When you define an API route with typed parameters, payloads, and responses, KosmoJS generates a corresponding fetch client - automatically, as part of the same build step.

The result is a fully-typed client that mirrors your route definition exactly. Parameters, payload shape, response type - all derived from the same source. Change your API, and the client updates with it. No manual sync required.

🤖 What Gets Generated

Each route's client module exports:

🔹 HTTP method functions - GET, POST, PUT, etc., accepting parameters and payloads typed to match your route definition and returning typed response promises. (Details ➜ )

🔹 path and href utilities - construct relative or absolute URLs with proper parameter substitution and optional query string support. (Details ➜ )

🔹 validationSchemas - the same schemas used for server-side validation, exposed for client-side form validation with check, errors, errorMessage, errorSummary, and validate methods. (Details ➜ )

🏗️ Using the Generated Client

Import the fetch map and pick the client for your route by path:

pages/example/index.tsx

import fetchClients from "_/fetch";

const response = await fetchClients["users/[id]"].GET([123]);

The generator places its output in the lib directory alongside other generated artifacts (validation routines, OpenAPI spec). Everything is updated automatically in the background as you modify routes during development.