From 9cfb17b64f941f80525369df45f957341a42eb27 Mon Sep 17 00:00:00 2001
From: Steve Sanderson <SteveSandersonMS@users.noreply.github.com>
Date: Mon, 16 Feb 2026 10:48:20 +0000
Subject: [PATCH] Fix ObjectDisposedException when disposing session after
 client.StopAsync()

Make CopilotSession.DisposeAsync() idempotent and tolerant to already-disposed
connections by adding an _isDisposed flag and catching ObjectDisposedException
and IOException during disposal.

Fixes #306

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 dotnet/src/Session.cs      | 21 +++++++++++++++++++--
 dotnet/test/ClientTests.cs |  9 +++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/dotnet/src/Session.cs b/dotnet/src/Session.cs
index 1f8bfd4b9..34f4d02d5 100644
--- a/dotnet/src/Session.cs
+++ b/dotnet/src/Session.cs
@@ -54,6 +54,7 @@ public partial class CopilotSession : IAsyncDisposable
     private SessionHooks? _hooks;
     private readonly SemaphoreSlim _hooksLock = new(1, 1);
     private SessionRpc? _sessionRpc;
+    private int _isDisposed;
 
     /// <summary>
     /// Gets the unique identifier for this session.
@@ -560,8 +561,24 @@ await InvokeRpcAsync<object>(
     /// </example>
     public async ValueTask DisposeAsync()
     {
-        await InvokeRpcAsync<object>(
-            "session.destroy", [new SessionDestroyRequest() { SessionId = SessionId }], CancellationToken.None);
+        if (Interlocked.Exchange(ref _isDisposed, 1) == 1)
+        {
+            return;
+        }
+
+        try
+        {
+            await InvokeRpcAsync<object>(
+                "session.destroy", [new SessionDestroyRequest() { SessionId = SessionId }], CancellationToken.None);
+        }
+        catch (ObjectDisposedException)
+        {
+            // Connection was already disposed (e.g., client.StopAsync() was called first)
+        }
+        catch (IOException)
+        {
+            // Connection is broken or closed
+        }
 
         _eventHandlers.Clear();
         _toolHandlers.Clear();
diff --git a/dotnet/test/ClientTests.cs b/dotnet/test/ClientTests.cs
index e3419f981..9e336a7e5 100644
--- a/dotnet/test/ClientTests.cs
+++ b/dotnet/test/ClientTests.cs
@@ -215,4 +215,13 @@ public void Should_Throw_When_UseLoggedInUser_Used_With_CliUrl()
             });
         });
     }
+
+    [Fact]
+    public async Task Should_Not_Throw_When_Disposing_Session_After_Stopping_Client()
+    {
+        await using var client = new CopilotClient(new CopilotClientOptions());
+        await using var session = await client.CreateSessionAsync();
+
+        await client.StopAsync();
+    }
 }