How to Configure Shell Settings with defaultShell in DesktopCommanderMCP

DesktopCommanderMCP uses the defaultShell configuration field to determine which shell binary executes commands, falling back to system environment variables if unset.

DesktopCommanderMCP provides a flexible configuration system that allows you to specify which shell binary handles command execution through the defaultShell setting. This configuration is managed by the Config Manager and stored in a persistent JSON file. You can modify this setting either through the Settings UI or programmatically via the Config Manager API to customize your command environment.

Understanding the defaultShell Configuration Field

The defaultShell field is formally defined in src/config-field-definitions.ts at lines 21-25, where it is typed as a string and annotated with user-friendly metadata. This definition tells the application that any value stored here should be interpreted as a file path to a shell executable, such as /bin/bash, /bin/zsh, cmd.exe, or pwsh.

When the Settings panel renders configuration options, it references these field definitions from CONFIG_FIELD_DEFINITIONS to display appropriate labels and descriptions for the shell selection interface.

System Detection and Fallback Behavior

If you never explicitly set a default shell, DesktopCommanderMCP automatically detects one based on your operating system. The detection logic, implemented in uninstall-claude-server.js at lines 144-151, inspects process.env.SHELL on Unix systems and process.env.ComSpec on Windows to determine the appropriate fallback binary.

This ensures that new REPL sessions and command executions always spawn a valid shell even without explicit configuration, using the system's preferred command interpreter as a default.

Programmatically Configuring the Default Shell

You can interact with the defaultShell setting directly through the Config Manager API exposed in src/config-manager.ts. The manager provides getter and setter methods that read from and write to the underlying config.json file.

Setting the Default Shell via the Config Manager

To change the shell programmatically, import the configManager and call setValue() with the key 'defaultShell':

import { configManager } from './config-manager';

// Switch to Zsh for all new sessions
await configManager.setValue('defaultShell', '/bin/zsh');

// Verify the change
const shell = await configManager.getValue('defaultShell');
console.log(`Current default shell: ${shell}`);

Reading the Default Shell for New Sessions

When spawning new processes, retrieve the configured shell using getValue() and provide a fallback if the configuration is empty:

const { spawn } = require('child_process');
const { configManager } = require('./config-manager');

async function startShell() {
  const shell = await configManager.getValue('defaultShell') || '/bin/sh';
  const child = spawn(shell, [], { stdio: 'inherit' });
  child.on('exit', code => console.log(`Shell exited with code ${code}`));
}

startShell();

Summary

• The defaultShell field is defined in src/config-field-definitions.ts as a string type that accepts paths to shell executables like /bin/bash or pwsh.
• DesktopCommanderMCP falls back to system environment variables (process.env.SHELL on Unix or process.env.ComSpec on Windows) when no explicit shell is configured, as implemented in uninstall-claude-server.js.
• Use configManager.setValue('defaultShell', path) to programmatically update settings and configManager.getValue('defaultShell') to retrieve the current configuration.
• Changes persist to config.json and apply immediately to new command sessions, while existing REPL sessions remain unaffected.

Frequently Asked Questions

Where is the defaultShell setting stored in DesktopCommanderMCP?

The defaultShell value is stored in the config.json file managed by the Config Manager in src/config-manager.ts. The field definition in src/config-field-definitions.ts provides the schema that validates this entry as a string representing a shell path.

What happens if I don't configure a defaultShell?

If the defaultShell configuration is empty, DesktopCommanderMCP automatically detects your system shell by checking process.env.SHELL on Unix or process.env.ComSpec on Windows, as defined in uninstall-claude-server.js at lines 144-151. This ensures commands execute using your system's default command interpreter.

Can I use PowerShell or CMD as the defaultShell on Windows?

Yes. The defaultShell field accepts any valid shell path, including Windows executables like cmd.exe or pwsh. Simply set the value to the full path of your preferred Windows shell executable using configManager.setValue('defaultShell', 'pwsh').

Do changes to defaultShell affect existing REPL sessions?

No. Changes to the defaultShell configuration only apply to new shell sessions spawned after the configuration is saved. Existing REPL sessions and running processes retain the shell binary that was active when they started.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}