shop3

Inspiration: Google launched Universal Cart at I/O this week — AI agents that shop for you. But only on Google's rails. Only with Visa. Only with approved merchants.

We asked: What does this look like on the open web? Where any agent can pay any service, with no middleman.

What it does: Shop3 lets AI agents become truly autonomous — discovering and paying for digital services using on-chain micropayments. No accounts. No API keys. No humans.

The agent receives a task, hits a paywalled service, gets back a 402 Payment Required response, pays autonomously from its own Circle wallet via x402, and returns clean structured results. Every action is stored in ClickHouse as an audit trail, and every finding is published via Senso to cited.md so the agent contributes back to the open web.

How we built it: The agent brain runs on Anthropic's Claude. The wallet is a Circle Programmable Wallet built on ERC-4337 account abstraction. Payments happen via x402 with USDC on Arc Testnet. Web data comes from Nimble's API. Memory lives in ClickHouse. Publishing happens through Senso, with citable output on cited.md. Datadog APM gives us full observability into every step the agent takes.

Everything is wired together in Node.js, orchestrated by Claude.

Challenges we ran into: Circle wallets don't natively sign x402 payment headers, so we wrapped paid APIs in our own middleware to make it work. We hit a Nimble auth scheme bug mid-build and debugged Bearer vs Basic auth live. At one point the agent was paying itself — we fixed that by creating a separate merchant wallet. And of course, time — five hours, solo with one engineer, learning Circle's SDK from scratch.

What we learned: x402 plus smart wallets is the missing payment layer for agents. Subscriptions assume you know who's calling, what they need, and how much they'll use. Agents break all three. They discover, decide, and pay in real time.

The hard part isn't crypto. It's the glue, getting wallets, payment protocols, and APIs to speak the same language.

The future of agentic commerce isn't fiat versus crypto. It's per-call, permissionless, and on-chain.

What's next for Shop3: Native x402 support so we don't need middleware. Multi-wallet agent sessions with on-chain spending limits. Publishing every transaction receipt as a citable artifact on cited.md. And an SDK so any developer can give their agent a wallet in three lines of code.