How to upload xlsx files with over than 500 KB to use AI prompt

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Posted on by gbatistaa

Hi everyone,

I’m running into an issue while trying to convert Excel (.xlsx) files into XML using Copilot Studio and Power Automate.

The flow works fine with small files, but when I try with a larger file (around 2,642 KB), the process fails at the step where the content is passed to the AI Prompt in Copilot Studio. The error says the file is too large and the AI can’t process the conversion.

What I’ve tried so far:

Using the standard Excel connector in Power Automate to read the data.
Passing the content directly to the AI Prompt so it can generate the XML output.
Testing with smaller files, which worked successfully.

The challenge:

I need the process to work with larger files as well.
I’d prefer to keep the conversion step handled by the AI Prompt in Copilot Studio, but I’m open to alternatives (e.g., splitting the file, using another connector, or extracting the data with Graph API before sending it to the prompt).

My questions:

Is there any recommended way to handle this file size limitation?

Are there best practices for using AI Prompt with large files, or should I follow a different approach to perform the Excel-to-XML conversion in Power Automate?

Thanks in advance for any guidance or references from those who may have faced a similar challenge!

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Romain The Low-Code... 2,564 Super User 2026 Season 1 on at

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Hello,

At the moment file in the chat windows of copilot studio are not supposed to be used as an upload solution. The contexte of the "messsage" is very small in size and if you open the Excel. No workarround, it's hard code limitation inside the chatbox.

What you can do : Drop in sharepoint library and start from here (copilot studio autonomous agent or power automate)

(Or start from mail, forms, workflow, one drive, power apps app, etc)

From here you can use AI Builder Prompt from power automate with bigger file (default is GPT 4.1 so it work very well :) )

At the moment if you want to start you'r process from the chat windows : no workaround until Microsoft change this (lot of demand since lot of use case involve document throught chat)

Sorry it's not a resolution, it's the situation at the moment :-)

Hope this helped you, if the case don't forget the little box to validate answer, it help a lot the community :)

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gbatistaa 6 on at

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Recently, I tried applying the previously mentioned solution; however, I was not fully successful.
Currently, I have a Power Automate flow configured to trigger whenever a new file is created in OneDrive for Business, since the agent developed in Copilot Studio will eventually be migrated to Microsoft Teams. In the corporate environment where I work, whenever an attachment is sent in a Teams conversation, it is automatically stored in OneDrive, in the Microsoft Teams Chat Files folder (or equivalent).

The problem occurs after this step. I managed to extract the data from the Excel file by converting Base64 to string, and then performed some additional processing to remove unwanted characters. However, when sending this string to the AI Prompt connector, I faced limitations related to the number of tokens.

In this context, I would like to know:

- Could a direct HTTP call to the OpenAI API, instead of using the AI Prompt, overcome this limitation?
- Or would it be more advisable to adopt an alternative approach for processing Excel files in order to avoid this issue?

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