I catalogued every way local models break JSON output and built a repair library, here's what I found across 288 model calls

I've been running structured output prompts through a bunch of models on OpenRouter for the past few months — Llama 3, Mistral, Command R, DeepSeek, Qwen, and every other model on OpenRouter — alongside the usual closed-source suspects. 288 calls total. I wanted to know what actually breaks, how oft