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SOUL.md vs CLAUDE.md vs .cursorrules: Which AI Agent Config File Should You Use (and When)?

ClawAgora Team·

Three config files. Three tools. Three completely different jobs. Yet developers keep asking: "Do I need SOUL.md if I already have CLAUDE.md?" or "Is .cursorrules the same thing as SOUL.md?"

The short answer is no. These files are not interchangeable. They are not competing standards. They serve different tools, different scopes, and different purposes. Conflating them leads to poorly configured agents, wasted effort, and missed capabilities.

This guide breaks down exactly what each file does, how they compare, when to use each, and how they fit together in a modern AI-assisted development workflow.

The Three Files at a Glance

Before diving into the details, here is the essential distinction:

  • SOUL.md defines who an AI agent is (OpenClaw)
  • CLAUDE.md defines how an AI assistant should code in a specific project (Claude Code)
  • .cursorrules defines how an AI assistant should code in a specific project (Cursor)

SOUL.md is about identity. CLAUDE.md and .cursorrules are about coding behavior. This is the fundamental divide that most comparisons miss.

SOUL.md: The Agent Identity File

What It Is

SOUL.md is the personality and behavioral configuration file for OpenClaw agents. It lives in the agent's workspace (typically ~/.openclaw/workspace/SOUL.md) and gets loaded into the system prompt at the start of every session. It is the single most influential file in shaping how an OpenClaw agent communicates, reasons, and behaves.

What It Defines

SOUL.md answers the question: who is this agent? It covers:

  • Personality and tone - Is the agent formal or casual? Opinionated or neutral? Verbose or terse?
  • Values and priorities - What does the agent care about? Accuracy over speed? Thoroughness over brevity?
  • Behavioral boundaries - What should the agent refuse to do? What ethical guardrails apply?
  • Communication style - How should the agent structure responses? Does it use humor? How does it handle disagreement?

Example SOUL.md

# SOUL.md - Who You Are

## Core Truths

Be genuinely helpful, not performatively helpful.
Skip the "Great question!" filler. Just help.

Have opinions. You are allowed to disagree, prefer things,
find stuff amusing or boring. Do not be a sycophant.

Be resourceful before asking. Try to figure it out.
Read the file. Check the context. Search for it.
Then ask if you are stuck.

## Communication Style

- Default to concise. Expand when the topic demands it.
- Use plain language. Avoid jargon unless the user speaks it first.
- When uncertain, say so. "I am not sure" is always valid.
- No corporate speak. No "leverage" or "synergize" or "circle back."

## Boundaries

- Never fabricate sources, URLs, or citations.
- If a request seems harmful, explain why and suggest an alternative.
- Protect user privacy. Do not reference personal details in group contexts.

Key Characteristics

  • Scope: Agent-wide. Applies to every session, every conversation, every context the agent enters.
  • Persistence: Loaded from disk at every session start. Survives restarts, crashes, and context compaction.
  • Format: Plain Markdown. Human-readable and version-controllable.
  • Size guidance: Under 2KB. Every character competes with conversation for context window space.
  • Tool: OpenClaw only.

What SOUL.md Is NOT

SOUL.md is not a coding style guide. It does not specify tab widths, naming conventions, or framework preferences. It is not about what the agent does - it is about how the agent approaches everything it does. Operational rules belong in AGENTS.md. Project-specific coding rules do not belong in SOUL.md at all.

CLAUDE.md: The Project Instructions File

What It Is

CLAUDE.md is the project-level configuration file for Claude Code, Anthropic's CLI tool for AI-assisted software development. It sits in the root of your project repository and tells Claude how to work within that specific codebase.

What It Defines

CLAUDE.md answers the question: how should Claude code in this project? It covers:

  • Coding standards - Language preferences, formatting rules, naming conventions
  • Project context - Architecture decisions, key dependencies, file structure explanations
  • Workflow instructions - How to run tests, what linting rules apply, deployment procedures
  • Constraints - What not to do, what patterns to avoid, what files not to touch

Example CLAUDE.md

# CLAUDE.md

## Project Overview

This is a Next.js 14 App Router project using TypeScript,
Tailwind CSS, and Prisma ORM with a PostgreSQL database.

