[BUG] Tab-completing @ file reference after /command deletes previously typed text

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 invoking a slash command (e.g., /review, /init) and typing additional text
before adding an @ file reference, pressing Tab to autocomplete the file path
deletes all text between the command and the @ reference.

What Should Happen?

Tab-completion should only replace the @... token with the completed file path,
preserving all text between the slash command and the file reference.

Error Messages/Logs

All text typed between the slash command and the `@` reference is erased upon
Tab-completion.

Steps to Reproduce

1. Type a slash command followed by some text and a file reference, e.g.:

/review please check this code @../some_project/

1. Press Tab to autocomplete the @ file reference
2. The text "please check this code" is deleted — only the slash command and the

completed file reference remain

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.50

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

Environment

• Claude Code version: 2.1.50
• Platform: Linux (WSL2, kernel 6.6.87.2-microsoft-standard-WSL2)
• Terminal: CLI

Notes

This also reproduces with custom skills (e.g., /spec). It may be related to #13940
(prompt suggestion replacing text, fixed in v2.0.70), but that fix addressed prompt
suggestions on empty input. This bug is specifically about @ file reference
Tab-completion within slash commands wiping intermediate text.