diff --git a/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/DeterministicFaultPlan.java b/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/DeterministicFaultPlan.java
new file mode 100644
index 0000000..cd5e042
--- /dev/null
+++ b/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/DeterministicFaultPlan.java
@@ -0,0 +1,105 @@
+package com.ft546.wcs.shadow.history.simulation;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+public final class DeterministicFaultPlan {
+    public enum VehicleEventType {
+        DISCONNECT, CONNECT, RESTART, SYNCHRONIZE,
+        LOW_BATTERY, RESTORE_BATTERY, FAULT, RECOVER
+    }
+
+    public static final class VehicleEvent {
+        private final String vehicleId;
+        private final VehicleEventType type;
+
+        private VehicleEvent(String vehicleId, VehicleEventType type) {
+            this.vehicleId = vehicleId;
+            this.type = type;
+        }
+
+        public String getVehicleId() { return vehicleId; }
+        public VehicleEventType getType() { return type; }
+    }
+
+    private final Map<String, Map<Integer, SimulatedPlcGateway.PlcReason>> plcFailures;
+    private final Map<Long, List<VehicleEvent>> vehicleEvents;
+
+    private DeterministicFaultPlan(
+            Map<String, Map<Integer, SimulatedPlcGateway.PlcReason>> plcFailures,
+            Map<Long, List<VehicleEvent>> vehicleEvents) {
+        this.plcFailures = plcFailures;
+        this.vehicleEvents = vehicleEvents;
+    }
+
+    public static Builder builder() { return new Builder(); }
+
+    public static DeterministicFaultPlan none() { return builder().build(); }
+
+    SimulatedPlcGateway.PlcReason plcReason(String taskId, int attempt) {
+        Map<Integer, SimulatedPlcGateway.PlcReason> byAttempt = plcFailures.get(taskId);
+        return byAttempt == null ? null : byAttempt.get(attempt);
+    }
+
+    public List<VehicleEvent> eventsAt(long eventNumber) {
+        List<VehicleEvent> events = vehicleEvents.get(eventNumber);
+        return events == null ? Collections.emptyList() : events;
+    }
+
+    public static final class Builder {
+        private final Map<String, Map<Integer, SimulatedPlcGateway.PlcReason>> plcFailures =
+                new LinkedHashMap<String, Map<Integer, SimulatedPlcGateway.PlcReason>>();
+        private final Map<Long, List<VehicleEvent>> vehicleEvents =
+                new LinkedHashMap<Long, List<VehicleEvent>>();
+
+        public Builder plcFailure(String taskId, int attempt,
+                                  SimulatedPlcGateway.PlcReason reason) {
+            if (taskId == null || attempt <= 0 || reason == null
+                    || reason == SimulatedPlcGateway.PlcReason.ACK
+                    || reason == SimulatedPlcGateway.PlcReason.STALE_BOOT_ID) {
+                throw new IllegalArgumentException("valid PLC failure is required");
+            }
+            Map<Integer, SimulatedPlcGateway.PlcReason> byAttempt = plcFailures.get(taskId);
+            if (byAttempt == null) {
+                byAttempt = new LinkedHashMap<Integer, SimulatedPlcGateway.PlcReason>();
+                plcFailures.put(taskId, byAttempt);
+            }
+            byAttempt.put(attempt, reason);
+            return this;
+        }
+
+        public Builder vehicleEvent(long eventNumber, String vehicleId, VehicleEventType type) {
+            if (eventNumber < 0 || vehicleId == null || vehicleId.trim().isEmpty() || type == null) {
+                throw new IllegalArgumentException("valid vehicle event is required");
+            }
+            List<VehicleEvent> events = vehicleEvents.get(eventNumber);
+            if (events == null) {
+                events = new ArrayList<VehicleEvent>();
+                vehicleEvents.put(eventNumber, events);
+            }
+            events.add(new VehicleEvent(vehicleId, type));
+            return this;
+        }
+
+        public DeterministicFaultPlan build() {
+            Map<String, Map<Integer, SimulatedPlcGateway.PlcReason>> plc =
+                    new LinkedHashMap<String, Map<Integer, SimulatedPlcGateway.PlcReason>>();
+            for (Map.Entry<String, Map<Integer, SimulatedPlcGateway.PlcReason>> entry
+                    : plcFailures.entrySet()) {
+                plc.put(entry.getKey(), Collections.unmodifiableMap(
