Recommended project structure

Start with one module. Split by feature when handlers and dependencies grow:

my_chat_app/
├── app.py                 # FastAPI composition and lifespan
├── config.py              # environment parsing, no global credentials
├── bot.py                 # Bot and credential provider construction
├── routers/
│   ├── messages.py
│   ├── commands.py
│   └── cards.py
├── workspace_events.py    # separate EventsRouter tree
├── services/              # application/business logic
└── tests/

Routers depend on application services through handler dependency injection. Business entities such as polls, approvals, incidents, and AI assistants stay in application modules; they are recipes composed from Chattice primitives.

Keep transport assembly at the edge, handlers thin, and raw Google access localized. Use Dispatcher.lifespan(...) for resources that must start and close with the application.

Next: Mental model.