Google has an agreement with Anthropic for the usage inside Android Studio.

> Unless previously approved, Anthropic does not allow third party developers to offer claude.ai login [..] for their products.

ref: https://code.claude.com/docs/en/agent-sdk.md

Yes there is a huge gray area. Yes people are getting away with it. That does not mean it's allowed. Anthropic could clarify their terms any day and they don't, on purpose.