Installation

One versioned package with one entry per runtime; the root is the contract language.

Install the single result-rpc package with your package manager:

npm install result-rpc
# or: pnpm add result-rpc
# or: yarn add result-rpc
# or: bun add result-rpc

Requirements:

Node.js 20.19.5 or newer
TypeScript 5.4 or newer
React 18.3 or newer when using result-rpc/react

result-rpc brings better-result@^3.0.0 as a peer dependency — npm 7+ and pnpm install it automatically, so there is no extra install step for apps that don’t use better-result directly. The Result you compose is better-result’s class; result-rpc re-exports the surface (ok, err, gen, tryCatch, tryPromise, InferErr/InferOk/GenErr), and the shared class identity is what the boundary’s instanceof checks rely on. See Results for the division of labor and the FAQ for the identity rule.

The published declaration surface is tested with TypeScript 5.4, 5.9, and 7.0. The package is ESM-only.

One versioned package, one entry per runtime — the root is everything isomorphic (the contract language):

import {
  rpc,
  error,
  errorCatalog,
  err,
  ok,
  wire,
  defineLayer,
  defineService,
  resolveServices,
  type RouterInputs,
  type RouterOutputs,
} from "result-rpc";
import { createFetchHandler, serverRpc } from "result-rpc/server";
import { batchFetchTransport, createBrowserClient } from "result-rpc/client";
import { createQueryRuntime } from "result-rpc/query";
import { defineShell, layerShell, ResultRpcProvider, useResultQuery } from "result-rpc/react";
import { createParityClient } from "result-rpc/testing";

Entry	Use it for
`result-rpc`	Shared contracts, codecs, Results, error definitions, layers, services, and models
`result-rpc/server`	Procedure implementations, fetch handlers, and direct server clients
`result-rpc/client`	Browser clients, transports, and client-originated failures
`result-rpc/query`	The React-free query runtime, including server-side prefetching
`result-rpc/react`	Providers, hooks, shells, and hydration boundaries
`result-rpc/testing`	Test clients that exercise the real wire boundary

Keep implementations out of browser bundles. Put the contract in a shared module and import that value when creating a browser client. Do not import the implemented server router: it retains its handlers and may retain database drivers, environment access, and private error classes. See The client boundary.

Continue with the quickstart to build one complete query.