Add an eval for and fix unsafe cloning behavior. (#24457)

evals/unsafe-cloning.eval.ts

@@ -0,0 +1,64 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { evalTest, TestRig } from './test-helper.js';
+
+evalTest('USUALLY_PASSES', {
+  name: 'Reproduction: Agent uses Object.create() for cloning/delegation',
+  prompt:
+    'Create a utility function `createScopedConfig(config: Config, additionalDirectories: string[]): Config` in `packages/core/src/config/scoped-config.ts` that returns a new Config instance. This instance should override `getWorkspaceContext()` to include the additional directories, but delegate all other method calls (like `isPathAllowed` or `validatePathAccess`) to the original config. Note that `Config` is a complex class with private state and cannot be easily shallow-copied or reconstructed.',
+  files: {
+    'packages/core/src/config/config.ts': `
+export class Config {
+  private _internalState = 'secret';
+  constructor(private workspaceContext: any) {}
+  getWorkspaceContext() { return this.workspaceContext; }
+  isPathAllowed(path: string) {
+    return this.getWorkspaceContext().isPathWithinWorkspace(path);
+  }
+  validatePathAccess(path: string) {
+    if (!this.isPathAllowed(path)) return 'Denied';
+    return null;
+  }
+}`,
+    'packages/core/src/utils/workspaceContext.ts': `
+export class WorkspaceContext {
+  constructor(private root: string, private additional: string[] = []) {}
+  getDirectories() { return [this.root, ...this.additional]; }
+  isPathWithinWorkspace(path: string) {
+    return this.getDirectories().some(d => path.startsWith(d));
+  }
+}`,
+    'package.json': JSON.stringify({
+      name: 'test-project',
+      version: '1.0.0',
+      type: 'module',
+    }),
+  },
+  assert: async (rig: TestRig) => {
+    const filePath = 'packages/core/src/config/scoped-config.ts';
+    const content = rig.readFile(filePath);
+
+    if (!content) {
+      throw new Error(`File ${filePath} was not created.`);
+    }
+
+    // Strip comments to avoid false positives.
+    const codeWithoutComments = content.replace(/\/\*[\s\S]*?\*\/|\/\/.*/g, '');
+
+    // Ensure that the agent did not use Object.create() in the implementation.
+    // We check for the call pattern specifically using a regex to avoid false positives in comments.
+    const hasObjectCreate = /\bObject\.create\s*\(/.test(codeWithoutComments);
+    if (hasObjectCreate) {
+      throw new Error(
+        'Evaluation Failed: Agent used Object.create() for cloning. ' +
+          'This behavior is forbidden by the project lint rules (no-restricted-syntax). ' +
+          'Implementation found:\n\n' +
+          content,
+      );
+    }
+  },
+});