations.
+ */
+export async function tryToFindFolderRecursively(
+  sourceFolder: string,
+  folderName: string,
+  maxIterations: number,
+): Promise<string> {
+  return tryToFindEntryRecursively(
+    sourceFolder,
+    folderName,
+    maxIterations,
+    isFolderExists,
+  );
+}
diff --git a/dev/test/utils/agent_loader_test.ts b/dev/test/utils/agent_loader_test.ts
index d53160d9d..5570cb804 100644
--- a/dev/test/utils/agent_loader_test.ts
+++ b/dev/test/utils/agent_loader_test.ts
@@ -34,7 +34,7 @@ vi.mock('../../src/utils/file_utils.js', () => ({
   isFileExists: vi.fn(),
   isFolderExists: vi.fn(),
   removeFolder: vi.fn(),
-  tryToFindFileRecursively: vi.fn(),
+  tryToFindFolderRecursively: vi.fn(),
 }));
 
 vi.mock('esbuild', async (importOriginal) => {
@@ -184,8 +184,8 @@ describe('AgentLoader', () => {
     (fileUtils.removeFolder as Mock).mockImplementation((folderPath) =>
       fs.rm(folderPath as string, {recursive: true, force: true}),
     );
-    (fileUtils.tryToFindFileRecursively as Mock).mockImplementation(
-      async (_sourceFolder, fileName) => path.join(tempAgentsDir, fileName),
+    (fileUtils.tryToFindFolderRecursively as Mock).mockImplementation(
+      async (_sourceFolder, folderName) => path.join(tempAgentsDir, folderName),
     );
   });
 
@@ -309,6 +309,54 @@ describe('AgentLoader', () => {
       await expect(fs.access(compiledAgentPath)).rejects.toThrow();
     });
 
+    it('links an ancestor node_modules into the compiled output directory', async () => {
+      const nestedDir = path.join(tempAgentsDir, 'nested');
+      await fs.mkdir(nestedDir, {recursive: true});
+      const agentPath = path.join(nestedDir, 'agent1.js');
+      await fs.writeFile(agentPath, agent1JsContent);
+
+      const compiledAgentPath = compiledPath('agent1.cjs');
+      (esbuild.build as Mock).mockImplementation(async () => {
+        await fs.writeFile(compiledAgentPath, agent1JsContent);
+        return Promise.resolve();
+      });
+
+      const agentFile = new AgentFile(agentPath);
+      await agentFile.load();
+
+      await expect(fs.readlink(compiledPath('node_modules'))).resolves.toBe(
+        path.join(tempAgentsDir, 'node_modules'),
+      );
+      expect(fileUtils.tryToFindFolderRecursively).toHaveBeenCalledWith(
+        nestedDir,
+        'node_modules',
+        10,
+      );
+
+      await agentFile.dispose();
+    });
+
+    it('skips the node_modules link when no ancestor has one', async () => {
+      (fileUtils.tryToFindFolderRecursively as Mock).mockRejectedValue(
+        new Error('No node_modules found in /nowhere'),
+      );
+      const agentPath = path.join(tempAgentsDir, 'agent1.js');
+      await fs.writeFile(agentPath, agent1JsContent);
+
+      const compiledAgentPath = compiledPath('agent1.cjs');
+      (esbuild.build as Mock).mockImplementation(async () => {
+        await fs.writeFile(compiledAgentPath, agent1JsContent);
+        return Promise.resolve();
+      });
+
+      const agentFile = new AgentFile(agentPath);
+      await agentFile.load();
+
+      await expect(fs.access(compiledPath('node_modules'))).rejects.toThrow();
+
+      await agentFile.dispose();
+    });
+
     it('throws when getting file path if agent is not loaded', () => {
       const agentPath = path.join(tempAgentsDir, 'agent1.js');
       const agentFile = new AgentFile(agentPath);
diff --git a/dev/test/utils/file_utils_test.ts b/dev/test/utils/file_utils_test.ts
index 8bd5dfdcd..0be5fed74 100644
--- a/dev/test/utils/file_utils_test.ts
+++ b/dev/test/utils/file_utils_test.ts
@@ -15,6 +15,7 @@ import {
   loadFileData,
   saveToFile,
   tryToFindFileRecursively,
+  tryToFindFolderRecursively,
 } from '../../src/utils/file_utils.js';
 
