diff --git a/docs/plans/2026-05-23-audit-source-node.md b/docs/plans/2026-05-23-audit-source-node.md
index 4c6e278..bd21313 100644
--- a/docs/plans/2026-05-23-audit-source-node.md
+++ b/docs/plans/2026-05-23-audit-source-node.md
@@ -469,13 +469,22 @@ migrationBuilder.AddColumn<string>(
     maxLength: 64,
     nullable: true);
 
-migrationBuilder.CreateIndex(
-    name: "IX_AuditLog_Node_Occurred",
-    table: "AuditLog",
-    columns: new[] { "SourceNode", "OccurredAtUtc" });
+// IMPORTANT: AuditLog is partitioned on ps_AuditLog_Month(OccurredAtUtc).
+// `migrationBuilder.CreateIndex(...)` lands the index on [PRIMARY], which breaks
+// `ALTER TABLE … SWITCH PARTITION` (the purge mechanism). Match the pattern used
+// by the other `IX_AuditLog_*` indexes (see 20260520142214_AddAuditLogTable.cs
+// and 20260521184044_AddAuditLogExecutionId.cs) — raw SQL with the partition
+// scheme spelled out. Keep the fluent `HasIndex(...).HasDatabaseName(...)` in
+// the EF configuration so the model snapshot stays in sync.
+migrationBuilder.Sql(@"
+CREATE NONCLUSTERED INDEX IX_AuditLog_Node_Occurred
+ON dbo.AuditLog (SourceNode, OccurredAtUtc)
+ON ps_AuditLog_Month(OccurredAtUtc);");
 ```
 
-`Down()` drops the index then the column.
+`Down()` drops the index (`IF EXISTS DROP INDEX … ON dbo.AuditLog`, raw SQL) then the column.
+
+You will *also* need to extend `AuditLogRepository.SwitchOutPartitionAsync`'s staging-table CREATE to include `SourceNode varchar(64) NULL` in the final ordinal position. `SWITCH PARTITION` rejects schema mismatches between live and staging — without this, the PartitionPurge integration tests fail.
 
 **Step 3: Update EF configuration**
 
diff --git a/src/ScadaLink.ConfigurationDatabase/Configurations/AuditLogEntityTypeConfiguration.cs b/src/ScadaLink.ConfigurationDatabase/Configurations/AuditLogEntityTypeConfiguration.cs
index 56bff18..e092b65 100644
--- a/src/ScadaLink.ConfigurationDatabase/Configurations/AuditLogEntityTypeConfiguration.cs
+++ b/src/ScadaLink.ConfigurationDatabase/Configurations/AuditLogEntityTypeConfiguration.cs
@@ -76,7 +76,8 @@ public class AuditLogEntityTypeConfiguration : IEntityTypeConfiguration<AuditEve
         // produced before this feature shipped. ASCII — varchar(64), no unicode.
         builder.Property(e => e.SourceNode)
             .HasColumnType("varchar(64)")
-            .HasMaxLength(64);
+            .HasMaxLength(64)
+            .IsUnicode(false);
 
         // Bounded unicode message column.
         builder.Property(e => e.ErrorMessage)
diff --git a/src/ScadaLink.ConfigurationDatabase/Configurations/NotificationOutboxConfiguration.cs b/src/ScadaLink.ConfigurationDatabase/Configurations/NotificationOutboxConfiguration.cs
index c8872a3..6c2c693 100644
--- a/src/ScadaLink.ConfigurationDatabase/Configurations/NotificationOutboxConfiguration.cs
+++ b/src/ScadaLink.ConfigurationDatabase/Configurations/NotificationOutboxConfiguration.cs
@@ -54,7 +54,8 @@ public class NotificationOutboxConfiguration : IEntityTypeConfiguration<Notifica
         // echoed onto NotifyDeliver audit rows (#23) for cross-row correlation.
