working

42.13/media/lua/client/Landtrain/LandtrainTowSyncClient.lua

@@ -0,0 +1,93 @@
+if isServer() then return end
+
+if not TowBarMod then TowBarMod = {} end
+TowBarMod.Landtrain = TowBarMod.Landtrain or {}
+if TowBarMod.Landtrain._towSyncClientLoaded then return end
+TowBarMod.Landtrain._towSyncClientLoaded = true
+
+local function log(msg)
+    print("[Landtrain][TowSyncClient] " .. tostring(msg))
+end
+
+local function ensureAttachment(vehicle, attachmentId)
+    if not vehicle or not attachmentId then return false end
+
+    local script = vehicle:getScript()
+    if not script then return false end
+    if script:getAttachmentById(attachmentId) ~= nil then return true end
+
+    local wheelCount = script:getWheelCount()
+    local yOffset = -0.5
+    if wheelCount > 0 then
+        local wheel = script:getWheel(0)
+        if wheel and wheel:getOffset() then
+            yOffset = wheel:getOffset():y() + 0.1
+        end
+    end
+
+    local chassis = script:getPhysicsChassisShape()
+    if not chassis then return false end
+
+    local attach = ModelAttachment.new(attachmentId)
+    if attachmentId == "trailer" then
+        attach:getOffset():set(0, yOffset, -chassis:z() / 2 - 0.1)
+        attach:setZOffset(-1)
+    else
+        attach:getOffset():set(0, yOffset, chassis:z() / 2 + 0.1)
+        attach:setZOffset(1)
+    end
+    script:addAttachment(attach)
+    return true
+end
+
+local function resolveVehicle(id)
+    if not id then return nil end
+    return getVehicleById(id)
+end
+
+local function applyAttachSync(args)
+    if not args then return end
+
+    local vehicleA = resolveVehicle(args.vehicleA)
+    local vehicleB = resolveVehicle(args.vehicleB)
+    if not vehicleA or not vehicleB then return end
+
+    if vehicleA:getVehicleTowing() == vehicleB and vehicleB:getVehicleTowedBy() == vehicleA then
+        return
+    end
+
+    local attachmentA = args.attachmentA or "trailer"
+    local attachmentB = args.attachmentB or "trailerfront"
+    if not ensureAttachment(vehicleA, attachmentA) or not ensureAttachment(vehicleB, attachmentB) then
+        log("attach sync skipped: missing attachment A=" .. tostring(attachmentA) .. " B=" .. tostring(attachmentB))
+        return
+    end
+
+    vehicleA:addPointConstraint(nil, vehicleB, attachmentA, attachmentB)
+end
+
+local function safeBreak(vehicle)
+    if not vehicle then return end
+    if vehicle:getVehicleTowing() == nil and vehicle:getVehicleTowedBy() == nil then return end
+    vehicle:breakConstraint(true, true)
+end
+
+local function applyDetachSync(args)
+    if not args then return end
+    safeBreak(resolveVehicle(args.vehicleA))
+    safeBreak(resolveVehicle(args.vehicleB))
+end
+
+local function onServerCommand(module, command, args)
+    if module ~= "landtrain" then return end
+
+    if command == "forceAttachSync" then
+        applyAttachSync(args)
+    elseif command == "forceDetachSync" then
+        applyDetachSync(args)
+    end
+end
+
+Events.OnServerCommand.Add(onServerCommand)
+
+log("LandtrainTowSyncClient loaded")

