13. Curing AI Amnesia (CLAUDE.md and Rules)

<p>In Episode 13 of <strong>Beyond Prompting</strong>, author Sho Shimoda breaks down how to configure persistent repository instructions using CLAUDE.md and rule files. Rather than treating CLAUDE.md as a generic style guide or dumping ground for historical bugs, this episode focuses on treating instruction files as a concise briefing for a capable colleague. We cover:</p><ul><ul><li><strong>The 200-Line Rule:</strong> Why CLAUDE.md should be kept concise (under ~200 lines) by focusing strictly on non-derivable facts, build environments, and explicit boundaries—leaving out generic advice and formatting rules the model can see for itself.</li></ul><ul><li><strong>Concatenative Inheritance:</strong> How instruction files concatenate rather than override across four scopes: managed enterprise policy, user-level ~/.claude/CLAUDE.md, project ./CLAUDE.md, and uncommitted ./CLAUDE.local.md.</li></ul><ul><li><strong>Scoped Rules (.claude/rules/):</strong> How to split large instruction sets into modular files inside .claude/rules/ using paths: frontmatter globs so that topic-specific rules (like frontend React conventions) only load when matching files are opened.</li></ul><ul><li><strong>Deterministic Tools vs. Reasoning Context:</strong> Why mechanical syntax and formatting rules belong in deterministic linters and git hooks, reserving CLAUDE.md for architectural context and edge-case rationale that static analysis cannot check.</li></ul><ul><li><strong>Preventing Instruction Sediment:</strong> Using CLI commands like /init, /memory, and /doctor to audit, prune, and maintain instruction files like code.</li></ul></ul><p><em>(Note for listeners: This episode covers Chapter 13 of Sho Shimoda&#39;s book </em><a href="https://www.amazon.com/dp/B0HJKBWKVQ" target="_blank" rel="noopener noreferer"><strong>RUNNING CLAUDE: The Operator’s Guide to Chat, Cowork and Claude Code</strong></a><em>, available on Amazon as the successor book to </em><strong>Master Claude: Chat, Cowork and Code</strong><em>).</em></p>