diff --git a/OpenNest.Data/SetReleaseText.cs b/OpenNest.Data/SetReleaseText.cs
index d95e4ccd..77232025 100644
--- a/OpenNest.Data/SetReleaseText.cs
+++ b/OpenNest.Data/SetReleaseText.cs
@@ -75,6 +75,25 @@ public static class SetReleaseText
             + "\n\nUndo the rest and leave these as they are, or restore them from their history.";
     }
 
+    /// <summary>
+    /// What the release did to one of its nests, and what undoing it did: "Created",
+    /// "Merged (revision 3 → 4)", "Created; undo deleted it".
+    /// </summary>
+    public static string Change(SetReleaseNest nest)
+    {
+        ArgumentNullException.ThrowIfNull(nest);
+        var text = nest.Kind == SetReleaseNestKind.Merged
+            ? $"Merged (revision {nest.RevisionBefore} → {nest.RevisionAfter})"
+            : "Created";
+        return nest.Undo switch
+        {
+            SetReleaseNestUndo.Deleted => text + "; undo deleted it",
+            SetReleaseNestUndo.Restored => text + $"; undo restored revision {nest.RevisionBefore}",
+            SetReleaseNestUndo.Skipped => text + "; undo left it as it was",
+            _ => text,
+        };
+    }
+
     /// <summary>The state of one nest of a release: its status name, or "Deleted".</summary>
     public static string NestState(SetReleaseNest nest)
     {
diff --git a/OpenNest.Tests/Data/InMemoryDrawingSets.cs b/OpenNest.Tests/Data/InMemoryDrawingSets.cs
index fa3e8097..36cfb19e 100644
--- a/OpenNest.Tests/Data/InMemoryDrawingSets.cs
+++ b/OpenNest.Tests/Data/InMemoryDrawingSets.cs
@@ -165,8 +165,19 @@ internal sealed class InMemoryDrawingSets : IDrawingSetStore
         });
     }
 
-    public Task<SetReleaseRecord> UndoReleaseAsync(Guid id, SetReleaseUndoRequest request, CancellationToken cancellationToken = default) =>
-        throw new NotSupportedException("The in-memory store does not hold nests, so it cannot undo a release.");
+    /// <summary>Every undo request, in order.</summary>
+    public List<(Guid Id, SetReleaseUndoRequest Request)> UndoRequests { get; } = new();
+
+    /// <summary>Answers an undo; this store holds no nests, so a test decides what the server says.</summary>
+    public Func<Guid, SetReleaseUndoRequest, SetReleaseRecord>? UndoHandler { get; set; }
+
+    public Task<SetReleaseRecord> UndoReleaseAsync(Guid id, SetReleaseUndoRequest request, CancellationToken cancellationToken = default)
+    {
+        UndoRequests.Add((id, new SetReleaseUndoRequest { UndoneBy = request.UndoneBy, SkipNests = request.SkipNests.ToList() }));
+        return UndoHandler is { } handler
+            ? Task.FromResult(handler(id, request))
+            : throw new NotSupportedException("The in-memory store does not hold nests, so it cannot undo a release.");
+    }
 
     private Task<DrawingSetRecord> SetArchived(Guid id, int expectedRevision, bool archived)
     {
diff --git a/OpenNest.Tests/Data/SetReleaseTextTests.cs b/OpenNest.Tests/Data/SetReleaseTextTests.cs
index cc0bf4d4..25c4f5ba 100644
--- a/OpenNest.Tests/Data/SetReleaseTextTests.cs
+++ b/OpenNest.Tests/Data/SetReleaseTextTests.cs
@@ -53,6 +53,25 @@ public class SetReleaseTextTests
         Assert.Equal("Released from set 'Synthetic kit' revision 3 ×2 by Synthetic operator", text);
     }
 
