3 files changed, 48 insertions, 0 deletions
diff --git a/src/Agent.Core/Sessions/AgentSession.cs b/src/Agent.Core/Sessions/AgentSession.cs
new file mode 100644
index 0000000..d561c8d
--- /dev/null
+++ b/src/Agent.Core/Sessions/AgentSession.cs
@@ -0,0 +1,26 @@
+namespace Agent.Core.Sessions;
+
+public sealed class AgentSession(Guid sessionId)
+{
+    private readonly object _sync = new();
+    private readonly List<ConversationMessage> _conversation = [];
+
+    public Guid SessionId { get; } = sessionId;
+    public DateTimeOffset CreatedAt { get; } = DateTimeOffset.UtcNow;
+    public DateTimeOffset LastAccessAt { get; private set; } = DateTimeOffset.UtcNow;
+
+    public IReadOnlyList<ConversationMessage> Conversation
+    {
+        get { lock (_sync) return _conversation.ToArray(); }
+    }
+
+    public void Append(ConversationMessage message)
+    {
+        ArgumentNullException.ThrowIfNull(message);
+        lock (_sync)
+        {
+            _conversation.Add(message);
+            LastAccessAt = DateTimeOffset.UtcNow;
+        }
+    }
+}
diff --git a/src/Agent.Core/Sessions/ConversationMessage.cs b/src/Agent.Core/Sessions/ConversationMessage.cs
new file mode 100644
index 0000000..9d48747
--- /dev/null
+++ b/src/Agent.Core/Sessions/ConversationMessage.cs
@@ -0,0 +1,3 @@
+namespace Agent.Core.Sessions;
+
+public sealed record ConversationMessage(string Role, string Content);
diff --git a/src/Agent.Core/Sessions/SessionStore.cs b/src/Agent.Core/Sessions/SessionStore.cs
new file mode 100644
index 0000000..59ea02c
--- /dev/null
+++ b/src/Agent.Core/Sessions/SessionStore.cs
@@ -0,0 +1,19 @@
+using System.Collections.Concurrent;
+
+namespace Agent.Core.Sessions;
+
+public sealed class SessionStore
+{
+    private readonly ConcurrentDictionary<Guid, AgentSession> _sessions = new();
+
+    public AgentSession Create()
+    {
+        while (true)
+        {
+            var session = new AgentSession(Guid.NewGuid());
+            if (_sessions.TryAdd(session.SessionId, session)) return session;
+        }
+    }
+
+    public bool TryGet(Guid sessionId, out AgentSession? session) => _sessions.TryGetValue(sessionId, out session);
+}