diff --git a/infra/lmxfakeproxy/LmxFakeProxy.csproj b/infra/lmxfakeproxy/LmxFakeProxy.csproj
index 1eaf063..59a4378 100644
--- a/infra/lmxfakeproxy/LmxFakeProxy.csproj
+++ b/infra/lmxfakeproxy/LmxFakeProxy.csproj
@@ -6,6 +6,12 @@
     <ImplicitUsings>enable</ImplicitUsings>
   </PropertyGroup>
 
+  <ItemGroup>
+    <Compile Remove="tests\**\*" />
+    <Content Remove="tests\**\*" />
+    <None Remove="tests\**\*" />
+  </ItemGroup>
+
   <ItemGroup>
     <Protobuf Include="Protos/scada.proto" GrpcServices="Server" />
   </ItemGroup>
diff --git a/infra/lmxfakeproxy/Sessions/SessionManager.cs b/infra/lmxfakeproxy/Sessions/SessionManager.cs
new file mode 100644
index 0000000..6a390c7
--- /dev/null
+++ b/infra/lmxfakeproxy/Sessions/SessionManager.cs
@@ -0,0 +1,51 @@
+using System.Collections.Concurrent;
+
+namespace LmxFakeProxy.Sessions;
+
+public record SessionInfo(string ClientId, long ConnectedSinceUtcTicks);
+
+public class SessionManager
+{
+    private readonly string? _requiredApiKey;
+    private readonly ConcurrentDictionary<string, SessionInfo> _sessions = new();
+
+    public SessionManager(string? requiredApiKey)
+    {
+        _requiredApiKey = requiredApiKey;
+    }
+
+    public (bool Success, string Message, string SessionId) Connect(string clientId, string apiKey)
+    {
+        if (!CheckApiKey(apiKey))
+            return (false, "Invalid API key", string.Empty);
+
+        var sessionId = Guid.NewGuid().ToString("N");
+        var info = new SessionInfo(clientId, DateTime.UtcNow.Ticks);
+        _sessions[sessionId] = info;
+        return (true, "Connected", sessionId);
+    }
+
+    public bool Disconnect(string sessionId)
+    {
+        return _sessions.TryRemove(sessionId, out _);
+    }
+
+    public bool ValidateSession(string sessionId)
+    {
+        return _sessions.ContainsKey(sessionId);
+    }
+
+    public (bool Found, string ClientId, long ConnectedSinceUtcTicks) GetConnectionState(string sessionId)
+    {
+        if (_sessions.TryGetValue(sessionId, out var info))
+            return (true, info.ClientId, info.ConnectedSinceUtcTicks);
+        return (false, string.Empty, 0);
+    }
+
+    public bool CheckApiKey(string apiKey)
+    {
+        if (string.IsNullOrEmpty(_requiredApiKey))
+            return true;
+        return apiKey == _requiredApiKey;
+    }
+}
diff --git a/infra/lmxfakeproxy/tests/LmxFakeProxy.Tests/GlobalUsings.cs b/infra/lmxfakeproxy/tests/LmxFakeProxy.Tests/GlobalUsings.cs
new file mode 100644
index 0000000..c802f44
--- /dev/null
+++ b/infra/lmxfakeproxy/tests/LmxFakeProxy.Tests/GlobalUsings.cs
@@ -0,0 +1 @@
+global using Xunit;
diff --git a/infra/lmxfakeproxy/tests/LmxFakeProxy.Tests/SessionManagerTests.cs b/infra/lmxfakeproxy/tests/LmxFakeProxy.Tests/SessionManagerTests.cs
new file mode 100644
index 0000000..6fe47b9
--- /dev/null
+++ b/infra/lmxfakeproxy/tests/LmxFakeProxy.Tests/SessionManagerTests.cs
@@ -0,0 +1,116 @@
+namespace LmxFakeProxy.Tests;
+
+using LmxFakeProxy.Sessions;
+
+public class SessionManagerTests
+{
+    [Fact]
+    public void Connect_ReturnsUniqueSessionId()
+    {
+        var mgr = new SessionManager(null);
