> and even every day as the vendor tweaks the system prompts

I just patched Claude Code's system prompts, pinned the version and stopped upgrading without first dissecting and auditing the executable. Even discovered Anthropic can remotely inject strings into the system prompt via some "growth book" or something. Neutralized that too.

Things got a lot better after I started doing this. It straight up fixed Opus 4.6, and Opus 4.8 got more consistent in my subjective experience.

Sadly there's nothing I can do about Anthropic's server side "system reminders" whenever some prompt trips their classifiers or whatever.

I'm in the process of switching to OpenAI and Codex. The open source harness is a breath of fresh air. We'll see how that goes.