What Is the x402 Protocol

x402 is an HTTP-native payment protocol that uses USDC stablecoins for signupless, programmatic access to APIs and services. It implements HTTP status code 402 (Payment Required) with on-chain USDC payments on Base and Solana. osModa uses x402 to allow server spawning without signup or credit cards.

How x402 Works

The x402 protocol follows a challenge-response pattern built on standard HTTP. A client makes a request to a protected endpoint. The server responds with HTTP 402 (Payment Required) and includes payment instructions in the response headers: the amount of USDC required, the recipient address, and the supported blockchain networks.

The client completes the USDC payment on-chain (either on Base or Solana), receives a transaction hash as proof, and resubmits the original request with the transaction hash included in the request headers. The server verifies the on-chain payment and fulfills the request. No account was created. No personal information was exchanged. The payment is the authentication.

Why USDC Instead of ETH or SOL

USDC is a stablecoin pegged 1:1 to the US dollar. Using USDC eliminates price volatility: when osModa's Solo plan costs $14.99/month, that is 14.99 USDC regardless of what ETH or SOL are trading at. This makes pricing predictable for both the service provider and the customer.

osModa supports USDC on two networks: Base, an Ethereum Layer 2 with low gas fees and Ethereum ecosystem compatibility, and Solana, which offers sub-second finality and extremely low transaction costs. Users choose whichever network they prefer or already have funds on.

x402 on osModa: Signupless Server Spawning

osModa uses x402 to offer a zero-friction path to infrastructure. A user visits spawn.os.moda, selects a plan (Solo $14.99, Pro $34.99, Team $62.99, or Scale $125.99), chooses a region (Frankfurt, Helsinki, Virginia, or Oregon), and pays with USDC. No email, no password, no credit card form. The server is provisioned after on-chain payment confirmation.

This is particularly relevant for AI agents that need to provision their own infrastructure. An agent running on osModa can use osmoda-keyd (the wallet daemon with ETH + SOL support and policy-gated signing) to programmatically pay for additional servers via x402. The agent decides it needs more compute, sends USDC, and gets a new server -- all without human intervention.

osmoda-keyd: Agent Wallet Management

osmoda-keyd is one of osModa's 9 Rust daemons, responsible for managing ETH and SOL wallets with policy-gated signing. It enables AI agents to hold and spend USDC programmatically while maintaining security through configurable policies.

• Policy-gated signing -- Define rules for what transactions an agent can sign: maximum amounts, allowed recipients, required approval chains, and time-based limits.
• Dual-chain support -- ETH wallets for Base transactions and SOL wallets for Solana transactions. Both can hold and spend USDC.
• Audit integration -- Every wallet operation (balance check, transaction signing, payment confirmation) is recorded in the SHA-256 hash-chained audit ledger.
• Trust tier enforcement -- Wallet access is governed by the platform's trust model (Tier 0 unrestricted, Tier 1 sandboxed, Tier 2 max isolation). Untrusted agents cannot access wallet functions.

The History of HTTP 402

HTTP status code 402 was included in the original HTTP/1.1 specification (RFC 2616, published in 1999) with the note "reserved for future use." The designers of HTTP anticipated that the web would eventually need a native payment mechanism, but no standard emerged for over two decades. The x402 protocol fills this gap using stablecoins and blockchain verification instead of the traditional payment card infrastructure that the original designers may have envisioned.

Frequently Asked Questions

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