gpt-6-luna does not support web_search in Microsoft Foundry Responses API, while gpt-6-sol does

Question

gpt-6-luna does not support web_search in Microsoft Foundry Responses API, while gpt-6-sol does

Søren Sparsø 0

Hi,

I am testing the Microsoft Foundry Responses API using the following project endpoint:

POST https://FOUNDRY_RESOURCE_NAME.services.ai.azure.com/api/projects/PROJECT_NAME/openai/v1/responses

The following request works correctly when using gpt-6-sol:

{
  "model": "gpt-6-sol",
  "input": "Search the web and tell me the current Microsoft Foundry homepage title.",
  "tools": [
    {
      "type": "web_search"
    }
  ],
  "tool_choice": "required"
}

However, when I send the same request using gpt-6-luna:

{
  "model": "gpt-6-luna",
  "input": "Search the web and tell me the current Microsoft Foundry homepage title.",
  "tools": [
    {
      "type": "web_search"
    }
  ],
  "tool_choice": "required"
}

I receive the following error:

{
  "error": {
    "message": "Tool 'web_search_preview' is not supported with gpt-6-luna-2026-09-22.",
    "type": "invalid_request_error",
    "param": "tools",
    "code": null,
    "request_id": "102ed4b84867293564bf24b783a89352"
  }
}

Both deployments are in the same Microsoft Foundry resource/project, and the only change between the two requests is the model/deployment name.

My questions are:

Is web_search officially supported with gpt-6-luna-2026-09-22 in Microsoft Foundry?
If not, is this a documented limitation?
If it is supposed to be supported, is the error above a known issue?
Why does the error refer to web_search_preview when the request explicitly uses "type": "web_search"?

The same request works as expected with gpt-6-sol, so this appears to be specific to gpt-6-luna.

Any clarification on the intended capability matrix for GPT-6 Luna versus GPT-6 Sol would be appreciated.

Sai Kiran Mudavath 175 Reputation points Microsoft External Staff Moderator

2026-10-02T04:37:54.09+00:00
Hi @Søren Sparsø ,

Thank you for providing the detailed request, error message, and the comparison with gpt-6-sol.

I reviewed the current Microsoft Foundry documentation for the Responses API and Web Search.

Is web_search supported with gpt-6-luna-2026-09-22?

The current documentation lists gpt-6-luna version 2026-09-22 as a supported model for the Responses API. Microsoft's Web Search documentation also states that Web Search is available through the web_search tool in the Responses API and is supported with GPT-4 models and later.

Is this a documented limitation of GPT-6 Luna?

I could not find any current Microsoft documentation indicating that gpt-6-luna-2026-09-22 does not support the web_search tool. The Foundry Responses API documentation lists web_search as a built-in tool, and Microsoft provides examples of using Web Search through the Foundry project endpoint.

Is this error a known issue?

I could not find any Microsoft documentation that identifies this exact error as a known issue. Based on the available documentation, the behavior appears inconsistent with the documented Web Search tool usage.

Why does the error refer to web_search_preview when the request specifies web_search?

Your request explicitly specifies:

{ "tools": [ { "type": "web_search" } ] }

However, the service returns:

Tool 'web_search_preview' is not supported with gpt-6-luna-2026-09-22.

Microsoft currently documents web_search and web_search_preview as separate tool types, with web_search being the recommended option. The public documentation does not explain why a request specifying web_search would return an error referencing web_search_preview. Therefore, I would avoid drawing conclusions about any internal service behavior based solely on the error message.

Since the same request succeeds with gpt-6-sol in the same Foundry resource and project, while the gpt-6-luna-2026-09-22 deployment returns the web_search_preview error, the behavior appears to be specific to the Luna deployment or its interaction with the Web Search tool rather than a general Web Search access issue.

Because the current documentation does not describe this behavior as a known issue, the request ID (x-request-id/correlation ID) from the failed request would be useful for further investigation if the issue continues.

I hope this helps clarify the currently documented behavior and the discrepancy in the returned error message.
Sai Kiran Mudavath 175 Reputation points Microsoft External Staff Moderator

2026-10-02T06:55:47.13+00:00

Hi @Søren Sparsø

We have reached out to you via private message for further assistance and to collect the details required to investigate the affected resource and failed indexing operations.

Thank You!

1 answer

Your answer

Sai Kiran Mudavath 175 Reputation points Microsoft External Staff Moderator

2026-10-02T06:55:47.13+00:00

Hi @Søren Sparsø

We have reached out to you via private message for further assistance and to collect the details required to investigate the affected resource and failed indexing operations.

Thank You!

Answer 1

Søren Sparsø 0

Here's an example of a failed request id:

{
    "error": {
        "message": "Tool 'web_search_preview' is not supported with gpt-6-luna-2026-09-22.",
        "type": "invalid_request_error",
        "param": "tools",
        "code": null,
        "request_id": "102ed4b84867293564bf24b783a89352"
    }
}

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