foo

Every one of the 33 standalone tests rebuilt the same seven-line preamble and
the same four-lambda BuildingSystem construction, while PlacementFixture sat
alongside doing exactly that. Each session of this refactor made those 33 blocks
a line longer, which is what made it worth fixing now.

They were not quite identical: 25 used the configured belt speed and 8 a fast
belt of one tile per tick, marked by comments rather than by anything the code
said. The fixture now takes an optional belt speed and kFastBeltSpeed_tps names
the concept, so the difference is visible at the call site instead of buried in
a static_cast.

The per-test comments that explained a choice — the fast belt, the RNG seed —
are kept; the fixture uses the same seed 0 those tests set by hand.

452 test cases and 3431 assertions before and after, so nothing was dropped in
the conversion.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YHcUerKAZKWNvSKJxYKbnG

src/CMakeLists.txt

@@ -1,3 +1,6 @@
+
+
+
 set(TARGET_BASE_NAME "${PRODUCT_NAME}")
 
 set(TARGET_APP_NAME "${TARGET_BASE_NAME}")

src/balancing/ArenaSimulation.cpp

@@ -46,9 +46,10 @@ ArenaSimulation::ArenaSimulation(const GameConfig& gameConfig,
     , m_finished(false)
     , m_stopRequested(false)
 {
+    m_factoryState = makeFactoryState(m_gameConfig);
+
     m_buildingSystem = std::make_unique<BuildingSystem>(
         m_gameConfig,
-        m_factoryState,
         m_beltSystem,
         [this]() { return allocateBuildingId(); },
         [](int) {},
@@ -163,7 +164,7 @@ void ArenaSimulation::placeStructures()
                                                 hp, hp, false);
         // Tag as an HQ so it is excluded from repair targeting (REQ-SHP-REPAIR).
         m_admin.addComponent<HqProxyComponent>(m_team1HqEntity);
-        m_buildingSystem->registerTileOccupancy(absCells, allocateBuildingId());
+        m_buildingSystem->registerTileOccupancy(m_factoryState, absCells, allocateBuildingId());
     }
 
     // Team 2 HQ — ECS proxy entity, enemy faction (isEnemy=true). No weapon.
@@ -184,7 +185,7 @@ void ArenaSimulation::placeStructures()
                                                 hp, hp, true);
         // Tag as an HQ so it is excluded from repair targeting (REQ-SHP-REPAIR).
         m_admin.addComponent<HqProxyComponent>(m_team2HqEntity);
-        m_buildingSystem->registerTileOccupancy(absCells, allocateBuildingId());
+        m_buildingSystem->registerTileOccupancy(m_factoryState, absCells, allocateBuildingId());
     }
 
     auto placeArenaStation = [&](const ArenaStationEntry& entry, bool isEnemy)
@@ -238,7 +239,7 @@ void ArenaSimulation::placeStructures()
             m_admin.addComponent<ModuleOwnerComponent>(wChild,
                 ModuleOwnerComponent{stationEntity});
         }
-        m_buildingSystem->registerTileOccupancy(absCells, allocateBuildingId());
+        m_buildingSystem->registerTileOccupancy(m_factoryState, absCells, allocateBuildingId());
     };
 
     for (const ArenaStationEntry& entry : m_arenaConfig.teams[0].stations)
@@ -323,9 +324,9 @@ void ArenaSimulation::tick()
     // Ship behavior systems (tick step 7): evaluate, select winner, execute.
     // Module + combat systems emit their tool beams into a shared buffer.
     m_shipSystem->clearMovementIntents();
-    m_aiSystem->tick(m_admin, m_factoryState, *m_debrisSystem);
+    m_aiSystem->tick(m_admin, m_factoryState);
     std::vector<BeamFiredEvent> beamFiredEvents;
-    m_salvagerSystem->tick(m_currentTick, *m_debrisSystem, m_factoryState, beamFiredEvents);
+    m_salvagerSystem->tick(m_currentTick, m_factoryState, beamFiredEvents);
     m_repairSystem->tick(m_currentTick, beamFiredEvents);
 
     // Combat resolution (tick step 8).
@@ -393,7 +394,7 @@ void ArenaSimulation::tickDeaths()
     for (entt::entity deadEntity : deadStations)
     {
         const StationBodyComponent& sb = m_admin.get<StationBodyComponent>(deadEntity);
-        m_buildingSystem->unregisterTileOccupancy(sb.bodyCells);
+        m_buildingSystem->unregisterTileOccupancy(m_factoryState, sb.bodyCells);
         {
             std::vector<entt::entity> stationChildren;
             m_admin.forEach<ModuleOwnerComponent>(

src/balancing/ArenaView.cpp

@@ -340,7 +340,7 @@ void ArenaView::drawBuildings(QPainter& painter)
 void ArenaView::drawDebris(QPainter& painter)
 {
     const float r = getTilePx() * 0.2f;
-    for (const DebrisInfo& debris : m_sim->getDebrisSystem().getAllDebrisInfo())
+    for (const DebrisInfo& debris : getAllDebrisInfo(m_sim->getAdmin()))
     {
         const QPointF center = worldToWidget(debris.position);
         painter.setBrush(QColor(128, 110, 90));

src/lib/ecs/system/AiSystem.cpp

@@ -43,8 +43,7 @@ AiSystem::AiSystem(const GameConfig& config)
 {
 }
 
-void AiSystem::tick(EntityAdmin& admin, const FactoryState& state,
+void AiSystem::tick(EntityAdmin& admin, const FactoryState& state)
-                    const DebrisSystem& debris)
 {
     TRACE();
 
@@ -55,7 +54,7 @@ void AiSystem::tick(EntityAdmin& admin, const FactoryState& state,
     m_retreatEvaluator.evaluate(admin);
     m_attackEvaluator.evaluate(admin);
     m_repairEvaluator.evaluate(admin);
-    m_salvageScrapEvaluator.evaluate(admin, debris);
+    m_salvageScrapEvaluator.evaluate(admin);
     m_deliverScrapEvaluator.evaluate(admin, state);
 
     // Phase 2: pick the highest-scoring behavior per ship.

src/lib/ecs/system/AiSystem.h

@@ -20,7 +20,6 @@
 #include "StandbyExecutor.h"
 
 class EntityAdmin;
-class DebrisSystem;
 struct GameConfig;
 
 // Orchestrates ship-behavior decision-making in three batched phases:
@@ -35,7 +34,7 @@ class AiSystem
 public:
     explicit AiSystem(const GameConfig& config);
 
-    void tick(EntityAdmin& admin, const FactoryState& state, const DebrisSystem& debris);
+    void tick(EntityAdmin& admin, const FactoryState& state);
 
 private:
     void selectWinningBehaviors(EntityAdmin& admin);

src/lib/ecs/system/DebrisSystem.cpp

@@ -46,13 +46,13 @@ std::optional<int> DebrisSystem::consume(entt::entity entity)
     return amount;
 }
 
-bool DebrisSystem::collectOne(entt::entity entity)
+bool collectOne(EntityAdmin& admin, entt::entity entity)
 {
-    if (!m_admin.isValid(entity) || !m_admin.hasAll<DebrisComponent>(entity))
+    if (!admin.isValid(entity) || !admin.hasAll<DebrisComponent>(entity))
     {
         return false;
     }
-    DebrisComponent& data = m_admin.get<DebrisComponent>(entity);
+    DebrisComponent& data = admin.get<DebrisComponent>(entity);
     if (data.amount <= 0)
     {
         return false;
@@ -60,18 +60,18 @@ bool DebrisSystem::collectOne(entt::entity entity)
     --data.amount;
     if (data.amount <= 0)
     {
-        m_admin.destroy(entity);
+        admin.destroy(entity);
     }
     return true;
 }
 
-std::vector<DebrisInfo> DebrisSystem::getAllDebrisInfo() const
+std::vector<DebrisInfo> getAllDebrisInfo(const EntityAdmin& admin)
 {
     std::vector<DebrisInfo> result;
-    m_admin.forEach<DebrisComponent>(
+    admin.forEach<DebrisComponent>(
-        [&result, this](entt::entity e, const DebrisComponent& sd)
+        [&result, &admin](entt::entity e, const DebrisComponent& sd)
         {
-            result.push_back(DebrisInfo{e, m_admin.get<PositionComponent>(e).value, sd.amount});
+            result.push_back(DebrisInfo{e, admin.get<PositionComponent>(e).value, sd.amount});
         });
     return result;
 }

src/lib/ecs/system/DebrisSystem.h

@@ -38,9 +38,17 @@ public:
     // false if the entity is invalid or already empty (REQ-SHP-SALVAGE).
     bool collectOne(entt::entity entity);
 
-    // Lightweight snapshot for callers that need to iterate all debris.
-    std::vector<DebrisInfo> getAllDebrisInfo() const;
 
 private:
     EntityAdmin& m_admin;
 };
+
+// Debris state read and changed straight off the registry — no system needed.
+
+// Lightweight snapshot for callers that need to iterate all debris.
+std::vector<DebrisInfo> getAllDebrisInfo(const EntityAdmin& admin);
+
+// Collects a single scrap unit from the debris: decrements its amount by one,
+// destroying the entity once depleted. Returns true if a scrap was collected,
+// false if the entity is invalid or already empty (REQ-SHP-SALVAGE).
+bool collectOne(EntityAdmin& admin, entt::entity entity);

src/lib/ecs/system/SalvagerSystem.cpp

@@ -24,14 +24,14 @@ SalvagerSystem::SalvagerSystem(EntityAdmin& admin)
 {
 }
 
-void SalvagerSystem::tick(Tick currentTick, DebrisSystem& debris, FactoryState& state,
+void SalvagerSystem::tick(Tick currentTick, FactoryState& state,
                           std::vector<BeamFiredEvent>& outBeamFiredEvents)
 {
     TRACE();
     // Apply collections whose mid-beam delay has elapsed (cycles started earlier).
-    applyPendingCollections(currentTick, debris);
+    applyPendingCollections(currentTick);
 
-    const std::vector<DebrisInfo> allDebris = debris.getAllDebrisInfo();
+    const std::vector<DebrisInfo> allDebris = getAllDebrisInfo(m_admin);
 
     // Tick down per-module collection cooldowns.
     m_admin.forEach<SalvagerComponent>(
@@ -108,7 +108,7 @@ void SalvagerSystem::tick(Tick currentTick, DebrisSystem& debris, FactoryState&
         });
 }
 
-void SalvagerSystem::applyPendingCollections(Tick currentTick, DebrisSystem& debris)
+void SalvagerSystem::applyPendingCollections(Tick currentTick)
 {
     std::vector<PendingCollection>::iterator it = m_pendingCollections.begin();
     while (it != m_pendingCollections.end())
@@ -118,7 +118,7 @@ void SalvagerSystem::applyPendingCollections(Tick currentTick, DebrisSystem& deb
             if (m_admin.isValid(it->ship) && m_admin.hasAll<CargoComponent>(it->ship))
             {
                 CargoComponent& cargo = m_admin.get<CargoComponent>(it->ship);
-                if (cargo.current < cargo.maxCapacity && debris.collectOne(it->debris))
+                if (cargo.current < cargo.maxCapacity && collectOne(m_admin, it->debris))
                 {
                     ++cargo.current;
                 }

src/lib/ecs/system/SalvagerSystem.h

@@ -10,7 +10,6 @@
 #include "entt/entity/entity.hpp"
 
 class EntityAdmin;
-class DebrisSystem;
 
 // World-mutation system for salvage modules: each module runs a collection cycle
 // on its own cooldown. When a cycle starts it emits a salvage beam toward an
@@ -22,7 +21,7 @@ class SalvagerSystem
 public:
     explicit SalvagerSystem(EntityAdmin& admin);
 
-    void tick(Tick currentTick, DebrisSystem& debris, FactoryState& state,
+    void tick(Tick currentTick, FactoryState& state,
               std::vector<BeamFiredEvent>& outBeamFiredEvents);
 
 private:
@@ -33,7 +32,7 @@ private:
         Tick         appliesAt;
     };
 
-    void applyPendingCollections(Tick currentTick, DebrisSystem& debris);
+    void applyPendingCollections(Tick currentTick);
 
     EntityAdmin&                   m_admin;
     std::vector<PendingCollection> m_pendingCollections;

src/lib/ecs/system/ai/SalvageScrapEvaluator.cpp

@@ -15,11 +15,11 @@
 #include "SensorRangeComponent.h"
 #include "tracing.h"
 
-void SalvageScrapEvaluator::evaluate(EntityAdmin& admin, const DebrisSystem& debris)
+void SalvageScrapEvaluator::evaluate(EntityAdmin& admin)
 {
     TRACE();
     const std::unordered_map<entt::entity, CargoState> cargoByShip = buildCargoByShip(admin);
-    const std::vector<DebrisInfo> allDebris = debris.getAllDebrisInfo();
+    const std::vector<DebrisInfo> allDebris = getAllDebrisInfo(admin);
 
     admin.forEach<SalvageScrapBehavior, PositionComponent, SensorRangeComponent>(
         [&](entt::entity e, SalvageScrapBehavior& salvage, const PositionComponent& pos,

src/lib/ecs/system/ai/SalvageScrapEvaluator.h

@@ -1,7 +1,6 @@
 #pragma once
 
 class EntityAdmin;
-class DebrisSystem;
 
