sanic-x402

Payment-gated routes for Sanic. Charge stablecoin micropayments for any endpoint with a single decorator, powered by the x402 protocol.

@app.get("/premium")
@paid("$0.01")
async def premium(request):
    return json({"data": "..."})

Why sanic-x402?

• One decorator to monetize an endpoint: no accounts, no API keys, no payment processor. Clients pay per request over HTTP 402.
• Built on the official x402 SDK: speaks both x402 v1 (X-PAYMENT) and v2 (PAYMENT-SIGNATURE) wire formats, works with any facilitator, and serves the built-in HTML paywall to browsers.
• Safe by default: payments settle only after your handler succeeds. Failed responses are never charged.
• AI-agent ready: agents holding a funded wallet can discover the price from the 402 challenge and pay autonomously.
• Stays out of your way: plain Sanic middleware and decorators, no base classes, no app rewrites.

Feature Overview

Quick Start

Install the package (the EVM extra covers the default Base/USDC setup):

pip install sanic-x402[evm]

Attach it to your app and mark a route as paid:

from sanic import Sanic
from sanic.response import json
from sanic_x402 import X402, paid

app = Sanic("Api")
X402(app, pay_to="0xYourReceivingAddress")  # Base Sepolia testnet by default

@app.get("/free")
async def free(request):
    return json({"hello": "world"})

@app.get("/premium")
@paid("$0.01")
async def premium(request):
    """Premium market data."""
    return json({"data": "..."})

Unpaid requests to /premium receive 402 Payment Required with a signed challenge. Paid requests are verified with the facilitator, your handler runs, and the payment settles on-chain. The settlement receipt is returned in the PAYMENT-RESPONSE header.

Going to production on Base mainnet:

X402(
    app,
    pay_to="0xYourReceivingAddress",
    network="eip155:8453",
    facilitator="https://your-facilitator.example",  # e.g. Coinbase CDP
)

The default facilitator is the testnet facilitator at https://x402.org/facilitator. It is an API base URL, not a web page: the bare path returns 404, while GET /facilitator/supported lists its capabilities.

Three Ways to Gate a Route

The @paid decorator (recommended). Apply it under the route decorator:

@app.get("/reports/<report_id>")
@paid("$0.25", description="Full analyst report", mime_type="application/json")
async def report(request, report_id):
    ...

A route kwarg. No extra import needed:

@app.get("/premium", ctx_x402="$0.05")
async def premium(request):
    ...

ctx_x402 accepts a bare price, a dict of @paid kwargs, an x402 PaymentOption, or a full RouteConfig.

Path patterns. Gate whole subtrees, like the official Express and FastAPI middlewares:

from sanic_x402 import X402, RouteConfig, PaymentOption

X402(app, routes={
    "GET /api/premium/*": RouteConfig(accepts=[
        PaymentOption(scheme="exact", pay_to="0x...", price="$0.10",
                      network="eip155:8453"),
    ]),
})

Supported Currencies

x402 is asset-agnostic: a payment option names any token on any supported network, and sanic-x402 exposes all of it.

USD money strings like "$0.01" are the simple path. They resolve to the network's default USD stablecoin from the SDK registry, which covers USDC on Base, Base Sepolia, Polygon, Arbitrum One, Arbitrum Sepolia, Monad, XDC and others, plus USDT0 (Stable), MegaUSD (MegaETH), Mezo USD, and more.

Any other token (EURC, DAI, or your own ERC-20/SPL asset) works via asset=:

@paid(
    "€0.50",
    asset="0x808456652fdb597867f38412077A9182bf77359F",  # EURC on Base
    asset_decimals=6,
    asset_extra={"name": "EURC", "version": "2"},  # token's EIP-712 domain
)
async def handler(request): ...

The price is converted to atomic units with asset_decimals, and currency symbols or codes in the string are stripped. For full control, pass an AssetAmount directly as the price:

from sanic_x402 import AssetAmount

@paid(AssetAmount(amount="500000", asset="0x8084...", extra={"name": "EURC", "version": "2"}))

Two practical constraints apply. On EVM networks with the exact scheme, the token must support EIP-3009 transferWithAuthorization (USDC and EURC do) or the Permit2 flow. And your facilitator must support the scheme and network pair; check GET <facilitator>/supported. The v2 spec also allows ISO 4217 codes (like "USD") as the asset for fiat facilitators.

Advanced Usage

@paid(lambda ctx: "$1.00" if ctx.adapter.get_query_param("hd") else "$0.10")

from sanic_x402 import PaymentOption, paid

@paid(accepts=[
    PaymentOption(scheme="exact", pay_to="0xEvm...", price="$0.01",
                  network="eip155:8453"),
    PaymentOption(scheme="exact", pay_to="Sol...", price="$0.01",
                  network="solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp"),
])
async def handler(request): ...

from x402.mechanisms.svm.exact import ExactSvmServerScheme

X402(app, pay_to="...", schemes=[
    ("eip155:*", ExactEvmServerScheme()),
    ("solana:*", ExactSvmServerScheme()),
])

@app.get("/premium")
@paid("$0.01")
async def premium(request):
    payment = request.ctx.x402
    return json({"paid_on": payment.requirements.network})

from sanic_x402 import PaywallConfig

X402(app, pay_to="...", paywall=PaywallConfig(app_name="My API", testnet=True))

from sanic_ext import Extend
from sanic_x402.ext import X402Extension

app.config.X402_PAY_TO = "0xYourAddress"
app.config.X402_NETWORK = "eip155:8453"
app.extend(extensions=[X402Extension])

How It Works

1. A client requests a gated route without payment.
2. sanic-x402 responds 402 with a challenge (JSON for agents, an HTML paywall for browsers) describing price, asset, network, and receiver.
3. The client signs a payment authorization and retries with a PAYMENT-SIGNATURE header.
4. The payment is verified with the facilitator, then your handler runs.
5. On a successful response the payment settles on-chain and the receipt is attached as a PAYMENT-RESPONSE header.

Semantics and Caveats

• No charge on failure. If the handler raises or returns a 4xx/5xx, settlement is skipped and the payment authorization expires unspent.
• Settlement runs after the handler, in response middleware. If settlement fails, the client receives 402 with the failure receipt instead of being charged for the body.
• Streaming. Responses returned from the handler (including ResponseStream) settle before the body is sent. Mid-handler await request.respond() triggers settlement at respond() time, so prefer returned responses on paid routes.
• Websockets are not gated. A warning is logged if @paid is applied to one.
• Facilitator sync is lazy. Capabilities are fetched on the first protected request; pass sync_facilitator_on_start=False to disable.

Development

uv sync
uv run pytest

Tests run fully offline against a fake facilitator.

Resources

• x402 protocol
• x402 documentation
• x402 specification
• x402 Python SDK
• Sanic documentation

License

MIT. See LICENSE.