## Coding Standards

- Use TypeScript strict mode. No `any` types.
- Prefer named exports over default exports.
- Use server components by default. Add "use client" only when needed.
- All database queries go through Prisma. No raw SQL.

## Testing

- Run tests with `npm test`
- Unit tests use Vitest. Integration tests use Playwright.
- Every new feature needs at least one test.

## File Structure

- `src/app/` - App Router pages and layouts
- `src/components/` - Shared React components
- `src/lib/` - Utility functions and shared logic
- `prisma/` - Database schema and migrations

## Do Not

- Do not modify `next.config.ts` without discussion.
- Do not add new dependencies without justification.
- Do not use `console.log` in production code. Use the logger.

Key Characteristics

  • Scope: Project-level. Applies only within the repository where the file lives.
  • Hierarchy: Supports global (~/.claude/CLAUDE.md), project (repo root), and directory-level overrides.
  • Persistence: Read when Claude Code starts a session. Not persistent across tool restarts in the same way SOUL.md is.
  • Format: Markdown with conventions understood by Claude Code.
  • Size guidance: No hard limit, but conciseness improves adherence. Aim for practical, not exhaustive.
  • Tool: Claude Code only.

What CLAUDE.md Is NOT

CLAUDE.md is not a personality file. It does not define who Claude is - Claude already has a personality. It is not about tone, values, or behavioral boundaries in a philosophical sense. It is about the practical mechanics of writing code in a specific project. You would never put "be funny" or "have strong opinions" in a CLAUDE.md. You would put "use 2-space indentation" and "always handle error cases explicitly."

.cursorrules: The Editor AI Rules File

What It Is

.cursorrules is the project-level configuration file for the AI assistant inside Cursor, a VS Code-based code editor with deep AI integration. It tells Cursor's AI how to behave when generating, editing, or explaining code within a specific project.

What It Defines

.cursorrules answers the same question as CLAUDE.md but for a different tool: how should the AI code in this project? It covers:

  • Code generation preferences - Languages, frameworks, patterns to use or avoid
  • Style rules - Formatting, naming, documentation standards
  • Project-specific context - Architecture, dependencies, conventions
  • Response format - How the AI should present code suggestions

Example .cursorrules

You are an expert in TypeScript, React, Next.js App Router, and Tailwind CSS.

Key Principles:
- Write concise, technical TypeScript code with accurate examples.
- Use functional and declarative programming patterns. Avoid classes.
- Prefer iteration and modularization over code duplication.
- Use descriptive variable names with auxiliary verbs (isLoading, hasError).

Naming Conventions:
- Use lowercase with dashes for directories (components/auth-wizard).
- Use PascalCase for component files (AuthWizard.tsx).
- Favor named exports for components.

TypeScript Usage:
- Use TypeScript for all code. Prefer interfaces over types.
- Avoid enums. Use const maps instead.
- Use functional components with TypeScript interfaces for props.

Syntax and Formatting:
- Use the "function" keyword for pure functions.
- Avoid unnecessary curly braces in conditionals.
- Use declarative JSX.

Error Handling:
- Implement proper error boundaries.
- Use early returns for error conditions.
- Log errors appropriately for debugging.

Key Characteristics

  • Scope: Project-level. Applies within the repository where the file lives.
  • Hierarchy: Project-level .cursorrules, plus global rules in Cursor settings.
  • Persistence: Read when Cursor opens the project. Refreshed on file change.
  • Format: Plain text or Markdown. Less structured than CLAUDE.md.
  • Size guidance: Keep it focused. Overly long rules get diluted in the context window.
  • Tool: Cursor only.

What .cursorrules Is NOT

Like CLAUDE.md, .cursorrules is not an identity file. It does not shape a persistent agent's personality across sessions. It is instructions for a coding assistant within a specific editor context. The AI assistant in Cursor has no "self" between sessions - it reads the rules fresh every time you open the project.

