If you use an agentic coding tool — Claude Code, or anything with a persistent instructions file — you've probably hit this. You start a CLAUDE.md (or .cursorrules, or AGENTS.md) with a few conventions. It's useful. So you add the architecture. Then the gotchas. Then the three things it keeps getting wrong.
Six months later it's 800 lines, and you are paying for all 800 of them on every single message, in every session, forever.
That's the part people miss. An instructions file isn't loaded once per session. It's part of the context for each turn. A file that doubles doesn't cost you twice once — it costs you twice per message, for the life of the project.
Why the two obvious fixes both fail
Delete most of it. Now the agent doesn't know your conventions and you're correcting it by hand again. You traded token cost for your own time, which is usually a worse trade.