+    [Theory]
+    [InlineData(SetReleaseNestKind.Created, null, "Created")]
+    [InlineData(SetReleaseNestKind.Created, SetReleaseNestUndo.Deleted, "Created; undo deleted it")]
+    [InlineData(SetReleaseNestKind.Merged, null, "Merged (revision 3 → 4)")]
+    [InlineData(SetReleaseNestKind.Merged, SetReleaseNestUndo.Restored, "Merged (revision 3 → 4); undo restored revision 3")]
+    [InlineData(SetReleaseNestKind.Merged, SetReleaseNestUndo.Skipped, "Merged (revision 3 → 4); undo left it as it was")]
+    public void Change_SaysWhatTheReleaseAndItsUndoDid(SetReleaseNestKind kind, SetReleaseNestUndo? undo, string expected)
+    {
+        var nest = new SetReleaseNest
+        {
+            Kind = kind,
+            RevisionBefore = kind == SetReleaseNestKind.Merged ? 3 : null,
+            RevisionAfter = kind == SetReleaseNestKind.Merged ? 4 : 1,
+            Undo = undo,
+        };
+
+        Assert.Equal(expected, SetReleaseText.Change(nest));
+    }
+
     [Fact]
     public void UndoRefusal_NamesEachChangedNest_OrSaysItWasUndoneBefore()
     {
diff --git a/OpenNest.WinForms.Tests/Forms/SetReleaseFormsTests.cs b/OpenNest.WinForms.Tests/Forms/SetReleaseFormsTests.cs
index 1c4e4650..bab6d707 100644
--- a/OpenNest.WinForms.Tests/Forms/SetReleaseFormsTests.cs
+++ b/OpenNest.WinForms.Tests/Forms/SetReleaseFormsTests.cs
@@ -43,13 +43,13 @@ public class SetReleaseFormsTests
                 Assert.Equal(2, grid.Rows.Count);
                 Assert.True(skipped.Visible);
                 Assert.Contains("'SYN-OLD'", skipped.Text);
-                Field<NumericUpDown>(form, "multiplierBox").Value = 3;
+                Field<DataGridView>(form, "setGrid").Rows[0].Cells["kitsColumn"].Value = "3";
                 Assert.Equal(new object[] { 12, 9 }, grid.Rows.Cast<DataGridViewRow>().Select(r => r.Cells["partsColumn"].Value));
                 Field<TextBox>(form, "notesBox").Text = "Synthetic run";
 
                 Run(form.ReleaseAsync());
 
-                Assert.Contains("Create 2 Draft nests from set 'Synthetic kit' ×3", Assert.Single(questions));
+                Assert.Contains("Release set 'Synthetic kit' ×3 into 2 Draft nests", Assert.Single(questions));
                 Assert.Equal(2, nests.Uploaded.Count);
                 Assert.Equal(2, opened.Count);
                 Assert.All(opened, o => Assert.Equal(NestStatus.Draft, o.Nest.Status));
@@ -64,7 +64,8 @@ public class SetReleaseFormsTests
                 Assert.StartsWith("Released: 2 nests", Field<Label>(form, "statusLabel").Text);
                 Assert.All(grid.Rows.Cast<DataGridViewRow>(), r => Assert.StartsWith("Created N26-", (string)r.Cells["statusColumn"].Value));
                 Assert.False(Field<Button>(form, "releaseButton").Enabled);
-                Assert.False(Field<NumericUpDown>(form, "multiplierBox").Enabled);
+                Assert.True(Field<DataGridView>(form, "setGrid").ReadOnly);
+                Assert.False(Field<ComboBox>(form, "addSetCombo").Enabled);
             },
             TestTimeout,
             "The release test did not complete.");
@@ -188,6 +189,147 @@ public class SetReleaseFormsTests
             "The releases view test did not complete.");
     }
 
