diff --git a/docs/requirements/Component-DeploymentManager.md b/docs/requirements/Component-DeploymentManager.md
index ececfb32..17173f37 100644
--- a/docs/requirements/Component-DeploymentManager.md
+++ b/docs/requirements/Component-DeploymentManager.md
@@ -167,7 +167,11 @@ one is parallel:
    does not reintroduce serialization. Shape mirrors
    `ArtifactDeploymentService.DeployCoreAsync`.
 3. **Finalize (serial).** Commit terminal statuses, apply post-success side
-   effects, write audit rows, release each operation lock.
+   effects, write audit rows, release each operation lock. Each finalised
+   instance's settled rows (staged `PendingDeployment`, snapshot, deployment
+   record) are then detached from the batch's shared unit of work, so the batch
+   does not hold N configs' JSON in the change tracker — or re-scan them on every
+   later save — until it ends (review 2026-10-21 04/M3).
 
 **Disabled instances are skipped.** A bulk site deploy never touches an instance
 in `Disabled` — no flatten, no send, no state change — because deploy is a legal
diff --git a/src/ZB.MOM.WW.ScadaBridge.Commons/Interfaces/Repositories/IDeploymentManagerRepository.cs b/src/ZB.MOM.WW.ScadaBridge.Commons/Interfaces/Repositories/IDeploymentManagerRepository.cs
index 91e6637f..24ef39bc 100644
--- a/src/ZB.MOM.WW.ScadaBridge.Commons/Interfaces/Repositories/IDeploymentManagerRepository.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.Commons/Interfaces/Repositories/IDeploymentManagerRepository.cs
@@ -466,4 +466,17 @@ public interface IDeploymentManagerRepository
     /// </summary>
     /// <returns>The number of tracked entries detached (0 when nothing was pending).</returns>
     int DetachPendingChanges();
+
+    /// <summary>
+    /// Stops tracking the SETTLED deployment rows of one instance — its
+    /// <see cref="PendingDeployment"/>, <see cref="DeployedConfigSnapshot"/> and
+    /// <see cref="DeploymentRecord"/> entries in the <c>Unchanged</c> state. A bulk site deploy
+    /// shares one scoped unit of work across every instance; without this, each finalised
+    /// instance's config JSON (staged copy, old and new snapshot) stays tracked for the rest of
+    /// the batch and every later <c>SaveChanges</c> re-scans it. Entries with pending writes are
+    /// left alone.
+    /// </summary>
+    /// <param name="instanceId">The instance whose settled rows to stop tracking.</param>
+    /// <returns>The number of entries detached.</returns>
+    int DetachSettledDeploymentRows(int instanceId);
 }
diff --git a/src/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase/Repositories/DeploymentManagerRepository.cs b/src/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase/Repositories/DeploymentManagerRepository.cs
index 8c7f8ce0..255f2245 100644
--- a/src/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase/Repositories/DeploymentManagerRepository.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase/Repositories/DeploymentManagerRepository.cs
@@ -844,6 +844,27 @@ public class DeploymentManagerRepository : IDeploymentManagerRepository
         return pending.Count;
     }
 
+    /// <inheritdoc />
+    public int DetachSettledDeploymentRows(int instanceId)
+    {
+        // Enumerated into a list first: changing State mutates the tracker.
+        var settled = _dbContext.ChangeTracker.Entries()
+            .Where(e => e.State == EntityState.Unchanged
+                        && e.Entity switch
+                        {
+                            PendingDeployment p => p.InstanceId == instanceId,
+                            DeployedConfigSnapshot s => s.InstanceId == instanceId,
+                            DeploymentRecord r => r.InstanceId == instanceId,
+                            _ => false
+                        })
+            .ToList();
+
+        foreach (var entry in settled)
+            entry.State = EntityState.Detached;
+
+        return settled.Count;
+    }
+
     /// <summary>
     /// Flat shape of the deployment-record ⋈ instance join used to compose the list
     /// query. A named type rather than an anonymous one so
diff --git a/src/ZB.MOM.WW.ScadaBridge.DeploymentManager/DeploymentService.cs b/src/ZB.MOM.WW.ScadaBridge.DeploymentManager/DeploymentService.cs
index 9c217a7d..12141524 100644
--- a/src/ZB.MOM.WW.ScadaBridge.DeploymentManager/DeploymentService.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.DeploymentManager/DeploymentService.cs
@@ -1051,6 +1051,13 @@ public class DeploymentService
                 {
                     step.LockHandle?.Dispose();
                 }
+
+                // This instance is done. The batch shares ONE scoped unit of work, so
+                // without this its staged copy and old/new snapshot JSON would stay
+                // tracked (and re-scanned by every later SaveChanges) until the whole
+                // batch ends; dropping the step's own copy of the config lets it go too.
+                _repository.DetachSettledDeploymentRows(step.Instance.Id);
+                prepared[finalizedUpTo] = step with { ConfigJson = string.Empty };
             }
         }
         catch (Exception ex)
diff --git a/tests/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Tests/PendingDeploymentRepositoryTests.cs b/tests/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Tests/PendingDeploymentRepositoryTests.cs
index e97d8a02..24774dbc 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Tests/PendingDeploymentRepositoryTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Tests/PendingDeploymentRepositoryTests.cs
@@ -3,6 +3,7 @@ using ZB.MOM.WW.ScadaBridge.Commons.Entities.Deployment;
 using ZB.MOM.WW.ScadaBridge.Commons.Entities.Instances;
 using ZB.MOM.WW.ScadaBridge.Commons.Entities.Sites;
 using ZB.MOM.WW.ScadaBridge.Commons.Entities.Templates;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
 using ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Repositories;
 
