[BUG] Stray Unicode characters rendered in terminal 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?

Claude Code's terminal output sometimes contains stray Unicode characters (subscript letters, arrow symbols like ▶, and other glyphs) embedded mid-word in responses. This makes the text difficult to read.

Expected behaviour:
Plain readable text, e.g. "Adding a task details page"

Actual behaviour:
Stray characters appear mid-word, e.g. "Addingₐaₙtask details page" or "Markingₙa▶directionᵒasₖcomplete"

Environment:

• macOS 15.7.3
• Terminal (Hyper)

<img width="1948" height="1068" alt="Image" src="https://github.com/user-attachments/assets/45d8ccf2-51b4-4344-bcfb-9c3ebb56866f" />

What Should Happen?

Plain readable text.

Error Messages/Logs

It outputs things like this:  

Addingₐaₙtask details page
Markingₙa▶directionᵒasₖcomplete

Steps to Reproduce

Just ask Claude Code to anything and check it's output.

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.47

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_