[BUG] Session crashes with "failed to load session" when Bash tool output contains U+2028 (LINE SEPARATOR) characters

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 a Bash tool command produces output containing Unicode U+2028 (LINE SEPARATOR) characters, the active session crashes immediately with a "failed to load session" error. The session cannot be recovered — clicking back into the conversation from the left panel shows an indefinite loading spinner with no resolution.

What Should Happen?

• The session should handle all valid Unicode characters in tool output without crashing
• U+2028 and U+2029 should either be preserved safely or normalized to standard newlines (U+000A) during session serialization
• If a session file is partially corrupted, the app should show a meaningful error and allow recovery rather than entering an unrecoverable spinner state

Error Messages/Logs

Steps to Reproduce

1. Open Claude Code (Desktop App)
2. Have a .docx file that contains bullet points or list formatting created in Microsoft Word (these often produce U+2028 characters when converted to plain text)
3. Ask Claude to read the .docx file — it will use textutil -convert txt -stdout "file.docx" on macOS
4. The Bash tool captures the output, which includes raw U+2028 characters
5. The session immediately crashes: the window switches to "failed to load session"
6. Attempting to reopen the session from the conversation list shows an infinite loading spinner

But also:

Any Bash command that outputs U+2028 should trigger this. You can test without needing a .docx file:

printf "Hello\xe2\x80\xa8World"

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

1.1.3830

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_