diff --git a/demos/openplc_tank/.gitignore b/demos/openplc_tank/.gitignore
new file mode 100644
index 0000000..3e57ad9
--- /dev/null
+++ b/demos/openplc_tank/.gitignore
@@ -0,0 +1 @@
+demos/openplc_tank/openplc/generated/
diff --git a/demos/openplc_tank/README.md b/demos/openplc_tank/README.md
new file mode 100644
index 0000000..dcd48c2
--- /dev/null
+++ b/demos/openplc_tank/README.md
@@ -0,0 +1,103 @@
+# OpenPLC Tank Demo
+
+PLC diagnostics demo using OpenPLC v4 + ros2_medkit OPC-UA plugin.
+
+## Architecture
+
+```
+OpenPLC v4 Runtime (Docker)           ros2_medkit Gateway
+  [Tank ST program]                     [opcua_plugin.so]
+  OPC-UA Server :4840  <-- sub -->   open62541pp client
+                                        |
+                                      OpcuaPoller
+                                        |
+                                +---------+---------+
+                                |         |         |
+                          IntrospectionProvider   REST   FaultManager
+                          (PLC entity tree)      routes  (alarm->fault)
+```
+
+## SOVD Entity Tree
+
+```
+Area: plc_systems
+  Component: openplc_runtime
+    App: tank_process     (level, temperature, pressure + alarms)
+    App: fill_pump        (speed control)
+    App: drain_valve      (position control)
+```
+
+## Quick Start
+
+```bash
+./scripts/run-demo.sh
+
+# Wait ~30s for startup, then:
+curl http://localhost:8080/api/v1/health
+curl http://localhost:8080/api/v1/apps | jq '.items[].id'
+curl http://localhost:8080/api/v1/apps/tank_process/x-plc-data | jq .
+```
+
+## Endpoints
+
+| Method | Path | Description |
+|--------|------|-------------|
+| GET | `/api/v1/areas` | List areas (plc_systems) |
+| GET | `/api/v1/components` | List components (openplc_runtime) |
+| GET | `/api/v1/apps` | List apps (tank_process, fill_pump, drain_valve) |
+| GET | `/apps/{id}/x-plc-data` | All OPC-UA values for entity |
+| GET | `/apps/{id}/x-plc-data/{node}` | Single value |
+| POST | `/apps/{id}/x-plc-operations/{op}` | Write value `{"value": 75.0}` |
+| GET | `/components/{id}/x-plc-status` | Connection state, stats |
+| GET | `/apps/{id}/faults` | SOVD faults (from PLC alarms) |
+
+## Fault Injection
+
+```bash
+# Inject high temperature (>80C threshold)
+./scripts/inject-fault.sh high_temp
+
+# Inject low level (<100mm threshold)
+./scripts/inject-fault.sh low_level
+
+# Inject overpressure (>5bar threshold)
+./scripts/inject-fault.sh overpressure
+
+# Restore normal operation
+./scripts/restore-normal.sh
+```
+
+## Control PLC via REST
+
+```bash
+# Set pump speed to 75%
+curl -X POST http://localhost:8080/api/v1/apps/fill_pump/x-plc-operations/set_pump_speed \
+  -H "Content-Type: application/json" -d '{"value": 75.0}'
+
+# Set valve position to 50%
+curl -X POST http://localhost:8080/api/v1/apps/drain_valve/x-plc-operations/set_valve_position \
+  -H "Content-Type: application/json" -d '{"value": 50.0}'
+```
+
+## Integration Tests
+
+```bash
+./scripts/run_integration_tests.sh
+```
+
+Tests cover: entity discovery, live data, control writes, fault lifecycle, connection resilience, error responses.
+
+## Ports
+
+| Service | Port | Protocol |
+|---------|------|----------|
+| OpenPLC OPC-UA | 4840 | OPC-UA TCP |
+| Gateway REST | 8080 | HTTP |
+| Web UI | 3000 | HTTP |
+
+## Stopping
+
+```bash
+./scripts/stop-demo.sh          # stop containers
+./scripts/stop-demo.sh --volumes # stop + remove volumes
+```
diff --git a/demos/openplc_tank/config/gateway_params.yaml b/demos/openplc_tank/config/gateway_params.yaml
new file mode 100644
index 0000000..bd25665
--- /dev/null
+++ b/demos/openplc_tank/config/gateway_params.yaml
@@ -0,0 +1,57 @@
+# Gateway parameters for OpenPLC Tank Demo
+# Namespace: diagnostics/ros2_medkit_gateway
+diagnostics:
+  ros2_medkit_gateway:
+    ros__parameters:
+      server:
+        host: "0.0.0.0"
+        port: 8080
+
+      cors:
+        allowed_origins: ["*"]
+        allowed_methods: [GET, PUT, POST, DELETE, OPTIONS]
+        allowed_headers: [Content-Type, Accept]
+        allow_credentials: false
+
+      discovery:
+        mode: "hybrid"
+        manifest_path: "/config/tank_manifest.yaml"
+        manifest_strict_validation: true
+        runtime:
+          create_synthetic_components: false
+
+      max_parallel_topic_samples: 10
+
+      # Plugin configuration
+      plugins: ["opcua"]
+      plugins.opcua.path: "/plugin_ws/install/opcua_gateway_plugin/lib/opcua_gateway_plugin/opcua_gateway_plugin.so"
+      plugins.opcua.endpoint_url: "opc.tcp://openplc:4840"
+      plugins.opcua.node_map_path: "/config/tank_nodes.yaml"
+      plugins.opcua.prefer_subscriptions: true
+      plugins.opcua.subscription_interval_ms: 500.0
+      plugins.opcua.poll_interval_ms: 1000
+
+      # Triggers
+      triggers:
+        enabled: true
+        max_triggers: 100
+
+      # Documentation
+      docs:
+        enabled: true
+
+# Fault Manager parameters
+fault_manager:
+  ros__parameters:
+    storage_type: "sqlite"
+    database_path: "/var/lib/ros2_medkit/faults.db"
+
+    confirmation_threshold: 0
+    healing_enabled: false
+    auto_confirm_after_sec: 0.0
+
+    snapshots:
+      enabled: false
+
+    rosbag:
+      enabled: false
diff --git a/demos/openplc_tank/config/tank_manifest.yaml b/demos/openplc_tank/config/tank_manifest.yaml
new file mode 100644
index 0000000..a304c65
--- /dev/null
+++ b/demos/openplc_tank/config/tank_manifest.yaml
@@ -0,0 +1,47 @@
+# SOVD Entity Manifest for OpenPLC Tank Demo
+# Defines the static entity tree structure
+# Dynamic data comes from the OPC-UA plugin at runtime
+
+areas:
+  - id: plc_systems
+    name: PLC Systems
+    description: PLC systems connected via OPC-UA
+
+components:
