karpathy-coding-guidelines

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.

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