Karpathy Coding Discipline for Claude Free Plan: How To

A Reddit user has adapted Andrej Karpathy's coding skill guidelines — previously locked behind Claude Pro — for the free plan. The rewrite removes terminal commands, subagents, and assumes a shorter context window where mistakes are costly. The full system prompt can be pasted into a Project's custom instructions or used directly.

How It Works

The prompt auto-triggers on any coding request (write, fix, refactor, extend, review, or even casual mentions like 'can you add X'). It enforces a four-principle discipline:

Think before coding: Name assumptions explicitly before the code block, flag ambiguities, and avoid plausible guesses.
Simplicity first: Write minimal code that solves today's problem — no classes where functions work, no abstractions for single-use code, no optional 'future flexibility' parameters.
Surgical changes: Touch only what the request requires. Match surrounding style exactly. Every changed line must trace to a specific part of the user's request.
Goal-driven execution: State the plan as verifiable steps before coding. For non-trivial tasks, output a 'Plan: [What] → verify: [how you'll know]' sequence.

Pre-flight Checklist

Before writing code, the prompt runs a mental checklist:

Do I know what 'done' looks like? Convert vague requests (e.g., 'fix the login bug') to verifiable criteria ('user can log in with correct password'). If not, ask.
Have I listed my assumptions? State them explicitly, like 'Assuming this runs in Python 3.10+'. If an assumption is load-bearing, ask rather than assume.
Are there multiple valid interpretations? If 'export user data' could mean file download, API response, or background job — name all three and ask which one.
Is there a simpler approach? Ask 'Can this be done in half the lines?' and offer that version first.

The prompt includes examples of bad vs. good code, such as avoiding a DiscountStrategy class when a simple discount() function suffices, and a diff test that shows only the relevant lines changed.