File attachments work in Copilot Studio but not after publishing

This is expected in many published Copilot Studio channels today.

The key point is that there are two different attachment experiences in the documentation:

1. Newer attachment/file-input support exists for agents in supported surfaces such as Microsoft Teams, Microsoft 365 Copilot, web chat, and the Copilot Studio test experience.
2. A documented publishing limitation states that, for published agents, users can't send or upload attachments to the chat, and if they do, the agent responds that it can only process text. That limitation is explicitly called out as applying to all channels, including Microsoft Teams and Direct Line, unless the message is sent to a skill that supports attachment processing.

That explains the behavior described:

• In the Copilot Studio test experience, attachments can work.
• After publishing to Teams or Microsoft 365 Copilot, the same agent can behave as though no file was provided because published-channel attachment handling is limited.

Additional channel-specific facts from the documentation:

• File input is supported only on certain channels, including Microsoft Teams, Microsoft 365 Copilot, and the Test your agent panel.
• File input is not supported on SharePoint, voice, or telephony channels.
• If the agent is in a customer managed key (CMK) enabled environment, users can add files, but the agent doesn't process them.
• For Office-style file reading, there are content limitations. For example, Word text in text boxes, shapes, SmartArt, headers, footers, or embedded objects might not be read.
• Without code interpreter, extracted text from Office documents is limited to 30,000 characters per file and 30,000 characters total across multiple files. If exceeded, the content is discarded. PDF files are processed as the file itself, so that character limit does not apply to PDFs.

Recommended checks:

1. Confirm whether the published behavior matches the known limitation
   • If the agent in Teams returns a text-only style response or ignores the file, that aligns with the documented publish limitation.
2. Verify the target channel actually supports file input
   • Supported: Teams, Microsoft 365 Copilot, custom/demo website, Facebook, Omnichannel, Test your agent.
   • Not supported: SharePoint, voice, telephony.
3. Check whether the environment uses CMK
   • In a CMK-enabled environment, files can be attached but are not processed.
4. Check file type and content structure
   • Supported file types include DOCX, CSV, PDF, TXT, JPG, PNG, WebP, and nonanimated GIF.
   • XLSX and PPTX are only available in experimental mode.
   • If Word files rely on text boxes, shapes, SmartArt, headers, or embedded objects, the agent may appear to miss the content.
5. Check size and text limits
   • File input guidance lists a 15 MB individual file size restriction.
   • Without code interpreter, Office-document extracted text over the 30,000-character limit is discarded.
6. If this must work after publishing, evaluate the documented exception
   • Attachments can be supported when the message is sent to a skill, where the skill bot supports processing attachments.

If the scenario is specifically “works in Copilot Studio test, but not in Teams/Microsoft 365 Copilot after publish,” the most likely documented cause is the published-channel attachment limitation, not a problem with the agent logic itself.

• Key concepts - Publish and deploy your agent
• Allow file input from users
• Allow file input from users
• Allow file input from users
• Attach files to a conversation (preview)
• Copilot agent can't read PDF files - Microsoft Q&A