 vi.mock('node:fs/promises', async () => {
@@ -153,6 +154,67 @@ describe('file_utils', () => {
     ).rejects.toThrow(/No target.txt found/);
   });
 
+  /** Makes `folderPaths` look like directories and everything else absent. */
+  function mockFoldersOnDisk(folderPaths: string[]) {
+    fsPromises.access.mockImplementation((p: string) =>
+      folderPaths.includes(p)
+        ? Promise.resolve()
+        : Promise.reject(new Error('not found')),
+    );
+    fsPromises.stat.mockImplementation((p: string) =>
+      folderPaths.includes(p)
+        ? Promise.resolve({isDirectory: () => true})
+        : Promise.reject(new Error('not found')),
+    );
+  }
+
+  it('tryToFindFolderRecursively finds a folder in the source folder itself', async () => {
+    const target = path.join('/a/b/c', 'node_modules');
+    mockFoldersOnDisk([target]);
+
+    await expect(
+      tryToFindFolderRecursively('/a/b/c', 'node_modules', 5),
+    ).resolves.toBe(target);
+  });
+
+  it('tryToFindFolderRecursively finds a folder several levels up', async () => {
+    const target = path.join('/a', 'node_modules');
+    mockFoldersOnDisk([target]);
+
+    await expect(
+      tryToFindFolderRecursively('/a/b/c', 'node_modules', 5),
+    ).resolves.toBe(target);
+  });
+
+  it('tryToFindFolderRecursively skips a same-named file and keeps walking up', async () => {
+    const decoyFile = path.join('/a/b/c', 'node_modules');
+    const target = path.join('/a', 'node_modules');
+    fsPromises.access.mockResolvedValue(undefined);
+    fsPromises.stat.mockImplementation((p: string) => {
+      if (p === decoyFile) {
+        return Promise.resolve({isDirectory: () => false});
+      }
+      if (p === target) {
+        return Promise.resolve({isDirectory: () => true});
+      }
+      return Promise.reject(new Error('not found'));
+    });
+
+    await expect(
+      tryToFindFolderRecursively('/a/b/c', 'node_modules', 5),
+    ).resolves.toBe(target);
+  });
+
+  it('tryToFindFolderRecursively throws when folder not found within maxIterations', async () => {
+    mockFoldersOnDisk([]);
+
+    await expect(
+      tryToFindFolderRecursively('/a/b/c', 'node_modules', 2),
+    ).rejects.toThrow(
+      'No node_modules found in /a/b/c or its parent folders up to 2 levels.',
+    );
+  });
+
   it('listFiles returns entries', async () => {
     const files = ['a.txt', 'b.txt'];
     fsPromises.readdir.mockResolvedValue(files);
diff --git a/tests/integration/agent_loader/__dirname/package.json b/tests/integration/agent_loader/__dirname/package.json
index 08e19b2d6..94601a65e 100644
--- a/tests/integration/agent_loader/__dirname/package.json
+++ b/tests/integration/agent_loader/__dirname/package.json
@@ -2,10 +2,6 @@
   "name": "dirname-test",
   "version": "1.0.0",
   "scripts": {
-    "start": "npx @google/adk-devtools run agent.ts"
-  },
-  "devDependencies": {
-    "@google/adk-devtools": "file:../../../../dev",
-    "@google/adk": "file:../../../../core"
+    "start": "node ../../../../dev/dist/esm/cli_entrypoint.js run agent.ts"
   }
 }
diff --git a/tests/integration/agent_loader/__filename/package.json b/tests/integration/agent_loader/__filename/package.json
index dbf037833..f2891b548 100644
--- a/tests/integration/agent_loader/__filename/package.json
+++ b/tests/integration/agent_loader/__filename/package.json
@@ -2,10 +2,6 @@
   "name": "filename-test",
   "version": "1.0.0",
   "scripts": {
-    "start": "npx @google/adk-devtools run agent.ts"
-  },
-  "devDependencies": {
-    "@google/adk-devtools": "file:../../../../dev",
-    "@google/adk": "file:../../../../core"
+    "start": "node ../../../../dev/dist/esm/cli_entrypoint.js run agent.ts"
   }
 }
diff --git a/tests/integration/agent_loader/agent_dirname_test.ts b/tests/integration/agent_loader/agent_dirname_test.ts
index 1e71a3a1d..058330787 100644
--- a/tests/integration/agent_loader/agent_dirname_test.ts
+++ b/tests/integration/agent_loader/agent_dirname_test.ts
@@ -4,14 +4,12 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {exec, spawn} from 'node:child_process';
-import * as fs from 'node:fs/promises';
+import {spawn} from 'node:child_process';
 import * as path from 'node:path';
-import {promisify} from 'node:util';
-import {afterAll, beforeAll, describe, expect, it} from 'vitest';
+import {beforeAll, describe, expect, it} from 'vitest';
 import {sendInput} from '../test_case_utils.js';
+import {assertWorkspaceAdkCliAvailable} from '../workspace_cli.js';
 
