Skip to main content

Documentation Index

Fetch the complete documentation index at: https://docs.launchtoday.dev/llms.txt

Use this file to discover all available pages before exploring further.

​
Overview

Launch uses tRPC to share API types across the API, mobile app, and web app. The API defines a single router, and both clients import the router type directly from the API package.

​
Prerequisites

  • API package built and available
  • apps/api/src/types.ts exports AppRouter

​
Steps

  1. Define routers in apps/api/src/router.ts
  2. Export AppRouter from apps/api/src/types.ts
  3. Import AppRouter in mobile and web

​
Single source of truth

  • Router definition: apps/api/src/router.ts
  • Type export: apps/api/src/types.ts
// apps/api/src/types.ts
export type { AppRouter } from "./router";
Because apps/api/package.json exposes types, both clients can import AppRouter from the api package without any manual codegen.

​
Mobile client usage

// apps/mobile/lib/trpc/client.ts
import type { AppRouter } from "api";
import { createTRPCReact } from "@trpc/react-query";

export const trpc = createTRPCReact<AppRouter>();

​
Web client usage

// apps/web/lib/trpc.ts
import type { AppRouter } from "api";
import { createTRPCReact } from "@trpc/react-query";

export const trpc = createTRPCReact<AppRouter>();

​
Extending routers safely

  1. Add a new router in apps/api/src/routers/
  2. Register it in apps/api/src/router.ts
  3. Use the typed hooks on mobile/web immediately
Type safety is automatic as long as:
  • The client imports AppRouter from api
  • You avoid any or casting tRPC hooks

​
Common pitfalls

  • Missing router registration: If a router isn’t added to appRouter, clients won’t see it.
  • Casting away types: Avoid as any or as unknown at the tRPC boundary.
  • Out-of-date builds: Restart the mobile/web dev server after adding new procedures to pick up updated types.

​
Troubleshooting

  • Types missing: ensure apps/api/package.json points to types
  • Type errors in mobile: restart dev server to pick up changes

​
Next Steps