+  - id: openplc_runtime
+    name: OpenPLC Runtime
+    area: plc_systems
+    description: OpenPLC v4 runtime with OPC-UA server
+    tags:
+      - plc
+      - opcua
+      - simulation
+
+apps:
+  - id: tank_process
+    name: Tank Process
+    component_id: openplc_runtime
+    external: true
+    description: Tank simulation - level, temperature, pressure sensors with alarms
+    tags:
+      - sensors
+      - alarms
+      - tank
+
+  - id: fill_pump
+    name: Fill Pump
+    component_id: openplc_runtime
+    external: true
+    description: Fill pump with speed control (0-100%)
+    tags:
+      - actuator
+      - pump
+
+  - id: drain_valve
+    name: Drain Valve
+    component_id: openplc_runtime
+    external: true
+    description: Drain valve with position control (0-100%)
+    tags:
+      - actuator
+      - valve
diff --git a/demos/openplc_tank/config/tank_nodes.yaml b/demos/openplc_tank/config/tank_nodes.yaml
new file mode 100644
index 0000000..3d9b889
--- /dev/null
+++ b/demos/openplc_tank/config/tank_nodes.yaml
@@ -0,0 +1,84 @@
+# OPC-UA Node Map for OpenPLC Tank Demo
+# Maps OPC-UA NodeIds to SOVD entity data points
+
+area_id: plc_systems
+area_name: PLC Systems
+component_id: openplc_runtime
+component_name: OpenPLC Runtime
+auto_browse: false
+
+nodes:
+  # === Tank Process - Sensor Readings ===
+  - node_id: "ns=1;s=TankLevel"
+    entity_id: tank_process
+    data_name: tank_level
+    display_name: Tank Level
+    unit: mm
+    data_type: float
+    writable: false
+    alarm:
+      fault_code: PLC_LOW_LEVEL
+      severity: WARNING
+      message: Tank level below minimum (100mm)
+      threshold: 100.0
+      above_threshold: false
+
+  - node_id: "ns=1;s=TankTemperature"
+    entity_id: tank_process
+    data_name: tank_temperature
+    display_name: Tank Temperature
+    unit: C
+    data_type: float
+    writable: false
+    alarm:
+      fault_code: PLC_HIGH_TEMP
+      severity: ERROR
+      message: Tank temperature above maximum (80C)
+      threshold: 80.0
+      above_threshold: true
+
+  - node_id: "ns=1;s=TankPressure"
+    entity_id: tank_process
+    data_name: tank_pressure
+    display_name: Tank Pressure
+    unit: bar
+    data_type: float
+    writable: false
+    alarm:
+      fault_code: PLC_OVERPRESSURE
+      severity: ERROR
+      message: Tank pressure above maximum (5 bar)
+      threshold: 5.0
+      above_threshold: true
+
+  # === Fill Pump - Speed Control ===
+  - node_id: "ns=1;s=PumpSpeed"
+    entity_id: fill_pump
+    data_name: pump_speed
+    display_name: Pump Speed Setpoint
+    unit: "%"
+    data_type: float
+    writable: true
+
+  - node_id: "ns=1;s=PumpRunning"
+    entity_id: fill_pump
+    data_name: pump_running
+    display_name: Pump Running Status
+    data_type: bool
+    writable: false
+
+  # === Drain Valve - Position Control ===
+  - node_id: "ns=1;s=ValvePosition"
+    entity_id: drain_valve
+    data_name: valve_position
+    display_name: Valve Position Setpoint
+    unit: "%"
+    data_type: float
+    writable: true
+
+  - node_id: "ns=1;s=ValveOpen"
+    entity_id: drain_valve
+    data_name: valve_open
+    display_name: Valve Open Status
+    data_type: bool
+    writable: false
diff --git a/demos/openplc_tank/docker-compose.yml b/demos/openplc_tank/docker-compose.yml
new file mode 100644
index 0000000..e7543aa
--- /dev/null
+++ b/demos/openplc_tank/docker-compose.yml
@@ -0,0 +1,75 @@
+services:
+  # OpenPLC v4 runtime with tank simulation program
+  openplc:
+    build:
+      context: openplc/
+      dockerfile: Dockerfile
+    container_name: openplc_tank
+    ports:
+      - "4840:4840"   # OPC-UA server
+    restart: unless-stopped
+    healthcheck:
+      test: ["CMD", "curl", "-sf", "http://localhost:8080/api/health"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+      start_period: 30s
+
+  # ros2_medkit Gateway with OPC-UA plugin
+  gateway:
+    build:
+      context: gateway/
+      dockerfile: Dockerfile
+      additional_contexts:
+        ros2_medkit: ../../../ros2_medkit
+        opcua_gateway_plugin: ../../../platform/commercial/opcua_gateway_plugin
+        config: config/
+    container_name: openplc_gateway
+    environment:
+      - ROS_DOMAIN_ID=50
+    ports:
+      - "8080:8080"
+    depends_on:
+      openplc:
+        condition: service_started
+    restart: unless-stopped
+
+  # SOVD Web UI
+  sovd-web-ui:
+    image: ghcr.io/selfpatch/sovd_web_ui:latest
+    container_name: sovd_web_ui
+    ports:
+      - "3000:80"
+    depends_on:
+      - gateway
+
+  # CI testing profile - headless validation
+  gateway-ci:
+    profiles: ["ci"]
+    build:
+      context: gateway/
+      dockerfile: Dockerfile
+      additional_contexts:
+        ros2_medkit: ../../../ros2_medkit
+        opcua_gateway_plugin: ../../../platform/commercial/opcua_gateway_plugin
+        config: config/
+    container_name: openplc_gateway_ci
+    environment:
+      - ROS_DOMAIN_ID=50
+    ports:
+      - "8080:8080"
+    depends_on:
+      openplc:
+        condition: service_started
+    command: >
+      bash -c "mkdir -p /var/lib/ros2_medkit/rosbags &&
+               source /opt/ros/jazzy/setup.bash &&
+               source /medkit_ws/install/setup.bash &&
+               source /plugin_ws/install/setup.bash &&
+               ros2 run ros2_medkit_gateway gateway_node \
+                 --ros-args --params-file /config/gateway_params.yaml &
+               sleep 15 &&
+               curl -sf http://localhost:8080/api/v1/health &&
+               curl -sf http://localhost:8080/api/v1/areas | jq '.items[] | .id' &&
+               curl -sf http://localhost:8080/api/v1/apps | jq '.items[] | .id' &&
+               echo 'CI validation passed!'"
