diff --git a/.gitignore b/.gitignore
index 04385494854..7f89b96eb78 100644
--- a/.gitignore
+++ b/.gitignore
@@ -61,4 +61,6 @@ gemini-debug.log
 .genkit
 .gemini-clipboard/
 .eslintcache
-evals/logs/
\ No newline at end of file
+evals/logs/
+
+evals/logs/
diff --git a/packages/sdk/src/agent.test.ts b/packages/sdk/src/agent.test.ts
new file mode 100644
index 00000000000..d85d671b4b9
--- /dev/null
+++ b/packages/sdk/src/agent.test.ts
@@ -0,0 +1,47 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { GeminiCliAgent } from './agent.js';
+import { GeminiCliSession } from './session.js';
+
+beforeEach(() => {
+  vi.restoreAllMocks();
+});
+
+describe('GeminiCliSession', () => {
+  it('propagates errors from dynamic instructions', async () => {
+    vi.spyOn(GeminiCliSession.prototype, 'initialize').mockImplementation(
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      async function (this: any) {
+        this.client = {
+          getHistory: () => [],
+          async *sendMessageStream () {},
+        };
+        this.initialized = true;
+      },
+    );
+
+    let callCount = 0;
+    const agent = new GeminiCliAgent({
+      instructions: () => {
+        callCount++;
+        throw new Error('Dynamic instruction failure');
+      },
+      model: 'gemini-2.0-flash',
+    });
+
+    const stream = agent.session().sendStream('Say hello.');
+
+    await expect(async () => {
+      for await (const _event of stream) {
+        // consume stream
+      }
+    }).rejects.toThrow('Dynamic instruction failure');
+
+    expect(callCount).toBe(1);
+  });
+});