diff --git a/src/MultiSeat.Tests/Streaming/ApolloStrayKillTests.cs b/src/MultiSeat.Tests/Streaming/ApolloStrayKillTests.cs
new file mode 100644
index 0000000..1d5ef38
--- /dev/null
+++ b/src/MultiSeat.Tests/Streaming/ApolloStrayKillTests.cs
@@ -0,0 +1,98 @@
+using System.Diagnostics;
+using System.Reflection;
+using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Options;
+using MultiSeat.Service.Configuration;
+using MultiSeat.Service.Streaming;
+using Xunit;
+
+namespace MultiSeat.Tests.Streaming;
+
+/// <summary>
+/// The stray-Apollo kill against real processes and real WMI (issue #124). The unit tests in
+/// <see cref="ApolloSeatConfigMatchTests"/> cover the matching rule; this proves the whole path
+/// finds a live process by its command line, kills it, and leaves a same-named process on another
+/// seat's config alone.
+/// </summary>
+public class ApolloStrayKillTests
+{
+    private static readonly BindingFlags NonPublic = BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance;
+
+    // A copy of cmd.exe named sunshine.exe. "cmd /k rem <config>" stays alive while its redirected
+    // stdin stays open, and the config path is a real argument on the command line.
+    private static Process StartFakeApollo(string exe, string configPath)
+    {
+        var start = new ProcessStartInfo(exe)
+        {
+            RedirectStandardInput = true, RedirectStandardOutput = true,
+            UseShellExecute = false, CreateNoWindow = true
+        };
+        start.ArgumentList.Add("/k");
+        start.ArgumentList.Add("rem");
+        start.ArgumentList.Add(configPath);
+        return Process.Start(start)!;
+    }
+
+    // WMI can lag a moment behind a process that has just started.
+    private static List<int> WaitForWmi(MethodInfo query, string configPath, int expectedPid)
+    {
+        var seen = new List<int>();
+        for (var i = 0; i < 50; i++)
+        {
+            seen = (List<int>)query.Invoke(null, ["sunshine", configPath, null])!;
+            if (seen.Contains(expectedPid)) break;
+            Thread.Sleep(100);
+        }
+        return seen;
+    }
+
+    [Fact]
+    public void KillStray_KillsOnlyTheApolloOnThatSeatsConfig()
+    {
+        var directory = Path.Combine(Path.GetTempPath(), "ms-straykill-" + Guid.NewGuid().ToString("N"));
+        Directory.CreateDirectory(directory);
+        var exe = Path.Combine(directory, "sunshine.exe");
+        File.Copy(Path.Combine(Environment.SystemDirectory, "cmd.exe"), exe);
+        var targetConfig = Path.Combine(directory, "seatA", "sunshine.conf");
+        var otherConfig = Path.Combine(directory, "seatB", "sunshine.conf");
+
+        // Any real Apollo on this machine must come through untouched.
+        var realBefore = Process.GetProcessesByName("sunshine").Select(p => p.Id).ToHashSet();
+        using var target = StartFakeApollo(exe, targetConfig);
+        using var other = StartFakeApollo(exe, otherConfig);
+        try
+        {
+            var manager = new ApolloManager(NullLogger<ApolloManager>.Instance,
+                Options.Create(new MultiSeatOptions { ApolloExePath = exe }), null!, null!);
+            var query = typeof(ApolloManager).GetMethod("QueryApolloPidsForConfig", NonPublic);
+            var kill = typeof(ApolloManager).GetMethod("KillStrayApollosForConfig", NonPublic);
+            Assert.NotNull(query); // a renamed method must fail loudly, not pass vacuously
+            Assert.NotNull(kill);
+
+            // Positive control: WMI sees each fake under its own config only.
+            Assert.Equal([target.Id], WaitForWmi(query, targetConfig, target.Id));
+            Assert.Equal([other.Id], WaitForWmi(query, otherConfig, other.Id));
+
+            // Negative control: a config no process runs kills nothing.
+            Assert.Equal(0, (int)kill.Invoke(manager, [Path.Combine(directory, "nobody", "sunshine.conf"), "control"])!);
+            Assert.False(target.HasExited);
+            Assert.False(other.HasExited);
+
+            Assert.Equal(1, (int)kill.Invoke(manager, [targetConfig, "test"])!);
+            Assert.True(target.WaitForExit(5000));
+            Assert.False(other.HasExited);
+
+            var realAfter = Process.GetProcessesByName("sunshine").Select(p => p.Id).ToHashSet();
+            Assert.True(realBefore.IsSubsetOf(realAfter), "a sunshine.exe that was not ours was killed");
+
+            // Nothing is left on that config.
+            Assert.Equal(0, (int)kill.Invoke(manager, [targetConfig, "again"])!);
+        }
+        finally
+        {
+            try { if (!target.HasExited) target.Kill(true); } catch { }
+            try { if (!other.HasExited) other.Kill(true); } catch { }
+            try { Directory.Delete(directory, true); } catch { }
+        }
+    }
+}