42.13/media/lua/client/Landtrain/LandtrainTowbarChainsRebuild.lua

@@ -0,0 +1,651 @@
+if not TowBarMod then TowBarMod = {} end
+TowBarMod.Landtrain = TowBarMod.Landtrain or {}
+if TowBarMod.Landtrain._rebuildLoaded then return end
+TowBarMod.Landtrain._rebuildLoaded = true
+
+TowBarMod.Utils = TowBarMod.Utils or {}
+TowBarMod.UI = TowBarMod.UI or {}
+TowBarMod.Hook = TowBarMod.Hook or {}
+
+local LT = TowBarMod.Landtrain
+local MAX_DIST_SQ = 3.25
+local MAX_DZ = 0.9
+local tmpA = Vector3f.new()
+local tmpB = Vector3f.new()
+
+local function log(msg)
+    print("[Landtrain] " .. tostring(msg))
+    if type(writeLog) == "function" then
+        pcall(writeLog, "Landtrain", "[Landtrain] " .. tostring(msg))
+    end
+end
+
+local function hasAttachment(vehicle, attachmentId)
+    if vehicle == nil or attachmentId == nil then return false end
+    local script = vehicle:getScript()
+    return script ~= nil and script:getAttachmentById(attachmentId) ~= nil
+end
+
+local function sideFree(vehicle, attachmentId)
+    if vehicle == nil then return false end
+    if attachmentId == "trailer" then return vehicle:getVehicleTowing() == nil end
+    if attachmentId == "trailerfront" then return vehicle:getVehicleTowedBy() == nil end
+    return true
+end
+
+local function wouldCreateTowLoop(towingVehicle, towedVehicle)
+    if towingVehicle == nil or towedVehicle == nil then return false end
+    if towingVehicle == towedVehicle or towingVehicle:getId() == towedVehicle:getId() then return true end
+
+    local visited = {}
+    local cursor = towedVehicle
+    while cursor do
+        local id = cursor:getId()
+        if visited[id] then return true end
+        if id == towingVehicle:getId() then return true end
+        visited[id] = true
+        cursor = cursor:getVehicleTowing()
+    end
+
+    visited = {}
+    cursor = towingVehicle
+    while cursor do
+        local id = cursor:getId()
+        if visited[id] then return true end
+        if id == towedVehicle:getId() then return true end
+        visited[id] = true
+        cursor = cursor:getVehicleTowedBy()
+    end
+
+    return false
+end
+
+local function closeEnoughFallback(vehicleA, vehicleB, attachmentA, attachmentB)
+    local posA = vehicleA:getAttachmentWorldPos(attachmentA, tmpA)
+    local posB = vehicleB:getAttachmentWorldPos(attachmentB, tmpB)
+    if not posA or not posB then return false end
+    local dx = posA:x() - posB:x()
+    local dy = posA:y() - posB:y()
+    local dz = posA:z() - posB:z()
+    local distSq = dx * dx + dy * dy + dz * dz
+    return distSq <= MAX_DIST_SQ and math.abs(dz) <= MAX_DZ
+end
+
+local function canTowByLandtrain(vehicleA, vehicleB, attachmentA, attachmentB, allowOccupiedSides)
+    if not vehicleA or not vehicleB or vehicleA == vehicleB then return false end
+    if wouldCreateTowLoop(vehicleA, vehicleB) then return false end
+    if not hasAttachment(vehicleA, attachmentA) or not hasAttachment(vehicleB, attachmentB) then return false end
+    if not allowOccupiedSides and (not sideFree(vehicleA, attachmentA) or not sideFree(vehicleB, attachmentB)) then return false end
+    if vehicleA:getVehicleTowing() == vehicleB or vehicleA:getVehicleTowedBy() == vehicleB then return false end
+
+    if vehicleA:canAttachTrailer(vehicleB, attachmentA, attachmentB) then return true end
+
+    local eitherLinked = vehicleA:getVehicleTowing() ~= nil or vehicleA:getVehicleTowedBy() ~= nil
+        or vehicleB:getVehicleTowing() ~= nil or vehicleB:getVehicleTowedBy() ~= nil
+    return eitherLinked and closeEnoughFallback(vehicleA, vehicleB, attachmentA, attachmentB)
+end
+
+local function resolvePair(towingVehicle, towedVehicle, preferredA, preferredB)
+    local pairs = {
+        { preferredA, preferredB },
+        { towingVehicle and towingVehicle:getTowAttachmentSelf() or nil, towedVehicle and towedVehicle:getTowAttachmentSelf() or nil },
+        { "trailer", "trailerfront" },
+        { "trailerfront", "trailer" }
+    }
+
+    for _, pair in ipairs(pairs) do
+        local a, b = pair[1], pair[2]
+        if a and b and a ~= b and canTowByLandtrain(towingVehicle, towedVehicle, a, b, true) then
+            return a, b
+        end
+    end
+
+    for _, pair in ipairs(pairs) do
+        local a, b = pair[1], pair[2]
+        if a and b and a ~= b and hasAttachment(towingVehicle, a) and hasAttachment(towedVehicle, b) then
+            return a, b
+        end
+    end
+
+    return "trailer", "trailerfront"
+end
+
+local function clearChangedOffset(vehicle)
+    if not vehicle then return end
+    local md = vehicle:getModData()
+    if not md or md["isChangedTowedAttachment"] ~= true then return end
+
+    local script = vehicle:getScript()
+    local changedId = md["towBarChangedAttachmentId"] or vehicle:getTowAttachmentSelf()
+    local attachment = script and script:getAttachmentById(changedId) or nil
+    if attachment then
+        local offset = attachment:getOffset()
+        local storedShift = tonumber(md["towBarChangedOffsetZShift"])
+        if storedShift ~= nil then
+            attachment:getOffset():set(offset:x(), offset:y(), offset:z() - storedShift)
+        else
+            local zShift = offset:z() > 0 and -1 or 1
+            attachment:getOffset():set(offset:x(), offset:y(), offset:z() + zShift)
+        end
+    end
+
+    md["isChangedTowedAttachment"] = false
+    md["towBarChangedAttachmentId"] = nil
+    md["towBarChangedOffsetZShift"] = nil
+    vehicle:transmitModData()
+end
+
+local function applyRigidTow(towingVehicle, towedVehicle, attachmentA, attachmentB)
+    if not TowBarMod.Utils or not TowBarMod.Utils.updateAttachmentsForRigidTow then return end
+    clearChangedOffset(towedVehicle)
+    TowBarMod.Utils.updateAttachmentsForRigidTow(towingVehicle, towedVehicle, attachmentA, attachmentB)
+end
+
+local function setTowBarModelVisible(vehicle, isVisible)
+    if not vehicle then return end
+    local part = vehicle:getPartById("towbar")
+    if part == nil then return end
+
+    for j = 0, 23 do
+        part:setModelVisible("towbar" .. j, false)
+    end
+
+    if isVisible then
+        local script = vehicle:getScript()
+        if script then
+            local scale = script:getModelScale()
+            if scale >= 1.5 and scale <= 2 then
+                local z = script:getPhysicsChassisShape():z() / 2 - 0.1
+                local index = math.floor((z * 2 / 3 - 1) * 10)
+                if index < 0 then index = 0 end
+                if index > 23 then index = 23 end
+                part:setModelVisible("towbar" .. index, true)
+            end
+        end
+    end
+
+    vehicle:doDamageOverlay()
+end
+
+local function refreshTowBarState(vehicle)
+    if not vehicle then return end
+    local md = vehicle:getModData()
+    if not md then return end
+
+    local front = vehicle:getVehicleTowedBy()
+    local rear = vehicle:getVehicleTowing()
+
+    local isTowed = false
+    if front then
+        local frontMd = front:getModData()
+        if md["towed"] == true or (frontMd and frontMd["isTowingByTowBar"] == true) then
+            isTowed = true
+        end
+    end
+
+    local isTowing = false
+    if rear then
+        local rearMd = rear:getModData()
+        if rearMd and rearMd["towed"] == true and rearMd["isTowingByTowBar"] == true then
+            isTowing = true
+        end
+    end
+
+    md["towed"] = isTowed
+    md["isTowingByTowBar"] = isTowed or isTowing
+    vehicle:transmitModData()
+end
+
+local function refreshAround(vehicle)
+    if not vehicle then return end
+    refreshTowBarState(vehicle)
+    refreshTowBarState(vehicle:getVehicleTowedBy())
+    refreshTowBarState(vehicle:getVehicleTowing())
+end
+
+local function restoreDefaultsIfLeadLost(vehicle)
+    if not vehicle then return end
+    local md = vehicle:getModData()
+    if not md then return end
+    if vehicle:getVehicleTowedBy() ~= nil then return end
+    if md["towed"] ~= true and md.towBarOriginalMass == nil and md.towBarOriginalBrakingForce == nil then return end
+
+    if md.towBarOriginalScriptName then vehicle:setScriptName(md.towBarOriginalScriptName) end
+    if md.towBarOriginalMass ~= nil then vehicle:setMass(md.towBarOriginalMass) end
+    if md.towBarOriginalBrakingForce ~= nil then vehicle:setBrakingForce(md.towBarOriginalBrakingForce) end
+    vehicle:constraintChanged()
+    vehicle:updateTotalMass()
+
+    md["towed"] = false
+    md.towBarOriginalScriptName = nil
+    md.towBarOriginalMass = nil
+    md.towBarOriginalBrakingForce = nil
