Why MPC Threshold Signing May Be the Safest Way for AI Agents to Handle Payments

A surge of AI agent payment infrastructure funding — including $30M raised by Catena and $35M by Sapiom — has highlighted a critical architectural gap: existing payment systems were built for humans, not autonomous software. When AI agents need to pay for services like API calls or cloud compute in milliseconds, traditional methods such as manual approvals and multi-signature wallets are too slow to be practical. Giving agents direct custody of private keys is fast but dangerous, as a recent fake AI trading bot incident demonstrated how easily such systems can be exploited. Multi-Party Computation (MPC) offers a middle path by splitting a private key into shares held by separate parties, so no single point of compromise can drain a wallet. This approach enables sub-150ms transaction signing without the agent ever reconstructing the full private key, though enterprises must still layer on spending limits and allowlists to maintain adequate controls.