The 4 Pillars

Every request in WELD passes through a sequential 4-layer pipeline. Each layer solves one specific problem that has historically caused pain in frontend development.

api.get('v1/products', Schema, options)
         │
         ▼
┌─────────────────────────────────────────┐
│  LAYER 1 — DEDUPLICATION               │
│  Is there an identical request in       │
│  flight right now?                      │
│  YES → return the same Promise          │
│  NO  → continue                         │
└──────────────────┬──────────────────────┘
                   │
                   ▼
┌─────────────────────────────────────────┐
│  LAYER 2 — REACTIVITY                  │
│  Initialize signals                     │
│  Set status = 'loading'                 │
│  Notify all subscribers                 │
└──────────────────┬──────────────────────┘
                   │
                   ▼
┌─────────────────────────────────────────┐
│  LAYER 3 — NETWORK                     │
│  Online  → fetch() with AbortController │
│  Offline (GET) → read IndexedDB cache   │
│  Offline (mutation) → enqueue locally   │
└──────────────────┬──────────────────────┘
                   │
                   ▼
┌─────────────────────────────────────────┐
│  LAYER 4 — VALIDATION                  │
│  Schema provided → Zod safeParse        │
│  No schema → return raw data            │
│  Validation error → set error signal    │
└─────────────────────────────────────────┘

Each layer is independent and testable. You can use WELD without Zod (skips layer 4), without offline support (skips the offline branch of layer 3), and without signals (use the promise directly).