 // When cargo is not full, finds the nearest debris within sensor range and sets
 // it as the target, scoring high. Scores inactive when cargo is full or no debris
@@ -9,5 +8,5 @@ class DebrisSystem;
 class SalvageScrapEvaluator
 {
 public:
-    void evaluate(EntityAdmin& admin, const DebrisSystem& debris);
+    void evaluate(EntityAdmin& admin);
 };

src/lib/sim/BuildingBuffers.cpp

@@ -0,0 +1,173 @@
+#include "BuildingBuffers.h"
+
+#include <algorithm>
+#include <cassert>
+
+#include "BuildingType.h"
+#include "ItemType.h"
+#include "ModulesConfig.h"
+#include "ShipsConfig.h"
+
+void initBuffers(Building& b, const RecipeDef& recipe)
+{
+    b.inputBuffer.counts.clear();
+    b.inputBuffer.caps.clear();
+    for (const RecipeIngredient& ing : recipe.inputs)
+    {
+        const ItemType type{ing.item};
+        b.inputBuffer.counts[type] = 0;
+        b.inputBuffer.caps[type]   = 2 * ing.amount;
+    }
+
+    b.outputBuffer.items.clear();
+    if (b.type == BuildingType::ReprocessingPlant)
+    {
+        // 1× max-per-roll (REQ-MAT-OUTPUT-BUFFER-REPROCESSING).
+        int maxAmount = 0;
+        for (const RecipeOutput& out : recipe.outputs)
+        {
+            if (out.amount > maxAmount)
+            {
+                maxAmount = out.amount;
+            }
+        }
+        b.outputBuffer.capacity = maxAmount;
+    }
+    else
+    {
+        // 2× per-cycle output.
+        int totalAmount = 0;
+        for (const RecipeOutput& out : recipe.outputs)
+        {
+            totalAmount += out.amount;
+        }
+        b.outputBuffer.capacity = 2 * totalAmount;
+    }
+}
+
+void initAutoBuffers(const GameConfig& config, Building& b)
+{
+    b.inputBuffer.counts.clear();
+    b.inputBuffer.caps.clear();
+
+    // Union the inputs of every recipe of this building type; the cap for each
+    // item is twice the largest per-cycle requirement across those recipes.
+    // Output capacity follows the same rules as initBuffers: the Reprocessing
+    // Plant holds one cycle's max output (REQ-MAT-OUTPUT-BUFFER-REPROCESSING),
+    // other auto buildings hold twice the largest per-cycle output.
+    int outputCapacity = 0;
+    for (const RecipeDef& recipe : config.recipes.recipes)
+    {
+        if (recipe.building != b.type)
+        {
+            continue;
+        }
+
+        for (const RecipeIngredient& ing : recipe.inputs)
+        {
+            const ItemType type{ing.item};
+            b.inputBuffer.counts[type] = 0;
+            b.inputBuffer.caps[type] =
+                std::max(b.inputBuffer.caps[type], 2 * ing.amount);
+        }
+
+        if (b.type == BuildingType::ReprocessingPlant)
+        {
+            int maxAmount = 0;
+            for (const RecipeOutput& out : recipe.outputs)
+            {
+                maxAmount = std::max(maxAmount, out.amount);
+            }
+            outputCapacity = std::max(outputCapacity, maxAmount);
+        }
+        else
+        {
+            int totalAmount = 0;
+            for (const RecipeOutput& out : recipe.outputs)
+            {
+                totalAmount += out.amount;
+            }
+            outputCapacity = std::max(outputCapacity, 2 * totalAmount);
+        }
+    }
+
+    b.outputBuffer.items.clear();
+    b.outputBuffer.capacity = outputCapacity;
+}
+
+void initShipyardBuffers(const GameConfig& config, Building& b)
+{
+    b.inputBuffer.counts.clear();
+    b.inputBuffer.caps.clear();
+    b.outputBuffer.items.clear();
+    b.outputBuffer.capacity = 0;
+    const ShipDef* def = config.ships.findShipDef(b.recipeId);
+    if (!def)
+    {
+        return;
+    }
+    for (const RecipeIngredient& ing : def->schematic.materials)
+    {
+        const ItemType type{ing.item};
+        b.inputBuffer.counts[type] = 0;
+        b.inputBuffer.caps[type]   = 2 * ing.amount;
+    }
+    if (b.shipLayout.has_value())
+    {
+        for (const PlacedModule& pm : b.shipLayout->placedModules)
+        {
+            const ModuleDef* modDef = config.modules.findModuleDef(pm.moduleId);
+            if (!modDef)
+            {
+                continue;
+            }
+            for (const RecipeIngredient& ing : modDef->materials)
+            {
+                const ItemType type{ing.item};
+                b.inputBuffer.counts.try_emplace(type, 0);
+                b.inputBuffer.caps[type] += 2 * ing.amount;
+            }
+        }
+    }
+}
+
+void initSalvageBayBuffer(const GameConfig& config, Building& b)
+{
+    // Salvage Bay has no recipe-driven buffer; its output-buffer holding size for
+    // ship drop-off is config-defined (REQ-BLD-SALVAGE-BAY).
+    b.outputBuffer.items.clear();
+    const BuildingDef* def = config.buildings.findBuildingDef(BuildingType::SalvageBay);
+    b.outputBuffer.capacity =
+        (def && def->outputBufferCapacity) ? *def->outputBufferCapacity : 0;
+}
+
+
+void reregisterBeltTile(BeltSystem& belts, const GameConfig& config,
+                        const Building& building,
+                                        const std::vector<ItemType>& splitterFilterA,
+                                        const std::vector<ItemType>& splitterFilterB)
+{
+    switch (building.type)
+    {
+        case BuildingType::Belt:
+            belts.placeBelt(building.anchor, building.rotation);
+            break;
+        case BuildingType::Splitter:
+            assert(building.outputPorts.size() >= 2);
+            belts.placeSplitter(building.anchor,
+                                  building.outputPorts[0].direction,
+                                  building.outputPorts[1].direction);
+            belts.setSplitterFilters(building.anchor, splitterFilterA, splitterFilterB);
+            break;
+        case BuildingType::TunnelEntry:
+            belts.placeTunnelEntry(building.anchor, building.rotation,
+                                     config.world.tunnelMaxDistance_tiles);
+            break;
+        case BuildingType::TunnelExit:
+            belts.placeTunnelExit(building.anchor, building.rotation);
+            break;
+        default:
+            break;
+    }
+}
+

src/lib/sim/BuildingBuffers.h

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <vector>
+
+#include "BeltSystem.h"
+#include "Building.h"
+#include "GameConfig.h"
+#include "ItemType.h"
+#include "RecipesConfig.h"
+
+// Setting a building up when it starts existing or is reconfigured: sizing its
+// input/output buffers from what it will produce, and handing belt-like types back
+// to BeltSystem. Free functions over the config and the building — they read no
+// factory state, so both BuildingSystem and ConstructionSystem can use them.
+
+// Buffers for a building running one known recipe: inputs capped at twice each
+// ingredient's per-cycle amount, output at twice the per-cycle total (one cycle's
+// max for a Reprocessing Plant, REQ-MAT-OUTPUT-BUFFER-REPROCESSING).
+void initBuffers(Building& b, const RecipeDef& recipe);
+
+// Buffers for an auto-recipe building (Smelter, Reprocessing Plant), unioned over
+// every recipe of its type (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING).
+void initAutoBuffers(const GameConfig& config, Building& b);
+
+// Buffers for a shipyard: its schematic's materials plus those of every placed
+// module (REQ-BLD-SHIPYARD).
+void initShipyardBuffers(const GameConfig& config, Building& b);
+
+// The Salvage Bay holds no recipe inputs; its output capacity is config-defined
+// (REQ-BLD-SALVAGE-BAY).
+void initSalvageBayBuffer(const GameConfig& config, Building& b);
+
+// Registers a belt, splitter or tunnel end with BeltSystem. A splitter's filters
+// live in BeltSystem and are lost by removeTile, so they are passed back in
+// (REQ-BLD-SPLITTER). No-op for every other building type.
+void reregisterBeltTile(BeltSystem& belts, const GameConfig& config,
+                        const Building& building,
+                        const std::vector<ItemType>& splitterFilterA,
+                        const std::vector<ItemType>& splitterFilterB);

src/lib/sim/BuildingSystem.cpp

@@ -26,7 +26,6 @@ bool inputLaneEntryFree(const std::vector<BeltItemSlot>& lane)
 }  // namespace
 
 BuildingSystem::BuildingSystem(const GameConfig& config,
-                               FactoryState& state,
                                BeltSystem& belts,
                                std::function<BuildingId()> allocateBuildingId,
                                std::function<void(int)> addBuildingBlocks,
@@ -35,7 +34,6 @@ BuildingSystem::BuildingSystem(const GameConfig& config,
                                std::function<bool(const std::string&)> isItemUnlocked,
                                std::mt19937& rng)
     : m_config(config)
-    , m_state(state)
     , m_belts(belts)
     , m_allocateBuildingId(std::move(allocateBuildingId))
     , m_addBuildingBlocks(std::move(addBuildingBlocks))
@@ -43,146 +41,12 @@ BuildingSystem::BuildingSystem(const GameConfig& config,
     , m_isItemUnlocked(std::move(isItemUnlocked))
     , m_rng(rng)
 {
-    m_state.asteroidWidth_tiles = config.world.regions.asteroidWidth_tiles;
 }
 
 // ---------------------------------------------------------------------------
 // Private helpers
 // ---------------------------------------------------------------------------
 
-void BuildingSystem::initBuffers(Building& b, const RecipeDef& recipe) const
-{
-    b.inputBuffer.counts.clear();
-    b.inputBuffer.caps.clear();
-    for (const RecipeIngredient& ing : recipe.inputs)
-    {
-        const ItemType type{ing.item};
-        b.inputBuffer.counts[type] = 0;
-        b.inputBuffer.caps[type]   = 2 * ing.amount;
-    }
-
-    b.outputBuffer.items.clear();
-    if (b.type == BuildingType::ReprocessingPlant)
-    {
-        // 1× max-per-roll (REQ-MAT-OUTPUT-BUFFER-REPROCESSING).
-        int maxAmount = 0;
-        for (const RecipeOutput& out : recipe.outputs)
-        {
-            if (out.amount > maxAmount)
-            {
-                maxAmount = out.amount;
-            }
-        }
-        b.outputBuffer.capacity = maxAmount;
-    }
-    else
-    {
-        // 2× per-cycle output.
-        int totalAmount = 0;
-        for (const RecipeOutput& out : recipe.outputs)
-        {
-            totalAmount += out.amount;
-        }
-        b.outputBuffer.capacity = 2 * totalAmount;
-    }
-}
-
-void BuildingSystem::initAutoBuffers(Building& b) const
-{
-    b.inputBuffer.counts.clear();
-    b.inputBuffer.caps.clear();
-
-    // Union the inputs of every recipe of this building type; the cap for each
-    // item is twice the largest per-cycle requirement across those recipes.
-    // Output capacity follows the same rules as initBuffers: the Reprocessing
-    // Plant holds one cycle's max output (REQ-MAT-OUTPUT-BUFFER-REPROCESSING),
-    // other auto buildings hold twice the largest per-cycle output.
-    int outputCapacity = 0;
-    for (const RecipeDef& recipe : m_config.recipes.recipes)
-    {
-        if (recipe.building != b.type)
-        {
-            continue;
-        }
-
-        for (const RecipeIngredient& ing : recipe.inputs)
-        {
-            const ItemType type{ing.item};
-            b.inputBuffer.counts[type] = 0;
-            b.inputBuffer.caps[type] =
-                std::max(b.inputBuffer.caps[type], 2 * ing.amount);
-        }
-
-        if (b.type == BuildingType::ReprocessingPlant)
-        {
-            int maxAmount = 0;
-            for (const RecipeOutput& out : recipe.outputs)
-            {
-                maxAmount = std::max(maxAmount, out.amount);
-            }
-            outputCapacity = std::max(outputCapacity, maxAmount);
-        }
-        else
-        {
-            int totalAmount = 0;
-            for (const RecipeOutput& out : recipe.outputs)
-            {
-                totalAmount += out.amount;
-            }
-            outputCapacity = std::max(outputCapacity, 2 * totalAmount);
-        }
-    }
-
-    b.outputBuffer.items.clear();
-    b.outputBuffer.capacity = outputCapacity;
-}
-
-void BuildingSystem::initShipyardBuffers(Building& b) const
-{
-    b.inputBuffer.counts.clear();
-    b.inputBuffer.caps.clear();
-    b.outputBuffer.items.clear();
-    b.outputBuffer.capacity = 0;
-    const ShipDef* def = m_config.ships.findShipDef(b.recipeId);
-    if (!def)
-    {
-        return;
-    }
-    for (const RecipeIngredient& ing : def->schematic.materials)
-    {
-        const ItemType type{ing.item};
-        b.inputBuffer.counts[type] = 0;
-        b.inputBuffer.caps[type]   = 2 * ing.amount;
-    }
-    if (b.shipLayout.has_value())
-    {
-        for (const PlacedModule& pm : b.shipLayout->placedModules)
-        {
-            const ModuleDef* modDef = m_config.modules.findModuleDef(pm.moduleId);
-            if (!modDef)
-            {
-                continue;
-            }
-            for (const RecipeIngredient& ing : modDef->materials)
-            {
-                const ItemType type{ing.item};
-                b.inputBuffer.counts.try_emplace(type, 0);
-                b.inputBuffer.caps[type] += 2 * ing.amount;
-            }
-        }
-    }
-}
-
-void BuildingSystem::initSalvageBayBuffer(Building& b) const
-{
-    // Salvage Bay has no recipe-driven buffer; its output-buffer holding size for
-    // ship drop-off is config-defined (REQ-BLD-SALVAGE-BAY).
-    b.outputBuffer.items.clear();
-    const BuildingDef* def = m_config.buildings.findBuildingDef(BuildingType::SalvageBay);
-    b.outputBuffer.capacity =
-        (def && def->outputBufferCapacity) ? *def->outputBufferCapacity : 0;
-}
-
 
 std::vector<Item> BuildingSystem::rollReprocessingOutput(const RecipeDef& recipe)
 {
@@ -213,7 +77,7 @@ std::vector<Item> BuildingSystem::rollReprocessingOutput(const RecipeDef& recipe
 // Placement
 // ---------------------------------------------------------------------------
 
-std::optional<BuildingId> BuildingSystem::place(BuildingType type, QPoint anchor,
+std::optional<BuildingId> BuildingSystem::place(FactoryState& state, BuildingType type, QPoint anchor,
                                 Rotation rotation, Tick currentTick)
 {
     const BuildingDef* def = m_config.buildings.findBuildingDef(type);
@@ -221,7 +85,7 @@ std::optional<BuildingId> BuildingSystem::place(BuildingType type, QPoint anchor
     const ParsedSurfaceMask mask = parseSurfaceMask(def->surfaceMask, rotation);
 
     // Reject placements that fall outside the world (REQ-BLD-PLACE-VALID).
-    if (!bodyCellsWithinWorldBounds(m_state, m_config, mask.bodyCells, anchor))
+    if (!bodyCellsWithinWorldBounds(state, m_config, mask.bodyCells, anchor))
     {
         return std::nullopt;
     }
@@ -232,7 +96,7 @@ std::optional<BuildingId> BuildingSystem::place(BuildingType type, QPoint anchor
     for (const QPoint& cell : mask.bodyCells)
     {
         const QPoint absCell = anchor + cell;
-        m_state.grid.occupy(absCell, id);
+        state.grid.occupy(absCell, id);
     }
 
     // Build construction site.
@@ -247,13 +111,13 @@ std::optional<BuildingId> BuildingSystem::place(BuildingType type, QPoint anchor
         site.bodyCells.push_back(anchor + cell);
     }
 
-    if (m_state.constructionQueue.empty())
+    if (state.constructionQueue.empty())
     {
         site.completesAt = currentTick + secondsToTicks(def->constructionTimeSeconds);
     }
     // else: completesAt remains 0 (queued, not yet started).
 
