ZUGZWANG

zk-402 is a privacy-first micropayment layer built purely on Ethereum, enabling MCP AI agents to transact in an incognito mode using zero-knowledge proofs. Payments follow the x402 model while zk ensures that agent identity, balances, and transaction metadata remain hidden by default. ENS provides human-readable, reputation-anchored identities for agents without leaking on-chain behavior. Yellow enables programmable, compliant settlement rails for agent payments, while Arc supports secure, policy-aware capital flows between autonomous agents. Together, zk-402 turns Ethereum into a private, machine-native payment network where MCP agents can discover, pay, and coordinate trustlessly without exposing economic or behavioral signals. zk-402 with OpenClaw enables Ethereum-native, privacy-preserving micropayments where an orchestrating agent coordinates MCP services and settles x402 payments via zero-knowledge proofs.

zk-402 is implemented as an Ethereum-native extension to the x402 HTTP payment pattern, designed for MCP AI agents. MCP agents issue standard HTTP requests; when a 402 is returned, the payment intent is intercepted by a zk middleware layer. This layer constructs a zero-knowledge circuit that proves: (1) the agent controls a valid ENS-bound identity commitment, (2) the payment amount and recipient match the 402 quote, and (3) the agent satisfies policy constraints, without revealing balances or the sender address. ENS names resolve to identity roots, not wallets, and are verified inside the circuit. Yellow is used as the programmable settlement rail, executing payments only after zk proof verification. Arc enforces policy-aware limits and capital controls at settlement time. A key hack was decoupling ENS identity from payment execution using zk commitments, enabling private yet accountable MCP agent payments on Ethereum. OpenClaw is integrated as the execution and orchestration layer that sits above MCP agents and the zk-402 payment flow. An OpenClaw agent coordinates task execution, invokes multiple MCP agents for data or services, and manages retries, aggregation, and context passing. When an MCP agent returns an HTTP 402, OpenClaw routes the request through the zk-402 middleware, generates the required zero-knowledge payment proof, and resubmits the call without exposing agent identity or balances. OpenClaw also enforces policy context and execution limits before settlement. This design cleanly separates orchestration (OpenClaw), capability providers (MCP agents), and private payments (zk-402), enabling scalable, autonomous agent-to-agent interactions on Ethereum.