Mermaid diagrams show up blank in GitHub Copilot chat

Open
#321,529 7 comments 0 reactions 1 assignee View on GitHub

@justschen is already working on this.

Since Aug 14, 2026.

Assessment

This issue has not been assessed yet.

Description

bug mermaid regression

I don't know how long "diagrams" have been available, but whenever Claude Opus 4.8 sends back a "diagram", it just shows a blank white box. (A "rendering code block" message briefly inside it.) There is an "Open Diagram in Editor" button, but it doesn't do anything.

If I restart VS Code, the diagram appears (although it doesn't look like a diagram—it looks more like source code for edges in a graph). There seems to be no reliable way to get it to appear—although restarting VS Code once got it to show up.

If I copy and paste the response as Markdown, I can see that this is a mermaid Markdown block.

This is similar to what happened in #280071, but in this case the block never showed up in the first place.

Version: 1.124.2 (user setup)
Commit: 6928394f91b684055b873eecb8bc281365131f1c
Date: 2026-06-12T00:12:36Z
Electron: 42.2.0
ElectronBuildId: 14159160
Chromium: 148.0.7778.97
Node.js: 24.15.0
V8: 14.8.178.14-electron.0
OS: Windows_NT x64 10.0.26200
Dominant language
TypeScript
Stars
193k
Forks
42.9k
PR metrics pending

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from microsoft/vscode

All issues in microsoft/vscode

Similar issues

More TypeScript issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.