Building Multi-UI Apps

UI is a plugin. Build a reusable core first, then keep each interface as a thin adapter around it. Adding a new interface (CLI, GUI, API) should not change business logic.

Architecture

Presentation Layer (top)
├── Qt GUI (PySide6)    - consumes domain, handles display
├── CLI (typer)          - consumes domain, handles terminal I/O
└── API (FastAPI)        - consumes domain, handles HTTP (if needed)
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        v
Domain Layer (middle)
├── Managers             - orchestrate operations
├── Models               - dataclasses, TypedDicts
└── Services             - business rules, pure logic