[BUG] Code Block Snippet displaying as Inline Code in chat

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?

Fenced code blocks returned by the assistant render as inline code instead of block-level code. The content appears in the same inline pill/badge style used for single-backtick spans, rather than as a multi-line block with its own background, padding, and (if applicable) syntax highlighting.

Previous Existing Issue but incorrectly closed: https://github.com/anthropics/claude-code/issues/11804

What Should Happen?

Expected behavior:
Triple-backtick fenced blocks should render as block-level code: full-width container, preserved line breaks, monospace, language-aware syntax highlighting, and a copy button (matching how bash / ts blocks render elsewhere in the UI).
Actual behavior:
The block renders as inline code — single-backtick styling — with content flowing inline with surrounding text. Line breaks inside the fence are not preserved visually, and there is no block container or copy affordance.

<img width="400" height="269" alt="Image" src="https://github.com/user-attachments/assets/a83164d6-0a6a-4f42-807c-dafb66b1894d" />

<img width="400" height="730" alt="Image" src="https://github.com/user-attachments/assets/fb5aff8a-f4bb-47bb-ac7c-1573f9653ed8" />

Error Messages/Logs

Steps to Reproduce

Have the assistant return a response containing a fenced code block, e.g.:

{
  "name": "Jordan",
  "role": "engineer",
  "team": "engineering",
  "active": true
}

Observe that it renders inline rather than as a block.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

v2.1.150 (VS Code Extension)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

I am running the Claude Code VSCode Extension