         builder.Property(n => n.SourceNode)
             .HasColumnType("varchar(64)")
-            .HasMaxLength(64);
+            .HasMaxLength(64)
+            .IsUnicode(false);
 
         // OriginExecutionId (Audit Log #23): nullable uniqueidentifier carried from the
         // site so the dispatcher can echo it onto NotifyDeliver audit rows. No index —
diff --git a/src/ScadaLink.ConfigurationDatabase/Configurations/SiteCallEntityTypeConfiguration.cs b/src/ScadaLink.ConfigurationDatabase/Configurations/SiteCallEntityTypeConfiguration.cs
index 206ad6e..a0203ab 100644
--- a/src/ScadaLink.ConfigurationDatabase/Configurations/SiteCallEntityTypeConfiguration.cs
+++ b/src/ScadaLink.ConfigurationDatabase/Configurations/SiteCallEntityTypeConfiguration.cs
@@ -66,7 +66,8 @@ public class SiteCallEntityTypeConfiguration : IEntityTypeConfiguration<SiteCall
         // per-site, not per-node, on this table.
         builder.Property(s => s.SourceNode)
             .HasColumnType("varchar(64)")
-            .HasMaxLength(64);
+            .HasMaxLength(64)
+            .IsUnicode(false);
 
         // Indexes — names locked for reconciliation/migration discoverability.
         // Source_Created backs "calls from this site" (Central UI Site Calls page,
diff --git a/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201754_AddAuditLogSourceNode.Designer.cs b/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201754_AddAuditLogSourceNode.Designer.cs
index 860a383..af73714 100644
--- a/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201754_AddAuditLogSourceNode.Designer.cs
+++ b/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201754_AddAuditLogSourceNode.Designer.cs
@@ -118,6 +118,7 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
 
                     b.Property<string>("SourceNode")
                         .HasMaxLength(64)
+                        .IsUnicode(false)
                         .HasColumnType("varchar(64)");
 
                     b.Property<string>("SourceScript")
diff --git a/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201754_AddAuditLogSourceNode.cs b/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201754_AddAuditLogSourceNode.cs
index c6a7fd5..0499ece 100644
--- a/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201754_AddAuditLogSourceNode.cs
+++ b/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201754_AddAuditLogSourceNode.cs
@@ -30,6 +30,7 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
                 name: "SourceNode",
                 table: "AuditLog",
                 type: "varchar(64)",
+                unicode: false,
                 maxLength: 64,
                 nullable: true);
 
diff --git a/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201950_AddNotificationSourceNode.Designer.cs b/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201950_AddNotificationSourceNode.Designer.cs
index 0772cf8..d4ea3b8 100644
--- a/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201950_AddNotificationSourceNode.Designer.cs
+++ b/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201950_AddNotificationSourceNode.Designer.cs
@@ -118,6 +118,7 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
 
                     b.Property<string>("SourceNode")
                         .HasMaxLength(64)
+                        .IsUnicode(false)
                         .HasColumnType("varchar(64)");
 
                     b.Property<string>("SourceScript")
@@ -825,6 +826,7 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
 
                     b.Property<string>("SourceNode")
                         .HasMaxLength(64)
+                        .IsUnicode(false)
                         .HasColumnType("varchar(64)");
 
                     b.Property<string>("SourceScript")
diff --git a/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201950_AddNotificationSourceNode.cs b/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201950_AddNotificationSourceNode.cs
index 722329b..2510ff6 100644
--- a/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201950_AddNotificationSourceNode.cs
+++ b/src/ScadaLink.ConfigurationDatabase/Migrations/20260523201950_AddNotificationSourceNode.cs
@@ -26,6 +26,7 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
                 name: "SourceNode",
                 table: "Notifications",
                 type: "varchar(64)",
+                unicode: false,
                 maxLength: 64,
                 nullable: true);
         }
