diff --git a/core/module.properties b/core/module.properties
index 90a5223381f..756c5aea7e0 100644
--- a/core/module.properties
+++ b/core/module.properties
@@ -1,6 +1,6 @@
 Name: Core
 ModuleClass: org.labkey.core.CoreModule
-SchemaVersion: 26.003
+SchemaVersion: 26.004
 Label: Administration and Essential Services
 Description: The Core module provides central services such as login, \
     security, administration, folder management, user management, \
diff --git a/core/resources/schemas/dbscripts/postgresql/core-25.008-25.009.sql b/core/resources/schemas/dbscripts/postgresql/core-25.008-25.009.sql
index 0e03311ca13..c7dc1519f74 100644
--- a/core/resources/schemas/dbscripts/postgresql/core-25.008-25.009.sql
+++ b/core/resources/schemas/dbscripts/postgresql/core-25.008-25.009.sql
@@ -1,3 +1 @@
 ALTER TABLE core.Documents ADD ParentType VARCHAR(300);
-
-SELECT core.executeJavaUpgradeCode('populateAttachmentParentTypeColumn');
diff --git a/core/resources/schemas/dbscripts/postgresql/core-25.009-25.010.sql b/core/resources/schemas/dbscripts/postgresql/core-25.009-25.010.sql
index 07546062a3a..774da99d529 100644
--- a/core/resources/schemas/dbscripts/postgresql/core-25.009-25.010.sql
+++ b/core/resources/schemas/dbscripts/postgresql/core-25.009-25.010.sql
@@ -4,5 +4,5 @@
 DELETE FROM core.Documents WHERE
     Container = (SELECT EntityId FROM core.Containers WHERE Parent IS NULL) AND
     Parent = (SELECT EntityId FROM core.Containers WHERE Parent IS NULL) AND
-    ParentType IS NULL AND
+    ParentType IS NULL AND -- ParentType is always NULL at this point, since populating the column is deferred. But the DocumentName condition below is sufficiently specific.
     (DocumentName LIKE 'auth_header_logo_%' OR DocumentName LIKE 'auth_login_page_logo_%');
diff --git a/core/resources/schemas/dbscripts/postgresql/core-26.000-26.001.sql b/core/resources/schemas/dbscripts/postgresql/core-26.000-26.001.sql
deleted file mode 100644
index 92b17b23648..00000000000
--- a/core/resources/schemas/dbscripts/postgresql/core-26.000-26.001.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- Extraction of parent EntityIds from data class LSIDs has been fixed, so re-run population of the ParentType column.
--- Keep the invocation in core-25.008-25.009.sql since core-25.009-25.010.sql relies on ParentType being populated.
-SELECT core.executeJavaUpgradeCode('populateAttachmentParentTypeColumn');
diff --git a/core/resources/schemas/dbscripts/postgresql/core-26.003-26.004.sql b/core/resources/schemas/dbscripts/postgresql/core-26.003-26.004.sql
new file mode 100644
index 00000000000..baa19d4e91e
--- /dev/null
+++ b/core/resources/schemas/dbscripts/postgresql/core-26.003-26.004.sql
@@ -0,0 +1,3 @@
+-- Detection of the data class Compound.Structure2D attachment column was corrected in a recent PR: https://github.com/LabKey/platform/pull/7513
+-- This re-populates the ParentType column to pick up those changes.
+SELECT core.executeJavaUpgradeCode('populateAttachmentParentTypeColumn');
diff --git a/core/resources/schemas/dbscripts/sqlserver/core-25.008-25.009.sql b/core/resources/schemas/dbscripts/sqlserver/core-25.008-25.009.sql
index 468a4ff1b0e..90d4b8792d7 100644
--- a/core/resources/schemas/dbscripts/sqlserver/core-25.008-25.009.sql
+++ b/core/resources/schemas/dbscripts/sqlserver/core-25.008-25.009.sql
@@ -1,3 +1 @@
 ALTER TABLE core.Documents ADD ParentType NVARCHAR(300);
-
-EXEC core.executeJavaUpgradeCode 'populateAttachmentParentTypeColumn';
diff --git a/core/resources/schemas/dbscripts/sqlserver/core-25.009-25.010.sql b/core/resources/schemas/dbscripts/sqlserver/core-25.009-25.010.sql
index 07546062a3a..774da99d529 100644
--- a/core/resources/schemas/dbscripts/sqlserver/core-25.009-25.010.sql
+++ b/core/resources/schemas/dbscripts/sqlserver/core-25.009-25.010.sql
@@ -4,5 +4,5 @@
 DELETE FROM core.Documents WHERE
     Container = (SELECT EntityId FROM core.Containers WHERE Parent IS NULL) AND
     Parent = (SELECT EntityId FROM core.Containers WHERE Parent IS NULL) AND
-    ParentType IS NULL AND
+    ParentType IS NULL AND -- ParentType is always NULL at this point, since populating the column is deferred. But the DocumentName condition below is sufficiently specific.
     (DocumentName LIKE 'auth_header_logo_%' OR DocumentName LIKE 'auth_login_page_logo_%');
diff --git a/core/resources/schemas/dbscripts/sqlserver/core-26.000-26.001.sql b/core/resources/schemas/dbscripts/sqlserver/core-26.000-26.001.sql
deleted file mode 100644
index be2043e0c12..00000000000
--- a/core/resources/schemas/dbscripts/sqlserver/core-26.000-26.001.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- Extraction of parent EntityIds from data class LSIDs has been fixed, so re-run population of the ParentType column.
--- Keep the invocation in core-25.008-25.009.sql since core-25.009-25.010.sql relies on ParentType being populated.
-EXEC core.executeJavaUpgradeCode 'populateAttachmentParentTypeColumn';
diff --git a/core/resources/schemas/dbscripts/sqlserver/core-26.003-26.004.sql b/core/resources/schemas/dbscripts/sqlserver/core-26.003-26.004.sql
new file mode 100644
index 00000000000..f7a61fa3c86
--- /dev/null
+++ b/core/resources/schemas/dbscripts/sqlserver/core-26.003-26.004.sql
@@ -0,0 +1,3 @@
+-- Detection of the data class Compound.Structure2D attachment column was corrected in a recent PR: https://github.com/LabKey/platform/pull/7513
+-- This re-populates the ParentType column to pick up those changes.
+EXEC core.executeJavaUpgradeCode 'populateAttachmentParentTypeColumn';
diff --git a/core/src/org/labkey/core/CoreUpgradeCode.java b/core/src/org/labkey/core/CoreUpgradeCode.java
index fdc15f89175..4001279f522 100644
--- a/core/src/org/labkey/core/CoreUpgradeCode.java
+++ b/core/src/org/labkey/core/CoreUpgradeCode.java
@@ -15,6 +15,7 @@
  */
 package org.labkey.core;
 
