diff --git a/CLAUDE.md b/CLAUDE.md
index 65c3f92..7a65cf0 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -187,11 +187,35 @@ mosquitto_pub -t "systant/hostname/commands" -m '{"command":"restart","params":[
 mosquitto_sub -t "systant/+/responses"
 ```
 
-### Phase 3: Home Assistant Integration
-- Custom MQTT integration following Home Assistant patterns
-- Auto-discovery of systant hosts via MQTT discovery protocol
-- Create entities for metrics (sensors) and commands (buttons/services)
-- Dashboard cards and automation support
+### Phase 3: Home Assistant Integration (Completed)
+- ✅ **MQTT Auto-Discovery**: `server/lib/systant/ha_discovery.ex` - Publishes HA discovery configurations for automatic device registration
+- ✅ **Device Registration**: Creates unified "Systant {hostname}" device in Home Assistant with comprehensive sensor suite
+- ✅ **Sensor Auto-Discovery**: CPU load averages, memory usage, system uptime, temperatures, GPU metrics, disk usage, network stats
+- ✅ **Configuration Integration**: TOML-based enable/disable with `homeassistant.discovery_enabled` setting
+- ✅ **Value Templates**: Proper JSON path extraction for nested metrics data with error handling
+- ✅ **Real-time Updates**: Seamless integration with existing MQTT stats publishing - no additional topics needed
+
+#### Home Assistant Integration Features
+- **Automatic Discovery**: No custom integration required - uses standard MQTT discovery protocol
+- **Device Grouping**: All sensors grouped under single "Systant {hostname}" device for clean organization  
+- **Comprehensive Metrics**: CPU, memory, disk, GPU (NVIDIA/AMD), network, temperature, and system sensors
+- **Configuration Control**: Enable/disable discovery via `systant.toml` configuration
+- **Template Flexibility**: Advanced Jinja2 templates handle optional/missing data gracefully
+- **Topic Structure**: Discovery on `homeassistant/#`, stats remain on `systant/{hostname}/stats`
+
+#### Setup Instructions
+1. **Configure MQTT Discovery**: Set `homeassistant.discovery_enabled = true` in `systant.toml`
+2. **Start Systant**: Discovery messages published automatically on startup (1s after MQTT connection)
+3. **Check Home Assistant**: Device and sensors appear automatically in MQTT integration
+4. **Verify Metrics**: All sensors should show current values within 30 seconds
+
+#### Available Sensors
+- **CPU**: Load averages (1m, 5m, 15m), temperature
+- **Memory**: Usage percentage, used/total in GB
+- **Disk**: Root and home filesystem usage percentages  
+- **GPU**: NVIDIA/AMD utilization, temperature, memory usage
+- **Network**: RX/TX bytes for primary interface
+- **System**: Uptime in hours, kernel version, online status
 
 ### Future Plans
 - Multi-host deployment for comprehensive system monitoring
diff --git a/flake.nix b/flake.nix
index 2f83987..0ac0bc1 100644
--- a/flake.nix
+++ b/flake.nix
@@ -45,6 +45,9 @@
 
             # Database for development
             postgresql
+
+            # Mosquito for MQTT support
+            mosquitto
           ];
 
           shellHook = ''
diff --git a/server/lib/systant/config.ex b/server/lib/systant/config.ex
index dd05322..eee5afd 100644
--- a/server/lib/systant/config.ex
+++ b/server/lib/systant/config.ex
@@ -70,6 +70,10 @@ defmodule Systant.Config do
       "password" => "",
       "qos" => 0
     },
+    "homeassistant" => %{
+      "discovery_enabled" => true,
+      "discovery_prefix" => "homeassistant"
+    },
     "logging" => %{
       "level" => "info",
       "log_config_changes" => true,
diff --git a/server/lib/systant/ha_discovery.ex b/server/lib/systant/ha_discovery.ex
new file mode 100644
index 0000000..32c6733
--- /dev/null
+++ b/server/lib/systant/ha_discovery.ex
@@ -0,0 +1,182 @@
+defmodule Systant.HaDiscovery do
+  @moduledoc """
+  Home Assistant MQTT Discovery integration for Systant.
