diff --git a/Plant3D2026/P_Rec_Annot/src/PRecAnnot.Plant3D2026/PlantReadPath.cs b/Plant3D2026/P_Rec_Annot/src/PRecAnnot.Plant3D2026/PlantReadPath.cs
index 346d822..b140aad 100644
--- a/Plant3D2026/P_Rec_Annot/src/PRecAnnot.Plant3D2026/PlantReadPath.cs
+++ b/Plant3D2026/P_Rec_Annot/src/PRecAnnot.Plant3D2026/PlantReadPath.cs
@@ -483,7 +483,9 @@ internal sealed class PlantViewportMembershipReader
         try
         {
             var openedByQuery = false;
-            var sourceDatabase = sourceId.GetDatabase(false, ref openedByQuery);
+            // The source model is normally not an active document in an Ortho /b session.
+            // Ask MdObjectId to open its source database read-only and dispose it below when it did.
+            var sourceDatabase = sourceId.GetDatabase(true, ref openedByQuery);
             try
             {
                 stage = "StartTransaction";
diff --git a/Plant3D2026/P_Rec_Annot/tests/PRecAnnot.Core.Tests/PxpOaRegistrationTests.cs b/Plant3D2026/P_Rec_Annot/tests/PRecAnnot.Core.Tests/PxpOaRegistrationTests.cs
index d1cb61a..82f101d 100644
--- a/Plant3D2026/P_Rec_Annot/tests/PRecAnnot.Core.Tests/PxpOaRegistrationTests.cs
+++ b/Plant3D2026/P_Rec_Annot/tests/PRecAnnot.Core.Tests/PxpOaRegistrationTests.cs
@@ -37,4 +37,5 @@ public sealed class PxpOaRegistrationTests
     [Fact] public void ScriptDrivenPxpOa_UsesPreparedFixtureContextBeforeImplicitLookup() => Assert.Contains("TryGetPreparedContext(document, out var scriptContext)", Entry);
     [Fact] public void ScriptDrivenPrepare_SelectsCanonicalTargetAndRetainsReadOnlyContext() { Assert.Contains("preparedContext = context", Observer); Assert.Contains("selectedTargetSnapshotId = candidates[0]", Observer); }
     [Fact] public void PlacementReadFailure_IsDiagnosedInsteadOfBeingSilentlyDiscarded() { var source = File.ReadAllText(Path.Combine(ProjectRoot, "PlantReadPath.cs")); Assert.Contains("OrthoPipePlacementReadFailed", source); Assert.Contains("ORTHO_PIPE_PLACEMENT_UNAVAILABLE", source); }
+    [Fact] public void PlacementReader_OpensSourceDatabaseWhenItIsNotActive() { var source = File.ReadAllText(Path.Combine(ProjectRoot, "PlantReadPath.cs")); Assert.Contains("sourceId.GetDatabase(true, ref openedByQuery)", source); }
 }