Remote Control: image/screenshot attachments frequently fail to sync from mobile to session

Description

When using Remote Control to interact with a Claude Code session from the mobile app (iPhone), image attachments (screenshots) sent from the phone frequently fail to reach the session. Text messages sent in the same way sync reliably and immediately, but images sent right after (or in the same session) often never arrive — the assistant reports no attachment was received, even though the sender can see the image as successfully sent/attached in their own chat view.

Environment

• Client: Claude mobile app (iOS), connected via Remote Control to a desktop Claude Code session (macOS)
• Text messages: sync reliably
• Image/screenshot messages: fail intermittently, no error shown to sender

Steps to reproduce

1. Start a Claude Code session on desktop (macOS), enable Remote Control (remoteControlAtStartup: true in settings, or per-session /remote-control)
2. Connect from the Claude iOS app to the same session
3. Send a few text messages — confirm they arrive and are visible in the session
4. Take a screenshot on the phone and send it as an attachment in the same conversation
5. Observe: the image often does not appear in the session's context at all (the assistant sees no attachment), while the sender's own chat view shows the image as sent

Observed behavior

• Recurred multiple times within a single session (4+ times in one evening)
• No error or retry prompt shown to the user on the sending side
• Text-only messages sent before/after the failed image always synced correctly
• Resending the same image sometimes works, sometimes doesn't, with no clear pattern

Expected behavior

Image attachments sent via Remote Control from the mobile app should sync to the session as reliably as text messages, or the sender should receive a clear failure/retry indicator when an attachment does not sync.

Impact

This made visual troubleshooting (e.g., confirming UI state, reading on-screen error messages) very difficult during a remote session, forcing fallback to manual text descriptions of screen content, which is error-prone and frustrating for non-technical users.