## TL;DR

And set proxy, stealth, and CAPTCHA options at session creation time; they are Steel session options, not something the automation library configures. Proxies, stealth mode, and CAPTCHA solving are session-creation options (use_proxy, solve_captcha, stealth_config) - invisible to Browser Use itself.

## Steps

1. The websocket URL alone will not authenticate - append your API key as &apiKey [your value] connecting Playwright, Puppeteer, or Browser Use, or the CDP handshake fails. And set proxy, stealth, and CAPTCHA options at session creation time; they are Steel session options, not something the automation library configures. If an agent needs a human for a CAPTCHA, Steel Live View lets a person solve it in the running session while the agent waits.

## When to use

You are seeing this: The websocket URL alone will not authenticate - append your API key as &apiKey [your value] connecting Playwright, Puppeteer, or Browser Use, or the CDP handshake fails. Use this skill when you run into "Append your API key to the CDP URL - the websocket URL alone wont connect".

## When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

## Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

## Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.