-    m_state.constructionQueue.push_back(std::move(site));
+    state.constructionQueue.push_back(std::move(site));
     return id;
 }
 
@@ -261,19 +125,19 @@ std::optional<BuildingId> BuildingSystem::place(BuildingType type, QPoint anchor
 // Deconstruct
 // ---------------------------------------------------------------------------
 
-int BuildingSystem::deconstruct(BuildingId id, Tick currentTick)
+int BuildingSystem::deconstruct(FactoryState& state, BuildingId id, Tick currentTick)
 {
     // Construction site? Removed instantly with the full refund; never queued
     // for deconstruction (REQ-BLD-DECONSTRUCT).
-    for (std::deque<ConstructionSite>::iterator it = m_state.constructionQueue.begin();
+    for (std::deque<ConstructionSite>::iterator it = state.constructionQueue.begin();
-         it != m_state.constructionQueue.end();
+         it != state.constructionQueue.end();
          ++it)
     {
         if (it->id == id)
         {
             const BuildingDef* def = m_config.buildings.findBuildingDef(it->type);
-            m_state.grid.release(it->bodyCells);
+            state.grid.release(it->bodyCells);
-            m_state.constructionQueue.erase(it);
+            state.constructionQueue.erase(it);
             if (def)
             {
                 return def->cost;
@@ -285,7 +149,7 @@ int BuildingSystem::deconstruct(BuildingId id, Tick currentTick)
     // Operational building? Append it to the deconstruction queue rather than
     // removing it now; the partial refund is credited on completion in
     // tickDeconstruction (REQ-BLD-DECON-QUEUE).
-    for (Building& building : m_state.buildings)
+    for (Building& building : state.buildings)
     {
         if (building.id != id) { continue; }
         if (building.queuedForDeconstruction) { return 0; }  // already queued
@@ -313,11 +177,11 @@ int BuildingSystem::deconstruct(BuildingId id, Tick currentTick)
             m_belts.removeTile(building.anchor);
         }
 
-        const bool wasEmpty = m_state.deconstructionQueue.empty();
+        const bool wasEmpty = state.deconstructionQueue.empty();
-        m_state.deconstructionQueue.push_back(std::move(entry));
+        state.deconstructionQueue.push_back(std::move(entry));
         if (wasEmpty)
         {
-            startFrontDeconstruction(currentTick);
+            startFrontDeconstruction(state, m_config, currentTick);
         }
         return 0;
     }
@@ -325,25 +189,14 @@ int BuildingSystem::deconstruct(BuildingId id, Tick currentTick)
     return 0;
 }
 
-void BuildingSystem::startFrontDeconstruction(Tick currentTick)
-{
-    if (m_state.deconstructionQueue.empty()) { return; }
-    DeconstructionEntry& front = m_state.deconstructionQueue.front();
-    if (front.completesAt == 0)
-    {
-        front.completesAt =
-            currentTick + secondsToTicks(m_config.world.deconstructionTimeSeconds);
-    }
-}
-
 // ---------------------------------------------------------------------------
 // Set recipe
 // ---------------------------------------------------------------------------
 
-void BuildingSystem::setRecipe(BuildingId id, const std::string& recipeId)
+void BuildingSystem::setRecipe(FactoryState& state, BuildingId id, const std::string& recipeId)
 {
     // Construction site: store recipe for when building completes.
-    for (ConstructionSite& site : m_state.constructionQueue)
+    for (ConstructionSite& site : state.constructionQueue)
     {
         if (site.id == id)
         {
@@ -366,7 +219,7 @@ void BuildingSystem::setRecipe(BuildingId id, const std::string& recipeId)
     }
 
     // Operational building: clear buffers and re-init.
-    for (Building& building : m_state.buildings)
+    for (Building& building : state.buildings)
     {
         if (building.id == id)
         {
@@ -400,7 +253,7 @@ void BuildingSystem::setRecipe(BuildingId id, const std::string& recipeId)
             {
                 if (building.type == BuildingType::Shipyard)
                 {
-                    initShipyardBuffers(building);
+                    initShipyardBuffers(m_config, building);
                 }
                 else
                 {
@@ -416,9 +269,9 @@ void BuildingSystem::setRecipe(BuildingId id, const std::string& recipeId)
     }
 }
 
-void BuildingSystem::setShipLayout(BuildingId id, const ShipLayoutConfig& layout)
+void BuildingSystem::setShipLayout(FactoryState& state, BuildingId id, const ShipLayoutConfig& layout)
 {
-    for (ConstructionSite& site : m_state.constructionQueue)
+    for (ConstructionSite& site : state.constructionQueue)
     {
         if (site.id == id)
         {
@@ -427,7 +280,7 @@ void BuildingSystem::setShipLayout(BuildingId id, const ShipLayoutConfig& layout
         }
     }
 
-    for (Building& building : m_state.buildings)
+    for (Building& building : state.buildings)
     {
         if (building.id == id)
         {
@@ -444,18 +297,18 @@ void BuildingSystem::setShipLayout(BuildingId id, const ShipLayoutConfig& layout
             for (std::vector<BeltItemSlot>& lane : building.incomingItems) { lane.clear(); }
             if (!building.recipeId.empty() && building.type == BuildingType::Shipyard)
             {
-                initShipyardBuffers(building);
+                initShipyardBuffers(m_config, building);
             }
             return;
         }
     }
 }
 
-void BuildingSystem::setSiteSplitterFilters(BuildingId id,
+void BuildingSystem::setSiteSplitterFilters(FactoryState& state, BuildingId id,
                                             const std::vector<ItemType>& filterA,
                                             const std::vector<ItemType>& filterB)
 {
-    for (ConstructionSite& site : m_state.constructionQueue)
+    for (ConstructionSite& site : state.constructionQueue)
     {
         if (site.id == id && site.type == BuildingType::Splitter)
         {
@@ -470,188 +323,10 @@ void BuildingSystem::setSiteSplitterFilters(BuildingId id,
 // Tick hooks
 // ---------------------------------------------------------------------------
 
-void BuildingSystem::tickConstruction(Tick currentTick)
+void BuildingSystem::cancelDeconstruction(FactoryState& state, BuildingId id)
 {
-	TRACE();
+    for (std::deque<DeconstructionEntry>::iterator it = state.deconstructionQueue.begin();
-    if (m_state.constructionQueue.empty())
+         it != state.deconstructionQueue.end();
-    {
-        return;
-    }
-
-    ConstructionSite& front = m_state.constructionQueue.front();
-
-    // Guard: if somehow the front site was never started, start it now.
-    if (front.completesAt == 0)
-    {
-        const BuildingDef* def = m_config.buildings.findBuildingDef(front.type);
-        if (def)
-        {
-            front.completesAt = currentTick + secondsToTicks(def->constructionTimeSeconds);
-        }
-        return;
-    }
-
-    if (currentTick < front.completesAt)
-    {
-        return;
-    }
-
-    // Promote construction site to an operational Building.
-    const BuildingDef* def = m_config.buildings.findBuildingDef(front.type);
-    const ParsedSurfaceMask mask = parseSurfaceMask(
-        def ? def->surfaceMask : std::vector<std::string>{},
-        front.rotation);
-
-    Building building;
-    building.id        = front.id;
-    building.anchor    = front.anchor;
-    building.footprint = front.footprint;
-    building.rotation  = front.rotation;
-    building.type      = front.type;
-    building.recipeId  = front.recipeId;
-    building.shipLayout = front.shipLayout;
-
-    for (const QPoint& cell : mask.bodyCells)
-    {
-        building.bodyCells.push_back(front.anchor + cell);
-    }
-    for (const Port& port : mask.outputPorts)
-    {
-        Port absPort;
-        absPort.tile      = front.anchor + port.tile;
-        absPort.direction = port.direction;
-        building.outputPorts.push_back(absPort);
-    }
-    building.emergingItems.resize(building.outputPorts.size());
-    building.inputPorts = computeInputPorts(building.bodyCells, building.outputPorts);
-    building.incomingItems.assign(building.inputPorts.size(), {});
-
-    if (building.type == BuildingType::SalvageBay)
-    {
-        initSalvageBayBuffer(building);
-    }
-    else if (isAutoRecipeBuildingType(building.type))
-    {
-        // Smelter/Reprocessing Plant need no recipe selection; buffers are set
-        // up from all recipes of the type (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING).
-        initAutoBuffers(building);
-    }
-    else if (!building.recipeId.empty())
-    {
-        if (building.type == BuildingType::Shipyard)
-        {
-            initShipyardBuffers(building);
-        }
-        else
-        {
-            const RecipeDef* recipe = m_config.recipes.findRecipeDef(building.recipeId, building.type);
-            if (recipe)
-            {
-                initBuffers(building, *recipe);
-            }
-        }
-    }
-
-    // Register with BeltSystem before the move (mask/building stays valid). Any
-    // filters configured while under construction carry over (REQ-BLD-SITE-CONFIG).
-    reregisterBeltTile(building, front.splitterFilterA, front.splitterFilterB);
-
-    m_state.buildings.push_back(std::move(building));
-
-    m_state.constructionQueue.pop_front();
-
-    // Start next queued site if present.
-    if (!m_state.constructionQueue.empty() && m_state.constructionQueue.front().completesAt == 0)
-    {
-        const BuildingDef* nextDef =
-            m_config.buildings.findBuildingDef(m_state.constructionQueue.front().type);
-        if (nextDef)
-        {
-            m_state.constructionQueue.front().completesAt =
-                currentTick + secondsToTicks(nextDef->constructionTimeSeconds);
-        }
-    }
-}
-
-void BuildingSystem::reregisterBeltTile(const Building& building,
-                                        const std::vector<ItemType>& splitterFilterA,
-                                        const std::vector<ItemType>& splitterFilterB)
-{
-    switch (building.type)
-    {
-        case BuildingType::Belt:
-            m_belts.placeBelt(building.anchor, building.rotation);
-            break;
-        case BuildingType::Splitter:
-            assert(building.outputPorts.size() >= 2);
-            m_belts.placeSplitter(building.anchor,
-                                  building.outputPorts[0].direction,
-                                  building.outputPorts[1].direction);
-            m_belts.setSplitterFilters(building.anchor, splitterFilterA, splitterFilterB);
-            break;
-        case BuildingType::TunnelEntry:
-            m_belts.placeTunnelEntry(building.anchor, building.rotation,
-                                     m_config.world.tunnelMaxDistance_tiles);
-            break;
-        case BuildingType::TunnelExit:
-            m_belts.placeTunnelExit(building.anchor, building.rotation);
-            break;
-        default:
-            break;
-    }
-}
-
-void BuildingSystem::tickDeconstruction(Tick currentTick)
-{
-    TRACE();
-    if (m_state.deconstructionQueue.empty())
-    {
-        return;
-    }
-
-    DeconstructionEntry& front = m_state.deconstructionQueue.front();
-
-    // Guard: if the front entry's timer was never started, start it now.
-    if (front.completesAt == 0)
-    {
-        startFrontDeconstruction(currentTick);
-        return;
-    }
-
-    if (currentTick < front.completesAt)
-    {
-        return;
-    }
-
-    // Remove the building from the world and credit its refund (REQ-BLD-DECONSTRUCT).
-    // Belt/tunnel/splitter tiles were already unregistered when the building was
-    // queued (see deconstruct), so only tile occupancy and the record remain.
-    for (std::vector<Building>::iterator it = m_state.buildings.begin();
-         it != m_state.buildings.end();
-         ++it)
-    {
-        if (it->id != front.id) { continue; }
-
-        const BuildingDef* def = m_config.buildings.findBuildingDef(it->type);
-        m_state.grid.release(it->bodyCells);
-        m_state.buildings.erase(it);
-        if (def)
-        {
-            m_addBuildingBlocks(def->cost * m_config.world.refundPercentage / 100);
-        }
-        break;
-    }
-
-    m_state.deconstructionQueue.pop_front();
-
-    // Start the next queued deconstruction, if any.
-    startFrontDeconstruction(currentTick);
-}
-
-void BuildingSystem::cancelDeconstruction(BuildingId id)
-{
-    for (std::deque<DeconstructionEntry>::iterator it = m_state.deconstructionQueue.begin();
-         it != m_state.deconstructionQueue.end();
          ++it)
     {
         if (it->id != id) { continue; }
@@ -659,27 +334,27 @@ void BuildingSystem::cancelDeconstruction(BuildingId id)
         // Resume operation: clear the flag and re-register belt/tunnel/splitter
         // tiles that were unregistered at enqueue (which re-pairs tunnels,
         // REQ-BLD-TUNNEL-PAIR). Deconstruction progress is discarded; no refund.
-        if (Building* building = findBuilding(m_state, id))
+        if (Building* building = findBuilding(state, id))
         {
             building->queuedForDeconstruction = false;
-            reregisterBeltTile(*building, it->splitterFilterA, it->splitterFilterB);
+            reregisterBeltTile(m_belts, m_config, *building, it->splitterFilterA, it->splitterFilterB);
         }
 