diff --git a/demos/openplc_tank/gateway/Dockerfile b/demos/openplc_tank/gateway/Dockerfile
new file mode 100644
index 0000000..510fa8c
--- /dev/null
+++ b/demos/openplc_tank/gateway/Dockerfile
@@ -0,0 +1,80 @@
+# Multi-stage build: ros2_medkit gateway + OPC-UA plugin
+# Stage 1: Build ros2_medkit
+# Stage 2: Build OPC-UA plugin against installed medkit headers
+# Stage 3: Runtime
+
+# ---- Stage 1: Build ros2_medkit ----
+FROM ros:jazzy AS medkit-builder
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+RUN apt-get update && apt-get install -y \
+    python3-colcon-common-extensions \
+    python3-rosdep \
+    libsqlite3-dev \
+    libssl-dev \
+    nlohmann-json3-dev \
+    libyaml-cpp-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+# Copy ros2_medkit source
+COPY ros2_medkit/ /medkit_ws/src/ros2_medkit/
+
+WORKDIR /medkit_ws
+
+# Build ros2_medkit
+RUN . /opt/ros/jazzy/setup.sh && \
+    colcon build \
+      --cmake-args -DCMAKE_BUILD_TYPE=Release \
+      --packages-up-to ros2_medkit_gateway ros2_medkit_fault_manager ros2_medkit_msgs ros2_medkit_cmake
+
+# ---- Stage 2: Build OPC-UA plugin ----
+FROM medkit-builder AS plugin-builder
+
+RUN apt-get update && apt-get install -y \
+    git \
+    && rm -rf /var/lib/apt/lists/*
+
+# Copy plugin source
+COPY opcua_gateway_plugin/ /plugin_ws/src/opcua_gateway_plugin/
+
+WORKDIR /plugin_ws
+
+# Build plugin against installed medkit
+RUN . /opt/ros/jazzy/setup.sh && \
+    . /medkit_ws/install/setup.sh && \
+    colcon build \
+      --cmake-args -DCMAKE_BUILD_TYPE=Release
+
+# ---- Stage 3: Runtime ----
+FROM ros:jazzy
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+RUN apt-get update && apt-get install -y \
+    libsqlite3-0 \
+    libssl3 \
+    libyaml-cpp0.8 \
+    curl \
+    jq \
+    && rm -rf /var/lib/apt/lists/*
+
+# Copy medkit install
+COPY --from=medkit-builder /medkit_ws/install/ /medkit_ws/install/
+
+# Copy plugin install
+COPY --from=plugin-builder /plugin_ws/install/ /plugin_ws/install/
+
+# Copy configuration files
+COPY config/ /config/
+
+EXPOSE 8080
+
+# Start gateway with plugin
+CMD ["bash", "-c", \
+     "mkdir -p /var/lib/ros2_medkit/rosbags && \
+      source /opt/ros/jazzy/setup.bash && \
+      source /medkit_ws/install/setup.bash && \
+      source /plugin_ws/install/setup.bash && \
+      ros2 run ros2_medkit_gateway gateway_node \
+        --ros-args --params-file /config/gateway_params.yaml"]
diff --git a/demos/openplc_tank/openplc/Dockerfile b/demos/openplc_tank/openplc/Dockerfile
new file mode 100644
index 0000000..2dd1ba9
--- /dev/null
+++ b/demos/openplc_tank/openplc/Dockerfile
@@ -0,0 +1,88 @@
+# OpenPLC Runtime v4 (Autonomy-Logic) with tank demo
+# Strategy: Build runtime, then at startup use the web API to upload,
+# compile and start the ST program through OpenPLC's full pipeline.
+
+FROM debian:bookworm-slim AS matiec-builder
+
+RUN apt-get update && apt-get install -y \
+    git build-essential flex bison autoconf automake \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN git clone --depth 1 https://github.com/beremiz/matiec.git /matiec && \
+    cd /matiec && autoreconf -i && ./configure && make -j$(nproc) && make install
+
+
+FROM debian:bookworm-slim
+
+ENV DEBIAN_FRONTEND=noninteractive
+WORKDIR /openplc
+
+RUN apt-get update && apt-get install -y git ca-certificates curl jq && \
+    git clone --depth 1 https://github.com/Autonomy-Logic/openplc-runtime.git /openplc && \
+    rm -rf /var/lib/apt/lists/*
+
+RUN mkdir -p /var/run/runtime && \
+    chmod +x install.sh scripts/* start_openplc.sh && \
+    rm -rf build/ venvs/ .venv/ 2>/dev/null || true && \
+    ./install.sh && \
+    rm -rf /var/lib/apt/lists/*
+
+# Enable OPC-UA plugin and install config
+RUN sed -i 's/^opcua,\(.*\),0,0,/opcua,\1,1,0,/' plugins.conf
+COPY opcua_config.json /openplc/core/src/drivers/plugins/python/opcua/opcua.json
+
+# Copy matiec for ST -> C compilation
+COPY --from=matiec-builder /usr/local/bin/iec2c /usr/local/bin/iec2c
+COPY --from=matiec-builder /matiec/lib /matiec/lib
+
+# Copy tank demo ST program
+COPY tank_demo.st /openplc/programs/tank_demo.st
+
+# Pre-compile ST -> C and place in core/generated with proper IEC lib
+RUN mkdir -p /openplc/core/generated && \
+    iec2c -I /matiec/lib -T /openplc/core/generated /openplc/programs/tank_demo.st && \
+    cp -r /matiec/lib/C/* /openplc/core/generated/lib/ 2>/dev/null; \
+    mkdir -p /openplc/core/generated/lib && \
+    cp -r /matiec/lib/C/* /openplc/core/generated/lib/
+
+# Copy hand-written glueVars that implements all required runtime symbols
+COPY glueVars_tank.c /openplc/core/generated/glueVars.c
+
+# debug.c stub
+RUN cat > /openplc/core/generated/debug.c << 'EOF'
+#include "iec_std_lib.h"
+int __debug_tick;
+void __cleanup(void) {}
+void __retrieve(void) {}
+void __publish(void) {}
+EOF
+
+# Empty c_blocks_code
+RUN echo '// no custom C blocks' > /openplc/core/generated/c_blocks_code.cpp
+
+# Create entrypoint
+RUN cat > /entrypoint.sh << 'BASH'
+#!/bin/bash
+set -e
+cd /openplc
+
+# Try to compile the PLC program
+echo "Compiling PLC program..."
+if bash scripts/compile.sh 2>&1; then
+    # Rename to pattern expected by runtime
+    if [ -f build/new_libplc.so ]; then
+        mv build/new_libplc.so build/libplc_tank.so
+        echo "PLC program compiled successfully"
+    fi
+else
+    echo "WARNING: Compilation failed, runtime will start without PLC program"
+fi
+
+echo "Starting OpenPLC runtime..."
+exec bash start_openplc.sh
+BASH
+RUN chmod +x /entrypoint.sh
+
+EXPOSE 8443 4840
+
+CMD ["/entrypoint.sh"]
diff --git a/demos/openplc_tank/openplc/glueVars_tank.c b/demos/openplc_tank/openplc/glueVars_tank.c
new file mode 100644
index 0000000..bad0f1d
--- /dev/null
+++ b/demos/openplc_tank/openplc/glueVars_tank.c
@@ -0,0 +1,118 @@
+/* glueVars.c - Generated for tank_demo.st
+ * Provides LOCATED variable storage and buffer glue for OpenPLC v4 runtime.
