From 5fcbde8803bb33dba8dba3d9ed38dd1d5ea21a15 Mon Sep 17 00:00:00 2001
From: Brandon McAnsh <git@bmcreations.dev>
Date: Mon, 27 Jul 2026 16:23:57 -0400
Subject: [PATCH 1/2] fix(tips): pad tip code payload reserved bytes with a
 non-zero sentinel

The tip payload left the reserved trailing bytes (17-19) zero. KikCodes.decode
strips trailing zero bytes, so a frame whose reserved region (or user id tail)
is zero comes back short. Fill the reserved region with incrementing digits
(1, 2, 3) on encode so the frame always ends non-zero and round-trips at full
length. Decoding still re-pads for legacy zero-trailing frames. Mirrors
Android #1163.
---
 .../Main/Bill/TipCode.Payload+Encoding.swift   | 17 +++++++++++++++--
 FlipcashTests/TipCodeEncodingTests.swift       | 18 ++++++++++++++----
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/Flipcash/Core/Screens/Main/Bill/TipCode.Payload+Encoding.swift b/Flipcash/Core/Screens/Main/Bill/TipCode.Payload+Encoding.swift
index 96fb40b1..0e8729ff 100644
--- a/Flipcash/Core/Screens/Main/Bill/TipCode.Payload+Encoding.swift
+++ b/Flipcash/Core/Screens/Main/Bill/TipCode.Payload+Encoding.swift
@@ -17,13 +17,22 @@ nonisolated extension TipCode.Payload {
 
     private static let userIDRange = 1..<17
 
+    /// The trailing reserved bytes, filled with a non-zero sentinel on encode.
+    private static let reservedRange = 17..<length
+
+    /// Incrementing digits written into `reservedRange` so the frame always ends
+    /// non-zero — `KikCodes.decode` strips trailing zero bytes, so a zero-filled
+    /// reserved region (or a user id ending in zeros) comes back short.
+    private static let reservedFill: [UInt8] = [1, 2, 3]
+
     init(data: Data) throws {
         guard !data.isEmpty, data.count <= Self.length else {
             throw Error.invalidDataSize
         }
 
-        // `KikCodes.decode` drops trailing zero bytes, so a user id ending in
-        // zeros comes back short. Restore the fixed frame before reading it.
+        // `KikCodes.decode` drops trailing zero bytes, so a frame that ends in
+        // zeros comes back short. Restore the fixed frame before reading it —
+        // still required for legacy frames encoded before the reserved fill.
         var bytes = Data(data)
         bytes.append(Data(count: Self.length - bytes.count))
 
@@ -39,6 +48,10 @@ nonisolated extension TipCode.Payload {
         var data = Data(count: Self.length)
         data[0] = Self.kind
         data.replaceSubrange(Self.userIDRange, with: userID.data)
+        // Fill the reserved trailing region with a non-zero sentinel so the
+        // frame survives the scannable code at full length regardless of the
+        // user id's trailing bytes. Decoding ignores this region.
+        data.replaceSubrange(Self.reservedRange, with: Self.reservedFill)
         return data
     }
 
diff --git a/FlipcashTests/TipCodeEncodingTests.swift b/FlipcashTests/TipCodeEncodingTests.swift
index cdac55d3..aef70e52 100644
--- a/FlipcashTests/TipCodeEncodingTests.swift
+++ b/FlipcashTests/TipCodeEncodingTests.swift
@@ -52,12 +52,19 @@ struct TipCodeEncodingTests {
         #expect(try TipCode.Payload(data: scanned) == payload)
     }
 
-    @Test("A zero-stripped frame decodes to the same user id")
+    /// The encoder now fills the reserved region with a non-zero sentinel, so a
+    /// freshly-encoded frame never ends in zeros. This still has to hold for a
+    /// legacy frame (zero reserved region) whose trailing zeros the scannable
+    /// code strips — reconstruct one explicitly rather than from `encode()`.
+    @Test("A zero-stripped legacy frame decodes to the same user id")
     func decodesAZeroStrippedFrame() throws {
         let userID = UUID(uuidString: "3f2504e0-4f89-41d3-9a0c-000000000000")!
         let payload = TipCode.Payload(userID: userID)
 
