Authentication fails on WSL despite correct environment and localhost networking

:Copilot setup の背後にある実装と、Vim に "Waiting..." と表示されたままになる認証コールバックから始めます。報告されている Ubuntu、Vim、Node のバージョンを使って WSL 2 上でフローを再現し、localhost テストの詳細をコンテキストとして使用します。ブラウザー認証が完了し、コールバックが Vim に到達し、Copilot が認証済み状態を報告すれば完了です。

The Copilot for Vim extension fails to complete the authentication process on my WSL (Ubuntu 24.04) setup. The authentication is successful in the browser, but the callback to Vim never completes, and Vim remains stuck on the "Waiting..." message.

I have performed this troubleshooting and can confirm the issue is not with my local environment.

Symptom:

Running :Copilot setup provides a code.
Authenticating in a browser (running inside WSL) succeeds with the "Congratulations, you're all set!" message.
Vim remains stuck on "Waiting (could take up to 5 seconds)" and never receives the authentication confirmation.
Troubleshooting Steps Performed:

Plugin Version: The issue occurs on both the latest version and after downgrading to v1.41.0.
WSL-Native Browsers: The issue occurs with multiple browsers installed and running directly within WSL, including:
Firefox (installed via Snap)
Google Chrome (non-Snap Deb version)
Firewall: Confirmed that ufw is not installed or active.
Localhost Networking Test: I have confirmed that basic localhost communication within WSL is working perfectly. A Python http.server can be successfully reached from curl via localhost.
This testing suggests the issue is a bug within the Copilot agent's internal web server or its callback handling mechanism within a WSL environment.

My Environment:

OS: Windows 11
WSL Version: WSL 2
Linux Distribution: Ubuntu 24.04 LTS
Vim Version: 9.1
Node Version (in wsl): 22.16.0
Copilot Status after hang and restart: Copilot: Not authenticated. Invoke :Copilot setup (process then repeats)

(Above is AI generated)