+ */
+
+#include "iec_std_lib.h"
+
+#define BUFFER_SIZE 1024
+
+// Buffer declarations (defined in image_tables.c via plcapp_manager)
+extern IEC_UINT *int_memory[];
+extern IEC_UDINT *dint_memory[];
+extern IEC_ULINT *lint_memory[];
+extern IEC_BOOL *bool_memory[][8];
+
+// Backing storage for LOCATED variables
+// These are the globals that __INIT_LOCATED references via extern
+REAL __md0_storage;
+REAL __md1_storage;
+REAL __md2_storage;
+REAL __md3_storage;
+REAL __md5_storage;
+BOOL __mx16_0_storage;
+BOOL __mx24_0_storage;
+BOOL __mx24_1_storage;
+BOOL __mx24_2_storage;
+BOOL __mx24_3_storage;
+
+// Global pointers that POUS.c __INIT_LOCATED expects
+REAL *__MD0 = &__md0_storage;
+REAL *__MD1 = &__md1_storage;
+REAL *__MD2 = &__md2_storage;
+REAL *__MD3 = &__md3_storage;
+REAL *__MD5 = &__md5_storage;
+BOOL *__MX16_0 = &__mx16_0_storage;
+BOOL *__MX24_0 = &__mx24_0_storage;
+BOOL *__MX24_1 = &__mx24_1_storage;
+BOOL *__MX24_2 = &__mx24_2_storage;
+BOOL *__MX24_3 = &__mx24_3_storage;
+
+void glueVars()
+{
+    // Map LOCATED variables to runtime memory buffers
+    // REAL vars -> dint_memory (32-bit)
+    if (dint_memory[0]) __MD0 = (REAL *)dint_memory[0];
+    if (dint_memory[1]) __MD1 = (REAL *)dint_memory[1];
+    if (dint_memory[2]) __MD2 = (REAL *)dint_memory[2];
+    if (dint_memory[3]) __MD3 = (REAL *)dint_memory[3];
+    if (dint_memory[5]) __MD5 = (REAL *)dint_memory[5];
+
+    // BOOL vars -> bool_memory
+    if (bool_memory[16][0]) __MX16_0 = bool_memory[16][0];
+    if (bool_memory[24][0]) __MX24_0 = bool_memory[24][0];
+    if (bool_memory[24][1]) __MX24_1 = bool_memory[24][1];
+    if (bool_memory[24][2]) __MX24_2 = bool_memory[24][2];
+    if (bool_memory[24][3]) __MX24_3 = bool_memory[24][3];
+}
+
+void updateTime() {}
+void updateBuffersIn() {}
+void updateBuffersOut() {}
+
+// --- Required symbols for OpenPLC v4 runtime ---
+
+void setBufferPointers(
+    IEC_BOOL *bi[][8], IEC_BOOL *bo[][8],
+    IEC_BYTE *ib[], IEC_BYTE *ob[],
+    IEC_UINT *ii[], IEC_UINT *io[],
+    IEC_UDINT *di[], IEC_UDINT *do_[],
+    IEC_ULINT *li[], IEC_ULINT *lo[],
+    IEC_UINT *im[], IEC_UDINT *dm[],
+    IEC_ULINT *lm[])
+{
+    (void)bi; (void)bo; (void)ib; (void)ob;
+    (void)ii; (void)io; (void)di; (void)do_;
+    (void)li; (void)lo; (void)im; (void)dm; (void)lm;
+}
+
+void setBufferPointers_v4(
+    IEC_BOOL *bi[][8], IEC_BOOL *bo[][8],
+    IEC_BYTE *ib[], IEC_BYTE *ob[],
+    IEC_UINT *ii[], IEC_UINT *io[],
+    IEC_UDINT *di[], IEC_UDINT *do_[],
+    IEC_ULINT *li[], IEC_ULINT *lo[],
+    IEC_UINT *im[], IEC_UDINT *dm[],
+    IEC_ULINT *lm[], IEC_BOOL *bm[][8])
+{
+    (void)bi; (void)bo; (void)ib; (void)ob;
+    (void)ii; (void)io; (void)di; (void)do_;
+    (void)li; (void)lo; (void)im; (void)dm; (void)lm; (void)bm;
+}
+
+const char *plc_program_md5(void) { return "tank_demo_v1"; }
+void set_endianness(int e) { (void)e; }
+int get_var_count(void) { return 10; }
+int get_var_size(int idx) { return (idx < 6) ? 4 : 1; }
+
+// Debug/trace symbols required by runtime
+void *get_var_addr(int idx)
+{
+    switch (idx) {
+        case 0: return __MD0;
+        case 1: return __MD1;
+        case 2: return __MD2;
+        case 3: return __MD3;
+        case 4: return __MD5;
+        case 5: return __MX16_0;
+        case 6: return __MX24_0;
+        case 7: return __MX24_1;
+        case 8: return __MX24_2;
+        case 9: return __MX24_3;
+        default: return (void *)0;
+    }
+}
+
+void set_trace(int idx, int force, void *val)
+{
+    (void)idx; (void)force; (void)val;
+}
diff --git a/demos/openplc_tank/openplc/opcua_config.json b/demos/openplc_tank/openplc/opcua_config.json
new file mode 100644
index 0000000..36804a3
--- /dev/null
+++ b/demos/openplc_tank/openplc/opcua_config.json
@@ -0,0 +1,95 @@
+[
+  {
+    "name": "opcua_server",
+    "protocol": "OPC-UA",
+    "config": {
+      "server": {
+        "name": "OpenPLC Tank Demo",
+        "application_uri": "urn:selfpatch:openplc:tank",
+        "product_uri": "urn:selfpatch:openplc:tank",
+        "endpoint_url": "opc.tcp://0.0.0.0:4840/openplc/opcua",
+        "security_profiles": [
+          {
+            "name": "insecure",
+            "enabled": true,
+            "security_policy": "None",
+            "security_mode": "None",
+            "auth_methods": ["Anonymous"]
+          }
+        ]
+      },
+      "security": {
+        "server_certificate_strategy": "auto_self_signed",
+        "server_certificate_custom": null,
+        "server_private_key_custom": null,
+        "trusted_client_certificates": []
+      },
+      "users": [
+        {
+          "type": "password",
+          "username": "admin",
+          "password_hash": "$2b$12$dummy_hash_for_demo_only",
+          "role": "engineer"
+        }
+      ],
+      "cycle_time_ms": 100,
+      "address_space": {
+        "namespace_uri": "urn:selfpatch:openplc:tank:ns",
+        "variables": [
+          {
+            "node_id": "PLC.Tank.TankLevel",
+            "browse_name": "TankLevel",
+            "display_name": "Tank Level",
+            "datatype": "REAL",
+            "initial_value": 500.0,
+            "description": "Tank level in mm (0-1000)",
+            "index": 0,
+            "permissions": {"viewer": "rw", "operator": "rw", "engineer": "rw"}
+          },
+          {
+            "node_id": "PLC.Tank.TankTemperature",
+            "browse_name": "TankTemperature",
+            "display_name": "Tank Temperature",
+            "datatype": "REAL",
+            "initial_value": 25.0,
+            "description": "Tank temperature in C (0-120)",
+            "index": 1,
+            "permissions": {"viewer": "rw", "operator": "rw", "engineer": "rw"}
+          },
+          {
+            "node_id": "PLC.Tank.TankPressure",
+            "browse_name": "TankPressure",
+            "display_name": "Tank Pressure",
+            "datatype": "REAL",
+            "initial_value": 1.0,
+            "description": "Tank pressure in bar (0-10)",
+            "index": 2,
+            "permissions": {"viewer": "r", "operator": "r", "engineer": "r"}
+          },
+          {
+            "node_id": "PLC.Tank.PumpSpeed",
+            "browse_name": "PumpSpeed",
+            "display_name": "Pump Speed",
+            "datatype": "REAL",
+            "initial_value": 0.0,
+            "description": "Pump speed setpoint % (0-100)",
