Hey, this is a known issue. When you set an OpenAI API key, that setting applies to all model providers, not just OpenAI. So Sonnet (Anthropic) tries to authenticate using your OpenAI key and it fails.
This has been discussed in a few threads:
- Bug Report: After enabling custom models, Gemini models become unavailable
- After integrating the Open API key, the existing AI becomes unusable
Workaround: turn off the OpenAI API key in Settings > Models > API Keys before switching to non OpenAI models like Sonnet. It’s a bit tedious, but it’s the only reliable option right now.
The team knows about this. There’s no ETA yet, but your report helps us prioritize it.