+                        new LinkedHashMap<Integer, SimulatedPlcGateway.PlcReason>(entry.getValue())));
+            }
+            Map<Long, List<VehicleEvent>> vehicles =
+                    new LinkedHashMap<Long, List<VehicleEvent>>();
+            for (Map.Entry<Long, List<VehicleEvent>> entry : vehicleEvents.entrySet()) {
+                vehicles.put(entry.getKey(), Collections.unmodifiableList(
+                        new ArrayList<VehicleEvent>(entry.getValue())));
+            }
+            return new DeterministicFaultPlan(Collections.unmodifiableMap(plc),
+                    Collections.unmodifiableMap(vehicles));
+        }
+    }
+}
diff --git a/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/IdempotentWmsCompletionReceiver.java b/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/IdempotentWmsCompletionReceiver.java
new file mode 100644
index 0000000..8442291
--- /dev/null
+++ b/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/IdempotentWmsCompletionReceiver.java
@@ -0,0 +1,24 @@
+package com.ft546.wcs.shadow.history.simulation;
+
+import java.util.Collections;
+import java.util.LinkedHashSet;
+import java.util.Set;
+
+public final class IdempotentWmsCompletionReceiver {
+    private final Set<String> completedTaskIds = new LinkedHashSet<String>();
+    private int deliveryAttempts;
+
+    public boolean receive(String taskId) {
+        if (taskId == null || taskId.trim().isEmpty()) {
+            throw new IllegalArgumentException("task id is required");
+        }
+        deliveryAttempts++;
+        return completedTaskIds.add(taskId);
+    }
+
+    public int getDeliveryAttempts() { return deliveryAttempts; }
+    public int getBusinessEffects() { return completedTaskIds.size(); }
+    public Set<String> getCompletedTaskIds() {
+        return Collections.unmodifiableSet(completedTaskIds);
+    }
+}
diff --git a/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/SimulatedPlcGateway.java b/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/SimulatedPlcGateway.java
new file mode 100644
index 0000000..77cf8f4
--- /dev/null
+++ b/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/SimulatedPlcGateway.java
@@ -0,0 +1,77 @@
+package com.ft546.wcs.shadow.history.simulation;
+
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+public final class SimulatedPlcGateway {
+    public enum PlcReason {
+        ACK, SEND_FAILURE, ACK_TIMEOUT, ACK_LOST, STALE_BOOT_ID
+    }
+
+    public static final class PlcResponse {
+        private final String taskId;
+        private final String vehicleId;
+        private final String from;
+        private final String to;
+        private final int attempt;
+        private final long bootId;
+        private final PlcReason reason;
+
+        private PlcResponse(String taskId, String vehicleId, String from, String to,
+                            int attempt, long bootId, PlcReason reason) {
+            this.taskId = taskId;
+            this.vehicleId = vehicleId;
+            this.from = from;
+            this.to = to;
+            this.attempt = attempt;
+            this.bootId = bootId;
+            this.reason = reason;
+        }
+
+        public String getTaskId() { return taskId; }
+        public String getVehicleId() { return vehicleId; }
+        public String getFrom() { return from; }
+        public String getTo() { return to; }
+        public int getAttempt() { return attempt; }
+        public long getBootId() { return bootId; }
+        public PlcReason getReason() { return reason; }
+    }
+
+    private final DeterministicFaultPlan faults;
+    private final Map<String, Integer> attempts = new LinkedHashMap<String, Integer>();
+
+    public SimulatedPlcGateway(DeterministicFaultPlan faults) {
+        if (faults == null) throw new IllegalArgumentException("fault plan is required");
+        this.faults = faults;
+    }
+
+    public PlcResponse send(String taskId, SimulatedVehicleRuntime vehicle,
+                            String from, String to) {
+        int attempt = attempts.containsKey(taskId) ? attempts.get(taskId) + 1 : 1;
+        attempts.put(taskId, attempt);
+        PlcReason reason = faults.plcReason(taskId, attempt);
+        if (reason == null) reason = PlcReason.ACK;
+        return new PlcResponse(taskId, vehicle.getVehicleId(), from, to,