-        m_state.deconstructionQueue.erase(it);
+        state.deconstructionQueue.erase(it);
         // If the running front was removed, the new front (completesAt == 0) has
         // its timer started by the next tickDeconstruction guard.
         return;
     }
 }
 
-void BuildingSystem::tickBeltPull()
+void BuildingSystem::tickBeltPull(FactoryState& state)
 {
 	TRACE();
     // Same per-tick step as the belts, so items travel inward at belt speed
     // (REQ-GW-BELT-SPEED, REQ-MAT-INPUT-INTAKE).
     const double progressPerTick = m_belts.getProgressPerTick_tpt();
 
-    for (Building& building : m_state.buildings)
+    for (Building& building : state.buildings)
     {
         // A building queued for deconstruction stops operating (REQ-BLD-DECON-QUEUE).
         if (building.queuedForDeconstruction) { continue; }
@@ -759,17 +434,17 @@ void BuildingSystem::depositToInputBelt(Building& consumer,
     consumer.incomingItems[inputPortIndex].push_back(BeltItemSlot{item, 0.0});
 }
 
-bool BuildingSystem::tryDirectCoupleDeposit(BuildingId producerId,
+bool BuildingSystem::tryDirectCoupleDeposit(FactoryState& state, BuildingId producerId,
                                             const Port& outputPort,
                                             const Item& item)
 {
-    const std::optional<BuildingId> ownerId = m_state.grid.findOwner(outputPort.tile);
+    const std::optional<BuildingId> ownerId = state.grid.findOwner(outputPort.tile);
     if (!ownerId.has_value() || *ownerId == producerId)
     {
         return false;
     }
 
-    Building* consumer = findBuilding(m_state, *ownerId);
+    Building* consumer = findBuilding(state, *ownerId);
     if (!consumer)
     {
         return false;  // an unbuilt construction site, or not an operational building
@@ -794,10 +469,10 @@ bool BuildingSystem::tryDirectCoupleDeposit(BuildingId producerId,
     return false;
 }
 
-void BuildingSystem::tickProduction(Tick currentTick)
+void BuildingSystem::tickProduction(FactoryState& state, Tick currentTick)
 {
 	TRACE();
-    for (Building& building : m_state.buildings)
+    for (Building& building : state.buildings)
     {
         // A building queued for deconstruction stops operating (REQ-BLD-DECON-QUEUE).
         if (building.queuedForDeconstruction) { continue; }
@@ -897,10 +572,10 @@ void BuildingSystem::tickProduction(Tick currentTick)
     }
 }
 
-void BuildingSystem::tickShipyardProduction(Tick currentTick)
+void BuildingSystem::tickShipyardProduction(FactoryState& state, Tick currentTick)
 {
 	TRACE();
-    for (Building& building : m_state.buildings)
+    for (Building& building : state.buildings)
     {
         // A building queued for deconstruction stops operating (REQ-BLD-DECON-QUEUE).
         if (building.queuedForDeconstruction) { continue; }
@@ -993,14 +668,14 @@ void BuildingSystem::tickShipyardProduction(Tick currentTick)
     }
 }
 
-void BuildingSystem::tickOutputBelts()
+void BuildingSystem::tickOutputBelts(FactoryState& state)
 {
 	TRACE();
     // Use BeltSystem's own per-tick step so emerging items travel at exactly the
     // same speed as real belts (REQ-GW-BELT-SPEED, REQ-MAT-OUTPUT-EMERGE).
     const double progressPerTick = m_belts.getProgressPerTick_tpt();
 
-    for (Building& building : m_state.buildings)
+    for (Building& building : state.buildings)
     {
         // A building queued for deconstruction stops operating (REQ-BLD-DECON-QUEUE).
         if (building.queuedForDeconstruction) { continue; }
@@ -1023,7 +698,7 @@ void BuildingSystem::tickOutputBelts()
             {
                 const Item item = lane.front().item;
                 if (m_belts.tryPutItem(port.tile, item, port.direction)
-                    || tryDirectCoupleDeposit(building.id, port, item))
+                    || tryDirectCoupleDeposit(state, building.id, port, item))
                 {
                     lane.erase(lane.begin());
                 }
@@ -1043,10 +718,10 @@ void BuildingSystem::tickOutputBelts()
     }
 }
 
-void BuildingSystem::forEachEmergingItem(
+void BuildingSystem::forEachEmergingItem(const FactoryState& state, 
     const std::function<void(const ItemType&, QPointF)>& visit) const
 {
-    for (const Building& building : m_state.buildings)
+    for (const Building& building : state.buildings)
     {
         for (std::size_t p = 0; p < building.outputPorts.size(); ++p)
         {
@@ -1065,10 +740,10 @@ void BuildingSystem::forEachEmergingItem(
     }
 }
 
-void BuildingSystem::forEachIncomingItem(
+void BuildingSystem::forEachIncomingItem(const FactoryState& state, 
     const std::function<void(const ItemType&, QPointF)>& visit) const
 {
-    for (const Building& building : m_state.buildings)
+    for (const Building& building : state.buildings)
     {
         for (std::size_t p = 0; p < building.inputPorts.size(); ++p)
         {
@@ -1096,10 +771,10 @@ void BuildingSystem::forEachIncomingItem(
 
 
 
-void BuildingSystem::rotateInPlace(BuildingId id, Rotation newRotation)
+void BuildingSystem::rotateInPlace(FactoryState& state, BuildingId id, Rotation newRotation)
 {
     // Construction site path — just update rotation; no ports to recompute.
-    for (ConstructionSite& site : m_state.constructionQueue)
+    for (ConstructionSite& site : state.constructionQueue)
     {
         if (site.id == id)
         {
@@ -1109,7 +784,7 @@ void BuildingSystem::rotateInPlace(BuildingId id, Rotation newRotation)
     }
 
     // Operational building path.
-    for (Building& b : m_state.buildings)
+    for (Building& b : state.buildings)
     {
         if (b.id != id) { continue; }
 
@@ -1154,14 +829,14 @@ void BuildingSystem::rotateInPlace(BuildingId id, Rotation newRotation)
             }
 
             m_belts.removeTile(b.anchor);
-            reregisterBeltTile(b, splitterFilterA, splitterFilterB);
+            reregisterBeltTile(m_belts, m_config, b, splitterFilterA, splitterFilterB);
         }
 
         return;
     }
 }
 
-BuildingId BuildingSystem::placeImmediate(BuildingType type,
+BuildingId BuildingSystem::placeImmediate(FactoryState& state, BuildingType type,
                                          const std::vector<std::string>& surfaceMask,
                                          QPoint anchor, Rotation rotation)
 {
@@ -1179,7 +854,7 @@ BuildingId BuildingSystem::placeImmediate(BuildingType type,
     {
         const QPoint absCell = anchor + cell;
         building.bodyCells.push_back(absCell);
-        m_state.grid.occupy(absCell, id);
+        state.grid.occupy(absCell, id);
     }
     for (const Port& port : mask.outputPorts)
     {
@@ -1194,17 +869,17 @@ BuildingId BuildingSystem::placeImmediate(BuildingType type,
 
     if (type == BuildingType::SalvageBay)
     {
-        initSalvageBayBuffer(building);
+        initSalvageBayBuffer(m_config, building);
     }
 
-    m_state.buildings.push_back(std::move(building));
+    state.buildings.push_back(std::move(building));
     return id;
 }
 
-bool BuildingSystem::removeBuilding(BuildingId id)
+bool BuildingSystem::removeBuilding(FactoryState& state, BuildingId id)
 {
-    for (std::vector<Building>::iterator it = m_state.buildings.begin();
+    for (std::vector<Building>::iterator it = state.buildings.begin();
-         it != m_state.buildings.end();
+         it != state.buildings.end();
          ++it)
     {
         if (it->id == id)
@@ -1214,31 +889,31 @@ bool BuildingSystem::removeBuilding(BuildingId id)
             {
                 m_belts.removeTile(it->anchor);
             }
-            m_state.grid.release(it->bodyCells);
+            state.grid.release(it->bodyCells);
-            m_state.buildings.erase(it);
+            state.buildings.erase(it);
             return true;
         }
     }
     return false;
 }
 
-void BuildingSystem::forEachBuilding(std::function<void(Building&)> fn)
+void BuildingSystem::forEachBuilding(FactoryState& state, std::function<void(Building&)> fn)
 {
-    for (Building& b : m_state.buildings)
+    for (Building& b : state.buildings)
     {
         fn(b);
     }
 }
 
-void BuildingSystem::registerTileOccupancy(const std::vector<QPoint>& cells,
+void BuildingSystem::registerTileOccupancy(FactoryState& state, const std::vector<QPoint>& cells,
                                             BuildingId ownerPlaceholder)
 {
-    m_state.grid.occupy(cells, ownerPlaceholder);
+    state.grid.occupy(cells, ownerPlaceholder);
 }
 
-void BuildingSystem::unregisterTileOccupancy(const std::vector<QPoint>& cells)
+void BuildingSystem::unregisterTileOccupancy(FactoryState& state, const std::vector<QPoint>& cells)
 {
-    m_state.grid.release(cells);
+    state.grid.release(cells);
 }
 
 namespace
@@ -1270,12 +945,12 @@ void appendInputBuffer(Hasher& hasher, const InputBuffer& buffer)
 }
 }  // namespace
 
-void BuildingSystem::appendChecksum(Hasher& hasher) const
+void BuildingSystem::appendChecksum(const FactoryState& state, Hasher& hasher) const
 {
-    // m_state.buildings keeps a stable, deterministic order (append on build, swap-free
+    // state.buildings keeps a stable, deterministic order (append on build, swap-free
     // erase aside — both runs perform identical operations, so order matches).
-    hasher.append(m_state.buildings.size());
+    hasher.append(state.buildings.size());
-    for (const Building& b : m_state.buildings)
+    for (const Building& b : state.buildings)
     {
         hasher.append(b.id);
         hasher.append(b.anchor);
@@ -1318,8 +993,8 @@ void BuildingSystem::appendChecksum(Hasher& hasher) const
         hasher.append(b.queuedForDeconstruction);
     }
 
-    hasher.append(m_state.constructionQueue.size());
+    hasher.append(state.constructionQueue.size());
-    for (const ConstructionSite& s : m_state.constructionQueue)
+    for (const ConstructionSite& s : state.constructionQueue)
     {
         hasher.append(s.id);
         hasher.append(s.anchor);
@@ -1336,8 +1011,8 @@ void BuildingSystem::appendChecksum(Hasher& hasher) const
         for (const ItemType& type : s.splitterFilterB) { hasher.append(type.id); }
     }
 
-    hasher.append(m_state.deconstructionQueue.size());
+    hasher.append(state.deconstructionQueue.size());
-    for (const DeconstructionEntry& e : m_state.deconstructionQueue)
+    for (const DeconstructionEntry& e : state.deconstructionQueue)
     {
         hasher.append(e.id);
         hasher.append(e.completesAt);
@@ -1347,5 +1022,5 @@ void BuildingSystem::appendChecksum(Hasher& hasher) const
         for (const ItemType& type : e.splitterFilterB) { hasher.append(type.id); }
     }
 
-    m_state.grid.appendChecksum(hasher);
+    state.grid.appendChecksum(hasher);
 }

src/lib/sim/BuildingSystem.h

@@ -16,6 +16,8 @@
 #include "BeltSystem.h"
 #include "Building.h"
 #include "FactoryState.h"
+#include "BuildingBuffers.h"
+#include "DeconstructionSystem.h"
 #include "PlacementRules.h"
 #include "ProductionRules.h"
 #include "BuildingType.h"
@@ -37,7 +39,6 @@ class BuildingSystem
 {
 public:
     BuildingSystem(const GameConfig& config,
-                   FactoryState& state,
                    BeltSystem& belts,
                    std::function<BuildingId()> allocateBuildingId,
                    std::function<void(int)> addBuildingBlocks,
@@ -53,7 +54,7 @@ public:
     // queue.  Terrain type (A vs S) is NOT checked here so that tests can stage
     // arbitrary layouts; the player-facing entry point
     // (Simulation::tryPlaceBuilding) enforces the full rule via isPlacementValid.
-    std::optional<BuildingId> place(BuildingType type, QPoint anchor, Rotation rotation,
+    std::optional<BuildingId> place(FactoryState& state, BuildingType type, QPoint anchor, Rotation rotation,
                    Tick currentTick);
 
     // Returns true if the placement satisfies REQ-BLD-PLACE-VALID terrain and
@@ -65,7 +66,8 @@ public:
     // Sets the current buildable asteroid width in tiles. Grows the left
     // placement bound as the player unlocks asteroid expansions (REQ-EXP-UNLOCK).
     // Defaults to world.regions.asteroid_width_tiles at construction.
-    void setAsteroidWidth_tiles(int widthTiles) { m_state.asteroidWidth_tiles = widthTiles; }
+    void setAsteroidWidth_tiles(FactoryState& state, int widthTiles) const
+    { state.asteroidWidth_tiles = widthTiles; }
 
     // Mark a building or construction site for demolition (REQ-BLD-DECONSTRUCT).
     // A construction site is removed instantly and the full cost is returned.
@@ -73,23 +75,23 @@ public:
     // (REQ-BLD-DECON-QUEUE) and stops operating at once; its (partial) refund is
     // credited later, on completion in tickDeconstruction, so this returns 0 for
     // it. Returns 0 for unknown ids and for a building already queued.
-    int deconstruct(BuildingId id, Tick currentTick);
+    int deconstruct(FactoryState& state, BuildingId id, Tick currentTick);
 
     // Take a building back out of the deconstruction queue before it is removed
     // (REQ-BLD-DECON-QUEUE). Clears its queued flag and resumes operation
     // (re-registering belt/tunnel/splitter tiles); discards deconstruction
     // progress and credits no refund. No-op if the id is not queued.
-    void cancelDeconstruction(BuildingId id);
+    void cancelDeconstruction(FactoryState& state, BuildingId id);
 
     // True if the building is currently in the deconstruction queue.
 