+        var (ok1, _, id1) = mgr.Connect("client1", "");
+        var (ok2, _, id2) = mgr.Connect("client2", "");
+        Assert.True(ok1);
+        Assert.True(ok2);
+        Assert.NotEqual(id1, id2);
+    }
+
+    [Fact]
+    public void Connect_WithValidApiKey_Succeeds()
+    {
+        var mgr = new SessionManager("secret");
+        var (ok, _, _) = mgr.Connect("client1", "secret");
+        Assert.True(ok);
+    }
+
+    [Fact]
+    public void Connect_WithInvalidApiKey_Fails()
+    {
+        var mgr = new SessionManager("secret");
+        var (ok, msg, id) = mgr.Connect("client1", "wrong");
+        Assert.False(ok);
+        Assert.Empty(id);
+        Assert.Contains("Invalid API key", msg);
+    }
+
+    [Fact]
+    public void Connect_WithNoKeyConfigured_AcceptsAnyKey()
+    {
+        var mgr = new SessionManager(null);
+        var (ok1, _, _) = mgr.Connect("c1", "anykey");
+        var (ok2, _, _) = mgr.Connect("c2", "");
+        Assert.True(ok1);
+        Assert.True(ok2);
+    }
+
+    [Fact]
+    public void Disconnect_RemovesSession()
+    {
+        var mgr = new SessionManager(null);
+        var (_, _, id) = mgr.Connect("client1", "");
+        Assert.True(mgr.ValidateSession(id));
+        var ok = mgr.Disconnect(id);
+        Assert.True(ok);
+        Assert.False(mgr.ValidateSession(id));
+    }
+
+    [Fact]
+    public void Disconnect_UnknownSession_ReturnsFalse()
+    {
+        var mgr = new SessionManager(null);
+        Assert.False(mgr.Disconnect("nonexistent"));
+    }
+
+    [Fact]
+    public void ValidateSession_ValidId_ReturnsTrue()
+    {
+        var mgr = new SessionManager(null);
+        var (_, _, id) = mgr.Connect("client1", "");
+        Assert.True(mgr.ValidateSession(id));
+    }
+
+    [Fact]
+    public void ValidateSession_InvalidId_ReturnsFalse()
+    {
+        var mgr = new SessionManager(null);
+        Assert.False(mgr.ValidateSession("bogus"));
+    }
+
+    [Fact]
+    public void GetConnectionState_ReturnsCorrectInfo()
+    {
+        var mgr = new SessionManager(null);
+        var (_, _, id) = mgr.Connect("myClient", "");
+        var (found, clientId, ticks) = mgr.GetConnectionState(id);
+        Assert.True(found);
+        Assert.Equal("myClient", clientId);
+        Assert.True(ticks > 0);
+    }
+
+    [Fact]
+    public void GetConnectionState_UnknownSession_ReturnsNotConnected()
+    {
+        var mgr = new SessionManager(null);
+        var (found, clientId, ticks) = mgr.GetConnectionState("unknown");
+        Assert.False(found);
+        Assert.Empty(clientId);
+        Assert.Equal(0, ticks);
+    }
+
+    [Fact]
+    public void CheckApiKey_NoKeyConfigured_AlwaysValid()
+    {
+        var mgr = new SessionManager(null);
+        Assert.True(mgr.CheckApiKey("anything"));
+        Assert.True(mgr.CheckApiKey(""));
+    }
+
+    [Fact]
+    public void CheckApiKey_WithKeyConfigured_ValidatesCorrectly()
+    {
+        var mgr = new SessionManager("mykey");
+        Assert.True(mgr.CheckApiKey("mykey"));
+        Assert.False(mgr.CheckApiKey("wrong"));
+        Assert.False(mgr.CheckApiKey(""));
+    }
+}