+    if vehicle:getVehicleTowing() == nil then
+        md["isTowingByTowBar"] = false
+    end
+    vehicle:transmitModData()
+
+    setTowBarModelVisible(vehicle, false)
+end
+
+local function queueAction(playerObj, delay, fn, arg)
+    if not playerObj or not fn then return end
+    if TowBarScheduleAction == nil then
+        fn(playerObj, arg)
+        return
+    end
+    ISTimedActionQueue.add(TowBarScheduleAction:new(playerObj, delay or 10, fn, arg))
+end
+
+local function sendAttach(playerObj, towingVehicle, towedVehicle, attachmentA, attachmentB)
+    if not playerObj or not towingVehicle or not towedVehicle then return end
+    if towingVehicle:getId() == towedVehicle:getId() then return end
+
+    sendClientCommand(playerObj, "vehicle", "attachTrailer", {
+        vehicleA = towingVehicle:getId(),
+        vehicleB = towedVehicle:getId(),
+        attachmentA = attachmentA,
+        attachmentB = attachmentB
+    })
+
+    if TowBarMod.Hook and TowBarMod.Hook.setVehiclePostAttach then
+        queueAction(playerObj, 10, TowBarMod.Hook.setVehiclePostAttach, towedVehicle)
+    end
+end
+
+local function captureFrontLink(middleVehicle)
+    if not middleVehicle then return nil end
+    local frontVehicle = middleVehicle:getVehicleTowedBy()
+    if not frontVehicle or frontVehicle == middleVehicle then return nil end
+    local a, b = resolvePair(frontVehicle, middleVehicle)
+    return { front = frontVehicle, middle = middleVehicle, a = a, b = b }
+end
+
+local function restoreFrontLink(playerObj, link)
+    if not link then return end
+    local front = link.front
+    local middle = link.middle
+    if not front or not middle then return end
+    if middle:getVehicleTowedBy() ~= nil then return end
+    if front == middle or front:getId() == middle:getId() then return end
+    if wouldCreateTowLoop(front, middle) then return end
+
+    local a, b = resolvePair(front, middle, link.a, link.b)
+    if not hasAttachment(front, a) or not hasAttachment(middle, b) then return end
+
+    applyRigidTow(front, middle, a, b)
+    middle:setScriptName("notTowingA_Trailer")
+    sendAttach(playerObj, front, middle, a, b)
+
+    local frontMd = front:getModData()
+    local middleMd = middle:getModData()
+    if frontMd then
+        frontMd["isTowingByTowBar"] = true
+        front:transmitModData()
+    end
+    if middleMd then
+        middleMd["isTowingByTowBar"] = true
+        middleMd["towed"] = true
+        middle:transmitModData()
+    end
+
+    setTowBarModelVisible(middle, true)
+    refreshAround(front)
+    refreshAround(middle)
+end
+
+local function queueRestoreFront(playerObj, link, delay)
+    if not playerObj or not link then return end
+    queueAction(playerObj, delay or 12, function(character, linkArg)
+        restoreFrontLink(character, linkArg)
+    end, link)
+end
+
+local function resolveDetachPair(towingVehicle, towedVehicle)
+    local resolvedTowing = towingVehicle
+    local resolvedTowed = resolvedTowing and resolvedTowing:getVehicleTowing() or nil
+
+    if resolvedTowed == nil and towedVehicle and towedVehicle:getVehicleTowedBy() then
+        resolvedTowing = towedVehicle:getVehicleTowedBy()
+        resolvedTowed = towedVehicle
+    elseif resolvedTowed == nil then
+        resolvedTowed = towedVehicle
+    end
+
+    if resolvedTowing == nil and resolvedTowed then
+        resolvedTowing = resolvedTowed:getVehicleTowedBy()
+    end
+
+    if resolvedTowing and resolvedTowed and resolvedTowed:getVehicleTowedBy() ~= resolvedTowing then
+        local directRear = resolvedTowing:getVehicleTowing()
+        if directRear and directRear:getVehicleTowedBy() == resolvedTowing then
+            resolvedTowed = directRear
+        else
+            return nil, nil
+        end
+    end
+
+    return resolvedTowing, resolvedTowed
+end
+
+local function getDetachAction()
+    return TowBarMod.Hook and (TowBarMod.Hook.deattachTowBarAction or TowBarMod.Hook.detachTowBarAction) or nil
+end
+
+local function getPerformDetachHook()
+    return TowBarMod.Hook and (TowBarMod.Hook.performDetachTowBar or TowBarMod.Hook.performDeattachTowBar) or nil
+end
+
+local function getLandtrainHookTypeVariants(vehicleA, vehicleB, hasTowBar)
+    local variants = {}
+    if not hasTowBar or not vehicleA or not vehicleB or vehicleA == vehicleB then return variants end
+
+    if canTowByLandtrain(vehicleA, vehicleB, "trailerfront", "trailer", false) then
+        table.insert(variants, {
+            name = getText("UI_Text_Towing_attach") .. "\n" .. ISVehicleMenu.getVehicleDisplayName(vehicleB) .. "\n" .. getText("UI_Text_Towing_byTowBar"),
+            func = TowBarMod.Hook.attachByTowBarAction,
+            towingVehicle = vehicleB,
+            towedVehicle = vehicleA,
+            textureName = "tow_bar_icon"
+        })
+    elseif canTowByLandtrain(vehicleA, vehicleB, "trailer", "trailerfront", false) then
+        table.insert(variants, {
+            name = getText("UI_Text_Towing_attach") .. "\n" .. ISVehicleMenu.getVehicleDisplayName(vehicleB) .. "\n" .. getText("UI_Text_Towing_byTowBar"),
+            func = TowBarMod.Hook.attachByTowBarAction,
+            towingVehicle = vehicleA,
+            towedVehicle = vehicleB,
+            textureName = "tow_bar_icon"
+        })
+    end
+
+    return variants
+end
+
+local function menuHasTowbarAttachSlice(menu)
+    if menu == nil or menu.slices == nil then return false end
+    local attachAction = TowBarMod.Hook and TowBarMod.Hook.attachByTowBarAction or nil
+    local chooseAction = TowBarMod.UI and TowBarMod.UI.showChooseVehicleMenu or nil
+    if attachAction == nil and chooseAction == nil then return false end
+
+    for _, slice in ipairs(menu.slices) do
+        local command = slice.command and slice.command[1]
+        if command == attachAction or command == chooseAction then
+            return true
+        end
+    end
+    return false
+end
+
+local function menuHasTowbarDetachSlice(menu)
+    if menu == nil or menu.slices == nil then return false end
+    local detachAction = getDetachAction()
+    if detachAction == nil then return false end
+
+    for _, slice in ipairs(menu.slices) do
+        local command = slice.command and slice.command[1]
+        if command == detachAction then
+            return true
+        end
+    end
+    return false
+end
+
+local function getNearbyTargets(mainVehicle)
+    local targets = {}
+    local square = mainVehicle and mainVehicle:getSquare() or nil
+    if square == nil then return targets end
+
+    for y = square:getY() - 6, square:getY() + 6 do
+        for x = square:getX() - 6, square:getX() + 6 do
+            local square2 = getCell():getGridSquare(x, y, square:getZ())
+            if square2 then
+                for i = 1, square2:getMovingObjects():size() do
+                    local obj = square2:getMovingObjects():get(i - 1)
+                    if obj and instanceof(obj, "BaseVehicle") and obj ~= mainVehicle then
+                        local variants = getLandtrainHookTypeVariants(mainVehicle, obj, true)
+                        if #variants > 0 then
+                            table.insert(targets, { vehicle = obj, variants = variants })
+                        end
+                    end
+                end
+            end
+        end
+    end
+
+    return targets
+end
+
+local function addAttachOptionToMenu(playerObj, vehicle)
+    if playerObj == nil or vehicle == nil then return end
+    local inventory = playerObj:getInventory()
+    if inventory == nil or inventory:getItemFromTypeRecurse("TowBar.TowBar") == nil then return end
+
+    local menu = getPlayerRadialMenu(playerObj:getPlayerNum())
+    if menu == nil then return end
+
+    local targets = getNearbyTargets(vehicle)
+    if #targets == 0 then return end
+
+    if #targets == 1 then
+        local hookType = targets[1].variants[1]
+        menu:addSlice(hookType.name, getTexture("media/textures/tow_bar_attach.png"), hookType.func, playerObj, hookType.towingVehicle, hookType.towedVehicle, hookType.towingPoint, hookType.towedPoint)
+        return
+    end
+
+    local vehicleList = {}
+    for _, entry in ipairs(targets) do table.insert(vehicleList, entry.vehicle) end
+    menu:addSlice(getText("UI_Text_Towing_attach") .. "...", getTexture("media/textures/tow_bar_attach.png"), TowBarMod.UI.showChooseVehicleMenu, playerObj, vehicle, vehicleList, true)
+end
+
+local function addDetachOptionToMenu(playerObj, vehicle)
+    if playerObj == nil or vehicle == nil then return end
