(Local Draft) Add Fast to x402 ecosystem as infra

[xc93]

Description

Adds Fast to the x402 ecosystem page.

What is Fast?

Fast is payment infrastructure that powers autonomous systems and intelligent agents with programmatic transactions. It enables agents, APIs, merchants, and services to request, authorize, send, and settle payments — fully programmatically, across both crypto and fiat rails.

Fast is built for scenarios where payment must occur before a task executes or a service responds: an API charging $0.01 per request, an agent paying another agent for compute, a workflow paying per inference step.

x402 Integration

x402 is a first-class payment protocol adapter in the Fast SDK.

We maintain a complete x402 SDK at fastxyz/x402-sdk:

Package	Purpose
@fastxyz/x402-client	Pay for 402-protected content using Fast or EVM wallets
@fastxyz/x402-server	Protect API routes with x402 payment requirements
@fastxyz/x402-facilitator	Verify Fast certificates and settle EVM payments

Supported networks: fast-mainnet, base, arbitrum, ethereum

Payment Flows: EVM

Uses EIP-3009 transferWithAuthorization - client signs, facilitator settles.

Client                          Server                         Facilitator
  │                               │                                │
  │ Sign EIP-3009 authorization   │                                │
  │ (EIP-712 typed data)          │                                │
  │                               │                                │
  │ X-PAYMENT: { signature,       │                                │
  │   authorization: {from,to,    │                                │
  │   value,validAfter,           │                                │
  │   validBefore,nonce} }        │                                │
  │──────────────────────────────>│                                │
  │                               │  /verify                       │
  │                               │  - Recover signer from sig     │
  │                               │  - Check recipient matches     │
  │                               │  - Check amount sufficient     │
  │                               │  - Check timing valid          │
  │                               │  - Check on-chain balance      │
  │                               │────────────────────────────────>
  │                               │  { isValid: true }             │
  │                               │<────────────────────────────────
  │                               │                                │
  │                               │  /settle                       │
  │                               │  - Re-verify payment           │
  │                               │  - Check nonce not used        │
  │                               │  - Call transferWithAuth()     │
  │                               │  - Wait for confirmation       │
  │                               │────────────────────────────────>
  │                               │  { txHash: 0x... }             │
  │                               │<────────────────────────────────
  │  200 OK + content             │                                │
  │<──────────────────────────────│                                │

Payment Flows: Fast Network

Client submits transaction directly, sends certificate as proof.

Client                          Server                         Facilitator
  │                               │                                │
  │ Submit TokenTransfer to       │                                │
  │ Fast network               │                                │
  │ (transaction already on-chain)│                                │
  │                               │                                │
  │ X-PAYMENT: {                  │                                │
  │   transactionCertificate: {   │                                │
  │     envelope: "0x...",        │                                │
  │     signatures: [...]         │                                │
  │   }                           │                                │
  │ }                             │                                │
  │──────────────────────────────>│                                │
  │                               │  /verify                       │
  │                               │  - Check certificate structure │
  │                               │  - (TODO: on-chain verify)     │
  │                               │────────────────────────────────>
  │                               │  { isValid: true }             │
  │                               │<────────────────────────────────
  │                               │                                │
  │  200 OK + content             │  (no /settle needed -          │
  │<──────────────────────────────│   already on-chain)            │

Links

• Documentation: https://docs.fast.xyz/sdk-references/payment-protocol-adapters/x402-sdk
• SDK repo: https://github.com/fastxyz/x402-sdk
• Website: https://fast.xyz
• npm: @fastxyz/x402-client, @fastxyz/x402-server, @fastxyz/x402-facilitator

Checklist

• Working integration with x402
• Link to documentation and code examples
• Actively maintained
• Working mainnet integration

Files Changed

typescript/site/app/ecosystem/partners-data/fast/metadata.json  (new)
typescript/site/public/logos/fast.png                           (new)

[yzhang90]

LGTM