[BUG] No syntax highlighting for Elixir (.ex/.exs) files

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?

Elixir (.ex / .exs) files have no syntax highlighting in code blocks and diffs. All Elixir code appears as plain white text. Other languages (TypeScript, Python, Rust) are highlighted correctly in the same session.

What Should Happen?

Elixir code should have syntax highlighting (keywords, strings, numbers, atoms, macros colored) similar to other supported languages.

Error Messages/Logs

Steps to Reproduce

1. Open Claude Code CLI
2. Ask Claude to create/edit a .ex file and a .ts file
3. Compare the diff output — .ts has colors, .ex is plain white

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

Unknown

Claude Code Version

2.1.150 (Claude Code)

Platform

Anthropic API

Operating System

Other Linux

Terminal/Shell

Other

Additional Information

Related: #48181 (GDScript — same root cause, same pattern).

Claude Code TUI uses highlight.js for rendering. Elixir is included in highlight.js's default grammar set (hljs.getLanguage('elixir') returns a valid grammar), so this is likely just a missing extension-to-language mapping. Fix should be a one-liner: add '.ex' → 'elixir' and '.exs' → 'elixir' to the extension map.