From 90e521413b42881e7e4a0df0fe62b862b5c4e057 Mon Sep 17 00:00:00 2001
From: Steve Sanderson <SteveSandersonMS@users.noreply.github.com>
Date: Tue, 7 Apr 2026 14:40:23 +0100
Subject: [PATCH] fix: resolve .NET E2E race conditions in cancellation and
 multi-client tests

SessionTests: SendAndWait_Throws_OperationCanceledException_When_Token_Cancelled
did not wait for the agent to go idle after cancellation, leaking proxy
requests into subsequent tests (causing Customized_SystemMessage_Config to fail).

MultiClientTests: One_Client_Approves_Permission_And_Both_See_The_Result
asserted PermissionCompletedEvent on client2 immediately after session1 went
idle, but event propagation to client2 is async and may not have arrived yet.
---
 dotnet/test/MultiClientTests.cs |  5 +++++
 dotnet/test/SessionTests.cs     | 14 ++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/dotnet/test/MultiClientTests.cs b/dotnet/test/MultiClientTests.cs
index bdd264a4a5..0f12a3cec1 100644
--- a/dotnet/test/MultiClientTests.cs
+++ b/dotnet/test/MultiClientTests.cs
@@ -170,6 +170,9 @@ public async Task One_Client_Approves_Permission_And_Both_See_The_Result()
         var client1Events = new ConcurrentBag<SessionEvent>();
         var client2Events = new ConcurrentBag<SessionEvent>();
 
+        // Wait for PermissionCompletedEvent on client2 which may arrive slightly after session1 goes idle
+        var client2PermissionCompleted = TestHelper.GetNextEventOfTypeAsync<PermissionCompletedEvent>(session2);
+
         using var sub1 = session1.On(evt => client1Events.Add(evt));
         using var sub2 = session2.On(evt => client2Events.Add(evt));
 
@@ -181,6 +184,8 @@ public async Task One_Client_Approves_Permission_And_Both_See_The_Result()
         Assert.NotNull(response);
         Assert.NotEmpty(client1PermissionRequests);
 
+        await client2PermissionCompleted;
+
         Assert.Contains(client1Events, e => e is PermissionRequestedEvent);
         Assert.Contains(client2Events, e => e is PermissionRequestedEvent);
         Assert.Contains(client1Events, e => e is PermissionCompletedEvent);
diff --git a/dotnet/test/SessionTests.cs b/dotnet/test/SessionTests.cs
index d0084c62ee..9bd03f186b 100644
--- a/dotnet/test/SessionTests.cs
+++ b/dotnet/test/SessionTests.cs
@@ -432,11 +432,18 @@ public async Task SendAndWait_Throws_On_Timeout()
     {
         var session = await CreateSessionAsync();
 
+        var sessionIdleTask = TestHelper.GetNextEventOfTypeAsync<SessionIdleEvent>(session);
+
         // Use a slow command to ensure timeout triggers before completion
         var ex = await Assert.ThrowsAsync<TimeoutException>(() =>
             session.SendAndWaitAsync(new MessageOptions { Prompt = "Run 'sleep 2 && echo done'" }, TimeSpan.FromMilliseconds(100)));
 
         Assert.Contains("timed out", ex.Message);
+
+        // The timeout only cancels the client-side wait; abort the agent and wait for idle
+        // so leftover requests don't leak into subsequent tests.
+        await session.AbortAsync();
+        await sessionIdleTask;
     }
 
     [Fact]
@@ -446,6 +453,7 @@ public async Task SendAndWait_Throws_OperationCanceledException_When_Token_Cance
 
         // Set up wait for tool execution to start BEFORE sending
         var toolStartTask = TestHelper.GetNextEventOfTypeAsync<ToolExecutionStartEvent>(session);
+        var sessionIdleTask = TestHelper.GetNextEventOfTypeAsync<SessionIdleEvent>(session);
 
         using var cts = new CancellationTokenSource();
 
@@ -461,6 +469,12 @@ public async Task SendAndWait_Throws_OperationCanceledException_When_Token_Cance
         cts.Cancel();
 
         await Assert.ThrowsAnyAsync<OperationCanceledException>(() => sendTask);
+
+        // Cancelling the token only cancels the client-side wait, not the server-side agent loop.
+        // Explicitly abort so the agent stops, then wait for idle to ensure we're not still
+        // running this agent's operations in the context of a subsequent test.
+        await session.AbortAsync();
+        await sessionIdleTask;
     }
 
     [Fact]