Project structure

Scaffold layout (Python)

fusion init --lang python creates a layout similar to:

my-app/
├── main.py                 # Required entry — listen() lives here
├── core/
│   └── settings.py         # Optional UPPERCASE overlay
├── src/
│   └── modules/
│       └── products/
│           └── products.py # Sample route module
├── fusion.dev.json         # Environment config + commands
├── fusion.stage.json
├── fusion.prod.json
└── fusion-framework.toml   # App metadata + installed [[modules]]

Exact files can vary by Fusion Tool version — treat the CLI output as source of truth when scaffolding.

File roles

Path	Owner	Role
`main.py`	You	Imports route modules, loads settings, registers middleware, calls `listen()`
`src/modules/**`	You	Route modules (`FusionBaseApi` classes)
`core/settings.py`	You	Python settings overlay (UPPERCASE names)
`fusion.<env>.json`	You	Host/port/swagger/commands for that environment — see Settings
`fusion-framework.toml`	You + CLI	App identity; `[[modules]]` after `fusion add`
`.fusion/modules/`	CLI	Vendored library packages (generated/managed)

Required vs optional

Required to run	Optional
Entrypoint that constructs `FusionApp` and listens	Extra environments
At least one registered route (or only Swagger/404 surface)	Library packages
Discoverable settings (or defaults)	`core/settings.py`

TypeScript / C#

Scaffolding differs by language but follows the same ideas: one entrypoint, route modules, environment JSON. See language getting-started pages and Fusion Tool.

Generated / vendored

Do not hand-edit vendored package trees under .fusion/modules/ as your source of truth — change the upstream package repo and re-add/update.