+            "index": 3,
+            "permissions": {"viewer": "rw", "operator": "rw", "engineer": "rw"}
+          },
+          {
+            "node_id": "PLC.Tank.ValvePosition",
+            "browse_name": "ValvePosition",
+            "display_name": "Valve Position",
+            "datatype": "REAL",
+            "initial_value": 0.0,
+            "description": "Valve position setpoint % (0-100)",
+            "index": 5,
+            "permissions": {"viewer": "rw", "operator": "rw", "engineer": "rw"}
+          }
+        ],
+        "structures": [],
+        "arrays": []
+      }
+    }
+  }
+]
diff --git a/demos/openplc_tank/openplc/tank_demo.st b/demos/openplc_tank/openplc/tank_demo.st
new file mode 100644
index 0000000..fb1d11b
--- /dev/null
+++ b/demos/openplc_tank/openplc/tank_demo.st
@@ -0,0 +1,80 @@
+PROGRAM TankSimulation
+  VAR
+    TankLevel       AT %MD0  : REAL := 500.0;
+    TankTemperature AT %MD1  : REAL := 25.0;
+    TankPressure    AT %MD2  : REAL := 1.0;
+    PumpSpeed       AT %MD3  : REAL := 0.0;
+    PumpRunning     AT %MX16.0 : BOOL := FALSE;
+    ValvePosition   AT %MD5  : REAL := 0.0;
+    ValveOpen       AT %MX24.0 : BOOL := FALSE;
+    HighTempAlarm   AT %MX24.1 : BOOL := FALSE;
+    LowLevelAlarm   AT %MX24.2 : BOOL := FALSE;
+    OverpressAlarm  AT %MX24.3 : BOOL := FALSE;
+  END_VAR
+  VAR
+    flow_in  : REAL;
+    flow_out : REAL;
+    heat_rate : REAL;
+  END_VAR
+
+  PumpRunning := PumpSpeed > 0.5;
+
+  IF PumpRunning THEN
+    flow_in := PumpSpeed * 0.5;
+  ELSE
+    flow_in := 0.0;
+  END_IF;
+
+  ValveOpen := ValvePosition > 0.5;
+
+  IF ValveOpen THEN
+    flow_out := ValvePosition * 0.3 * TankLevel / 1000.0;
+  ELSE
+    flow_out := 0.0;
+  END_IF;
+
+  TankLevel := TankLevel + (flow_in - flow_out) * 0.1;
+
+  IF TankLevel > 1000.0 THEN
+    TankLevel := 1000.0;
+  ELSIF TankLevel < 0.0 THEN
+    TankLevel := 0.0;
+  END_IF;
+
+  heat_rate := 0.05;
+  IF flow_in > 0.0 THEN
+    heat_rate := heat_rate - flow_in * 0.002;
+  END_IF;
+  IF flow_out > 0.0 THEN
+    heat_rate := heat_rate - flow_out * 0.001;
+  END_IF;
+
+  TankTemperature := TankTemperature + heat_rate * 0.1;
+
+  IF TankTemperature > 120.0 THEN
+    TankTemperature := 120.0;
+  ELSIF TankTemperature < 0.0 THEN
+    TankTemperature := 0.0;
+  END_IF;
+
+  TankPressure := 1.0 + TankLevel / 1000.0 * 2.0 + TankTemperature / 100.0 * 3.0;
+
+  IF TankPressure > 10.0 THEN
+    TankPressure := 10.0;
+  ELSIF TankPressure < 0.0 THEN
+    TankPressure := 0.0;
+  END_IF;
+
+  HighTempAlarm  := TankTemperature > 80.0;
+  LowLevelAlarm  := TankLevel < 100.0;
+  OverpressAlarm := TankPressure > 5.0;
+
+END_PROGRAM
+
+
+CONFIGURATION Config0
+  RESOURCE Res0 ON PLC
+    TASK MainTask(INTERVAL := T#100ms, PRIORITY := 0);
+    PROGRAM Inst0 WITH MainTask : TankSimulation;
+  END_RESOURCE
+END_CONFIGURATION
diff --git a/demos/openplc_tank/scripts/inject-fault.sh b/demos/openplc_tank/scripts/inject-fault.sh
new file mode 100755
index 0000000..34287b0
--- /dev/null
+++ b/demos/openplc_tank/scripts/inject-fault.sh
@@ -0,0 +1,81 @@
+#!/usr/bin/env bash
+# Inject faults into the OpenPLC Tank Demo
+# Writes values directly to PLC via the x-plc-operations endpoint
+set -eu
+
+GATEWAY_URL="${GATEWAY_URL:-http://localhost:8080}"
+API_BASE="${GATEWAY_URL}/api/v1"
+
+FAULT_TYPE="${1:-high_temp}"
+
+usage() {
+  echo "Usage: $0 [FAULT_TYPE]"
+  echo ""
+  echo "Fault types:"
+  echo "  high_temp     - Set temperature to 95C (triggers PLC_HIGH_TEMP alarm)"
+  echo "  low_level     - Stop pump + open drain (triggers PLC_LOW_LEVEL alarm)"
+  echo "  overpressure  - High pump speed to increase pressure (triggers PLC_OVERPRESSURE)"
+  echo "  all           - Inject all faults simultaneously"
+  echo ""
+  echo "Default: high_temp"
+}
+
+inject_high_temp() {
+  echo "Injecting HIGH_TEMP fault..."
+  echo "  Setting pump speed to 0% (stop cooling)"
+  curl -s -X POST "${API_BASE}/apps/fill_pump/x-plc-operations/set_pump_speed" \
+    -H "Content-Type: application/json" \
+    -d '{"value": 0.0}' | jq .
+
+  echo "  Temperature will rise above 80C threshold..."
+  echo "  Watch: curl ${API_BASE}/apps/tank_process/x-plc-data/tank_temperature"
+  echo "  Fault: curl ${API_BASE}/apps/tank_process/faults"
+}
+
+inject_low_level() {
+  echo "Injecting LOW_LEVEL fault..."
+  echo "  Stopping pump and opening drain valve to 100%"
+  curl -s -X POST "${API_BASE}/apps/fill_pump/x-plc-operations/set_pump_speed" \
+    -H "Content-Type: application/json" \
+    -d '{"value": 0.0}' | jq .
+
+  curl -s -X POST "${API_BASE}/apps/drain_valve/x-plc-operations/set_valve_position" \
+    -H "Content-Type: application/json" \
+    -d '{"value": 100.0}' | jq .
+
+  echo "  Tank level will drop below 100mm threshold..."
+  echo "  Watch: curl ${API_BASE}/apps/tank_process/x-plc-data/tank_level"
+}
+
+inject_overpressure() {
+  echo "Injecting OVERPRESSURE fault..."
+  echo "  Setting pump to 100% and closing drain valve"
+  curl -s -X POST "${API_BASE}/apps/fill_pump/x-plc-operations/set_pump_speed" \
+    -H "Content-Type: application/json" \
+    -d '{"value": 100.0}' | jq .
+
+  curl -s -X POST "${API_BASE}/apps/drain_valve/x-plc-operations/set_valve_position" \
+    -H "Content-Type: application/json" \
+    -d '{"value": 0.0}' | jq .
+
+  echo "  Pressure will rise above 5 bar threshold..."
+  echo "  Watch: curl ${API_BASE}/apps/tank_process/x-plc-data/tank_pressure"
+}
+
+case "$FAULT_TYPE" in
+  high_temp)     inject_high_temp ;;
+  low_level)     inject_low_level ;;
+  overpressure)  inject_overpressure ;;
+  all)
+    inject_high_temp
+    echo ""
+    inject_low_level
+    echo ""
+    inject_overpressure
+    ;;
+  -h|--help)     usage ;;
+  *)             echo "Unknown fault type: $FAULT_TYPE"; usage; exit 1 ;;
+esac
+
+echo ""
+echo "Check faults: curl ${API_BASE}/faults | jq ."
diff --git a/demos/openplc_tank/scripts/restore-normal.sh b/demos/openplc_tank/scripts/restore-normal.sh
new file mode 100755
index 0000000..1c7c16b
--- /dev/null
+++ b/demos/openplc_tank/scripts/restore-normal.sh
@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+# Restore normal operation of the OpenPLC Tank Demo
+# Sets pump and valve to safe operating values
+set -eu
+
+GATEWAY_URL="${GATEWAY_URL:-http://localhost:8080}"
+API_BASE="${GATEWAY_URL}/api/v1"
+
+echo "=== Restoring Normal Operation ==="
+
+echo "Setting pump speed to 50%..."
