Environment:
- macOS 26 (Sequoia 15.7.4, build 24G517)
- Final Cut Pro 12.2
- Motion 5.8.x
- Xcode 26.3 (build 17C529)
- Apple Silicon (Mac Studio, ARM-64)
- FxPlug SDK 4.3.4 (from /Library/Developer/Frameworks/FxPlug.framework)
Problem: A third-party FxPlug 4 XPC-based plugin appears correctly in Motion's filter browser but does not appear in Final Cut Pro's Effects or Generators browser. This behavior occurs even with Apple's own Xcode FxPlug template project built with zero code modifications.
Plugin configuration:
- Architecture: Host app (SilverScreenHost.app) containing XPC pluginkit extension (SilverScreen.pluginkit)
- Bundle identifier: com.kb.silverscreen.relight
- Signed with Developer ID Application certificate
- Hardened runtime enabled
- No get-task-allow entitlement
- No app sandbox
- com.apple.version tested at both 3.30 and 4.0
- protocolNames tested as both FxFilter and FxGenerator
- NSPrincipalClass tested as both FxPrincipal and custom registrar class
What works:
- Plugin registers successfully with PlugInKit (pluginkit -mAD -p FxPlug shows + com.kb.silverscreen.relight)
- FCP activates the XPC service at launch (confirmed via log stream: name=com.kb.silverscreen.relight)
- Plugin appears correctly in Motion's Filters browser
- +load fires and executes in the plugin binary
- All plugins installed before the macOS 26 upgrade continue to appear in FCP normally
What doesn't work:
- Plugin never appears in FCP Effects or Generators browser
- FCP discovery shows "Final # of matches: 9" — same count as before plugin was installed, suggesting FCP is rejecting it during a validation step after XPC launch
- registeredPlugInsWithError: is never called by FCP
- Plugin XPC service crashes with NSInvalidArgumentException on unrecognized selector sent to FxPrincipal
Crash detail: Exception: EXC_BREAKPOINT / NSInvalidArgumentException -[%s %s]: unrecognized selector sent to instance Call stack leads to: +[FxPrincipal startServicePrincipal] called from Foundation NSXPCConnection machinery
This suggests FCP 12.2 is calling FxPrincipal methods via XPC that are implemented in the runtime FxPlug.framework but are not being resolved correctly in the plugin process — even when the plugin links directly against /Library/Developer/Frameworks/FxPlug.framework (v4.3.4).
Question: Has FCP 12.2 introduced a new registration requirement, entitlement, or linking requirement for third-party FxPlug plugins that is not yet reflected in the FxPlug SDK documentation or Xcode template?
Is there a known workaround or updated FxPlug template that works with FCP 12.2 on macOS 26?
Any guidance from the FxPlug team would be greatly appreciated.