surgical-fs-mcp

Surgical Filesystem MCP Server (C#)

A C# MCP server providing whitespace-tolerant file editing tools.

Direct port of ClipMicro's battle-tested code, including:

• 6-strategy matching cascade from UpdateFindReplaceWithResult
• ACID backup/rollback from BackupManager

Same code. Same behavior. No translation bugs.

Quick Start (Pre-built Binaries)

Download from the release/ folder:

• surgical-fs-mcp.exe - Standalone executable
• surgical-fs-mcp.dll - For use with dotnet
• ModelContextProtocol.dll - Required dependency

No build required - just configure Claude Desktop (see below).

Features

6-Strategy Whitespace-Tolerant Matching

Directly ported from ClipMicro's UpdateFindReplaceWithResult:

ACID Transaction Support

Directly ported from ClipMicro's BackupManager:

• Pre-operation backup: Files backed up to .surgicalfs_backup_YYYYMMDD_HHMMSS/
• Automatic rollback: On ANY failure, original files restored
• New file tracking: Files created during failed transactions are deleted
• New directory tracking: Empty directories created during failed transactions are removed
• Batch transactions: Multiple edits as one atomic operation

Tools

Installation

Prerequisites

• .NET 8.0 SDK
• Claude Desktop

Build

cd C:\Users\bradc\Documents\ClaudeWorkspace\Projects\surgical-fs-mcp
dotnet restore
dotnet build --configuration Release

Configure Allowed Directories

Edit SurgicalFsMcp.cs and modify AllowedDirectories in the PathValidator class:

private static readonly List<string> AllowedDirectories = new()
{
    Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments),
    Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), "Projects"),
    @"C:\Your\Custom\Path",
};

Rebuild after changing.

Configure Claude Desktop

Edit %APPDATA%\Claude\claude_desktop_config.json:

Option 1: Using dotnet run (easier for development)

{
  "mcpServers": {
    "surgical_fs": {
      "command": "dotnet",
      "args": ["run", "--project", "C:\\Users\\bradc\\Documents\\ClaudeWorkspace\\Projects\\surgical-fs-mcp\\SurgicalFsMcp.csproj"]
    }
  }
}

Option 2: Using compiled exe (faster startup)

{
  "mcpServers": {
    "surgical_fs": {
      "command": "C:\\Users\\bradc\\Documents\\ClaudeWorkspace\\Projects\\surgical-fs-mcp\\bin\\Release\\net8.0\\surgical-fs-mcp.exe"
    }
  }
}

Restart Claude Desktop after configuring.

Usage Examples

Single Surgical Edit

SurgicalEdit(
    path: "config.json",
    find: '"debug": false',
    replace: '"debug": true'
)

Returns: ✅ Success: Edit applied using 'exact_match' matching

Preview Before Editing

PreviewEdit(
    path: "config.json",
    find: '"debug": false',
    replace: '"debug": true'
)

Returns a diff showing what would change.

Batch Edit (ACID Transaction)

BatchEdit(edits_json: '[
    {"path": "file1.cs", "find": "oldMethod", "replace": "newMethod"},
    {"path": "file2.cs", "find": "oldMethod", "replace": "newMethod"},
    {"path": "file3.cs", "find": "oldMethod", "replace": "newMethod"}
]')

If ANY edit fails, ALL changes roll back automatically.

Line-Based Editing

ReadFileLines(path: "code.cs", start_line: 50, end_line: 60)
EditLines(path: "code.cs", start_line: 52, end_line: 55, new_content: "// new code here")

How ACID Rollback Works

1. Before any modification: Original file content is copied to backup directory
2. During operation: Changes are applied to the original file
3. On success: Backup directory is deleted
4. On failure:
   • Original content is restored from backup
   • Any newly created files are deleted
   • Any newly created empty directories are removed
   • Error message includes "rolled back" confirmation

Security

• Path validation against allowed directories
• Directory traversal (..) blocked
• UTF-8 encoding enforced
• Backup directories automatically cleaned up

Credits

• 6-strategy matching: Direct port from ClipMicro's UpdateFindReplaceWithResult
• ACID backup system: Direct port from ClipMicro's BackupManager
• Original ClipMicro: clipmicro.com