+curl -s -X POST "${API_BASE}/apps/fill_pump/x-plc-operations/set_pump_speed" \
+  -H "Content-Type: application/json" \
+  -d '{"value": 50.0}' > /dev/null
+
+echo "Setting valve position to 30%..."
+curl -s -X POST "${API_BASE}/apps/drain_valve/x-plc-operations/set_valve_position" \
+  -H "Content-Type: application/json" \
+  -d '{"value": 30.0}' > /dev/null
+
+echo ""
+echo "Normal operating parameters set."
+echo "  Pump: 50% (filling)"
+echo "  Valve: 30% (partial drain)"
+echo ""
+echo "Tank will stabilize to normal levels."
+echo "Alarms will clear automatically when values return to safe range."
+echo ""
+
+# Clear any existing faults from fault manager
+echo "Clearing existing faults..."
+for code in PLC_HIGH_TEMP PLC_LOW_LEVEL PLC_OVERPRESSURE; do
+  curl -s -X DELETE "${API_BASE}/apps/tank_process/faults/${code}" > /dev/null 2>&1 || true
+done
+
+echo "Done. Check status:"
+echo "  curl ${API_BASE}/apps/tank_process/x-plc-data | jq ."
+echo "  curl ${API_BASE}/faults | jq ."
diff --git a/demos/openplc_tank/scripts/run-demo.sh b/demos/openplc_tank/scripts/run-demo.sh
new file mode 100755
index 0000000..4536604
--- /dev/null
+++ b/demos/openplc_tank/scripts/run-demo.sh
@@ -0,0 +1,89 @@
+#!/usr/bin/env bash
+# Run the OpenPLC Tank Demo
+set -eu
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+DEMO_DIR="$(dirname "$SCRIPT_DIR")"
+cd "$DEMO_DIR"
+
+# Defaults
+DETACH_MODE=true
+UPDATE=false
+NO_CACHE=false
+
+usage() {
+  echo "Usage: $0 [OPTIONS]"
+  echo ""
+  echo "Options:"
+  echo "  --attached    Run in foreground (default: detached)"
+  echo "  --update      Pull latest images before starting"
+  echo "  --no-cache    Build without Docker cache"
+  echo "  -h, --help    Show this help"
+}
+
+while [[ $# -gt 0 ]]; do
+  case $1 in
+    --attached) DETACH_MODE=false; shift ;;
+    --update)   UPDATE=true; shift ;;
+    --no-cache) NO_CACHE=true; shift ;;
+    -h|--help)  usage; exit 0 ;;
+    *)          echo "Unknown option: $1"; usage; exit 1 ;;
+  esac
+done
+
+# Detect compose command
+if docker compose version &> /dev/null; then
+  COMPOSE_CMD="docker compose"
+else
+  COMPOSE_CMD="docker-compose"
+fi
+
+echo "=== OpenPLC Tank Demo ==="
+echo "Components:"
+echo "  - OpenPLC v4 Runtime (OPC-UA :4840)"
+echo "  - ros2_medkit Gateway + OPC-UA Plugin (REST :8080)"
+echo "  - SOVD Web UI (:3000)"
+echo ""
+
+# Optional: pull latest web UI
+if [[ "$UPDATE" == "true" ]]; then
+  echo "Pulling latest images..."
+  $COMPOSE_CMD pull sovd-web-ui
+fi
+
+# Build
+BUILD_ARGS=""
+if [[ "$NO_CACHE" == "true" ]]; then
+  BUILD_ARGS="--no-cache"
+fi
+
+echo "Building containers..."
+$COMPOSE_CMD build $BUILD_ARGS || {
+  echo "Build failed!"
+  exit 1
+}
+
+# Run
+DETACH_FLAG=""
+if [[ "$DETACH_MODE" == "true" ]]; then
+  DETACH_FLAG="-d"
+fi
+
+echo "Starting demo..."
+$COMPOSE_CMD up $DETACH_FLAG
+
+if [[ "$DETACH_MODE" == "true" ]]; then
+  echo ""
+  echo "Demo started in background."
+  echo ""
+  echo "Next steps:"
+  echo "  - Web UI:     http://localhost:3000"
+  echo "  - REST API:   http://localhost:8080/api/v1"
+  echo "  - OPC-UA:     opc.tcp://localhost:4840"
+  echo ""
+  echo "  - Check:      curl http://localhost:8080/api/v1/health"
+  echo "  - PLC data:   curl http://localhost:8080/api/v1/apps/tank_process/x-plc-data"
+  echo "  - Inject:     ./scripts/inject-fault.sh"
+  echo "  - Restore:    ./scripts/restore-normal.sh"
+  echo "  - Stop:       ./scripts/stop-demo.sh"
+fi
diff --git a/demos/openplc_tank/scripts/run_integration_tests.sh b/demos/openplc_tank/scripts/run_integration_tests.sh
new file mode 100755
index 0000000..31443f3
--- /dev/null
+++ b/demos/openplc_tank/scripts/run_integration_tests.sh
@@ -0,0 +1,378 @@
+#!/usr/bin/env bash
+# Integration Tests for OpenPLC Tank Demo
+# Tests: entity discovery, live data, control, fault lifecycle, resilience, errors
+set -euo pipefail
+
+GATEWAY_URL="${GATEWAY_URL:-http://localhost:8080}"
+API="${GATEWAY_URL}/api/v1"
+CURL_OPTS="--max-time 10 -sf"
+PASSED=0
+FAILED=0
+TOTAL=0
+
+# Colors
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m'
+
+cleanup() {
+  echo ""
+  echo "==============================="
+  echo -e "Results: ${GREEN}${PASSED} passed${NC} / ${RED}${FAILED} failed${NC} / ${TOTAL} total"
+  echo "==============================="
+  if [[ $FAILED -gt 0 ]]; then
+    exit 1
+  fi
+}
+trap cleanup EXIT
+
+# --- Helpers ---
+
+assert_response() {
+  local description="$1"
+  local method="$2"
+  local url="$3"
+  local expected_status="$4"
+  local body="${5:-}"
+  local jq_filter="${6:-}"
+  local expected_value="${7:-}"
+
+  TOTAL=$((TOTAL + 1))
+
+  local curl_args=("--max-time" "10" "-s" "-o" "/tmp/test_body.json" "-w" "%{http_code}")
+
+  if [[ "$method" == "POST" ]]; then
+    curl_args+=("-X" "POST" "-H" "Content-Type: application/json")
+    if [[ -n "$body" ]]; then
+      curl_args+=("-d" "$body")
+    fi
+  elif [[ "$method" == "DELETE" ]]; then
+    curl_args+=("-X" "DELETE")
+  fi
+
+  curl_args+=("$url")
+
+  local status
+  status=$(curl "${curl_args[@]}" 2>/dev/null) || status="000"
+
+  if [[ "$status" != "$expected_status" ]]; then
+    FAILED=$((FAILED + 1))
+    echo -e "${RED}FAIL${NC} $description"
+    echo "       Expected HTTP $expected_status, got $status"
+    echo "       URL: $method $url"
+    if [[ -f /tmp/test_body.json ]]; then
+      echo "       Body: $(head -c 200 /tmp/test_body.json)"
+    fi
+    return 1
+  fi
+
+  if [[ -n "$jq_filter" && -n "$expected_value" ]]; then
+    local actual
+    actual=$(jq -r "$jq_filter" /tmp/test_body.json 2>/dev/null) || actual="<jq error>"
+
+    if [[ "$actual" != "$expected_value" ]]; then
+      FAILED=$((FAILED + 1))
+      echo -e "${RED}FAIL${NC} $description"
+      echo "       jq '$jq_filter' = '$actual', expected '$expected_value'"
+      return 1
+    fi
+  fi
+
+  PASSED=$((PASSED + 1))
+  echo -e "${GREEN}PASS${NC} $description"
+  return 0
+}
+
+assert_contains() {
+  local description="$1"
+  local url="$2"
+  local jq_filter="$3"
+  local expected_value="$4"
+
+  TOTAL=$((TOTAL + 1))
+
+  local body
+  body=$(curl $CURL_OPTS "$url" 2>/dev/null) || body=""
+
+  local result
+  result=$(echo "$body" | jq -r "$jq_filter" 2>/dev/null) || result=""
+
+  if echo "$result" | grep -q "$expected_value"; then
+    PASSED=$((PASSED + 1))
+    echo -e "${GREEN}PASS${NC} $description"
+    return 0
+  else
+    FAILED=$((FAILED + 1))
+    echo -e "${RED}FAIL${NC} $description"
+    echo "       '$expected_value' not found in jq output of '$jq_filter'"
+    return 1
+  fi
+}
+
+wait_for_gateway() {
+  echo "Waiting for gateway..."