+    [Fact]
+    public void Release_OfATypedInSecondSet_MergesOneGroupIntoADraft_UnlessItIsOpen()
+    {
+        StaTestThread.Run(
+            () =>
+            {
+                var library = new PackageLibrary();
+                var a = library.Add("SYN-A", "Synthetic Steel");
+                var b = library.Add("SYN-B", "Synthetic Steel");
+                var c = library.Add("SYN-C", "Synthetic Aluminum");
+                var sets = new InMemoryDrawingSets();
+                var first = CreateSet(sets, "First kit", (a, 1), (c, 1));
+                CreateSet(sets, "Second kit", (b, 2));
+                var nests = new MemoryNests();
+                var draft = nests.AddDraft("N26-0007", "Synthetic Steel", "Grade A", 0.25);
+                var opened = new List<NestRecord>();
+                var messages = new List<string>();
+
+                using var form = new ReleaseSetForm(sets, library, nests, Server, first, (_, record) => opened.Add(record));
+                form.ShowMessage = (text, _, _) => { messages.Add(text); return DialogResult.OK; };
+                form.CreateNest = (group, _) => Task.FromResult(new Nest("N26-0100") { Units = group.Units });
+                var openTabs = new HashSet<Guid> { draft.Id };
+                form.IsNestOpen = openTabs.Contains;
+                form.Show();
+
+                Field<ComboBox>(form, "addSetCombo").Text = "second KIT";
+                Run(form.AddTypedSetAsync());
+                Assert.Equal(new[] { ("First kit", 1), ("Second kit", 1) }, form.Lines().Select(l => (l.Set.Name, l.Quantity)));
+                Assert.False(form.AddLine(first, 2));
+                Field<DataGridView>(form, "setGrid").Rows[1].Cells["kitsColumn"].Value = "2";
+
+                var grid = Field<DataGridView>(form, "groupGrid");
+                DataGridViewRow Steel() => grid.Rows.Cast<DataGridViewRow>().Single(r => ((SetReleaseGroup)r.Tag!).MaterialName == "Synthetic Steel");
+                PumpUntil(() => ((DataGridViewComboBoxCell)Steel().Cells["targetColumn"]).Items.Count == 2, "the drafts to merge into");
+                Assert.Equal(new object[] { 1, 4 }, new[] { a, b }.Select(d => (object)((SetReleaseGroup)Steel().Tag!).Items.Single(i => i.Drawing.Id == d.Id).Quantity));
+                var mergeChoice = (string)((DataGridViewComboBoxCell)Steel().Cells["targetColumn"]).Items[1]!;
+                Assert.StartsWith("Merge into N26-0007 (1 sheet", mergeChoice);
+
+                // An open draft is refused and the group stays a new nest.
+                Steel().Cells["targetColumn"].Value = mergeChoice;
+                Assert.Contains("is open in a tab here", Assert.Single(messages));
+                Assert.Equal("New Draft nest", Steel().Cells["targetColumn"].Value);
+                Assert.Empty(form.ChosenMerges());
+
+                openTabs.Clear();
+                Steel().Cells["targetColumn"].Value = mergeChoice;
+                Assert.Same(draft, form.ChosenMerges().Values.Single());
+                Assert.Contains("Merging discards the layout of 'N26-0007'", (string)Steel().Cells["statusColumn"].Value);
+                Assert.Contains("1 new Draft nest, 1 merge, 6 parts", Field<Label>(form, "summaryLabel").Text);
+
+                Run(form.ReleaseAsync());
+
+                Assert.Contains("1 new and 1 merged into existing drafts", messages[^1]);
+                var release = Assert.Single(sets.Releases);
+                Assert.Equal(new[] { ("First kit", 1), ("Second kit", 2) }, release.Sets.Select(l => (l.SetName, l.Quantity)));
+                var merged = release.Nests.Single(n => n.Kind == SetReleaseNestKind.Merged);
+                Assert.Equal((draft.Id, (int?)draft.Revision, draft.Revision + 1), (merged.NestId, merged.RevisionBefore, merged.RevisionAfter));
+                Assert.Equal(SetReleaseNestKind.Created, release.Nests.Single(n => n.NestId != draft.Id).Kind);
+                Assert.Equal(2, opened.Count);
+                Assert.StartsWith("Merged into N26-0007", (string)Steel().Cells["statusColumn"].Value);
+            },
+            TestTimeout,
+            "The multi-set merge release test did not complete.");
+    }
+
+    [Fact]
+    public void Releases_UndoOffersToLeaveChangedNests_AndShowsWhatTheReleaseDid()
+    {
+        StaTestThread.Run(
+            () =>
+            {
+                var sets = new InMemoryDrawingSets();
+                var set = CreateSet(sets);
+                var created = new SetReleaseNest { NestId = Guid.NewGuid(), MaterialName = "Synthetic Steel", Thickness = 0.25, RevisionAfter = 1, Nest = new NestRecord { Name = "N1", Status = NestStatus.Draft } };
+                var merged = new SetReleaseNest
+                {
+                    NestId = Guid.NewGuid(),
+                    Kind = SetReleaseNestKind.Merged,
+                    RevisionBefore = 3,
+                    RevisionAfter = 4,
+                    MaterialName = "Synthetic Aluminum",
+                    Thickness = 0.25,
+                    Nest = new NestRecord { Name = "N2", Status = NestStatus.Draft },
+                };
+                var release = new SetReleaseRecord
+                {
+                    Id = Guid.NewGuid(),
+                    Sets = new[]
+                    {
+                        new SetReleaseLine { SetId = set.Id, SetRevision = 1, SetName = set.Name, Quantity = 2 },
+                        new SetReleaseLine { SetId = Guid.NewGuid(), SetRevision = 1, SetName = "Other kit", Quantity = 1 },
+                    },
+                    Nests = new[] { created, merged },
+                };
+                sets.Releases.Add(release);
+                sets.UndoHandler = (_, request) =>
+                {
+                    if (request.SkipNests.Count == 0)
+                        throw new SetReleaseUndoConflictException(new SetReleaseUndoConflict
+                        {
+                            Reason = SetReleaseUndoRefusal.NestsChanged,
+                            Release = release,
+                            ChangedNests = new[] { new NestRecord { Id = merged.NestId, Name = "N2", Revision = 6, Status = NestStatus.ToBeCut } },
+                        });
+                    release.UndoneAt = new DateTime(2026, 10, 21, 12, 0, 0, DateTimeKind.Utc);
+                    created.Undo = SetReleaseNestUndo.Deleted;
+                    merged.Undo = SetReleaseNestUndo.Skipped;
+                    return release;
+                };
+                var questions = new List<string>();
+
+                using var form = new SetReleasesForm(sets, set);
+                form.ShowMessage = (text, buttons, _) =>
+                {
+                    questions.Add(text);
+                    return buttons == MessageBoxButtons.YesNo ? DialogResult.Yes : DialogResult.OK;
+                };
+                form.Show();
+                var releases = Field<DataGridView>(form, "releaseGrid");
+                var nests = Field<DataGridView>(form, "nestGrid");
+                PumpUntil(() => releases.Rows.Count == 1 && nests.Rows.Count == 2, "the releases");
+                Assert.Equal("×2 (+1 other set)", releases.Rows[0].Cells["multiplierColumn"].Value);
+                Assert.Equal(new object[] { "Created", "Merged (revision 3 → 4)" }, nests.Rows.Cast<DataGridViewRow>().Select(r => r.Cells["changeColumn"].Value));
+                Assert.True(Field<Button>(form, "undoButton").Enabled);
+
+                Run(form.UndoSelectedAsync());
+
+                Assert.Contains("1 nest it created is deleted", questions[0]);
+                Assert.Contains("1 draft it merged into goes back", questions[0]);
+                Assert.Contains("- N2: saved since the release (now revision 6, To Be Cut)", questions[1]);
+                Assert.Equal(new[] { 0, 1 }, sets.UndoRequests.Select(r => r.Request.SkipNests.Count));
+                Assert.Equal(merged.NestId, sets.UndoRequests[1].Request.SkipNests.Single());
+                PumpUntil(() => (string)releases.Rows[0].Cells["progressColumn"].Value == "Undone", "the release to read as undone");
+                Assert.Equal(new object[] { "Created; undo deleted it", "Merged (revision 3 → 4); undo left it as it was" },
+                    nests.Rows.Cast<DataGridViewRow>().Select(r => r.Cells["changeColumn"].Value));
+                Assert.False(Field<Button>(form, "undoButton").Enabled);
+            },
+            TestTimeout,
+            "The release undo test did not complete.");
+    }
+
     [Fact]
     public void Browser_Release_ReadsTheSetWithItsMembers_OnlyWhenEnabled()
     {
@@ -222,12 +364,15 @@ public class SetReleaseFormsTests
             "The browser release test did not complete.");
     }
 
