[BUG] Markdown renderer incorrectly treats single tilde (~) as strikethrough

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?

Single tildes used for "approximately" (e.g., ~15M minutes) are being rendered with strikethrough formatting in the markdown viewer, when they should just display as plain text

What Should Happen?

Expected behavior: Single tilde should display as "approximately" symbol
Actual behavior: Text appears with strikethrough formatting

Error Messages/Logs

Steps to Reproduce

create markdown with

~test test~

and see if it generates strikethrough

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.12

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

This has been previously reported in #9757 , but that issue has been closed after just one month of inactivity, despite the closing message mentioning 2 months of inactivity, and now has also been locked. This anti-user automatic behavior is quite annoying. Bugs should be investigated and fixed, not ignored.

One of my comments from the previous issue on this subject:

I had a similar issue with a markdown rendering engine (the issue I had is not directly related to this bug, I found this bug report by accident when looking for solutions to my unrelated problem).

It seems there is a particular flavor of markdown, called GFM (GitHub Flavored Markdown), for which this particular "bug" is considered a "feature". The engine I was using supports disabling GFM, which fixed my particular problem.

GFM has other peculiarities too, for example the handling of new lines is also inconsistent with standard markdown. From what I see, many LLM tools use GFM for rendering, instead of standard markdown. LM Studio for example is affected by the same "bug", I'm guessing for the same reason, GFM support.

The problem is that, in my experience, LLMs can frequently generate "~" characters when not actually "intending" to strikethrough any text, and this "feature" can be quite annoying when that happens.

Further comment on the subject:

For example, Unix/Linux home directories can be represented using the ~ character in paths, as a placeholder, so LLM outputs containing such home directory based paths will frequently trigger this incorrect strike-through formatting.