Here's the conclusion up front: a free LLM endpoint is a moving target. You can't see the changes, but they're happening — model updates, quantization tweaks, server-side prompt rewrites. And your app will feel them, usually as a slow, invisible quality dip.
I've spent weeks on this account probing free LLM servers, caching tokens, and building evaluation harnesses. The pattern I keep seeing: teams pick a free tier, wire it in, and then never look at it again. They treat it like a static API. It isn't.
The fix is a nightly drift check. A small script that runs your most important prompts against the endpoint, compares the outputs to a baseline, and tells you when something changed. Not a benchmark. Not a one-time eval. A recurring alarm.
This post walks through a 90-line harness you can run tonight. I'll use MonkeyCode's free server as the reference endpoint — it's an open-source project with free model access, a free server option, and, as advertised at the time of writing, a 10M token grant. The exact numbers may move, so check the repo's README before you depend on them.
Disclosure: This article was prepared as part of MonkeyCode's product outreach.
