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Error Report – Agent Creation in Copilot Studio (AxiosError 400 / ErrorCode 4003)

Marcelo Lorenz 0 Reputation points
2025-12-09T10:39:54.5366667+00:00

Hello,

I’d like to report a recurring error I’m experiencing when trying to create an agent in Microsoft Copilot Studio.

During the creation process, I receive the following error message:

AxiosError: Request failed with status code 400
ErrorCode: 4003
ErrorMessage: "The request must contain at least one user message with non-empty content."

This error occurs even after filling in all required fields and following the standard creation flow. I’ve already tried the following troubleshooting steps without success:

  • Clearing browser cache and cookies
  • Using incognito/private mode
  • Switching browsers (Chrome, Edge)
  • Restarting session and environment
  • Testing on another device and network

The issue seems related to input validation, where the system fails to recognize the initial user message even when content is provided. I’ve also found similar reports from other users on Microsoft forums, which may indicate a systemic issue or bug in the platform.

If there are any additional instructions, planned fixes, or if you need further technical details (such as correlation IDs), I’m happy to assist.

Thank you in advance for your support.

Best regards,

Marcelo Lorenz

Supervisor – Itajaí, SC

Let me know if you'd like help sending this via Outlook or if you want to attach screenshots or logs.

Microsoft Copilot | Microsoft 365 Copilot | Development

2 answers

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  1. Q&A Assist
    2025-12-09T10:40:12.27+00:00
    AI generated content. This question contains an answer created with AI from Q&A Assist. Learn more

    It seems that you are encountering an AxiosError with code 4003 while trying to create an agent in Microsoft Copilot Studio. The error message indicates that the request must contain at least one user message with non-empty content, which suggests that the system is not recognizing the input you are providing.

    Given your troubleshooting steps, it may be beneficial to check the following:

    • Ensure that the user message you are entering is not only filled out but also meets any specific formatting or content requirements that may not be immediately apparent.
    • Review any recent updates or changes in the Copilot Studio that might affect the agent creation process.
    • If you haven't already, consider reaching out to Microsoft Support for technical issues that can't be resolved locally, as they may have more insights into this specific error code and any potential systemic issues.

    Additionally, joining community forums may provide insights from other users who have faced similar issues and could offer workarounds or solutions.

    If you continue to experience this issue, providing Microsoft with detailed information, including correlation IDs and any relevant timestamps, could assist in their investigation.

    References:

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  2. Karan Shewale 2,385 Reputation points Microsoft External Staff
    2025-12-11T10:03:02.5266667+00:00

    Hi Marcelo Lorenz,

    The AxiosError 400 / ErrorCode 4003 occurs during agent creation in Copilot Studio when the system does not detect a valid initial user message. Even if all fields appear filled, the error usually indicates that the first user message in the agent flow is missing, empty, or incorrectly formatted. To fix this, ensure that the first message contains non-empty content and follows the correct formatting guidelines, including avoiding hidden spaces, line breaks, or unsupported YAML syntax. If you are using a pre-built template, double-check that all required fields are properly completed. Clearing browser cache, using incognito mode, or restarting the session can help if the platform is temporarily caching invalid input. Providing correlation IDs and timestamps when contacting Microsoft Support can also help in diagnosing any underlying platform issues.

    Following these steps typically resolves the error and allows the agent to be created successfully.

    Documents:

    1. https://dori-uw-1.kuma-moon.com/en-us/microsoft-copilot-studio/fundamentals-what-is-copilot-studio
    2. https://dori-uw-1.kuma-moon.com/en-us/microsoft-copilot-studio/nlu-boost-node

    Thank you.

    Karan Shewale.

    If this response resolves your issue, please Accept the answer and, if helpful, click the “Upvote” button. Your feedback helps us improve and assist others more effectively.

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