So you were using it because your tests are going to look for it, think again, find another way.
Also, I suspect that is why I had a lot of "Extra usage".
For the whole long history:
https://github.com/anthropics/claude-code/issues/54497
Hope this saves some others a lot of headaches!
Isn't that literally what the point of this environment variable is for?
ie to provide your Anthropic API key to Claude Code so it uses that for billing