+    local detachAction = getDetachAction()
+    if detachAction == nil then return end
+
+    local menu = getPlayerRadialMenu(playerObj:getPlayerNum())
+    if menu == nil or menuHasTowbarDetachSlice(menu) then return end
+    if vehicle:getVehicleTowing() == nil and vehicle:getVehicleTowedBy() == nil then return end
+
+    local target = vehicle:getVehicleTowing() or vehicle
+    menu:addSlice(getText("ContextMenu_Vehicle_DetachTrailer", ISVehicleMenu.getVehicleDisplayName(target)), getTexture("media/textures/tow_bar_detach.png"), detachAction, playerObj, target)
+end
+
+LT.getHookTypeVariantsWrapper = function(vehicleA, vehicleB, hasTowBar)
+    return getLandtrainHookTypeVariants(vehicleA, vehicleB, hasTowBar)
+end
+
+LT.performAttachWrapper = function(playerObj, towingVehicle, towedVehicle, attachmentA, attachmentB)
+    local original = TowBarMod.Hook and TowBarMod.Hook._ltOriginalPerformAttach or nil
+    if original == nil or towingVehicle == nil or towedVehicle == nil then return end
+    if towingVehicle == towedVehicle or towingVehicle:getId() == towedVehicle:getId() then return end
+    if wouldCreateTowLoop(towingVehicle, towedVehicle) then return end
+
+    local frontLink = captureFrontLink(towingVehicle)
+    original(playerObj, towingVehicle, towedVehicle, attachmentA, attachmentB)
+
+    restoreFrontLink(playerObj, frontLink)
+    queueRestoreFront(playerObj, frontLink, 12)
+    queueRestoreFront(playerObj, frontLink, 30)
+
+    setTowBarModelVisible(towedVehicle, true)
+    refreshAround(towingVehicle)
+    refreshAround(towedVehicle)
+end
+
+LT.performDetachWrapper = function(playerObj, towingVehicle, towedVehicle)
+    local original = TowBarMod.Hook and TowBarMod.Hook._ltOriginalPerformDetach or nil
+    if original == nil then return end
+
+    local resolvedTowing, resolvedTowed = resolveDetachPair(towingVehicle, towedVehicle)
+    if resolvedTowing == nil or resolvedTowed == nil then return end
+
+    local frontLink = captureFrontLink(resolvedTowing)
+    original(playerObj, resolvedTowing, resolvedTowed)
+
+    restoreFrontLink(playerObj, frontLink)
+    queueRestoreFront(playerObj, frontLink, 12)
+    queueRestoreFront(playerObj, frontLink, 30)
+
+    restoreDefaultsIfLeadLost(resolvedTowing)
+    restoreDefaultsIfLeadLost(resolvedTowed)
+    refreshAround(resolvedTowing)
+    refreshAround(resolvedTowed)
+
+    queueAction(playerObj, 12, function(_, v) restoreDefaultsIfLeadLost(v); refreshAround(v) end, resolvedTowing)
+    queueAction(playerObj, 12, function(_, v) restoreDefaultsIfLeadLost(v); refreshAround(v) end, resolvedTowed)
+    queueAction(playerObj, 30, function(_, v) restoreDefaultsIfLeadLost(v); refreshAround(v) end, resolvedTowing)
+    queueAction(playerObj, 30, function(_, v) restoreDefaultsIfLeadLost(v); refreshAround(v) end, resolvedTowed)
+
+    setTowBarModelVisible(resolvedTowed, false)
+end
+
+LT.showRadialWrapper = function(playerObj)
+    local original = TowBarMod.UI and TowBarMod.UI._ltOriginalShowRadial or nil
+    if original then original(playerObj) end
+
+    if playerObj == nil or playerObj:getVehicle() then return end
+    if ISVehicleMenu == nil or ISVehicleMenu.getVehicleToInteractWith == nil then return end
+
+    local vehicle = ISVehicleMenu.getVehicleToInteractWith(playerObj)
+    if vehicle == nil then return end
+
+    local linked = vehicle:getVehicleTowing() ~= nil or vehicle:getVehicleTowedBy() ~= nil
+    if not linked then return end
+
+    if TowBarMod.UI and TowBarMod.UI.removeDefaultDetachOption then
+        TowBarMod.UI.removeDefaultDetachOption(playerObj)
+    end
+    addDetachOptionToMenu(playerObj, vehicle)
+
+    local menu = getPlayerRadialMenu(playerObj:getPlayerNum())
+    if menu and not menuHasTowbarAttachSlice(menu) then
+        addAttachOptionToMenu(playerObj, vehicle)
+    end
+end
+
+LT.onDetachTrailerWrapper = function(playerObj, vehicle, ...)
+    local original = TowBarMod.UI and TowBarMod.UI._ltOriginalOnDetachTrailer or nil
+    local detachAction = getDetachAction()
+
+    local vehicleToCheck = vehicle
+    if vehicleToCheck == nil and playerObj and ISVehicleMenu and ISVehicleMenu.getVehicleToInteractWith then
+        vehicleToCheck = ISVehicleMenu.getVehicleToInteractWith(playerObj)
+    end
+
+    if playerObj and vehicleToCheck and detachAction then
+        if vehicleToCheck:getVehicleTowing() or vehicleToCheck:getVehicleTowedBy() then
+            detachAction(playerObj, vehicleToCheck)
+            return
+        end
+    end
+
+    if original then
+        return original(playerObj, vehicle, ...)
+    end
+end
+
+local function ensureTrailerAttachments()
+    local sm = getScriptManager()
+    if sm == nil then return end
+    local scripts = sm:getAllVehicleScripts()
+    if scripts == nil then return end
+
+    for i = 0, scripts:size() - 1 do
+        local script = scripts:get(i)
+        local name = script and script:getName() or nil
+        if script and name and string.match(string.lower(name), "trailer") then
+            local wheelCount = script:getWheelCount()
+            local yOffset = -0.5
+            if wheelCount > 0 then
+                yOffset = script:getWheel(0):getOffset():y() + 0.1
+            end
+
+            if script:getAttachmentById("trailer") == nil then
+                local rearAttach = ModelAttachment.new("trailer")
+                rearAttach:getOffset():set(0, yOffset, -script:getPhysicsChassisShape():z() / 2 - 0.1)
+                rearAttach:setZOffset(-1)
+                script:addAttachment(rearAttach)
+            end
+
+            if script:getAttachmentById("trailerfront") == nil then
+                local frontAttach = ModelAttachment.new("trailerfront")
+                frontAttach:getOffset():set(0, yOffset, script:getPhysicsChassisShape():z() / 2 + 0.1)
+                frontAttach:setZOffset(1)
+                script:addAttachment(frontAttach)
+            end
+        end
+    end
+end
+
+local function installPatch()
+    if TowBarMod.Utils == nil or TowBarMod.UI == nil or TowBarMod.Hook == nil then return false end
+    if TowBarMod.Hook.attachByTowBarAction == nil or ISVehicleMenu == nil then return false end
+    if TowBarMod.Hook.performAttachTowBar == nil then return false end
+    if getPerformDetachHook() == nil then return false end
+
+    if TowBarMod.Utils._ltOriginalGetHookTypeVariants == nil then
+        TowBarMod.Utils._ltOriginalGetHookTypeVariants = TowBarMod.Utils.getHookTypeVariants
+    end
+    TowBarMod.Utils.getHookTypeVariants = LT.getHookTypeVariantsWrapper
+
+    if TowBarMod.Hook._ltOriginalPerformAttach == nil then
+        TowBarMod.Hook._ltOriginalPerformAttach = TowBarMod.Hook.performAttachTowBar
+    end
+    if TowBarMod.Hook._ltOriginalPerformDetach == nil then
+        TowBarMod.Hook._ltOriginalPerformDetach = getPerformDetachHook()
+    end
+    if TowBarMod.Hook._ltOriginalPerformAttach == nil or TowBarMod.Hook._ltOriginalPerformDetach == nil then
+        return false
+    end
+
+    TowBarMod.Hook.performAttachTowBar = LT.performAttachWrapper
+    TowBarMod.Hook.performDetachTowBar = LT.performDetachWrapper
+    TowBarMod.Hook.performDeattachTowBar = LT.performDetachWrapper
+
+    if TowBarMod.UI._ltOriginalShowRadial == nil then
+        TowBarMod.UI._ltOriginalShowRadial = ISVehicleMenu.showRadialMenu
+    end
+    ISVehicleMenu.showRadialMenu = LT.showRadialWrapper
+
+    if TowBarMod.UI._ltOriginalOnDetachTrailer == nil then
+        TowBarMod.UI._ltOriginalOnDetachTrailer = ISVehicleMenu.onDetachTrailer
+    end
+    ISVehicleMenu.onDetachTrailer = LT.onDetachTrailerWrapper
+
+    TowBarMod.Utils._landtrainUnlimitedChainsInstalled = true
+    return true
+end
+
+local watchTicks = 0
+local readyLogged = false
+
+local function watchdogTick()
+    if watchTicks <= 0 then
+        Events.OnTick.Remove(watchdogTick)
+        return
+    end
+    watchTicks = watchTicks - 1
+
+    if installPatch() then
+        if not readyLogged then
+            log("Towbar chain hooks active")
+            readyLogged = true
+        end
+        Events.OnTick.Remove(watchdogTick)
+    end
+end
+
+local function startWatchdog()
+    readyLogged = false
+    watchTicks = 1800
+    Events.OnTick.Remove(watchdogTick)
+    Events.OnTick.Add(watchdogTick)
+    installPatch()
+end
+
+Events.OnGameBoot.Add(ensureTrailerAttachments)
+Events.OnGameBoot.Add(startWatchdog)
+Events.OnGameStart.Add(startWatchdog)
+
+log("LandtrainTowbarChainsRebuild loaded")
+

