BYOK Azure Foundry /responses fails with invalid input type (input[n].type)

[mderazon]

Summary

Using VS Code Copilot Chat BYOK with an Azure Foundry OpenAI-compatible endpoint and explicit /responses path can fail with a request validation error indicating an invalid/missing input[n].type.

Environment

• VS Code: latest stable (repro observed in May 2026)
• Extension: GitHub Copilot Chat (BYOK custom model)
• Provider in chatLanguageModels.json: azure
• Endpoint style: Azure Foundry project OpenAI-compatible endpoint

Config Snippet

{
  "models": {
    "provider": "azure",
    "url": "https://<foundry-host>.services.ai.azure.com/api/projects/<project>/openai/v1/responses",
    "id": "<model-id>",
    "name": "<display-name>",
    "toolCalling": true,
    "vision": false,
    "maxInputTokens": 64000,
    "maxOutputTokens": 8000
  }
}

Steps to Reproduce

1. Configure a BYOK Azure custom model in chatLanguageModels.json with an explicit /responses URL (Foundry project endpoint).
2. Select that model in Copilot Chat.
3. Send a simple prompt (for example: Hello).
4. Observe request failure.

Actual Result

Request fails with 400-like validation response (sanitized):

{
  "error": {
    "message": "Invalid value: ''. Supported values are: 'input_text', 'input_image', 'output_text', 'refusal', 'input_file', 'computer_screenshot', and 'summary_text'.",
    "type": "invalid_request_error",
    "param": "input[1]",
    "code": "invalid_value"
  }
}

Expected Result

The BYOK request payload generated for /responses should be compatible with Azure Foundry OpenAI-compatible Responses API expectations.

Notes

• Using /chat/completions is more reliable in this setup.
• This may be a payload-shape compatibility issue in the BYOK Responses path for Azure Foundry endpoints.

[alexdima]

Thanks for filing this issue! This repository has been archived because the project has moved into the main VS Code repository.

Could you please reopen this issue in the VS Code repository instead?
https://github.com/microsoft/vscode

Thanks for helping us keep issue tracking centralized.