AU plugin not showing up in GarageBand on macOS 15 Sequoia — is there a free workaround?

Audio Plugins
1

Hi all, I’m a beginner just getting started with JUCE plugin development and I’ve run into a wall trying to load my first AU plugin into GarageBand on macOS 15.7.3 Sequoia.

Setup:

  • macOS 15.7.3 (Sequoia)
  • Xcode 26.2
  • JUCE (latest)
  • Built a basic gain plugin (AudioProcessor + APVTS + one rotary slider)

The problem:
The plugin builds successfully as an AU. The .component file is in ~/Library/Audio/Plug-Ins/Components/. But it doesn’t appear in GarageBand’s Audio Units menu, and pluginkit returns nothing when I search for it.

Everything I’ve tried:

  • Clearing the AU cache (~/Library/Caches/AudioUnitCache)
  • Running sudo killall -9 AudioComponentRegistrar
  • Ad-hoc code signing with codesign --force --deep --sign -
  • Stripping quarantine attributes with xattr -cr
  • Manually registering with pluginkit -a
  • Setting defaults write com.apple.audio.AudioComponentRegistrar AllowUnsignedAudioUnits -bool YES
  • Trying to attach Xcode debugger to GarageBand (blocked by Sequoia sandbox)
  • Updating the bundle identifier from the placeholder com.yourcompany.SimpleGain to a real one

codesign -vvv reports the component as valid and satisfying its Designated Requirement, but pluginkit -m -v | grep -i gain consistently returns nothing.

Question:
Is there any free way to get an unsigned/ad-hoc signed AU plugin to load in GarageBand on Sequoia without a paid Apple Developer certificate? Or has Sequoia fully closed this off? I’m aware Reaper is the practical solution for development, just want to know if GarageBand is completely off the table without the $99 certificate.

Thanks in advance!

2

Does it load in the JUCE AudioPluginHost?

Does it work when you run auval on it?

Is it AUv2 or AUv3? Note that AudioComponentRegistrar is for AUv2 and pluginkit is for AUv3. So if it’s an AUv2 then it’s normal for pluginkit to not show anything.