42.13/media/lua/server/Landtrain/LandtrainTowAttachmentsServer.lua

@@ -0,0 +1,77 @@
+if isClient() then return end
+
+if not TowBarMod then TowBarMod = {} end
+TowBarMod.Landtrain = TowBarMod.Landtrain or {}
+if TowBarMod.Landtrain._serverTowAttachmentsLoaded then return end
+TowBarMod.Landtrain._serverTowAttachmentsLoaded = true
+
+local function log(msg)
+    print("[Landtrain][Server] " .. tostring(msg))
+end
+
+local function addMissingTowAttachments(script)
+    if not script then return 0 end
+
+    local wheelCount = script:getWheelCount()
+    local yOffset = -0.5
+    if wheelCount > 0 then
+        local wheel = script:getWheel(0)
+        if wheel and wheel:getOffset() then
+            yOffset = wheel:getOffset():y() + 0.1
+        end
+    end
+
+    local chassis = script:getPhysicsChassisShape()
+    if not chassis then return 0 end
+
+    local changed = 0
+
+    if script:getAttachmentById("trailer") == nil then
+        local rearAttach = ModelAttachment.new("trailer")
+        rearAttach:getOffset():set(0, yOffset, -chassis:z() / 2 - 0.1)
+        rearAttach:setZOffset(-1)
+        script:addAttachment(rearAttach)
+        changed = changed + 1
+    end
+
+    if script:getAttachmentById("trailerfront") == nil then
+        local frontAttach = ModelAttachment.new("trailerfront")
+        frontAttach:getOffset():set(0, yOffset, chassis:z() / 2 + 0.1)
+        frontAttach:setZOffset(1)
+        script:addAttachment(frontAttach)
+        changed = changed + 1
+    end
+
+    return changed
+end
+
+local function ensureTowAttachmentsServer()
+    local sm = getScriptManager()
+    if sm == nil then
+        log("ScriptManager unavailable; skipping tow attachment bootstrap")
+        return
+    end
+
+    local scripts = sm:getAllVehicleScripts()
+    if scripts == nil then
+        log("Vehicle script list unavailable; skipping tow attachment bootstrap")
+        return
+    end
+
+    local patchedScripts = 0
+    local addedAttachments = 0
+    for i = 0, scripts:size() - 1 do
+        local script = scripts:get(i)
+        local added = addMissingTowAttachments(script)
+        if added > 0 then
+            patchedScripts = patchedScripts + 1
+            addedAttachments = addedAttachments + added
+        end
+    end
+
+    log("Tow attachment bootstrap complete: scripts=" .. tostring(patchedScripts) .. ", attachments=" .. tostring(addedAttachments))
+end
+
+Events.OnGameBoot.Add(ensureTowAttachmentsServer)
+
+log("LandtrainTowAttachmentsServer loaded")

42.13/media/lua/server/Landtrain/LandtrainTowSyncServer.lua

@@ -0,0 +1,124 @@
+if isClient() then return end
+
+if not TowBarMod then TowBarMod = {} end
+TowBarMod.Landtrain = TowBarMod.Landtrain or {}
+if TowBarMod.Landtrain._towSyncServerLoaded then return end
+TowBarMod.Landtrain._towSyncServerLoaded = true
+
+local SYNC_DELAY_TICKS = 2
+local pending = {}
+
+local function log(msg)
+    print("[Landtrain][TowSyncServer] " .. tostring(msg))
+end
+
+local function queueSync(kind, player, args)
+    if not args then return end
+    table.insert(pending, {
+        kind = kind,
+        ticks = SYNC_DELAY_TICKS,
+        player = player,
+        args = args
+    })
+end
+
+local function vehicleHasAttachment(vehicle, attachmentId)
+    if not vehicle or not attachmentId then return false end
+    local script = vehicle:getScript()
+    return script ~= nil and script:getAttachmentById(attachmentId) ~= nil
+end
+
+local function isLinked(vehicleA, vehicleB)
+    if not vehicleA or not vehicleB then return false end
+    return vehicleA:getVehicleTowing() == vehicleB and vehicleB:getVehicleTowedBy() == vehicleA
+end
+
+local function resolveAttachmentA(args, vehicleA)
+    if args and args.attachmentA then return args.attachmentA end
+    if vehicleA and vehicleA:getTowAttachmentSelf() then return vehicleA:getTowAttachmentSelf() end
+    return "trailer"
+end
+
+local function resolveAttachmentB(args, vehicleB)
+    if args and args.attachmentB then return args.attachmentB end
+    if vehicleB and vehicleB:getTowAttachmentSelf() then return vehicleB:getTowAttachmentSelf() end
+    return "trailerfront"
+end
+
+local function processAttach(item)
+    local args = item.args or {}
+    local vehicleA = args.vehicleA and getVehicleById(args.vehicleA) or nil
+    local vehicleB = args.vehicleB and getVehicleById(args.vehicleB) or nil
+    if not vehicleA or not vehicleB then
+        log("attach sync skipped: missing vehicle A=" .. tostring(args.vehicleA) .. " B=" .. tostring(args.vehicleB))
+        return
+    end
+
+    local attachmentA = resolveAttachmentA(args, vehicleA)
+    local attachmentB = resolveAttachmentB(args, vehicleB)
+
+    local linked = isLinked(vehicleA, vehicleB)
+    if not linked then
+        if not vehicleHasAttachment(vehicleA, attachmentA) or not vehicleHasAttachment(vehicleB, attachmentB) then
+            log("attach sync failed: missing attachment A=" .. tostring(attachmentA) .. " B=" .. tostring(attachmentB))
+            return
+        end
+
+        vehicleA:addPointConstraint(item.player, vehicleB, attachmentA, attachmentB)
+        linked = isLinked(vehicleA, vehicleB)
+        if not linked then
+            log("attach sync failed: server link not established A=" .. tostring(vehicleA:getId()) .. " B=" .. tostring(vehicleB:getId()))
+            return
+        end
+    end
+
+    sendServerCommand("landtrain", "forceAttachSync", {
+        vehicleA = vehicleA:getId(),
+        vehicleB = vehicleB:getId(),
+        attachmentA = attachmentA,
+        attachmentB = attachmentB
+    })
+end
+
+local function processDetach(item)
+    local args = item.args or {}
+    local vehicleAId = args.towingVehicle or args.vehicleA or args.vehicle
+    local vehicleBId = args.vehicleB
+
+    sendServerCommand("landtrain", "forceDetachSync", {
+        vehicleA = vehicleAId,
+        vehicleB = vehicleBId
+    })
+end
+
+local function processPending()
+    if #pending == 0 then return end
+
+    for i = #pending, 1, -1 do
+        local item = pending[i]
+        item.ticks = item.ticks - 1
+        if item.ticks <= 0 then
+            if item.kind == "attach" then
+                processAttach(item)
+            elseif item.kind == "detach" then
+                processDetach(item)
+            end
+            table.remove(pending, i)
+        end
+    end
+end
+
+local function onClientCommand(module, command, player, args)
+    if module == "vehicle" and command == "attachTrailer" then
+        queueSync("attach", player, args)
+    elseif module == "vehicle" and command == "detachTrailer" then
+        queueSync("detach", player, args)
+    elseif module == "towbar" and command == "detachTowBar" then
+        queueSync("detach", player, args)
+    end
+end
+
+Events.OnClientCommand.Add(onClientCommand)
+Events.OnTick.Add(processPending)
+
+log("LandtrainTowSyncServer loaded")

