Control LLM Costs with LangSmith LLM Gateway

Learn how LangSmith LLM Gateway lets you set and enforce cost limits across multiple models and agents, avoiding surprise AI spend spikes.

Worried about skyrocketing AI bills?

⚡ TL;DR: LangSmith LLM Gateway lets you set and enforce cost limits across multiple models and agents, preventing surprise spikes.

The Simple Version

Think of the gateway as a toll booth for your LLM traffic.

It watches every request, checks your budget, and can block or throttle calls that would go over.

The gateway receives API calls and decides which model to use.

🎯 Think of it this way: It's like a traffic light that only lets cars (requests) go when the road (budget) has space.

You define a maximum spend per day or per model.

If usage approaches the limit, the gateway can pause further calls.

🎯 Think of it this way: Like a credit card that declines a purchase once you hit your limit.

LangSmith LLM Gateway sits between your app and the model endpoints.

It uses a cost calculator middleware that tracks token usage and monetary cost in real time.

The gateway can be configured with JSON rules that specify per‑model caps, burst allowances, and fallback actions.

When a request arrives, the middleware calculates the cost, updates a running total, and decides whether to forward, delay, or reject the call.

All actions are logged in LangSmith’s tracing UI, giving you visibility into where money is spent.

Uncontrolled LLM usage can bleed budgets faster than a coffee shop on a Monday.

By centralizing cost enforcement, teams avoid hidden overruns and can allocate funds more predictably.

This also encourages experimentation — developers can try new agents knowing they won’t break the bank.