Hard caps on autonomous agent API spend

A developer has proposed a DIY client-wrapper approach to cap autonomous agent API spending, tracking cumulative token or dollar cost per session and refusing further calls once a hard session ceiling is reached. The method logs the stop reason for operator inspection, with provider key quotas and org spend limits serving as a backstop when the wrapper fails open.

Autonomous agents in long research loops can exhaust an API budget before anyone notices. Provider dashboards and account-level alerts help after the fact, but they often fire too late for a single runaway session. A practical DIY baseline is a thin client wrapper that: - tracks cumulative token or dollar cost per session - refuses the next call once a hard session ceiling is hit - logs the stop reason so the operator can inspect what burned the budget Provider key quotas and org spend limits still matter as a backstop when the wrapper fails open. When you run agents against paid model APIs, where do you enforce the hard stop: in the agent loop, at an API gateway, or only via the provider's billing controls?