Side-by-Side Comparison

Dimension SOUL.md CLAUDE.md .cursorrules
Tool OpenClaw Claude Code Cursor
Primary purpose Agent identity and personality Project coding instructions Project coding instructions
Scope Agent-wide (all sessions) Project-level (per repo) Project-level (per repo)
What it defines Who the agent IS How to code HERE How to code HERE
Format Markdown Markdown Plain text / Markdown
Lives in ~/.openclaw/workspace/ Project root (or ~/.claude/) Project root
Loaded when Every session start Claude Code session start Cursor project open
Hierarchy support Single file Global + project + directory Global + project
Personality content Yes (primary purpose) No No
Coding style content No Yes (primary purpose) Yes (primary purpose)
Persists across sessions Yes (file on disk) Yes (file on disk) Yes (file on disk)
Size recommendation Under 2KB Concise as practical Concise as practical
Version controllable Yes Yes (committed to repo) Yes (committed to repo)
Shareable as template Yes (via workspace templates) Yes (committed to repo) Yes (committed to repo)

The Decision Flowchart

Choosing the right file is straightforward once you understand the mapping:

What tool are you configuring?
|
+-- OpenClaw agent?
|   |
|   +-- Defining personality, tone, values?
|   |   --> SOUL.md
|   |
|   +-- Defining operational rules and procedures?
|   |   --> AGENTS.md (not covered here, but worth knowing)
|   |
|   +-- Defining coding style for a specific project?
|       --> The agent reads project files directly. Consider
|           adding a CONTRIBUTING.md or CLAUDE.md if the agent
|           uses Claude as its LLM backend.
|
+-- Claude Code (CLI)?
|   |
|   +-- Global preferences across all projects?
|   |   --> ~/.claude/CLAUDE.md
|   |
|   +-- Project-specific instructions?
|   |   --> CLAUDE.md in project root
|   |
|   +-- Directory-specific overrides?
|       --> CLAUDE.md in subdirectory
|
+-- Cursor (editor)?
|   |
|   +-- Project-specific instructions?
|   |   --> .cursorrules in project root
|   |
|   +-- Global preferences?
|       --> Cursor settings (Rules section)
|
+-- Multiple tools on the same project?
    --> Use ALL relevant config files. They do not conflict.
        SOUL.md for your OpenClaw agent personality.
        CLAUDE.md for Claude Code sessions.
        .cursorrules for Cursor sessions.

The critical insight: you are not choosing between these files. You are choosing which tools you use, and each tool has its own config file. Asking "should I use SOUL.md or CLAUDE.md?" is like asking "should I use .gitignore or .dockerignore?" - they solve different problems for different tools.

When They Overlap (and When They Do Not)

The Overlap: Coding Preferences

CLAUDE.md and .cursorrules have significant overlap in purpose - both define coding preferences for an AI assistant. If you use both Cursor and Claude Code on the same project, you will likely have similar content in both files. The "use TypeScript strict mode" rule belongs in both.

This duplication is intentional, not a problem. Each tool reads its own file. Maintaining both ensures consistent AI behavior regardless of which tool you use on a given day.

The Divergence: Identity vs. Instructions

SOUL.md is in a different category entirely. It does not overlap with CLAUDE.md or .cursorrules because it operates at a different level of abstraction. SOUL.md says "be direct, have opinions, do not fabricate." CLAUDE.md says "use Vitest for testing, prefer named exports." They are not competing directives - they are complementary layers.

An OpenClaw agent with a well-crafted SOUL.md might use Claude as its underlying LLM. That agent could work on a project that has a CLAUDE.md. But the SOUL.md defines the agent's consistent personality across all projects, while the CLAUDE.md provides project-specific coding context. They stack, not conflict.

The Non-Overlap: Tool Boundaries

SOUL.md has zero effect in Claude Code or Cursor. CLAUDE.md has zero effect in OpenClaw or Cursor. .cursorrules has zero effect in Claude Code or OpenClaw. These are tool-specific files, full stop. Putting SOUL.md content in a .cursorrules file does not give Cursor's AI a personality - it just wastes context window tokens on instructions the AI cannot meaningfully follow in that context.

