diff --git a/backend.tests/RealtimeSessionEndSessionTests.cs b/backend.tests/RealtimeSessionEndSessionTests.cs
new file mode 100644
index 0000000..4f065f8
--- /dev/null
+++ b/backend.tests/RealtimeSessionEndSessionTests.cs
@@ -0,0 +1,54 @@
+using System.Text.Json.Nodes;
+using backend.Conversations;
+using backend.Realtime;
+using backend.Tools;
+using FluentAssertions;
+using Microsoft.Extensions.DependencyInjection;
+using Xunit;
+
+namespace backend.tests;
+
+public class RealtimeSessionEndSessionTests(ApiFactory factory) : IClassFixture<ApiFactory>
+{
+    private readonly ApiFactory _factory = factory;
+
+    [Fact]
+    public async Task End_session_call_closes_session_with_reason_tool_and_skips_response_create()
+    {
+        using var scope = _factory.Services.CreateScope();
+        var log = scope.ServiceProvider.GetRequiredService<ConversationLog>();
+        var reg = new ToolRegistry(new ITool[] { new EndSessionTool() });
+        var upstream = new ScriptedRealtimeUpstream();
+        var sink = new RecordingSink();
+        var cfg = new RealtimeSettings("m", "v", "p", 30, new HashSet<string> { "end_session" });
+        var session = new RealtimeSession(Guid.NewGuid(), upstream, sink, log, reg, cfg,
+            new FakeDeviceChannel(), NullLogger.Instance);
+
+        upstream.Push(new JsonObject { ["type"] = "session.updated" });
+        var run = session.RunAsync(default);
+        await sink.WaitForAsync("session_started", TimeSpan.FromSeconds(2));
+
+        upstream.Push(new JsonObject
+        {
+            ["type"] = "response.audio.delta",
+            ["delta"] = Convert.ToBase64String(new byte[3840]),
+        });
+        upstream.Push(new JsonObject
+        {
+            ["type"] = "response.function_call_arguments.done",
+            ["call_id"] = "c1",
+            ["name"] = "end_session",
+            ["arguments"] = "{}",
+        });
+        upstream.Push(new JsonObject { ["type"] = "response.done" });
+
+        await run;
+
+        sink.Binary.Should().NotBeEmpty();
+
+        var ended = sink.Envelopes.Last(e => (string?)e["type"] == "session_ended");
+        ((string?)ended["reason"]).Should().Be("tool");
+
+        upstream.Sent.Should().NotContain(e => (string?)e["type"] == "response.create");
+    }
+}