> ## 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.

# Service injection

> Provide Effect layers to procedures and preserve service requirement type safety.

Use `.provide(layer)` to make Effect services available to downstream procedures.

```ts title="services.ts" theme={null}
import { Context, Effect, Layer } from "effect";

export class UsersRepo extends Context.Service<
  UsersRepo,
  {
    readonly findById: (
      id: string,
    ) => Effect.Effect<{ id: string; name: string }>;
  }
>()("UsersRepo") {}

export const UsersRepoLive = Layer.succeed(UsersRepo, {
  findById: (id) => Effect.succeed({ id, name: "Ada Lovelace" }),
});
```

```ts title="procedure.ts" theme={null}
import { eos } from "effect-orpc";

const effectProcedure = eos.provide(UsersRepoLive);

const getUser = effectProcedure.effect(function* () {
  const usersRepo = yield* UsersRepo;
  return yield* usersRepo.findById("1");
});
```

## Missing services are type errors

If a handler yields a service that was not provided, the procedure should fail to type-check.

```ts title="missing-service.ts" theme={null}
class MissingRepo extends Context.Service<
  MissingRepo,
  { readonly find: () => Effect.Effect<string> }
>()("MissingRepo") {}

const procedure = eos.provide(UsersRepoLive).effect(
  // @ts-expect-error MissingRepo was not provided.
  function* () {
    return yield* MissingRepo;
  },
);
```

## Provide multiple services

Merge services into one application layer, then provide that layer once.

```ts title="app-layer.ts" theme={null}
const AppLive = Layer.mergeAll(UsersRepoLive, Logger.pretty, CacheLive);

const effectProcedure = eos.provide(AppLive);
```

## Next step

Use request data to provide per-request services in [Request-scoped services](/effect-v4/capabilities/request-scoped-services).