Implement duel request/accept/decline UI and packet handling

- Parse SMSG_DUEL_REQUESTED: store challenger guid/name, set
  pendingDuelRequest_ flag, show chat notification
- Parse SMSG_DUEL_COMPLETE: clear pending flag, notify on cancel
- Parse SMSG_DUEL_WINNER: show "X defeated Y in a duel!" chat message
- Handle SMSG_DUEL_OUTOFBOUNDS with warning message
- Add acceptDuel() method sending CMSG_DUEL_ACCEPTED (new builder)
- Wire forfeitDuel() to clear pendingDuelRequest_ on decline
- Add renderDuelRequestPopup() ImGui window (Accept/Decline buttons)
  positioned near group invite popup; shown when challenge is pending
- Add DuelAcceptPacket builder to world_packets.hpp/cpp

.claude/scheduled_tasks.lock

@@ -0,0 +1 @@
+{"sessionId":"55a28c7e-8043-44c2-9829-702f303c84ba","pid":3880168,"acquiredAt":1773085726967}

include/game/game_handler.hpp

@@ -707,6 +707,12 @@ public:
     bool hasPendingGroupInvite() const { return pendingGroupInvite; }
     const std::string& getPendingInviterName() const { return pendingInviterName; }
 
+    // ---- Duel ----
+    bool hasPendingDuelRequest() const { return pendingDuelRequest_; }
+    const std::string& getDuelChallengerName() const { return duelChallengerName_; }
+    void acceptDuel();
+    // forfeitDuel() already declared at line ~399
+
     // ---- Instance lockouts ----
     struct InstanceLockout {
         uint32_t mapId       = 0;
@@ -1249,6 +1255,9 @@ private:
 
     // ---- Instance lockout handler ----
     void handleRaidInstanceInfo(network::Packet& packet);
+    void handleDuelRequested(network::Packet& packet);
+    void handleDuelComplete(network::Packet& packet);
+    void handleDuelWinner(network::Packet& packet);
 
     // ---- LFG / Dungeon Finder handlers ----
     void handleLfgJoinResult(network::Packet& packet);
@@ -1601,6 +1610,12 @@ private:
     bool pendingGroupInvite = false;
     std::string pendingInviterName;
 
+    // Duel state
+    bool pendingDuelRequest_    = false;
+    uint64_t duelChallengerGuid_= 0;
+    uint64_t duelFlagGuid_      = 0;
+    std::string duelChallengerName_;
+
     // ---- Guild state ----
     std::string guildName_;
     std::vector<std::string> guildRankNames_;

include/game/world_packets.hpp

@@ -1265,6 +1265,12 @@ public:
 // Duel
 // ============================================================
 
+/** CMSG_DUEL_ACCEPTED packet builder (no payload) */
+class DuelAcceptPacket {
+public:
+    static network::Packet build();
+};
+
 /** CMSG_DUEL_CANCELLED packet builder */
 class DuelCancelPacket {
 public:

include/ui/game_screen.hpp

@@ -204,6 +204,7 @@ private:
     void renderCombatText(game::GameHandler& gameHandler);
     void renderPartyFrames(game::GameHandler& gameHandler);
     void renderGroupInvitePopup(game::GameHandler& gameHandler);
+    void renderDuelRequestPopup(game::GameHandler& gameHandler);
     void renderBuffBar(game::GameHandler& gameHandler);
     void renderLootWindow(game::GameHandler& gameHandler);
     void renderGossipWindow(game::GameHandler& gameHandler);

src/game/game_handler.cpp

@@ -1891,8 +1891,22 @@ void GameHandler::handlePacket(network::Packet& packet) {
             handleRaidInstanceInfo(packet);
             break;
         case Opcode::SMSG_DUEL_REQUESTED:
-            // Duel request UI flow not implemented yet.
-            packet.setReadPos(packet.getSize());
+            handleDuelRequested(packet);
+            break;
+        case Opcode::SMSG_DUEL_COMPLETE:
+            handleDuelComplete(packet);
+            break;
+        case Opcode::SMSG_DUEL_WINNER:
+            handleDuelWinner(packet);
+            break;
+        case Opcode::SMSG_DUEL_OUTOFBOUNDS:
+            addSystemChatMessage("You are out of the duel area!");
+            break;
+        case Opcode::SMSG_DUEL_INBOUNDS:
+            // Re-entered the duel area; no special action needed.
+            break;
+        case Opcode::SMSG_DUEL_COUNTDOWN:
+            // Countdown timer — no action needed; server also sends UNIT_FIELD_FLAGS update.
             break;
         case Opcode::SMSG_PARTYKILLLOG:
             // Classic-era packet: killer GUID + victim GUID.
@@ -7023,18 +7037,76 @@ void GameHandler::respondToReadyCheck(bool ready) {
     LOG_INFO("Responded to ready check: ", ready ? "ready" : "not ready");
 }
 
+void GameHandler::acceptDuel() {
+    if (!pendingDuelRequest_ || state != WorldState::IN_WORLD || !socket) return;
+    pendingDuelRequest_ = false;
+    auto pkt = DuelAcceptPacket::build();
+    socket->send(pkt);
+    addSystemChatMessage("You accept the duel.");
+    LOG_INFO("Accepted duel from guid=0x", std::hex, duelChallengerGuid_, std::dec);
+}
+
 void GameHandler::forfeitDuel() {
     if (state != WorldState::IN_WORLD || !socket) {
         LOG_WARNING("Cannot forfeit duel: not in world or not connected");
         return;
     }
-
+    pendingDuelRequest_ = false;  // cancel request if still pending
     auto packet = DuelCancelPacket::build();
     socket->send(packet);
     addSystemChatMessage("You have forfeited the duel.");
     LOG_INFO("Forfeited duel");
 }
 
