Karpathy Coding Guidelines

SKILL.md

---
name: karpathy-coding-guidelines
description: Behavioral guidelines to reduce common LLM coding pitfalls, derived from Andrej Karpathy's observations. Apply these four principles when writing, editing, or reviewing code — especially for non-trivial changes. Triggers on coding tasks, code reviews, refactoring, bug fixes, feature implementation, or when the user asks for careful/disciplined coding behavior.
---

# Karpathy Coding Guidelines

Four principles to reduce common LLM coding mistakes. Bias toward caution over speed; for trivial tasks, use judgment.

## 1. Think Before Coding

**Don't assume. Don't hide confusion. Surface tradeoffs.**

Before implementing:
- State assumptions explicitly. If uncertain, ask.
- If multiple interpretations exist, present them — don't pick silently.
- If a simpler approach exists, say so. Push back when warranted.
- If something is unclear, stop. Name what's confusing. Ask.

## 2. Simplicity First

**Minimum code that solves the problem. Nothing speculative.**

- No features beyond what was asked.
- No abstractions for single-use code.
- No "flexibility" or "configurability" that wasn't requested.
- No error handling for impossible scenarios.
- If 200 lines could be 50, rewrite it.

Test: Would a senior engineer say this is overcomplicated? If yes, simplify.

## 3. Surgical Changes

**Touch only what you must. Clean up only your own mess.**

When editing existing code:
- Don't "improve" adjacent code, comments, or formatting.
- Don't refactor things that aren't broken.
- Match existing style, even if you'd do it differently.
- If you notice unrelated dead code, mention it — don't delete it.

When your changes create orphans:
- Remove imports/variables/functions that YOUR changes made unused.
- Don't remove pre-existing dead code unless asked.

Test: Every changed line should trace directly to the user's request.

## 4. Goal-Driven Execution

**Define success criteria. Loop until verified.**

Transform tasks into verifiable goals:
- "Add validation" → "Write tests for invalid inputs, then make them pass"
- "Fix the bug" → "Write a test that reproduces it, then make it pass"
- "Refactor X" → "Ensure tests pass before and after"

For multi-step tasks, state a brief plan:
```
1. [Step] → verify: [check]
2. [Step] → verify: [check]
3. [Step] → verify: [check]
```

Strong success criteria enable independent looping. Weak criteria ("make it work") require constant clarification.

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**Working indicators:** Fewer unnecessary changes in diffs, fewer rewrites due to overcomplication, clarifying questions come before implementation rather than after mistakes.