[Bug] Claude Code ignores subscription tier when $ANTHROPIC_API_KEY is set, requires separate API key variable name for billing

Bug Description

Conflicts in how claude code manages auth and billing

If you have $ANTHROPIC_API_KEY set either as a global env variable or in a project specific .env file AND you are a logged in Max subscriber, Claude bills the API key for ALL interactions with Claude code

Expected behavior:

• Only bill API keys for explicit and permitted project runtime calls (eg image or document processing, web research, etc)
• Everything else should remain Claude code billing with Max.

Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 2.0.53