Anti-patterns

Giant route modules

Bad: One class with dozens of unrelated resources.
Better: Split into focused *Module classes and import each from main.

Calling listen inside route files

Bad: Instantiating FusionApp and calling listen() at the bottom of every module file.
Better: Single entrypoint owns lifecycle.

Treating packages as auto-routes

Bad: Expecting fusion add to expose HTTP endpoints automatically.
Better: Import the package and wire it explicitly from your route modules or middleware.

Circular route imports

Bad: users.py imports orders.py which imports users.py for helpers.
Better: Move shared helpers to a library package or src/shared/.

Business logic only in handlers

Bad: Hundreds of lines of domain logic inside get/post.
Better: Handlers map HTTP ↔ calls into helpers/services you own (plain functions/classes — Fusion has no DI container).

Relying on unverified JWT in production

Bad: app.use(bearer_jwt()) with default decode on a public API.
Better: Pass verify= that checks signature, expiry, and issuer.

Hard-coding resource path segments

Bad: @route("api/product/") duplicated across renames.
Better: @route("api/[module]/") with ProductModule.

Oversharing internal module state

Bad: Writing global mutable singletons imported everywhere.
Better: Per-request state for request-scoped data; explicit function parameters for everything else.