elysia-beta-headers

Elysia plugin that makes it easy to use Request header values to feature gate beta functionality. Inspired by how OpenAI and Anthropic use beta headers for their experimental endpoints.

Installation

bun add @p0u4a/elysia-beta-headers

Quickstart

import Elysia from "elysia";
import { betaHeaders } from "../src/index.ts";

// Define your beta features
const BETA_FEATURES = ["newDashboard", "darkMode", "experimentalApi"] as const;

const app = new Elysia()
  .use(
    betaHeaders({
      headerName: "X-MyApp-Beta", // The header that your API consumer will set to request beta features
      features: BETA_FEATURES,
    })
  )
  // Now beta feature flags are available in the route context with full type safety
  .get("/dashboard", ({ newDashboard }) => {
    if (newDashboard) {
      return { version: "v2", message: "Welcome to the new dashboard!" };
    }
    return { version: "v1", message: "Classic dashboard" };
  })
  .listen(3000);

console.log(`Server running at http://localhost:${app.server?.port}`);

// Example request
// curl -H "X-Beta-Features: newDashboard" http://localhost:3000/

Configuration

headerName

The name of the HTTP header to read beta features from.

Example: "X-MyApp-Beta"

features

Array of valid bet header values.

Example: ["featureA", "featureB", "featureC"]

separator (optional)

Separator used to split multiple features in the header value.

Default: ,

Contributing

Contributions welcome.