Where does the bug appear (feature/product)?
Cursor IDE
Describe the Bug
The in-editor Markdown Preview toggle (top-right of a .md tab: Preview / Markdown) silently truncates the document. Everything after a certain heading disappears. There is no error.
Cmd+Shift+V (VS Code Markdown Preview) shows the full file, so the source is valid.
This is Cursor’s TipTap/ProseMirror preview (markdownChunkedRender.js). It splits the file at headings, renders the first segment with setContent, then appends later segments with insertContentAt. If a later segment fails, the loop stops and all remaining sections are dropped.
The failing content is a fenced code block nested under a list item (the fence indented with two spaces). If that nested fence is in the first segment, it can still render. If it is in a later segment (after the first ~600 characters, when a new ## heading starts a new chunk), Preview stops at the previous heading.
Steps to Reproduce
- Create a new
.mdfile with this content (the first section must be long enough to exceed the ~600-character first-segment threshold):
## Section A
Filler paragraph 1 with enough text to push this first segment past the six hundred character threshold that Cursor uses.
Filler paragraph 2 with enough text to push this first segment past the six hundred character threshold that Cursor uses.
Filler paragraph 3 with enough text to push this first segment past the six hundred character threshold that Cursor uses.
Filler paragraph 4 with enough text to push this first segment past the six hundred character threshold that Cursor uses.
Filler paragraph 5 with enough text to push this first segment past the six hundred character threshold that Cursor uses.
Filler paragraph 6 with enough text to push this first segment past the six hundred character threshold that Cursor uses.
## Section B
- a list item that introduces a block:
```hcl
prod_environment = {
prevent_self_review = true
}
```
continuation paragraph inside the same list item.
K-MARKER-VISIBLE: this file rendered fully.
- Open the file and click the in-editor Preview button (not
Cmd+Shift+V). - Scroll to the bottom.
Control: copy the same file, un-indent the fence so it is at column 0 (not inside the list). Preview then shows Section B and K-MARKER-VISIBLE.
Expected Behavior
Preview should render the whole document, including Section B, the nested fence, and K-MARKER-VISIBLE.
If a chunk fails to parse, Preview should still show the rest of the file, or at least surface an error instead of truncating with no message.
Cmd+Shift+V already behaves correctly on the same source.
Operating System
MacOS
Version Information
Version: 3.21.18
VS Code Extension API: 1.128.0
Commit: c4730f7d93d787d9ab120af715999f0345ee5bc0
Date: 2026-09-22T02:04:34.641Z
Layout: IDE
Build Type: Stable
Release Track: Default
Electron: 42.10.0
Chromium: 148.0.7778.280
Node.js: 24.18.1
V8: 14.8.178.38-electron.0
xterm.js: 6.1.0-beta.291
OS: Darwin arm64 27.0.0
Does this stop you from using Cursor
No - Cursor works, but with this issue