-const execAsync = promisify(exec);
 const dirname = process.cwd();
 const TEST_EXECUTION_TIMEOUT = 40000;
 
@@ -25,8 +23,8 @@ describe.each(['__dirname', '__filename', 'import_meta_url'])(
     );
 
     beforeAll(async () => {
-      await execAsync('npm install', {cwd: projectPath});
-    }, TEST_EXECUTION_TIMEOUT);
+      await assertWorkspaceAdkCliAvailable();
+    });
 
     it(
       'should run agent and load params from file nearby via package.json script',
@@ -45,17 +43,5 @@ describe.each(['__dirname', '__filename', 'import_meta_url'])(
       },
       TEST_EXECUTION_TIMEOUT,
     );
-
-    afterAll(async () => {
-      await fs
-        .rm(path.join(projectPath, 'node_modules'), {
-          recursive: true,
-          force: true,
-        })
-        .catch(() => {});
-      await fs
-        .unlink(path.join(projectPath, 'package-lock.json'))
-        .catch(() => {});
-    }, TEST_EXECUTION_TIMEOUT);
   },
 );
diff --git a/tests/integration/agent_loader/import_meta_url/package.json b/tests/integration/agent_loader/import_meta_url/package.json
index 11701374f..a0ad5bea4 100644
--- a/tests/integration/agent_loader/import_meta_url/package.json
+++ b/tests/integration/agent_loader/import_meta_url/package.json
@@ -3,10 +3,6 @@
   "version": "1.0.0",
   "type": "module",
   "scripts": {
-    "start": "npx @google/adk-devtools run agent.ts"
-  },
-  "devDependencies": {
-    "@google/adk-devtools": "file:../../../../dev",
-    "@google/adk": "file:../../../../core"
+    "start": "node ../../../../dev/dist/esm/cli_entrypoint.js run agent.ts"
   }
 }
diff --git a/tests/integration/app_loader/app_default/package.json b/tests/integration/app_loader/app_default/package.json
index 6ae9d8c19..122826c53 100644
--- a/tests/integration/app_loader/app_default/package.json
+++ b/tests/integration/app_loader/app_default/package.json
@@ -2,10 +2,6 @@
   "name": "app-default-test",
   "version": "1.0.0",
   "scripts": {
-    "start": "npx @google/adk-devtools run app.ts"
-  },
-  "devDependencies": {
-    "@google/adk-devtools": "file:../../../../dev",
-    "@google/adk": "file:../../../../core"
+    "start": "node ../../../../dev/dist/esm/cli_entrypoint.js run app.ts"
   }
 }
diff --git a/tests/integration/app_loader/app_js/package.json b/tests/integration/app_loader/app_js/package.json
index d4424f58d..beafca6c4 100644
--- a/tests/integration/app_loader/app_js/package.json
+++ b/tests/integration/app_loader/app_js/package.json
@@ -2,10 +2,6 @@
   "name": "app-js-test",
   "version": "1.0.0",
   "scripts": {
-    "start": "npx @google/adk-devtools run app.js"
-  },
-  "devDependencies": {
-    "@google/adk-devtools": "file:../../../../dev",
-    "@google/adk": "file:../../../../core"
+    "start": "node ../../../../dev/dist/esm/cli_entrypoint.js run app.js"
   }
 }
diff --git a/tests/integration/app_loader/app_loader_test.ts b/tests/integration/app_loader/app_loader_test.ts
index 4367307b8..30657c49a 100644
--- a/tests/integration/app_loader/app_loader_test.ts
+++ b/tests/integration/app_loader/app_loader_test.ts
@@ -5,15 +5,13 @@
  */
 