     // Set the recipe (or schematic id for shipyard) on a building or queued
     // construction site.  Clears both buffers on an operational building.
-    void setRecipe(BuildingId id, const std::string& recipeId);
+    void setRecipe(FactoryState& state, BuildingId id, const std::string& recipeId);
 
     // Set the module layout for a shipyard. Cancels in-progress production
     // (materials discarded) and reinitializes input buffers (REQ-BLD-SHIPYARD).
-    void setShipLayout(BuildingId id, const ShipLayoutConfig& layout);
+    void setShipLayout(FactoryState& state, BuildingId id, const ShipLayoutConfig& layout);
 
     // Splitter filter configuration for a queued/under-construction Splitter
     // site (REQ-BLD-SITE-CONFIG). Operational splitters are configured through
@@ -98,23 +100,21 @@ public:
     // output directions (derived from its surface mask) and stored filters, or
     // nullopt if the id is not a Splitter site. The stored filters are applied
     // to BeltSystem when the splitter finishes building (tickConstruction).
-    void setSiteSplitterFilters(BuildingId id,
+    void setSiteSplitterFilters(FactoryState& state, BuildingId id,
                                 const std::vector<ItemType>& filterA,
                                 const std::vector<ItemType>& filterB);
 
     // -- Tick hooks (called from Simulation::tick in the documented order) ---
-    void tickConstruction(Tick currentTick);
     // Advances the deconstruction queue (REQ-BLD-DECON-QUEUE): one building at a
     // time, in parallel with tickConstruction. Removes the front building and
     // credits its refund when its timer elapses.
-    void tickDeconstruction(Tick currentTick);
+    void tickBeltPull(FactoryState& state);
-    void tickBeltPull();
+    void tickProduction(FactoryState& state, Tick currentTick);
-    void tickProduction(Tick currentTick);
+    void tickShipyardProduction(FactoryState& state, Tick currentTick);
-    void tickShipyardProduction(Tick currentTick);
     // Advances each building's virtual output belts, hands finished items off onto
     // the adjacent real belt, and feeds new buffered items into them
     // (REQ-MAT-OUTPUT-EMERGE).
-    void tickOutputBelts();
+    void tickOutputBelts(FactoryState& state);
 
     // -- Queries -------------------------------------------------------------
 
@@ -134,26 +134,19 @@ public:
     // virtual output belt (REQ-MAT-OUTPUT-EMERGE), passing the item type and its
     // world-space centre (in tile units). Least-progressed first (drawn bottom) so
     // callers can paint in visit order (REQ-GW-TILE-SIZE ordering).
-    void forEachEmergingItem(
+    void forEachEmergingItem(const FactoryState& state, 
         const std::function<void(const ItemType&, QPointF)>& visit) const;
 
     // Visits every item currently travelling inward on a building input port's
     // virtual input belt (REQ-MAT-INPUT-INTAKE), passing the item type and its
     // world-space centre (in tile units). Least-progressed first (drawn bottom).
-    void forEachIncomingItem(
+    void forEachIncomingItem(const FactoryState& state, 
         const std::function<void(const ItemType&, QPointF)>& visit) const;
 
-    // Returns the entity id of the building or construction site whose footprint
-    // exactly coincides with the ghost (type, anchor, rot) and is of the same
-    // building type.  Returns nullopt otherwise.
-    std::optional<BuildingId> findRotateInPlaceTarget(BuildingType type,
-                                                     QPoint anchor,
-                                                     Rotation rot) const;
-
     // Rotate an existing building or construction site to newRotation in place.
     // For belt-type operational buildings, re-registers with BeltSystem (items
     // currently on the tile are discarded by BeltSystem::removeTile).
-    void rotateInPlace(BuildingId id, Rotation newRotation);
+    void rotateInPlace(FactoryState& state, BuildingId id, Rotation newRotation);
 
 
     // Input-capable adjacent tiles for a building or construction site
@@ -162,8 +155,8 @@ public:
     // the target. Output-port edges are excluded. Empty for an unknown id.
 
     // Register / unregister tile occupancy for ECS station entities.
-    void registerTileOccupancy(const std::vector<QPoint>& cells, BuildingId ownerPlaceholder);
+    void registerTileOccupancy(FactoryState& state, const std::vector<QPoint>& cells, BuildingId ownerPlaceholder);
-    void unregisterTileOccupancy(const std::vector<QPoint>& cells);
+    void unregisterTileOccupancy(FactoryState& state, const std::vector<QPoint>& cells);
 
     // Place one "scrap" item into a SalvageBay's output buffer.
     // Returns false if bay not found, wrong type, or output buffer is full.
@@ -171,33 +164,29 @@ public:
     // Bypass the construction queue and create a fully-operational Building
     // immediately. Used for pre-placed structures (HQ, defence stations).
     // surfaceMask comes from the relevant config struct.
-    BuildingId placeImmediate(BuildingType type,
+    BuildingId placeImmediate(FactoryState& state, BuildingType type,
                             const std::vector<std::string>& surfaceMask,
                             QPoint anchor, Rotation rotation);
 
     // Remove an operational building by id without refund (used for deaths).
     // Returns true if found and removed.
-    bool removeBuilding(BuildingId id);
+    bool removeBuilding(FactoryState& state, BuildingId id);
 
     // Mutable iteration over all operational buildings.
-    void forEachBuilding(std::function<void(Building&)> fn);
+    void forEachBuilding(FactoryState& state, std::function<void(Building&)> fn);
 
     // -- Determinism ---------------------------------------------------------
     // Folds all building, construction-site, and tile-occupancy state into the
     // hasher in deterministic order (see docs/replay_design.md).
-    void appendChecksum(Hasher& hasher) const;
+    void appendChecksum(const FactoryState& state, Hasher& hasher) const;
 
 private:
     // Starts the front deconstruction-queue entry's timer if not yet started
     // (mirrors how tickConstruction starts a queued construction site).
-    void                 startFrontDeconstruction(Tick currentTick);
 
     // Registers a belt/splitter/tunnel building's tile with the belt subsystem
     // (on construction completion, or when un-queuing a deconstruction). No-op for
     // non-belt-subsystem types. Splitter filters are (re)applied after placement.
-    void                 reregisterBeltTile(const Building& building,
-                                            const std::vector<ItemType>& splitterFilterA,
-                                            const std::vector<ItemType>& splitterFilterB);
 
     // True if the consumer would accept `type` at the given input port right now:
     // it is a required input (or a building block for the HQ), the reservation-aware
@@ -213,7 +202,7 @@ private:
     // Attempts to hand an emerging output item straight into a directly adjacent
     // building whose input edge meets the producer's output port (REQ-MAT-DIRECT-COUPLE).
     // Returns true if the item was accepted onto the consumer's input belt.
-    bool                 tryDirectCoupleDeposit(BuildingId producerId,
+    bool                 tryDirectCoupleDeposit(FactoryState& state, BuildingId producerId,
                                                 const Port& outputPort,
                                                 const Item& item);
 
@@ -228,21 +217,14 @@ private:
     // (ignoring output-buffer space); drives the Starved/Blocked distinction of
     // the status light (REQ-UI-STATUS-LIGHT).
 
-    void                initBuffers(Building& b, const RecipeDef& recipe) const;
     // Buffers for an auto-recipe building (Smelter, Reprocessing Plant): input
     // caps span the union of every recipe of the building's type; no player
     // recipe is selected (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING).
-    void                initAutoBuffers(Building& b) const;
-    void                initShipyardBuffers(Building& b) const;
-    void                initSalvageBayBuffer(Building& b) const;
     // Core input-edge scan shared by operational buildings and construction sites.
     std::vector<Item>   rollReprocessingOutput(const RecipeDef& recipe);
 
     const GameConfig&                              m_config;
 
-    // The factory's world data — buildings, queued work, tile ownership. Owned by
-    // Simulation, not by this system (see FactoryState.h).
-    FactoryState&                                  m_state;
 
     BeltSystem&                                    m_belts;
     std::function<BuildingId()>                      m_allocateBuildingId;

src/lib/sim/CMakeLists.txt

@@ -13,6 +13,9 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/Building.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildingConfig.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildingGrid.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/ConstructionSystem.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/DeconstructionSystem.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/BuildingBuffers.h
     ${CMAKE_CURRENT_SOURCE_DIR}/FactoryState.h
     ${CMAKE_CURRENT_SOURCE_DIR}/FactoryQueries.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ProductionRules.h
@@ -42,6 +45,9 @@ SET(SRCS
     ${CMAKE_CURRENT_SOURCE_DIR}/BeltSystem.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildingConfig.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildingGrid.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/ConstructionSystem.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/DeconstructionSystem.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/BuildingBuffers.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/FactoryQueries.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ProductionRules.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/PlacementRules.cpp

src/lib/sim/ConstructionSystem.cpp

@@ -0,0 +1,112 @@
+#include "ConstructionSystem.h"
+
+#include "BuildingBuffers.h"
+#include "BuildingType.h"
+#include "FactoryQueries.h"
+#include "PortGeometry.h"
+#include "SurfaceMask.h"
+#include "tracing.h"
+
+void ConstructionSystem::tick(FactoryState& state, BeltSystem& belts, Tick currentTick)
+{
+	TRACE();
+    if (state.constructionQueue.empty())
+    {
+        return;
+    }
+
+    ConstructionSite& front = state.constructionQueue.front();
+
+    // Guard: if somehow the front site was never started, start it now.
+    if (front.completesAt == 0)
+    {
+        const BuildingDef* def = m_config.buildings.findBuildingDef(front.type);
+        if (def)
+        {
+            front.completesAt = currentTick + secondsToTicks(def->constructionTimeSeconds);
+        }
+        return;
+    }
+
+    if (currentTick < front.completesAt)
+    {
+        return;
+    }
+
+    // Promote construction site to an operational Building.
+    const BuildingDef* def = m_config.buildings.findBuildingDef(front.type);
+    const ParsedSurfaceMask mask = parseSurfaceMask(
+        def ? def->surfaceMask : std::vector<std::string>{},
+        front.rotation);
+
+    Building building;
+    building.id        = front.id;
+    building.anchor    = front.anchor;
+    building.footprint = front.footprint;
+    building.rotation  = front.rotation;
+    building.type      = front.type;
+    building.recipeId  = front.recipeId;
+    building.shipLayout = front.shipLayout;
+
+    for (const QPoint& cell : mask.bodyCells)
+    {
+        building.bodyCells.push_back(front.anchor + cell);
+    }
+    for (const Port& port : mask.outputPorts)
+    {
+        Port absPort;
+        absPort.tile      = front.anchor + port.tile;
+        absPort.direction = port.direction;
+        building.outputPorts.push_back(absPort);
+    }
+    building.emergingItems.resize(building.outputPorts.size());
+    building.inputPorts = computeInputPorts(building.bodyCells, building.outputPorts);
+    building.incomingItems.assign(building.inputPorts.size(), {});
+
+    if (building.type == BuildingType::SalvageBay)
+    {
+        initSalvageBayBuffer(m_config, building);
+    }
+    else if (isAutoRecipeBuildingType(building.type))
+    {
+        // Smelter/Reprocessing Plant need no recipe selection; buffers are set
+        // up from all recipes of the type (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING).
+        initAutoBuffers(m_config, building);
+    }
+    else if (!building.recipeId.empty())
+    {
+        if (building.type == BuildingType::Shipyard)
+        {
+            initShipyardBuffers(m_config, building);
+        }
+        else
+        {
+            const RecipeDef* recipe = m_config.recipes.findRecipeDef(building.recipeId, building.type);
+            if (recipe)
+            {
+                initBuffers(building, *recipe);
+            }
+        }
+    }
+
+    // Register with BeltSystem before the move (mask/building stays valid). Any
+    // filters configured while under construction carry over (REQ-BLD-SITE-CONFIG).
+    reregisterBeltTile(belts, m_config, building, front.splitterFilterA, front.splitterFilterB);
+
+    state.buildings.push_back(std::move(building));
+
+    state.constructionQueue.pop_front();
+
+    // Start next queued site if present.
+    if (!state.constructionQueue.empty() && state.constructionQueue.front().completesAt == 0)
+    {
+        const BuildingDef* nextDef =
+            m_config.buildings.findBuildingDef(state.constructionQueue.front().type);
+        if (nextDef)
+        {
+            state.constructionQueue.front().completesAt =
+                currentTick + secondsToTicks(nextDef->constructionTimeSeconds);
+        }
+    }
+}
+

src/lib/sim/ConstructionSystem.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include "BeltSystem.h"
+#include "FactoryState.h"
+#include "GameConfig.h"
+#include "Tick.h"
+
+// Advances the construction queue and turns a finished site into an operational
+// building (REQ-BLD-CONSTRUCTION). One site is built at a time, in queue order:
+// the front site's timer runs, and when it elapses the site becomes a Building —
+// its ports and buffers are derived from its definition, its belt tile is handed
+// back to BeltSystem, and the next queued site starts.
+//
+// It completes the building itself rather than handing the finished site back to
+// BuildingSystem: everything materialisation needs is either in FactoryState, the
+// config, or a free function (see BuildingBuffers.h, PortGeometry.h), so there is
+// no intermediate value to pass and no ordering rule between two calls.
+//
+// Holds only the config; the world it works on arrives per tick, like the other
+// systems in lib/ecs/system.
+class ConstructionSystem
+{
+public:
+    explicit ConstructionSystem(const GameConfig& config) : m_config(config) {}
+
+    void tick(FactoryState& state, BeltSystem& belts, Tick currentTick);
+
+private:
+    const GameConfig& m_config;
+};

