Fixing Kate's Blank Markdown Preview on Kubuntu 25.10

TL;DR

sudo apt install markdownpart

Restart Kate. Done.

The problem

Kubuntu 25.10, KDE Plasma 6, latest Kate.

1. Open a .md file.
2. Go to Settings → Configure Kate → Plugins and enable Document Preview.
3. Hit View → Tool Views → Show Document Preview (or Ctrl+Alt+Shift+P).
4. The preview pane is blank.

Plugin is enabled. No error. Just an empty panel staring back at you.

What’s actually going on

Kate’s Document Preview plugin doesn’t render Markdown itself. It just asks KDE’s KParts system: “got anyone who can handle this MIME type?”

Kate (Document Preview plugin)
   │
   │  "Any KPart for text/markdown?"
   ▼
KPart system → markdownpart → renders to HTML → shows in preview

Without markdownpart, nobody answers. You get a blank pane instead of an error, because nothing failed to load — there was simply nothing to load in the first place. That’s why the silence is so eerie.

Diagnosing it

apt policy markdownpart

If you see this, you’ve found the culprit:

markdownpart:
  Installed: (none)
  Candidate: 25.08.1-0ubuntu1

The fix

sudo apt install markdownpart

Then restart Kate completely. An already-running Kate won’t rescan for new KParts, so closing the window isn’t enough.

killall kate
kate &

Open your .md file, hit Ctrl+Alt+Shift+P, and the rendered preview shows up on the side.

The same trap with other formats

This “plugin enabled, pane blank, no error” pattern isn’t unique to Markdown. Kate’s Document Preview delegates every format to a KPart, so a missing renderer for another type fails the same silent way. When a preview comes up empty, find which KPart should render it — System Settings → File Associations → Embedding shows the preferred service — then check whether that component’s package is installed with apt search/apt policy. It’s a Kubuntu packaging gap more than a Kate bug: the renderer ships in a separate package that isn’t pulled in automatically.

Summary

Item	Detail
Environment	Kubuntu 25.10 / KDE Plasma 6 / KF6
Symptom	Document Preview enabled, but .md stays blank
Cause	markdownpart KPart not installed
Fix	sudo apt install markdownpart + restart Kate

Kate’s Document Preview is a clean design — delegating to KParts keeps things nicely extensible. But shipping without the renderer it depends on makes for a rough first impression. Hope this saves someone the hour I spent chasing the wrong packages.