quanticsoul4772/macos-shell

macOS Shell MCP Server

A Model Context Protocol (MCP) server that provides shell command execution on macOS with session management, working directory persistence, environment isolation, and background process management.

Architecture

The server includes a layer that intercepts all commands, providing caching (85% hit rate), deduplication (80% reduction), and error correction. Commands that hit the cache return in ~1ms, while 15% of requests require tool execution.

Installation

# Clone the repository
git clone https://github.com/quanticsoul4772/macos-shell.git
cd macos-shell

# Install dependencies
npm install

# Build the server
npm run build

# Run tests (optional)
npm test

# Start the server (optional)
npm start

Configuration

Add to your Claude Desktop configuration file:

Location: ~/Library/Application Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "macos-shell": {
      "command": "node",
      "args": [
        "/path/to/macos-shell/build/server.js"
      ],
      "type": "stdio"
    }
  }
}

Restart Claude Desktop after adding the configuration.

Features

Features

• Session Management: Create multiple named sessions with isolated environments
• Working Directory Persistence: Each session maintains its own working directory
• Environment Variables: Set and manage environment variables per session
• Command History: Track executed commands with timing and output
• Script Execution: Run multi-line shell scripts
• Background Processes: Run processes in the background with output capture
• Error Handling: Error reporting with exit codes

Caching and Performance

Command Caching

• Cacheable commands execute in 1ms vs 120ms uncached
• Status commands (git status, ls, docker ps) are never cached
• Variable TTLs:
  • Never: Status/monitoring commands
  • 30s: Directory context (pwd, whoami)
  • 5m: Config files (cat package.json)
  • 30m: Documentation (cat README.md)
  • 1h: Static content (node --version, --help)
• Cache hit indicator: "cached": true with "cacheStrategy" in responses
• Disable caching: Set MCP_DISABLE_CACHE=true environment variable

Deduplication

• 10-second deduplication window for identical commands
• Batches multiple executions into single operation
• Normalizes command variations (ls -la = ls -al)

Error Recovery

• Corrects file path typos using Levenshtein distance
• Retries network errors with exponential backoff
• Adds flags like --legacy-peer-deps for npm errors
• Suggests command alternatives (python → python3)

Performance Monitoring

• Stats logged every minute to stderr
• Tracks cache hit rate, deduplication rate, error recovery
• Shows command patterns for optimization

Available Tools (35 Total)

Command Execution (3 tools)

• run_command - Execute shell commands

  • Parameters: command, args[], session?, cwd?, env?, timeout?
  • Returns: Exit code, stdout, stderr

• run_script - Execute multi-line shell scripts

  • Parameters: script, session?, timeout?
  • Returns: Exit code, stdout, stderr

• batch_execute_enhanced - Execute commands with conditional logic and retries

  • Parameters: commands[] with conditions, parallel?, stopOnFirstFailure?, maxOutputLines?, includeFullOutput?
  • Returns: Execution results with skip reasons
  • Output truncation to prevent context window overload

Session Management (3 tools)

• create_shell_session - Create a new named session with isolated environment

  • Parameters: name, cwd?, env?
  • Returns: Session ID and working directory

• list_shell_sessions - List active sessions with details

  • Parameters: None
  • Returns: List of sessions with creation time, last used, command count, background process count

• close_session - Close a session and free resources

  • Parameters: session
  • Returns: Success confirmation

Working Directory (2 tools)

• cd - Change working directory (persists in session)

  • Parameters: path, session?
  • Returns: New working directory path

• pwd - Get current working directory

  • Parameters: session?
  • Returns: Current directory path

Environment Management (2 tools)

• set_env - Set environment variables in a session

  • Parameters: name, value, session?
  • Returns: Confirmation with variable details

• get_env - Get environment variables

  • Parameters: name?, session?
  • Returns: Variable value(s)

History (1 tool)

• history - View command history for a session
  • Parameters: session?, limit?
  • Returns: Commands with timestamps, exit codes, duration

Background Process Management (8 tools)

• run_background - Start a command in the background

  • Parameters: command, args[], session?, name?
  • Returns: Process ID, PID, status

• list_processes - List background processes with resource monitoring

  • Parameters: session? (optional filter)
  • Returns: JSON with processes including CPU%, memory, trends, and runtime

• get_process_output - Retrieve output from a background process with search

  • Parameters: process_id, lines?, from_line?, search?, case_sensitive?
  • Returns: Buffered stdout/stderr with line numbers and type indicators

• stream_process_output - Stream output from a background process

  • Parameters: process_id, after_line?, timeout?, max_lines?
  • Returns: New output lines as they arrive, with streaming hints

• kill_process - Terminate a background process (including orphaned processes)

  • Parameters: process_id, signal? (SIGTERM/SIGKILL)
  • Returns: Success confirmation

• cleanup_orphans - Manage processes from previous server sessions

  • Parameters: mode? (list/kill/interactive), force? (use SIGKILL)
  • Returns: List of orphans or cleanup results

• kill_all_matching - Kill processes matching a pattern

  • Parameters: pattern, pattern_type? (text/regex), signal?, dry_run?
  • Returns: List of killed processes or dry run preview

