diff --git a/src/models/openai.baseurl.test.ts b/src/models/openai.baseurl.test.ts
new file mode 100644
index 0000000..d01edf4
--- /dev/null
+++ b/src/models/openai.baseurl.test.ts
@@ -0,0 +1,28 @@
+import { describe, expect, it, vi } from 'vitest';
+
+let capturedOptions: any;
+
+vi.mock('openai', () => {
+  class OpenAI {
+    constructor(options: any) {
+      capturedOptions = options;
+    }
+  }
+  return { default: OpenAI };
+});
+
+describe('OpenAIClient', () => {
+  it('passes baseURL through to the OpenAI SDK', async () => {
+    const { OpenAIClient } = await import('./openai.js');
+
+    capturedOptions = undefined;
+    new OpenAIClient({
+      model: 'gpt-4.1',
+      apiKey: 'sk-test',
+      baseURL: 'https://example.com/v1',
+    });
+
+    expect(capturedOptions).toBeDefined();
+    expect(capturedOptions.baseURL).toBe('https://example.com/v1');
+  });
+});