CLAUDE.md and Rules Creator

You are about to write or edit a CLAUDE.md, CLAUDE.local.md, or .claude/rules/*.md file. At runtime these three shapes are the SAME content type: Claude Code's memory loader discovers them, concatenates them with a fixed MEMORY_INSTRUCTION_PROMPT prefix, and the API layer prepends the result as a single <system-reminder> user message before the conversation starts. The model treats them all the same; the file shape just controls when each loads and how a human maintains it.

This skill is the playbook for picking the right shape, choosing the right scope, writing content that actually changes behavior, splitting bloated files, using @path imports, and debugging "Claude is not following my CLAUDE.md". Target is Opus 5. Same rules work for Sonnet 5 at lower cost and for Haiku 4.5, which supports no effort parameter.

Three jobs, not one

Writing a CLAUDE.md or rule splits into three tasks. Conflating them is the most common authoring mistake.

1. Surrounding skill shape. None. CLAUDE.md and .claude/rules/*.md are not skills, not commands, not agents. They are plain markdown files the memory loader picks up. No frontmatter fields apply except paths: (only on .claude/rules/*.md). Route through ac:skill-creator ONLY if you are wrapping CLAUDE.md authoring inside a custom slash command or skill.
2. CLAUDE.md / rule shape. Where the file lives (managed / user-global / project-team / project-personal), what file name (CLAUDE.md / CLAUDE.local.md / .claude/rules/<topic>.md), paths: frontmatter for rules, @path imports, HTML comments. This file teaches that.
3. Body content. The markdown text the model reads. This is a standing instruction set, a prompt at runtime. Route through ac:prompt-writer for prompt architecture, snippets, and Opus 5 tuning.

A great body in the wrong file shape (oversized, wrong scope, missing paths:, leaks personal preferences into a team file) never produces consistent behavior. A modest body in the right shape, sized below the adherence cliff, changes behavior every session.

What CLAUDE.md actually is, mechanically

The lifecycle: