Crash
MCP server for structured and efficient reasoning with step validation, branching, and revisions.
What is Crash?
Crash is a Model Context Protocol (MCP) server that allows AI assistants like Claude, Cursor, and VS Code to mcp server for structured and efficient reasoning with step validation, branching, and revisions.
MCP server for structured and efficient reasoning with step validation, branching, and revisions.
This server falls under the Coding Agents category on MCPgee, the world's largest MCP server directory with 33,000+ servers.
Features
- MCP server for structured and efficient reasoning with step
Use Cases
Maintainer
Works with
Installation
Manual Installation
npx crashConfiguration
Configuration Details
claude_desktop_config.json
Performance
Response Metrics
Resource Usage
How to Set Up and Use Crash
CRASH (Controlled Reasoning And Structured Hypothesis) is a TypeScript MCP server that provides Claude with a structured reasoning tool, enabling step-by-step analysis with built-in validation, branching for exploring alternative hypotheses, and revision capabilities to correct earlier steps. Each reasoning step includes a purpose, thought, outcome, and next action, creating a transparent audit trail of the AI's problem-solving process. Teams use it for complex debugging sessions, architecture decisions, and multi-step analyses where they need to see Claude's reasoning chain rather than just the final answer.
Prerequisites
- Node.js 18 or later with npx available
- An MCP-compatible client such as Claude Desktop, Claude Code, or Cursor
- No API keys required — CRASH is a pure reasoning tool with no external service dependencies
Add CRASH to Claude Desktop config
Open your Claude Desktop configuration file (~/ Library/Application Support/Claude/claude_desktop_config.json on macOS) and add the crash server entry. The -y flag ensures npx downloads it automatically.
{
"mcpServers": {
"crash": {
"command": "npx",
"args": ["-y", "crash-mcp"]
}
}
}Or add via Claude Code CLI
If you are using Claude Code instead of Claude Desktop, add the CRASH server with a single CLI command.
claude mcp add crash -- npx -y crash-mcpConfigure optional environment variables
CRASH has several optional environment variables that control behavior. The most useful ones are CRASH_STRICT_MODE (rejects incomplete steps) and CRASH_MAX_BRANCH_DEPTH (limits how deep branching can go). Add them to the env block if needed.
{
"mcpServers": {
"crash": {
"command": "npx",
"args": ["-y", "crash-mcp"],
"env": {
"CRASH_STRICT_MODE": "false",
"CRASH_MAX_BRANCH_DEPTH": "5",
"CRASH_SESSION_TIMEOUT": "60"
}
}
}
}Restart Claude Desktop
Quit and reopen Claude Desktop. On first use, npx will download crash-mcp automatically. The reasoning tool will be available in Claude's tool list.
Invoke structured reasoning
Ask Claude to use CRASH for a complex problem. Claude will use the structured reasoning tool to break the problem into numbered steps, each with a purpose, thought, outcome, and next action.
Crash Examples
Client configuration
Claude Desktop config entry for CRASH with optional environment variables.
{
"mcpServers": {
"crash": {
"command": "npx",
"args": ["-y", "crash-mcp"],
"env": {
"CRASH_STRICT_MODE": "false",
"CRASH_OUTPUT_FORMAT": "console",
"CRASH_MAX_BRANCH_DEPTH": "5"
}
}
}
}Prompts to try
Example prompts that benefit most from CRASH structured reasoning.
- "Use structured reasoning to diagnose why my PostgreSQL query is returning duplicate rows"
- "Walk me through a step-by-step analysis of whether I should use microservices or a monolith for my new project"
- "Apply CRASH reasoning to evaluate three different caching strategies for my API and recommend the best one"
- "Use structured steps to identify the root cause of this React component re-rendering too frequently"
- "Break down the security implications of storing JWTs in localStorage vs httpOnly cookies using structured reasoning"Troubleshooting Crash
CRASH reasoning steps appear but lack detail or are cut short
Set CRASH_STRICT_MODE to 'true' in the env config — this forces Claude to provide all required fields (purpose, thought, outcome, next_action, rationale) for every step. Also increase the context window in your client settings if available.
npx crash-mcp fails with 'package not found' or version errors
The correct package name is 'crash-mcp' (with a hyphen). Run 'npx -y crash-mcp' in a terminal to confirm it installs. If you see version conflicts, clear the npx cache with 'npx clear-npx-cache' and try again.
Branching produces too many steps and the session becomes unwieldy
Set CRASH_MAX_BRANCH_DEPTH to a lower value like '3' to limit how many levels of alternative hypotheses Claude can explore. Also set CRASH_ENABLE_SESSIONS to 'false' if you only need single-session reasoning without history.
Frequently Asked Questions about Crash
What is Crash?
Crash is a Model Context Protocol (MCP) server that mcp server for structured and efficient reasoning with step validation, branching, and revisions. It connects AI assistants to external tools and data sources through a standardized interface.
How do I install Crash?
Follow the installation instructions on the Crash GitHub repository. Clone the repo, install dependencies, and add the server config to your AI client.
Which AI clients work with Crash?
Crash works with all major MCP-compatible AI clients including Claude Desktop, Claude Code, Cursor, VS Code (GitHub Copilot), Windsurf, and Cline.
Is Crash free to use?
Yes, Crash is open source and available under the MIT license. You can use it freely in both personal and commercial projects.
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