How to Add Budget Control to a LangChain Agent

How to Add Budget Control to a LangChain Agent LangChain makes it easy to build agents that call LLMs, search the web, execute code, and chain tool calls together. What it doesn't give you is any way to cap how much a single agent run is allowed to spend. That's fine when you're experimenting. It's a real problem when you're running agents in production — especially across multiple users or tenants. A single misbehaving agent loop can burn through hundreds of dollars before anyone notices. This guide shows how to add per-run budget control to a LangChain agent using Cycles — without rewriting your agent logic. tip Already using the callback handler? If you want per-LLM-call budget tracking (a reservation around every model invocation), see Integrating Cycles with LangChain. This guide covers a different pattern: a single reservation around the entire agent run, plus optional tool-level checks. ::: The problem Here's a typical LangChain agent loop: from langchain.agents import AgentExec