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

[michou]

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+)