My Codex Harness: Project Overrides and Environment Setup

I work on a shared project with many other developers in my organization. Its shared instructions added up to roughly 13,200 tokens, including workflows for Claude Code. My personal Codex harness uses about 670 tokens, a 95% reduction in instruction text, without changing everyone else’s setup. The shared guide could be trimmed too, but that’s for later. My personal harness has 2 parts: short instruction overrides and automatic worktree setup. Override the project instructions Codex loads AGENTS.override.md instead of AGENTS.md in the same directory. Global and parent-directory instructions still apply; an override doesn’t replace the whole chain. See the discovery rules. I use a root override for shared preferences and ios/AGENTS.override.md for platform essentials. They cover focused checks, existing architecture, precise money handling, simulator sessions, and generated files. The shared guides stay intact. I read them when a task needs more detail, rather than loading the whole…