How to keep an agent's LLM bill flat

Six tactics for bounding what an autonomous agent can spend on inference: prepay the ceiling, one key per agent, daily caps, model allow-lists, budget in the loop, and a kill switch that is not a deploy.

1. Prepay the ceiling — the only limit that cannot be exceeded is money that was never there.
2. One key per agent — shared credentials mean shared blast radius.
3. Cap the rate, not just the total — a daily cap bounds the burn.
4. Pin the models a key may call — model choice is a 30x price lever.
5. Put the budget in the loop — a spend receipt on every completion lets the agent degrade or stop.
6. Keep a kill switch that is not a deploy.

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