 namespace ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Tests;
@@ -416,4 +417,37 @@ public class PendingDeploymentRepositoryTests : IDisposable
         var row = await _repository.GetPendingDeploymentByIdAsync("dep-x");
         Assert.Equal("{\"fresh\":true}", row!.ConfigurationJson);
     }
+
+    /// <summary>
+    /// review 2026-10-21 04/M3: detaching an instance's settled rows stops tracking its saved
+    /// pending row, snapshot and deployment record, and leaves another instance's rows and any
+    /// entry with a pending write alone.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task DetachSettledDeploymentRows_DetachesOnlyThatInstancesUnchangedRows()
+    {
+        var mine = await SeedInstanceAsync("InstM3a");
+        var other = await SeedInstanceAsync("InstM3b");
+        await _repository.AddPendingDeploymentAsync(NewPending("m3-mine", mine, "{}"));
+        await _repository.AddPendingDeploymentAsync(NewPending("m3-other", other, "{}"));
+        await _repository.AddDeployedSnapshotAsync(new DeployedConfigSnapshot("m3-mine", "rev", "{}") { InstanceId = mine });
+        var record = new DeploymentRecord("m3-mine", "admin") { InstanceId = mine, Status = DeploymentStatus.Success };
+        await _repository.AddDeploymentRecordAsync(record);
+        await _repository.SaveChangesAsync();
+
+        var detached = _repository.DetachSettledDeploymentRows(mine);
+
+        Assert.Equal(3, detached);
+        Assert.DoesNotContain(_context.ChangeTracker.Entries<PendingDeployment>(), e => e.Entity.InstanceId == mine);
+        Assert.Empty(_context.ChangeTracker.Entries<DeployedConfigSnapshot>());
+        Assert.Empty(_context.ChangeTracker.Entries<DeploymentRecord>());
+        Assert.Contains(_context.ChangeTracker.Entries<PendingDeployment>(), e => e.Entity.InstanceId == other);
+
+        // A row with a pending write is never detached.
+        await _repository.AddDeploymentRecordAsync(
+            new DeploymentRecord("m3-unsaved", "admin") { InstanceId = mine, Status = DeploymentStatus.InProgress });
+        Assert.Equal(0, _repository.DetachSettledDeploymentRows(mine));
+        Assert.Single(_context.ChangeTracker.Entries<DeploymentRecord>());
+    }
 }
diff --git a/tests/ZB.MOM.WW.ScadaBridge.DeploymentManager.Tests/DeploySiteAsyncTests.cs b/tests/ZB.MOM.WW.ScadaBridge.DeploymentManager.Tests/DeploySiteAsyncTests.cs
index 27092d24..22d2d51e 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.DeploymentManager.Tests/DeploySiteAsyncTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.DeploymentManager.Tests/DeploySiteAsyncTests.cs
@@ -592,6 +592,26 @@ public class DeploySiteAsyncTests : TestKit
         Assert.All(sessions, s => Assert.Same(sessions[0], s));
     }
 
+    /// <summary>
+    /// review 2026-10-21 04/M3: once an instance is finalised its settled deployment rows are
+    /// detached from the batch's shared unit of work, so N instances' config JSON is not held
+    /// (and re-scanned by every later save) for the rest of the batch.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task DeploySiteAsync_DetachesEachInstancesSettledRowsAfterFinalize()
+    {
+        ArrangeInstances(3);
+        var applied = new ConcurrentBag<string>();
+        var commActor = Sys.ActorOf(Props.Create(() => new RecordingSiteActor(applied)));
+
+        var result = await CreateService(commActor, maxParallelism: 3).DeploySiteAsync(SiteId, "admin");
+
+        Assert.Equal(3, result.Value.SuccessCount);
+        foreach (var id in new[] { 1, 2, 3 })
+            _repo.Received(1).DetachSettledDeploymentRows(id);
+    }
+
     /// <summary>
     /// <c>force</c> restores the unconditional behaviour for operators whose
     /// site state central cannot see — a restored data volume or a rebuilt node