Author: Clow, Plain Language Blockchain

An AI wrote a piece of code that needed data to validate.

It sent an HTTP request, and the server returned a number: 402.

Then, it paid 0.001 dollars using USDC. Within less than a second, the data came back.

This transaction had no account, no password, no bank card, no KYC. The entire process involved no human participation.

This is no longer science fiction. By the end of 2025, the x402 protocol handled over 100 million such transactions; in the last 30 days, there were an additional 15 million.

The "Payment Code" that slept for thirty years

In 1990, the drafters of the HTTP protocol specifically left a slot for a status code: 402, Payment Required.

The meaning is very straightforward—"You need to pay to enter here."

But this status code was never officially used. It just hung in the protocol documentation, sleeping for thirty-four years.

The reason is not complicated: the first builders of the internet never imagined that one day it would be machines paying the bills. Credit cards, bank accounts, KYC verification—these payment infrastructures were designed for humans and became completely ineffective in the face of autonomously running code.

AI Agents need to call APIs, purchase data, and obtain computing power at millisecond speed; the account registration and transaction fee thresholds of traditional payments act as an impenetrable wall.

By 2025, three conditions would align.

The total supply of stablecoins surpassed 300 billion dollars, L2 networks represented by Base reduced single transaction costs to sub-cent levels; the AI Agent ecosystem led by OpenAI and Anthropic began large-scale commercialization; and engineers at Coinbase unearthed that dusty 402, deciding to activate it.

In May 2025, Coinbase and Cloudflare officially launched the x402 protocol. In September, they collaborated to announce the establishment of the x402 Foundation. A forgotten status code returned to the center of the internet. Cloudflare manages about 20% of global web traffic—this means that x402 had ample infrastructure entry from day one.

For the first time, machines learned to pay

The design of x402 is surprisingly simple.

An AI Agent initiates an HTTP request, the server returns the 402 status code, along with the payment request: how much, which chain, which token. The Agent uses EIP-712 encrypted signatures for authorization, inserting the payment information into the request header and resending it; the server verifies and returns the resources once approved.

The entire process takes less than a second, with no account, no subscription, and no API key.

This turns "payment" into a part of the internet. Like GET or POST, it is merely an HTTP action; any service can charge machines by adding a line of middleware.

Data proves that this logic works. About seven months after the protocol was released, it processed over 100 million transactions. According to the Cambrian Network Q1 2026 report, over the past 30 days there were more than 15 million transactions, with over 400,000 buyers and more than 80,000 sellers. The AI Agent community of Virtuals Protocol is the largest single source of transactions, autonomously settling cooperation fees among Agents on the protocol.

On December 11, 2025, x402 V2 went live. This upgrade moved the protocol from "usable" to "user-friendly": it supports multi-chain parallel transactions including Base, Solana, Avalanche, introduces a Session mechanism (where wallets become identity credentials, and repeated access does not require on-chain interactions each time), and connects the ACH bank transfer and credit card networks—bringing together the payment systems of Web2 and Web3 for the first time within this protocol.

Google subsequently integrated x402 into the Agent2Agent (A2A) protocol, releasing the Agentic Payments Protocol (AP2); machine payments are becoming a consensus infrastructure for large tech companies.

Trust is the first hurdle of the Agent economy

While payment issues have been resolved, there remains a more fundamental question without an answer.

"Commerce can’t happen if people don’t trust each other."

Davide Crapis is the AI lead at the Ethereum Foundation and one of the co-drafters of ERC-8004. His judgment directly points to the core obstacle of the Agent economy: when an AI Agent needs to hire another Agent to complete a task, how does it know that the other is not a fraud? Where is the transaction record? How is reputation transmitted?

ERC-8004 is Ethereum's answer to this question. Drafted in August 2025, it was officially launched on the Ethereum mainnet on January 29, 2026. It establishes three lightweight registries on-chain:

• Identity Registry: Each Agent receives an on-chain ID based on ERC-721 NFT, which is portable, transferable, cross-chain verifiable; AgentCard (in JSON format) records abilities, endpoints, and x402 payment support status;
• Reputation Registry: Feedback signals among Agents are archived on-chain—accuracy, timeliness, reliability ratings; only indexes are retained on-chain, with data hashes pointing to off-chain storage to lower Gas costs;
• Validation Registry: After task completion, the result data hash requests verification on-chain, allowing for cryptographic proof of "whether the task was completed."

The drafting team spans four major crypto ecosystems: Marco De Rossi from MetaMask, Davide Crapis from the Ethereum Foundation, Jordan Ellis from Google, and Erik Reppel from Coinbase. EigenLayer, ENS, The Graph, and Taiko have all expressed support. Less than a month after going live on the mainnet, the Ethereum mainnet registered over 24,000 Agents, with a total of about 49,000 across all EVM chains.

A typical workflow looks like this: Agent A finds a service provider through the ERC-8004 identity registry, filters the reputation registry to select a high-scoring Agent B, completes payment with x402, and after the task ends, attaches payment records with reputation feedback—creating a credit anchor point from the payment history. This link constitutes what Cambrian Network refers to as the "Agent economy operating system": Payment + Identity + Reputation, the three layers merge.

How deep is the water here?

The data looks attractive, but there are several things that need to be clarified.

Tokens and protocols are two different things.

The x402 ecosystem token once exceeded a market cap of 9 billion dollars on CoinGecko, with a daily trading volume exceeding 230 million dollars. However, a large number of "x402 concept tokens" are meme tokens that have no substantial binding to the protocol itself. Buying x402-related tokens does not equate to buying the growth of the x402 protocol. This market has always excelled at blending narrative and reality, and this time is no exception.

Technical risks have not yet been resolved.

The EIP-712 signature mechanism of x402 requires continuous security audits. The ERC-8004 reputation registry faces threats from Sybil attacks—bulk registration of false identities, and the existing economic incentive mechanisms are still inadequate. There is economic tension between high-frequency micropayments (0.0001 dollars per transaction) and L2 transaction fees (which can still be as high as 0.05 dollars); small-value transactions are still being eaten up by fees at this stage.

The protocol war is not over.

The coexistence of x402, Google's AP2, and a16z's ACP leads to three competing protocols. If developers split between these three standards, the network effect will be significantly reduced. Moreover, OpenAI and Anthropic could completely bypass on-chain protocols and construct their own closed-loop payment systems—they have users, data, and scale advantages, which pose competitive pressure that x402 cannot ignore.

Regulatory aspects are another blank space. Who is the party to a transaction initiated by an AI Agent autonomously? Where are the trigger points for KYC/AML responsibilities? No primary jurisdiction has provided definitive answers.

Summary

Someone wrote a sentence that is suitable to quote here: "The inscriptions of 2023 had humans carve value onto the chain; the x402 of 2025 allows machines to autonomously pay for value on the network for the first time."

If HTTP connected global computers into an information network, the combination of x402 and ERC-8004 aims to connect billions of Agents into an open service and data market—no accounts needed, no approvals required, just a request, a payment, a result.

However, whether the protocol can emerge victorious in fragmented competition, whether the trust mechanism can truly be perfected, and whether the Agent economy can transition from Demo to real commercial viability… these remain open questions.

Before narratives materialize, distinguishing "the value of the protocol" and "tokens speculated around the protocol" may be what each participant needs to clarify the most.

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