fix(core): Fix chat corruption bug in context manager. (#26534)

packages/core/src/context/graph/render.test.ts

@@ -0,0 +1,64 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi } from 'vitest';
+import { render } from './render.js';
+import type { ConcreteNode } from './types.js';
+import { NodeType } from './types.js';
+import type { ContextEnvironment } from '../pipeline/environment.js';
+import type { ContextTracer } from '../tracer.js';
+import type { ContextProfile } from '../config/profiles.js';
+import type { PipelineOrchestrator } from '../pipeline/orchestrator.js';
+import type { Part } from '@google/genai';
+
+describe('render', () => {
+  it('should filter out previewNodeIds', async () => {
+    const mockNodes: ConcreteNode[] = [
+      {
+        id: '1',
+        type: NodeType.USER_PROMPT,
+        payload: {} as Part,
+      } as unknown as ConcreteNode,
+      {
+        id: '2',
+        type: NodeType.AGENT_THOUGHT,
+        payload: {} as Part,
+      } as unknown as ConcreteNode,
+      {
+        id: 'preview-1',
+        type: NodeType.USER_PROMPT,
+        payload: {} as Part,
+      } as unknown as ConcreteNode,
+    ];
+    const previewNodeIds = new Set(['preview-1']);
+
+    const orchestrator = {} as PipelineOrchestrator;
+    const sidecar = { config: {} } as ContextProfile; // No budget
+    const env = {
+      graphMapper: {
+        fromGraph: vi.fn((nodes: readonly ConcreteNode[]) =>
+          nodes.map((n) => ({ text: n.id })),
+        ),
+      },
+    } as unknown as ContextEnvironment;
+    const tracer = {
+      logEvent: vi.fn(),
+    } as unknown as ContextTracer;
+
+    const result = await render(
+      mockNodes,
+      orchestrator,
+      sidecar,
+      tracer,
+      env,
+      new Map(),
+      0,
+      previewNodeIds,
+    );
+
+    expect(result.history).toEqual([{ text: '1' }, { text: '2' }]);
+  });
+});