diff --git a/packages/playwright-core/src/server/trace/viewer/traceViewer.ts b/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
index 4436227623..3f322e7125 100644
--- a/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
+++ b/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
@@ -144,10 +144,13 @@ export async function installRootRedirect(server: HttpServer, traceUrls: string[
     response.setHeader('Location', urlPath);
 
     if (process.env.OPENAI_API_KEY)
-      response.setHeader('Set-Cookie', `openai_api_key=${process.env.OPENAI_API_KEY}`);
-
+      response.appendHeader('Set-Cookie', `openai_api_key=${process.env.OPENAI_API_KEY}`);
+    if (process.env.OPENAI_BASE_URL)
+      response.appendHeader('Set-Cookie', `openai_base_url=${process.env.OPENAI_BASE_URL}`);
     if (process.env.ANTHROPIC_API_KEY)
-      response.setHeader('Set-Cookie', `anthropic_api_key=${process.env.ANTHROPIC_API_KEY}`);
+      response.appendHeader('Set-Cookie', `anthropic_api_key=${process.env.ANTHROPIC_API_KEY}`);
+    if (process.env.ANTHROPIC_BASE_URL)
+      response.appendHeader('Set-Cookie', `anthropic_base_url=${process.env.ANTHROPIC_BASE_URL}`);
 
     response.end();
     return true;
diff --git a/packages/trace-viewer/src/ui/llm.tsx b/packages/trace-viewer/src/ui/llm.tsx
index 29d607e2d2..1532ed4bc8 100644
--- a/packages/trace-viewer/src/ui/llm.tsx
+++ b/packages/trace-viewer/src/ui/llm.tsx
@@ -221,15 +221,15 @@ export class Conversation {
 const llmContext = React.createContext<LLMChat | undefined>(undefined);
 
 export function LLMProvider({ children }: React.PropsWithChildren<{}>) {
-  const cookies = useCookies();
+  const cookiePairs = useCookies();
   const chat = React.useMemo(() => {
-    for (const [name, value] of cookies) {
-      if (name === 'openai_api_key')
-        return new LLMChat(new OpenAI(value));
-      if (name === 'anthropic_api_key')
-        return new LLMChat(new Anthropic(value))
-    }
-  }, [cookies]);
+    const cookies = Object.fromEntries(cookiePairs);
+    console.log({ cookies })
+    if (cookies.openai_api_key)
+      return new LLMChat(new OpenAI(cookies.openai_api_key, cookies.openai_base_url));
+    if (cookies.anthropic_api_key)
+      return new LLMChat(new Anthropic(cookies.anthropic_api_key, cookies.anthropic_base_url));
+  }, [cookiePairs]);
   return <llmContext.Provider value={chat}>{children}</llmContext.Provider>;
 };
 
diff --git a/packages/web/src/uiUtils.ts b/packages/web/src/uiUtils.ts
index 57f32720cc..b5f7aeffa1 100644
--- a/packages/web/src/uiUtils.ts
+++ b/packages/web/src/uiUtils.ts
@@ -250,7 +250,7 @@ export function useFlash(): [boolean, EffectCallback] {
 }
 
 export function useCookies() {
-  return document.cookie.split(";").filter(v => v.includes("=")).map(kv => {
+  return document.cookie.split("; ").filter(v => v.includes("=")).map(kv => {
     const separator = kv.indexOf("=");
     return [kv.substring(0, separator), kv.substring(separator + 1)];
   }) 
diff --git a/tests/playwright-test/ui-mode-llm.spec.ts b/tests/playwright-test/ui-mode-llm.spec.ts
index dc264da40b..69e318dd69 100644
--- a/tests/playwright-test/ui-mode-llm.spec.ts
+++ b/tests/playwright-test/ui-mode-llm.spec.ts
@@ -21,7 +21,23 @@ test.describe.configure({ mode: 'parallel', retries });
 test.beforeAll(() => process.env.PW_EXPERIMENTAL_SERVICE_WORKER_NETWORK_EVENTS = '1');
 test.afterAll(() => delete process.env.PW_EXPERIMENTAL_SERVICE_WORKER_NETWORK_EVENTS);
 
-test('openai', async ({ runUITest }) => {
+test('openai', async ({ runUITest, server }) => {
+  server.setRoute('/v1/chat/completions', async (req, res) => {
+    res.setHeader('Access-Control-Allow-Origin', '*');
+    res.setHeader('Access-Control-Allow-Headers', '*');
+    if (req.method === 'OPTIONS')
+      return res.end();
+
+    expect(req.headers.authorization).toBe('Bearer fake-key');
+    expect((await req.postBody).toString()).toContain(`- button \\"Submit\\"`);
+    const event = {
+      object: 'chat.completion.chunk',
+      choices: [{ delta: { content: 'This is a mock response' } }]
+    };
+    res.setHeader('Content-Type', 'text/event-stream');
+    res.write(`data: ${JSON.stringify(event)}\n\n`);
+  });
+
   const { page } = await runUITest({
     'a.test.ts': `
       import { test, expect } from '@playwright/test';
@@ -31,19 +47,8 @@ test('openai', async ({ runUITest }) => {
       });
     `,
   }, {
-    OPENAI_API_KEY: 'fake-key'
-  });
-
-  await page.context().route('https://api.openai.com/**', async (route, request) => {
-    expect(await request.headerValue('authorization')).toBe('Bearer fake-key');
-    expect(request.postData()).toContain(`- button \\"Submit\\"`);
-    const event = {
-      object: 'chat.completion.chunk',
-      choices: [{ delta: { content: 'This is a mock response' } }]
-    };
-    await route.fulfill({
-      body: `\n\ndata: ${JSON.stringify(event)}\n\n`
-    });
+    OPENAI_API_KEY: 'fake-key',
+    OPENAI_BASE_URL: server.PREFIX,
   });
 
   await page.getByTitle('Run all').click();