+  for i in $(seq 1 30); do
+    if curl -sf "${API}/health" > /dev/null 2>&1; then
+      echo "Gateway is up!"
+      return 0
+    fi
+    sleep 1
+  done
+  echo "Gateway did not start within 30s"
+  exit 1
+}
+
+# --- Start ---
+
+echo "========================================"
+echo "OpenPLC Tank Demo - Integration Tests"
+echo "Gateway: $GATEWAY_URL"
+echo "========================================"
+echo ""
+
+wait_for_gateway
+
+# =============================================================================
+# 1. Entity Discovery (SOVD Tree)
+# =============================================================================
+echo ""
+echo -e "${YELLOW}--- 1. Entity Discovery ---${NC}"
+
+assert_contains "Area plc_systems exists" \
+  "${API}/areas" '.items[].id' "plc_systems"
+
+assert_contains "Component openplc_runtime exists" \
+  "${API}/components" '.items[].id' "openplc_runtime"
+
+assert_contains "App tank_process exists" \
+  "${API}/apps" '.items[].id' "tank_process"
+
+assert_contains "App fill_pump exists" \
+  "${API}/apps" '.items[].id' "fill_pump"
+
+assert_contains "App drain_valve exists" \
+  "${API}/apps" '.items[].id' "drain_valve"
+
+assert_response "tank_process detail returns external=true" \
+  "GET" "${API}/apps/tank_process" "200" "" '.external' "true"
+
+assert_response "openplc_runtime is in plc_systems area" \
+  "GET" "${API}/components/openplc_runtime" "200" "" '."x-medkit".area' "plc_systems"
+
+# =============================================================================
+# 2. Live Data (sensor readings)
+# =============================================================================
+echo ""
+echo -e "${YELLOW}--- 2. Live Data ---${NC}"
+
+assert_response "tank_process x-plc-data returns 200" \
+  "GET" "${API}/apps/tank_process/x-plc-data" "200"
+
+assert_contains "tank_process has tank_level data" \
+  "${API}/apps/tank_process/x-plc-data" '.items[].name' "tank_level"
+
+assert_contains "tank_process has tank_temperature data" \
+  "${API}/apps/tank_process/x-plc-data" '.items[].name' "tank_temperature"
+
+assert_contains "tank_process has tank_pressure data" \
+  "${API}/apps/tank_process/x-plc-data" '.items[].name' "tank_pressure"
+
+assert_response "fill_pump x-plc-data returns 200" \
+  "GET" "${API}/apps/fill_pump/x-plc-data" "200"
+
+assert_contains "fill_pump has pump_speed data" \
+  "${API}/apps/fill_pump/x-plc-data" '.items[].name' "pump_speed"
+
+assert_contains "fill_pump has pump_running data" \
+  "${API}/apps/fill_pump/x-plc-data" '.items[].name' "pump_running"
+
+assert_response "drain_valve x-plc-data returns 200" \
+  "GET" "${API}/apps/drain_valve/x-plc-data" "200"
+
+assert_contains "drain_valve has valve_position data" \
+  "${API}/apps/drain_valve/x-plc-data" '.items[].name' "valve_position"
+
+assert_response "Single node query works" \
+  "GET" "${API}/apps/tank_process/x-plc-data/tank_level" "200"
+
+# Verify values are numeric (not null)
+TOTAL=$((TOTAL + 1))
+LEVEL=$(curl $CURL_OPTS "${API}/apps/tank_process/x-plc-data/tank_level" 2>/dev/null | jq '.value' 2>/dev/null)
+if [[ "$LEVEL" != "null" && -n "$LEVEL" ]]; then
+  PASSED=$((PASSED + 1))
+  echo -e "${GREEN}PASS${NC} tank_level has numeric value: $LEVEL"
+else
+  FAILED=$((FAILED + 1))
+  echo -e "${RED}FAIL${NC} tank_level value is null or missing"
+fi
+
+# =============================================================================
+# 3. Control (write setpoints)
+# =============================================================================
+echo ""
+echo -e "${YELLOW}--- 3. Control Operations ---${NC}"
+
+assert_response "Set pump speed to 75%" \
+  "POST" "${API}/apps/fill_pump/x-plc-operations/set_pump_speed" "200" \
+  '{"value": 75.0}'
+
+sleep 1  # Wait for PLC cycle
+
+# Verify pump speed was written
+TOTAL=$((TOTAL + 1))
+PUMP_SPEED=$(curl $CURL_OPTS "${API}/apps/fill_pump/x-plc-data/pump_speed" 2>/dev/null | jq '.value' 2>/dev/null)
+if [[ -n "$PUMP_SPEED" ]] && (( $(echo "$PUMP_SPEED > 70 && $PUMP_SPEED < 80" | bc -l 2>/dev/null || echo 0) )); then
+  PASSED=$((PASSED + 1))
+  echo -e "${GREEN}PASS${NC} pump_speed reads back ~75.0 (got $PUMP_SPEED)"
+else
+  FAILED=$((FAILED + 1))
+  echo -e "${RED}FAIL${NC} pump_speed readback: expected ~75.0, got $PUMP_SPEED"
+fi
+
+assert_response "Set valve position to 50%" \
+  "POST" "${API}/apps/drain_valve/x-plc-operations/set_valve_position" "200" \
+  '{"value": 50.0}'
+
+sleep 1
+
+# Verify valve position
+TOTAL=$((TOTAL + 1))
+VALVE_POS=$(curl $CURL_OPTS "${API}/apps/drain_valve/x-plc-data/valve_position" 2>/dev/null | jq '.value' 2>/dev/null)
+if [[ -n "$VALVE_POS" ]] && (( $(echo "$VALVE_POS > 45 && $VALVE_POS < 55" | bc -l 2>/dev/null || echo 0) )); then
+  PASSED=$((PASSED + 1))
+  echo -e "${GREEN}PASS${NC} valve_position reads back ~50.0 (got $VALVE_POS)"
+else
+  FAILED=$((FAILED + 1))
+  echo -e "${RED}FAIL${NC} valve_position readback: expected ~50.0, got $VALVE_POS"
+fi
+
+# =============================================================================
+# 4. Fault Lifecycle (alarm injection + SOVD faults)
+# =============================================================================
+echo ""
+echo -e "${YELLOW}--- 4. Fault Lifecycle ---${NC}"
+
+# First, restore normal state
+curl -s -X POST "${API}/apps/fill_pump/x-plc-operations/set_pump_speed" \
+  -H "Content-Type: application/json" -d '{"value": 0.0}' > /dev/null 2>&1 || true
+
+echo "Waiting for temperature to rise above 80C (alarm threshold)..."
