We are developing GateCall, an iOS application that uses a Call Directory extension to maintain a private, user-selected list of blocked telephone numbers. We are seeking clarification about Call Directory blocking precedence on iOS 27.0.1, particularly when a number exists in Contacts or outgoing Recents. Test environment Physical iPhone 11 Pro Max running iOS 27.0.1. Call Directory extension enabled in Settings. Blocking entry: a valid Canadian telephone number normalized to E.164 and submitted as an Int64. CXCallDirectoryManager.reloadExtension returned successful completion. The application reported synchronization of one blocking entry. Actual extension-loaded entry count has not been independently verified. Observed sequence — November 1, 2026 The target number was initially present in iPhone Contacts. At 2:01 PM, the application reported successful Call Directory synchronization. At 2:06 PM, the iPhone placed an outgoing call to the target number. At 2:16 PM, an incoming cellular call from the same number caused the iPhone to ring. The call subsequently appeared in Phone → Recents as a missed call. We reviewed the September 2025 Apple DTS discussion: https://developer.apple.com/forums/thread/800415 That discussion describes a caller-information priority hierarchy and changes in iOS 26 affecting outgoing Recents. Questions Does iOS 27.0.1 intentionally prioritize Contacts and outgoing Recents over explicit blocking entries supplied by a third-party Call Directory extension? Is there a supported public API or configuration that allows a user-selected Call Directory block to take precedence over those sources? Is this priority behaviour documented or expected to change in future iOS releases? Is there a supported diagnostic mechanism to verify which blocking entries were actually loaded by iOS, beyond successful extension reload completion? We understand that a successful reload does not independently prove that a particular number was loaded or that Call Directory caused the observed behaviour. Our objective is to implement accurate, user-controlled blocking and avoid claiming protection that the operating system cannot guarantee. Any clarification from Apple DTS or developers with recent iOS 27 experience would be appreciated.