Unable to update the attachment of the agent

Hello Wei,

This appears to be an unexpected update failure rather than a documented limitation. Please try the following workarounds:

1. Open Microsoft 365 Copilot in an InPrivate/Incognito window and edit the agent again.
2. Remove the affected attachment, save the agent without it, reopen the agent, and then add it again.
3. If removal and save also fail, create a copy or new agent and add the same knowledge sources there.
4. For SharePoint content, add the parent folder, document library, or site as one knowledge source instead of attaching individual files.
5. If the agent already has 20 source items, consolidate files under a folder and add that folder as the source. SharePoint agents support up to 20 source items, where a site, library, folder, or file counts as one item.
6. If one particular file fails, try a newly downloaded copy with a shorter filename and a supported extension. Confirm the user can still open the source file.
7. Try the update from another supported desktop browser and temporarily disable browser extensions that modify network traffic.

Please do not delete the original working agent until the replacement has been tested. Also, avoid repeatedly saving the same agent while the error continues.