# `Mppx.create` \[Create a payment-aware fetch client] Creates a client-side payment handler. Returns a payment handler with a `fetch` function that automatically handles `402` Payment Required responses. By default, also polyfills `globalThis.fetch`. ## Usage ```ts twoslash import { Mppx, tempo } from 'mppx/client' import { privateKeyToAccount } from 'viem/accounts' const account = privateKeyToAccount('0x...') Mppx.create({ methods: [tempo({ account })], }) // Global fetch now handles 402 automatically const res = await fetch('https://mpp.dev/api/ping/paid') ``` ### Without polyfill Set `polyfill: false` to get a scoped fetch without modifying the global: ```ts twoslash import { Mppx, tempo } from 'mppx/client' import { privateKeyToAccount } from 'viem/accounts' const account = privateKeyToAccount('0x...') const mppx = Mppx.create({ methods: [tempo({ account })], polyfill: false, // [!code hl] }) // Use the returned fetch // [!code hl] const res = await mppx.fetch('https://mpp.dev/api/ping/paid') // [!code hl] ``` ### Manual credential handling For full control over the payment flow: ```ts twoslash import { Mppx, tempo } from 'mppx/client' import { privateKeyToAccount } from 'viem/accounts' const mppx = Mppx.create({ methods: [tempo()], polyfill: false, // [!code hl] }) // [!code hl:start] const response = await fetch('https://mpp.dev/api/ping/paid') if (response.status === 402) { const credential = await mppx.createCredential(response, { account: privateKeyToAccount('0x...'), }) const paidResponse = await fetch('https://mpp.dev/api/ping/paid', { headers: { Authorization: credential }, }) } // [!code hl:end] ``` ## Return type ```ts type Mppx = { /** Payment-aware fetch function that automatically handles 402 responses. */ fetch: Fetch /** The original, unwrapped fetch — bypasses payment interception. */ rawFetch: typeof globalThis.fetch /** The configured payment methods. */ methods: readonly Method.Client[] /** The transport used. */ transport: Transport /** Creates a credential from a payment-required response. */ createCredential: ( response: Response, context?: Context, ) => Promise } ``` ### `rawFetch` The original `fetch` function, before payment interception. Use `rawFetch` when you need to make requests that bypass the 402 handler—for example, probing a 402 endpoint for websocket auth tokens or calling APIs that return 402 for non-payment reasons. ```ts twoslash import { Mppx, tempo } from 'mppx/client' import { privateKeyToAccount } from 'viem/accounts' const account = privateKeyToAccount('0x...') const mppx = Mppx.create({ polyfill: false, methods: [tempo({ account })], }) // Bypass payment interception const raw = await mppx.rawFetch('https://api.example.com/ws-auth') // [!code focus] ``` ## Parameters ### fetch (optional) * **Type:** `typeof globalThis.fetch` * **Default:** `globalThis.fetch` Custom fetch function to wrap. ```ts twoslash import { Mppx, tempo } from 'mppx/client' import { privateKeyToAccount } from 'viem/accounts' const customFetch = globalThis.fetch const account = privateKeyToAccount('0x...') const mppx = Mppx.create({ fetch: customFetch, // [!code focus] methods: [tempo({ account })], }) ``` ### methods * **Type:** `readonly Method.Client[]` Array of payment methods to use. ```ts twoslash import { Mppx, tempo } from 'mppx/client' import { privateKeyToAccount } from 'viem/accounts' const account = privateKeyToAccount('0x...') const mppx = Mppx.create({ // [!code focus:start] methods: [tempo({ account })], // [!code focus:end] }) ``` ### onChallenge (optional) * **Type:** `(challenge: Challenge, helpers: { createCredential: (context?) => Promise }) => Promise` Called when a `402` challenge is received, before credential creation. Return a credential string to use it directly, or `undefined` to fall back to the default credential flow. ```ts twoslash import { Mppx, tempo } from 'mppx/client' import { privateKeyToAccount } from 'viem/accounts' const account = privateKeyToAccount('0x...') const mppx = Mppx.create({ methods: [tempo({ account })], onChallenge: async (challenge, { createCredential }) => { // [!code focus:start] console.log('Challenge received:', challenge.method) return createCredential() }, // [!code focus:end] }) ``` ### polyfill (optional) * **Type:** `boolean` * **Default:** `true` Whether to polyfill `globalThis.fetch` with the payment-aware wrapper. ```ts twoslash import { Mppx, tempo } from 'mppx/client' import { privateKeyToAccount } from 'viem/accounts' const account = privateKeyToAccount('0x...') const mppx = Mppx.create({ methods: [tempo({ account })], polyfill: false, // [!code focus] }) ``` ### transport (optional) * **Type:** `Transport` * **Default:** `Transport.http()` Transport to use for extracting challenges and attaching credentials. ```ts twoslash import { Mppx, Transport, tempo } from 'mppx/client' import { privateKeyToAccount } from 'viem/accounts' const account = privateKeyToAccount('0x...') const mppx = Mppx.create({ methods: [tempo({ account })], transport: Transport.mcp(), // [!code focus] }) ```