-    private static DrawingSetRecord CreateSet(InMemoryDrawingSets sets, params (DrawingLibraryRecord Drawing, int Quantity)[] members)
+    private static DrawingSetRecord CreateSet(InMemoryDrawingSets sets, params (DrawingLibraryRecord Drawing, int Quantity)[] members) =>
+        CreateSet(sets, "Synthetic kit", members);
+
+    private static DrawingSetRecord CreateSet(InMemoryDrawingSets sets, string name, params (DrawingLibraryRecord Drawing, int Quantity)[] members)
     {
         var task = sets.CreateAsync(new DrawingSetRecord
         {
             Id = Guid.NewGuid(),
-            Name = "Synthetic kit",
+            Name = name,
             Customer = "Synthetic customer",
             Members = members.Select(m => new DrawingSetMember { DrawingId = m.Drawing.Id, Quantity = m.Quantity, Drawing = m.Drawing }).ToList(),
         });
@@ -301,10 +446,57 @@ public class SetReleaseFormsTests
             CancellationToken cancellationToken = default) => throw new NotSupportedException();
     }
 
-    /// <summary>Stores uploads in memory under their client-allocated ids.</summary>
+    /// <summary>Stores uploads in memory under their client-allocated ids, and drafts a release can merge into.</summary>
     private sealed class MemoryNests : INestRepository
     {
+        private readonly Dictionary<(Guid, int), byte[]> _revisions = new();
+
         public List<NestRecord> Uploaded { get; } = new();
+        public List<NestRecord> Drafts { get; } = new();
+
+        /// <summary>A Draft nest on one empty sheet, stored as a real archive at revision 3.</summary>
+        public NestRecord AddDraft(string name, string material, string grade, double thickness)
+        {
+            var nest = new Nest(name) { Units = Units.Inches, Material = new Material(material, grade), Thickness = thickness, Status = NestStatus.Draft };
+            nest.CreatePlate();
+            using var stream = new MemoryStream();
+            new NestWriter(nest).Write(stream);
+            var record = new NestRecord
+            {
+                Id = Guid.NewGuid(),
+                Revision = 3,
+                Name = name,
+                Material = material,
+                MaterialGrade = grade,
+                Thickness = thickness,
+                Status = NestStatus.Draft,
+                PlateCount = 1,
+                SavedAt = new DateTime(2026, 10, 21, 9, 0, 0, DateTimeKind.Utc),
+            };
+            _revisions[(record.Id, record.Revision)] = stream.ToArray();
+            Drafts.Add(record);
+            return record;
+        }
+
+        public Task<NestPage> QueryAsync(NestQuery query, CancellationToken ct = default)
+        {
+            var found = Drafts.Where(d => query.Status == d.Status && query.Material == d.Material
+                && query.MaterialGrade == d.MaterialGrade && query.Thickness == d.Thickness).ToList();
+            return Task.FromResult(new NestPage { Items = found, Total = found.Count, Limit = query.Limit });
+        }
+
+        public Task<byte[]?> GetRevisionFileAsync(Guid id, int revisionNumber, CancellationToken cancellationToken = default) =>
+            Task.FromResult(_revisions.TryGetValue((id, revisionNumber), out var bytes) ? bytes : null);
+
+        public Task<NestRecord> UpdateFileAsync(Guid id, byte[] nestFile, NestRecord record, int expectedRevision,
+            CancellationToken cancellationToken = default)
+        {
+            var current = Drafts.Single(d => d.Id == id);
+            Assert.Equal(current.Revision, expectedRevision);
+            var saved = new NestRecord { Id = id, Revision = expectedRevision + 1, Name = record.Name, Status = record.Status };
+            _revisions[(id, saved.Revision)] = nestFile;
+            return Task.FromResult(saved);
+        }
 
