diff --git a/doc/ADS_INTEGRATION.md b/doc/ADS_INTEGRATION.md
new file mode 100644
index 0000000..f0b6c9a
--- /dev/null
+++ b/doc/ADS_INTEGRATION.md
@@ -0,0 +1,212 @@
+# ADS Integration Architecture
+
+## Decision
+
+**Use Beckhoff.TwinCAT.Ads for direct ADS communication** instead of a custom ADS-over-MQTT relay protocol.
+
+### Context
+
+The original architecture assumed a custom relay where the monitor server would exchange ADS read/write commands as MQTT messages (`flowforge/ads/read/*`, `flowforge/ads/write/*`, `flowforge/ads/notification/*`). Research revealed this is unnecessary:
+
+- **ADS-over-MQTT is a native TwinCAT router feature** — transparent to application code. Once configured on the PLC via `TcConfig.xml`, any `AdsClient` connects normally via `AmsNetId`.
+- **`Beckhoff.TwinCAT.Ads.TcpRouter`** provides a software ADS router for non-TwinCAT systems (Linux Docker containers).
+- MQTT remains for **FlowForge internal messaging** (build notifications, progress updates) but is no longer used for ADS relay.
+
+### Consequences
+
+| Component | Before | After |
+|-----------|--------|-------|
+| **Monitor Server** | MQTT relay topics for ADS reads | `Beckhoff.TwinCAT.Ads` + `TcpRouter` for direct ADS-over-TCP |
+| **Build Server** | MQTT relay for deploy commands | `Beckhoff.TwinCAT.Ads` natively (Windows/TwinCAT router) |
+| **Shared MQTT Topics** | `flowforge/ads/read/*`, `write/*`, `notification/*` | Removed — MQTT for build notifications only |
+
+---
+
+## NuGet Packages
+
+| Package | Version | Used By | Purpose |
+|---------|---------|---------|---------|
+| `Beckhoff.TwinCAT.Ads` | 7.0.* | Monitor Server, Build Server | Core ADS client (`AdsClient`) |
+| `Beckhoff.TwinCAT.Ads.TcpRouter` | 7.0.* | Monitor Server only | Software ADS router for Linux/Docker |
+
+Both packages target .NET 8.0, .NET 10.0, and .NET Standard 2.0. They work with .NET 9.0 via the .NET Standard 2.0 target.
+
+---
+
+## Key API Patterns
+
+### Connection
+
+```csharp
+// On Windows with TwinCAT installed (build server):
+var client = new AdsClient();
+client.Connect(AmsNetId.Parse("192.168.1.100.1.1"), 851);
+
+// On Linux/Docker with TcpRouter (monitor server):
+// TcpRouter must be started first, then AdsClient connects normally.
+```
+
+**Port 851** = PLC Runtime 1 (default). Ports 852, 853 for additional runtimes.
+
+### Variable Access
+
+**Symbol-based read** (dynamic, for discovery):
+```csharp
+var loader = SymbolLoaderFactory.Create(client, settings);
+var value = loader.Symbols["MAIN.nCounter"].ReadValue();
+```
+
+**Handle-based read** (faster for repeated access):
+```csharp
+uint handle = client.CreateVariableHandle("MAIN.nCounter");
+int value = (int)client.ReadAny(handle, typeof(int));
+client.DeleteVariableHandle(handle);
+```
+
+**Sum Commands** (batch — critical for performance):
+- 4000 individual reads = 4–8 seconds
+- 4000 reads via Sum Command = ~10 ms
+- Max 500 sub-commands per call
+
+### Notifications (Monitor Server)
+
+```csharp
+client.AddDeviceNotificationEx(
+    "MAIN.nCounter",
+    AdsTransMode.OnChange,
+    cycleTime: 100,   // ms — check interval
+    maxDelay: 0,       // ms — max delay before notification
+    userData: null,
+    type: typeof(int));
+```
+
+- **Max 1024 notifications per connection**
+- Notifications fire on background threads
+- Always unregister when done (`DeleteDeviceNotification`)
+
+### PLC State Management (Build Server — Deploy)
+
+```csharp
+// Read state
+StateInfo state = client.ReadState();
+// state.AdsState == AdsState.Run / Stop / Config / etc.
