diff --git a/core/src/code_executors/unsafe_local_code_executor.ts b/core/src/code_executors/unsafe_local_code_executor.ts
index 97061719a..1457d189e 100644
--- a/core/src/code_executors/unsafe_local_code_executor.ts
+++ b/core/src/code_executors/unsafe_local_code_executor.ts
@@ -65,12 +65,10 @@ async function createTempScriptFile(
   language: CodeExecutionLanguage,
   shellCommandPath?: string,
 ): Promise<{filePath: string; tempDir: string}> {
-  const tempDir = path.join(
-    os.tmpdir(),
-    'adk_js_unsafe_code_executor',
-    Date.now().toString() + '_' + Math.random().toString(36).slice(2),
+  // mkdtemp names the directory itself and creates it exclusively at 0o700.
+  const tempDir = await fs.mkdtemp(
+    path.join(os.tmpdir(), 'adk_js_unsafe_code_executor_'),
   );
-  await fs.mkdir(tempDir, {recursive: true});
 
   const ext = getExtensionForLanguage(language, shellCommandPath) || '.js';
   const filePath = path.join(tempDir, `script${ext}`);
diff --git a/core/test/code_executors/unsafe_local_code_executor_test.ts b/core/test/code_executors/unsafe_local_code_executor_test.ts
index 82a0d2d01..7a38ed2c0 100644
--- a/core/test/code_executors/unsafe_local_code_executor_test.ts
+++ b/core/test/code_executors/unsafe_local_code_executor_test.ts
@@ -15,6 +15,7 @@ import {
 } from '@google/adk';
 import {EventEmitter} from 'node:events';
 import * as os from 'node:os';
+import * as path from 'node:path';
 import {beforeEach, describe, expect, it, vi} from 'vitest';
 
 // Only `spawn` is mocked; it defaults to the real implementation (see
@@ -90,6 +91,42 @@ describe('UnsafeLocalCodeExecutor', () => {
     expect(result.stderr).toBe('');
   });
 
+  // The script runs with the temporary directory as its cwd, so it can report
+  // the name and mode the executor actually created.
+  it('creates a private, unpredictable temporary directory', async () => {
+    const params: ExecuteCodeParams = {
+      invocationContext,
+      codeExecutionInput: {
+        code: [
+          'const fs = require("node:fs");',
+          'const dir = process.cwd();',
+          'const mode = (fs.statSync(dir).mode & 0o777).toString(8);',
+          'console.log(JSON.stringify({dir, mode}));',
+        ].join('\n'),
+        language: CodeExecutionLanguage.JAVASCRIPT,
+        inputFiles: [],
+      },
+    };
+
+    const firstResult = await executor.executeCode(params);
+    const secondResult = await executor.executeCode(params);
+    expect(firstResult.stderr).toBe('');
+    expect(secondResult.stderr).toBe('');
+
+    const first = JSON.parse(firstResult.stdout);
+    const second = JSON.parse(secondResult.stdout);
+
+    // mkdtemp appends six random characters to the prefix it is given.
+    expect(path.basename(first.dir)).toMatch(
+      /^adk_js_unsafe_code_executor_.{6}$/,
+    );
+    expect(second.dir).not.toBe(first.dir);
+
+    if (os.platform() !== 'win32') {
+      expect(first.mode).toBe('700');
+    }
+  });
+
   it('should capture stderr', async () => {
     const params: ExecuteCodeParams = {
       invocationContext,