         public Task<NestRecord> UploadAsync(byte[] file, NestRecord record, CancellationToken ct = default)
         {
@@ -318,7 +510,6 @@ public class SetReleaseFormsTests
             Task.FromResult(Uploaded.FirstOrDefault(r => r.Id == id));
 
         public Task<IReadOnlyList<NestRecord>> ListAsync(CancellationToken ct = default) => throw new NotSupportedException();
-        public Task<NestPage> QueryAsync(NestQuery query, CancellationToken ct = default) => throw new NotSupportedException();
         public Task<byte[]?> GetFileAsync(Guid id, CancellationToken ct = default) => throw new NotSupportedException();
         public Task<NestRecord> UpdateFileAsync(Guid id, byte[] file, NestRecord record, CancellationToken ct = default) => throw new NotSupportedException();
         public Task<NestRecord> UpdateMetadataAsync(Guid id, NestRecord record, CancellationToken ct = default) => throw new NotSupportedException();
diff --git a/OpenNest/Controls/DrawingSetBrowser.cs b/OpenNest/Controls/DrawingSetBrowser.cs
index 1ab9cd23..f6ed1605 100644
--- a/OpenNest/Controls/DrawingSetBrowser.cs
+++ b/OpenNest/Controls/DrawingSetBrowser.cs
@@ -25,6 +25,7 @@ namespace OpenNest.Controls
         private string serverUrl;
         private INestRepository nests;
         private Action<Nest, NestRecord> openNest;
+        private Func<Guid, bool> isNestOpen = _ => false;
         private DrawingSetBrowseSession session;
         private bool pick;
         private bool busy;
@@ -101,7 +102,7 @@ namespace OpenNest.Controls
             };
             ShowRelease = set =>
             {
-                using var form = new ReleaseSetForm(sets, library, nests, this.serverUrl, set, openNest);
+                using var form = new ReleaseSetForm(sets, library, nests, this.serverUrl, set, openNest) { IsNestOpen = isNestOpen };
                 form.ShowDialog(FindForm());
             };
 
@@ -120,11 +121,14 @@ namespace OpenNest.Controls
         }
 
         /// <summary>
-        /// Shows Release, which makes nests from the selected set: uploads them through
-        /// <paramref name="nests"/> and opens each with <paramref name="openNest"/>.
+        /// Shows Release, which makes nests from the selected set and any others the operator
+        /// adds: saves them through <paramref name="nests"/> and opens each with
+        /// <paramref name="openNest"/>. <paramref name="isNestOpen"/> says whether a server nest
+        /// is open in a tab, which keeps a release from merging into it.
         /// </summary>
-        public void EnableRelease(INestRepository nests, Action<Nest, NestRecord> openNest)
+        public void EnableRelease(INestRepository nests, Action<Nest, NestRecord> openNest, Func<Guid, bool> isNestOpen = null)
         {
+            this.isNestOpen = isNestOpen ?? (_ => false);
             if (session == null || pick)
                 throw new InvalidOperationException("Release needs an initialized set browser that is not picking.");
             this.nests = nests ?? throw new ArgumentNullException(nameof(nests));
diff --git a/OpenNest/Forms/DrawingLibraryForm.cs b/OpenNest/Forms/DrawingLibraryForm.cs
index 44164435..629ae8ed 100644
--- a/OpenNest/Forms/DrawingLibraryForm.cs
+++ b/OpenNest/Forms/DrawingLibraryForm.cs
@@ -160,13 +160,14 @@ namespace OpenNest.Forms
         internal OpenNest.Controls.DrawingSetBrowser SetBrowser => setBrowser;
 
         /// <summary>
-        /// Lets the Sets tab release sets: nests are uploaded through <paramref name="nests"/>
-        /// and each is opened with <paramref name="openNest"/>.
+        /// Lets the Sets tab release sets: nests are saved through <paramref name="nests"/>
+        /// and each is opened with <paramref name="openNest"/>; a nest <paramref name="isNestOpen"/>
+        /// reports as open in a tab is never merged into.
         /// </summary>
-        public void EnableRelease(INestRepository nests, Action<Nest, NestRecord> openNest)
+        public void EnableRelease(INestRepository nests, Action<Nest, NestRecord> openNest, Func<Guid, bool> isNestOpen = null)
         {
             if (setBrowser.IsInitialized)
-                setBrowser.EnableRelease(nests, openNest);
+                setBrowser.EnableRelease(nests, openNest, isNestOpen);
         }
 
