In the guide it mentions to set GEMINI_API_KEY but it looks like you actually need to set GOOGLE_API_KEY.
Once that is set, I still get this error:
API call failed: This model models/gemini-2.5-flash-lite-preview-09-2025 is no longer available to new users. Please update your code to use a newer model for the latest features and improvements.
changes to the model specified in hank.json do not alter that error, and I'm not sure where that specific model is named (doesn't show up in the repo).