3 files changed, 80 insertions, 0 deletions

diff --git a/src/Agent.Core/Sessions/AgentSession.cs b/src/Agent.Core/Sessions/AgentSession.cs
index d561c8d..07b1f16 100644
--- a/src/Agent.Core/Sessions/AgentSession.cs
+++ b/src/Agent.Core/Sessions/AgentSession.cs
@@ -1,19 +1,36 @@
+using System.Collections.Concurrent;
+using Agent.Planner;
+
 namespace Agent.Core.Sessions;
 
 public sealed class AgentSession(Guid sessionId)
 {
     private readonly object _sync = new();
     private readonly List<ConversationMessage> _conversation = [];
+    private readonly List<ExecutionResult> _executionResults = [];
+    private readonly ConcurrentDictionary<Guid, TaskGraph> _taskGraphs = new();
 
     public Guid SessionId { get; } = sessionId;
     public DateTimeOffset CreatedAt { get; } = DateTimeOffset.UtcNow;
     public DateTimeOffset LastAccessAt { get; private set; } = DateTimeOffset.UtcNow;
+    public string? Summary { get; private set; }
 
     public IReadOnlyList<ConversationMessage> Conversation
     {
         get { lock (_sync) return _conversation.ToArray(); }
     }
 
+    public IReadOnlyList<ExecutionResult> ExecutionResults
+    {
+        get { lock (_sync) return _executionResults.ToArray(); }
+    }
+
+    /// <summary>
+    /// TaskGraphs owned by this session, keyed by MCP Task ID.
+    /// One TaskGraph per agent_run execution (not shared across tasks).
+    /// </summary>
+    public ConcurrentDictionary<Guid, TaskGraph> TaskGraphs => _taskGraphs;
+
     public void Append(ConversationMessage message)
     {
         ArgumentNullException.ThrowIfNull(message);
@@ -23,4 +40,51 @@ public sealed class AgentSession(Guid sessionId)
             LastAccessAt = DateTimeOffset.UtcNow;
         }
     }
+
+    public void AppendExecutionResult(ExecutionResult result)
+    {
+        ArgumentNullException.ThrowIfNull(result);
+        lock (_sync)
+        {
+            _executionResults.Add(result);
+            LastAccessAt = DateTimeOffset.UtcNow;
+        }
+    }
+
+    public void SetSummary(string summary)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(summary);
+        lock (_sync)
+        {
+            Summary = summary;
+            LastAccessAt = DateTimeOffset.UtcNow;
+        }
+    }
+
+    /// <summary>
+    /// Removes old conversation entries from the active context set after summary compaction.
+    /// Audit/LLM logs are NOT affected — only the context-active representation is compacted.
+    /// </summary>
+    public void CompactConversation(int keepLastN)
+    {
+        lock (_sync)
+        {
+            if (_conversation.Count > keepLastN)
+                _conversation.RemoveRange(0, _conversation.Count - keepLastN);
+            LastAccessAt = DateTimeOffset.UtcNow;
+        }
+    }
+
+    /// <summary>
+    /// Removes old execution results from the active context set after summary compaction.
+    /// </summary>
+    public void CompactExecutionResults(int keepLastN)
+    {
+        lock (_sync)
+        {
+            if (_executionResults.Count > keepLastN)
+                _executionResults.RemoveRange(0, _executionResults.Count - keepLastN);
+            LastAccessAt = DateTimeOffset.UtcNow;
+        }
+    }
 }
diff --git a/src/Agent.Core/Sessions/ExecutionResult.cs b/src/Agent.Core/Sessions/ExecutionResult.cs
new file mode 100644
index 0000000..ab665fa
--- /dev/null
+++ b/src/Agent.Core/Sessions/ExecutionResult.cs
@@ -0,0 +1,11 @@
+namespace Agent.Core.Sessions;
+
+/// <summary>
+/// A tool execution result recorded in the session for context summary and audit.
+/// The full output is stored in Audit/LLM logs; this is the context-active representation.
+/// </summary>
+public sealed record ExecutionResult(
+    Guid TaskId,
+    string ToolName,
+    bool Success,
+    string Output);
\ No newline at end of file
diff --git a/src/Agent.Core/Sessions/SessionStore.cs b/src/Agent.Core/Sessions/SessionStore.cs
index 59ea02c..6224e80 100644
--- a/src/Agent.Core/Sessions/SessionStore.cs
+++ b/src/Agent.Core/Sessions/SessionStore.cs
@@ -6,6 +6,11 @@ public sealed class SessionStore
 {
     private readonly ConcurrentDictionary<Guid, AgentSession> _sessions = new();
 
+    /// <summary>
+    /// Enumerates all active sessions. Primarily for TaskGraphToolHandler to resolve graphs by TaskId.
+    /// </summary>
+    public IEnumerable<AgentSession?> Sessions => _sessions.Values;
+
     public AgentSession Create()
     {
         while (true)