         private async void TabControl_SelectedIndexChanged(object sender, EventArgs e)
diff --git a/OpenNest/Forms/EditNestForm.cs b/OpenNest/Forms/EditNestForm.cs
index 33064430..63c54d41 100644
--- a/OpenNest/Forms/EditNestForm.cs
+++ b/OpenNest/Forms/EditNestForm.cs
@@ -1268,7 +1268,7 @@ namespace OpenNest.Forms
             using var form = new DrawingLibraryForm(library, NestStorage.Settings.ServerUrl, Nest, sets);
             // Released nests open in their own tabs beside this one.
             if (MdiParent is MainForm main)
-                form.EnableRelease(NestStorage.CreateRepository(), main.OpenServerNest);
+                form.EnableRelease(NestStorage.CreateRepository(), main.OpenServerNest, main.IsServerNestOpen);
             form.ShowDialog(this);
             if (form.AddedDrawings.Count > 0)
                 UpdateDrawingList();
diff --git a/OpenNest/Forms/MainForm.File.cs b/OpenNest/Forms/MainForm.File.cs
index 0af9af85..f5042532 100644
--- a/OpenNest/Forms/MainForm.File.cs
+++ b/OpenNest/Forms/MainForm.File.cs
@@ -45,6 +45,10 @@ namespace OpenNest.Forms
             LoadNest(nest, windowState, record.Id, NestStorage.Settings.ServerUrl, record.Revision);
         }
 
+        /// <summary>True when a tab holds the server nest <paramref name="id"/>.</summary>
+        internal bool IsServerNestOpen(Guid id) =>
+            id != Guid.Empty && MdiChildren.OfType<EditNestForm>().Any(form => form.Document.RemoteId == id);
+
         #region File Menu Events
 
         private async void New_Click(object sender, EventArgs e)
diff --git a/OpenNest/Forms/ReleaseSetForm.Designer.cs b/OpenNest/Forms/ReleaseSetForm.Designer.cs
index 45e0fd9d..63ba8d6b 100644
--- a/OpenNest/Forms/ReleaseSetForm.Designer.cs
+++ b/OpenNest/Forms/ReleaseSetForm.Designer.cs
@@ -9,6 +9,7 @@ namespace OpenNest.Forms
             if (disposing)
             {
                 cancellation?.Dispose();
+                searchCancellation?.Dispose();
                 if (components != null)
                     components.Dispose();
             }
@@ -19,12 +20,21 @@ namespace OpenNest.Forms
 
