Introduction: Many users of Claude Code face not an issue of model capability, but rather the recurring need to start from scratch every time.

You repeatedly have to explain project context, tech stack, coding standards, what must remain untouched, and which solutions have already been tested. As long as this information isn't fixed, Claude will operate on guesswork—potentially modifying files that shouldn’t be changed, refactoring code without request, or even recommending tools unsuitable for your current project.

The CLAUDE.md file described in this article serves as a formal operating manual for Claude Code. Simply place it in your project’s root directory, and Claude will automatically read it at each session start. It pre-informs Claude about how to respond, how to write code, when to ask before acting, which operations must never be performed autonomously, what tech stack is used, and what critical decisions have already been made.

In short, CLAUDE.md’s purpose is: reduce redundant explanations, prevent model overreach, and make AI-driven development more stable and controllable.

If you're using Claude Code, begin with Karpathy’s four foundational rules: ask first if unclear, start with the simplest solution, avoid touching unrelated code, and explicitly state uncertainty. Add these four lines to your CLAUDE.md first, then gradually expand based on your project needs—your experience will improve dramatically.

Below is the original text:

A file named CLAUDE.md has topped GitHub Trending.

82,000 stars, 7,800 forks.

This began with Andrej Karpathy, former AI lead at Tesla and one of OpenAI’s founding members. He identified four behaviors that cause Claude Code to fail and documented them in a single file.

Later, a developer expanded upon these four rules and publicly released the file. It quickly went viral.

The reason is straightforward: code accuracy jumped from 65% to 94%.

Yet most daily users of Claude Code have never set this up. Each session starts from zero: re-explaining the same context, cleaning up unnecessary scope changes, rolling back refactorings no one requested.

Here is the complete file.

Every time you open Claude Code, it defaults to knowing nothing.

It doesn’t know your tech stack, your coding standards, your project background, what you’ve already tried, or what you explicitly decided not to do three sessions ago.

So it guesses. And once it starts guessing, it may refactor code you didn’t ask to touch, recommend frameworks that break your existing architecture, delete files without confirmation, or overturn decisions you’ve already made.

CLAUDE.md is a plain-text file placed in your project’s root directory. Claude Code automatically reads it at the start of every session.

One-time setup, no repeated explanations, and fixes three high-cost errors.

On average, developers spend about 30 minutes per day re-explaining context to Claude.

Tech stack, coding standards, project context, prior attempts—unless you document these once and let Claude auto-read them, they won’t persist across sessions.

At a developer hourly rate of $150:

· 30 minutes daily = $75;

· $375 weekly;

· $1,875 weekly for a 5-person team—the hidden cost.

The following seven rules should be placed at the beginning of CLAUDE.md.

→ Eliminate filler

Do not begin responses with phrases like “Great question,” “Of course,” “No problem,” or similar pleasantries. Deliver answers directly. No small talk, no repetition of the question.

→ Match response length to task complexity

Response length must align with task complexity. Simple questions get concise answers; complex tasks receive full, detailed explanations. Do not pad content with restating the question or repeating conclusions.

→ Propose options before acting

Before starting any significant task, present 2–3 viable paths for me to choose from before proceeding.

→ Acknowledge uncertainty before causing loss

If you’re uncertain about any fact, data, date, or technical detail, state it clearly before citing. Do not fill knowledge gaps with plausible-sounding but unverified information. When unsure, say “I’m uncertain” directly.

→ Who I am, what I know

About me: [Name] / Role: [Your role] / Background: [Domain].

I excel at: [Topics you’re familiar with].

I’m still learning: [Knowledge gaps].

Adjust answer depth accordingly. Don’t over-explain what I already know; don’t skip essential context I need.

→ Current project context

I’m working on: [Project name] / Goal: [Specific outcome] / Audience: [Who will use it] / Tech stack constraints: [Relevant limitations] / Must avoid: [List].

Apply this context to every task. If a requirement conflicts with context, flag it before execution.

→ Lock your expression style

My writing style is: [Describe your style].

Sentence length: [Preference].

Commonly used words: [Examples].

Words I never use: [Examples].

Format: [Prose or structured].

When writing on my behalf, strictly adhere to this style—never default to your own expression patterns.

Time spent daily re-explaining context: 30 minutes

At $150/hour: $75/day

Weekly: $375 per developer

5-person team: $1,875 weekly

Setup time for CLAUDE.md: Total 45 minutes

Errors to avoid: Never start from scratch writing CLAUDE.md. First use the prompt below, then edit the output:

Based on what I’ve shared about myself, my project, and how I want to work, generate a complete CLAUDE.md file. Include: who I am, my technical background, communication preferences, and default behaviors to follow in every session. Be specific, plain text, under 500 words.

You ask Claude to fix a function.

It refactors three files, renames variables, reorganizes imports, and rewrites comments you spent time crafting.

All without your confirmation.

Reviewing and rolling back these unnecessary changes could take 1 hour—$150. Three times weekly = $450. For a 5-person team, $2,250 weekly spent cleaning up unauthorized changes.

The following seven rules should be placed in the behavior constraints section of CLAUDE.md.

→ Strict scope control

Only modify files, functions, and code lines directly related to the current task. Do not refactor, rename, restructure, reformat, or “optimize” anything I haven’t explicitly asked you to change.

If you identify other areas worth fixing, note them at the end—but do not alter them. Never.

→ Ask before major changes

Before making significant modifications to content I’ve already created—including rewriting sections, deleting paragraphs, restructuring, or changing tone—pause, clearly explain what you plan to change and why. Wait for my confirmation before continuing.