README.md

@@ -4,27 +4,46 @@ Landtrain extends Towbars to support chained towing.
 
 ## Important
 
-Project Zomboid base `BaseVehicle.addPointConstraint()` force-breaks existing constraints.
-To keep `1 -> 2` while attaching `2 -> 3`, Landtrain includes a Java class override:
+Project Zomboid base `BaseVehicle.addPointConstraint()` force-breaks existing constraints and chain state in MP.
+To keep `1 -> 2` while attaching `2 -> 3` (and preserve movement replication), Landtrain includes a Java class override:
 
-- `zombie/vehicles/BaseVehicle.class`
+- client install: `zombie/vehicles/BaseVehicle.class`
+- dedicated install: `java/zombie/vehicles/BaseVehicle.class`
+- helper class (both): `LandtrainConstraintAuthHelper.class` in the same `zombie/vehicles` folder
 
 This is the same override pattern used by mods like Realistic Car Physics (manual `zombie` folder copy).
 
 ## Apply patch to game
 
-1. Run:
+1. Patch your local client install:
 
 ```powershell
 .\tools\patch-game-basevehicle.ps1
 ```
 
-2. Ensure both mods are enabled:
-   - `hrsys_towbars`
-   - `hrsys_landtrain`
+2. Patch the dedicated server install:
+
+```powershell
+.\tools\patch-game-basevehicle.ps1 -GameRoot "D:\SteamLibrary\steamapps\common\Project Zomboid Dedicated Server"
+```
+
+3. Ensure both mods are enabled:
+   - `\hrsys_towbars`
+   - `\hrsys_landtrain`
+
+## MP requirement
+
+For multiplayer, every connecting client and the dedicated server must run the patched class.
+If only one side is patched, towing links can desync with no explicit Lua error.
 
 ## Restore vanilla class
 
 ```powershell
 .\tools\restore-game-basevehicle.ps1
 ```
+
+To restore dedicated server too:
+
+```powershell
+.\tools\restore-game-basevehicle.ps1 -GameRoot "D:\SteamLibrary\steamapps\common\Project Zomboid Dedicated Server"
+```

tools/check-game-basevehicle.ps1

@@ -0,0 +1,104 @@
+param(
+    [string]$GameRoot = "D:\SteamLibrary\steamapps\common\ProjectZomboid"
+)
+
+$ErrorActionPreference = "Stop"
+
+function Get-Sha256([string]$Path) {
+    if (-not (Test-Path $Path)) { return $null }
+    return (Get-FileHash $Path -Algorithm SHA256).Hash.ToLowerInvariant()
+}
+
+function Get-JarEntrySha256([string]$JarPath, [string]$EntryName) {
+    if (-not (Test-Path $JarPath)) { return $null }
+
+    Add-Type -AssemblyName System.IO.Compression.FileSystem
+    $zip = [System.IO.Compression.ZipFile]::OpenRead($JarPath)
+    try {
+        $entry = $zip.GetEntry($EntryName)
+        if ($null -eq $entry) { return $null }
+        $stream = $entry.Open()
+        $memory = New-Object System.IO.MemoryStream
+        try {
+            $stream.CopyTo($memory)
+        } finally {
+            $stream.Close()
+        }
+        $bytes = $memory.ToArray()
+        $sha = [System.Security.Cryptography.SHA256]::Create()
+        return (($sha.ComputeHash($bytes) | ForEach-Object { $_.ToString("x2") }) -join "")
+    } finally {
+        $zip.Dispose()
+    }
+}
+
+$repoRoot = Split-Path -Parent $PSScriptRoot
+$knownPatchedClass = Join-Path $repoRoot "zombie\vehicles\BaseVehicle.class"
+$patchedHash = Get-Sha256 $knownPatchedClass
+$patchedHashText = if ($null -eq $patchedHash) { "missing" } else { $patchedHash }
+$knownHelperClass = Join-Path $repoRoot "zombie\vehicles\LandtrainConstraintAuthHelper.class"
+$helperHash = Get-Sha256 $knownHelperClass
+$helperHashText = if ($null -eq $helperHash) { "missing" } else { $helperHash }
+
+$targets = @(
+    @{
+        Name = "Client override path"
+        Path = Join-Path $GameRoot "zombie\vehicles\BaseVehicle.class"
+    },
+    @{
+        Name = "Dedicated override path"
+        Path = Join-Path $GameRoot "java\zombie\vehicles\BaseVehicle.class"
+    }
+)
+
+$jarCandidates = @(
+    (Join-Path $GameRoot "projectzomboid.jar"),
+    (Join-Path $GameRoot "java\projectzomboid.jar")
+)
+
+Write-Output "GameRoot: $GameRoot"
+Write-Output "Known patched hash (repo): $patchedHashText"
+Write-Output "Known helper hash (repo): $helperHashText"
+Write-Output ""
+
+foreach ($target in $targets) {
+    $path = $target.Path
+    $hash = Get-Sha256 $path
+    if ($null -eq $hash) {
+        Write-Output "$($target.Name): MISSING ($path)"
+        continue
+    }
+
+    $status = if ($patchedHash -and $hash -eq $patchedHash) { "PATCHED" } else { "NOT_MATCHING_PATCHED_HASH" }
+    Write-Output "$($target.Name): $status"
+    Write-Output "  path: $path"
+    Write-Output "  hash: $hash"
+}
+
+Write-Output ""
+foreach ($helperPath in @(
+    (Join-Path $GameRoot "zombie\vehicles\LandtrainConstraintAuthHelper.class"),
+    (Join-Path $GameRoot "java\zombie\vehicles\LandtrainConstraintAuthHelper.class")
+) | Select-Object -Unique) {
+    $hash = Get-Sha256 $helperPath
+    if ($null -eq $hash) {
+        Write-Output "Helper class: MISSING ($helperPath)"
+        continue
+    }
+    $status = if ($helperHash -and $hash -eq $helperHash) { "PATCHED" } else { "NOT_MATCHING_HELPER_HASH" }
+    Write-Output "Helper class: $status"
+    Write-Output "  path: $helperPath"
+    Write-Output "  hash: $hash"
+}
+
+Write-Output ""
+foreach ($jar in $jarCandidates | Select-Object -Unique) {
+    $jarHash = Get-JarEntrySha256 $jar "zombie/vehicles/BaseVehicle.class"
+    if ($null -eq $jarHash) {
+        Write-Output "Jar class: MISSING ($jar)"
+        continue
+    }
+    Write-Output "Jar class hash:"
+    Write-Output "  jar: $jar"
+    Write-Output "  hash: $jarHash"
+}

tools/java/BaseVehicleConstraintPatch.java

@@ -3,27 +3,34 @@ import java.nio.file.Path;
 import java.nio.file.Paths;
 import org.objectweb.asm.ClassReader;
 import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.Opcodes;
 import org.objectweb.asm.tree.AbstractInsnNode;
 import org.objectweb.asm.tree.ClassNode;
-import org.objectweb.asm.tree.InsnNode;
 import org.objectweb.asm.tree.InsnList;
+import org.objectweb.asm.tree.InsnNode;
 import org.objectweb.asm.tree.LdcInsnNode;
 import org.objectweb.asm.tree.MethodInsnNode;
 import org.objectweb.asm.tree.MethodNode;
-import org.objectweb.asm.Opcodes;
 
