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Files and attachments

Attach text files or a document from your Library to a message, and what to do when a file is refused.

Crossbox is not open to the public yet. These guides describe the application as it works today. Join waitlist

On this page

You can attach files to a message so the model can read them when it answers. Attaching works inside a chat.

What you can attach

  • Plain text, Markdown, CSV, JSON, or Jupyter notebooks (.ipynb).
  • Up to 8 MB per file.
  • Up to 5 files per message.

A Jupyter notebook is converted to text so it can be read. Your original file is the one that is kept and downloaded.

Attach a file in a chat

  1. Open a chat and open the attach button at the left of the message box.
  2. Choose Upload file to pick a file from your device, or Add from Library to add one of your documents.
  3. Each file appears as a card with its state (uploading, attached, or not attached and why). Remove a card to take the file off the message.
  4. Write your message and send it. The files go with it.

You can also paste a file or text into the message box; it arrives as an attachment in the same way.

Add from Library

Add from Library adds one of your documents at the version you pick. The message refers to that exact version, so a later edit to the document does not change what was attached.

If a file is refused or fails

  • A refused or failed file stays on its card and says why; it is not silently dropped.
  • A failed file offers one Try again. Use Remove if you do not want it on the message.
  • If the reason is the format or size, convert or shorten the file and attach it again.

Last checked against the product on 10 October 2026.

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