Simon Willison calls for hard budget caps by default on usage-based paid APIs

Simon Willison proposes that usage-based paid services and APIs should have hard budget caps by default, that is, after reaching $X per month, they should be cut off directly and return an error, rather than just sending a warning email. He believes that coding agents and AI agents will lower the barrier to creating paid services, and users may wake up to find that an out-of-control service has already consumed hundreds or even thousands of extra dollars, so the hard cap should be the default and opting out should require an active choice. AWS launched a monthly spending cap feature on September 16, pausing projects for the month once the limit is reached, but this new experience is currently only available to a limited set of customers; Google Cloud launched Spend Caps in July.