Windows: every tool call opens a new visible PowerShell/cmd window #7895

What happens

On Windows, the desktop app opens a new PowerShell or cmd window each time the agent makes a tool call that runs a shell command. A normal agent run leaves a pile of console windows popping up and stealing focus.

Why

The desktop app is a GUI process. When a GUI process starts a console program (powershell.exe, cmd.exe, npx.cmd, etc.) with std::process::Command, Windows gives the child its own visible console window unless the CREATE_NO_WINDOW creation flag is set. The shell tool (and likely stdio MCP server launches and any other spawned helpers) doesn't seem to set it.

macOS and Linux don't have this behavior, which is probably why it hasn't shown up there.

Fix

Set the flag on every Command spawned on Windows:

#[cfg(windows)]
{
    use std::os::windows::process::CommandExt;
    cmd.creation_flags(0x08000000); // CREATE_NO_WINDOW
}

For tokio::process::Command, the same creation_flags method is available on Windows.

A shared helper that builds every child process would catch all spawn sites at once (shell tool, MCP stdio servers, git, ripgrep, etc.).

Workaround for now

Running the terminal/headless build from an existing terminal avoids it, since children inherit that console. Docker sandbox mode or WSL also avoids it.

Related

#4705 (Windows shell tool defaulting to bash)