This is Part 2 of our LLM Selection series. In Part 1, we covered why choosing LLMs based on benchmarks is professional malpractice. Now we’re diving deep into the six specific failure patterns I’ve seen destroy production systems — and more importantly, how to test for them before they destroy yours.
Our customer support chatbot told a user that our premium feature was “definitely included” in the free tier. It wasn’t. The user upgraded based on that promise, then demanded a refund when they discovered the hallucination. That single confident fabrication cost us $2,400 in refunds and a scathing review that’s still our top Google result.