diff --git a/tests/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.ParityTests/ScanStateProbeParityTests.cs b/tests/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.ParityTests/ScanStateProbeParityTests.cs
new file mode 100644
index 0000000..9efad27
--- /dev/null
+++ b/tests/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.ParityTests/ScanStateProbeParityTests.cs
@@ -0,0 +1,100 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.ParityTests;
+
+/// <summary>
+///     PR 5.8 — Per-platform <c>ScanState</c> probe parity. The legacy backend's
+///     <c>GalaxyRuntimeProbeManager</c> and the in-process backend's
+///     <c>PerPlatformProbeWatcher</c> (PR 4.7) must surface the same per-host
+///     <see cref="HostConnectivityStatus"/> stream after Discover: same host name
+///     set, matching <see cref="HostState"/> per host.
+/// </summary>
+[Trait("Category", "ParityE2E")]
+[Collection(nameof(ParityCollection))]
+public sealed class ScanStateProbeParityTests
+{
+    private readonly ParityHarness _h;
+    public ScanStateProbeParityTests(ParityHarness h) => _h = h;
+
+    [Fact]
+    public async Task GetHostStatuses_emits_same_host_set_after_Discover()
+    {
+        _h.RequireBoth();
+
+        // Probe-watcher membership only refreshes after a Discover pass — drive that
+        // first so both backends have populated their per-platform tracker.
+        var snapshots = await _h.RunOnAvailableAsync(async (driver, ct) =>
+        {
+            var b = new RecordingAddressSpaceBuilder();
+            await ((ITagDiscovery)driver).DiscoverAsync(b, ct);
+            // Give the probe watcher a beat to land its initial ScanState reads —
+            // PR 4.7 subscribes per platform with bufferedUpdateIntervalMs=0 so the
+            // first push lands within ~publishingInterval (1s default).
+            await Task.Delay(1_500, ct);
+            return ((IHostConnectivityProbe)driver).GetHostStatuses();
+        }, CancellationToken.None);
+
+        var legacy = snapshots[ParityHarness.Backend.LegacyHost];
+        var mxgw = snapshots[ParityHarness.Backend.MxGateway];
+
+        // Legacy reports: client-name transport entry + every $WinPlatform/$AppEngine
+        // probe. Mxgw reports the same shape (PR 4.7). The host-name set must agree
+        // case-insensitively.
+        var legacyHosts = legacy.Select(s => s.HostName).ToHashSet(StringComparer.OrdinalIgnoreCase);
+        var mxgwHosts = mxgw.Select(s => s.HostName).ToHashSet(StringComparer.OrdinalIgnoreCase);
+
+        if (legacyHosts.Count == 0)
+        {
+            Assert.Skip("legacy backend reported no host probes — dev Galaxy may not be a multi-platform deployment");
+        }
+
+        // The transport-entry host names differ by design — legacy uses the legacy
+        // host's process-level identity, mxgw uses MxAccess.ClientName. Compare
+        // only the platform-host subset (anything that's NOT either side's transport).
+        var legacyPlatformHosts = legacyHosts.Where(h => !h.Contains("Galaxy.Host", StringComparison.OrdinalIgnoreCase)).ToHashSet(StringComparer.OrdinalIgnoreCase);
+        var mxgwPlatformHosts = mxgwHosts.Where(h => !h.Contains("OtOpcUa-Parity", StringComparison.OrdinalIgnoreCase)).ToHashSet(StringComparer.OrdinalIgnoreCase);
+
+        legacyPlatformHosts.Except(mxgwPlatformHosts, StringComparer.OrdinalIgnoreCase).ShouldBeEmpty(
+            "every $WinPlatform / $AppEngine probed by the legacy backend must appear in the mxgw probe set");
+        mxgwPlatformHosts.Except(legacyPlatformHosts, StringComparer.OrdinalIgnoreCase).ShouldBeEmpty(
+            "every $WinPlatform / $AppEngine probed by the mxgw backend must appear in the legacy probe set");
+    }
+
+    [Fact]
+    public async Task GetHostStatuses_state_per_platform_matches_across_backends()
+    {
+        _h.RequireBoth();
+
+        var snapshots = await _h.RunOnAvailableAsync(async (driver, ct) =>
+        {
+            var b = new RecordingAddressSpaceBuilder();
+            await ((ITagDiscovery)driver).DiscoverAsync(b, ct);
+            await Task.Delay(1_500, ct);
+            return ((IHostConnectivityProbe)driver).GetHostStatuses()
+                .ToDictionary(s => s.HostName, s => s.State, StringComparer.OrdinalIgnoreCase);
+        }, CancellationToken.None);
+
+        var legacy = snapshots[ParityHarness.Backend.LegacyHost];
+        var mxgw = snapshots[ParityHarness.Backend.MxGateway];
+
+        if (legacy.Count == 0 || mxgw.Count == 0)
+        {
+            Assert.Skip("one or both backends reported no host probes");
+        }
+
+        // Skip the transport entry per backend (different by design); compare the
+        // platform-host overlap.
+        var commonHosts = legacy.Keys.Intersect(mxgw.Keys, StringComparer.OrdinalIgnoreCase).ToArray();
+        if (commonHosts.Length == 0)
+        {
+            Assert.Skip("no overlapping platform hosts between backends — likely the transport names differ but no $WinPlatform was discovered");
+        }
+
+        foreach (var host in commonHosts)
+        {
+            mxgw[host].ShouldBe(legacy[host], $"HostState parity for '{host}'");
+        }
+    }
+}