IME CLAUDE.md rarely gets fully honored. I've left HN comments before about how I had to convert some CLAUDE.md instructions to pre-commit deterministic checks due to how often they were ignored. My guesstimate is that it is about 70 % reliable. That's with Opus 4.5. I've since switched to GPT-5.2 and now GPT-5.3 Codex and use Codex CLI, Pi and OpenCode, not CC, so maybe things have changed with a new system prompt or with the introduction of Opus 4.6.