The Twitch Extension JWT Mistake That Causes 401s on Every Request

I recently shipped a production Twitch extension. This is the mistake that cost me the most time. If you've tried to build a Twitch extension with a backend service (called an EBS — Extension Backend Service), you may have run into a wall of mysterious 401 errors that no amount of Stack Overflow searching seems to fix. The cause is almost certainly this. The Mistake Twitch signs the JWTs it sends to your EBS using your extension's secret key. You verify these JWTs in your backend using a library