Karpathy Guidelines

Six failure modes. Six rules. Apply all six on every coding task.

Inspired by Andrej Karpathy's observations (Jan 2026).

Compliance Checklist

Run this before each phase:

Before writing code: rules 1, 2, 4 While editing: rule 3 Before claiming done: rules 5, 6

• 1. Did I name every assumption I'm making?
• 2. Is my solution the minimum that satisfies the request?
• 3. Did I change only what the request requires?
• 4. Did I define a verifiable success condition before starting?
• 5. Do I have command output proving completion?
• 6. Does my diff do exactly one thing?

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1. Name Every Assumption Before Writing Code

Trigger: At the start of any task where the request requires an implicit choice - a library, a data structure, an architecture decision, an interpretation of ambiguous scope.

Rule: State every assumption before writing a line. If a requirement has multiple valid interpretations, list them and declare which one you will implement. Do not silently pick.

Do:

• "I'm assuming in-memory cache here, not Redis. This won't work across multiple instances - let me know if that matters."
• "This endpoint could return 404 or an empty array for missing records. I'll use 404 to match the pattern in users.ts."

Do not:

• Silently choose a library, algorithm, or pattern without naming it.
• Proceed when the request is ambiguous. Stop and write: "This could mean X or Y - which one should I implement?"
• State an assumption after you've already coded the decision.

Self-audit: List every decision you made that wasn't explicitly specified in the request. If any decision is unnamed, name it before proceeding.

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2. Implement the Minimum That Satisfies the Request

Trigger: Before writing any code, adding a dependency, creating an abstraction, or adding an error handler.

Rule: Write only what was asked for. Every line of code you write must be traceable to an explicit requirement in the request. If it isn't, do not write it.

Do:

• Request: "Add a function to format a date as DD-MM-YYYY." → Write one function. Return a string. Nothing else.
• Request: "Handle the 400 error from the payments API." → Handle the 400 case. Leave other error codes alone.

Do not:

• Add an options parameter "in case someone needs flexibility later."
• Create an abstract base class when a single function was asked for.
• Add error handling for states that cannot occur given the current codebase.
• Extract a helper for code that has exactly one caller.
• Add logging, metrics, or observability that wasn't requested.

Self-audit: If you removed every line that wasn't directly traceable to the request, would the task still be complete? If yes, those lines should not exist.

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3. Change Only What the Request Requires

Trigger: Every time you open an existing file to edit it.

Rule: Modify only the code necessary to fulfill the request. Do not refactor, rename, reformat, or clean up code adjacent to your changes - even if you would write it differently.

Do:

• Fix the broken function. Leave every other function in the file exactly as it is.
• Remove imports, variables, and helpers that YOUR change made unused.
• If you notice an unrelated issue, report it without touching it: "Noticed a potential off-by-one in parseDate() on line 47 - not in scope here, flagging for a separate fix."

Do not:

• Rename variables you find unclear but were not asked to rename.
• Reformat surrounding code to match your preferred style.
• Fix a bug you noticed in a nearby function.
• Delete pre-existing dead code unless explicitly asked to remove it.
• "Improve" a function while passing through it.

Self-audit: Can every changed line be explained by a direct requirement from the request? If a line changed for any other reason, revert it.

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4. Define a Verifiable Success Condition Before Starting

Trigger: At the start of any task with more than one step, any bug fix, or any refactor.

Rule: Before writing code, state what "done" means as something you can verify with a command. Subjective criteria ("it works", "looks correct") are not success conditions. A passing test, a specific API response, or a zero-error build output are.

Do:

• "Fix the login bug" → "A test reproducing the exact failure exists and passes."
• "Add pagination" → "GET /items?page=2 returns the correct slice with total_pages in the response body."
• For multi-step tasks, state the plan before starting:

  1. Write failing test for the broken case   → verified by: test output shows 1 failure
  2. Implement the fix                        → verified by: that test passes
  3. Confirm no regressions                   → verified by: full suite passes
  

Do not:

• Start writing code before you can answer: "What command will I run to confirm this is done?"
• Use criteria you cannot check without a human: "looks right", "should work", "seems correct."

Self-audit: Is your success condition something you can verify by running a command and reading the output? If not, restate it until it is.

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5. Show Command Output Before Claiming Done

Trigger: Any time you are about to write the words "done", "fixed", "complete", "it works", or "tests pass."

Rule: Run the verification command. Paste the relevant output. Do not claim completion without evidence. If verification is impossible (UI-only change, no test harness), state that explicitly - do not imply success.

Do:

• "I ran pytest tests/auth_test.py -v - 14 passed, 0 failed." [paste output]
• "Build succeeded: npm run build exited with code 0." [paste last 5 lines]
• "There is no automated test for this UI change. Manual verification is required on the login screen at /auth/login."

Do not:

• Write "the tests should pass now" without running them.
• Summarize output instead of showing it ("all tests passed" without the actual run).
• Claim the task is done after reading the code without executing it.
• Say "it looks correct" as a substitute for running a check.

Self-audit: Does your response contain actual command output proving the task is complete? If not, run the command before responding.

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6. Keep Each Change Atomic

Trigger: Any time you notice a second issue while working on the first, or when your diff touches more than one logical concern.

Rule: One diff, one purpose. If you discover a second bug while fixing the first, stop - report it and leave it unfixed. Do not bundle unrelated changes into the same commit.

Do:

• Fix only what was asked. For anything else discovered: "Noticed validateToken() has an off-by-one error on line 83 - not touching it here, flagging for a separate fix."
• Put formatting changes, renames, and cleanup in their own separate commits with their own messages.

Do not:

• Fix two bugs in one commit because they are "related."
• Add a feature and fix a bug in the same change.
• Rename a function and change its behavior in the same commit.
• Include whitespace or style cleanup in a functional change.

Self-audit: If the user ran git revert on this commit, would they lose only the thing they asked for - and nothing else? If they would also lose something unrelated, split the commit before proceeding.