The fact that the exact same image works in the Copilot Studio test pane but not when the agent is used through Microsoft 365 is the key clue here.
I would first separate file upload being enabled from image understanding being supported in the channel. Enabling file uploads in Copilot Studio doesn't necessarily guarantee identical file/image behavior across every published channel.
For Microsoft 365 Copilot, I'd check the following:
- Test with a new/simple image — preferably a small JPG or PNG with no unusual metadata.
- Confirm the agent is published after enabling file uploads and that the Microsoft 365 Copilot channel is using the latest published version.
- Test the same image in:
-
Make the first prompt something explicit such as:
"Describe the image I just uploaded."
If it works in Studio but consistently fails in Microsoft 365 with a simple JPG/PNG, I would not start changing the prompt or knowledge sources. That points much more strongly toward a channel/file-input limitation or current ingestion issue.
Microsoft's current documentation does support image file input for agents, but the supported experience depends on the channel and how the file is being supplied to the conversation. The documentation also distinguishes between files uploaded directly by users and files used as knowledge sources.
Another thing worth checking is whether the agent is actually receiving the attachment. If the response behaves as though no image was uploaded at all, that's different from the model being unable to interpret the image. In that case I'd focus on the Microsoft 365 channel/file-handling path rather than the vision model.
I'd also avoid converting the image to a knowledge source just to work around this. A user-uploaded image and an image stored as a knowledge source are two different scenarios.
If the issue reproduces with a brand-new published agent containing only file uploads + a simple image question, I'd capture:
- Copilot Studio environment ID
- Agent ID
- Microsoft 365 Copilot channel
- exact Microsoft 365 client/version
- image format and size
- whether the attachment appears in the conversation
- whether Teams behaves the same way
and raise it with Microsoft as a channel-specific image/file input issue, because the Studio test pane already proves that the agent itself can process the image.
One particularly useful test would be to compare Microsoft 365 Copilot vs Teams with the same published agent. If both published channels fail while the Studio test works, that's much stronger evidence of a publishing/channel-side issue.