 import {App, isApp, isBaseAgent} from '@google/adk';
-import {exec, spawn} from 'node:child_process';
-import * as fs from 'node:fs/promises';
+import {spawn} from 'node:child_process';
 import * as path from 'node:path';
-import {promisify} from 'node:util';
 import {afterAll, beforeAll, describe, expect, it} from 'vitest';
 import {AgentLoader} from '../../../dev/src/utils/agent_loader.js';
 import {sendInput} from '../test_case_utils.js';
+import {assertWorkspaceAdkCliAvailable} from '../workspace_cli.js';
 
-const execAsync = promisify(exec);
 const dirname = process.cwd();
 const TEST_EXECUTION_TIMEOUT = 40000;
 
@@ -28,8 +26,8 @@ describe('App loader CLI integration', () => {
       );
 
       beforeAll(async () => {
-        await execAsync('npm install', {cwd: projectPath});
-      }, TEST_EXECUTION_TIMEOUT);
+        await assertWorkspaceAdkCliAvailable();
+      });
 
       it(
         'should run app via package.json start script and get responses',
@@ -51,18 +49,6 @@ describe('App loader CLI integration', () => {
         },
         TEST_EXECUTION_TIMEOUT,
       );
-
-      afterAll(async () => {
-        await fs
-          .rm(path.join(projectPath, 'node_modules'), {
-            recursive: true,
-            force: true,
-          })
-          .catch(() => {});
-        await fs
-          .unlink(path.join(projectPath, 'package-lock.json'))
-          .catch(() => {});
-      }, TEST_EXECUTION_TIMEOUT);
     },
   );
 });
@@ -75,9 +61,9 @@ describe('AgentLoader discovery and loading integration', () => {
   let loader: AgentLoader;
 
   beforeAll(async () => {
-    await execAsync('npm install', {cwd: projectPath});
+    await assertWorkspaceAdkCliAvailable();
     loader = new AgentLoader(projectPath);
-  }, TEST_EXECUTION_TIMEOUT);
+  });
 
   it(
     'should discover apps vs agents across directories and standalone files',
@@ -129,14 +115,5 @@ describe('AgentLoader discovery and loading integration', () => {
 
