Opening a Markdown file in the main IDE and switching the in-editor toggle to Preview (Cursor’s rich Markdown editor, not the classic side preview) shows a completely blank black pane. No rendered text, no error toast, status bar shows 0 errors / 0 warnings.
Switching back to Markdown (source) shows the file content correctly.
Steps to Reproduce
Open a reasonably large Markdown file that includes a Mermaid flowchart with several subgraph blocks and many edges.
Actual behavior
Preview pane is entirely black / empty.
No visible error UI.
Classic commands (Cmd+Shift+V, “Markdown: Open Preview”) often do nothing or are unavailable depending on editor mode (related to known markdownEditor.toggleMode / raw-editor replacement issues).
Workarounds tried
Reopen file in IDE (not Agents Window viewer).
Toggle Preview ↔ Markdown repeatedly.
Simplified Mermaid (removed <–>, removed spaces in subgraph titles).
Preview remains blank.
Expected Behavior
Preview renders the Markdown (headings, tables, and Mermaid diagram, or at least the Markdown with a Mermaid fallback/error).
I am seeing this too. Sometimes only part of the markdown file gets displayed in “preview” mode, while the whole file is visible in “markdown” mode.
I also noticed that when I first open the markdown file, it says it is in “preview” mode, but it displays the raw markdown instead. Switching then to “Markdown” mode, shows the blank page or incomplete file rendering.
The only work around I have is to look at the markdown file in a terminal tool like glow.
It isn’t your Mermaid diagram. This is a known issue with Cursor’s built-in Preview (the rich WYSIWYG renderer behind the Markdown/Preview toggle), and the actual trigger is a specific Markdown list structure. In your file it’s the “Partial status” bullet under section 1: a single bullet that contains a paragraph, then a table, then a further continuation paragraph (the “Remaining legacy:” line). The built-in Preview’s renderer rejects that “one bullet with multiple blocks plus a trailing loose paragraph” shape, and because the failure isn’t caught gracefully, the whole pane goes blank instead of showing an error. That’s why simplifying the Mermaid didn’t change anything, and why the Source view still works. We’ve reproduced it on our side and it’s on our radar.
Two ways to unblock yourself now:
Use the classic Markdown preview (a different renderer that isn’t affected). Since the file opens in the built-in editor, first reopen it as plain text: right-click the editor tab and choose Reopen Editor With… → Text Editor. Then Cmd+Shift+P → Markdown: Open Preview (or Open Preview to the Side). Headings, tables, and text render fine there. (For Mermaid to show as a rendered diagram in the classic preview rather than a code block, you can add a Markdown Mermaid extension from the marketplace.)
If you’d rather keep using the built-in Preview, adjust the offending bullet: fold that trailing “Remaining legacy:” line into the bullet’s paragraph, or make it a nested sub-bullet, so the item isn’t paragraph + table + a separate loose paragraph. The same applies to any bullet that mixes a paragraph, a block like a table or blockquote, and then another paragraph.
@aplatti - this is very likely the same underlying issue. The classic preview above should render your files in the meantime. If you can share a small snippet of one that goes blank, I’m happy to confirm it’s the same trigger.