+  
+  Publishes device and entity discovery configurations to Home Assistant
+  via MQTT following the HA discovery protocol.
+  
+  Discovery topic format: homeassistant/<component>/<node_id>/<object_id>/config
+  """
+
+  require Logger
+
+  @manufacturer "Systant"
+  @model "System Monitor"
+
+  @doc """
+  Publish all discovery configurations for a host
+  """
+  def publish_discovery(client_pid, hostname, config \\ nil) do
+    app_config = config || Systant.Config.load_config()
+    ha_config = Systant.Config.get(app_config, ["homeassistant"]) || %{}
+    
+    if ha_config["discovery_enabled"] != false do
+      discovery_prefix = ha_config["discovery_prefix"] || "homeassistant"
+      device_config = build_device_config(hostname)
+      
+      # Publish device discovery first
+      publish_device_discovery(client_pid, hostname, device_config, discovery_prefix)
+      
+      # Publish sensor discoveries
+      publish_sensor_discoveries(client_pid, hostname, device_config, discovery_prefix)
+      
+      Logger.info("Published Home Assistant discovery for #{hostname}")
+    else
+      Logger.info("Home Assistant discovery disabled in configuration")
+    end
+  end
+
+  @doc """
+  Remove all discovery configurations for a host
+  """
+  def remove_discovery(client_pid, hostname, config \\ nil) do
+    app_config = config || Systant.Config.load_config()
+    ha_config = Systant.Config.get(app_config, ["homeassistant"]) || %{}
+    discovery_prefix = ha_config["discovery_prefix"] || "homeassistant"
+    
+    # Remove by publishing empty payloads to discovery topics
+    sensors = get_sensor_definitions(hostname)
+    
+    Enum.each(sensors, fn {component, object_id, _config} ->
+      topic = "#{discovery_prefix}/#{component}/#{hostname}/#{object_id}/config"
+      Tortoise.publish(client_pid, topic, "", retain: true)
+    end)
+    
+    Logger.info("Removed Home Assistant discovery for #{hostname}")
+  end
+
+  # Private functions
+
+  defp publish_device_discovery(client_pid, hostname, device_config, discovery_prefix) do
+    # Use device-based discovery for multiple components
+    components_config = %{
+      device: device_config,
+      components: build_all_components(hostname, device_config)
+    }
+    
+    topic = "#{discovery_prefix}/device/#{hostname}/config"
+    payload = Jason.encode!(components_config)
+    
+    Tortoise.publish(client_pid, topic, payload, retain: true)
+  end
+
+  defp publish_sensor_discoveries(client_pid, hostname, device_config, discovery_prefix) do
+    sensors = get_sensor_definitions(hostname)
+    
+    Enum.each(sensors, fn {component, object_id, config} ->
+      full_config = Map.merge(config, %{device: device_config})
+      topic = "#{discovery_prefix}/#{component}/#{hostname}/#{object_id}/config"
+      payload = Jason.encode!(full_config)
+      
+      Tortoise.publish(client_pid, topic, payload, retain: true)
+    end)
+  end
+
+  defp build_device_config(hostname) do
+    %{
+      identifiers: ["systant_#{hostname}"],
+      name: "Systant #{hostname}",
+      manufacturer: @manufacturer,
+      model: @model,
+      sw_version: Application.spec(:systant, :vsn) |> to_string()
+    }
+  end
+
+  defp build_all_components(hostname, device_config) do
+    get_sensor_definitions(hostname)
+    |> Enum.map(fn {_component, object_id, config} ->
+      Map.merge(config, %{device: device_config})
+      |> Map.put(:object_id, object_id)
+    end)
+  end
+
+  defp get_sensor_definitions(hostname) do
+    base_topic = "systant/#{hostname}/stats"
+    
+    [
