Changelog

When biometric is enabled, focus the biometric button instead of the

password box on both the main unlock view and the sensitive data overlay.

This lets users press Enter/Space to trigger biometric without having

to click the button manually. Falls back to password box focus when

biometric is not available. Uses PropertyChanged to handle the async

biometric availability check — switches focus to biometric button

as soon as availability is confirmed.

The block struct had Flags = 1 << 25 (BLOCK_HAS_COPY_DISPOSE) but the

descriptor only contained Reserved and Size — no copy/dispose function

pointers. When the ObjC runtime copied the block for async dispatch, it

read garbage memory as the copy helper, corrupting the block and causing

a NullReferenceException when the callback tried to read the Context

GCHandle.

Fixed by:

• Using _NSConcreteGlobalBlock with BLOCK_IS_GLOBAL flag (no copy/dispose)
• Pinning the invoker delegate as a static field (prevents GC collection)
• Making the invoker null-safe with try/catch for native callback safety
• Returning a cleanup Action from EvaluatePolicy so the caller frees

resources after gate.Wait() instead of a racy 2-second Task.Delay

The validation overlay was calling AuthenticateAsync (Touch ID + keychain

read + password validation) when it only needs to verify Touch ID works.

Since the app is already unlocked at this point, there's no need to

retrieve the password from the keychain.

Added VerifyBiometricAsync to IBiometricService — prompts biometric only

with no keychain access. Moved EvaluateBiometricPolicyAsync out of the

DEBUG preprocessor block into the shared section so it's available in

both build configurations. Added logging to trace the verification flow.

Instead of closing the main window and showing the unlock screen when

validating biometric enrollment, the app now displays a frosted glass

overlay at ZIndex 2000 on top of the existing UI. The user sees a

verification prompt: succeed with biometric and it stays enabled, or

enter the master password and biometric gets disabled. The main window

stays open throughout — no shutdown, no window recreation.

Place Exit and Unlock buttons side by side on the lock screen so users

can quit the app without needing to unlock first. Exit uses the

secondary surface style, Unlock retains the primary accent style.