src/lib/sim/DeconstructionSystem.cpp

@@ -0,0 +1,67 @@
+#include "DeconstructionSystem.h"
+
+#include <vector>
+
+#include "Building.h"
+#include "tracing.h"
+
+void startFrontDeconstruction(FactoryState& state, const GameConfig& config,
+                              Tick currentTick)
+{
+    if (state.deconstructionQueue.empty()) { return; }
+    DeconstructionEntry& front = state.deconstructionQueue.front();
+    if (front.completesAt == 0)
+    {
+        front.completesAt =
+            currentTick + secondsToTicks(config.world.deconstructionTimeSeconds);
+    }
+}
+
+
+void DeconstructionSystem::tick(FactoryState& state, Tick currentTick)
+{
+    TRACE();
+    if (state.deconstructionQueue.empty())
+    {
+        return;
+    }
+
+    DeconstructionEntry& front = state.deconstructionQueue.front();
+
+    // Guard: if the front entry's timer was never started, start it now.
+    if (front.completesAt == 0)
+    {
+        startFrontDeconstruction(state, m_config, currentTick);
+        return;
+    }
+
+    if (currentTick < front.completesAt)
+    {
+        return;
+    }
+
+    // Remove the building from the world and credit its refund (REQ-BLD-DECONSTRUCT).
+    // Belt/tunnel/splitter tiles were already unregistered when the building was
+    // queued (see deconstruct), so only tile occupancy and the record remain.
+    for (std::vector<Building>::iterator it = state.buildings.begin();
+         it != state.buildings.end();
+         ++it)
+    {
+        if (it->id != front.id) { continue; }
+
+        const BuildingDef* def = m_config.buildings.findBuildingDef(it->type);
+        state.grid.release(it->bodyCells);
+        state.buildings.erase(it);
+        if (def)
+        {
+            m_addBuildingBlocks(def->cost * m_config.world.refundPercentage / 100);
+        }
+        break;
+    }
+
+    state.deconstructionQueue.pop_front();
+
+    // Start the next queued deconstruction, if any.
+    startFrontDeconstruction(state, m_config, currentTick);
+}
+

src/lib/sim/DeconstructionSystem.h

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <functional>
+
+#include "FactoryState.h"
+#include "GameConfig.h"
+#include "Tick.h"
+
+// The queue timer for pending demolitions (REQ-BLD-DECON-QUEUE): one building at a
+// time, in parallel with construction. When the front entry's timer elapses the
+// building is removed from the world, its tiles are released, and its partial refund
+// is credited.
+//
+// It needs no BeltSystem: a belt, splitter or tunnel end is unregistered the moment
+// it is queued (see BuildingSystem::deconstruct), not when the timer completes.
+//
+// Holds the config and the refund sink; the world arrives per tick.
+class DeconstructionSystem
+{
+public:
+    DeconstructionSystem(const GameConfig& config,
+                         std::function<void(int)> addBuildingBlocks)
+        : m_config(config), m_addBuildingBlocks(std::move(addBuildingBlocks)) {}
+
+    void tick(FactoryState& state, Tick currentTick);
+
+private:
+    const GameConfig&        m_config;
+    std::function<void(int)> m_addBuildingBlocks;
+};
+
+// Starts the timer on the front entry of the deconstruction queue, if it has one and
+// it has not started yet. Shared: BuildingSystem::deconstruct starts the timer when it
+// queues the first entry, and DeconstructionSystem restarts it after each completion.
+void startFrontDeconstruction(FactoryState& state, const GameConfig& config,
+                              Tick currentTick);

src/lib/sim/FactoryState.h

@@ -4,6 +4,7 @@
 #include <vector>
 
 #include "Building.h"
+#include "GameConfig.h"
 #include "BuildingGrid.h"
 #include "BuildingId.h"
 #include "ItemType.h"
@@ -52,3 +53,14 @@ struct FactoryState
     // Seeded from config by BuildingSystem's constructor.
     int                             asteroidWidth_tiles = 0;
 };
+
+// A fresh factory for a new run: nothing built, and the asteroid bound seeded from
+// config. Every owner of a FactoryState creates it this way — the bound has no
+// sensible default without the config, so a default-constructed state would refuse
+// every placement on the asteroid.
+inline FactoryState makeFactoryState(const GameConfig& config)
+{
+    FactoryState state;
+    state.asteroidWidth_tiles = config.world.regions.asteroidWidth_tiles;
+    return state;
+}

src/lib/sim/Simulation.cpp

@@ -1,6 +1,8 @@
 #include "Simulation.h"
 
 #include "FactoryQueries.h"
+#include "ConstructionSystem.h"
+#include "DeconstructionSystem.h"
 #include "PlacementRules.h"
 
 #include <algorithm>
@@ -50,6 +52,7 @@ Simulation::Simulation(GameConfig config, unsigned int seed)
 {
     m_currentEnemyStationEntities[0] = entt::null;
     m_currentEnemyStationEntities[1] = entt::null;
+    m_factoryState = makeFactoryState(m_config);
 
     initializeSubsystems();
 
@@ -97,7 +100,7 @@ void Simulation::reset(unsigned int seed)
     m_pendingSchematicChoices.clear();
 
     m_admin.clear();
-    m_factoryState = FactoryState{};
+    m_factoryState = makeFactoryState(m_config);
     m_beltSystem = BeltSystem(m_config.world.beltSpeed_tps);
     initializeSubsystems();
 
@@ -109,7 +112,6 @@ void Simulation::initializeSubsystems()
 {
     m_buildingSystem = std::make_unique<BuildingSystem>(
         m_config,
-        m_factoryState,
         m_beltSystem,
         [this]() { return allocateBuildingId(); },
         [this](int amount) { m_buildingBlocksStock += amount; },
@@ -123,6 +125,9 @@ void Simulation::initializeSubsystems()
         },
         [this](const std::string& itemId) -> bool { return isItemUnlocked(itemId); },
         m_rng);
+    m_constructionSystem = std::make_unique<ConstructionSystem>(m_config);
+    m_deconstructionSystem = std::make_unique<DeconstructionSystem>(
+        m_config, [this](int amount) { m_buildingBlocksStock += amount; });
     m_shipSystem     = std::make_unique<ShipSystem>(m_config, m_admin);
     m_aiSystem       = std::make_unique<AiSystem>(m_config);
     m_movementIntentSystem = std::make_unique<MovementIntentSystem>();
@@ -153,15 +158,15 @@ void Simulation::apply(const Command& command)
         const BuildingId id = *placed;
         if (c.recipeId.has_value())
         {
-            m_buildingSystem->setRecipe(id, *c.recipeId);
+            m_buildingSystem->setRecipe(m_factoryState, id, *c.recipeId);
         }
         if (c.shipLayout.has_value())
         {
-            m_buildingSystem->setShipLayout(id, *c.shipLayout);
+            m_buildingSystem->setShipLayout(m_factoryState, id, *c.shipLayout);
         }
         if (c.hasSplitterFilters)
         {
-            m_buildingSystem->setSiteSplitterFilters(id, c.splitterFilterA, c.splitterFilterB);
+            m_buildingSystem->setSiteSplitterFilters(m_factoryState, id, c.splitterFilterA, c.splitterFilterB);
         }
         break;
     }
@@ -174,26 +179,26 @@ void Simulation::apply(const Command& command)
     case CommandKind::RotateInPlace:
     {
         const RotateInPlaceCommand& c = static_cast<const RotateInPlaceCommand&>(command);
-        m_buildingSystem->rotateInPlace(*c.id, c.newRotation);
+        m_buildingSystem->rotateInPlace(m_factoryState, *c.id, c.newRotation);
         break;
     }
     case CommandKind::SetRecipe:
     {
         const SetRecipeCommand& c = static_cast<const SetRecipeCommand&>(command);
-        m_buildingSystem->setRecipe(*c.id, c.recipeId);
+        m_buildingSystem->setRecipe(m_factoryState, *c.id, c.recipeId);
         break;
     }
     case CommandKind::SetShipLayout:
     {
         const SetShipLayoutCommand& c = static_cast<const SetShipLayoutCommand&>(command);
-        m_buildingSystem->setShipLayout(*c.id, c.layout);
+        m_buildingSystem->setShipLayout(m_factoryState, *c.id, c.layout);
         break;
     }
     case CommandKind::SetSiteSplitterFilters:
     {
         const SetSiteSplitterFiltersCommand& c =
             static_cast<const SetSiteSplitterFiltersCommand&>(command);
-        m_buildingSystem->setSiteSplitterFilters(*c.id, c.filterA, c.filterB);
+        m_buildingSystem->setSiteSplitterFilters(m_factoryState, *c.id, c.filterA, c.filterB);
         break;
     }
     case CommandKind::SetSplitterFilters:
@@ -243,12 +248,12 @@ void Simulation::tick()
     m_waveSystem->tickThreatAccumulation();
 
     // Construction + production pipeline
-    m_buildingSystem->tickConstruction(m_currentTick);
+    m_constructionSystem->tick(m_factoryState, m_beltSystem, m_currentTick);
-    m_buildingSystem->tickDeconstruction(m_currentTick); // parallel to construction
+    m_deconstructionSystem->tick(m_factoryState, m_currentTick);        // parallel to construction
-    m_buildingSystem->tickBeltPull();                    // step 3
+    m_buildingSystem->tickBeltPull(m_factoryState);                    // step 3
-    m_buildingSystem->tickProduction(m_currentTick);     // step 4
+    m_buildingSystem->tickProduction(m_factoryState, m_currentTick);     // step 4
-    m_buildingSystem->tickShipyardProduction(m_currentTick); // step 4b
+    m_buildingSystem->tickShipyardProduction(m_factoryState, m_currentTick); // step 4b
-    m_buildingSystem->tickOutputBelts();                 // step 5
+    m_buildingSystem->tickOutputBelts(m_factoryState);                 // step 5
     m_beltSystem.tick();                                 // step 6
 
     // Step 7: ship behavior systems (movement arbitration via intent priority)
@@ -263,10 +268,10 @@ void Simulation::tick()
     m_shipSystem->clearMovementIntents();
     // Score-based behavior selection: evaluate, select winner, execute (sets
     // movement intent + preferred module targets only — no world mutation).
-    m_aiSystem->tick(m_admin, m_factoryState, *m_debrisSystem);
+    m_aiSystem->tick(m_admin, m_factoryState);
     // Module systems perform the world mutation (collection/delivery, healing).
     // Each emits its tool beams and applies its own delayed (mid-beam) effects.
-    m_salvagerSystem->tick(m_currentTick, *m_debrisSystem, m_factoryState, m_beamFiredEvents);
+    m_salvagerSystem->tick(m_currentTick, m_factoryState, m_beamFiredEvents);
     m_repairSystem->tick(m_currentTick, m_beamFiredEvents);
 
     // Step 8: combat resolution
@@ -306,8 +311,7 @@ void Simulation::placeInitialStructures()
         (m_config.world.heightTiles - hqParsed.footprint.height()) / 2;
     const float hqHp =
         static_cast<float>(m_config.stations.hq.hpFormula.evaluate(0.0));
-    m_hqBuildingId = m_buildingSystem->placeImmediate(
+    m_hqBuildingId = m_buildingSystem->placeImmediate(m_factoryState, BuildingType::Hq,
-        BuildingType::Hq,
         m_config.stations.hq.surfaceMask,
         QPoint(hqAnchorX, hqAnchorY),
         Rotation::East);
@@ -356,7 +360,7 @@ void Simulation::placeInitialStructures()
             m_admin.addComponent<ModuleOwnerComponent>(wChild,
                 ModuleOwnerComponent{m_playerStation1Entity});
         }
-        m_buildingSystem->registerTileOccupancy(absCells, allocateBuildingId());
+        m_buildingSystem->registerTileOccupancy(m_factoryState, absCells, allocateBuildingId());
     }
     {
         const QPoint anchor(psAnchorX, ps2Y);
@@ -373,7 +377,7 @@ void Simulation::placeInitialStructures()
             m_admin.addComponent<ModuleOwnerComponent>(wChild,
                 ModuleOwnerComponent{m_playerStation2Entity});
         }
-        m_buildingSystem->registerTileOccupancy(absCells, allocateBuildingId());
+        m_buildingSystem->registerTileOccupancy(m_factoryState, absCells, allocateBuildingId());
     }
 
     // Rally point: center of the player defence stations' X column, world vertical midpoint.
@@ -428,7 +432,7 @@ void Simulation::placeEnemyStationSet(int generation)
             m_admin.addComponent<ModuleOwnerComponent>(wChild,
                 ModuleOwnerComponent{m_currentEnemyStationEntities[0]});
         }
-        m_buildingSystem->registerTileOccupancy(absCells, allocateBuildingId());
+        m_buildingSystem->registerTileOccupancy(m_factoryState, absCells, allocateBuildingId());
     }
     {
         const QPoint anchor(anchorX, y2);
@@ -445,7 +449,7 @@ void Simulation::placeEnemyStationSet(int generation)
             m_admin.addComponent<ModuleOwnerComponent>(wChild,
                 ModuleOwnerComponent{m_currentEnemyStationEntities[1]});
         }
-        m_buildingSystem->registerTileOccupancy(absCells, allocateBuildingId());
+        m_buildingSystem->registerTileOccupancy(m_factoryState, absCells, allocateBuildingId());
     }
 }
 
@@ -519,7 +523,7 @@ void Simulation::tickDeathsAndLoot()
         {
             m_debrisSystem->spawn(pos.value, scrap, despawnAt);
         }
-        m_buildingSystem->unregisterTileOccupancy(sb.bodyCells);
+        m_buildingSystem->unregisterTileOccupancy(m_factoryState, sb.bodyCells);
         {
             std::vector<entt::entity> stationChildren;
             m_admin.forEach<ModuleOwnerComponent>(
@@ -671,7 +675,7 @@ unsigned long long Simulation::computeStateChecksum() const
     m_unlockState.appendChecksum(hasher);
 
     // Subsystems contribute their own state.
-    m_buildingSystem->appendChecksum(hasher);
+    m_buildingSystem->appendChecksum(m_factoryState, hasher);
     m_beltSystem.appendChecksum(hasher);
 
