[NingLin Liu (ninglinLiu)]

Motivation & Context

LocalShellTool(shell=r"C:\Windows\...\powershell.exe") and unquoted AGENT_FRAMEWORK_SHELL paths fail on Windows with FileNotFoundError because resolve_shell used shlex.split, which treats \ as an escape and drops every backslash. The PowerShell -Command flag is also missed after the path is mangled.

Description & Review Guide

• What are the major changes?
  • Add _split_shell_override: on win32, non-POSIX shlex that keeps backslashes and only honours "..." quotes; elsewhere keep shlex.split.
  • Use it for both the shell= argument and AGENT_FRAMEWORK_SHELL.
  • Tests cover unquoted Windows paths, env override, and quoted paths with spaces.
• What is the impact of these changes? Windows shell overrides work; POSIX behaviour unchanged.
• What do you want reviewers to focus on? That win32 splitting matches CommandLineToArgvW-style double-quote handling.

Related Issue

Fixes #9819

AI Assistance

• No material AI assistance was used.
• This is an AI-assisted contribution. I reviewed, understood, and verified all submitted content and accept responsibility for it.

AI assistance details: locating the shlex.split win32 escape behaviour, implementing _split_shell_override, and writing the regression tests and this PR description.

Contribution Checklist

• The code builds clean without any errors or warnings
• All unit tests pass, and I have added new tests where possible
• The PR follows the Contribution Guidelines
• This PR links to an agreed issue with no competing open PR, or the Related Issue section documents a trivial-change or repository-automation exception.
• This is not a breaking change.

[Copilot]

🟡 Changes recommended

Windows shell overrides mishandle partially quoted executable paths and quoted option values, while Windows-mocking tests fail on Linux/macOS because basename handling remains POSIX.

2 open issues

• Preserve quoted Windows paths when parsing shell command overrides · New
• Use Windows path handling when testing PowerShell command construction · New

What changed in this PR

This PR addresses #9819 by preserving Windows backslashes in Python LocalShellTool string overrides while keeping POSIX parsing unchanged.

Changes:

• Adds platform-aware splitting for shell= and AGENT_FRAMEWORK_SHELL.
• Adds regression tests for unquoted Windows paths, environment overrides, and quoted paths containing spaces.

File	Description
python/​packages/​tools/​tests/​test_shell_resolve.py	Adds Windows path and PowerShell flag regression tests.
python/​packages/​tools/​agent_framework_tools/​shell/​_resolve.py	Introduces and applies platform-aware shell override parsing.

_{Review effort: Balanced}