No way to attach files or images to a message from the GitHub Mobile app in a remote CLI session #5117

Summary

In a remote Copilot CLI session driven from the GitHub Mobile app, there is no way to attach a file or image to a message. The desktop/web session supports attachments, so the capability exists on the backend — the mobile composer simply offers no entry point for it.

This is distinct from #745, which is about the local CLI not reading attached file contents. Here the problem is one step earlier: on mobile you cannot attach anything at all.

Steps to reproduce

1. Start a session with copilot on a desktop and enable /remote.
2. Open that remote session from the GitHub Mobile app.
3. Try to attach a screenshot or file to a message in the mobile composer.

Expected

A way to attach an image/file from the phone (camera roll, share sheet, or file picker), the same as the web/desktop session, so screenshots and logs can be handed to the agent while away from a desk.

Actual

No attach/upload control is present in the mobile composer. The only way to pass a file to the agent is to paste its text, or upload it elsewhere (gist, repo) and paste a URL for the agent to fetch.

Why it matters

Mobile is where the "triage from the couch" use case lives, and that use case is overwhelmingly about showing the agent something — a screenshot of a failing dashboard, a photo of a whiteboard, an error on another screen. Without attachments, the mobile session is text-only and the most natural mobile input is unavailable.

Related

• File attachments in interactive mode do not attach file contents, just line count. Nothing gets attached in prompt mode. #745 — attachments in the CLI do not attach file contents (different layer, same broad area)
• Remote session UI does not render on GitHub Mobile app (Android) - WebSocket works but content not displayed #3498 — remote session UI does not render on GitHub Mobile (Android)