[BUG] Slash command execution message appears twice in CLI output

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?

Description:

When invoking a custom slash command via the SlashCommand tool, the command execution message appears twice in the CLI output, creating the appearance
that the command is being processed twice.

Steps to Reproduce:

1. Invoke a custom slash command (e.g., /create-work-item) via the SlashCommand tool
2. Observe the CLI output

Expected Behavior:
The command execution message should appear once:
> /create-work-item is running…

Actual Behavior:
The command execution message appears twice:
> /create-work-item is running…
> /create-work-item is running…

Impact:

• Confusing user experience (appears like duplicate processing)
• Actual execution only happens once (no functional impact)
• Appears to be a display/messaging issue

Context:
The duplication seems to occur between when the SlashCommand tool returns and when the command prompt expands.

What Should Happen?

Expected Behavior:
The command execution message should appear once:
> /create-work-item is running…

Error Messages/Logs

Steps to Reproduce

Steps to Reproduce:

1. Invoke a custom slash command (e.g., /create-work-item) via the SlashCommand tool
2. Observe the CLI output

<img width="1144" height="146" alt="Image" src="https://github.com/user-attachments/assets/e166878b-967a-4738-b16c-3557b58e03f4" />

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.0.22

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_