Three ways your coding agent silently never reads your instructions

You write instructions for your coding agent. It ignores one of them. You rewrite it more forcefully, in bold, with "IMPORTANT" in front. It still ignores it. Before blaming the model, check whether it ever saw the text. Each of the three cases below is documented behaviour of a tool you already use, each one drops part of your instructions on the floor, and none of them prints a warning. 1. Cursor ignores .md files in .cursor/rules Project rules in Cursor must use the .mdc extension. Cursor's own docs put it plainly: a plain .md file there is ignored by the rules system, because it has nowhere to declare the description , globs and alwaysApply frontmatter that tells Cursor when to apply it. So a file sitting in exactly the right directory, with exactly the right content, does nothing. No error at startup, no "rule skipped" line, nothing in the UI. Ten-second check: find .cursor/rules -name '*.md' 2>/dev/null Any output is a rule that isn't loading. Rename to .mdc and add the frontmatter. A detail that makes this worse: people who set up .md rules a while ago report that they used to work. If that's right, a working setup stopped working at some point during an update, and nothing announced it — so "I checked this once" is not protection. 2. Codex truncates your AGENTS.md files — as a set, not one by one Codex reads the AGENTS.md files that apply to your working directory: a global one, the repo root, and the nested ones on the path. It concatenates them, and the 32 KB truncation applies to that combined payload . This is the part that catches people, because every individual file looks fine: AGENTS.md 12 KB ✓ fine packages/api/AGENTS.md 12 KB ✓ fine packages/web/AGENTS.md 12 KB ✓ fine ----- 36 KB ✗ 4 KB never reaches the model Nobody wrote a "too big" file. The rule you carefully put at the bottom of the last one simply isn't there when the model reads. Check it: find . -name AGENTS.md -not -path '*/node_modules/*' | xargs wc -c Add your global ~/.codex/AGENTS.md t