Your AvaloniaUI license does not allow usage in application 'LINQPad9' with bundle identifier ''.

curtjester · August 9

LINQPad 9.9.10 will not start on macOS. It dies during InitAvalonia() with an Avalonia XPF licensing exception before any window appears. 9.8.12 and every earlier 9.x build ran fine on this same machine — the failure started the instant the auto-updater patched 9.8.12 → 9.9.10, and it has been 100% reproducible ever since.

Error

Your AvaloniaUI license does not allow usage in application 'LINQPad9' with bundle identifier ''.
Please add this application to your license and copy an updated key from the Avalonia Portal.

Source=AvaloniaUI.Licensing

 -AvaloniaUI.Licensing.AvaloniaLicenseInformation Void c(System.String) offset: 0x5F
 -AvaloniaUI.Licensing.AvaloniaLicenseInformation Void Validate(System.String, System.String, System.String, System.Nullable`1[System.DateTimeOffset]) offset: 0xF7
 -Atlantis.XpfLicensing Void VerifyProductLicense(System.String) offset: 0x33
 -Atlantis.XpfLicensing Void VerifyXpfApiShimLicense() offset: 0x0
 -AvaloniaUI.Xpf.WinApiShim.WinApiShimSetup Void AddLibrary(System.Reflection.Assembly) offset: 0x0
 -LINQPad.UI.UILoader Void InitAvalonia() offset: 0xDE
 -LINQPad.UI.UILoader Void Start(System.String[]) offset: 0xF3

Logged twice per launch — once under Startup, once under GuiAppHost — then the process exits.

Log file: ~/Library/Application Support/LINQPad/Logs.LINQPad9/log.txt

Root Cause

LINQPad for macOS is built on Avalonia XPF, the commercial WPF-compatibility layer (see AvaloniaUI.Xpf.WinApiShim.Native.dylib in the app bundle). The throw comes from XpfLicensing.VerifyXpfApiShimLicense() — that is LINQPad Pty Ltd's own embedded XPF key, not a user license.

There is no Avalonia license key of any kind on this machine: no AvaloniaUILicenseKey env var, no Directory.Build.props, no portal account. The message's advice to "add this application to your license" is therefore not actionable by a LINQPad user. Only the vendor can fix it.

The empty bundle identifier is a red herring

The installed Contents/Info.plist is correct:

CFBundleIdentifier         = LINQPad9.macos
CFBundleExecutable         = LINQPad9
CFBundleShortVersionString = 9.9.10

Yet the check reports bundle identifier ''. Validation runs inside InitAvalonia(), well before Cocoa/NSBundle is initialised, so it likely reads the identifier too early and passes an empty string to AvaloniaLicenseInformation.Validate(...). Unverified hypothesis — offered to the vendor as a lead, not established fact.

Environment

Name	Data
LINQPad	9.9.10 (ARM64), auto-updated from 9.8.12
macOS	27.0 (build 26A5388g)
Hardware	Apple Silicon (arm64)
.NET runtime	Microsoft.NETCore.App 8.0.2

Workaround

Roll back to 9.8.12 and it opens correctly