An AI agent calls a paid API, the payment goes through, and the response never arrives. The connection dropped, a proxy timed out, or the agent's own runtime restarted. From the agent's side the call failed, so it does the reasonable thing and tries again. If the API charges per call, that retry is where money goes missing. The first payment may have settled on chain while the agent never saw the result. A naive retry pays a second time for the same work. We run an MCP gateway where agents...