     // ECS component state. View iteration order is a pure function of the
@@ -784,7 +788,7 @@ void Simulation::tryExpandAsteroid()
     }
     m_buildingBlocksStock -= cost;
     ++m_expansionsPurchased;
-    m_buildingSystem->setAsteroidWidth_tiles(getCurrentAsteroidWidth_tiles());
+    m_buildingSystem->setAsteroidWidth_tiles(m_factoryState, getCurrentAsteroidWidth_tiles());
 }
 
 bool Simulation::isGameOver() const
@@ -880,17 +884,17 @@ std::optional<BuildingId> Simulation::tryPlaceBuilding(BuildingType type, QPoint
         return std::nullopt;
     }
     m_buildingBlocksStock -= cost;
-    return m_buildingSystem->place(type, anchor, rotation, m_currentTick);
+    return m_buildingSystem->place(m_factoryState, type, anchor, rotation, m_currentTick);
 }
 
 void Simulation::deconstruct(BuildingId id)
 {
-    m_buildingBlocksStock += m_buildingSystem->deconstruct(id, m_currentTick);
+    m_buildingBlocksStock += m_buildingSystem->deconstruct(m_factoryState, id, m_currentTick);
 }
 
 void Simulation::cancelDeconstruction(BuildingId id)
 {
-    m_buildingSystem->cancelDeconstruction(id);
+    m_buildingSystem->cancelDeconstruction(m_factoryState, id);
 }
 
 BuildingSystem& Simulation::getBuildingsMutable()

src/lib/sim/Simulation.h

@@ -25,6 +25,8 @@
 
 class AiSystem;
 class BuildingSystem;
+class ConstructionSystem;
+class DeconstructionSystem;
 struct Command;
 class Hasher;
 class CombatSystem;
@@ -218,6 +220,8 @@ private:
     FactoryState                      m_factoryState;
     BeltSystem                        m_beltSystem;
     std::unique_ptr<BuildingSystem>   m_buildingSystem;
+    std::unique_ptr<ConstructionSystem> m_constructionSystem;
+    std::unique_ptr<DeconstructionSystem> m_deconstructionSystem;
     std::unique_ptr<ShipSystem>       m_shipSystem;
     std::unique_ptr<AiSystem>         m_aiSystem;
     std::unique_ptr<MovementIntentSystem> m_movementIntentSystem;

src/test/BehaviorSystemTest.cpp

@@ -15,6 +15,7 @@
 #include "BeltSystem.h"
 #include "Building.h"
 #include "BuildingSystem.h"
+#include "ConstructionSystem.h"
 #include "FactoryState.h"
 #include "BuildingType.h"
 #include "ConfigLoader.h"
@@ -56,13 +57,14 @@
 struct Fixture
 {
     GameConfig     cfg;
-    FactoryState   state;
+    FactoryState state = makeFactoryState(cfg);
     BeltSystem     belts;
     BuildingId       nextBuildingId;
     int            stock;
     std::mt19937   rng;
     EntityAdmin    admin;
     BuildingSystem buildings;
+    ConstructionSystem construction;
     ShipSystem     ships;
     AiSystem             ai;
     SalvagerSystem       salvager;
@@ -79,12 +81,13 @@ struct Fixture
         , nextBuildingId(1)
         , stock(0)
         , rng(42)
-        , buildings(cfg, state, belts,
+        , buildings(cfg, belts,
                     [this]() { return nextBuildingId++; },
                     [this](int n) { stock += n; },
                     [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
                     [](const std::string&) -> bool { return true; },
                     rng)
+        , construction(cfg)
         , ships(cfg, admin)
         , ai(cfg)
         , salvager(admin)
@@ -98,14 +101,14 @@ struct Fixture
     void decide()
     {
         ships.clearMovementIntents();
-        ai.tick(admin, state, scraps);
+        ai.tick(admin, state);
     }
 
     // World mutation: collection/delivery and healing.
     void runModules()
     {
         beamEvents.clear();
-        salvager.tick(tick, scraps, state, beamEvents);
+        salvager.tick(tick, state, beamEvents);
         repair.tick(tick, beamEvents);
     }
 
@@ -138,7 +141,7 @@ struct Fixture
     void salvageTick()
     {
         beamEvents.clear();
-        salvager.tick(tick, scraps, state, beamEvents);
+        salvager.tick(tick, state, beamEvents);
         ++tick;
     }
 
@@ -952,12 +955,12 @@ TEST_CASE("BehaviorSystem: full-cargo salvage ship moves toward SalvageBay", "[b
 {
     Fixture f;
 
-    const BuildingId bayId = f.buildings.place(BuildingType::SalvageBay,
+    const BuildingId bayId = f.buildings.place(f.state, BuildingType::SalvageBay,
                                               QPoint(-4, 0), Rotation::East, 0).value();
     Tick t = 0;
     for (int i = 0; i < 500; ++i)
     {
-        f.buildings.tickConstruction(t++);
+        f.construction.tick(f.state, f.belts, t++);
         if (findBuilding(f.state, bayId) != nullptr)
         {
             break;
@@ -987,12 +990,12 @@ TEST_CASE("SalvagerSystem: full-cargo ship at its SalvageBay hands over cargo",
 {
     Fixture f;
 
-    const BuildingId bayId = f.buildings.place(BuildingType::SalvageBay,
+    const BuildingId bayId = f.buildings.place(f.state, BuildingType::SalvageBay,
                                               QPoint(-4, 0), Rotation::East, 0).value();
     Tick t = 0;
     for (int i = 0; i < 500; ++i)
     {
-        f.buildings.tickConstruction(t++);
+        f.construction.tick(f.state, f.belts, t++);
         if (findBuilding(f.state, bayId) != nullptr) { break; }
     }
     const Building* bay = findBuilding(f.state, bayId);

src/test/BlueprintTest.cpp

@@ -666,7 +666,7 @@ TEST_CASE("Blueprint placement: setRecipe on construction site stores recipe", "
     const BuildingId id = SimulationTestAccess::place(sim,BuildingType::Miner, QPoint(-2, 0), Rotation::East).value();
     REQUIRE(id != kInvalidBuildingId);
 
-    SimulationTestAccess::buildings(sim).setRecipe(id, "mine_iron_ore");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), id, "mine_iron_ore");
 
     const ConstructionSite* site = findSite(sim.getFactoryState(), id);
     REQUIRE(site != nullptr);
@@ -680,7 +680,7 @@ TEST_CASE("Blueprint placement: recipe transfers to building after construction
 
     const BuildingId id = SimulationTestAccess::place(sim,BuildingType::Miner, QPoint(-2, 0), Rotation::East).value();
     REQUIRE(id != kInvalidBuildingId);
-    SimulationTestAccess::buildings(sim).setRecipe(id, "mine_copper_ore");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), id, "mine_copper_ore");
 
     // Miner construction_time_seconds = 10 → completesAt = secondsToTicks(10) = 300.
     // Run 301 ticks (0..300) to process the completion tick.
@@ -726,7 +726,7 @@ TEST_CASE("Blueprint creation: a construction site's recipe is captured", "[blue
     const BuildingId id =
         SimulationTestAccess::place(sim, BuildingType::Miner, QPoint(-2, 0), Rotation::East).value();
     REQUIRE(id != kInvalidBuildingId);
-    SimulationTestAccess::buildings(sim).setRecipe(id, "mine_iron_ore");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), id, "mine_iron_ore");
 
     const Blueprint bp = captureBlueprintFromSelection(sim, { id });
 
@@ -743,7 +743,7 @@ TEST_CASE("Blueprint creation: mixed operational building and construction site
     const BuildingId idA =
         SimulationTestAccess::place(sim, BuildingType::Miner, QPoint(-2, 0), Rotation::East).value();
     REQUIRE(idA != kInvalidBuildingId);
-    SimulationTestAccess::buildings(sim).setRecipe(idA, "mine_iron_ore");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), idA, "mine_iron_ore");
     for (int i = 0; i <= static_cast<int>(secondsToTicks(10.0)); ++i) { sim.tick(); }
     REQUIRE(findBuilding(sim.getFactoryState(), idA) != nullptr);
 
@@ -751,7 +751,7 @@ TEST_CASE("Blueprint creation: mixed operational building and construction site
     const BuildingId idB =
         SimulationTestAccess::place(sim, BuildingType::Miner, QPoint(-6, 0), Rotation::East).value();
     REQUIRE(idB != kInvalidBuildingId);
-    SimulationTestAccess::buildings(sim).setRecipe(idB, "mine_copper_ore");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), idB, "mine_copper_ore");
     REQUIRE(findSite(sim.getFactoryState(), idB) != nullptr);
 
     const Blueprint bp = captureBlueprintFromSelection(sim, { idA, idB });
@@ -854,7 +854,7 @@ TEST_CASE("Blueprint placement: setShipLayout on construction site stores layout
     pm.rotation = Rotation::East;
     layout.placedModules.push_back(pm);
 
-    SimulationTestAccess::buildings(sim).setShipLayout(id, layout);
+    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), id, layout);
 
     const ConstructionSite* site = findSite(sim.getFactoryState(), id);
     REQUIRE(site != nullptr);
@@ -878,7 +878,7 @@ TEST_CASE("Blueprint placement: ship layout transfers to building after construc
     pm.rotation = Rotation::North;
     layout.placedModules.push_back(pm);
 
-    SimulationTestAccess::buildings(sim).setShipLayout(id, layout);
+    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), id, layout);
 
     // Shipyard construction_time_seconds = 30 in the test config.
     double constructionTime = 0.0;

src/test/BuildingConfigTest.cpp

@@ -37,8 +37,7 @@ BuildingId placeOperational(Simulation& sim, const GameConfig& cfg,
 {
     const BuildingDef* def = findDef(cfg, type);
     REQUIRE(def != nullptr);
-    return SimulationTestAccess::buildings(sim).placeImmediate(
+    return SimulationTestAccess::buildings(sim).placeImmediate(SimulationTestAccess::state(sim), type, def->surfaceMask, anchor, Rotation::East);
-        type, def->surfaceMask, anchor, Rotation::East);
 }
 
 const ShipDef* findAvailableSchematic(const GameConfig& cfg)
@@ -67,7 +66,7 @@ TEST_CASE("readBuildingConfig returns a miner's selected recipe", "[copyconfig]"
     Simulation sim(loadTestConfig(), 7);
 
     const BuildingId id = placeOperational(sim, cfg, BuildingType::Miner, QPoint(0, 0));
-    SimulationTestAccess::buildings(sim).setRecipe(id, "mine_iron_ore");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), id, "mine_iron_ore");
 
     const std::optional<BuildingConfig> config = readBuildingConfig(sim, id);
     REQUIRE(config.has_value());
@@ -103,8 +102,8 @@ TEST_CASE("readBuildingConfig returns a shipyard's schematic and layout",
     REQUIRE(schematic != nullptr);
 
     const BuildingId id = placeOperational(sim, cfg, BuildingType::Shipyard, QPoint(0, 0));
-    SimulationTestAccess::buildings(sim).setRecipe(id, schematic->id);
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), id, schematic->id);
-    SimulationTestAccess::buildings(sim).setShipLayout(id, ShipLayoutConfig{});
+    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), id, ShipLayoutConfig{});
 
     const std::optional<BuildingConfig> config = readBuildingConfig(sim, id);
     REQUIRE(config.has_value());
@@ -126,7 +125,7 @@ TEST_CASE("readBuildingConfig reads a queued construction site", "[copyconfig]")
     REQUIRE(findBuilding(sim.getFactoryState(), id) == nullptr);
     REQUIRE(findSite(sim.getFactoryState(), id) != nullptr);
 
-    SimulationTestAccess::buildings(sim).setRecipe(id, "mine_iron_ore");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), id, "mine_iron_ore");
 
     const std::optional<BuildingConfig> config = readBuildingConfig(sim, id);
     REQUIRE(config.has_value());

src/test/CombatSystemTest.cpp

@@ -52,7 +52,7 @@ static entt::entity findWeaponChild(EntityAdmin& admin, entt::entity ship)
 struct CombatFixture
 {
     GameConfig cfg;
-    FactoryState state;
+    FactoryState state = makeFactoryState(cfg);
     std::mt19937 rng;
     EntityAdmin admin;
     BuildingId nextBuildingId;
@@ -67,7 +67,7 @@ struct CombatFixture
         , nextBuildingId(1)
         , belts(cfg.world.beltSpeed_tps)
         , ships(cfg, admin)
-        , buildings(cfg, state, belts,
+        , buildings(cfg, belts,
                     [this]() { return nextBuildingId++; },
                     [](int){},
                     [](const std::string&, QVector2D, const std::optional<ShipLayoutConfig>&) {},
@@ -415,7 +415,7 @@ TEST_CASE("CombatSystem: scrap is spawned on ship death", "[combat]")
 
     sim.tick();
 
-    const std::vector<DebrisInfo> scraps = sim.getDebrisSystem().getAllDebrisInfo();
+    const std::vector<DebrisInfo> scraps = getAllDebrisInfo(sim.getAdmin());
     REQUIRE(scraps.size() == 1);
     CHECK(sim.getAdmin().get<DebrisComponent>(scraps[0].entity).amount == 59);
 }

src/test/CommandTest.cpp

@@ -47,7 +47,7 @@ TEST_CASE("apply(PlaceBuildingCommand) with recipe matches place-then-setRecipe"
 
     const BuildingId id =
         SimulationTestAccess::place(viaDirect, BuildingType::Miner, QPoint(-2, 0), Rotation::East).value();
-    SimulationTestAccess::buildings(viaDirect).setRecipe(id, "mine_iron_ore");
+    SimulationTestAccess::buildings(viaDirect).setRecipe(SimulationTestAccess::state(viaDirect), id, "mine_iron_ore");
 
     REQUIRE(viaCommand.computeStateChecksum() == viaDirect.computeStateChecksum());
 }

src/test/DebrisTest.cpp

@@ -116,16 +116,16 @@ TEST_CASE("DebrisSystem: collectOne depletes one scrap and keeps the debris unti
 
     const entt::entity e = ss.spawn(QVector2D(0.0f, 0.0f), 3, 100);
 
-    REQUIRE(ss.collectOne(e));
+    REQUIRE(collectOne(admin, e));
     REQUIRE(admin.isValid(e));
     REQUIRE(admin.get<DebrisComponent>(e).amount == 2);
 
