I was running a multi-agent setup over a weekend. Three workers in parallel, each calling Claude, each with their own retry logic. I woke up on Sunday to a bill alert.
Forty bucks. Eighteen minutes. One worker had gotten into a retry loop on a malformed tool response and had hammered the API until I happened to glance at my dashboard.
The annoying part: I had per-call cost logging. Every call printed its USD cost. I just had no shared cap across the three workers. Each one thought it was being polite by capping at $5. Three workers, three caps. The actual ceiling was $15+ per minute and nothing stopped them.
So I built token-budget-pool. One shared atomic counter that all workers check before every call.
The API
