Introduction

WELD is a TypeScript-native HTTP client built around a single idea: the contract between your backend and frontend should be enforced automatically, not maintained by hand.

The Problem

Every frontend application faces the same cycle:

1. Backend changes a response shape
2. Frontend keeps reading the old shape
3. UI silently renders wrong data or crashes at runtime
4. Developer spends hours debugging

Type assertions like as User don’t help — they lie at runtime. And adding manual validation everywhere is tedious and error-prone.

The Solution

WELD solves this with four pillars working together in a single pipeline:

Pillar	What it does
E2E Type Safety	Your backend router type flows into every request. Wrong paths, wrong bodies, and wrong query params break at compile time.
Runtime Validation	Zod schemas validate the actual response at the network boundary. No more silent data corruption.
Offline-First	GET requests fall back to IndexedDB cache when offline. Mutations queue locally and replay when the network restores.
Request Deduplication	Concurrent requests for the same resource share one in-flight Promise. No duplicate server hits.

Philosophy

WELD follows Progressive Complexity — it’s as simple as a direct fetch() call for a landing page, and scales up to enterprise hexagonal architecture without changing your mental model.

// Zero-config — just works
const { promise } = api.get('v1/products')

// Full power — type-safe, validated, offline-resilient
const { signal, promise } = api.get('v1/products', z.array(ProductSchema), {
  offlineFallback: true,
  retry: { attempts: 3, delay: 300 },
})

Same API. Same client. Different levels of safety depending on what your project needs.