A signed DriverKit extension fails OSSystemExtensionRequest activation on macOS 26.4.1. The user-facing error is OSSystemExtensionErrorDomain code 4 ("Extension not found in App bundle") — but the dext is in the bundle, the identifier matches, and sysextd confirms it received the request: sysextd: [com.apple.sx:XPC] client activation request for com.arqitekta.bluefield.rshim.driver sysextd: attempting to realize extension with identifier com.arqitekta.bluefield.rshim.driver …and then nothing further. systemextensionsctl list reports 0 extensions. Question: Which log subsystem/category surfaces the kernel-side reason that sysextd aborts after "attempting to realize"? com.apple.sx only shows the request was accepted; whatever vetoes the realize step isn't in that subsystem (or isn't at info/debug level). Is there a separate predicate for the kernelmanagerd / dext-loading path I should be capturing? Environment: macOS 26.4.1 (25E253), Apple Silicon Mac Studio Xcode 26.2 (17C52), DriverKit SDK 25.2 SIP disabled, systemextensionsctl developer on Apple Developer Program, signed "Apple Development: …" DriverKit entitlement request 264CFJJU36 approved; profile includes com.apple.developer.driverkit, allow-any-userclient-access, transport.pci Already verified: Dext at Contents/Library/SystemExtensions/RshimDriver.dext CFBundleIdentifier matches the request, CFBundlePackageType=DEXT codesign --verify --deep --strict passes on app + dext embedded.provisionprofile parses, contains the expected entitlements Three IOKitPersonalities (BF2 / BF2-alt / BF3) using Apple's placeholder IOPCIPrimaryMatch Installer app entitled with com.apple.developer.system-extension.install only spctl -a -vv on the dext reports "rejected" — expected for development signing, should be bypassed under developer mode Minimal repro: https://github.com/jfabienke/bluefield-macos-toolkit/tree/dev-stub-entitlements/rshim-dext — build.sh produces the failing app dext. Captured artefacts (build output, embedded profile dump, signing report, repro shell script) under rshim-dext/dts-artifacts/. Looking for either (a) the right log show predicate to find the actual refusal reason, or (b) an environmental requirement on macOS 26 I'm missing.