Migration and Cross-Pollination Tips

Porting Between CLAUDE.md and .cursorrules

Since both files serve similar purposes (project-level coding instructions), content is relatively portable between them:

  1. Extract the universal rules. Identify coding standards that apply regardless of tool: naming conventions, formatting rules, architectural patterns.
  2. Adapt tool-specific features. CLAUDE.md supports directory-level overrides and a global hierarchy. .cursorrules relies on Cursor's settings for global rules. Adjust accordingly.
  3. Keep format conventions. CLAUDE.md works best as structured Markdown with headers. .cursorrules works well as direct instructions with a persona framing ("You are an expert in...").
  4. Maintain both. Do not try to symlink or auto-generate one from the other. The files are small, the maintenance cost is low, and each tool has subtle differences in how it interprets instructions.

Building a SOUL.md from Scratch

If you are new to OpenClaw and coming from Claude Code or Cursor, resist the urge to copy your CLAUDE.md into a SOUL.md. They serve different purposes. Instead:

  1. Start with personality. How do you want the agent to communicate? Formal? Casual? Opinionated? Measured?
  2. Define values. What matters most? Accuracy? Speed? Thoroughness? Creativity?
  3. Set boundaries. What should the agent never do? What ethical lines should it respect?
  4. Keep it short. Under 2KB. Every word counts because this file is loaded into every single session.

Workspace templates on platforms like ClawAgora include pre-configured SOUL.md files tuned for specific use cases - research assistants, development helpers, content creators, home automation agents. Starting from a template and customizing is often faster than writing from scratch.

Sharing Your Configuration

One advantage of all three formats being plain text files: they are trivially shareable.

  • CLAUDE.md and .cursorrules naturally live in your git repository. Every team member who clones the repo gets the same AI configuration. This is team-level consistency for free.
  • SOUL.md is shareable through OpenClaw workspace templates. When you package a workspace for sharing, the SOUL.md travels with it, giving the recipient a fully configured agent personality out of the box.

Common Mistakes

Mistake 1: Putting Coding Rules in SOUL.md

SOUL.md is not the place for "use 4-space indentation" or "prefer functional components." Those are project-specific coding preferences. They belong in AGENTS.md (for agent-wide coding habits) or in the project's own documentation. SOUL.md is for personality and values - the stuff that stays constant regardless of what project the agent is working on.

Mistake 2: Putting Personality in CLAUDE.md

"Be friendly and encouraging" does not belong in CLAUDE.md. Claude already has a personality. CLAUDE.md is for practical coding instructions, not personality customization. If you find yourself writing tone and communication style directives in CLAUDE.md, you are probably looking for a different tool.

Mistake 3: Treating .cursorrules as a System Prompt

Some developers write elaborate persona descriptions in .cursorrules: backstory, motivations, philosophical outlook. This wastes context. Cursor's AI is a coding assistant, not a character. Give it coding rules, not a biography. The "You are an expert in..." framing works well, but keep it functional.

Mistake 4: Assuming One File Covers All Tools

The most common mistake. A developer creates a thorough CLAUDE.md and assumes their Cursor sessions will pick it up. They will not. Each tool reads its own file. If you use multiple AI tools, maintain multiple config files. The duplication is intentional and manageable.

Mistake 5: Making Config Files Too Long

All three files compete for context window space with actual conversation and code. A 10KB SOUL.md means 10KB less room for the agent to think. A 5KB .cursorrules means 5KB less room for Cursor to reason about your code. Be concise. A focused 500-word config file outperforms a sprawling 3000-word one.

A Practical Setup for Multi-Tool Developers

Here is what a well-configured project looks like for a developer who uses all three tools:

my-project/
├── .cursorrules          # Cursor AI coding rules
├── CLAUDE.md             # Claude Code project instructions
├── src/
├── tests/
├── package.json
└── ...