+import jakarta.servlet.ServletContext;
 import org.apache.logging.log4j.Logger;
 import org.labkey.api.attachments.AttachmentParentType;
 import org.labkey.api.attachments.AttachmentService;
@@ -29,6 +30,8 @@
 import org.labkey.api.module.ModuleLoader;
 import org.labkey.api.security.Directive;
 import org.labkey.api.settings.AppProps;
+import org.labkey.api.util.ContextListener;
+import org.labkey.api.util.StartupListener;
 import org.labkey.api.util.logging.LogHelper;
 import org.labkey.core.security.AllowedExternalResourceHosts;
 import org.labkey.core.security.AllowedExternalResourceHosts.AllowedHost;
@@ -82,38 +85,55 @@ public static void migrateAllowedExternalConnectionHosts(ModuleContext context)
     }
 
     /**
-     * Called from core-25.008-25.009.sql
-     * Called from core-26.000-26.001.sql
+     * Called from core-26.003-26.004.sql
      */
     @SuppressWarnings("unused")
+    // @DeferredUpgrade ensures that the upgrade code method gets queued in the database so the listener eventually
+    // gets registered and run, even in the case of an upgrade failure or server shutdown.
     @DeferredUpgrade
     public static void populateAttachmentParentTypeColumn(ModuleContext context)
     {
         if (context.isNewInstall())
             return;
 