• save_process_output - Save process output to a file

  • Parameters: process_id, file_path, format? (text/json), include_metadata?
  • Returns: Success confirmation with file details

System Tools (3 tools)

• get_system_health - Get system health information

  • Parameters: session?
  • Returns: System metrics including memory, CPU, disk, and resource usage

• preflight_check - Validate multiple conditions before operations

  • Parameters: commands[], paths[], ports[], env_vars[], session?
  • Returns: Validation results with summary

• system_profile - Gather system information in one call

  • Parameters: include[] (os, shell, node, python, git, docker, etc.)
  • Returns: Structured system information

Interactive SSH Tools (8 tools)

• ssh_interactive_start - Start an SSH session

  • Parameters: host, port?, user?, options[]?, key_file?
  • Returns: Session ID and initial output (ANSI codes stripped)

• ssh_interactive_send - Send input to an SSH session

  • Parameters: session_id, input, add_newline?
  • Returns: Output after sending input

• ssh_interactive_control - Send control characters (e.g., Ctrl+C)

  • Parameters: session_id, char
  • Returns: Success confirmation

• ssh_interactive_output - Get output from SSH session with search

  • Parameters: session_id, lines?, from_line?, search?, search_type?, case_sensitive?, invert_match?
  • Returns: Output with optional search filtering and match counts

• ssh_interactive_wait - Wait for new output from SSH session

  • Parameters: session_id, after_line, timeout?
  • Returns: New output lines as they arrive

• ssh_interactive_resize - Resize terminal dimensions

  • Parameters: session_id, cols, rows
  • Returns: Success confirmation

• ssh_interactive_close - Close an SSH session

  • Parameters: session_id
  • Returns: Success confirmation

• ssh_interactive_list - List active SSH sessions

  • Parameters: None
  • Returns: List of sessions with host, status, runtime, and output line count

Cache Management Tools (5 tools)

• cache_stats - Get cache statistics

  • Parameters: None
  • Returns: Cache size, hit rate, strategy breakdown, learned rules

• cache_clear_command - Clear specific commands from cache

  • Parameters: command
  • Returns: Number of entries cleared

• cache_clear_pattern - Clear commands matching regex pattern

  • Parameters: pattern
  • Returns: Number of entries cleared

• cache_mark_never - Mark command to never be cached

  • Parameters: command, reason
  • Returns: Success confirmation

• cache_explain - Explain cache decision for a command

  • Parameters: command
  • Returns: Cache strategy, TTL, reason, and analysis

SSH Guidelines

Session Management

• Check existing sessions before creating new ones with ssh_interactive_list()
• Reuse session IDs for command execution to avoid connection overhead
• Sessions persist across multiple tool calls
• Create new connections only when necessary
• Keep sessions alive for servers requiring multiple commands
• Use interactive sessions instead of run_command with sshpass

Common Mistakes to Avoid

• Creating new SSH connections for each command
• Using run_command with sshpass for multiple commands
• Forgetting to check ssh_interactive_list first

Technical Details

Architecture

• Language: TypeScript (ES2020)
• Runtime: Node.js (>=18.0.0)
• Dependencies: MCP SDK, Zod, Execa, UUID
• Shell: /bin/zsh (macOS default)
• Module System: NodeNext with .js extensions

Session Implementation

• Sessions are stored in memory using a Map data structure
• Each session maintains:
  • Unique ID (UUID v4)
  • Name (user-defined)
  • Working directory
  • Environment variables (isolated)
  • Command history (last 1000 commands in memory)
  • Background processes
  • Creation and last used timestamps
• Default session is created automatically
• Sessions persist to disk in ~/.macos-shell/sessions as JSON files
• On server restart:
  • Existing sessions are restored (except default)
  • Working directories are validated
  • Command history restored (last 100 commands)
  • Background processes marked as terminated

Background Process Implementation

• Processes run with detached: true using execa
• Output captured line-by-line to CircularBuffer
• CircularBuffer features:
  • Stores last 300 lines per process
  • Waiter management prevents memory leaks
  • Max 100 concurrent waiters per buffer
  • 60-second maximum wait timeout for long-polling operations
  • Cleanup of stale waiters every 30 seconds
  • Cleanup when approaching waiter limit
  • Batch notification processing
  • Cleanup on process termination
• Separate tracking for stdout and stderr
• Process states: STARTING → RUNNING → STOPPED/FAILED/KILLED/ORPHANED
• Cleanup 5 seconds after process termination
• Resource limits enforced at spawn time
• Orphan detection on server startup using process.kill(pid, 0)
• Handling for bash -c commands to prevent shell escaping issues

Error Handling

• Commands wrapped in try/catch blocks
• Typed errors with ExecaError
• Exit codes captured (null if process killed)
• Stdout/stderr typed and captured
• Timeout errors handled
• Background process spawn failures captured in output
• Bash command parsing fixed to prevent server crashes

Architecture Details

The server has been refactored from a 1,910-line file into modular components:

