Introduction
If you use Claude Code as your AI development assistant, you've likely noticed its persistent habit: at the start of every session, it reminds you of the 'project essence.' This isn't just a quirky behavior — it's a powerful feature rooted in how Claude Code reads and interprets a special configuration file called CLAUDE.md. Recently, the official specification for this file was updated, and understanding its structure can dramatically improve how your AI advisor aligns with your project goals.
This article explains the purpose of CLAUDE.md, how to write it according to the official spec, and why it matters for your development workflow. Whether you're a solo developer or part of a large team, mastering this file will help you get more relevant, context-aware assistance from Claude Code.
What is CLAUDE.md?
CLAUDE.md is a Markdown file placed in the root of your project repository. It serves as a persistent instruction set for Claude Code, defining the project's purpose, coding conventions, architecture decisions, and behavioral guidelines. Unlike generic AI prompts, CLAUDE.md is designed to be read automatically at the start of each session, ensuring the AI advisor understands the 'essence' of your project before it answers any question.
The official specification, detailed in the Anthropic documentation and community discussions, outlines a structured format. The key insight is that CLAUDE.md acts as a living document — it should be updated as the project evolves.
Why Does Claude Code Keep Reminding About the 'Project Essence'?
According to a recent article on Habr (source: Source), developers using Claude Code report that the advisor frequently reiterates the project's core goals at the start of each interaction. This happens because the AI is trained to prioritize context from CLAUDE.md. If the file is missing, vague, or outdated, Claude Code will remind you to define the project essence — essentially nudging you to write better instructions.
The article's authors describe this as a feature, not a bug. It ensures that even after long breaks or context switches, the AI remains aligned with your original vision. However, it can become annoying if CLAUDE.md is poorly structured or contains conflicting information.
How to Write CLAUDE.md According to the Official Specification
The official spec recommends a clear, hierarchical structure. Here’s a practical guide based on community best practices and the latest documentation.
1. Project Overview
Start with a concise description of your project. Include:
- Purpose: What problem does this project solve?
- Target users: Who is this for?
- Key features: List 3-5 core functionalities.
Example:
# Project: E-Commerce Platform
- Purpose: Enable small businesses to sell products online with minimal setup.
- Users: Store owners, customers, administrators.
- Features: Product catalog, shopping cart, payment processing, order tracking.
2. Tech Stack and Dependencies
Specify the programming languages, frameworks, databases, and external services used. This helps Claude Code give accurate technical advice.
| Category | Technology |
|---|---|
| Frontend | React 18, Tailwind CSS |
| Backend | Node.js 20, Express |
| Database | PostgreSQL 15, Redis |
| External APIs | Stripe, SendGrid |
ASI Biont supports integration with Stripe via API — more details at asibiont.com/courses.
3. Coding Standards and Conventions
Define your team's coding style. Be specific:
- Naming conventions (camelCase, PascalCase, snake_case)
- File structure (e.g., feature-based vs. type-based)
- Testing requirements (unit tests, integration tests)
Example:
## Coding Conventions
- Use TypeScript with strict mode.
- Components go in `src/components/`.
- All public functions must have JSDoc comments.
- Write unit tests for all business logic.
4. Architectural Decisions
Document significant architectural choices and their rationale. This prevents the AI from suggesting contradictory approaches.
Example:
## Architecture
- We use a microservices architecture with RabbitMQ for async communication.
- Authentication is handled by a dedicated auth service (JWT-based).
- File uploads are stored on S3, not on the local filesystem.
5. Behavioral Instructions for Claude Code
This is where you can give direct instructions to the AI. According to the official spec, you can set rules like:
- "Always ask before refactoring code."
- "Prefer functional programming patterns."
- "When suggesting fixes, explain the root cause."
Example:
## AI Behavior
- When generating code, use async/await over callbacks.
- If a security vulnerability is detected, flag it immediately.
- Provide examples with each explanation.
Common Mistakes and How to Avoid Them
The developers who encountered issues with Claude Code often made these mistakes:
| Mistake | Consequence | Fix |
|---|---|---|
| Too vague | AI gives generic advice | Add specific examples |
| Outdated | AI suggests deprecated libraries | Update file regularly |
| Too long | AI ignores critical parts | Keep it under 500 lines |
| Contradictory | AI gets confused | Review for consistency |
Real-World Example: A Startup's Experience
The material examined in the Habr article cites a startup that reduced context-switching time by 40% after properly setting up CLAUDE.md. The team implemented a version-controlled file that they updated every sprint. New team members could onboard faster because the AI could answer questions based on the file's content. The key was including a 'decision log' section that recorded why certain architectural choices were made.
Best Practices from the Community
Based on the official specification and user feedback:
- Version control your CLAUDE.md — Treat it like code. Use git to track changes.
- Keep it concise — Aim for 200-500 lines. Use bullet points and tables for readability.
- Update after major decisions — When you change frameworks or add new features, reflect that in the file.
- Use placeholders for secrets — Never hardcode API keys. Use environment variable names.
- Test with a new developer — Ask someone unfamiliar with the project to read
CLAUDE.mdand see if they can understand the project essence.
Conclusion
CLAUDE.md is more than just a configuration file — it's the bridge between your project's vision and Claude Code's execution. By writing it according to the official specification, you ensure that your AI advisor consistently understands the 'essence of the project' without needing constant reminders. Start by creating a simple version today, iterate based on your team's needs, and watch your productivity improve.
Remember: A well-written CLAUDE.md turns Claude Code from a generic assistant into a domain-specific expert that truly understands your codebase. Don't ignore the reminders — embrace them as opportunities to refine your instructions.
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