         private void InitializeComponent()
         {
+            components = new System.ComponentModel.Container();
             System.Windows.Forms.DataGridViewCellStyle rightAligned = new System.Windows.Forms.DataGridViewCellStyle();
             layoutTable = new System.Windows.Forms.TableLayoutPanel();
             setLabel = new System.Windows.Forms.Label();
+            addSetTable = new System.Windows.Forms.TableLayoutPanel();
+            addSetLabel = new System.Windows.Forms.Label();
+            addSetCombo = new System.Windows.Forms.ComboBox();
+            addSetButton = new System.Windows.Forms.Button();
+            removeSetButton = new System.Windows.Forms.Button();
+            setGrid = new System.Windows.Forms.DataGridView();
+            setNameColumn = new System.Windows.Forms.DataGridViewTextBoxColumn();
+            setCustomerColumn = new System.Windows.Forms.DataGridViewTextBoxColumn();
+            setRevisionColumn = new System.Windows.Forms.DataGridViewTextBoxColumn();
+            kitsColumn = new System.Windows.Forms.DataGridViewTextBoxColumn();
             optionsTable = new System.Windows.Forms.TableLayoutPanel();
-            multiplierLabel = new System.Windows.Forms.Label();
-            multiplierBox = new System.Windows.Forms.NumericUpDown();
             includeArchivedCheckBox = new System.Windows.Forms.CheckBox();
             notesLabel = new System.Windows.Forms.Label();
             notesBox = new System.Windows.Forms.TextBox();
@@ -37,6 +47,7 @@ namespace OpenNest.Forms
             cutTypeColumn = new System.Windows.Forms.DataGridViewTextBoxColumn();
             drawingsColumn = new System.Windows.Forms.DataGridViewTextBoxColumn();
             partsColumn = new System.Windows.Forms.DataGridViewTextBoxColumn();
+            targetColumn = new System.Windows.Forms.DataGridViewComboBoxColumn();
             statusColumn = new System.Windows.Forms.DataGridViewTextBoxColumn();
             skippedLabel = new System.Windows.Forms.Label();
             bottomTable = new System.Windows.Forms.TableLayoutPanel();
@@ -44,9 +55,11 @@ namespace OpenNest.Forms
             releaseButton = new System.Windows.Forms.Button();
             closeButton = new System.Windows.Forms.Button();
             statusLabel = new System.Windows.Forms.Label();
+            searchTimer = new System.Windows.Forms.Timer(components);
             layoutTable.SuspendLayout();
+            addSetTable.SuspendLayout();
+            ((System.ComponentModel.ISupportInitialize)setGrid).BeginInit();
             optionsTable.SuspendLayout();
-            ((System.ComponentModel.ISupportInitialize)multiplierBox).BeginInit();
             ((System.ComponentModel.ISupportInitialize)groupGrid).BeginInit();
             bottomTable.SuspendLayout();
             SuspendLayout();
@@ -56,23 +69,27 @@ namespace OpenNest.Forms
             layoutTable.ColumnCount = 1;
             layoutTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle(System.Windows.Forms.SizeType.Percent, 100F));
             layoutTable.Controls.Add(setLabel, 0, 0);
-            layoutTable.Controls.Add(optionsTable, 0, 1);
-            layoutTable.Controls.Add(groupGrid, 0, 2);
-            layoutTable.Controls.Add(skippedLabel, 0, 3);
-            layoutTable.Controls.Add(bottomTable, 0, 4);
-            layoutTable.Controls.Add(statusLabel, 0, 5);
+            layoutTable.Controls.Add(addSetTable, 0, 1);
+            layoutTable.Controls.Add(setGrid, 0, 2);
+            layoutTable.Controls.Add(optionsTable, 0, 3);
+            layoutTable.Controls.Add(groupGrid, 0, 4);
+            layoutTable.Controls.Add(skippedLabel, 0, 5);
+            layoutTable.Controls.Add(bottomTable, 0, 6);
+            layoutTable.Controls.Add(statusLabel, 0, 7);
             layoutTable.Dock = System.Windows.Forms.DockStyle.Fill;
             layoutTable.Location = new System.Drawing.Point(0, 0);
             layoutTable.Name = "layoutTable";
             layoutTable.Padding = new System.Windows.Forms.Padding(8);
-            layoutTable.RowCount = 6;
+            layoutTable.RowCount = 8;
             layoutTable.RowStyles.Add(new System.Windows.Forms.RowStyle());
             layoutTable.RowStyles.Add(new System.Windows.Forms.RowStyle());
+            layoutTable.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Absolute, 130F));
+            layoutTable.RowStyles.Add(new System.Windows.Forms.RowStyle());
             layoutTable.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 100F));
             layoutTable.RowStyles.Add(new System.Windows.Forms.RowStyle());
             layoutTable.RowStyles.Add(new System.Windows.Forms.RowStyle());
             layoutTable.RowStyles.Add(new System.Windows.Forms.RowStyle());
-            layoutTable.Size = new System.Drawing.Size(944, 521);
+            layoutTable.Size = new System.Drawing.Size(1104, 661);
             layoutTable.TabIndex = 0;
             //
             // setLabel
@@ -84,55 +101,136 @@ namespace OpenNest.Forms
             setLabel.Name = "setLabel";
             setLabel.Size = new System.Drawing.Size(100, 20);
             setLabel.TabIndex = 0;
+            setLabel.Text = "Sets to release";
+            //
+            // addSetTable
+            //
+            addSetTable.AutoSize = true;
+            addSetTable.ColumnCount = 4;
+            addSetTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle());
+            addSetTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle(System.Windows.Forms.SizeType.Absolute, 360F));
+            addSetTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle());
+            addSetTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle(System.Windows.Forms.SizeType.Percent, 100F));
+            addSetTable.Controls.Add(addSetLabel, 0, 0);
+            addSetTable.Controls.Add(addSetCombo, 1, 0);
+            addSetTable.Controls.Add(addSetButton, 2, 0);
+            addSetTable.Controls.Add(removeSetButton, 3, 0);
