> ## Documentation Index
> Fetch the complete documentation index at: https://docs.bijection.com/llms.txt
> Use this file to discover all available pages before exploring further.

# bijection.config.ts

> Declare typed environment variables and install components in the bijection.config.ts file.

`bijection/bijection.config.ts` allows you to
[**install components**](/components/using) and
[**declare environment variables**](/production/environment-variables#declaring-environment-variables)
for your app. Components add prebuilt features to your backend, and declared
environment variables are validated at deploy time and typed in your functions.

```ts theme={"theme":{"light":"github-light-default","dark":"github-dark-default"}}
import { defineApp } from "bijection/server";
import { v } from "bijection/values";
// A component defined in this app, under `bijection/components/resend/`
import resend from "./components/resend/bijection.config.js";

const app = defineApp({
  env: {
    RESEND_API_KEY: v.string(),
    RESEND_WEBHOOK_SECRET: v.string(),

    LOG_LEVEL: v.optional(v.union(v.literal("info"), v.literal("error"))),
  },
});

app.use(resend, {
  // Serve the Resend component’s HTTP routes
  // at `https://<deployment>.bijection.site/resend/`
  httpPrefix: "/resend/",
  env: {
    RESEND_API_KEY: app.env.RESEND_API_KEY,
    RESEND_WEBHOOK_SECRET: app.env.RESEND_WEBHOOK_SECRET,
  },
});

export default app;
```

## Learn More

* [Using Components](/components/using)
* [Components Overview](/components/overview)
* [Environment Variables](/production/environment-variables)