 /**
- * Patches zombie.vehicles.BaseVehicle so addPointConstraint() no longer force-breaks
- * both vehicles before creating a new constraint.
+ * Patches zombie.vehicles.BaseVehicle for Landtrain chain support:
+ * 1) remove forced breakConstraint() in addPointConstraint()
+ * 2) route constraintChanged() driver lookups through helper that handles chain middle vehicles
  */
 public final class BaseVehicleConstraintPatch {
     private static final String TARGET_NAME = "addPointConstraint";
+    private static final String CONSTRAINT_CHANGED_NAME = "constraintChanged";
     private static final String CLINIT_NAME = "<clinit>";
     private static final String VOID_NOARG_DESC = "()V";
     private static final String PATCH_LOG_LINE = "[Landtrain][BaseVehiclePatch] BaseVehicle override enabled";
     private static final String BREAK_DESC_OBJECT_BOOL = "(ZLjava/lang/Boolean;)V";
     private static final String BREAK_DESC_PRIMITIVE_BOOL = "(ZZ)V";
     private static final String BASE_VEHICLE_OWNER = "zombie/vehicles/BaseVehicle";
+    private static final String GET_DRIVER_DESC = "()Lzombie/characters/IsoGameCharacter;";
+    private static final String HELPER_OWNER = "zombie/vehicles/LandtrainConstraintAuthHelper";
+    private static final String HELPER_METHOD = "resolveConstraintDriver";
+    private static final String HELPER_DESC =
+            "(Lzombie/vehicles/BaseVehicle;)Lzombie/characters/IsoGameCharacter;";
 
     private BaseVehicleConstraintPatch() {
     }
@@ -43,12 +50,16 @@ public final class BaseVehicleConstraintPatch {
 
         int removedCalls = 0;
         int inspectedAddPointMethods = 0;
+        int patchedConstraintDriverCalls = 0;
+
         for (MethodNode method : classNode.methods) {
-            if (!TARGET_NAME.equals(method.name) || !isTargetAddPointConstraint(method.desc)) {
-                continue;
-            }
+            if (TARGET_NAME.equals(method.name) && isTargetAddPointConstraint(method.desc)) {
                 inspectedAddPointMethods++;
                 removedCalls += patchAddPointConstraint(method);
+            } else if (CONSTRAINT_CHANGED_NAME.equals(method.name)
+                    && VOID_NOARG_DESC.equals(method.desc)) {
+                patchedConstraintDriverCalls += patchConstraintChangedDriverCalls(method);
+            }
         }
 
         if (removedCalls < 2) {
@@ -59,6 +70,11 @@ public final class BaseVehicleConstraintPatch {
                             + inspectedAddPointMethods
                             + ")");
         }
+        if (patchedConstraintDriverCalls < 1) {
+            throw new IllegalStateException(
+                    "Expected to patch at least 1 constraintChanged getDriver call, patched "
+                            + patchedConstraintDriverCalls);
+        }
         if (!ensureClassInitLog(classNode)) {
             throw new IllegalStateException("Failed to inject BaseVehicle class-init debug log");
         }
@@ -71,12 +87,12 @@ public final class BaseVehicleConstraintPatch {
         System.out.println(
                 "Patched BaseVehicle.class; removed breakConstraint calls: "
                         + removedCalls
+                        + ", constraint driver hooks: "
+                        + patchedConstraintDriverCalls
                         + ", class-init debug log: enabled");
     }
 
     private static boolean isTargetAddPointConstraint(String methodDesc) {
-        // We only want the 5-arg overload:
-        // (IsoPlayer, BaseVehicle, String, String, boolean|Boolean) -> void
         return "(Lzombie/characters/IsoPlayer;Lzombie/vehicles/BaseVehicle;Ljava/lang/String;Ljava/lang/String;Z)V"
                         .equals(methodDesc)
                 || "(Lzombie/characters/IsoPlayer;Lzombie/vehicles/BaseVehicle;Ljava/lang/String;Ljava/lang/String;Ljava/lang/Boolean;)V"
@@ -97,9 +113,8 @@ public final class BaseVehicleConstraintPatch {
                     node = next;
                     continue;
                 }
-                // Keep stack-map frames valid by preserving stack effect:
+
                 // breakConstraint(...) consumes objectref + 2 args and returns void.
-                // Replace invoke with POP2 + POP (consume 3 category-1 stack slots).
                 InsnList replacement = new InsnList();
                 replacement.add(new InsnNode(Opcodes.POP2));
                 replacement.add(new InsnNode(Opcodes.POP));
@@ -113,6 +128,36 @@ public final class BaseVehicleConstraintPatch {
         return patched;
     }
 
+    private static int patchConstraintChangedDriverCalls(MethodNode method) {
+        int patched = 0;
+        InsnList insns = method.instructions;
+        for (AbstractInsnNode node = insns.getFirst(); node != null; ) {
+            AbstractInsnNode next = node.getNext();
+            if (!(node instanceof MethodInsnNode call)) {
+                node = next;
+                continue;
+            }
+            if (!BASE_VEHICLE_OWNER.equals(call.owner)
+                    || !"getDriver".equals(call.name)
+                    || !GET_DRIVER_DESC.equals(call.desc)) {
+                node = next;
+                continue;
+            }
+
+            MethodInsnNode replacement =
+                    new MethodInsnNode(
+                            Opcodes.INVOKESTATIC,
+                            HELPER_OWNER,
+                            HELPER_METHOD,
+                            HELPER_DESC,
+                            false);
+            insns.set(call, replacement);
+            patched++;
+            node = next;
+        }
+        return patched;
+    }
+
     private static boolean ensureClassInitLog(ClassNode classNode) {
         MethodNode clinit = null;
         for (MethodNode method : classNode.methods) {

tools/java/LandtrainConstraintAuthHelper.java

@@ -0,0 +1,38 @@
+package zombie.vehicles;
+
+import zombie.characters.IsoGameCharacter;
+
+/**
+ * Resolves the effective driver for constraint auth in chained towing.
+ * For middle vehicles in a chain, prefer the front/lead driver's authority.
+ */
+public final class LandtrainConstraintAuthHelper {
+    private LandtrainConstraintAuthHelper() {
+    }
+
+    public static IsoGameCharacter resolveConstraintDriver(BaseVehicle vehicle) {
+        if (vehicle == null) {
+            return null;
+        }
+
+        IsoGameCharacter driver = vehicle.getDriver();
+        if (driver != null) {
+            return driver;
+        }
+
+        BaseVehicle front = vehicle.getVehicleTowedBy();
+        if (front != null) {
+            driver = front.getDriver();
+            if (driver != null) {
+                return driver;
+            }
+        }
+
+        BaseVehicle rear = vehicle.getVehicleTowing();
+        if (rear != null) {
+            return rear.getDriver();
+        }
+
+        return null;
+    }
+}

tools/patch-game-basevehicle.ps1

@@ -14,9 +14,27 @@ New-Item -ItemType Directory -Force -Path $classPatchDir | Out-Null
 New-Item -ItemType Directory -Force -Path $buildDir | Out-Null
 
