Gate your CI on a dollar ceiling, not a percentage — the number your finance team actually asks for
Most cost gates for agent/LLM workflows check a delta: did this PR make the run more expensive than the last one, by more than X%? That's a good regression alarm. But it answers a developer's question ("did I make it worse?"), not a budget owner's question ("are we going to blow the monthly number?").
Those are genuinely different gates, and a team that only has the percentage one keeps getting surprised. A workflow can pass every percentage check — each PR adds a harmless-looking 3% — and still cross the line where the absolute monthly spend stops being okay. Percentages compound quietly; dollars are what shows up on the invoice.
So the second gate I want on any agent workflow is an absolute ceiling: "a single run of this job must not cost more than $N," full stop, regardless of whether it went up or down since yesterday.
Three things make that gate actually usable rather than theater:
