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

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Handler shape

handler-options.ts
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) };
});

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Mix with standard oRPC handlers

You can put standard oRPC procedures and Effect procedures in the same router.
mixed-router.ts
import { os } from "@orpc/server";

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

  users: {
    get: effectProcedure.effect(function* ({ input }) {
      return yield* UsersRepo.findById(input.id);
    }),
  },
};
Use .handler(...) for plain synchronous or async procedures. Use .effect(...) when the handler needs Effect services, typed Effect failures, tracing, or fiber context.

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Next steps

Last modified on June 15, 2026