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xNUWA is Nuwa’s x402-native AI client that demonstrates how users and autonomous agents can browse, pay for, and run AI Agents with nothing more than an on-device wallet. The app lives at xnuwa.app and is open-sourced at nuwa-protocol/xnuwa.app.
Agents bundle a prompt, model (or remote API), optional MCP tools, and a UI surface. xNUWA renders these agents, handles payment auth, and records usage so builders can monetize instantly.
xNUWA is currently in alpha. For developers, xNUWA is the fastest way to feel the x402 flow from the client perspective—use it to test your own paid MCP, validate facilitator compatibility, and demo the experience to end users. .

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Key Features

  • Self-custodied identity: Users authenticate with an EVM address. Keys are stored client-side (IndexedDB) and decrypted only when signing with a PIN or passkey.
  • Seamless x402 checkout: Every paid MCP call or LLM request goes through x402 receipts. The client handles the X-PAYMENT negotiation flow automatically.
  • Offline-friendly data model: Zustand + Dexie keep chat history, wallet metadata, and agent configs available even without a persistent backend.
  • Registry integration: Ships with a community agent-registry/ for publishing reusable agents that comply with the Nuwa Agent registration schema.

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How payments work inside xNUWA

  1. The MCP or LLM endpoint replies with 402 Payment Required plus the x402 paymentRequirements payload.
  2. xNUWA selects a supported scheme/network (default: exact on base-sepolia) and builds the X-PAYMENT header, signing the transaction via the embedded wallet.
  3. The client resends the request with X-PAYMENT; the endpoint verifies/settles (often via Coinbase facilitator) and responds with X-PAYMENT-RESPONSE for observability.
  4. Receipts are persisted locally so users can audit spend and quickly replay flows without reconfiguration.
You can connect xNUWA to mainnet by switching the default network to base once your service wallet is funded with USDC.

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What Is ERC8004?

ERC8004 is an emerging on-chain registry standard for publishing and discovering off-chain AI services and agents. In practice, it maps an on-chain identity to verifiable service metadata (e.g., endpoints, content identifiers, and ownership), so wallets and clients like xNUWA can resolve and load agents in a permissionless way.
  • xNUWA reads ERC8004 records to discover and load agents alongside its local agent-registry/.
  • Builders can register their agents to an ERC8004 registry to make them globally discoverable.
  • See the Nuwa reference implementation: https://github.com/nuwa-protocol/nuwa-8004/tree/main

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Best practices for builders

  • Bundle demos: Include a demo agent and sample MCP configs so new users can verify payments quickly.
  • Respect privacy: Keep sensitive data in encrypted Zustand stores and avoid exporting private keys.
  • Document agents: Maintain markdown docs inside agent-registry/ and link back to your repos via the metadata block.
  • Monitor receipts: Surface X-PAYMENT-RESPONSE details in your agent UI so developers can debug facilitator or settlement issues fast.