+      # CPU Sensors
+      {"sensor", "cpu_load_1m", build_sensor_config("CPU Load 1m", "#{base_topic}", "cpu.avg1", "load", "mdi:speedometer")},
+      {"sensor", "cpu_load_5m", build_sensor_config("CPU Load 5m", "#{base_topic}", "cpu.avg5", "load", "mdi:speedometer")},
+      {"sensor", "cpu_load_15m", build_sensor_config("CPU Load 15m", "#{base_topic}", "cpu.avg15", "load", "mdi:speedometer")},
+      
+      # Memory Sensors
+      {"sensor", "memory_used_percent", build_sensor_config("Memory Used", "#{base_topic}", "memory.used_percent", "%", "mdi:memory")},
+      {"sensor", "memory_used_gb", build_sensor_config("Memory Used GB", "#{base_topic}", "memory.used_kb", "GB", "mdi:memory", "{{ (value_json.memory.used_kb | float / 1024 / 1024) | round(2) }}")},
+      {"sensor", "memory_total_gb", build_sensor_config("Memory Total GB", "#{base_topic}", "memory.total_kb", "GB", "mdi:memory", "{{ (value_json.memory.total_kb | float / 1024 / 1024) | round(2) }}")},
+      
+      # System Sensors
+      {"sensor", "uptime_hours", build_sensor_config("Uptime", "#{base_topic}", "system.uptime_seconds", "h", "mdi:clock-outline", "{{ (value_json.system.uptime_seconds | float / 3600) | round(1) }}")},
+      {"sensor", "kernel_version", build_sensor_config("Kernel Version", "#{base_topic}", "system.kernel_version", nil, "mdi:linux")},
+      
+      # Temperature Sensors
+      {"sensor", "cpu_temperature", build_sensor_config("CPU Temperature", "#{base_topic}", "temperature.cpu", "°C", "mdi:thermometer")},
+      
+      # GPU Sensors - NVIDIA
+      {"sensor", "gpu_nvidia_utilization", build_sensor_config("NVIDIA GPU Utilization", "#{base_topic}", "gpu.nvidia[0].utilization_percent", "%", "mdi:expansion-card", "{{ value_json.gpu.nvidia[0].utilization_percent if value_json.gpu.nvidia and value_json.gpu.nvidia|length > 0 else 0 }}")},
+      {"sensor", "gpu_nvidia_temperature", build_sensor_config("NVIDIA GPU Temperature", "#{base_topic}", "gpu.nvidia[0].temperature_c", "°C", "mdi:thermometer", "{{ value_json.gpu.nvidia[0].temperature_c if value_json.gpu.nvidia and value_json.gpu.nvidia|length > 0 else none }}")},
+      {"sensor", "gpu_nvidia_memory", build_sensor_config("NVIDIA GPU Memory", "#{base_topic}", "gpu.nvidia[0].memory_used_mb", "MB", "mdi:memory", "{{ value_json.gpu.nvidia[0].memory_used_mb if value_json.gpu.nvidia and value_json.gpu.nvidia|length > 0 else none }}")},
+      
+      # GPU Sensors - AMD
+      {"sensor", "gpu_amd_utilization", build_sensor_config("AMD GPU Utilization", "#{base_topic}", "gpu.amd[0].utilization_percent", "%", "mdi:expansion-card", "{{ value_json.gpu.amd[0].utilization_percent if value_json.gpu.amd and value_json.gpu.amd|length > 0 else 0 }}")},
+      {"sensor", "gpu_amd_temperature", build_sensor_config("AMD GPU Temperature", "#{base_topic}", "gpu.amd[0].temperature_c", "°C", "mdi:thermometer", "{{ value_json.gpu.amd[0].temperature_c if value_json.gpu.amd and value_json.gpu.amd|length > 0 else none }}")},
+      
+      # Disk Sensors - Main filesystem usage
+      {"sensor", "disk_root_usage", build_sensor_config("Root Disk Usage", "#{base_topic}", "disk.disks", "%", "mdi:harddisk", "{{ (value_json.disk.disks | selectattr('mounted_on', 'equalto', '/') | list | first).use_percent if value_json.disk.disks else 0 }}")},
+      {"sensor", "disk_home_usage", build_sensor_config("Home Disk Usage", "#{base_topic}", "disk.disks", "%", "mdi:harddisk", "{{ (value_json.disk.disks | selectattr('mounted_on', 'equalto', '/home') | list | first).use_percent if (value_json.disk.disks | selectattr('mounted_on', 'equalto', '/home') | list) else 0 }}")},
