Cross-tool  .claude/settings.local.json  hooks with shell operators ( || ,  && ) break on Windows PowerShell

Describe the bug

When a repository contains a Claude Code hook config ( .claude/settings.local.json  or  .claude/settings.json ) with a  PreToolUse  hook defined via a single cross-platform  command  string containing POSIX shell operators (e.g.  ... || echo {} ), Copilot CLI fails to execute that hook correctly on Windows, which can block all subsequent tool calls gated by that hook.

Root cause hypothesis:
Claude Code executes these same hook commands via git-bash on Windows, so  || / &&  work there. Copilot CLI's cross-tool compatibility layer, per the hooks reference, reads  .claude/settings*.json  files but runs the single  command  string as the native Windows  powershell  fallback rather than replicating Claude Code's git-bash execution context. This makes any Claude hook authored with POSIX-only shell syntax silently non-functional (and blocking) on Windows.

Affected version

No response

Steps to reproduce the behavior

1. On Windows, in a repo, create  .claude/settings.local.json  with:
   {
   "hooks": {
   "PreToolUse": [
   {
   "matcher": "Bash",
   "hooks": [
   { "type": "command", "command": ""C:\path\to\tool.exe" some-check || echo {}" }
   ]
   }
   ]
   }
   }
2. Launch  copilot  in a native Windows PowerShell (5.1) terminal in that repo.
3. Attempt any shell/Bash tool call.

Expected behavior

Expected behavior:
The hook executes successfully and either allows or blocks the tool call based on its actual logic, consistent with how the same config works under Claude Code.

Actual behavior:
The tool call is blocked.  /env  confirms the hook is loaded ("preToolUse: N hooks, source: repo settings"), but the underlying command fails silently, because  ||  is invalid syntax in Windows PowerShell 5.1 — the shell that Copilot CLI uses to run the hook (per the docs, the  command  field is used as a fallback for both  bash  and  powershell  execution).

Additional context

Windows 11 Enterprise, PowerShell terminal (Windows PowerShell 5.1, not  pwsh  7+)

Tái hiện sự cố với .claude/settings.local.json hoặc .claude/settings.json, một lệnh PreToolUse sử dụng || và Copilot CLI trong Windows PowerShell 5.1. Kiểm tra /env để xác nhận nguồn của hook và quan sát xem lệnh có bị lỗi trong khi gọi công cụ Bash hay không. Hoàn tất khi hook thực thi thành công và cho phép hoặc chặn lệnh gọi công cụ theo kết quả của nó.