Rate limiting: Copilot Models are silently changed leading to less reliable results

[cyconx]

🏷️ Discussion Type

Bug

💬 Feature/Topic Area

Copilot in GitHub

Body

I have been trying to work around the P1 Rate limiting Incident. I found that choosing different models would allow the AI to respond without being impacted by the rate limiting bug.

However, I noticed the results were strange and not at all of the quality I would expect. I then noticed the following in the logs:

[Conversations Warning] [CopilotClient] Failed to resolve Copilot model for response: 'gpt-5.4-2026-03-05'. Error: Microsoft.VisualStudio.Copilot.Diagnostics.Exceptions.CopilotApiException: The requested model is not supported.
at Microsoft.VisualStudio.Copilot.Diagnostics.DiagnosticExceptionHelper.ThrowCopilotApiException(String errorContent, HttpResponseMessage response) in D:\dbs\el\ddvsm\src\Copilot\src\Copilot.Core\Diagnostics\DiagnosticExceptionHelper.cs:line 224
at Microsoft.VisualStudio.Conversations.CopilotClient.CopilotAPIClient.GetModelAsync(String id, String userCopilotSku, CancellationToken cancellationToken) in D:\dbs\el\ddvsm\src\Copilot\src\CopilotClient\CopilotAPIClient.cs:line 1424
at Microsoft.VisualStudio.Conversations.CopilotClient.CopilotAPIClient.ResolveResponseModelAsync(String responseModelName, CopilotModel requestModel, CancellationToken cancellationToken) in D:\dbs\el\ddvsm\src\Copilot\src\CopilotClient\CopilotAPIClient.cs:line 281

What this means is that a much less capable model is automatically chosen for the job. The result is garbage and you are left scratching your head wondering why. (Yes, of course you are still being charged for the activity, but the wasted effort is far more expensive)

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