> ## Documentation Index
> Fetch the complete documentation index at: https://docs.gx402.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Payment flow

> Step-by-step payment lifecycle: create → sign → confirm → finalize and the responsibilities of each layer.

# Payment flow

This is the canonical flow we use across all platforms. It's the same x402 flow but wrapped by Gx402 middleware patterns so every client behaves the same.

## 1) Create (client → backend)

* Client requests `POST /create-payment` with `{ itemId, amount, userAddress, metadata }`.
* Server creates a `paymentSession`  and builds a **deterministic payload** (paymentId, amount, timestamp, chainId, optional nonce).
* Server may optionally call x402's create endpoint to register the session — not required if you only need a client-sign flow.

**Server response**

```json theme={null}
{ "paymentId": "pay_123", "payload": "string-to-sign", "expiresAt": 1670000000000 }
```