-        for (AttachmentParentType type : AttachmentService.get().getAttachmentParentTypes())
+        // This code needs to run after all @DeferredUpgrades are complete. In particular, it needs to wait for
+        // ExperimentUpgradeCode.addRowIdToProvisionedDataClassTables() to restructure data class provisioned tables.
+        ContextListener.addStartupListener(new StartupListener()
         {
-            LOG.info("Populating attachment parent type for {}", type.getUniqueName());
-
-            SQLFragment updateSql = new SQLFragment("UPDATE ")
-                .append(CoreSchema.getInstance().getTableInfoDocuments())
-                .append(" SET ParentType = ?")
-                .add(type.getUniqueName())
-                .append(" WHERE ");
-            // TODO: This is the only caller of addWhereSql(), which can be removed when this upgrade code is deleted.
-            type.addWhereSql(updateSql, "Parent", "DocumentName");
-
-            new SqlExecutor(CoreSchema.getInstance().getSchema()).execute(updateSql);
-        }
+            @Override
+            public String getName()
+            {
+                return "Populate Attachment Parent Types";
+            }
+
+            @Override
+            public void moduleStartupComplete(ServletContext servletContext)
+            {
+                for (AttachmentParentType type : AttachmentService.get().getAttachmentParentTypes())
+                {
+                    LOG.info("Populating attachment parent type for {}", type.getUniqueName());
+
+                    SQLFragment updateSql = new SQLFragment("UPDATE ")
+                        .append(CoreSchema.getInstance().getTableInfoDocuments())
+                        .append(" SET ParentType = ?")
+                        .add(type.getUniqueName())
+                        .append(" WHERE ");
+                    // TODO: This is the only caller of addWhereSql(), which can be removed when this upgrade code is deleted.
+                    type.addWhereSql(updateSql, "Parent", "DocumentName");
+
+                    new SqlExecutor(CoreSchema.getInstance().getSchema()).execute(updateSql);
+                }
+            }
+        });
     }
 
     /**
-     * This is not invoked from any script yet. We want to make sure our orphaned attachment detection is perfect
-     * before blanket deleting them.
+     * This is not invoked from any script yet. We want to make sure our orphaned attachment detection is well tested
+     * and reviewed before blanket deleting them. TODO: Do not just call this from a script! We likely need to work
+     * this code into a StartupListener like we do above. Or integrate them into one. Or something.
      */
-    @DeferredUpgrade // Need to execute this after AttachmentTypes are registered
     @SuppressWarnings("unused")
+    @DeferredUpgrade // Need to execute this after AttachmentTypes are registered
     public static void deleteOrphanedAttachments(ModuleContext context)
     {
         if (context.isNewInstall())
diff --git a/experiment/src/org/labkey/experiment/ExperimentUpgradeCode.java b/experiment/src/org/labkey/experiment/ExperimentUpgradeCode.java
index e693224a7ec..c821141996b 100644
--- a/experiment/src/org/labkey/experiment/ExperimentUpgradeCode.java
+++ b/experiment/src/org/labkey/experiment/ExperimentUpgradeCode.java
@@ -122,6 +122,7 @@ public class ExperimentUpgradeCode implements UpgradeCode
     @SuppressWarnings("unused")
     public static void ensureBigObjectIds(ModuleContext context)
     {
+        // We force dev mode deployments to use BIGINT ObjectIds everywhere to ensure comprehensive testing
         if (AppProps.getInstance().isDevMode() && ModuleLoader.getInstance().shouldInsertData())
         {
             DbScope primary = DbScope.getLabKeyScope();
@@ -695,7 +696,7 @@ private String bracketIt(String name)
     }
 
     /**
-     * Called from exp-26.004-26.005.sql, on SQL Server only
+     * Called from exp-26.004-26.005.sql on SQL Server only
      * GitHub Issue 869: Long table/column names cause SQL Server migration to fail
      * Query all table & column storage names and rename the ones that are too long for PostgreSQL
      * TODO: When this upgrade code is removed, get rid of the StorageProvisionerImpl.makeTableName() method it uses.