From 42816d4272e2d942fd7b35517a8cdf46131f52bd Mon Sep 17 00:00:00 2001
From: Tom Brow <tomb@block.xyz>
Date: Tue, 13 Oct 2026 09:41:57 -0700
Subject: [PATCH] fix(ios): preserve navigation for empty reply markers

Signed-off-by: Tom Brow <tomb@block.xyz>
---
 .../BuzzPushKit/BuzzPushNavigationTarget.swift | 13 +++++++++++++
 .../BuzzPushNotificationResolver.swift         | 11 +----------
 .../BuzzPushNavigationTargetTests.swift        | 18 ++++++++++++++++++
 3 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/mobile/ios/BuzzPushKit/Sources/BuzzPushKit/BuzzPushNavigationTarget.swift b/mobile/ios/BuzzPushKit/Sources/BuzzPushKit/BuzzPushNavigationTarget.swift
index dccf62c6a9..2c6605719a 100644
--- a/mobile/ios/BuzzPushKit/Sources/BuzzPushKit/BuzzPushNavigationTarget.swift
+++ b/mobile/ios/BuzzPushKit/Sources/BuzzPushKit/BuzzPushNavigationTarget.swift
@@ -31,6 +31,19 @@ public struct BuzzPushNavigationTarget: Codable, Equatable, Sendable {
     return value
   }
 
+  static func threadRootID(in tags: [[String]]) -> String? {
+    // Inbox opens broadcast replies in the channel and other replies in their
+    // direct parent's thread, even when the NIP-10 root names an outer thread.
+    if tags.contains(where: { $0.count >= 2 && $0[0] == "broadcast" && $0[1] == "1" }) {
+      return nil
+    }
+    let parent = tags.last(where: { $0.count >= 4 && $0[0] == "e" && $0[3] == "reply" })?[1]
+    // Relay ingest ignores malformed reply IDs. An empty marker must not
+    // invalidate the otherwise usable channel/event navigation payload.
+    guard let parent, !parent.isEmpty else { return nil }
+    return parent
+  }
+
   /// Decodes a target without trusting other fields from the APNs payload.
   public static func decodeIfPresent(
     from userInfo: [AnyHashable: Any]
diff --git a/mobile/ios/BuzzPushKit/Sources/BuzzPushKit/BuzzPushNotificationResolver.swift b/mobile/ios/BuzzPushKit/Sources/BuzzPushKit/BuzzPushNotificationResolver.swift
index 5fd9f30876..d195748021 100644
--- a/mobile/ios/BuzzPushKit/Sources/BuzzPushKit/BuzzPushNotificationResolver.swift
+++ b/mobile/ios/BuzzPushKit/Sources/BuzzPushKit/BuzzPushNotificationResolver.swift
@@ -463,7 +463,7 @@ public final class BuzzPushNotificationResolver: BuzzPushNotificationResolving {
           eventID: event.id,
           communityID: community.id,
           channelID: $0,
-          threadRootID: navigationThreadRootID(event)
+          threadRootID: BuzzPushNavigationTarget.threadRootID(in: event.tags)
         )
       },
       senderPubkey: event.pubkey.lowercased(),
@@ -474,15 +474,6 @@ public final class BuzzPushNotificationResolver: BuzzPushNotificationResolving {
     )
   }
 
-  private static func navigationThreadRootID(_ event: VerifiedNostrEvent) -> String? {
-    // Inbox opens broadcast replies in the channel and other replies in their
-    // direct parent's thread, even when the NIP-10 root names an outer thread.
-    if event.tags.contains(where: { $0.count >= 2 && $0[0] == "broadcast" && $0[1] == "1" }) {
-      return nil
-    }
-    return event.tags.last(where: { $0.count >= 4 && $0[0] == "e" && $0[3] == "reply" })?[1]
-  }
-
   private static func ephemeralProfile(
     event: VerifiedNostrEvent,
     communityID: String,
diff --git a/mobile/ios/BuzzPushKit/Tests/BuzzPushKitTests/BuzzPushNavigationTargetTests.swift b/mobile/ios/BuzzPushKit/Tests/BuzzPushKitTests/BuzzPushNavigationTargetTests.swift
index f02e35770a..660945eb6d 100644
--- a/mobile/ios/BuzzPushKit/Tests/BuzzPushKitTests/BuzzPushNavigationTargetTests.swift
+++ b/mobile/ios/BuzzPushKit/Tests/BuzzPushKitTests/BuzzPushNavigationTargetTests.swift
@@ -103,3 +103,21 @@ import Testing
     ) == nil)
   }
 }
+
+@Test func `Empty reply marker preserves channel navigation`() {
+  let thread = BuzzPushNavigationTarget.threadRootID(in: [["e", "", "", "reply"]])
+  #expect(thread == nil)
+  let target = BuzzPushNavigationTarget(
+    eventID: "message", communityID: "community", channelID: "channel", threadRootID: thread
+  )
+  #expect(BuzzPushNavigationTarget.decodeIfPresent(
+    from: [BuzzPushNavigationTarget.userInfoKey: target.userInfoValue]
+  ) == target)
+}
+
+@Test func `Thread destination keeps direct parent and broadcast semantics`() {
+  let tags = [["e", "outer-root", "", "root"], ["e", "direct-parent", "", "reply"]]
+  #expect(BuzzPushNavigationTarget.threadRootID(in: tags) == "direct-parent")
+  #expect(BuzzPushNavigationTarget.threadRootID(in: tags + [["broadcast", "1"]]) == nil)
+  #expect(BuzzPushNavigationTarget.threadRootID(in: [["e", "outer-root", "", "root"]]) == nil)
+}