Saving a Model Generated File in SharePoint - New Copilot Studio

Hi everyone, 

I have spent the last two days trying to solve a problem that to me should be a straightforward functionality. 

I have an agent I made which generates Word file reports. The agent is Cluade Opus 4.8 and it generates the file wonderfully as per my brand guidelines. The document in not a simple content file. Rather these documents can get complex based on the user requirement. 

Currently the document generates fine and the user gets a popup to download the file. I however need the file to be saved in our share SharePoint library. 

I created a workflow tool that accepts a file input and then saves it to SharePoint, however when I tried to configure this tool in the agent, the file input parameter was not showing. I then tried to set up a workflow which accepts a url, but the agent cannot seem to access any url or pass it to my workflow. 

Using a create file tool within the agent and having the agent fill in the file name and content parameters was slow, and the agent was actually attempting to rewrite the file byte-by-byte which lead to the file being re-created and is not scalable for large files.

Based on the agent, this is how the file is currently saved:

"The file is saved inside my sandboxed container at:

/app/created/Sample_Report.docx

/app/created/ is a special output directory: any file I place there is automatically packaged by the platform and returned to you as the chat attachment (the Sample_Report.docx chip you see).

This is a private, ephemeral location inside my container — it is not a shared network path, and it is not the SharePoint library. Neither you nor the SharePoint tool can reach /app/created/ directly; the platform's attachment mechanism is the only bridge out of it, and as we established, that bridge delivers a direct download rather than a hosted HTTPS URL.

So to be precise: the file exists only (a) here in my container at /app/created/Sample_Report.docx, and (b) as the downloadable attachment the platform generated from it. It has not been saved to SharePoint."

I need this functionality working as I will have several automations flows around report generation so no human will be available to download the file from within Copilot. 

Note: I cannot use the old copilot studio as the file generation capabilities are not on par with the new copilot studio experience. The same agent model does not output files, and the create word file node does not output files at the depth and formatting complexity I require.

Can anyone please help with a reliable way to get the file save in SharePoint from the New Copilot Studio experience?

I'm at my wits end here.