#1 - quicr module

modules/server/src/ZoneManager.cpp

@@ -68,6 +68,8 @@ void ZoneManager::on_player_move(SessionId session_id, mmo::PlayerMoveMessage&&
     entt::entity entity = client_entity(session_id);
     if (entity == entt::null) return;
 
+    m_session_input_frame[session_id] = message.frame_idx();
+
     auto* controller = m_world->registry().try_get<CharacterController>(entity);
     if (controller) {
         controller->set_input(
@@ -97,6 +99,11 @@ const im::Interest* ZoneManager::get_interest(im::InterestId id) const {
     return m_interest_system->get_interest(id);
 }
 
+uint32_t ZoneManager::acked_input_frame(im::InterestId interest_id) const {
+    auto it = m_session_acked_frame.find(interest_id);
+    return it != m_session_acked_frame.end() ? it->second : 0;
+}
+
 // ── Private helpers ───────────────────────────────────────────────────────────
 
 void ZoneManager::check_neighbor_transfers() {
@@ -169,9 +176,25 @@ void ZoneManager::tick(uint32_t frame_idx, float delta_time) {
     m_world->step(delta_time);
     FrameMarkEnd("World step");
 
+    // Re-stamp each client entity's newest input onto the server's frame index.
+    // The input ring is keyed by client frame numbers (independent counter),
+    // but physics lookup uses the server's frame counter. By re-stamping onto
+    // the server frame, input(server_frame_idx) resolves by exact match rather
+    // than fallback, ensuring deterministic and correct input consumption.
+    for (const auto& [interest_id, entity] : m_client_entities) {
+        auto* controller = m_world->registry().try_get<CharacterController>(entity);
+        if (!controller) continue;
+        controller->set_input(frame_idx, controller->input());
+    }
+
     FrameMarkStart("Physics step");
-    m_physics_world.step(frame_idx, delta_time);
+    // Fixed step, not the measured interval: the simulation has to advance by the
+    // same amount every frame for a replay of the same inputs to land in the same
+    // place.
+    m_physics_world.step(frame_idx, JoltPhysicsWorld::FIXED_DELTA_TIME);
     FrameMarkEnd("Physics step");
+
+    m_session_acked_frame = m_session_input_frame;
 }
 
 } // namespace tw::net