Squid MPP Adapter

AI agents and backend services can now accept and make payments across any EVM chain using the Squid MPP adapter — a Machine Payments Protocol (MPP) adapter powered by Squid to abstract away the complexity of cross-chain bridging.

Instead of managing bridges or writing complex multi-chain payment logic, developers can integrate the Squid MPP adapter to automatically handle bridging and paying for 402 resources in a single, seamless integration. Clients settle automatically by scanning their available balances across all Squid-supported EVM chains and routing through the Squid API to Tempo mainnet.

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Features

• Auto chain selection — scans all Squid-supported EVM chains for available balances and picks the best source token automatically

• Cross-chain bridging — routes tokens from any supported chain to Tempo mainnet via Squid Router

• HTTP 402 payment flow — standard MPP challenge/credential cycle: server issues a challenge, client pays and retries with a credential

Info The Squid MPP adapter currently supports EVM chains only.

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Getting Started

Requirements

• Node.js ≥ 18

• A Squid Integrator ID (issued on a limited basis upon review via the partnerships form)

Server integration

Protect any HTTP endpoint so that only clients who have paid can access it. Install the mppx library:

npm install mppx

Generate a secret key for credential signing:

openssl rand -hex 32

Add the output to your environment variables:

MPP_SECRET_KEY=<output from above>

Add mppx.charge() as middleware on any route you want to gate. The tempo() method configures the settlement token and recipient on Tempo mainnet:

import { Mppx, tempo } from "mppx"

const mppx = Mppx.create({
  secretKey: process.env.MPP_SECRET_KEY!,
  methods: [
    tempo({
      currency: "0x20c0000000000000000000000000000000000000", // PathUSD on Tempo
      recipient: process.env.RECIPIENT_ADDRESS!
    })
  ]
})

// Protect any route — amount is in PathUSD units
app.get("/resource", mppx.charge({ amount: "0.01" }), c => {
  return c.json({ data: "secret content" })
})

Unauthenticated requests receive an HTTP 402 with the charge parameters. Requests that include a valid credential pass through to the handler.

Learn more about protecting endpoints with MPP at the official MPP docs.

Client integration

Access any MPP-protected endpoint and pay from any supported EVM chain — no manual bridging required. Install @0xsquid/mpp alongside mppx and viem:

npm install @0xsquid/mpp mppx viem

You will need a funded agent wallet (USDC or any Squid-supported token on any supported chain) and your Squid Integrator ID.

# Private key of the agent wallet
PRIVATE_KEY=0x...

Wrap your fetch calls with Mppx.create() using squid() as the payment method. When a 402 is received, the library handles the entire bridge flow:

import { privateKeyToAccount } from "viem/accounts"
import { Mppx } from "mppx"
import { squid } from "@0xsquid/mpp"

const account = privateKeyToAccount(process.env.PRIVATE_KEY! as `0x${string}`)

const { fetch: mppxFetch } = Mppx.create({
  polyfill: false,
  methods: [
    squid({
      account,
      integratorId: "your-integrator-id"
    })
  ]
})

const response = await mppxFetch("https://mpp-server.com/resource")
console.log(await response.json())

squid(config) options

Option	Type	Required	Description
account	Account	Yes	A viem Account (e.g. from privateKeyToAccount)
integratorId	string	Yes	Your Squid integrator ID
onPayment	(summary: PaymentSummary) => void	No	Callback fired after a successful payment with amount, token, and source chain info

Learn more about MPP clients at the official MPP docs.

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Payment Flow

Client                Server              Squid API             Tempo Chain
  |                     |                     |                      |
  |-- GET /resource --> |                     |                      |
  |<- HTTP 402 -------- |                     |                      |
  |   { amount,         |                     |                      |
  |     currency,       |                     |                      |
  |     recipient }     |                     |                      |
  |                     |                     |                      |
  | [find optimal source token]               |                      |
  |                     |                     |                      |
  |-- get route quote ----------------------> |                      |
  |<- bridge route -------------------------- |                      |
  |                     |                     |                      |
  |-- submit bridge tx ---------------------> |                      |
  |-- poll bridge status -------------------> |                      |
  |                     |                     |-- pay on Tempo ----> |
  |                     |                     |<- payment tx hash -- |
  |<- payment tx hash ----------------------- |                      |
  |                     |                     |                      |
  |-- GET /resource --> |                     |                      |
  |   + credential      |-- verify tx -----------------------------> |
  |                     |<- payment confirmed ---------------------- |
  |<- 200 OK ---------- |                     |                      |