5 Silent Failure Patterns I Keep Finding in Production AI Systems

I've spent roughly two years debugging production AI systems for engineering teams that have already shipped, with production traffic, real users, and real cost surfaces. Different stacks (LangChain, LlamaIndex, vanilla SDK calls, custom agent harnesses), different audiences (B2B SaaS, internal tools, consumer features), and different scales. But the failure modes are remarkably consistent. Here's what's surprised me: the failures that hurt the most aren't the obvious ones. Models hallucinate, s