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

# Effect procedures

> Write oRPC handlers as Effect generators or Effect-returning functions.

Use `.effect(...)` when a procedure implementation should run as an Effect.

Handlers can be generator callbacks, `Effect.fn(...)` callbacks, or functions that return an `Effect`.

```ts title="effect-procedure.ts" theme={null}
const getUser = effectProcedure
  .input(z.object({ id: z.string() }))
  .effect(function* ({ input }) {
    const user = yield* UsersRepo.findById(input.id);
    return user;
  });
```

The handler receives the normal oRPC handler options, including `input`, `context`, `errors`, `path`, `signal`, and metadata.

## Handler shape

```ts title="handler-options.ts" theme={null}
const procedure = effectProcedure.effect(function* ({
  input,
  context,
  errors,
  path,
  signal,
}) {
  yield* Effect.logDebug("handling procedure", { path });

  if (signal?.aborted) {
    yield* Effect.logDebug("request was already aborted");
  }

  return { input, context, path, errorKeys: Object.keys(errors) };
});
```

## Effect-returning handlers

Use a plain Effect-returning callback when you already have an `Effect` value, or when you want to keep a named `Effect.fn(...)` span inside the automatic procedure span.

```ts title="effect-returning.ts" theme={null}
const getUser = effectProcedure.effect(
  Effect.fn("users.get")(function* ({ input }) {
    return yield* UsersRepo.findById(input.id);
  }),
);

const listUsers = effectProcedure.effect(() =>
  Effect.gen(function* () {
    return yield* UsersRepo.list();
  }),
);
```

## Mix with standard oRPC handlers

You can put standard oRPC procedures and Effect procedures in the same router.

```ts title="mixed-router.ts" theme={null}
import { os } from "@orpc/server";

export const router = {
  health: os.handler(() => "ok"),

  users: {
    get: effectProcedure.effect(function* ({ input }) {
      return yield* UsersRepo.findById(input.id);
    }),
  },
};
```

<Tip>
  Use `.handler(...)` for plain synchronous or async procedures. Use
  `.effect(...)` when the handler needs Effect services, typed Effect failures,
  tracing, or fiber context.
</Tip>

## Next steps

* Add schemas with [Input and output schemas](/capabilities/input-output-schemas).
* Add services with [Service injection](/capabilities/service-injection).