I think it depends on whether you work in a notebook environment or the conversation environment in coPilot M365. The former creates links to downloadable sites, but they don't work, whereas the latter does, apparently.
M365 Copilot-created file placed at unreachable URL: sandbox:/mnt/data
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(307.2, 54%, 39%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EMM%3C/text%3E%3C/svg%3E)
Maria Mingallon
110
Reputation points
We are encountering a recurring issue where Microsoft 365 Copilot creates files that are saved to an unreachable URL: sandbox:/mnt/data. This behavior has been observed in multiple contexts:
- When using M365 Copilot chat
- When interacting with Microsoft Copilot agents via browser app or Teams
- When working within the Notebook experience
This issue prevents users from accessing the generated files, disrupting workflows and causing confusion.
A similar topic was previously raised in the Microsoft Answers forum (https://answers.microsoft.com/en-us/msoffice/forum/all/m365-copilot-created-file-placed-at-unreachable/54cedad9-20fe-4b67-a9e3-11ea0bf1dd60?page=1&messageId=b68870a6-c171-4bc3-a09b-6ebe2533be08), but it has not been successfully addressed by Microsoft so far.
We are raising this again in hopes of receiving a definitive explanation and resolution. Specifically, we would like to understand:
- Why are files being saved to
sandbox:/mnt/data? - Is this expected behavior or a bug?
- What steps can be taken to retrieve or redirect these files to an accessible location?
Thank you for your support.
Microsoft Copilot | Microsoft 365 Copilot | Development
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Gee777 Disciple 70 Reputation points2025-07-08T22:26:02.5766667+00:00 I am also having the same issue, somebody please help!
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Jimbob1986 0 Reputation points2025-07-15T13:39:48.9566667+00:00 any update on this?
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QuickBrownFox 36 Reputation points2025-07-17T22:17:17.09+00:00 I can confirm this happens when chatting with Copilot M365 in a Notebook context, just as @Harrie Boonen wrote. In a "normal" M365 Copilot chat conversation, documents are generated with working hyperlinks and downloadable.
Would like to hear from Microsoft about this issue... -
QuickBrownFox 36 Reputation points
2025-07-17T22:28:42.1566667+00:00 Update: Microsoft has acknowledged the issue and is working on it:
https://admin.cloud.microsoft/?#/servicehealth/:/alerts/CP1116386 -
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Kluge, Christine 0 Reputation points2025-07-24T18:27:57.53+00:00 same issue here
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Mike Conrad 0 Reputation points2025-07-26T00:14:04.88+00:00 An update was due today. This is now impacting all of my chats and custom agents.
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Neal Williams 5 Reputation points2025-07-28T14:53:01.81+00:00 Same issue here
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Rebecca H Meller 0 Reputation points2025-07-30T00:56:46.36+00:00 same issue here
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James Gill 25 Reputation points2025-08-11T19:37:59.9366667+00:00 Opened a ticket with M$ suppport a week or so ago for exactly this issue and they linked me to this answer in their support ticket. So as of 8/11/2025, this is an ongoing issue with no permanent fix. Go figure, Microsoft is perfectly willing to let us buy licenses for and spend $51/mo on a broken product. Criminal stuff here...
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Harrie Boonen 5 Reputation points2025-07-16T14:11:26.6066667+00:00 -
Maria Mingallon 110 Reputation points
2025-07-24T03:36:24.2366667+00:00 Hi Harrie,
Not sure I am understanding you correctly. The issue we have is within a chat that is in the 'Notebook' environment not under the 'Chat' instance only outside 'Notebook'. Have you been able to get downloadable sites/documents from Notebook?
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QuickBrownFox 36 Reputation points
2025-07-24T12:18:48.6533333+00:00 @Maria Mingallon Your understanding is correct. And what you describe is exactly the issue confirmed by Microsoft (see https://admin.cloud.microsoft/?#/servicehealth/:/alerts/CP1116386).
Microsoft's last information:- Juli 2025, 19:17 MESZ We're completing our internal validations and tests for our fix to ensure it addresses the affected declarative agents and Copilot notebooks without introducing any unexpected problems to the service. We're expecting the validations to be completed and a timeline for our fix deployment to be available by our next scheduled update. Next update by: Freitag, 25. Juli 2025 um 20:00 MESZ
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Lemus, Ricardo 0 Reputation points2025-07-31T20:11:48.3366667+00:00 Exactly the same output/behavior - I did request the agent to generate a downloadable link, but no luck either! keep sending the sandbox:/mnt/data
Any workaround that had worked so far? Thanks