+                attempt, vehicle.getBootId(), reason);
+    }
+
+    public PlcResponse accept(PlcResponse response, SimulatedVehicleRuntime vehicle) {
+        if (response.getReason() != PlcReason.ACK) return response;
+        if (response.getBootId() != vehicle.getBootId()) {
+            return new PlcResponse(response.getTaskId(), response.getVehicleId(),
+                    response.getFrom(), response.getTo(), response.getAttempt(),
+                    response.getBootId(), PlcReason.STALE_BOOT_ID);
+        }
+        return response;
+    }
+
+    public int attemptsFor(String taskId) {
+        Integer value = attempts.get(taskId);
+        return value == null ? 0 : value;
+    }
+
+    public Map<String, Integer> getAttempts() {
+        return Collections.unmodifiableMap(attempts);
+    }
+}
diff --git a/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/SimulatedVehicleRuntime.java b/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/SimulatedVehicleRuntime.java
new file mode 100644
index 0000000..c735e4e
--- /dev/null
+++ b/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/SimulatedVehicleRuntime.java
@@ -0,0 +1,78 @@
+package com.ft546.wcs.shadow.history.simulation;
+
+import com.ft546.wcs.demo.model.VehicleSnapshot;
+
+public final class SimulatedVehicleRuntime {
+    private final String vehicleId;
+    private String currentSite;
+    private int floor;
+    private int battery = 100;
+    private boolean connected = true;
+    private boolean faulted;
+    private boolean synchronizedAfterBoot = true;
+    private long bootId = 1L;
+
+    public SimulatedVehicleRuntime(String vehicleId, String currentSite, int floor) {
+        if (vehicleId == null || vehicleId.trim().isEmpty()
+                || currentSite == null || currentSite.trim().isEmpty() || floor <= 0) {
+            throw new IllegalArgumentException("valid vehicle identity and position are required");
+        }
+        this.vehicleId = vehicleId;
+        this.currentSite = currentSite;
+        this.floor = floor;
+    }
+
+    public static SimulatedVehicleRuntime from(VehicleSnapshot snapshot) {
+        SimulatedVehicleRuntime runtime = new SimulatedVehicleRuntime(
+                snapshot.getVehicleId(), snapshot.getCurrentSite(), snapshot.getFloor());
+        runtime.battery = snapshot.getBattery();
+        runtime.connected = snapshot.isConnected();
+        return runtime;
+    }
+
+    public boolean isAssignmentEligible() {
+        return connected && !faulted && synchronizedAfterBoot && battery > 30;
+    }
+
+    public void disconnect() { connected = false; }
+    public void connect() { connected = true; }
+    public void fail() { faulted = true; }
+    public void recover() { faulted = false; }
+
+    public void restart() {
+        bootId++;
+        synchronizedAfterBoot = false;
+    }
+
+    public void synchronizeAfterRestart() { synchronizedAfterBoot = true; }
+
+    public void setBattery(int battery) {
+        if (battery < 0 || battery > 100) {
+            throw new IllegalArgumentException("battery must be between 0 and 100");
+        }
+        this.battery = battery;
+    }
+
+    public void moveTo(String site, int newFloor) {
+        if (site == null || site.trim().isEmpty() || newFloor <= 0) {
+            throw new IllegalArgumentException("valid destination is required");
+        }
+        currentSite = site;
+        floor = newFloor;
+    }
+
+    public VehicleSnapshot snapshot() {
+        return new VehicleSnapshot(vehicleId, floor, currentSite, 5,
+                faulted ? 0 : 1, battery, connected,
+                connected && !faulted && synchronizedAfterBoot, false);
+    }
+
+    public String getVehicleId() { return vehicleId; }
+    public String getCurrentSite() { return currentSite; }
+    public int getFloor() { return floor; }
+    public int getBattery() { return battery; }
+    public long getBootId() { return bootId; }
+    public boolean isConnected() { return connected; }
+    public boolean isFaulted() { return faulted; }
+    public boolean isSynchronizedAfterBoot() { return synchronizedAfterBoot; }
+}
diff --git a/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/SimulationArchive.java b/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/SimulationArchive.java
new file mode 100644
index 0000000..fb9637a