• Main Server: Reduced to 192 lines - handles initialization
• Tool Modules: 20 tools distributed across 4 focused modules
• Utility Modules: Reusable components (LRU cache, debouncer, buffer)
• Session Manager: Centralized session and process management (577 lines)

Architecture characteristics:

• Each module under 500 lines with single responsibility
• Memory leak prevention in background processes
• New tools can be added without touching core logic
• Components can be tested in isolation

Project Structure

macos-shell/
├── src/
│   ├── server.ts                    # Main server (192 lines)
│   ├── session-manager.ts           # Session orchestrator (350 lines)
│   ├── sessions/                    # Session modules
│   │   ├── session-types.ts         # Types and constants
│   │   ├── session-persistence.ts   # Save/load functionality
│   │   ├── background-process-manager.ts
│   │   └── command-history-manager.ts
│   ├── tools/                       # Tool implementations
│   │   ├── command-tools.ts         # Command tool orchestrator
│   │   ├── command/                 # Command tool modules
│   │   ├── process-tools.ts         # Process tool orchestrator
│   │   ├── helpers/                 # Process helper modules
│   │   ├── interactive-ssh-tool.ts  # SSH tools
│   │   ├── session-tools.ts         # Session management
│   │   ├── system-tools.ts          # System health
│   │   ├── enhanced-ssh-tool.ts     # SSH execution
│   │   └── preflight-tools.ts       # Validation tools
│   ├── ai-*.ts                      # AI optimization layer (5 files)
│   └── utils/                       # Utility modules
│       ├── logger.ts                # Structured logging
│       ├── enhanced-circular-buffer.ts
│       ├── batch-executor.ts
│       └── resource-monitor.ts
├── build/                           # Compiled JavaScript
├── docs/                            # Feature documentation
├── test/                            # Test files
├── README.md                        # Main documentation
├── package.json                     # Dependencies
└── tsconfig.json                    # TypeScript config

Limitations

• 30-second default timeout for synchronous commands (configurable, max 10 minutes)
• macOS only (uses /bin/zsh)
• Commands run with the permissions of the user running Claude Desktop
• Sudo commands require password input (unless passwordless sudo is configured)
• Output buffer limited to 300 lines per process (older output is discarded)

Troubleshooting

Common Issues

1. "Session not found" error

   • Ensure you're using the correct session name
   • Check if the session was closed
   • Use list_shell_sessions to see active sessions

2. Command timeout

   • Increase timeout for commands
   • Default is 30 seconds, max recommended is 600000 (10 minutes)
   • Use run_background for processes that need to run longer

3. Permission denied

   • Commands run with the permissions of the user running Claude Desktop
   • Sudo commands require interactive password input (unless passwordless sudo is configured)
   • Ensure the user has necessary permissions for the commands being run

4. Environment variables not working

   • Variables are session-specific
   • Use set_env before running commands that need them
   • Check with get_env to verify

5. "Maximum process limit reached"

   • Check running processes with list_processes
   • Kill unnecessary processes with kill_process
   • Close sessions to free their processes

6. Process output truncated

   • CircularBuffer stores only last 300 lines
   • Use from_line parameter to track output position
   • Consider writing output to files for permanent storage

7. Orphaned processes after server restart

   • Use list_processes to check for orphaned processes (marked with WARNING)
   • Use cleanup_orphans to manage them:
     • cleanup_orphans() - Interactive mode shows orphans and suggestions
     • cleanup_orphans({ mode: "list" }) - Just list orphans
     • cleanup_orphans({ mode: "kill" }) - Kill orphans
   • Individual orphans can be killed with kill_process

8. Server crashes with bash commands (Fixed)

   • Previously, bash -c commands with scripts would crash the server
   • This has been fixed by detecting bash commands and preventing double shell interpretation
   • Commands like bash -c "while true; do echo test; done" work

9. Server crashes when killing processes (Fixed)

   • Previously, killing background processes would crash the server with unhandled promise rejection
   • This has been fixed by adding error handling for process termination
   • The server remains stable when processes are killed with SIGTERM or SIGKILL

10. Tool naming conflicts

    • If you have iterm-mcp installed, use the correct tool names:
      • Use create_shell_session (not create_session)
      • Use list_shell_sessions (not list_sessions)
    • These were renamed to avoid conflicts

Testing

The project maintains comprehensive test coverage with 712+ tests across 41 test suites.

Test Status

• Pass Rate: 100% [PASSED]
• Code Coverage: 60.62%
• Test Execution: ~32 seconds

Running Tests

# Run all tests
npm test

# Run with coverage report
npm test -- --coverage

# Run in watch mode
npm test -- --watch

# Run specific test file
npm test -- src/ai-cache.test.ts

Documentation

• - Comprehensive testing documentation
• - Current test metrics and coverage
• - Future testing plans

Development

Build Commands

# Install dependencies
npm install

# Build TypeScript
npm run build

# Start server (for testing)
npm start

# Development mode (if configured)
npm run dev

Roadmap

• Process groups and job control
• Command aliases and templates
• Shell detection (bash, fish, etc.)
• Process CPU/memory monitoring

Contributing

Contributions are welcome! Please submit pull requests or issues on GitHub.

Changelog

See for version history.

License

ISC