feat: add configurable default shell for Windows users

[Br1an67]

Related Issue

Resolve #1274

Description

Currently, kimi-cli hardcodes powershell.exe as the only shell on Windows (in environment.py lines 33-35). Users who prefer pwsh (PowerShell 7), cmd.exe, Git Bash, or WSL bash have no way to override this.

This PR adds a default_shell configuration option so Windows users can choose their preferred shell.

Changes

• config.py: Added default_shell: str field (empty string = auto-detect, preserving current behavior)
• environment.py:
  • Environment.detect() now accepts an optional default_shell keyword argument
  • Added _resolve_shell() helper that uses shutil.which() to locate the binary and maps common shell names to friendly display names
  • Widened shell_name type from Literal["bash", "sh", "Windows PowerShell"] to str to support arbitrary shells
• agent.py: Passes config.default_shell to Environment.detect() in Runtime.create()
• tools/shell/__init__.py:
  • Added _is_cmd flag to handle cmd.exe argument syntax (/c instead of -c)
  • Recognizes both Windows PowerShell and PowerShell (pwsh) as PowerShell variants
• Tests: Added test cases for custom shell override and empty fallback

Usage

# ~/.config/kimi-cli/config.toml
default_shell = "pwsh"        # PowerShell 7
# default_shell = "cmd.exe"   # Command Prompt
# default_shell = "bash"      # Git Bash / WSL

When default_shell is empty (default), behavior is unchanged — PowerShell on Windows, bash/sh on Unix.

Checklist

• I have read the CONTRIBUTING document.
• I have linked the related issue, if any.
• I have added tests that prove my fix is effective or that my feature works.
• I have run make gen-changelog to update the changelog.
• I have run make gen-docs to update the user documentation.

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[devin-ai-integration]

Devin Review found 1 potential issue.

View 4 additional findings in Devin Review.

[devin-ai-integration]

🔴 Background tasks for cmd.exe use wrong shell_name and get incorrect -c flag instead of /c

In _run_in_background, the shell_name passed to create_bash_task is a binary choice: "Windows PowerShell" if powershell, else "bash". When the user configures cmd.exe as their default shell (self._is_cmd = True, self._is_powershell = False), shell_name is set to "bash". The background worker at src/kimi_cli/background/worker.py:136-140 then constructs args as (spec.shell_path, "-c", spec.command) since shell_name != "Windows PowerShell". But cmd.exe requires /c, not -c, so all background tasks will fail to execute when cmd.exe is the shell. The foreground path correctly handles this in _shell_args (line 230-231), but the background path was not updated to account for the new _is_cmd case.

(Refers to line 153)

Prompt for agents

The shell_name passed to create_bash_task at src/kimi_cli/tools/shell/__init__.py:153 needs to propagate the actual shell type (including cmd) rather than a binary PowerShell-or-bash choice. Change line 153 to pass the actual shell_name, e.g. using environment.shell_name stored as self._shell_name, or a computed value that accounts for self._is_cmd. For example:

  shell_name = "Windows PowerShell" if self._is_powershell else ("cmd" if self._is_cmd else "bash")

Additionally, the background worker at src/kimi_cli/background/worker.py:136-140 only handles two cases (PowerShell and everything else with -c). It needs a third branch for cmd that uses /c:

  if spec.shell_name == "Windows PowerShell":
      args = (spec.shell_path, "-command", spec.command)
  elif spec.shell_name == "cmd":
      args = (spec.shell_path, "/c", spec.command)
  else:
      args = (spec.shell_path, "-c", spec.command)

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