Reusable packages

What

A Fusion library package (often called a “module” in the CLI) is a publishable library with a fusion.module.toml manifest. It is installed into an application with fusion add and consumed via normal language imports.

It is not automatically mounted as HTTP routes.

Why

Reuse middleware helpers, validators, clients, or native code across many Fusion apps without copying files.

How

Full CLI reference: Modules.

flowchart LR
  init["fusion module init"] --> repo[Package repository]
  repo --> gh[GitHub]
  gh --> add["fusion add --github"]
  add --> vendor[".fusion/modules/<id>/"]
  vendor --> import[Import in app code]

Create

fusion module init --lang python --name jwt --description "JWT helpers"

Install into an app

From a project that has fusion-framework.toml:

fusion add --github OWNER/fusion-jwt-mod@v1.0.0

Use

from fusion_jwt_mod import some_helper

Call helpers from route modules, middleware, or startup — whatever fits your design.

Application module vs reusable package

Best practices

• Keep packages focused (one concern)
• Document public exports in the package README
• Version with tags for fusion add …@vX.Y.Z
• Prefer Rust scaffolds when one native core must serve Python and Node hosts

See also

• FMA
• CLI Modules