Introduction to Reion

Reion is a backend API framework for building fast, type-safe HTTP services. It gives you file-based routing, a middleware pipeline, validation with Zod, and a CLI so you can go from zero to a running API in minutes.

This documentation covers what Reion is, why it exists, and how to use it.

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What is Reion?

Reion is a Node.js and Bun-ready API framework that focuses on:

• File-based routing — Define routes by placing files in your app directory; no manual router setup.
• Type-safe request/response — Validate bodies and responses with Zod and get full TypeScript inference.
• Middleware pipeline — Compose CORS, logging, and custom logic in a clear order.
• CLI-first workflow — Use reion create, reion dev, reion build, reion start, and reion add for projects and plugins.

You write your handlers and middleware in TypeScript; Reion handles routing, validation, body parsing, and server lifecycle. It runs on both Node.js (with tsx for .ts route files) and Bun natively.

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Why Reion?

• Ship faster — Minimal config, conventional project layout, and a single CLI. No framework lock-in for your HTTP layer; it's just a server and a router.
• Type safety — Request/response schemas with Zod mean fewer runtime bugs and better editor support.
• Flexible runtime — Use Node or Bun. Reion stays close to the platform instead of hiding it.
• Observability — Built-in request logging (Pino), tracing, and structured logging so you can debug and monitor without extra setup.
• Extensible — Plugins and an event bus let you add cross-cutting behavior without cluttering route handlers.

Whether you're building a small API or a larger service, Reion gives you structure without forcing a specific architecture.

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What does Reion provide?

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Who is Reion for?

Reion is for developers who want:

• A lightweight API framework that doesn't dictate your whole stack.
• TypeScript-first APIs with validation and good DX.
• Conventions (file-based routes, standard CLI) without magic.
• The option to run on Node or Bun with minimal changes.

It fits greenfield APIs, internal tools, and services where you care about clarity and control over the HTTP layer.

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How do I get started?

1. Create a project: run npx reion create my-app (or add reion to an existing app and create appDir/router/** yourself — default appDir is often ./src).
2. Run the dev server: reion dev (default port 3000, configurable with -p and -H).
3. Add routes as files under your appDir/router/; Reion will load and serve them.
4. Build for production: reion build, then run with reion start.

The rest of this documentation goes into setup, routing, validation, middleware, and advanced topics.

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What you'll find in these docs

• Get started — Install Reion, scaffold or wire a project, first routes and production build.
• Development guide — Folder layout, routes, middleware, security, events.
• Concepts — Request/response, validation, CLI, plugins API, tracing, and more.
• Plugins — First-party packages such as Cron and Better Auth.

Use the sidebar to jump to a section, or search (⌘K) to find a topic.

Quick links

Need help?

If something is unclear or you run into issues, check the relevant section in the sidebar or open an issue in the project repository.