When you run Claude Code it lets you pick between API key and Claude subscription login. It sounds like it found an API key in your env and is trying to use that. You may have to find a way to trigger a login to get you into your subscription account.
In the terminal based Claude Code, use /logout and /login to switch billing iirc.
Yep, that was it. I had an Anthropic API Key set in Zed. Resetting that (after typing /login in the agent window) did the trick!