+      
+      # Network Sensors - Primary interface
+      {"sensor", "network_rx_bytes", build_sensor_config("Network RX Bytes", "#{base_topic}", "network", "bytes", "mdi:download-network", "{{ value_json.network[0].rx_bytes if value_json.network and value_json.network|length > 0 else 0 }}")},
+      {"sensor", "network_tx_bytes", build_sensor_config("Network TX Bytes", "#{base_topic}", "network", "bytes", "mdi:upload-network", "{{ value_json.network[0].tx_bytes if value_json.network and value_json.network|length > 0 else 0 }}")},
+      
+      # Binary Sensors for status
+      {"binary_sensor", "system_online", build_binary_sensor_config("System Online", "#{base_topic}", "mdi:server", "connectivity")}
+    ]
+  end
+
+  defp build_sensor_config(name, state_topic, value_template_path, unit, icon, custom_template \\ nil) do
+    base_config = %{
+      name: name,
+      state_topic: state_topic,
+      value_template: custom_template || "{{ value_json.#{value_template_path} }}",
+      icon: icon,
+      unique_id: "systant_#{String.replace(state_topic, "/", "_")}_#{String.replace(value_template_path, ".", "_")}",
+      origin: %{
+        name: "Systant",
+        sw_version: Application.spec(:systant, :vsn) |> to_string(),
+        support_url: "https://github.com/user/systant"
+      }
+    }
+    
+    if unit do
+      Map.put(base_config, :unit_of_measurement, unit)
+    else
+      base_config
+    end
+  end
+
+  defp build_binary_sensor_config(name, state_topic, icon, device_class) do
+    %{
+      name: name,
+      state_topic: state_topic,
+      value_template: "{{ 'ON' if value_json.timestamp else 'OFF' }}",
+      device_class: device_class,
+      icon: icon,
+      unique_id: "systant_#{String.replace(state_topic, "/", "_")}_online",
+      origin: %{
+        name: "Systant",
+        sw_version: Application.spec(:systant, :vsn) |> to_string(),
+        support_url: "https://github.com/user/systant"
+      }
+    }
+  end
+end
\ No newline at end of file
diff --git a/server/lib/systant/mqtt_client.ex b/server/lib/systant/mqtt_client.ex
index e55dcaa..ad35963 100644
--- a/server/lib/systant/mqtt_client.ex
+++ b/server/lib/systant/mqtt_client.ex
@@ -41,6 +41,10 @@ defmodule Systant.MqttClient do
         Process.send_after(self(), :publish_startup_stats, startup_delay)
         Logger.info("Will publish initial stats in #{startup_delay}ms")
         
+        # Publish Home Assistant discovery after MQTT connection
+        Process.send_after(self(), :publish_ha_discovery, 1000)
+        Logger.info("Will publish HA discovery in 1000ms")
+        
         schedule_stats_publish(mqtt_config.publish_interval)
         {:ok, state_config}
         
@@ -50,6 +54,14 @@ defmodule Systant.MqttClient do
     end
   end
 
+  def handle_info(:publish_ha_discovery, state) do
+    Logger.info("Publishing Home Assistant discovery configuration")
+    # Get hostname from system metrics (reuse existing logic)
+    stats = Systant.SystemMetrics.collect_metrics(state.app_config)
+    Systant.HaDiscovery.publish_discovery(state.mqtt_config.client_id, stats.hostname, state.app_config)
+    {:noreply, state}
+  end
+
   def handle_info(:publish_startup_stats, state) do
     Logger.info("Publishing initial system metrics")
     publish_stats(state.app_config, state.mqtt_config)
diff --git a/server/systant.toml b/server/systant.toml
index 67400b9..23f6ff6 100644
--- a/server/systant.toml
+++ b/server/systant.toml
@@ -88,6 +88,11 @@ password = ""
 # QoS level (0, 1, or 2)
 qos = 0
 