--- /dev/null
+++ b/javaTest/src/main/java/com/ft546/wcs/shadow/history/simulation/SimulationArchive.java
@@ -0,0 +1,37 @@
+package com.ft546.wcs.shadow.history.simulation;
+
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+public final class SimulationArchive {
+    public static final class ArchiveRecord {
+        private final String taskId;
+        private final String vehicleId;
+        private final long completedAtMillis;
+
+        private ArchiveRecord(String taskId, String vehicleId, long completedAtMillis) {
+            this.taskId = taskId;
+            this.vehicleId = vehicleId;
+            this.completedAtMillis = completedAtMillis;
+        }
+
+        public String getTaskId() { return taskId; }
+        public String getVehicleId() { return vehicleId; }
+        public long getCompletedAtMillis() { return completedAtMillis; }
+    }
+
+    private final Map<String, ArchiveRecord> records =
+            new LinkedHashMap<String, ArchiveRecord>();
+
+    public boolean complete(String taskId, String vehicleId, long completedAtMillis) {
+        if (records.containsKey(taskId)) return false;
+        records.put(taskId, new ArchiveRecord(taskId, vehicleId, completedAtMillis));
+        return true;
+    }
+
+    public int size() { return records.size(); }
+    public Map<String, ArchiveRecord> getRecords() {
+        return Collections.unmodifiableMap(records);
+    }
+}
diff --git a/javaTest/src/test/java/com/ft546/wcs/shadow/history/simulation/SimulationAdaptersTest.java b/javaTest/src/test/java/com/ft546/wcs/shadow/history/simulation/SimulationAdaptersTest.java
new file mode 100644
index 0000000..09b14e4
--- /dev/null
+++ b/javaTest/src/test/java/com/ft546/wcs/shadow/history/simulation/SimulationAdaptersTest.java
@@ -0,0 +1,61 @@
+package com.ft546.wcs.shadow.history.simulation;
+
+import org.junit.jupiter.api.Test;
+
+import static com.ft546.wcs.shadow.history.simulation.SimulatedPlcGateway.PlcReason.ACK;
+import static com.ft546.wcs.shadow.history.simulation.SimulatedPlcGateway.PlcReason.SEND_FAILURE;
+import static com.ft546.wcs.shadow.history.simulation.SimulatedPlcGateway.PlcReason.STALE_BOOT_ID;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class SimulationAdaptersTest {
+    @Test
+    void retriesDeterministicSendFailureAndRejectsAckFromAnOldBoot() {
+        DeterministicFaultPlan faults = DeterministicFaultPlan.builder()
+                .plcFailure("T1", 1, SEND_FAILURE).build();
+        SimulatedPlcGateway plc = new SimulatedPlcGateway(faults);
+        SimulatedVehicleRuntime vehicle = new SimulatedVehicleRuntime("1", "A", 1);
+
+        assertEquals(SEND_FAILURE, plc.send("T1", vehicle, "A", "B").getReason());
+        SimulatedPlcGateway.PlcResponse ack = plc.send("T1", vehicle, "A", "B");
+        assertEquals(ACK, ack.getReason());
+        assertEquals(ACK, plc.accept(ack, vehicle).getReason());
+
+        vehicle.restart();
+        assertEquals(STALE_BOOT_ID, plc.accept(ack, vehicle).getReason());
+        vehicle.synchronizeAfterRestart();
+        assertTrue(vehicle.isAssignmentEligible());
+    }
+
+    @Test
+    void excludesDisconnectedLowBatteryAndFaultedVehiclesUntilRecovery() {
+        SimulatedVehicleRuntime vehicle = new SimulatedVehicleRuntime("1", "A", 1);
+        assertTrue(vehicle.isAssignmentEligible());
+        vehicle.disconnect();
+        assertFalse(vehicle.isAssignmentEligible());
+        vehicle.connect();
+        vehicle.setBattery(29);
+        assertFalse(vehicle.isAssignmentEligible());
+        vehicle.setBattery(100);
+        vehicle.fail();
+        assertFalse(vehicle.isAssignmentEligible());
+        vehicle.recover();
+        assertTrue(vehicle.isAssignmentEligible());
+    }
+
+    @Test
+    void archivesAndAppliesWmsCompletionExactlyOnceAcrossDuplicateDelivery() {
+        SimulationArchive archive = new SimulationArchive();
+        IdempotentWmsCompletionReceiver wms = new IdempotentWmsCompletionReceiver();
+
+        assertTrue(archive.complete("T1", "1", 123L));
+        assertFalse(archive.complete("T1", "1", 123L));
+        assertTrue(wms.receive("T1"));
+        assertFalse(wms.receive("T1"));
+
+        assertEquals(1, archive.size());
+        assertEquals(2, wms.getDeliveryAttempts());
+        assertEquals(1, wms.getBusinessEffects());
+    }
+}