Remote Control: first message of a new session only accepts images, follow-up messages accept PDFs

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When starting a new session on a Remote Control host, the composer for the first message only accepts images. This happens in the Claude Desktop app (Code tab) and on claude.ai/code.

The + menu already shows the difference: in a new session it offers "Add image", in a running session "Add files or photos".

In the Desktop app, attaching a PDF to the first message is refused with a toast and the file is never attached:

Nur PNG-, JPEG-, GIF- und WebP-Bilder werden unterstützt. (German UI; in English: "Only PNG, JPEG, GIF, and WebP images are supported.")

Once the session is running, the same PDF can be attached to a follow-up message without problems: Claude Code downloads it to the host and Claude reads it. So the host and the transport handle PDFs; only the new-session composer refuses them. claude.ai/code behaves exactly the same.

What Should Happen?

The first message of a new session should accept the same attachments as follow-up messages. The docs say: "attach a photo or file in the Claude app or at claude.ai/code ... Claude Code downloads other files to your machine and passes them to Claude as @ file references." (https://code.claude.com/docs/en/remote-control)

Error Messages/Logs

No error in the session or the host logs. The client refuses the file before upload, so the host never receives anything.

Screenshots (added below):

1. The toast after attaching a PDF to the first message

<img width="1150" height="167" alt="Image" src="https://github.com/user-attachments/assets/50172646-a7b4-4354-91d0-b04612c61478" />

1. The + menu in a new session ("Add image")

<img width="300" height="167" alt="Image" src="https://github.com/user-attachments/assets/f58acb71-a2f5-4148-9a27-28cb54fb8245" />

1. The + menu in a running session ("Add files or photos")

<img width="600" height="334" alt="Image" src="https://github.com/user-attachments/assets/fbbf40b5-2013-452f-ba6a-25266cb6232f" />

Steps to Reproduce

1. On a Mac, run claude remote-control (server mode).
2. In the Claude Desktop app (Code tab), start a new session and pick that host as the environment.
3. Open the + menu: it offers "Add image".
4. Attach a PDF to the first message via the + button, drag and drop or paste. The toast above appears and the PDF is not attached.
5. Send a text-only first message so the session starts.
6. Open the + menu again: it now offers "Add files or photos". Attach the same PDF: it is accepted and Claude can read it.
7. Repeat steps 2 to 6 on claude.ai/code: same result.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.287

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

• Host: macOS 26.5.2, Claude Code 2.1.287
• Client: Claude Desktop 2.19675.0 on the same Mac, and claude.ai/code in the browser
• Also reproduced with a Windows 11 host, so it does not depend on the host OS.
• The model does not matter, this is client-side (tested with Opus 5.5).
• Possibly related, but different: #64240 and #74409 (Remote Control attachments dropped in transit, fixed in 2.1.207). In this case the client refuses the file before it is sent.