diff --git a/src/ZB.MOM.WW.ScadaBridge.CentralUI/ScriptAnalysis/InboundScriptHost.cs b/src/ZB.MOM.WW.ScadaBridge.CentralUI/ScriptAnalysis/InboundScriptHost.cs
index fda5d3d4..607f42bb 100644
--- a/src/ZB.MOM.WW.ScadaBridge.CentralUI/ScriptAnalysis/InboundScriptHost.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.CentralUI/ScriptAnalysis/InboundScriptHost.cs
@@ -98,5 +98,21 @@ public class InboundScriptHost
             IReadOnlyDictionary<string, string> attributeValues,
             System.Threading.CancellationToken cancellationToken = default) =>
             System.Threading.Tasks.Task.CompletedTask;
+
+        /// <summary>
+        /// Waits until a named attribute on the target instance reaches the specified value,
+        /// or until the timeout elapses.
+        /// </summary>
+        /// <param name="attributeName">The name of the attribute to watch.</param>
+        /// <param name="targetValue">The value to wait for.</param>
+        /// <param name="timeout">Maximum time to wait before returning false.</param>
+        /// <param name="cancellationToken">Cancellation token.</param>
+        /// <returns>A task that resolves to true if the attribute reached the target value within the timeout, false otherwise.</returns>
+        public System.Threading.Tasks.Task<bool> WaitForAttribute(
+            string attributeName,
+            object? targetValue,
+            System.TimeSpan timeout,
+            System.Threading.CancellationToken cancellationToken = default) =>
+            System.Threading.Tasks.Task.FromResult(false);
     }
 }
diff --git a/src/ZB.MOM.WW.ScadaBridge.CentralUI/ScriptAnalysis/SandboxInboundScriptHost.cs b/src/ZB.MOM.WW.ScadaBridge.CentralUI/ScriptAnalysis/SandboxInboundScriptHost.cs
index 639a0f40..2c155945 100644
--- a/src/ZB.MOM.WW.ScadaBridge.CentralUI/ScriptAnalysis/SandboxInboundScriptHost.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.CentralUI/ScriptAnalysis/SandboxInboundScriptHost.cs
@@ -104,6 +104,21 @@ public class SandboxInboundScriptHost
             CancellationToken cancellationToken = default) =>
             throw Unavailable("SetAttributes(...)");
 
+        /// <summary>
+        /// Always throws <see cref="ScriptSandboxException"/>; cross-site routing is unavailable in a Test Run.
+        /// </summary>
+        /// <param name="attributeName">Attribute name (included in the exception message).</param>
+        /// <param name="targetValue">Unused target value.</param>
+        /// <param name="timeout">Unused timeout.</param>
+        /// <param name="cancellationToken">Unused token.</param>
+        /// <returns>Never returns; always throws <see cref="ScriptSandboxException"/>.</returns>
+        public Task<bool> WaitForAttribute(
+            string attributeName,
+            object? targetValue,
+            TimeSpan timeout,
+            CancellationToken cancellationToken = default) =>
+            throw Unavailable($"WaitForAttribute(\"{attributeName}\")");
+
         private ScriptSandboxException Unavailable(string operation) =>
             new($"Route.To(\"{_instanceCode}\").{operation} is not available in Test Run — " +
                 "cross-site routing needs a deployed site reachable over the cluster transport.");
diff --git a/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/ScriptAnalysis/ScriptAnalysisServiceTests.cs b/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/ScriptAnalysis/ScriptAnalysisServiceTests.cs
index 4b7500d3..a044e39a 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/ScriptAnalysis/ScriptAnalysisServiceTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/ScriptAnalysis/ScriptAnalysisServiceTests.cs
@@ -644,4 +644,20 @@ public class ScriptAnalysisServiceTests
             Assert.All(lines, l => Assert.Equal($"S{i}", l.Trim()));
         }
     }
+
+    // ── Inbound-script analysis surface ──────────────────────────────────
+
+    [Fact]
+    public void InboundScript_WaitForAttribute_DiagnosesClean()
+    {
+        // WaitForAttribute is a shipped inbound-script helper. The editor must
+        // not flag it as an error: the InboundScriptHost mirror must expose the
+        // method so Roslyn resolves it during static analysis.
+        var resp = _svc.Diagnose(new DiagnoseRequest(
+            Code: "var ok = await Route.To(\"site-a\").WaitForAttribute(\"Flag\", true, System.TimeSpan.FromSeconds(5));",
+            Kind: ScriptKind.InboundApi));
+
+        Assert.DoesNotContain(resp.Markers, m => m.Code.StartsWith("CS"));
+        Assert.DoesNotContain(resp.Markers, m => m.Code.StartsWith("SCADA"));
+    }
 }