Token Budget Enforcement
Limiting token consumption per user, tenant, feature or time window at a central point, so cost cannot run away unobserved.
LLM cost scales with usage in a way that has no natural ceiling. A single misbehaving loop, an unconstrained agent, or one enthusiastic customer can generate a very large bill in hours — and unlike compute overspend, there is no capacity limit that stops it.
Enforcement belongs at a gateway, because it must apply across every application and cannot be left to each one.
What a budget policy specifies: the scope (user, tenant, feature, API key), the window (hourly, daily, monthly), the limit in tokens or currency, and the action on breach — reject, degrade to a cheaper model, or queue.
The controls that pair with it: per-request maximum output tokens, which bounds the worst case; maximum context size, which bounds input cost; maximum agent iterations, since an agent loop is the most common runaway; and alerting on burn rate, so a problem is caught in hours rather than on the invoice.
The gateway earns its place through what it centralises alongside this: provider abstraction and failover, credential management, prompt injection screening, output validation, caching, and consistent telemetry. Doing any of these per application produces six inconsistent implementations.