From 073535340531a2546ca05327ce97d0b4b3804790 Mon Sep 17 00:00:00 2001
From: savis <106487343+savisxss@users.noreply.github.com>
Date: Sun, 28 Dec 2025 16:44:26 +0100
Subject: [PATCH] Fix SEQUENCE mismatch error in packet validation

---
 src/game/desc.cpp | 7 ++++++-
 src/game/desc.h   | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/game/desc.cpp b/src/game/desc.cpp
index 2f6c450..567babc 100644
--- a/src/game/desc.cpp
+++ b/src/game/desc.cpp
@@ -77,6 +77,8 @@ void DESC::Initialize()
 	m_bChannelStatusRequested = false;
 
 	m_SequenceGenerator.seed(SEQUENCE_SEED);
+	// Pre-generate the first expected sequence to match what client will send
+	m_bNextExpectedSequence = m_SequenceGenerator(UINT8_MAX + 1);
 
 	m_pkLoginKey = NULL;
 	m_dwLoginKey = 0;
@@ -911,7 +913,10 @@ bool DESC::IsAdminMode()
 
 BYTE DESC::GetSequence()
 {
-	return m_SequenceGenerator(UINT8_MAX + 1);
+	// Return the next expected sequence and then generate the one after that
+	BYTE bCurrentExpected = m_bNextExpectedSequence;
+	m_bNextExpectedSequence = m_SequenceGenerator(UINT8_MAX + 1);
+	return bCurrentExpected;
 }
 
 void DESC::SendLoginSuccessPacket()
diff --git a/src/game/desc.h b/src/game/desc.h
index bc81300..1ffb2ca 100644
--- a/src/game/desc.h
+++ b/src/game/desc.h
@@ -226,6 +226,7 @@ class DESC
 		bool			m_bPong;
 
 		pcg32 			m_SequenceGenerator;
+		BYTE			m_bNextExpectedSequence; // Next expected sequence number from client
 
 		CLoginKey *		m_pkLoginKey;
 		DWORD			m_dwLoginKey;