Why Claude Code Ignores Your CLAUDE.md (And How to Fix It)

If you've ever noticed Claude Code ignoring rules you carefully wrote in your CLAUDE.md, you're not imagining it. I spent hours adding instructions to my config file, only to watch Claude keep doing the exact things I told it not to. After digging into how Claude Code actually processes CLAUDE.md, I found four specific reasons this happens. 1. Your file is too long Claude Code starts selectively ignoring content after around 80 lines. This isn't a bug — it's a fundamental limitation of how LLMs process instructions. Frontier models can reliably follow approximately 150 instructions. Once you exceed that, the model starts making judgment calls about what to pay attention to. Most CLAUDE.md files I've seen are 100-200+ lines. Mine was 140 lines. I had no idea this was a problem. Fix: Keep your CLAUDE.md under 80 lines. Every line should answer the question: "Would removing this cause Claude to make mistakes?" If not, cut it. 2. You have contradicting instructions This one is subtle. If y