→ Confirm before destructive actions

Before deleting any file, overwriting existing code, removing database records, or uninstalling dependencies, pause, list exactly what will be affected, and require my explicit confirmation. Only proceed if I say “yes” in the current message.

“You mentioned earlier” does not constitute confirmation.

→ Mandatory pause for production operations

The following actions require explicit confirmation within the current session—no exceptions:

· Deployment or push to any environment;

· Running migrations or database schema changes;

· Sending any external API calls;

· Executing any command with irreversible side effects.

· I must explicitly say “yes” in the current message.

→ Always show what changed

After completing any coding task, end with:

Modified files: list all touched files;

Changes: one sentence per file;

Files intentionally unchanged;

Next steps required.

→ No action without explicit confirmation

Without my explicit confirmation in the current message, do not send, publish, share, or schedule any content on my behalf—email, calendar invites, document sharing, or any action outside the current conversation. I must say “yes” explicitly in the current message.

→ Think before writing code

For tasks involving architectural decisions, complex debugging, or non-trivial feature development, first break down the problem step by step before writing code. Show your reasoning, highlight uncertainties, then execute.

Weekly cost of rolling back unauthorized scope changes: $150

Weekly manual diff checks: $75

Per developer wasted effort: $225/week

5-person team: $1,125/week

Setup time for CLAUDE.md behavior section: 30 minutes

Claude forgets everything between sessions.

Every decision you’ve made, every failed attempt, why you chose Prisma over Drizzle six months ago, why a constraint comes from a specific client demand—it all vanishes.

Then it proposes again solutions you’ve already rejected.

This section provides Claude with the closest thing to “persistent memory,” locks your tech stack, and prevents it from recommending tools that would break your existing architecture.

→ MEMORY.md Decision Log

Maintain a file named MEMORY.md in your project. After each important decision, add a new entry:

· What was decided;

· Why it was decided;

· What was excluded, and why.

Read MEMORY.md at the start of every session. Do not conflict with recorded decisions without reminder.

→ Session end summary

When I say “session end,” “wrapping up,” or “let’s stop here,” write a session summary into MEMORY.md including:

· What was addressed;

· What was completed;

· What remains in progress;

· Decisions made;

· Priority items for next session.

→ ERRORS.md Failure Log

Maintain a file named ERRORS.md. When a solution fails after two attempts, record:

· What didn’t work;

· What finally worked;

· What to watch for next time.

Check ERRORS.md before proposing similar solutions.

→ Permanent facts list

The following facts always apply to this project and must be enforced in every session without exception:

[Your permanent constraints, architectural decisions, and rules]

If a task conflicts with these facts, point it out before execution.

→ Lock tech stack

The project’s tech stack is as follows—always use these tools. Do not suggest alternatives unless I explicitly request it:

Language: [e.g., TypeScript]

Framework: [e.g., Next.js 14]

Package manager: [e.g., pnpm]

Database: [e.g., PostgreSQL with Prisma]

Testing: [e.g., Vitest]

Styling: [e.g., Tailwind CSS]

If a tool seems inappropriate, you may raise it. But unless I explicitly state otherwise, use only the defined tech stack.

→ Enable extended thinking for hard decisions

For issues involving system architecture, performance trade-offs, database design, or long-term technical decisions, use extended thinking mode.

Analyze step-by-step, propose trade-offs you may not have considered, identify assumptions that may fail at scale, then provide recommendations.

→ The 4 viral rules

Karpathy distilled four behaviors that cause Claude Code to fail. A developer condensed them into the following four lines. Code accuracy rose from 65% to 94%.

Ask first, don’t assume. If anything is unclear, ask before writing the first line of code. Never silently assume intent, architecture, or requirements.

Start with the simplest solution. Always implement the simplest working solution first. Do not add abstraction layers or flexibility not explicitly requested.

Don’t touch unrelated code. If a file or function isn’t directly related to the current task, don’t modify it—even if you think it could be optimized.

Explicitly mark uncertainty. If you’re unsure about a solution or technical detail, state it before proceeding. Acting confidently without certainty causes more damage than admitting ignorance.

· Weekly recovery cost from forgotten decisions and bad suggestions: $300 per developer

· Wrong tech stack recommendations and incompatible tools: $75/week

· Per developer waste from memory issues: $375/week

· 5-person team: $1,875/week

· Setup time for MEMORY.md + ERRORS.md + tech stack: 20 minutes

Full cost breakdown:

· Weekly re-explaining context: $375

· Weekly rolling back unauthorized changes: $225

· Weekly dealing with forgotten decisions: $375

· Total per developer weekly waste: $975.

For a 5-person team: $4,875 weekly. $253,500 annually.

While setting up CLAUDE.md takes only 2 hours total.

Just Karpathy’s four rules improved code accuracy from 65% to 94%.

A plain-text file. 21 rules. Two hours of work.

Developers who complete this setup are effectively using a more reliable Claude: one that remembers decisions, controls task scope, requests confirmation before destructive actions, and won’t recommend frameworks that break your existing architecture.

Those who haven’t set it up are still spending $975 weekly repeating themselves.

Footnote: Start with Karpathy’s four rules. Just these four. Paste them now into a new file named CLAUDE.md in your project root—takes 2 minutes. Then incrementally add gaps you discover each week.

Bookmark it before it gets buried in the feed. If you find it useful, share it with someone who truly needs it.

Original: Ludong BlockBeats