When we published our analysis of x402 last week, we ended with an open question. The internet finally had a native payment layer built on stablecoins. But would agent commerce settle on crypto rails or card rails?

Stripe just answered: both. Today, Stripe and Tempo, a blockchain startup incubated by Stripe and Paradigm, launched the Machine Payments Protocol (MPP). It is an open standard that lets AI agents pay for services programmatically, settling on stablecoins, traditional cards, buy now pay later, and bitcoin over the Lightning Network. Over 100 services integrated at launch. Visa contributed the card payment specifications. Lightspark extended it to bitcoin.

The protocol solves the same problem x402 solves, but from a different starting position.

Today, an AI agent that wants to buy something faces a human-shaped checkout process. It needs to create an account, navigate a pricing page, choose a subscription tier, enter payment details, and set up billing. These steps were designed for people with browsers, not software with HTTP requests.

MPP provides a specification for agents and services to coordinate payments programmatically. An agent requests a resource from a service, API, MCP server, or any HTTP-addressable endpoint. The service responds with a payment request. The agent authorises payment. The resource is delivered.

The critical difference from x402: MPP does not require stablecoin settlement. Businesses using Stripe can accept payments from agents in stablecoins on the Tempo network, in fiat through cards, or through buy now pay later methods via Shared Payment Tokens (SPTs). Settlement happens in the business's default currency, on their existing payout schedule, through Stripe's standard infrastructure.

For businesses already on Stripe, integration takes a few lines of code using the PaymentIntents API. Transactions appear in the same dashboard, with the same fraud protection, tax calculation, reporting, and refund capabilities they already use.

Tempo is the blockchain underlying MPP's crypto settlement. Incubated by Stripe and Paradigm, Tempo's mainnet launched today alongside the protocol. It is purpose-built for machine payments, and its launch means MPP has its own chain rather than relying on existing networks.

The coalition extends beyond Stripe's own infrastructure. Visa developed the specifications for letting agents pay with credit or debit cards through MPP. Lightspark extended the protocol to bitcoin payments over the Lightning Network. Paradigm backed both Tempo and the protocol's development.

The payments directory at launch includes integrations with over 100 services spanning model providers, developer infrastructure, compute platforms, and data services. Alchemy, Dune Analytics, Merit Systems, and Parallel Web Systems are among them.

The early use cases are specific and telling. Browserbase lets agents spin up headless browsers and pay per session. PostalForm enables agents to pay to print and send physical mail. Prospect Butcher Co. in New York City lets agents order sandwiches for human pickup or delivery. These are small. They are also real, production transactions, not demos.

Both protocols solve agent-to-service payments in a single request cycle. Both are open standards. Both launched with serious coalitions. The differences are architectural and philosophical.

x402 embeds payments into HTTP itself. A server returns a 402 status code with payment metadata. The client constructs a signed stablecoin payment and retries with the payment in an HTTP header. Settlement is onchain, instant, and irreversible. The protocol is chain-agnostic but crypto-native. As we covered, the x402 Foundation now includes Coinbase, Cloudflare, Google, and Visa.

MPP settles through Stripe's existing infrastructure. Stablecoins settle on Tempo. Cards settle through Visa and Mastercard rails. BNPL settles through providers like Klarna and Affirm via Shared Payment Tokens. The protocol is payment-method agnostic. It does not care whether the agent pays with USDC, a Visa card, or a buy now pay later plan.

The practical implications are significant. x402 requires businesses to accept stablecoin payments and manage onchain settlement. MPP requires businesses to have a Stripe account. One is a bet that crypto rails will become the default for machine commerce. The other is a bet that the 4.5 million businesses already on Stripe will adopt agent payments faster if nothing else changes.

We have been mapping the agentic commerce stack all quarter. Discovery, trust, processing, settlement. MPP adds another settlement option to a layer that was already contested.

Here is where things stand. For discovery and checkout, OpenAI and Stripe's Agentic Commerce Protocol (ACP) is live in ChatGPT. Google's Universal Commerce Protocol (UCP) is rolling out. For trust and authorisation, Mastercard's Verifiable Intent framework and Visa's Trusted Agent Protocol handle agent authentication. For processing, Fiserv adopted both card network frameworks simultaneously.

Settlement was the layer with the clearest binary: stablecoins (x402) or cards (existing rails). MPP collapses that binary. A single protocol now settles on stablecoins, cards, BNPL, and bitcoin. The settlement layer war is not x402 versus card networks. It is x402 versus MPP, where MPP includes card networks as one of several options.

This has implications for the interoperability problem we identified in Q1. An agent using Google's UCP for discovery, Mastercard's Verifiable Intent for authorisation, and MPP for settlement can pay with whatever method the business accepts. The settlement layer becomes a routing decision, not an architecture decision.

MPP launched today. It is early. Several things remain unresolved.

Stripe dependency. MPP's fiat settlement runs through Stripe. That makes adoption easy for Stripe merchants and irrelevant for everyone else. x402 is infrastructure-agnostic. MPP is Stripe-dependent for everything except stablecoin settlement on Tempo.

Tempo's untested chain. The blockchain underlying MPP's crypto settlement launched its mainnet today. It has no transaction history, no stress-tested throughput, and no independent security audits at scale. x402 settles on established chains: Base, Ethereum, Solana, Stellar.

Real volume. x402 processes roughly $28,000 in daily volume, much of it testing. MPP launched with over 100 integrations but zero volume history. Both protocols are infrastructure ahead of demand. The question, as always, is whether agentic commerce scales fast enough to justify the rails.

Governance. Neither protocol addresses the liability, dispute resolution, and chargeback questions that remain unresolved across the agentic commerce stack. When an agent makes a bad purchase, who bears the cost? Onchain settlement is irreversible. Card settlement has chargeback mechanisms. That difference may matter more than the protocol design.

The settlement layer for agent commerce now has two credible candidates with production infrastructure.

x402 has Coinbase, Cloudflare, Google, and Visa. It settles on stablecoins across multiple established chains. It is HTTP-native, infrastructure-agnostic, and open. Its weakness is that it requires businesses to adopt crypto rails.

MPP has Stripe, Visa, Paradigm, Lightspark, and a purpose-built blockchain. It settles on stablecoins, cards, BNPL, and bitcoin. It is Stripe-native and payment-method agnostic. Its weakness is that it runs through a single company's infrastructure for fiat settlement.

They will likely coexist. x402 for crypto-native services, micropayment APIs, and decentralised infrastructure. MPP for the millions of businesses already on Stripe that want to accept agent payments without changing anything. The split will be determined by what the business already uses, not by which protocol is technically superior.

The internet reserved a payment status code for 29 years. In the space of one week, two competing protocols filled it. The settlement layer war for agentic commerce is now live.

Two protocols. Two coalitions. Two settlement philosophies. When your AI agent needs to pay for something, who decides which rails it uses: the agent, the merchant, or the infrastructure provider?