[BUG] Autocomplete prompt suggestion includes hallucinated non-English 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?

Autocomplete prompt suggestion included hallucinated Korean text ("오늘은 이 영상에서 만나보실게요") appended to an English suggestion post-submission. Likely glitch in the suggestion generation/hidden text. Went to approve and submit the autopopulated follow-on prompt from CC. Original prompt said "open it in a file so I can read through" - submitted it as is with no edits. In conversation thread, my message now reads "open it in a file so I can read through <korean letters that mean 'today we will meet in this video'>"

*I don't speak korean, have never typed in korean, do not have korean keyboard enabled, did not copy/paste, have no clipboard manager, and it did not originally show in the text prompt. It was generated by Claude Code's prompt suggestion feature.

<img width="1088" height="548" alt="Image" src="https://github.com/user-attachments/assets/050133f5-7fce-4a04-a554-a5d8a84016d8" />

What Should Happen?

Claude should not invent random letters that I did not approve or submit.

Error Messages/Logs

Steps to Reproduce

1. Start a Claude Code session
2. Ask Claude to read/display a file (e.g., "can you open the prompt for [skill name]")
3. After Claude responds, observe the autocomplete prompt suggestion
4. Accept the suggested follow-up prompt
5. The accepted prompt may contain hallucinated Korean text appended to the English suggestion: "오늘은 이 영상에서 만나보실게요" ("you'll see it in today's video")

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.55

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_