Add hide_cli_window option to suppress console on Windows

[Copilot]

Windows GUI applications show a console window when the SDK auto-starts the CLI subprocess, breaking the user experience for frozen apps.

Changes

• New option: hide_cli_window (bool, default False) in CopilotClientOptions
• Implementation: Uses subprocess.CREATE_NO_WINDOW flag on Windows when enabled
• Scope: Applies to both stdio and TCP transport modes

Implementation

Uses conditional kwargs pattern to avoid passing Windows-specific parameters on other platforms:

popen_kwargs = {"cwd": self.options["cwd"], "env": env}

if sys.platform == "win32" and self.options.get("hide_cli_window", False):
    popen_kwargs["creationflags"] = subprocess.CREATE_NO_WINDOW

self._process = subprocess.Popen(args, **popen_kwargs)

Usage

from copilot import CopilotClient

# For Windows GUI applications
client = CopilotClient({"hide_cli_window": True})

On non-Windows platforms, the option is ignored.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Copilot CLI subprocess opens console window when SDK auto-starts CLI</issue_title>
<issue_description>When using the Python SDK on Windows in a frozen app, a console window pops up and stays open whenever the SDK auto-starts the Copilot CLI server. This happens because the CLI is spawned via subprocess.Popen(...) without CREATE_NO_WINDOW/STARTUPINFO

Relevant lines:
https://github.com/github/copilot-sdk/blob/main/python/copilot/client.py#L927-L935
https://github.com/github/copilot-sdk/blob/main/python/copilot/client.py#L939-L946

The console window is visible and distracts end users. This is especially noticeable in GUI apps that shouldn’t show any terminal windows.

Could you add an option to suppress the window on Windows? For example:

• A client option like hide_cli_window: true, or
• Passing creationflags=subprocess.CREATE_NO_WINDOW / startupinfo when launching the CLI on Windows</issue_description>

<agent_instructions>Review the issue and implement the change.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Copilot CLI subprocess opens console window when SDK auto-starts CLI #305

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