+        // Zero the reserved region back out to mimic a pre-fill encoder, then
+        // drop the trailing zeros the way `KikCodes.decode` would.
         var truncated = payload.encode()
+        truncated.replaceSubrange(17..<TipCode.Payload.length, with: [0, 0, 0])
         while truncated.last == 0 { truncated.removeLast() }
 
         #expect(truncated.count < TipCode.Payload.length)
@@ -74,12 +81,15 @@ struct TipCodeEncodingTests {
         #expect(encoded.count == CashCode.Payload.length)
     }
 
-    @Test("The trailing bytes are reserved and zeroed", arguments: TipCodeEncodingTests.userIDs)
-    func reservedBytesAreZero(userID: UUID) {
+    /// The reserved trailing bytes are filled with a non-zero sentinel (1, 2, 3)
+    /// rather than left zero, so the frame always ends non-zero and survives the
+    /// scannable code — `KikCodes.decode` strips trailing zeros.
+    @Test("The trailing bytes carry the reserved non-zero fill", arguments: TipCodeEncodingTests.userIDs)
+    func reservedBytesCarryFill(userID: UUID) {
         let encoded = TipCode.Payload(userID: userID).encode()
 
         #expect(encoded[0] == TipCode.Payload.kind)
-        #expect(encoded[17...].allSatisfy { $0 == 0 })
+        #expect(Data(encoded[17...]) == Data([1, 2, 3]))
     }
 
     // MARK: - Rejection -

From 3c9d7ff6b5a67cd90c22b56d188cfc2d587f587d Mon Sep 17 00:00:00 2001
From: Brandon McAnsh <git@bmcreations.dev>
Date: Mon, 27 Jul 2026 16:59:58 -0400
Subject: [PATCH 2/2] fix(chat): restore dropped comma when merging code/main
 into the tip payload branch

The #524 (focusOnAppear) and #525 (isTipDm) conversation-bar params were
integrated on main without a separator between them, leaving
ConversationScreen and ChatScreenRepresentable non-compiling. Add the missing
commas so the tree builds.
---
 .../Core/Screens/Conversation/ChatScreenRepresentable.swift     | 2 +-
 Flipcash/Core/Screens/Conversation/ConversationScreen.swift     | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Flipcash/Core/Screens/Conversation/ChatScreenRepresentable.swift b/Flipcash/Core/Screens/Conversation/ChatScreenRepresentable.swift
index 1d38c0fa..1cd72b0e 100644
--- a/Flipcash/Core/Screens/Conversation/ChatScreenRepresentable.swift
+++ b/Flipcash/Core/Screens/Conversation/ChatScreenRepresentable.swift
@@ -102,7 +102,7 @@ struct ChatScreenRepresentable: UIViewControllerRepresentable {
                 symbol: symbol,
                 onSendCash: onSendCash,
                 model: barModel,
-                focusOnAppear: focusOnAppear
+                focusOnAppear: focusOnAppear,
                 isTipDm: isTipDm
             )
             .environment(conversationController)
diff --git a/Flipcash/Core/Screens/Conversation/ConversationScreen.swift b/Flipcash/Core/Screens/Conversation/ConversationScreen.swift
index 0865f6c9..ba3ec93d 100644
--- a/Flipcash/Core/Screens/Conversation/ConversationScreen.swift
+++ b/Flipcash/Core/Screens/Conversation/ConversationScreen.swift
@@ -172,7 +172,7 @@ struct ConversationScreen: View {
             onSendCash: sendCash,
             conversationController: conversationController,
             barModel: barModel,
-            focusOnAppear: openKeyboard
+            focusOnAppear: openKeyboard,
             isTipDm: tipCounterpart != nil
         )
         .ignoresSafeArea(.keyboard)