[BUG] Status line JSON contains literal newlines in session_name, breaking jq parsing

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code

What's Wrong?

When a session originates from a slash command (e.g. /brainstorm), the session_name field in the status line JSON input contains literal (unescaped) newlines. This produces invalid JSON that causes jq and other strict JSON parsers to fail silently, resulting in the status line not rendering any data derived from the JSON.

What Should Happen?

The session_name field should properly escape newlines as \n per the JSON specification, so that the status line input is always valid JSON.

Error Messages/Logs

Example of invalid JSON received by the status line command:

"session_name":"<command-message>brainstorm</command-message>
<command-name>/brainstorm</command-name>
<command-args (Fork 7)"

The literal newlines inside the string value make the JSON unparseable.

Steps to Reproduce

1. Configure a custom status line in settings.json that parses stdin with jq
2. Start a conversation using a slash command (e.g. /brainstorm)
3. Fork the conversation with /fork
4. The status line fails to render any JSON-derived data (e.g. context bar)
5. Resuming the original session also exhibits the same broken behavior

Claude Model

Opus

Is this a regression?

I don't know

Claude Code Version

2.1.55 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

Terminal: WezTerm

Workaround: pipe stdin through tr '\n' ' ' before jq to collapse literal newlines.