+
+// Switch to config mode (required before activation)
+client.WriteControl(new StateInfo(AdsState.Reconfig, 0));
+
+// Restart to run mode
+client.WriteControl(new StateInfo(AdsState.Run, 0));
+```
+
+---
+
+## PlcAdsState Enum
+
+Mirrored in `FlowForge.Shared.Models.Ads.PlcAdsState` (no Beckhoff dependency in Shared):
+
+| Value | Name | FlowForge Meaning |
+|-------|------|--------------------|
+| 5 | **Run** | PLC running — deploy needs approval if production target |
+| 6 | **Stop** | PLC stopped — safe for deploy |
+| 11 | **Error** | PLC error — needs investigation |
+| 15 | **Config** | Config mode — safe for deploy |
+| 16 | **Reconfig** | Transitioning to config mode |
+
+Deploy lock logic: `IsSafeForDeploy = State is Stop or Config`.
+
+---
+
+## Component Architecture
+
+### Monitor Server (Linux/Docker)
+
+```
+┌─────────────────────────────────┐
+│  Monitor Container              │
+│                                 │
+│  ┌──────────────────────────┐   │
+│  │  IAdsClient              │   │      ADS-over-TCP
+│  │  (AdsClientWrapper)      │───────────────────────► PLC
+│  │  Uses: AdsClient +       │   │      Port 48898
+│  │        TcpRouter          │   │
+│  └──────────┬───────────────┘   │
+│             │                   │
+│  ┌──────────▼───────────────┐   │
+│  │  SubscriptionManager    │   │
+│  └──────────┬───────────────┘   │
+│             │                   │
+│  ┌──────────▼───────────────┐   │      SignalR
+│  │  PlcDataHub (SignalR)    │◄─────────────────── Frontend
+│  └──────────────────────────┘   │
+└─────────────────────────────────┘
+```
+
+- Each container gets a unique local `AmsNetId` (derived from IP or session ID).
+- `TcpRouter` establishes the ADS-over-TCP connection to the target PLC.
+- `AdsClient` connects through the local `TcpRouter`.
+
+### Build Server (Windows/TwinCAT)
+
+```
+┌─────────────────────────────────┐
+│  Build Server (Windows)         │
+│                                 │
+│  ┌──────────────────────────┐   │
+│  │  IAdsDeployClient        │   │      Native ADS
+│  │  (AdsDeployClient)       │───────────────────────► PLC
+│  │  Uses: AdsClient          │   │      (via TwinCAT router)
+│  └──────────────────────────┘   │
+│                                 │
+│  ┌──────────────────────────┐   │
+│  │  IAutomationInterface    │   │      COM Interop
+│  │  (ActivateConfiguration) │───────────────────────► TwinCAT XAE
+│  └──────────────────────────┘   │
+└─────────────────────────────────┘
+```
+
+- No `TcpRouter` needed — uses the native TwinCAT router on Windows.
+- Deploy sequence: connect → read state → switch to config → activate → restart → verify.
