[BUG] VSCode extension: copy button on completed code blocks flickers during streaming

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?

While Claude is streaming a response, the "copy" icon in the top-right corner of every completed code block flickers (rapidly fades in/out) at the same rate as new tokens arrive. The flicker only happens when the mouse cursor is hovering over the code block — which is exactly when the user is about to click the button.

This produces visible strobing of the copy button.

What Should Happen?

The copy button should remain stably visible while the cursor hovers over a completed code block, regardless of streaming activity in the rest of the message.

Error Messages/Logs

Steps to Reproduce

1. Install Claude Code VSCode extension v2.1.140.
2. Open the Claude Code panel.
3. Send a prompt that produces a long response containing at least one early code block, e.g.:

"Show me a TypeScript example of a debounce function, then explain in 5 paragraphs how it works."

1. As soon as the first ``` code block is fully rendered, hover the mouse over it.
2. Keep watching the copy icon in the top-right corner of that code block while the model continues streaming the explanation below.

Expected: copy icon stays solidly visible while hovered.
Actual: copy icon flickers/strobes with the streaming token rate (~10–20 Hz).

Environment:

• Claude Code VSCode extension: v2.1.140 (anthropic.claude-code)
• VSCode: 1.119.0 8b640eef5a6c6089c029249d48efa5c99adf7d51 arm64
• macOS 15 (Darwin 25.0.0), MacBook Pro 14" M4

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Platform

AWS Bedrock

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_