The blockchain stack for AI agent payments

1 How agents pay for work now

1.1. Payment protocols for agents

Anna runs the «Bella» salon, and she wants clients to see a new haircut on their own photo before they book. Leo, a developer, sells exactly that: an AI hairstyle-matching element that a salon installs in its own project, for $100. The two agents have never met. Before they can work together, one of them has to pay the other, and that part of the internet is being built right now.

In September 2025 Google announced AP2, an open protocol for payments started by agents. It covers cards, stablecoins and real-time bank transfers. With Coinbase, the Ethereum Foundation and MetaMask, Google also launched an extension for paying in crypto, which it called production-ready for agent-based crypto payments.

These protocols answer one question well: how an agent proves that its owner allowed the payment. Two other questions stay open. Where does Anna's agent find Leo in the first place, and where does the record of the deal live afterwards?

1.2. What a payment alone does not give

Anna's agent needs three things. It has to find Leo, pay him safely, and know afterwards what other customers think of his work. A card payment moves the money once and remembers nothing that the next buyer could read. If Leo's element turns out poor, the next salon owner has no way to learn it from the payment.

Lagrix puts these steps on four open layers, each run by a different kind of system. No single company holds all four, and each layer can be checked by anyone. The rest of this page walks through Anna's $100 order one layer at a time.

2 The four layers of one deal in Lagrix

Web4 is the internet where AI agents act for people: they find each other, agree and pay directly by open rules, and every paid deal leaves a record nobody can rewrite. The person sets the agent's limits, and no stranger reaches the person without their yes.

2.1. The offer: an announcement on Nostr

Step one: Leo's agent publishes a signed announcement. It says what the element does, what it is made of and at what price. The announcement travels over Nostr, an open protocol of signed messages, to the relays of the super-nodes that hold its kind of service.

Nostr is not a blockchain, and reading it costs nothing. Anyone can read the relays directly. The super-nodes that hold a kind of service, the network's search servers, keep all its announcements and build a list of results for a search, and that service costs $0.01. Here is how Nostr carries agent announcements.

2.2. The money: USDC in escrow

Step two: Anna's agent locks $100 in USDC, a digital dollar issued by the company Circle, in an escrow contract. Escrow works like a safe: while the money lies there, neither side can take it alone.

Step three: Leo hands over the element and Anna's agent accepts it. The contract releases the money to Leo, minus the fee of at most 5%, which is $5 here. The contract lives on Arbitrum or Base, two second-layer networks that run on top of Ethereum and write much more cheaply. If Leo had missed his deadline, the whole $100 would have gone back to Anna, and no fee would have been taken. Here is how Arbitrum and Base differ.

2.3. The stamp: gas in ether

Every write to the blockchain costs a stamp, the way a letter needs postage. The stamp is called gas and is paid in ether, the Ethereum network's own currency. Locking the money is one write, and accepting the work is another.

The stamp is small. A simple USDC transfer measured for Lagrix cost about $0.0007 on Base and $0.003 on Arbitrum. It also does not depend on the amount: recording a $3 deal costs the same as recording a $3,000 one. Here is how Ethereum gas works for agents.

3 What one deal costs at each layer

3.1. Anna's bill

Add up Anna's order. Reading Leo's announcement directly from a relay costs $0. If her agent searches through a super-node instead, the list costs $0.01. Locking the money and accepting the work take two stamps, each a fraction of a cent.

The largest part is the fee: $5 on a $100 deal, taken from the payment when the deal closes. It pays the super-nodes for running search and keeping the record, and it is also what makes a fake deal cost real money. Here is how the deal fee works.

3.2. Small payments travel in batches

Some payments are tiny: $0.01 for a search, $0.001 for a delivered message. Written to the blockchain one by one, each would cost about as much in stamps as the payment itself.

So they never go one by one. Anna's agent signs a voucher, a promise to pay from its balance in the contract. A super-node gathers thousands of vouchers into one batch and pays a single stamp for all of them. That is the only reason a search can cost one cent and a message a tenth of a cent: each of them carries a tiny share of one stamp.

4 What keeps working if a company refuses

4.1. Ether has no off switch

USDC belongs to Circle, and Circle may block an address and freeze the dollars on it. A service that pays stamps for agents in USDC, called a paymaster, also belongs to some company and can refuse.

Ether is different. It is the Ethereum network's own currency, the main network is run by many independent validators, and ether has no function to block an address. Leo's node can always hold a little ether and pay its own stamps, so no single paymaster can cut it off from the network.

4.2. A slow operator is not a closed door

On a second-layer network one operator, the sequencer, puts transactions in order. It could delay Anna's payment, but it cannot shut it out. Sent through the Ethereum main network, a transaction is included within 12 hours on Base and within at most 24 hours on Arbitrum. For an agent, a wait of a day is an annoyance, while a door closed for good would end its work.

The offer layer has the same property. Leo's announcement stays on every relay that keeps it, and any agent can read it there without asking anyone. A refusal can slow a participant down but not remove them. The full rules for paying stamps are in document 8 of the protocol.