+
+---
+
+## Deploy Sequence (Build Server)
+
+1. **Connect** to target PLC via ADS (`IAdsDeployClient.ConnectAsync`)
+2. **Read PLC state** — deploy lock check (`ReadPlcStateAsync`)
+3. If running + production → require 4-eyes approval (handled by backend before queuing)
+4. **Switch to config mode** (`SwitchToConfigModeAsync` → `AdsState.Reconfig`)
+5. **Activate configuration** via Automation Interface (`IAutomationInterface.ActivateConfiguration`)
+6. **Start/restart TwinCAT** via ADS (`StartRestartTwinCatAsync` → `AdsState.Run`)
+7. **Verify** PLC is in Run state
+8. **Disconnect**
+
+---
+
+## MQTT Topic Changes
+
+### Removed
+- `flowforge/ads/read/{amsNetId}` — replaced by direct ADS reads
+- `flowforge/ads/write/{amsNetId}` — replaced by direct ADS writes
+- `flowforge/ads/notification/{amsNetId}` — replaced by ADS notifications
+
+### Retained
+- `flowforge/build/notify/{twincat-version}` — backend → build servers (wake-up signal)
+- `flowforge/build/progress/{build-id}` — build server → backend (progress updates)
+
+### Added
+- `flowforge/deploy/status/{deploy-id}` — build server → backend (deploy progress)
+
+---
+
+## References
+
+- [Beckhoff.TwinCAT.Ads NuGet](https://www.nuget.org/packages/Beckhoff.TwinCAT.Ads)
+- [Beckhoff.TwinCAT.Ads.TcpRouter NuGet](https://www.nuget.org/packages/Beckhoff.TwinCAT.Ads.TcpRouter/)
+- [ADS-over-MQTT Manual](https://download.beckhoff.com/download/document/automation/twincat3/ADS-over-MQTT_en.pdf)
+- [Beckhoff/ADS-over-MQTT_Samples](https://github.com/Beckhoff/ADS-over-MQTT_Samples)
+- [Beckhoff/TF6000_ADS_DOTNET_V5_Samples](https://github.com/Beckhoff/TF6000_ADS_DOTNET_V5_Samples)
+- [ADS Notifications](https://infosys.beckhoff.com/content/1033/tc3_adsnetref/7312578699.html)
+- [ADS Sum Commands](https://infosys.beckhoff.com/content/1033/tc3_adssamples_net/185258507.html)
+- [AdsState Enum](https://infosys.beckhoff.com/content/1033/tc3_adsnetref/7313023115.html)
+- [ITcSysManager.ActivateConfiguration](https://infosys.beckhoff.com/content/1033/tc3_automationinterface/242759819.html)
+- [Secure ADS](https://download.beckhoff.com/download/document/automation/twincat3/Secure_ADS_EN.pdf)
diff --git a/src/shared/FlowForge.Shared/Models/Ads/AdsConnectionInfo.cs b/src/shared/FlowForge.Shared/Models/Ads/AdsConnectionInfo.cs
new file mode 100644
index 0000000..ed39d17
--- /dev/null
+++ b/src/shared/FlowForge.Shared/Models/Ads/AdsConnectionInfo.cs
@@ -0,0 +1,19 @@
+// Copyright (c) 2026 Qubernetic (Biró, Csaba Attila)
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace FlowForge.Shared.Models.Ads;
+
+public record AdsConnectionInfo
+{
+    public string AmsNetId { get; init; } = string.Empty;
+    public int AdsPort { get; init; } = 851;
+
+    /// <summary>
+    /// Hostname or IP of the target PLC. Used by TcpRouter on non-TwinCAT
+    /// systems (e.g. Linux Docker containers) to establish ADS-over-TCP.
+    /// </summary>
+    public string? TargetHostname { get; init; }
+
+    /// <summary>TCP port for the ADS router on the target (default 48898).</summary>
+    public int TcpPort { get; init; } = 48898;
+}
diff --git a/src/shared/FlowForge.Shared/Models/Ads/AdsVariableSubscription.cs b/src/shared/FlowForge.Shared/Models/Ads/AdsVariableSubscription.cs
new file mode 100644
index 0000000..0c161a1
--- /dev/null
+++ b/src/shared/FlowForge.Shared/Models/Ads/AdsVariableSubscription.cs
@@ -0,0 +1,11 @@
+// Copyright (c) 2026 Qubernetic (Biró, Csaba Attila)
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace FlowForge.Shared.Models.Ads;
+
+public record AdsVariableSubscription
+{
+    public string VariablePath { get; init; } = string.Empty;
+    public int CycleTimeMs { get; init; } = 100;
+    public int MaxDelayMs { get; init; }
+}
diff --git a/src/shared/FlowForge.Shared/Models/Ads/PlcAdsState.cs b/src/shared/FlowForge.Shared/Models/Ads/PlcAdsState.cs
new file mode 100644
index 0000000..a64b8ec
--- /dev/null
+++ b/src/shared/FlowForge.Shared/Models/Ads/PlcAdsState.cs
@@ -0,0 +1,30 @@
+// Copyright (c) 2026 Qubernetic (Biró, Csaba Attila)
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace FlowForge.Shared.Models.Ads;
+
+/// <summary>
+/// Mirrors TwinCAT.Ads.AdsState for use in shared DTOs without requiring a
+/// Beckhoff NuGet dependency in the Shared library.
