Ceilings

A project needs a ceiling before any request is forwarded. You can set a daily limit, a monthly limit, or both. Each period resets at midnight in the timezone on that ceiling. Whichever period would be crossed first blocks the request.

Fuse reserves the worst case first: input tokens plus the output cap, times the price for that model, with a small margin. The reservation is replaced when the provider reports usage. A provider error before any tokens costs nothing.

{
  "error": "fuse_blown",
  "message": "The monthly ceiling for this project would be crossed by this request.",
  "spent_usd": 24.97,
  "limit_usd": 25,
  "in_flight_usd": 0.01,
  "request_estimate_usd": 0.04,
  "period": "monthly",
  "period_resets_at": "2026-11-01T00:00:00.000Z",
  "request_id": "req_…"
}

403 no_ceiling_configured means the project has no daily or monthly limit yet.