+# Home Assistant MQTT Discovery Configuration
+[homeassistant]
+discovery_enabled = true              # Enable/disable HA auto-discovery
+discovery_prefix = "homeassistant"    # HA discovery topic prefix
+
 [logging]
 # Log level: "debug", "info", "warning", "error"
 level = "info"
diff --git a/server/systant.toml.example b/server/systant.toml.example
new file mode 100644
index 0000000..5e59634
--- /dev/null
+++ b/server/systant.toml.example
@@ -0,0 +1,108 @@
+# Systant Configuration Example
+# Copy to systant.toml and customize for your environment
+
+[general]
+enabled_modules = ["cpu", "memory", "disk", "gpu", "network", "temperature", "processes", "system"]
+collection_interval = 30000  # milliseconds
+startup_delay = 5000        # milliseconds
+
+[mqtt]
+host = "localhost"          # MQTT broker hostname/IP
+port = 1883                 # MQTT broker port
+client_id_prefix = "systant" # Prefix for MQTT client ID
+username = ""               # MQTT username (optional)
+password = ""               # MQTT password (optional)
+qos = 0                     # MQTT QoS level
+
+# Home Assistant MQTT Discovery Configuration
+[homeassistant]
+discovery_enabled = true              # Enable/disable HA auto-discovery
+discovery_prefix = "homeassistant"    # HA discovery topic prefix
+
+[cpu]
+enabled = true
+
+[memory]
+enabled = true
+show_detailed = true
+
+[disk]
+enabled = true
+include_mounts = []                                     # Only include these mounts (empty = all)
+exclude_mounts = ["/snap", "/boot", "/dev", "/sys", "/proc", "/run", "/tmp"]
+exclude_types = ["tmpfs", "devtmpfs", "squashfs", "overlay"]
+min_usage_percent = 1                                   # Minimum usage to report
+
+[gpu]
+enabled = true
+nvidia_enabled = true
+amd_enabled = true
+max_gpus = 8
+
+[network]
+enabled = true
+include_interfaces = []                                 # Only include these interfaces (empty = all)
+exclude_interfaces = ["lo", "docker0", "br-", "veth", "virbr"]
+min_bytes_threshold = 1024                              # Minimum traffic to report
+
+[temperature]
+enabled = true
+cpu_temp_enabled = true
+sensors_enabled = true
+temp_unit = "celsius"
+
+[processes]
+enabled = true
+max_processes = 10
+sort_by = "cpu"                                         # "cpu" or "memory"
+min_cpu_percent = 0.0
+min_memory_percent = 0.0
+max_command_length = 50
+
+[system]
+enabled = true
+include_uptime = true
+include_load_average = true
+include_kernel_version = true
+include_os_info = true
+
+[commands]
+enabled = true
+timeout_seconds = 30
+log_executions = true
+
+# Example commands - customize for your needs
+[[commands.available]]
+trigger = "restart"
+command = "systemctl"
+allowed_params = ["nginx", "apache2", "docker", "ssh"]
+description = "Restart system services"
+
+[[commands.available]]
+trigger = "info"
+command = "uname"
+allowed_params = ["-a"]
+description = "Show system information"
+
+[[commands.available]]
+trigger = "df"
+command = "df"
+allowed_params = ["-h", "/", "/home", "/var", "/tmp"]
+description = "Show disk usage"
+
+[[commands.available]]
+trigger = "ps"
+command = "ps"
+allowed_params = ["aux", "--sort=-pcpu", "--sort=-pmem"]
+description = "Show running processes"
+
+[[commands.available]]
+trigger = "ping"
+command = "ping"
+allowed_params = ["-c", "4", "8.8.8.8", "google.com", "1.1.1.1"]
+description = "Network connectivity test"
+
+[logging]
+level = "info"                                          # debug, info, warn, error
+log_config_changes = true
+log_metric_collection = false
\ No newline at end of file