+/// See: https://infosys.beckhoff.com/content/1033/tc3_adsnetref/7313023115.html
+/// </summary>
+public enum PlcAdsState
+{
+    Invalid = 0,
+    Idle = 1,
+    Reset = 2,
+    Init = 3,
+    Start = 4,
+    Run = 5,
+    Stop = 6,
+    SaveConfig = 7,
+    LoadConfig = 8,
+    PowerFailure = 9,
+    PowerGood = 10,
+    Error = 11,
+    Shutdown = 12,
+    Suspend = 13,
+    Resume = 14,
+    Config = 15,
+    Reconfig = 16
+}
diff --git a/src/shared/FlowForge.Shared/Models/Ads/PlcStateDto.cs b/src/shared/FlowForge.Shared/Models/Ads/PlcStateDto.cs
new file mode 100644
index 0000000..d8bffa4
--- /dev/null
+++ b/src/shared/FlowForge.Shared/Models/Ads/PlcStateDto.cs
@@ -0,0 +1,15 @@
+// Copyright (c) 2026 Qubernetic (Biró, Csaba Attila)
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace FlowForge.Shared.Models.Ads;
+
+public record PlcStateDto
+{
+    public string AmsNetId { get; init; } = string.Empty;
+    public PlcAdsState State { get; init; }
+    public DateTimeOffset Timestamp { get; init; }
+
+    public bool IsRunning => State == PlcAdsState.Run;
+    public bool IsInConfigMode => State is PlcAdsState.Config or PlcAdsState.Reconfig;
+    public bool IsSafeForDeploy => State is PlcAdsState.Stop or PlcAdsState.Config;
+}
diff --git a/src/shared/FlowForge.Shared/Models/Deploy/DeployRequestDto.cs b/src/shared/FlowForge.Shared/Models/Deploy/DeployRequestDto.cs
index af1ca3d..28a4d44 100644
--- a/src/shared/FlowForge.Shared/Models/Deploy/DeployRequestDto.cs
+++ b/src/shared/FlowForge.Shared/Models/Deploy/DeployRequestDto.cs
@@ -8,4 +8,5 @@ public record DeployRequestDto
     public Guid ProjectId { get; init; }
     public string TargetAmsNetId { get; init; } = string.Empty;
     public string? ApproverId { get; init; }
+    public int AdsPort { get; init; } = 851;
 }
diff --git a/src/shared/FlowForge.Shared/Models/Target/PlcTargetDto.cs b/src/shared/FlowForge.Shared/Models/Target/PlcTargetDto.cs
index 8bb3d03..ced51d5 100644
--- a/src/shared/FlowForge.Shared/Models/Target/PlcTargetDto.cs
+++ b/src/shared/FlowForge.Shared/Models/Target/PlcTargetDto.cs
@@ -1,6 +1,8 @@
 // Copyright (c) 2026 Qubernetic (Biró, Csaba Attila)
 // SPDX-License-Identifier: AGPL-3.0-or-later
 
+using FlowForge.Shared.Models.Ads;
+
 namespace FlowForge.Shared.Models.Target;
 
 public record PlcTargetDto
@@ -13,4 +15,5 @@ public record PlcTargetDto
     public Guid? GroupId { get; init; }
     public bool IsProductionTarget { get; init; }
     public bool DeployLocked { get; init; }
+    public PlcAdsState? CurrentState { get; init; }
 }