Credits
A run spends credits for the time it uses. The estimate before a run is not a price and not a cap, and a run settles on what it actually used.
Estimate first
Ask for an estimate before you start. A preview runs the selection and the admission checks and then stops: it creates no run, holds no phone and reserves no credits. In the web app the estimate appears before you confirm. For a coding agent, start_run accepts preview: true, and the verify skill states the estimate before it starts more than one scenario.
Cap a run
Pass --max-credits to talotrace run, or max_credits to start_run. TaloTrace refuses the run when its estimate is above the cap.
When billing refuses a run
ADMISSION_REFUSED means billing does not allow the run. The answer lists what is missing. Check the Billing page of your organisation. See Problems.