fix(mxc): align build and UBR checks with mxc-sdk platform detection

The MxcAvailability probe used stale build constants (26300 / UBR 8289)
instead of matching the @microsoft/mxc-sdk getPlatformSupport() values
(build >= 26100, UBR >= 7965 for builds 26100-26500, no UBR minimum
for builds >= 26500).

This caused false-negative sandbox unavailability on newer Windows builds
that the SDK considers supported.

Changes:
- Replace exact-equality build check with minimum-build (>= 26100) check
- Align UBR minimum from 8289 to 7965
- Relax UBR requirement for builds >= 26500 (SDK policy)
- Update tests to cover the expanded build range

Author: QQSHI13

src/OpenClaw.Shared/Mxc/MxcAvailability.cs

@@ -8,7 +8,7 @@ namespace OpenClaw.Shared.Mxc;
 /// <remarks>
 /// Backends checked:
 /// <list type="bullet">
-/// <item><see cref="IsAppContainerAvailable"/> — Windows 11 build 26300 with UBR &gt;= 8289, x64 / arm64.</item>
+/// <item><see cref="IsAppContainerAvailable"/> — Windows build &gt;= 26100 with UBR &gt;= 7965 (builds 26100–26500), x64 / arm64.</item>
 /// <item><see cref="IsWxcExecResolvable"/> — wxc-exec.exe found in the shipped tray output layout or via override.</item>
 /// <item><see cref="IsIsolationSessionAvailable"/> — requires AppContainer plus IsolationProxy.exe in System32.</item>
 /// </list>
@@ -22,14 +22,13 @@ public sealed class MxcAvailability
     /// </summary>
     public const string WxcExecOverrideEnvVar = "OPENCLAW_WXC_EXEC";
 
-    private const int SupportedBuild = 26300;
-
-    // TODO: This is all temporary and a moment in time; feature gate this correctly ASAP.
-    /// <summary>
-    /// Temporary MXC support table: only build 26300 with UBR 8289+ is enabled.
-    /// All other builds are blocked until validated and the table is updated.
-    /// </summary>
-    private const int MinSupportedUbr = 8289;
+    // Matches @microsoft/mxc-sdk platform.checkWindowsBuildVersion():
+    // - Build >= 26100 required.
+    // - Builds 26100–26500 require UBR >= 7965.
+    // - Builds >= 26500 have no UBR minimum.
+    private const int MinBuild = 26100;
+    private const int MinSupportedUbr = 7965;
+    private const int UbrRelaxedBuild = 26500;
 
     public bool IsAppContainerAvailable { get; }
     public bool IsIsolationSessionAvailable { get; }
@@ -114,14 +113,14 @@ public static MxcAvailability Probe(IOpenClawLogger? logger = null)
 
     internal static string? GetWindowsBuildUnsupportedReason(int build, int ubr)
     {
-        if (build != SupportedBuild)
-            return $"Windows build {build} is not MXC supported build {SupportedBuild}.";
+        if (build < MinBuild)
+            return $"Windows build {build} is below MXC minimum {MinBuild}.";
 
-        if (ubr < MinSupportedUbr)
+        if (build < UbrRelaxedBuild && ubr < MinSupportedUbr)
         {
             return
                 $"Windows UBR {ubr} below MXC minimum {MinSupportedUbr} " +
-                $"(for build {SupportedBuild}). " +
+                $"(for build {build}). " +
                 "Install latest cumulative update.";
         }
 

tests/OpenClaw.Shared.Tests/Mxc/MxcAvailabilityTests.cs

@@ -65,25 +65,36 @@ public void Constructor_StoresAllFields()
     }
 
     [Theory]
-    [InlineData(26299, 9999, "is not MXC supported build 26300")]
-    [InlineData(26300, 8288, "Windows UBR 8288 below MXC minimum 8289")]
-    [InlineData(26301, 9999, "is not MXC supported build 26300")]
-    [InlineData(27999, 9999, "is not MXC supported build 26300")]
-    [InlineData(28000, 9999, "is not MXC supported build 26300")]
+    [InlineData(26099, 9999, "is below MXC minimum 26100")]
+    [InlineData(26100, 7964, "Windows UBR 7964 below MXC minimum 7965")]
+    [InlineData(26300, 7964, "Windows UBR 7964 below MXC minimum 7965")]
+    [InlineData(26499, 7964, "Windows UBR 7964 below MXC minimum 7965")]
+    [InlineData(26500, 1, null)]
+    [InlineData(27000, 0, null)]
     public void GetWindowsBuildUnsupportedReason_RejectsUnsupportedBuilds(
         int build,
         int ubr,
-        string expectedReason)
+        string? expectedReason)
     {
         var reason = MxcAvailability.GetWindowsBuildUnsupportedReason(build, ubr);
 
-        Assert.NotNull(reason);
-        Assert.Contains(expectedReason, reason);
+        if (expectedReason is null)
+        {
+            Assert.Null(reason);
+        }
+        else
+        {
+            Assert.NotNull(reason);
+            Assert.Contains(expectedReason, reason);
+        }
     }
 
     [Theory]
+    [InlineData(26100, 7965)]
+    [InlineData(26100, 9999)]
     [InlineData(26300, 8289)]
-    [InlineData(26300, 9999)]
+    [InlineData(26500, 0)]
+    [InlineData(27000, 0)]
     public void GetWindowsBuildUnsupportedReason_AllowsSupportedBuilds(int build, int ubr)
     {
         var reason = MxcAvailability.GetWindowsBuildUnsupportedReason(build, ubr);