 $javaExe = Join-Path $GameRoot "jre64\bin\java.exe"
-$gameJar = Join-Path $GameRoot "projectzomboid.jar"
 if (-not (Test-Path $javaExe)) { throw "java.exe not found at $javaExe" }
-if (-not (Test-Path $gameJar)) { throw "projectzomboid.jar not found at $gameJar" }
+
+$clientJar = Join-Path $GameRoot "projectzomboid.jar"
+$dedicatedJar = Join-Path $GameRoot "java\projectzomboid.jar"
+$gameJar = $null
+$targetClasses = @()
+
+if (Test-Path $clientJar) {
+    $gameJar = $clientJar
+    $targetClasses += (Join-Path $GameRoot "zombie\vehicles\BaseVehicle.class")
+}
+if (Test-Path $dedicatedJar) {
+    $gameJar = $dedicatedJar
+    $targetClasses += (Join-Path $GameRoot "java\zombie\vehicles\BaseVehicle.class")
+}
+if ($null -eq $gameJar) {
+    throw "projectzomboid.jar not found at either $clientJar or $dedicatedJar"
+}
+if ($targetClasses.Count -eq 0) {
+    throw "No valid BaseVehicle.class deployment targets found under $GameRoot"
+}
 
 $ecjJar = Join-Path $toolsDir "ecj.jar"
 $asmJar = Join-Path $toolsDir "asm.jar"
@@ -34,12 +52,15 @@ if (-not (Test-Path $asmTreeJar)) {
 
 $patcherSource = Join-Path $PSScriptRoot "java\BaseVehicleConstraintPatch.java"
 if (-not (Test-Path $patcherSource)) { throw "Missing patcher source: $patcherSource" }
+$helperSource = Join-Path $PSScriptRoot "java\LandtrainConstraintAuthHelper.java"
+if (-not (Test-Path $helperSource)) { throw "Missing helper source: $helperSource" }
 
-& $javaExe -jar $ecjJar -17 -cp "$asmJar;$asmTreeJar" -d $buildDir $patcherSource
-if ($LASTEXITCODE -ne 0) { throw "Failed to compile BaseVehicleConstraintPatch.java" }
+& $javaExe -jar $ecjJar -17 -cp "$asmJar;$asmTreeJar;$gameJar" -d $buildDir $patcherSource $helperSource
+if ($LASTEXITCODE -ne 0) { throw "Failed to compile BaseVehicleConstraintPatch.java/LandtrainConstraintAuthHelper.java" }
 
 $inputClass = Join-Path $classPatchDir "BaseVehicle.original.class"
 $patchedClass = Join-Path $classPatchDir "BaseVehicle.patched.class"
+$helperClass = Join-Path $buildDir "zombie\vehicles\LandtrainConstraintAuthHelper.class"
 
 Add-Type -AssemblyName System.IO.Compression.FileSystem
 $zip = [System.IO.Compression.ZipFile]::OpenRead($gameJar)
@@ -61,26 +82,33 @@ try {
 
 & $javaExe -cp "$buildDir;$asmJar;$asmTreeJar" BaseVehicleConstraintPatch $inputClass $patchedClass
 if ($LASTEXITCODE -ne 0) { throw "BaseVehicle class patch failed" }
+if (-not (Test-Path $helperClass)) { throw "Missing compiled helper class: $helperClass" }
 
-$targetDir = Join-Path $GameRoot "zombie\vehicles"
-$targetClass = Join-Path $targetDir "BaseVehicle.class"
-$backupClass = "$targetClass.landtrain.original"
+foreach ($targetClass in $targetClasses | Select-Object -Unique) {
+    $targetDir = Split-Path -Parent $targetClass
+    $backupClass = "$targetClass.landtrain.original"
+    $targetHelperClass = Join-Path $targetDir "LandtrainConstraintAuthHelper.class"
 
-New-Item -ItemType Directory -Force -Path $targetDir | Out-Null
-if (-not (Test-Path $backupClass)) {
+    New-Item -ItemType Directory -Force -Path $targetDir | Out-Null
+    if (-not (Test-Path $backupClass)) {
         if (Test-Path $targetClass) {
             Copy-Item $targetClass $backupClass -Force
         } else {
             Copy-Item $inputClass $backupClass -Force
         }
+    }
+    Copy-Item $patchedClass $targetClass -Force
+    Copy-Item $helperClass $targetHelperClass -Force
+    Write-Output "Patched BaseVehicle.class deployed to $targetClass"
+    Write-Output "Deployed LandtrainConstraintAuthHelper.class to $targetHelperClass"
+    Write-Output "Backup stored at $backupClass"
 }
 
-Copy-Item $patchedClass $targetClass -Force
-Write-Output "Patched BaseVehicle.class deployed to $targetClass"
-Write-Output "Backup stored at $backupClass"
-
 $distDir = Join-Path $repoRoot "zombie\vehicles"
 $distClass = Join-Path $distDir "BaseVehicle.class"
+$distHelperClass = Join-Path $distDir "LandtrainConstraintAuthHelper.class"
 New-Item -ItemType Directory -Force -Path $distDir | Out-Null
 Copy-Item $patchedClass $distClass -Force
+Copy-Item $helperClass $distHelperClass -Force
 Write-Output "Distribution class updated at $distClass"
+Write-Output "Distribution helper class updated at $distHelperClass"

tools/restore-game-basevehicle.ps1

@@ -4,15 +4,37 @@ param(
 
 $ErrorActionPreference = "Stop"
 
-$targetClass = Join-Path $GameRoot "zombie\vehicles\BaseVehicle.class"
-$backupClass = "$targetClass.landtrain.original"
+$targets = @(
+    (Join-Path $GameRoot "zombie\vehicles\BaseVehicle.class"),
+    (Join-Path $GameRoot "java\zombie\vehicles\BaseVehicle.class")
+)
+$helperTargets = @(
+    (Join-Path $GameRoot "zombie\vehicles\LandtrainConstraintAuthHelper.class"),
+    (Join-Path $GameRoot "java\zombie\vehicles\LandtrainConstraintAuthHelper.class")
+)
 
-if (Test-Path $backupClass) {
+$handled = $false
+foreach ($targetClass in $targets | Select-Object -Unique) {
+    $backupClass = "$targetClass.landtrain.original"
+    if (Test-Path $backupClass) {
         Copy-Item $backupClass $targetClass -Force
         Write-Output "Restored BaseVehicle.class from $backupClass"
-} elseif (Test-Path $targetClass) {
+        $handled = $true
+    } elseif (Test-Path $targetClass) {
         Remove-Item $targetClass -Force
         Write-Output "Removed override class at $targetClass (game will use class from projectzomboid.jar)"
-} else {
-    Write-Output "No override or backup found. Nothing to restore."
+        $handled = $true
+    }
+}
+
+foreach ($helperClass in $helperTargets | Select-Object -Unique) {
+    if (Test-Path $helperClass) {
+        Remove-Item $helperClass -Force
+        Write-Output "Removed helper override class at $helperClass"
+        $handled = $true
+    }
+}
+
+if (-not $handled) {
+    Write-Output "No override or backup found in known client/dedicated paths. Nothing to restore."
 }