diff --git a/src/ScadaLink.ConfigurationDatabase/Migrations/20260523202131_AddSiteCallSourceNode.Designer.cs b/src/ScadaLink.ConfigurationDatabase/Migrations/20260523202131_AddSiteCallSourceNode.Designer.cs
index 4a5bbae..fe3c141 100644
--- a/src/ScadaLink.ConfigurationDatabase/Migrations/20260523202131_AddSiteCallSourceNode.Designer.cs
+++ b/src/ScadaLink.ConfigurationDatabase/Migrations/20260523202131_AddSiteCallSourceNode.Designer.cs
@@ -118,6 +118,7 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
 
                     b.Property<string>("SourceNode")
                         .HasMaxLength(64)
+                        .IsUnicode(false)
                         .HasColumnType("varchar(64)");
 
                     b.Property<string>("SourceScript")
@@ -267,6 +268,7 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
 
                     b.Property<string>("SourceNode")
                         .HasMaxLength(64)
+                        .IsUnicode(false)
                         .HasColumnType("varchar(64)");
 
                     b.Property<string>("SourceSite")
@@ -829,6 +831,7 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
 
                     b.Property<string>("SourceNode")
                         .HasMaxLength(64)
+                        .IsUnicode(false)
                         .HasColumnType("varchar(64)");
 
                     b.Property<string>("SourceScript")
diff --git a/src/ScadaLink.ConfigurationDatabase/Migrations/20260523202131_AddSiteCallSourceNode.cs b/src/ScadaLink.ConfigurationDatabase/Migrations/20260523202131_AddSiteCallSourceNode.cs
index 8db59c3..9dd92c2 100644
--- a/src/ScadaLink.ConfigurationDatabase/Migrations/20260523202131_AddSiteCallSourceNode.cs
+++ b/src/ScadaLink.ConfigurationDatabase/Migrations/20260523202131_AddSiteCallSourceNode.cs
@@ -27,6 +27,7 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
                 name: "SourceNode",
                 table: "SiteCalls",
                 type: "varchar(64)",
+                unicode: false,
                 maxLength: 64,
                 nullable: true);
         }
diff --git a/src/ScadaLink.ConfigurationDatabase/Migrations/ScadaLinkDbContextModelSnapshot.cs b/src/ScadaLink.ConfigurationDatabase/Migrations/ScadaLinkDbContextModelSnapshot.cs
index 0ff9638..d78df93 100644
--- a/src/ScadaLink.ConfigurationDatabase/Migrations/ScadaLinkDbContextModelSnapshot.cs
+++ b/src/ScadaLink.ConfigurationDatabase/Migrations/ScadaLinkDbContextModelSnapshot.cs
@@ -115,6 +115,7 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
 
                     b.Property<string>("SourceNode")
                         .HasMaxLength(64)
+                        .IsUnicode(false)
                         .HasColumnType("varchar(64)");
 
                     b.Property<string>("SourceScript")
@@ -264,6 +265,7 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
 
                     b.Property<string>("SourceNode")
                         .HasMaxLength(64)
+                        .IsUnicode(false)
                         .HasColumnType("varchar(64)");
 
                     b.Property<string>("SourceSite")
@@ -826,6 +828,7 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
 
                     b.Property<string>("SourceNode")
                         .HasMaxLength(64)
+                        .IsUnicode(false)
                         .HasColumnType("varchar(64)");
 
                     b.Property<string>("SourceScript")
diff --git a/src/ScadaLink.ConfigurationDatabase/Repositories/SiteCallAuditRepository.cs b/src/ScadaLink.ConfigurationDatabase/Repositories/SiteCallAuditRepository.cs
index cfe0478..e14d46a 100644
--- a/src/ScadaLink.ConfigurationDatabase/Repositories/SiteCallAuditRepository.cs
+++ b/src/ScadaLink.ConfigurationDatabase/Repositories/SiteCallAuditRepository.cs
@@ -171,6 +171,11 @@ WHERE TrackedOperationId = {idText}
         // and compose with the keyset cursor, so a StuckOnly page is honest:
         // never under-filled with a non-null next cursor. Mirrors how
         // NotificationOutboxRepository.QueryAsync applies NotificationOutboxFilter.StuckCutoff.
+        //
+        // SELECT-list maintenance: EF Core's FromSqlInterpolated requires every
+        // entity-tracked column to appear in the result set. Adding a new column
+        // to the SiteCall entity means extending the list below too — otherwise
+        // every read trips "The required column 'X' was not present" at runtime.
         FormattableString sql = $@"
 SELECT TOP ({paging.PageSize})
     TrackedOperationId, Channel, Target, SourceSite, SourceNode, Status, RetryCount,