[BUG] Desktop Code tab: can't send a message containing more than one slash command

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?

In the Claude Desktop app (Code tab, local session), a message that contains two slash commands (custom skills) separated by plain text is not sent at all. The composer only shows a warning toast and drops nothing into the conversation.

Example input:

/day-plan
potom
/day-review

("potom" is Slovak for "then" — I want Claude to run the first skill, then the second one.)

What Should Happen?

The message is sent and Claude runs the commands one after another (first /day-plan, then /day-review) — or, at minimum, the first command runs and receives the rest of the text as its arguments, as in the Claude Code CLI.

If this is intentionally unsupported, the error message should say clearly which part is the problem (a second slash command) and suggest sending the commands as separate messages.

Error Messages/Logs

A command takes file @-mentions but no other @-mentions, slash commands, links, or inline formatting, so nothing was sent. Remove them.

Steps to Reproduce

1. Open Claude Desktop (macOS) → Code tab → New session, environment "This computer", any local folder.
2. Have at least two custom skills / slash commands available (e.g. /day-plan and /day-review).
3. In the composer, insert the first command via the slash picker, type some plain text on the next line, then insert the second command via the picker:

``
/day-plan
then
/day-review
``

1. Press Enter.
2. Nothing is sent; the warning toast above is shown.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.288 (Claude Code), Claude Desktop app for macOS

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

Related (same area, but different symptoms):

• #98568 — a slash command combined with a URL is blocked with the same toast.
• #89802 — slash commands are only recognized at the very start of a message (silent failure). Here the failure is explicit: the message with two commands is refused outright.

Chaining skills ("run X, then Y") is a natural workflow. The CLI passes the rest of the line to the command as arguments, so this asymmetry between CLI and Desktop is surprising.

Screenshot:

<img width="4064" height="2148" alt="Image" src="https://github.com/user-attachments/assets/1852a428-26f9-41ba-ac9c-929798f8e26f" />