/add-mistake

Quickly add a mistake or anti-pattern to CLAUDE.md so Claude doesn't repeat it.

This implements Boris's "compounding engineering" pattern: every time Claude does something wrong, document it so it doesn't happen again.

Usage

/add-mistake "Claude used deprecated useState syntax instead of useReducer for complex state"
/add-mistake "Added moment.js when date-fns was already installed"
/add-mistake "Didn't run tests before committing"

Process

When the user provides a mistake description:

1. Read CLAUDE.md to find the Anti-Patterns table
2. Ask clarifying questions (via AskUserQuestionTool):
   • What should Claude do instead?
   • Is this a one-time mistake or a pattern to always avoid?
3. Add to the table with today's date
4. Confirm the addition

Example Addition

If the user says: /add-mistake "Used any type instead of proper typing"

Add to the Anti-Patterns table in CLAUDE.md:

| 2026-01-08 | Used `any` type instead of proper TypeScript typing | Always define explicit types; use `unknown` if truly unknown |

If No CLAUDE.md Exists

No CLAUDE.md found in this project.

Run /new-project first to create the project structure,
or create CLAUDE.md manually.

Compounding Engineering

This is how teams build institutional knowledge:

• Each mistake becomes a documented lesson
• Claude reads CLAUDE.md every session
• Over time, Claude makes fewer project-specific mistakes
• New team members (and Claude) benefit from accumulated wisdom

Commit CLAUDE.md changes so the whole team benefits!