Unable to load AU plug-in on OSX

[quagly]

Trying to get started with pedalboard.

OSX: 26.4.1
Python: 3.12.12
pedalboard: 0.9.22

I am unable to load any of my plug-ins. They all have the same error.

CODE

from pedalboard import load_plugin                                                                                                      
au_plugin = load_plugin("/Library/Audio/Plug-Ins/Components/Pianoteq 9.component") 

ERROR

ImportError: Failed to load plugin as VST3Plugin or AudioUnitPlugin. Errors were:
        VST3Plugin: Unable to scan plugin /Library/Audio/Plug-Ins/Components/Pianoteq 9.component: unsupported plugin format or scan failure.
        AudioUnitPlugin: Unable to scan plugin /Library/Audio/Plug-Ins/Components/Pianoteq 9.component: unsupported plugin format or scan failure.

What are next steps for debugging?

[ausbernard]

I traced the failure to getAudioUnitIdentifiersFromFile in our Audio Unit parser — it reads AudioComponents from the plugin's Info.plist, but if that key is missing or structured differently (some plugins register AUs dynamically rather than via plist), it returns empty and the scan fails.

Could you run this and paste the output?

plutil -p "/Library/Audio/Plug-Ins/Components/Pianoteq 9.component/Contents/Info.plist"

That'll confirm whether the AudioComponents key exists and whether the type/subtype/manufacturer values are stored as
strings or integers. Either way, the fix is to fall back to AVAudioUnitComponentManager (the macOS system AU registry) when
plist parsing yields nothing — I have a patch ready once we confirm the cause.

[quagly]

plutil -p "/Library/Audio/Plug-Ins/Components/Pianoteq 9.component/Contents/Info.plist"

{
  "AudioComponents" => [
    0 => {
      "description" => "Pianoteq 9"
      "factoryFunction" => "mdrtEntryPointAUFactory"
      "manufacturer" => "Mdrt"
      "name" => "Modartt: Pianoteq 9"
      "sandboxSafe" => false
      "subtype" => "Pt9q"
      "type" => "aumu"
      "version" => 590337
    }
  ]
  "CFBundleDevelopmentRegion" => "English"
  "CFBundleDisplayName" => "Pianoteq 9"
  "CFBundleExecutable" => "Pianoteq 9"
  "CFBundleIconFile" => "Pianoteq.icns"
  "CFBundleIdentifier" => "com.modartt.Pianoteq9.AudioUnit"
  "CFBundleInfoDictionaryVersion" => "6.0"
  "CFBundleName" => "Pianoteq 9"
  "CFBundlePackageType" => "BNDL"
  "CFBundleShortVersionString" => "9.2.1"
  "CFBundleSignature" => "Pt9q"
  "CFBundleVersion" => "9.2.1/20260610"
  "CSResourcesFileMapped" => true
  "LSMinimumSystemVersion" => "10.7.0"
  "NSAppTransportSecurity" => {
    "NSAllowsArbitraryLoads" => false
    "NSExceptionDomains" => {
      "modartt.com" => {
        "NSIncludesSubdomains" => true
        "NSTemporaryExceptionAllowsInsecureHTTPLoads" => true
        "NSTemporaryExceptionMinimumTLSVersion" => "TLSv1.1"
      }
    }
  }
  "NSHumanReadableCopyright" => "Modartt S.A.S."
}