QL extensions don't seem to work

[czottmann]

• Mud 2.1.0
• macOS 26.4.1 (25E253)
• direct install

I can't get the QL extensions to work. Whether they're enabled or not, MD files are identically rendered as text both in thumbnail and preview overlay. Finder window screenshot:

If you need more details, I may be able to provide them. :) Thanks in advance!

[drjasinski]

Same here:

• macOS 26.4.1
• Mud 2.1.0
• MudQuickLook.appex is installed and enabled
• .md file UTI: net.daringfireball.markdown
• Quick Look shows raw Markdown text
• Logs show Mud QuickLook processes start and immediately quit

[joseph]

This is interesting. I had some real problems with this during development. In my case it was because another app on my system was pinning the .md UTI to public.plain-text: https://github.com/joseph/mud/blob/main/Doc/Plans/Archive/2026-04-quicklook-extension.md#1-macvims-uti-pollution

But that doesn't sound like the case here if logs show that Mud's QL processes are starting. Are there any crash logs? If not, an lsregister dump may be useful for debugging.

I did just check QL in Mud on another macOS 26.4 laptop after running the Sparkle update to 2.1.0 and had success. So it works out of the box on some machines — but clearly it's not handling certain system configurations or something.

Here's Claude Code's suggested steps if you're comfortable sharing the output:

The lsregister tool lives at a deep path, so it's easiest to alias it first. In Terminal:

alias lsregister=/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister

Run these two commands:

# 1. All Mud-related registrations (app + QuickLook + Thumbnail extensions)
lsregister -dump | grep -B 2 -A 30 -i 'org\.josephpearson\.Mud' > ~/Desktop/mud-lsregister.txt

# 2. Everything claiming the Markdown UTI
lsregister -dump | grep -B 5 -A 10 'net\.daringfireball\.markdown' > ~/Desktop/markdown-uti.txt

Look for (or attach to this issue for me to look for):

• More than one entry for org.josephpearson.Mud.QuickLook or org.josephpearson.Mud.Thumbnail
• Other apps exporting or claiming net.daringfireball.markdown with higher priority
• The reg date: lines on each entry, which tell us which registration is winning

Also helpful, if you can grab them at the same time: the path of every Mud.app copy on disk —

mdfind "kMDItemCFBundleIdentifier == 'org.josephpearson.Mud'"

[czottmann]

Thanks for looking into this, Joseph!

• /Applications/Mud.app
• markdown-uti.txt
• mud-lsregister.txt

[drjasinski]

• /Applications/Mud.app
• markdown-uti.txt
• mud-lsregister.txt

[joseph]

Thank you both! It looks like these have two different causes. I should caveat that the analysis is mostly Claude's, and Claude was not very good at tracking down system registration problems during development. It's a pretty complex area of macOS without much tooling. So anyway, the analysis might be wrong.

@czottmann It looks like Mud is losing out to QLMarkdown, or possibly MarkEdit. Not clear to me why you don't see QLMarkdown's preview instead though. But the first thing you could try is disabling QLMarkdown's extension in System Settings → General → Login Items & Extensions → Quick Look. Then make sure Mud's extension is enabled. Then killall -KILL quicklookd.

@drjasinski Your system appears to have the Mud binary in three places, and in two of those places, it's an outdated binary. Possibly a problem with Mud's Sparkle implementation — I'm going to investigate whether that's the case. But it should resolve if you delete the other two. This command will give you the locations:

lsregister -dump | grep -B 50 -A 5 "identifier:.*org\.josephpearson\.Mud\s*$" | grep -E "path:"

I ran into a similar problem during the Thumbnail work — more notes on that here: https://github.com/joseph/mud/blob/main/Doc/Plans/Archive/2026-04-document-icons.md#gotcha-2-duplicate-registrations-cause-silent-non-firing

[drjasinski]

lsregister -dump | grep -B 50 -A 5 "identifier:.org.josephpearson.Mud\s$" | grep -E "path:|reg date:|bundle flags:|identifier:"
reg date: 2026-04-11 13:58 (POSIX 1775908700, 𝛥 2Wo. 4Tg. 16Std. 13Min. 54Sek.)
bundle flags: ui-element (0000000000000004)
path: /private/tmp/dmg.xIzv62/Mud.app (0xe990)
identifier: org.josephpearson.Mud
reg date: 2026-04-11 13:58 (POSIX 1775908700, 𝛥 2Wo. 4Tg. 16Std. 13Min. 54Sek.)
bundle flags: has-display-name ui-element (0000000000000006)
path: /Volumes/Mud/Mud.app (0xe9a4)
identifier: org.josephpearson.Mud
reg date: 2026-04-11 13:58 (POSIX 1775908700, 𝛥 2Wo. 4Tg. 16Std. 13Min. 54Sek.)
bundle flags: ui-element (0000000000000004)
path: /Applications/Mud.app (0xe9c8)
identifier: org.josephpearson.Mud

lsregister -u /Applications/Mud.app
lsregister -u /Volumes/Mud/Mud.app
lsregister -u /private/tmp/dmg.xIzv62/Mud.app/
lsregister -f /Applications/Mud.app
killall Finder
lsregister -dump | grep -B 50 -A 5 "identifier:.org.josephpearson.Mud\s$" | grep -E "path:|reg date:|bundle flags:|identifier:"
path: /Applications/Mud.app (0xefd8)
identifier: org.josephpearson.Mud

QuickLook still doesn’t work.

[czottmann]

But the first thing you could try is disabling QLMarkdown's extension in System Settings → General → Login Items & Extensions → Quick Look. Then make sure Mud's extension is enabled. Then killall -KILL quicklookd.

Thanks. Did that (QLMarkdown was disabled before), there's no quicklookd, but I killed all QuickLook* processes. Still no dice, I'm afraid.

[joseph]

I'm going to continue to dig on this, but presently on OSS vacation for a few more days. 🌴

[czottmann]

@joseph Good idea. Enjoy! 👋🏼 We'll be here when you come back, I reckon