The file size exceeds the limit and will be skipped Error with copilot agent

Question

The file size exceeds the limit and will be skipped Error with copilot agent

Albert Cooper 0

I have an agent that should be reviewing documents for users and giving feedback on what needs to be adjusted before final submission but all of a sudden copilot has started giving me the following error.

The file size exceeds the limit and will be skipped. The maximum file size for images is 16 MB and for text files is 16 MB. Error code: FileValidationError.

Even when i save the file to sharepoint and copy the link and paste it in the agent it gives me the same error.

I checked the settings and the setting that limits the attachment to 16 mb is disabled as well as the Code interpreter.

I checked the documentation and it says that copilots file size limit is 512mb so I'm not sure why this error is coming up. I can run an automation that once a file is uploaded to a SharePoint site it will call the agent and run the review but this limits the users interaction with the agent and getting or detailed feedback.

can someone help me identify why this is occurring and how to resolve this issue.

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2 answers

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Answer 1

Sayali-MSFT 6,476 Microsoft External Staff Moderator

Hello Albert Cooper,
Based on the error, it sounds like the file is being processed through the chat attachment pipeline rather than being accessed as a knowledge source. The FileValidationError and the reported 16 MB limit suggest the file is failing validation before the agent can review it, even though other Copilot scenarios may support larger file sizes. Could you confirm the file type (PDF, DOCX, PPTX, etc.), its actual size, and whether the issue occurs with all files or only specific ones?

It would also be helpful to know whether the file is being uploaded directly in chat, accessed through a SharePoint link, or retrieved from a SharePoint library configured as a knowledge source. If the same error occurs when using a SharePoint link, the service may still be attempting to ingest the document through the attachment-processing path rather than retrieving it from SharePoint. If this previously worked and no configuration changes were made, it could indicate a recent platform regression. Capturing a correlation ID, conversation ID, sample file details, and whether the issue reproduces in both the test and published experiences would help determine for further investigation.

Albert Cooper 0 Reputation points

2026-08-27T05:13:55.3733333+00:00

Hi Thank you for the reply.

The file is being sent through the copilot app in chat form. I cant add these files as a knowledge source they are user generated files that need to be checked to make sure they match our internal guidelines. I can setup a power automate flow that allows a user to put the document in to a sharepoint library and then it will call the agent to check the file. The issue with this is that the user can not follow up with the agent on any suggestions for the fixes. Like give me citations, suggest correction text, or anything else like that.

It does work with smaller files that are smaller than 16mb. If there is a limit of 16mb limit for directly working with the agent that seems like a pretty low limit for modern files.

I also tried uploading the files to sharepoint and copying the file link and using that but that also failed. With HTTPS:// added to the link it gives the same error. When I remove it it works but its not the file that I had copied the link from...
Sayali-MSFT 6,476 Reputation points Microsoft External Staff Moderator

2026-09-10T09:45:23.5733333+00:00

Hello Albert Cooper •,
Thanks for clarifying the scenario. Since these are user-generated documents that need to be reviewed dynamically during the conversation, adding them as a permanent knowledge source wouldn’t really fit the requirement.

For agents using the standard harness, Microsoft currently documents a 15 MB limit per file for files uploaded by users during chat. So files above this size can be skipped even though larger files are supported when configured as agent knowledge sources.

Using SharePoint + Power Automate can work around the initial processing, but as you mentioned, it changes the experience because the user needs an ongoing conversation about that specific document, for example asking for citations, suggested corrections, or clarification.

So for this use case, I don't see a supported way in the standard harness to increase the per-chat file upload limit. If handling documents larger than 15 MB directly in an interactive conversation is a requirement, I would recommend raising this as a product limitation/feature request with Microsoft rather than treating it as a configuration issue.

Also, modifying the SharePoint URL by removing https:// isn't a reliable workaround, since the agent may interpret the resulting text differently rather than actually retrieving the intended file.
Reference:
1.https://learn.microsoft.com/en-us/microsoft-copilot-studio/image-input-analysis
2.https://learn.microsoft.com/en-us/microsoft-copilot-studio/requirements-quotas
3.https://learn.microsoft.com/en-us/microsoft-copilot-studio/agents-experience/attachments-overview

Answer 2

After some additional investigation, I found documentation that may explain the behavior.

The agent is configured with File** processing **capabilities enabled. The official documentation for file uploads and image/file analysis states that uploaded files used during conversations are subject to file processing limits. The configuration page explicitly states:

"Uploads are limited to 15 MB."

Documentation: Analyze images and files in Microsoft Copilot Studio

In my environment, the agent returns the following error:

"The maximum file size for images is 16 MB and for text files is 16 MB. Error code: FileValidationError."

The 15 MB limit shown in the agent configuration is very close to the 16 MB validation error returned by the runtime, which suggests the failure is likely occurring within the file-processing capability used by the chat experience rather than in the underlying knowledge source or storage layer. [learn.microsoft.com]

It's also worth noting that other Copilot Studio documentation references larger limits (for example, 512 MB for certain file upload/knowledge scenarios), which may refer to a different upload path than conversational file processing.

Based on these findings, the observed behavior appears consistent with the file processing feature limit rather than a SharePoint, OneDrive, or Teams file storage limit.

Could Microsoft confirm whether the 15 MB file-processing limit documented in Copilot Studio is the expected limit for files uploaded to agents through Microsoft Teams and Microsoft 365 Copilot Chat?