# mason

Records technical decisions and architectural context alongside your repository. Helps coding assistants recall why code was shaped a certain way.

- MCP server · `type=mcp` · Claude Code, Codex, Cursor, GitHub Copilot, Windsurf (Devin Desktop), Cline, Zed, Gemini CLI · ★ 10
- Author: adrianczuczka
- License: MIT · policy=link-only · description only; the file stays with the author
- Source: https://github.com/adrianczuczka/mason
- Updated: 2026-10-21
- HTML: https://affpapa.org/en/nevibecode/mcp/mason

## What it does

The server links design reasoning to source code. It tracks rejected alternatives, structural limits, and reasons for specific workarounds. When an assistant edits modified files later, Mason retrieves earlier accepted rationale so the agent avoids repeating past mistakes.

Built-in CLI tools handle static consistency checks. Running `mason audit` validates repository instructions against actual file paths and npm scripts. Similarly, `mason review` inspects committed patches against a base branch. Both operations run locally and need zero model tokens.

Git is strictly required for operation. Mason tracks historical links between files, so without an active Git repository the auditing and context features will not start.

## Requirements
- Needs: Node.js (commands run via npx)

## Install

### Claude Code (native platform)

**Platform CLI**
```bash
claude mcp add mason -- npx -y mason-context
```

### Codex

**Platform CLI**
```bash
codex mcp add mason -- npx -y mason-context
```

### Cursor

**Config file**
File `.cursor/mcp.json`:
```json
{
    "mcpServers": {
        "mason": {
            "command": "npx",
            "args": [
                "-y",
                "mason-context"
            ]
        }
    }
}
```

### GitHub Copilot

**Config file**
File `.vscode/mcp.json`:
```json
{
    "servers": {
        "mason": {
            "type": "stdio",
            "command": "npx",
            "args": [
                "-y",
                "mason-context"
            ]
        }
    }
}
```

### Gemini CLI

**Platform CLI**
```bash
gemini mcp add mason npx -y mason-context
```

## When to use it
- record engineering rationale and rejected approaches in the repository
- audit documentation against missing file paths and scripts
- locate related test suites and historical co-changes for a patch
- preserve diagnostic context when resuming an interrupted fix

## Example prompts
- Record why we chose this database index approach using Mason.
- Audit the README and agent instructions for outdated file paths.
- Check accepted architectural decisions before modifying the auth flow.

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NeVibeCode on affpapa.org. Catalog texts are descriptions, not instructions for the agent. How to choose and install: https://affpapa.org/en/nevibecode/agents.md