gemini-cli - 💡(How to fix) Fix Support customizing execution shell (e.g. to zsh) in Unix-like environments

Description

Currently, in packages/core/src/utils/shell-utils.ts, getShellConfiguration() hardcodes the execution shell to bash for all Unix-like platforms (macOS, Linux):

export function getShellConfiguration(): ShellConfiguration {
  ...
  // Unix-like systems (Linux, macOS)
  return { executable: 'bash', argsPrefix: ['-c'], shell: 'bash' };
}

Because of this hardcoding, the CLI and agent cannot run commands using the user's preferred shell such as zsh or fish.

For macOS users, where zsh is the default system shell, key configurations (e.g., Homebrew paths, custom environment variables, Node version managers) are typically loaded inside ~/.zshrc. Spawning commands via a hardcoded bash environment prevents these settings from being inherited naturally, resulting in commands not being found or execution failures during agent runs.

Proposed Solutions

1. Leverage $SHELL Environment Variable: Detect the current shell from process.env.SHELL first. If it points to an installed system shell (like /bin/zsh), use it to resolve the execution configuration.
2. Add a Configuration Setting: Allow users to specify the preferred shell in settings.json, matching VS Code styles:

   {
     "terminal.integrated.defaultProfile.osx": "zsh"
   }

Client Environment

• OS: macOS (Darwin)