Agents Window sometimes opens the legacy Markdown editor by default

[hediet]

Type: Bug

Reported behavior

A user reported that opening a Markdown file in the Agents Window showed the legacy Markdown editor instead of the new rich Markdown editor, even though they had not configured an editor association or Markdown-editor setting.

Expected behavior

Markdown files opened in the Agents Window use the new rich Markdown editor by default when no explicit editor association says otherwise.

Actual behavior

The user reports that the legacy Markdown editor opened. We do not yet know whether this was the Markdown preview custom editor or the Monaco source editor.

Current reproduction status

I could not reproduce this when launching with --transient; Markdown files consistently opened in the new editor.

Information needed

• VS Code version/commit and operating system
• Whether the editor was the Markdown preview or Monaco source editor
• The effective value and configuration scope of workbench.editor.markdownDefaultEditorInAgentsWindow
• The effective workbench.editorAssociations and workbench.diffEditorAssociations values
• How the Markdown file was opened in the Agents Window
• Whether Reopen Editor With... shows and successfully opens the new Markdown editor