How are you handling user-uploaded file attachments in the new Copilot Studio agent experience?

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Posted on by OB-09100801-0

Hi everyone,

I’m testing user-uploaded file attachments in the new Copilot Studio agent experience and looking for practical guidance from the community.

Scenario:

A user attaches a file directly in the chat with a new Copilot Studio agent. I need the agent to pass that file to another component, such as:

- Power Automate / agent flow

- SharePoint or Azure Blob Storage tool

- custom connector / REST API tool

- connected agent

I’ve tried Power Automate, SharePoint/Blob tools, PowerFx, explicit agent instructions, different models, and connected-agent orchestration. So far, it looks like the new agent can maybe read the uploaded file internally, but does not expose the actual file binary/content bytes to tools, flows, or connected agents.

In classic Copilot Studio, there were topic-based patterns like System.Activity.Attachments. In the new agent experience, I haven’t found an equivalent mechanism.

Has anyone found a working way to:

1. access user-uploaded file content in the new agent experience;

2. pass that file to a flow/tool/connected agent;

3. or implement a reliable workaround?

If direct attachment passthrough is not possible, what approach are you using instead — SharePoint staging, Power Apps upload form, Dataverse file column, Azure Blob SAS URL, or passing only fileId/fileUrl/blobPath?

Any practical examples or lessons learned would be very helpful.

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BD-02060115-0 2 on at

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Same issue for me in new agent experience. But in classic one agent was able to pass the excel file to the agent flow and then agent flow create file in sharepoint.

New agent experience, doesn't show the agent flow tool input related to the file

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sannavajjala87 522 Super User 2026 Season 1 on at

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Hi,

You’re not missing anything , what you’re seeing is the current limitation of the new Copilot Studio agent experience.
Right now, when a user uploads a file in chat, the agent can reference or reason over it internally, but the actual file (binary/content bytes) is not exposed to downstream tools like Power Automate, custom connectors, or even connected agents. There isn’t an equivalent to System.Activity.Attachments in the new experience yet, so you can’t directly pick up the file and pass it along.
Because of that, most working patterns today rely on indirection rather than passthrough. The approaches I’ve seen work reliably are:

Pre-upload pattern (recommended): Have users upload files to SharePoint, Blob, or Dataverse first, then pass the file URL/ID into the agent. The agent works with metadata, and your flow/tool retrieves the file directly from the source.

Power Apps front door: Use a simple Power Apps form for file upload and trigger your flow from there. The agent can then operate on the stored file reference.

Link-based handoff: Instead of passing file content, pass a fileUrl, itemId, or blobPath to your tool/flow, which then performs the actual processing.

Custom API pattern: If you control the backend, expose an endpoint that accepts a reference (not the binary), and let the API fetch the file using service credentials.

What doesn’t work reliably today:

Passing file bytes directly to a flow/tool

Accessing attachment content from agent memory/context

Chaining file attachments across connected agents

So in short: direct attachment passthrough isn’t supported yet, and the most stable design is to treat the agent as an orchestrator working with file references, not file payloads.
Hopefully this saves you some time , I went down the same path and ended up standardizing on SharePoint + URL handoff.

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Valantis 6,778 on at

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hi @OB-09100801-0,

There is actually a supported way in the new agent experience, but it requires a specific setup that's easy to miss.

<cite index="47-1">To pass a user file to a Power Automate flow added as a tool, on the tool's Inputs page, set the file parameter using the Custom value option with a Power Fx formula. It does not work using the Dynamically fill with AI option.</cite>

The formula to use:

{ contentBytes: First(System.Activity.Attachments).Content, name: First(System.Activity.Attachments).Name }

For this to work, the agent needs File upload enabled in settings, and the flow must have a File type input (not string).

The System.Activity.Attachments variable is available in the new experience too, it just isn't exposed automatically to tools.

<cite index="47-1">File inputs only work when you set them as a Power Fx formula using the Custom value option on the Tools page.</cite>

mosty many users hit the "contentBytes empty" wall, they're relying on AI to fill the parameter automatically.

Ref: https://learn.microsoft.com/en-us/microsoft-copilot-studio/guidance/pass-files-to-connectors

Best regards,

Valantis ✅ If this helped solve your issue, please Accept as Solution so others can find it quickly.

❤️ If it didn’t fully solve it but was still useful, please click “Yes” on “Was this reply helpful?” or leave a Like :).

🏷️ For follow-ups @Valantis.

📝 https://valantisond365.com/ 💼 LinkedIn ▶️ YouTube

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