+void GameHandler::handleDuelRequested(network::Packet& packet) {
+    if (packet.getSize() - packet.getReadPos() < 16) {
+        packet.setReadPos(packet.getSize());
+        return;
+    }
+    duelChallengerGuid_ = packet.readUInt64();
+    duelFlagGuid_       = packet.readUInt64();
+
+    // Resolve challenger name from entity list
+    duelChallengerName_.clear();
+    auto entity = entityManager.getEntity(duelChallengerGuid_);
+    if (auto* unit = dynamic_cast<Unit*>(entity.get())) {
+        duelChallengerName_ = unit->getName();
+    }
+    if (duelChallengerName_.empty()) {
+        char tmp[32];
+        std::snprintf(tmp, sizeof(tmp), "0x%llX",
+                      static_cast<unsigned long long>(duelChallengerGuid_));
+        duelChallengerName_ = tmp;
+    }
+    pendingDuelRequest_ = true;
+
+    addSystemChatMessage(duelChallengerName_ + " challenges you to a duel!");
+    LOG_INFO("SMSG_DUEL_REQUESTED: challenger=0x", std::hex, duelChallengerGuid_,
+             " flag=0x", duelFlagGuid_, std::dec, " name=", duelChallengerName_);
+}
+
+void GameHandler::handleDuelComplete(network::Packet& packet) {
+    if (packet.getSize() - packet.getReadPos() < 1) return;
+    uint8_t started = packet.readUInt8();
+    // started=1: duel began, started=0: duel was cancelled before starting
+    pendingDuelRequest_ = false;
+    if (!started) {
+        addSystemChatMessage("The duel was cancelled.");
+    }
+    LOG_INFO("SMSG_DUEL_COMPLETE: started=", static_cast<int>(started));
+}
+
+void GameHandler::handleDuelWinner(network::Packet& packet) {
+    if (packet.getSize() - packet.getReadPos() < 3) return;
+    /*uint8_t type =*/ packet.readUInt8();  // 0=normal, 1=flee
+    std::string winner = packet.readString();
+    std::string loser  = packet.readString();
+
+    std::string msg = winner + " has defeated " + loser + " in a duel!";
+    addSystemChatMessage(msg);
+    LOG_INFO("SMSG_DUEL_WINNER: winner=", winner, " loser=", loser);
+}
+
 void GameHandler::toggleAfk(const std::string& message) {
     afkStatus_ = !afkStatus_;
     afkMessage_ = message;

src/game/world_packets.cpp

@@ -2083,6 +2083,12 @@ network::Packet ReadyCheckConfirmPacket::build(bool ready) {
 // Duel
 // ============================================================
 
+network::Packet DuelAcceptPacket::build() {
+    network::Packet packet(wireOpcode(Opcode::CMSG_DUEL_ACCEPTED));
+    LOG_DEBUG("Built CMSG_DUEL_ACCEPTED");
+    return packet;
+}
+
 network::Packet DuelCancelPacket::build() {
     network::Packet packet(wireOpcode(Opcode::CMSG_DUEL_CANCELLED));
     LOG_DEBUG("Built CMSG_DUEL_CANCELLED");

src/ui/game_screen.cpp

@@ -396,6 +396,7 @@ void GameScreen::render(game::GameHandler& gameHandler) {
     renderCombatText(gameHandler);
     renderPartyFrames(gameHandler);
     renderGroupInvitePopup(gameHandler);
+    renderDuelRequestPopup(gameHandler);
     renderGuildInvitePopup(gameHandler);
     renderGuildRoster(gameHandler);
     renderBuffBar(gameHandler);
@@ -4376,6 +4377,30 @@ void GameScreen::renderGroupInvitePopup(game::GameHandler& gameHandler) {
     ImGui::End();
 }
 
+void GameScreen::renderDuelRequestPopup(game::GameHandler& gameHandler) {
+    if (!gameHandler.hasPendingDuelRequest()) return;
+
+    auto* window = core::Application::getInstance().getWindow();
+    float screenW = window ? static_cast<float>(window->getWidth()) : 1280.0f;
+
+    ImGui::SetNextWindowPos(ImVec2(screenW / 2 - 150, 250), ImGuiCond_Always);
+    ImGui::SetNextWindowSize(ImVec2(300, 0), ImGuiCond_Always);
+
+    if (ImGui::Begin("Duel Request", nullptr, ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoResize)) {
+        ImGui::Text("%s challenges you to a duel!", gameHandler.getDuelChallengerName().c_str());
+        ImGui::Spacing();
+
+        if (ImGui::Button("Accept", ImVec2(130, 30))) {
+            gameHandler.acceptDuel();
+        }
+        ImGui::SameLine();
+        if (ImGui::Button("Decline", ImVec2(130, 30))) {
+            gameHandler.forfeitDuel();
+        }
+    }
+    ImGui::End();
+}
+
 void GameScreen::renderGuildInvitePopup(game::GameHandler& gameHandler) {
     if (!gameHandler.hasPendingGuildInvite()) return;