# An x402 client SDK + middleware for Sui (testnet, feedback wanted)

**URL:** <https://forums.sui.io/t/an-x402-client-sdk-middleware-for-sui-testnet-feedback-wanted/49421>\
**Category:** SDK\
**Tags:** sui, feature\
**Created:** [August 24, 2026, 10:22am UTC](https://forums.sui.io/t/an-x402-client-sdk-middleware-for-sui-testnet-feedback-wanted/49421 "2026-08-24T10:22:20Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![yannickrocks](https://avatars.discourse-cdn.com/v4/letter/y/3be4f8/32.png) [@yannickrocks](https://forums.sui.io/u/yannickrocks)\
**Post date:** [August 24, 2026, 10:22am UTC](https://forums.sui.io/t/an-x402-client-sdk-middleware-for-sui-testnet-feedback-wanted/49421/1 "2026-08-24T10:22:21Z")

</div>

Stripe shipped Machine Payments in Feb 2026. AWS made CloudFront/WAF x402-aware in June. Both use the same open Linux Foundation spec, x402. Sui already has an `exact` scheme in that spec and one solid open-source facilitator (`DrVelvetFog/sui-x402-facilitator`, non-custodial, live on mainnet and testnet).

There’s already a marketplace-specific SDK on Sui: `@t2000/sui-x402` and `@t2000/serve` (`github.com/mission69b/t2000`), live on Sui mainnet, 23 stars, about 10k npm downloads a month. It’s a different design: v1-style `X-PAYMENT`/`X-PAYMENT-RESPONSE` headers with a custom `extra.suimpp` extension, the seller verifies and settles payments itself with no facilitator, the handler runs before settlement, it’s Next.js first, and it’s tied to their marketplace with a 5% fee on jobs. (There’s also `@altaga/x402-sui`, sponsored transactions, about 145 downloads a month.) What’s been missing is the standards-track option: the actual x402 v2 wire format and facilitator model the spec, and the foundation’s own EVM implementations, use. That’s what I built. One thing they have that I don’t yet: gasless payments. Planned.

**What’s here today**

- `@sui-x402/core`: Zod schemas derived from captured facilitator traffic, the header codec, reason codes with retry hints, and the seller core every adapter wraps.
- `@sui-x402/payer-sui`: the agent side. A `fetch()` that handles a 402 itself: gRPC coin discovery, transaction build with a simulated gas budget, a self-check on the simulated balance change, signing, and a strict no-double-pay rule. Testnet only by default, per-asset spend caps.
- `@sui-x402/hono`, `@sui-x402/express`, `@sui-x402/next`: seller middleware. Strict mode settles before your handler runs; a facilitator outage is a 503 with Retry-After, never free content. One conformance suite runs against all three adapters.
- Runnable examples for each framework, a Dockerfile plus Fly and Railway config for self-hosting the facilitator, and 349 tests.

It has moved real money on testnet: ten $0.01 USDC payments settled end to end through the reference facilitator (every push to the repo settles another through CI), verified on chain (for example digest `GE85dg3wNUdfRKJpFW9bBz2qkk4qgvgihWxMrFzDfc4T`, checkable on SuiVision).

A paid route, as shipped:

```ts
import { Hono } from "hono";
import { x402 } from "@sui-x402/hono";

const app = new Hono();
app.use("/paid/*", x402({
  payTo: "0xYOUR_SUI_ADDRESS",
  amount: "10000", // 0.01 USDC
  asset: "0xa1ec7fc00a6f40db9693ad1415d0c193ad3906494428cf252621037bd7117e29::usdc::USDC", // testnet USDC
  network: "sui:testnet",
  facilitator: "https://your-facilitator.example",
}));
app.get("/paid/quote", (c) => c.json({ symbol: "SUI", quote: "1.00" }));

```

And the paying side:

```ts
const payer = new SuiX402Payer({ client, signer: ed25519SignerFromEnv() });
const { response, receipt } = await payer.fetchWithReceipt("https://api.example/paid/quote");

```

**What it settles through:** the existing open-source reference facilitator, self-hosted (Fly/Railway config and a runbook are in the repo). This SDK doesn’t run its own facilitator and never touches custody: it only builds and signs the payer’s transaction and relays bytes unmodified.

**Status:** testnet only, v0.1.0 on npm. Nothing has touched mainnet; mainnet is behind explicit opt-ins on both sides.

**Three asks**

1. **Feedback** on the API shape (`payer.fetch()`, middleware config) while it’s early enough to change. Repo: `github.com/yannickrocks/sui-x402`.
2. **Sellers willing to pilot** a paid endpoint on testnet now. Ten lines and a funded test wallet are all it takes.
3. **The testnet network id.** The x402 Sui scheme spec only shows `sui:mainnet` in its example payload; no testnet identifier is defined. The reference facilitator and this SDK have both independently landed on `sui:testnet` (CAIP-2-style) as a stopgap. I’d like to propose formalizing it upstream. Does anyone know if there’s an existing spec issue tracking this, or should I open one?

Repo: `github.com/yannickrocks/sui-x402` · npm org: `sui-x402` · facilitator (testnet): `facilitator-production-1e79.up.railway.app`