+# Stop pump to let temperature rise
+ALARM_DETECTED=0
+for i in $(seq 1 60); do
+  TEMP=$(curl $CURL_OPTS "${API}/apps/tank_process/x-plc-data/tank_temperature" 2>/dev/null | jq '.value' 2>/dev/null || echo "0")
+  if (( $(echo "${TEMP:-0} > 80" | bc -l 2>/dev/null || echo 0) )); then
+    echo "  Temperature reached ${TEMP}C"
+    ALARM_DETECTED=1
+    break
+  fi
+  if (( i % 10 == 0 )); then
+    echo "  Temperature at ${TEMP}C..."
+  fi
+  sleep 2
+done
+
+if [[ $ALARM_DETECTED -eq 1 ]]; then
+  sleep 2  # Wait for poller + fault report
+
+  assert_contains "PLC_HIGH_TEMP fault reported" \
+    "${API}/apps/tank_process/faults" '.faults[].fault_code' "PLC_HIGH_TEMP"
+
+  assert_contains "PLC_HIGH_TEMP in global fault list" \
+    "${API}/faults" '.faults[].fault_code' "PLC_HIGH_TEMP"
+
+  # Clear alarm by restoring pump (cooling)
+  echo "Clearing alarm - restoring pump to cool tank..."
+  curl -s -X POST "${API}/apps/fill_pump/x-plc-operations/set_pump_speed" \
+    -H "Content-Type: application/json" -d '{"value": 80.0}' > /dev/null
+
+  ALARM_CLEARED=0
+  for i in $(seq 1 60); do
+    TEMP=$(curl $CURL_OPTS "${API}/apps/tank_process/x-plc-data/tank_temperature" 2>/dev/null | jq '.value' 2>/dev/null || echo "100")
+    if (( $(echo "${TEMP:-100} < 80" | bc -l 2>/dev/null || echo 0) )); then
+      echo "  Temperature dropped to ${TEMP}C"
+      ALARM_CLEARED=1
+      break
+    fi
+    if (( i % 10 == 0 )); then
+      echo "  Temperature at ${TEMP}C..."
+    fi
+    sleep 2
+  done
+
+  if [[ $ALARM_CLEARED -eq 1 ]]; then
+    sleep 2
+    TOTAL=$((TOTAL + 1))
+    FAULTS=$(curl $CURL_OPTS "${API}/apps/tank_process/faults" 2>/dev/null | jq '[.faults[] | select(.fault_code == "PLC_HIGH_TEMP" and .status == "active")] | length' 2>/dev/null || echo "1")
+    if [[ "$FAULTS" == "0" ]]; then
+      PASSED=$((PASSED + 1))
+      echo -e "${GREEN}PASS${NC} PLC_HIGH_TEMP fault cleared after temperature drop"
+    else
+      FAILED=$((FAILED + 1))
+      echo -e "${RED}FAIL${NC} PLC_HIGH_TEMP fault still active after temperature drop"
+    fi
+  else
+    TOTAL=$((TOTAL + 1))
+    FAILED=$((FAILED + 1))
+    echo -e "${RED}FAIL${NC} Temperature did not drop below 80C within timeout"
+  fi
+else
+  echo -e "${YELLOW}SKIP${NC} Fault lifecycle tests - temperature did not reach threshold"
+  echo "  (This may happen if PLC simulation rate differs from expected)"
+fi
+
+# Restore normal operation for remaining tests
+curl -s -X POST "${API}/apps/fill_pump/x-plc-operations/set_pump_speed" \
+  -H "Content-Type: application/json" -d '{"value": 50.0}' > /dev/null 2>&1 || true
+curl -s -X POST "${API}/apps/drain_valve/x-plc-operations/set_valve_position" \
+  -H "Content-Type: application/json" -d '{"value": 30.0}' > /dev/null 2>&1 || true
+
+# =============================================================================
+# 5. Connection Status
+# =============================================================================
+echo ""
+echo -e "${YELLOW}--- 5. Connection Status ---${NC}"
+
+assert_response "x-plc-status endpoint returns 200" \
+  "GET" "${API}/components/openplc_runtime/x-plc-status" "200"
+
+assert_response "x-plc-status shows connected=true" \
+  "GET" "${API}/components/openplc_runtime/x-plc-status" "200" "" '.connected' "true"
+
+TOTAL=$((TOTAL + 1))
+POLL_COUNT=$(curl $CURL_OPTS "${API}/components/openplc_runtime/x-plc-status" 2>/dev/null | jq '.poll_count' 2>/dev/null || echo "0")
+if [[ -n "$POLL_COUNT" ]] && (( POLL_COUNT > 0 )); then
+  PASSED=$((PASSED + 1))
+  echo -e "${GREEN}PASS${NC} poll_count > 0 (got $POLL_COUNT)"
+else
+  FAILED=$((FAILED + 1))
+  echo -e "${RED}FAIL${NC} poll_count should be > 0, got $POLL_COUNT"
+fi
+
+# =============================================================================
+# 6. Error Responses (SOVD conformance)
+# =============================================================================
+echo ""
+echo -e "${YELLOW}--- 6. Error Responses ---${NC}"
+
+assert_response "404 for nonexistent app x-plc-data" \
+  "GET" "${API}/apps/nonexistent/x-plc-data" "404"
+
+assert_response "404 for nonexistent operation" \
+  "POST" "${API}/apps/fill_pump/x-plc-operations/nonexistent" "404" \
+  '{"value": 42}'
+
+assert_response "400 for invalid JSON body" \
+  "POST" "${API}/apps/fill_pump/x-plc-operations/set_pump_speed" "400" \
+  'not json'
+
+assert_response "400 for missing value field" \
+  "POST" "${API}/apps/fill_pump/x-plc-operations/set_pump_speed" "400" \
+  '{"wrong": 42}'
+
+assert_response "400 for read-only data point write" \
+  "POST" "${API}/apps/fill_pump/x-plc-operations/set_pump_running" "404"
+
+assert_response "404 for nonexistent single data point" \
+  "GET" "${API}/apps/tank_process/x-plc-data/nonexistent" "404"
diff --git a/demos/openplc_tank/scripts/stop-demo.sh b/demos/openplc_tank/scripts/stop-demo.sh
new file mode 100755
index 0000000..3fba002
--- /dev/null
+++ b/demos/openplc_tank/scripts/stop-demo.sh
@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+# Stop the OpenPLC Tank Demo
+set -eu
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+DEMO_DIR="$(dirname "$SCRIPT_DIR")"
+cd "$DEMO_DIR"
+
+VOLUMES=false
+
+while [[ $# -gt 0 ]]; do
+  case $1 in
+    --volumes|-v) VOLUMES=true; shift ;;
+    *)            shift ;;
+  esac
+done
+
+if docker compose version &> /dev/null; then
+  COMPOSE_CMD="docker compose"
+else
+  COMPOSE_CMD="docker-compose"
+fi
+
+DOWN_ARGS=""
+if [[ "$VOLUMES" == "true" ]]; then
+  DOWN_ARGS="-v"
+fi
+
+echo "Stopping OpenPLC Tank Demo..."
+$COMPOSE_CMD down $DOWN_ARGS
+echo "Done."