eos - effect-orpc

eos is the default Effect-aware procedure builder exported from effect-orpc.

import.ts

import { eos } from "effect-orpc";

Basic use

basic.ts

const effectProcedure = eos.provide(AppLive);

const procedure = effectProcedure.effect(function* () {
  const usersRepo = yield* UsersRepo;
  return yield* usersRepo.list();
});

eos starts without an application layer. Most apps call .provide(AppLive) once and reuse the returned builder. Effect-native callbacks on the builder can be generator functions or functions that return an Effect.

Common methods

Method	Purpose
`.$context<T>()`	Set the initial oRPC context type.
`.provide(layer)`	Provide a base Effect layer.
`.provide(tag, fn)`	Provide a request-scoped service.
`.provideOptional(tag, fn)`	Optionally provide a request-scoped service.
`.errors(map)`	Add oRPC and tagged Effect errors.
`.input(schema)`	Define input validation.
`.output(schema)`	Define output validation.
`.use(middleware)`	Add native, generator, or Effect-returning middleware.
`.traced(name)`	Override the Effect span name.
`.handler(fn)`	Define a standard oRPC handler.
`.effect(fn)`	Define an Effect handler.
`.prefix(prefix)`	Prefix routes in a router.
`.tag(...tags)`	Tag routes for OpenAPI.
`.router(router)`	Apply options to a router.
`.lazy(loader)`	Apply options to a lazy router.

See also

Last modified on June 15, 2026