   afterAll(async () => {
     await loader.disposeAll();
-    await fs
-      .rm(path.join(projectPath, 'node_modules'), {
-        recursive: true,
-        force: true,
-      })
-      .catch(() => {});
-    await fs
-      .unlink(path.join(projectPath, 'package-lock.json'))
-      .catch(() => {});
   }, TEST_EXECUTION_TIMEOUT);
 });
diff --git a/tests/integration/app_loader/app_ts/package.json b/tests/integration/app_loader/app_ts/package.json
index f113941d3..e891ecf00 100644
--- a/tests/integration/app_loader/app_ts/package.json
+++ b/tests/integration/app_loader/app_ts/package.json
@@ -2,10 +2,6 @@
   "name": "app-ts-test",
   "version": "1.0.0",
   "scripts": {
-    "start": "npx @google/adk-devtools run app.ts"
-  },
-  "devDependencies": {
-    "@google/adk-devtools": "file:../../../../dev",
-    "@google/adk": "file:../../../../core"
+    "start": "node ../../../../dev/dist/esm/cli_entrypoint.js run app.ts"
   }
 }
diff --git a/tests/integration/app_loader/discovery/package.json b/tests/integration/app_loader/discovery/package.json
index 8b137cf40..152e0553b 100644
--- a/tests/integration/app_loader/discovery/package.json
+++ b/tests/integration/app_loader/discovery/package.json
@@ -1,8 +1,4 @@
 {
   "name": "discovery-test",
-  "version": "1.0.0",
-  "devDependencies": {
-    "@google/adk-devtools": "file:../../../../dev",
-    "@google/adk": "file:../../../../core"
-  }
+  "version": "1.0.0"
 }
diff --git a/tests/integration/skills/script_js/agent_test.ts b/tests/integration/skills/script_js/agent_test.ts
index b17df2c86..aad21f773 100644
--- a/tests/integration/skills/script_js/agent_test.ts
+++ b/tests/integration/skills/script_js/agent_test.ts
@@ -3,13 +3,12 @@
  * Copyright 2026 Google LLC
  * SPDX-License-Identifier: Apache-2.0
  */
-import {exec, spawn} from 'node:child_process';
+import {spawn} from 'node:child_process';
 import * as fs from 'node:fs/promises';
-import {promisify} from 'node:util';
 import {afterAll, beforeAll, describe, expect, it} from 'vitest';
 import {normalizeLineEndings, sendInput} from '../../test_case_utils.js';
+import {assertWorkspaceAdkCliAvailable} from '../../workspace_cli.js';
 
-const execAsync = promisify(exec);
 const dirname = process.cwd();
 const PROJECT_PATH = `${dirname}/tests/integration/skills/script_js`;
 const TEST_EXECUTION_TIMEOUT = 60000;
@@ -24,14 +23,14 @@ const TEST_EXECUTION_TIMEOUT = 60000;
  * 3. Asserts that the agent's response matches the expected output, confirming it claims to have created the art and files.
  * 4. Verifies that the expected files (`ephemeral_entanglement.md`, `index.html`, `sketch.js`) were actually generated in the file system.
  * 5. Compares the content of these generated files with reference files in the `expected/` directory to ensure correctness.
- * 6. Cleans up the generated files and installed dependencies after execution.
+ * 6. Cleans up the generated files after execution.
  *
  * This test ensures the end-to-end flow of an agent using tools to generate and materialize files based on a high-level request.
  */
 describe('Agent with skills that generates JS script and runs it locally', () => {
   beforeAll(async () => {
-    await execAsync('npm install', {cwd: PROJECT_PATH});
-  }, TEST_EXECUTION_TIMEOUT);
+    await assertWorkspaceAdkCliAvailable();
+  });
 