~/.claude/
└── CLAUDE.md             # Global Claude Code preferences

~/.openclaw/workspace/
├── SOUL.md               # Agent personality (shared across all projects)
├── AGENTS.md             # Agent operating rules
├── MEMORY.md             # Agent long-term memory
└── USER.md               # Information about you

The project-level files (.cursorrules, CLAUDE.md) travel with the repo. The agent-level files (SOUL.md, AGENTS.md, MEMORY.md) live in the OpenClaw workspace and apply globally.

This separation is clean and intentional:

  • Switch projects? Your coding rules change (new .cursorrules, new CLAUDE.md), but your agent's personality stays the same (SOUL.md is constant).
  • Switch tools? Your coding rules might be duplicated across .cursorrules and CLAUDE.md, but each tool reads its own file and behaves consistently.
  • Switch agents? Different SOUL.md means a different personality, even on the same project.

Conclusion

The proliferation of AI config files is not fragmentation - it is specialization. Each file exists because each tool has different needs:

  • SOUL.md exists because persistent AI agents need a stable identity that transcends any individual project or conversation.
  • CLAUDE.md exists because Claude Code needs project-specific coding context to write good code in your particular codebase.
  • .cursorrules exists because Cursor needs the same kind of project-specific guidance in its editor context.

They are not competitors. They are not alternatives. They are complementary tools for complementary purposes. Use the ones that match the tools you use, configure them for their intended purpose, and resist the urge to make one file do everything.

If you are building OpenClaw agents and want a head start on SOUL.md configuration, community-created workspace templates on ClawAgora include pre-configured personality files alongside full workspace architectures - skills, memory structures, and operating rules ready to customize.

The right question is not "which config file should I use?" It is "which tools am I using, and have I configured each one properly?"

Frequently Asked Questions

What is the difference between SOUL.md and CLAUDE.md?

SOUL.md and CLAUDE.md serve fundamentally different purposes for different tools. SOUL.md is an OpenClaw configuration file that defines an AI agent's personality, tone, values, and behavioral boundaries - essentially who the agent IS as a persistent entity. CLAUDE.md is a Claude Code configuration file that defines project-level coding instructions, preferences, and context for the Claude assistant during development sessions. SOUL.md shapes identity across all interactions; CLAUDE.md shapes coding behavior within a specific project.

Can I use SOUL.md, CLAUDE.md, and .cursorrules in the same project?

Yes, and in many cases you should. These files target different tools and serve different purposes, so they do not conflict. SOUL.md configures your OpenClaw agent, CLAUDE.md configures Claude Code, and .cursorrules configures Cursor. A developer who uses all three tools would maintain all three files. The key is understanding that each file speaks to a different AI system - they are not interchangeable alternatives but complementary configurations for different parts of your workflow.

Which AI config file should I start with if I only use one tool?

Start with the config file that matches your primary AI tool. If you use Claude Code for development, create a CLAUDE.md with your coding standards and project context. If you use Cursor, create a .cursorrules file with your style preferences and constraints. If you use OpenClaw as a persistent AI agent, start with SOUL.md to define the agent's personality and behavioral boundaries. You can always add the others later as you adopt additional tools.

How do .cursorrules differ from CLAUDE.md?

.cursorrules and CLAUDE.md are both project-level configuration files for AI coding assistants, but they target different editors. .cursorrules configures the AI assistant inside Cursor (a VS Code fork), while CLAUDE.md configures Claude Code (Anthropic's CLI tool). They share a similar purpose - defining coding style, project conventions, and constraints - but differ in syntax, supported features, and how they integrate with their respective tools. .cursorrules uses a plain text or structured format read by Cursor's AI, while CLAUDE.md uses Markdown with conventions understood by Claude Code.

Do I need SOUL.md if I already have a system prompt for my AI agent?

SOUL.md replaces and improves upon a traditional system prompt for OpenClaw agents. Rather than a static prompt string embedded in code, SOUL.md is a version-controlled Markdown file that lives in the agent's workspace and can be edited, shared, and templated. It is loaded into the system prompt automatically at every session start. The advantage over a raw system prompt is that SOUL.md is human-readable, easily auditable, shareable as part of workspace templates, and can be updated without code changes.