The 3am bill: how a runaway agent loop quietly torches your LLM budget
Agents don't fail loudly. They loop, politely, expensively, and you find out on the invoice. A budget wall that's enforced before the spend, not discovered after it.
The scariest LLM bills don't come from traffic spikes. They come from a single agent that got stuck in a loop at 2am, asking the model the same near-identical question a few thousand times, each call a few cents, all night, until someone wakes up to a five-figure surprise. Nobody meant to spend it. There was just no wall to stop it.
The limit is enforced at the cache, before a single extra token is bought.
And here's the compounding part: most of those looped questions are near-duplicates, which means the semantic cache absorbs the bulk of them for free long before the budget wall is even in play. The cache flattens the cost; the wall caps the worst case. Together they turn a category of terrifying bills into a non-event.
The bottom line
You shouldn't learn your agent misbehaved from your credit card statement. Put the wall where the spend happens, at the cache, and sleep through the loop.