   it(
     'should run agent with skills successfully',
@@ -99,10 +98,5 @@ describe('Agent with skills that generates JS script and runs it locally', () =>
       .catch(() => {});
     await fs.rm(`${PROJECT_PATH}/index.html`, {force: true}).catch(() => {});
     await fs.rm(`${PROJECT_PATH}/sketch.js`, {force: true}).catch(() => {});
-
-    await fs
-      .rm(`${PROJECT_PATH}/node_modules`, {recursive: true, force: true})
-      .catch(() => {});
-    await fs.unlink(`${PROJECT_PATH}/package-lock.json`).catch(() => {});
   });
 });
diff --git a/tests/integration/skills/script_js/package.json b/tests/integration/skills/script_js/package.json
index 352430b54..015dff40a 100644
--- a/tests/integration/skills/script_js/package.json
+++ b/tests/integration/skills/script_js/package.json
@@ -3,10 +3,6 @@
   "version": "1.0.0",
   "type": "module",
   "scripts": {
-    "start": "npx @google/adk-devtools run agent.ts"
-  },
-  "devDependencies": {
-    "@google/adk-devtools": "file:../../../../dev",
-    "@google/adk": "file:../../../../core"
+    "start": "node ../../../../dev/dist/esm/cli_entrypoint.js run agent.ts"
   }
 }
diff --git a/tests/integration/workspace_cli.ts b/tests/integration/workspace_cli.ts
new file mode 100644
index 000000000..b2bf08c04
--- /dev/null
+++ b/tests/integration/workspace_cli.ts
@@ -0,0 +1,40 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {access} from 'node:fs/promises';
+import * as path from 'node:path';
+
+/**
+ * The built dev-workspace CLI, relative to the repository root.
+ *
+ * Fixtures under `tests/integration` invoke this file directly from their
+ * `start` script, so they need no `node_modules` of their own. `npm install`
+ * cannot link `node_modules/.bin/adk` for them: npm skips a workspace bin whose
+ * target does not exist yet, and the repository builds only after installing.
+ */
+const DEV_CLI_PATH = path.join('dev', 'dist', 'esm', 'cli_entrypoint.js');
+
+/**
+ * Fails fast when the workspace-root build those fixtures rely on is missing.
+ *
+ * Without it the spawned `npm run start` dies before writing anything to
+ * stdout, and the suite reports an empty-response assertion failure that says
+ * nothing about the cause.
+ */
+export async function assertWorkspaceAdkCliAvailable(
+  workspaceRoot = process.cwd(),
+): Promise<void> {
+  const cliPath = path.join(workspaceRoot, DEV_CLI_PATH);
+
+  try {
+    await access(cliPath);
+  } catch (e: unknown) {
+    throw new Error(
+      `Missing ${cliPath}. Run \`npm install && npm run build\` at the repository root first.`,
+      {cause: e},
+    );
+  }
+}
diff --git a/tests/integration/workspace_cli_test.ts b/tests/integration/workspace_cli_test.ts
new file mode 100644
index 000000000..21d5b594b
--- /dev/null
+++ b/tests/integration/workspace_cli_test.ts
@@ -0,0 +1,39 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import * as fs from 'node:fs/promises';
+import * as os from 'node:os';
+import * as path from 'node:path';
+import {afterEach, beforeEach, describe, expect, it} from 'vitest';
+import {assertWorkspaceAdkCliAvailable} from './workspace_cli.js';
+
+describe('assertWorkspaceAdkCliAvailable', () => {
+  let workspaceRoot: string;
+
+  beforeEach(async () => {
+    workspaceRoot = await fs.mkdtemp(path.join(os.tmpdir(), 'workspace-cli-'));
+  });
+
+  afterEach(async () => {
+    await fs.rm(workspaceRoot, {recursive: true, force: true});
+  });
+
+  it('resolves when the dev CLI has been built', async () => {
+    const cliDir = path.join(workspaceRoot, 'dev', 'dist', 'esm');
+    await fs.mkdir(cliDir, {recursive: true});
+    await fs.writeFile(path.join(cliDir, 'cli_entrypoint.js'), '');
+
+    await expect(
+      assertWorkspaceAdkCliAvailable(workspaceRoot),
+    ).resolves.toBeUndefined();
+  });
+
+  it('rejects naming the missing CLI path when the workspace is not built', async () => {
+    await expect(assertWorkspaceAdkCliAvailable(workspaceRoot)).rejects.toThrow(
+      `Missing ${path.join(workspaceRoot, 'dev', 'dist', 'esm', 'cli_entrypoint.js')}. Run \`npm install && npm run build\` at the repository root first.`,
+    );
+  });
+});