Unable to add Anthropic (Claude models) from Azure in GitHub Copilot (Visual Studio)

[akilesh1102]

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Hey folks!

I've deployed claude-opus-4-6 model in Azure Foundry and added in GitHub copilot. While I'm trying to use, facing an "Unknown mode" error even though everything is accurate. I did the same for OpenAI model, and it worked. From the logs, I can see that it still uses OpenAI APIs and endpoints to make a request. Not sure whether this is a bug.

OUTPUT:

[CopilotSessionProvider Information] Begin sending message (ConversationId:58fbcf80-6d31-47b2-9acc-3482eca512d9, CorrelationId:4def588d-23de-4b7b-95a8-a572160a25b4, MessageId: 8e73c0b9-93f4-4301-a7b1-47ef745e71e8)
[CopilotSessionProvider Information] Request content: "Explain the code"
[Conversations Information] Copilot auth status: OK. Copilot badge status: Active
[Conversations Information] [CopilotClient] Using Azure Foundry endpoint: **https://foundry-github-copilot.services.ai.azure.com/openai/v1**
[Conversations Information] [CopilotClient] Sending chat completions to claude-opus-4-6 with 4 messages.
[Conversations Information] [CopilotClient] ===========

As you can see, while adding even though If I mention the anthropic endpoint, it still uses the OpenAI's one by default.

**Unknown model: claude-opus-4-6
   at OpenAI.ClientPipelineExtensions.ProcessMessageAsync(ClientPipeline pipeline, PipelineMessage message, RequestOptions options)
   at OpenAI.Chat.ChatClient.CompleteChatAsync(BinaryContent content, RequestOptions options)
   at OpenAI.Chat.ChatClient.<>c__DisplayClass17_0.<<CompleteChatStreamingAsync>b__0>d.MoveNext()**

Kindly let me know if there are any other workaround to use models apart from OpenAI. Thanks in advance.

[madebymustafa]

It looks like the Unknown model error happens because GitHub Copilot no longer supports or routes requests to that specific Anthropic model right now. GitHub has been updating and deprecating older models in Copilot, and as of recent changes some Anthropic options can’t be used directly the way they were before.

What you can try instead:

1. Pick a supported model in the Copilot model selector (like the newer Claude versions or GPT-5 series) because deprecated/removed models will cause Unknown model errors.
2. Check your Copilot settings at github.com/settings/copilot/features to confirm the models you want are enabled.
3. Make sure your extension and VS Code are up to date, because sometimes model lists don’t update if you’re on an old version.
4. If that model is important for your workflow, raise feedback or a feature request so GitHub can clarify availability.

Hope this helps!

[akilesh1102]

Thanks a lot! I'll try the mentioned steps.