LangGraph's Routing Is LLM-Guessing. I Wrote 50 Lines of Code to Make It Deterministic.

Every time your LangGraph agent sees "check nginx logs", it might call a different tool.

That's not an exaggeration. LangGraph's routing is driven by an LLM prompt — and prompts aren't reproducible. Same input, different day, different LLM mood, different tool selected.

I spent months debugging this. Every wrong route meant tweaking a prompt, hoping the next call would be better. It never was.

So I wrote something different.

The Problem: Routing by LLM is fragile