-    REQUIRE(ss.collectOne(e));
+    REQUIRE(collectOne(admin, e));
     REQUIRE(admin.isValid(e));
     REQUIRE(admin.get<DebrisComponent>(e).amount == 1);
 
     // Final unit collected: the debris is removed once depleted.
-    REQUIRE(ss.collectOne(e));
+    REQUIRE(collectOne(admin, e));
     REQUIRE_FALSE(admin.isValid(e));
 }
 
@@ -134,7 +134,7 @@ TEST_CASE("DebrisSystem: collectOne returns false for an invalid entity", "[debr
     EntityAdmin admin;
     DebrisSystem ss(admin);
 
-    REQUIRE_FALSE(ss.collectOne(entt::null));
+    REQUIRE_FALSE(collectOne(admin, entt::null));
 }
 
 // ---------------------------------------------------------------------------
@@ -149,7 +149,7 @@ TEST_CASE("DebrisSystem: getAllDebrisInfo returns all spawned debris", "[debris]
     ss.spawn(QVector2D(1.0f, 2.0f), 3, 100);
     ss.spawn(QVector2D(4.0f, 5.0f), 6, 200);
 
-    const std::vector<DebrisInfo> info = ss.getAllDebrisInfo();
+    const std::vector<DebrisInfo> info = getAllDebrisInfo(admin);
     REQUIRE(info.size() == 2);
 }
 
@@ -161,7 +161,7 @@ TEST_CASE("DebrisSystem: getAllDebrisInfo reports each debris entry.s remaining
     const entt::entity a = ss.spawn(QVector2D(1.0f, 2.0f), 3, 100);
     const entt::entity b = ss.spawn(QVector2D(4.0f, 5.0f), 6, 200);
 
-    const std::vector<DebrisInfo> info = ss.getAllDebrisInfo();
+    const std::vector<DebrisInfo> info = getAllDebrisInfo(admin);
     REQUIRE(info.size() == 2);
     for (const DebrisInfo& i : info)
     {

src/test/ShipModuleTest.cpp

@@ -62,8 +62,7 @@ static const BuildingDef* findShipyardDef(const GameConfig& cfg)
 
 static BuildingId placeShipyard(Simulation& sim, const BuildingDef& yardDef)
 {
-    return SimulationTestAccess::buildings(sim).placeImmediate(
+    return SimulationTestAccess::buildings(sim).placeImmediate(SimulationTestAccess::state(sim), BuildingType::Shipyard,
-        BuildingType::Shipyard,
         yardDef.surfaceMask,
         QPoint(0, 0),
         Rotation::East);
@@ -73,7 +72,7 @@ static void fillMaterials(Simulation& sim, BuildingId yardId,
                           const ShipDef& def,
                           const ShipLayoutConfig& layout)
 {
-    SimulationTestAccess::buildings(sim).forEachBuilding([&](Building& b) {
+    SimulationTestAccess::buildings(sim).forEachBuilding(SimulationTestAccess::state(sim), [&](Building& b) {
         if (b.id != yardId)
         {
             return;
@@ -208,7 +207,7 @@ TEST_CASE("Shipyard: setShipLayout reinitializes buffers with module materials",
     REQUIRE(yardDef != nullptr);
 
     const BuildingId yardId = placeShipyard(sim, *yardDef);
-    SimulationTestAccess::buildings(sim).setRecipe(yardId,"interceptor");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), yardId,"interceptor");
 
     ShipLayoutConfig layout;
     PlacedModule pm;
@@ -217,7 +216,7 @@ TEST_CASE("Shipyard: setShipLayout reinitializes buffers with module materials",
     pm.rotation = Rotation::East;
     layout.placedModules.push_back(pm);
 
-    SimulationTestAccess::buildings(sim).setShipLayout(yardId, layout);
+    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), yardId, layout);
 
     const Building* b = findBuilding(sim.getFactoryState(), yardId);
     REQUIRE(b != nullptr);
@@ -237,7 +236,7 @@ TEST_CASE("Shipyard: setShipLayout cancels in-progress production",
     REQUIRE(yardDef != nullptr);
 
     const BuildingId yardId = placeShipyard(sim, *yardDef);
-    SimulationTestAccess::buildings(sim).setRecipe(yardId,"interceptor");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), yardId,"interceptor");
 
     // Fill materials and tick to start production.
     ShipLayoutConfig emptyLayout;
@@ -256,7 +255,7 @@ TEST_CASE("Shipyard: setShipLayout cancels in-progress production",
     pm.rotation = Rotation::East;
     layout.placedModules.push_back(pm);
 
-    SimulationTestAccess::buildings(sim).setShipLayout(yardId, layout);
+    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), yardId, layout);
 
     const Building* b2 = findBuilding(sim.getFactoryState(), yardId);
     REQUIRE(b2 != nullptr);
@@ -279,7 +278,7 @@ TEST_CASE("Shipyard: builds a bare hull when no layout is configured",
     REQUIRE(yardDef != nullptr);
 
     const BuildingId yardId = placeShipyard(sim, *yardDef);
-    SimulationTestAccess::buildings(sim).setRecipe(yardId, "interceptor");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), yardId, "interceptor");
     // Deliberately no setShipLayout: recipe set, layout left unconfigured.
 
     // Charge only the base-hull materials (an empty layout adds none).
@@ -314,7 +313,7 @@ TEST_CASE("Shipyard: setRecipe clears ship layout", "[modules][shipyard]")
     REQUIRE(yardDef != nullptr);
 
     const BuildingId yardId = placeShipyard(sim, *yardDef);
-    SimulationTestAccess::buildings(sim).setRecipe(yardId,"interceptor");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), yardId,"interceptor");
 
     ShipLayoutConfig layout;
     PlacedModule pm;
@@ -322,13 +321,13 @@ TEST_CASE("Shipyard: setRecipe clears ship layout", "[modules][shipyard]")
     pm.position = QPoint(0, 0);
     pm.rotation = Rotation::East;
     layout.placedModules.push_back(pm);
-    SimulationTestAccess::buildings(sim).setShipLayout(yardId, layout);
+    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), yardId, layout);
 
     const Building* b1 = findBuilding(sim.getFactoryState(), yardId);
     REQUIRE(b1 != nullptr);
     REQUIRE(b1->shipLayout.has_value());
 
-    SimulationTestAccess::buildings(sim).setRecipe(yardId,"destroyer");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), yardId,"destroyer");
 
     const Building* b2 = findBuilding(sim.getFactoryState(), yardId);
     REQUIRE(b2 != nullptr);
@@ -343,7 +342,7 @@ TEST_CASE("Shipyard: setRecipe with unchanged recipe keeps ship layout",
     REQUIRE(yardDef != nullptr);
 
     const BuildingId yardId = placeShipyard(sim, *yardDef);
-    SimulationTestAccess::buildings(sim).setRecipe(yardId,"interceptor");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), yardId,"interceptor");
 
     ShipLayoutConfig layout;
     PlacedModule pm;
@@ -351,14 +350,14 @@ TEST_CASE("Shipyard: setRecipe with unchanged recipe keeps ship layout",
     pm.position = QPoint(0, 0);
     pm.rotation = Rotation::East;
     layout.placedModules.push_back(pm);
-    SimulationTestAccess::buildings(sim).setShipLayout(yardId, layout);
+    SimulationTestAccess::buildings(sim).setShipLayout(SimulationTestAccess::state(sim), yardId, layout);
 
     const Building* b1 = findBuilding(sim.getFactoryState(), yardId);
     REQUIRE(b1 != nullptr);
     REQUIRE(b1->shipLayout.has_value());
 
     // Re-selecting the same recipe must be a no-op and preserve the layout.
-    SimulationTestAccess::buildings(sim).setRecipe(yardId,"interceptor");
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), yardId,"interceptor");
 
     const Building* b2 = findBuilding(sim.getFactoryState(), yardId);
     REQUIRE(b2 != nullptr);

src/test/ShipyardTest.cpp

@@ -58,8 +58,7 @@ static const BuildingDef* findShipyardDef(const GameConfig& cfg)
 
 static BuildingId placeShipyard(Simulation& sim, const BuildingDef& yardDef)
 {
-    return SimulationTestAccess::buildings(sim).placeImmediate(
+    return SimulationTestAccess::buildings(sim).placeImmediate(SimulationTestAccess::state(sim), BuildingType::Shipyard,
-        BuildingType::Shipyard,
         yardDef.surfaceMask,
         QPoint(0, 0),
         Rotation::East);
@@ -75,7 +74,7 @@ static int countShips(Simulation& sim)
 
 static void fillMaterials(Simulation& sim, BuildingId yardId, const ShipDef& def)
 {
-    SimulationTestAccess::buildings(sim).forEachBuilding([&](Building& b)
+    SimulationTestAccess::buildings(sim).forEachBuilding(SimulationTestAccess::state(sim), [&](Building& b)
     {
         if (b.id != yardId)
         {
@@ -107,7 +106,7 @@ TEST_CASE("Shipyard: spawns a player ship after production cycle completes",
     const BuildingId yardId = placeShipyard(sim, *yardDef);
     REQUIRE(yardId != kInvalidBuildingId);
 
-    SimulationTestAccess::buildings(sim).setRecipe(yardId, def->id);
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), yardId, def->id);
     fillMaterials(sim, yardId, *def);
 
     // First tick: materials consumed, production cycle starts — no ship yet.
@@ -166,7 +165,7 @@ TEST_CASE("Shipyard: does not spawn with insufficient materials", "[shipyard]")
     const int shipsBefore = countShips(sim);
 
     const BuildingId yardId = placeShipyard(sim, *yardDef);
-    SimulationTestAccess::buildings(sim).setRecipe(yardId, def->id);
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), yardId, def->id);
     // Materials remain at zero (default after setRecipe); no cycle starts.
 
     const Tick cycleTicks = secondsToTicks(def->schematic.productionTimeSeconds);
@@ -188,7 +187,7 @@ TEST_CASE("Shipyard: spawns a second ship after materials replenished", "[shipya
     REQUIRE(yardDef != nullptr);
 
     const BuildingId yardId = placeShipyard(sim, *yardDef);
-    SimulationTestAccess::buildings(sim).setRecipe(yardId, def->id);
+    SimulationTestAccess::buildings(sim).setRecipe(SimulationTestAccess::state(sim), yardId, def->id);
 
     const Tick cycleTicks = secondsToTicks(def->schematic.productionTimeSeconds);
 

src/test/SimulationTestAccess.h

@@ -7,6 +7,7 @@
 #include "BuildingId.h"
 #include "BuildingType.h"
 #include "Rotation.h"
+#include "FactoryState.h"
 #include "Simulation.h"
 
 class BeltSystem;
@@ -25,6 +26,7 @@ class BuildingSystem;
 struct SimulationTestAccess
 {
     static BuildingSystem& buildings(Simulation& sim) { return sim.getBuildingsMutable(); }
+    static FactoryState&   state(Simulation& sim)     { return sim.m_factoryState; }
     static BeltSystem&     belts(Simulation& sim)     { return sim.getBeltsMutable(); }
 
     static std::optional<BuildingId> place(Simulation& sim, BuildingType type,

src/ui/FieldSelectionPanel.cpp

@@ -367,7 +367,7 @@ int FieldSelectionPanel::selectedDebrisScrapTotal() const
 {
     // Sum the remaining scrap across the still-living selected debris (REQ-UI-DEBRIS-PANEL).
     int total = 0;
-    for (const DebrisInfo& info : m_sim->getDebrisSystem().getAllDebrisInfo())
+    for (const DebrisInfo& info : getAllDebrisInfo(m_sim->getAdmin()))
     {
         if (std::find(m_selectedDebris.begin(), m_selectedDebris.end(), info.entity)
             != m_selectedDebris.end())

src/ui/GameWorldView.cpp

@@ -777,7 +777,7 @@ void GameWorldView::pruneDespawnedDebris()
     if (m_selectedDebris.empty()) { return; }
 
     std::vector<entt::entity> live;
-    for (const DebrisInfo& info : m_sim->getDebrisSystem().getAllDebrisInfo())
+    for (const DebrisInfo& info : getAllDebrisInfo(m_sim->getAdmin()))
     {
         if (std::find(m_selectedDebris.begin(), m_selectedDebris.end(), info.entity)
             != m_selectedDebris.end())
@@ -1510,7 +1510,7 @@ void GameWorldView::drawSelectionHighlights(QPainter& painter)
     if (!m_selectedDebris.empty())
     {
         const qreal outlineRadius = static_cast<qreal>(getTilePx() * 0.2f) + 3.0;
-        for (const DebrisInfo& debris : m_sim->getDebrisSystem().getAllDebrisInfo())
+        for (const DebrisInfo& debris : getAllDebrisInfo(m_sim->getAdmin()))
         {
             if (std::find(m_selectedDebris.begin(), m_selectedDebris.end(), debris.entity)
                 == m_selectedDebris.end()) { continue; }
@@ -1605,8 +1605,8 @@ void GameWorldView::drawPortItems(QPainter& painter)
 
     painter.save();
     painter.setClipRegion(clip);
-    m_sim->getBuildings().forEachEmergingItem(drawItem);
+    m_sim->getBuildings().forEachEmergingItem(m_sim->getFactoryState(), drawItem);
-    m_sim->getBuildings().forEachIncomingItem(drawItem);
+    m_sim->getBuildings().forEachIncomingItem(m_sim->getFactoryState(), drawItem);
     painter.restore();
 }
 
@@ -1654,7 +1654,7 @@ void GameWorldView::drawBeltItems(QPainter& painter)
 void GameWorldView::drawDebris(QPainter& painter)
 {
     const float r = getTilePx() * 0.2f;
-    for (const DebrisInfo& debris : m_sim->getDebrisSystem().getAllDebrisInfo())
+    for (const DebrisInfo& debris : getAllDebrisInfo(m_sim->getAdmin()))
     {
         const QPointF center = worldToWidget(debris.position);
         painter.setBrush(QColor(128, 110, 90));