AISdkClient with Bedrock fails with 'modelApiKey is required' error

[tkhduracell]

Description

When using AISdkClient with Amazon Bedrock models in BROWSERBASE environment, Stagehand throws a StagehandAPIError: modelApiKey is required error during initialization.

Error

StagehandAPIError: modelApiKey is required
    at <anonymous> (/usr/src/app/node_modules/@browserbasehq/stagehand/dist/index.js:38340:19)

Root Cause

When passing an llmClient to Stagehand, the code at lines 38695-38699 sets modelClientOptions to baseClientOptions without adding an apiKey:

if (opts.llmClient) {
  this.llmClient = opts.llmClient;
  this.modelClientOptions = baseClientOptions;  // No apiKey added
}

However, later at line 39129, when env: "BROWSERBASE" and disableAPI: false, the code tries to access this.modelClientOptions.apiKey:

const { sessionId: sessionId2, available } = yield this.apiClient.init({
  modelName: this.modelName,
  modelApiKey: this.modelClientOptions.apiKey,  // undefined for Bedrock
  // ...
});

Bedrock models use AWS credential chains (via credentialProvider) rather than a simple apiKey property, so this.modelClientOptions.apiKey is undefined.

Reproduction

import { createAmazonBedrock } from '@ai-sdk/amazon-bedrock';
import { fromNodeProviderChain } from '@aws-sdk/credential-providers';
import { AISdkClient, Stagehand } from '@browserbasehq/stagehand';

const bedrock = createAmazonBedrock({
  region: 'eu-north-1',
  credentialProvider: fromNodeProviderChain(),
});

const bedrockClient = new AISdkClient({
  model: bedrock('eu.amazon.nova-pro-v1:0'),
});

const stagehand = new Stagehand({
  env: 'BROWSERBASE',
  llmClient: bedrockClient,
});

await stagehand.init(); // Error: modelApiKey is required

Workaround

Setting disableAPI: true bypasses the API client that requires modelApiKey:

const stagehand = new Stagehand({
  env: 'BROWSERBASE',
  llmClient: bedrockClient,
  disableAPI: true,  // Bypasses the modelApiKey requirement
});

Suggested Fix

When llmClient is provided, Stagehand should either:

1. Skip modelApiKey validation for custom LLM clients (similar to PR fix: allow custom LLM clients to skip modelApiKey validation in BrowserBase #966)
2. Extract credentials from the AI SDK model if available
3. Document that disableAPI: true is required for Bedrock/custom credential providers

Environment

• Stagehand version: 3.0.1
• Node version: 22.x
• Using @ai-sdk/amazon-bedrock with Bedrock models
• BROWSERBASE environment