Welcome to b402

Gasless, confidential, multi-token agent payments across EVM chains

b402 is a multichain payment protocol for AI agents and web services. It extends the HTTP 402 standard and x402 protocol with gasless execution, compliant confidentiality, and multi-token support across EVM-compatible chains.

Architecture

Rather than depending on token-level signature standards like EIP-3009, b402 introduces its own execution layer — the Relayer contract — that works with any whitelisted token on any deployed chain. An agent signs an EIP-712 authorization off-chain (zero cost), the Facilitator settles on-chain, and the agent never needs native tokens for gas.

b402 is organized in three layers:

1. Protocol Layer — The b402 Relayer smart contract handles EIP-712 signature verification and on-chain token transfers. Deployed on BNB Chain and Base, with more chains to follow.
2. Service Layer — The Facilitator verifies payment payloads, settles transactions, deploys smart wallets, and executes swaps. b402scan provides agent reputation and seller discovery.
3. Developer Layer — Integrate via the Facilitator API, MCP tools, or agent frameworks (LangChain, CrewAI, Vercel AI SDK).

What Makes b402 Different

Compared to standard x402 implementations:

Feature	x402	b402
Tokens	USDC only	USDT, USDC, USD1, any whitelisted ERC-20
Privacy	None	Privacy pool integration (shield, transact, unshield)
Wallets	EOA only	EOA + Smart Wallets (ERC-7579 Nexus)
Gas	Gasless (USDC only, via EIP-3009)	Gasless (any whitelisted ERC-20, via Relayer)
Swaps	None	Integrated DEX swaps
Identity	None	ERC-8004 agent identity
Chains	Base (USDC, USDT)	Multichain — BNB Chain, Base, more planned

What Can You Build?

• Autonomous API trading bots that pay per query
• AI agents purchasing verified data feeds or inference time
• Usage-based paywalls for analytics, content, or compute
• Private payments where transaction details are shielded via the b402 privacy pool
• Cross-chain agent workflows that transact wherever liquidity exists

Get Started

Quickstart

Send your first payment in under 5 minutes

Architecture

Understand how the protocol works

Facilitator API

Full API reference for all endpoints

EIP-712 Signatures

Learn how to sign payment payloads

Links

GitHub

Discord