Unable To Resolve Chat Model with Family GPT-4.1 | Easy Fix

This error typically appears in GitHub Copilot (inside VS Code or Visual Studio) when the extension tries to load the “GPT-4.1” model but fails to connect to it.

Since GPT-4.1 (released April 2025) is now the default coding model for many Copilot plans, this error usually means your local extension is out of sync with your account permissions or network access.

Here is how to fix it:

1. Reset the “Preferred Model” Setting (Most Likely Fix)

Your VS Code settings might be forcing a specific model family that isn’t currently available to your session.

1. Open VS Code Settings (Ctrl + , or Cmd + ,).

2. Search for copilot.chat.

3. Look for a setting like “Preferred Model” or check your settings.json file for this line:

   JSON

   "github.copilot.chat.preferredModelFamily": "gpt-4.1"
   

4. Delete this line entirely or change it to "default". This forces Copilot to auto-negotiate the best available model (usually GPT-4o or GPT-4.1 Mini) instead of failing on a hard-coded request.

Also Read : BandLab HTTP Error 503 | Service Unavailable

2. Update the GitHub Copilot Extension

If your extension is outdated, it may not know how to handshake with the current GPT-4.1 endpoints.

1. Go to the Extensions tab in VS Code (Ctrl+Shift+X).

2. Search for GitHub Copilot and GitHub Copilot Chat.

3. If an Update button is visible, click it.

4. Reload VS Code (close and reopen entirely) after updating.

3. Check for Network/VPN Blocks

This error often happens if you are on a corporate VPN (like Zscaler) that is inspecting SSL traffic. The “handshake” to the specific GPT-4.1 model family fails because the security certificate is intercepted.

• Test: Disconnect from your VPN and try sending a message to Copilot. If it works, your IT network is blocking the new model route.

4. Sign Out and Sign Back In

Sometimes your authentication token expires, especially if your organization recently changed model policies (e.g., switching from GPT-4o to GPT-4.1).

1. Click the Profile icon (bottom left of VS Code).

2. Select Sign out of GitHub.

3. Restart VS Code.

4. Sign back in when prompted.

Why is this happening?

GPT-4.1 is the specialized “coding-focused” model released in 2025. If you are on an Enterprise plan, your admin might have restricted access to specific model families, or your local machine is requesting a “Preview” version of the model that has been moved or renamed on the server side.