+            addSetTable.Dock = System.Windows.Forms.DockStyle.Fill;
+            addSetTable.Margin = new System.Windows.Forms.Padding(0, 0, 0, 3);
+            addSetTable.Name = "addSetTable";
+            addSetTable.RowCount = 1;
+            addSetTable.RowStyles.Add(new System.Windows.Forms.RowStyle());
+            addSetTable.TabIndex = 1;
+            //
+            // addSetLabel
+            //
+            addSetLabel.Anchor = System.Windows.Forms.AnchorStyles.Left;
+            addSetLabel.AutoSize = true;
+            addSetLabel.Name = "addSetLabel";
+            addSetLabel.TabIndex = 0;
+            addSetLabel.Text = "Add a set:";
+            //
+            // addSetCombo
+            //
+            addSetCombo.Dock = System.Windows.Forms.DockStyle.Fill;
+            addSetCombo.Name = "addSetCombo";
+            addSetCombo.TabIndex = 1;
+            addSetCombo.TextUpdate += AddSetCombo_TextUpdate;
+            addSetCombo.KeyDown += AddSetCombo_KeyDown;
+            //
+            // addSetButton
+            //
+            addSetButton.AutoSize = true;
+            addSetButton.Name = "addSetButton";
+            addSetButton.TabIndex = 2;
+            addSetButton.Text = "Add";
+            addSetButton.UseVisualStyleBackColor = true;
+            addSetButton.Click += AddSetButton_Click;
+            //
+            // removeSetButton
+            //
+            removeSetButton.Anchor = System.Windows.Forms.AnchorStyles.Left;
+            removeSetButton.AutoSize = true;
+            removeSetButton.Name = "removeSetButton";
+            removeSetButton.TabIndex = 3;
+            removeSetButton.Text = "Remove Set";
+            removeSetButton.UseVisualStyleBackColor = true;
+            removeSetButton.Click += RemoveSetButton_Click;
+            //
+            // setGrid
+            //
+            setGrid.AllowUserToAddRows = false;
+            setGrid.AllowUserToDeleteRows = false;
+            setGrid.Columns.AddRange(new System.Windows.Forms.DataGridViewColumn[] { setNameColumn, setCustomerColumn, setRevisionColumn, kitsColumn });
+            setGrid.Dock = System.Windows.Forms.DockStyle.Fill;
+            setGrid.Margin = new System.Windows.Forms.Padding(3, 3, 3, 6);
+            setGrid.MultiSelect = false;
+            setGrid.Name = "setGrid";
+            setGrid.RowHeadersVisible = false;
+            setGrid.SelectionMode = System.Windows.Forms.DataGridViewSelectionMode.FullRowSelect;
+            setGrid.StandardTab = true;
+            setGrid.TabIndex = 2;
+            setGrid.CellValidating += SetGrid_CellValidating;
+            setGrid.CellValueChanged += SetGrid_CellValueChanged;
+            setGrid.SelectionChanged += SetGrid_SelectionChanged;
+            //
+            // setNameColumn
+            //
+            setNameColumn.AutoSizeMode = System.Windows.Forms.DataGridViewAutoSizeColumnMode.Fill;
+            setNameColumn.HeaderText = "Set";
+            setNameColumn.Name = "setNameColumn";
+            setNameColumn.ReadOnly = true;
+            setNameColumn.SortMode = System.Windows.Forms.DataGridViewColumnSortMode.NotSortable;
+            //
+            // setCustomerColumn
+            //
+            setCustomerColumn.HeaderText = "Customer";
+            setCustomerColumn.Name = "setCustomerColumn";
+            setCustomerColumn.ReadOnly = true;
+            setCustomerColumn.SortMode = System.Windows.Forms.DataGridViewColumnSortMode.NotSortable;
+            setCustomerColumn.Width = 200;
+            //
+            // setRevisionColumn
+            //
+            setRevisionColumn.DefaultCellStyle = rightAligned;
+            setRevisionColumn.HeaderText = "Revision";
+            setRevisionColumn.Name = "setRevisionColumn";
+            setRevisionColumn.ReadOnly = true;
+            setRevisionColumn.SortMode = System.Windows.Forms.DataGridViewColumnSortMode.NotSortable;
+            setRevisionColumn.Width = 75;
+            //
+            // kitsColumn
+            //
+            kitsColumn.DefaultCellStyle = rightAligned;
+            kitsColumn.HeaderText = "Kits";
+            kitsColumn.Name = "kitsColumn";
+            kitsColumn.SortMode = System.Windows.Forms.DataGridViewColumnSortMode.NotSortable;
+            kitsColumn.ToolTipText = "How many of this set to release: every quantity in the set is multiplied by it.";
+            kitsColumn.Width = 70;
             //
             // optionsTable
             //
             optionsTable.AutoSize = true;
-            optionsTable.ColumnCount = 5;
-            optionsTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle());
-            optionsTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle());
+            optionsTable.ColumnCount = 3;
             optionsTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle());
             optionsTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle());
             optionsTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle(System.Windows.Forms.SizeType.Percent, 100F));
-            optionsTable.Controls.Add(multiplierLabel, 0, 0);
-            optionsTable.Controls.Add(multiplierBox, 1, 0);
-            optionsTable.Controls.Add(includeArchivedCheckBox, 2, 0);
-            optionsTable.Controls.Add(notesLabel, 3, 0);
-            optionsTable.Controls.Add(notesBox, 4, 0);
+            optionsTable.Controls.Add(includeArchivedCheckBox, 0, 0);
+            optionsTable.Controls.Add(notesLabel, 1, 0);
+            optionsTable.Controls.Add(notesBox, 2, 0);
             optionsTable.Dock = System.Windows.Forms.DockStyle.Fill;
             optionsTable.Margin = new System.Windows.Forms.Padding(0, 0, 0, 6);
             optionsTable.Name = "optionsTable";
             optionsTable.RowCount = 1;
             optionsTable.RowStyles.Add(new System.Windows.Forms.RowStyle());
-            optionsTable.TabIndex = 1;
-            //
-            // multiplierLabel
-            //
-            multiplierLabel.Anchor = System.Windows.Forms.AnchorStyles.Left;
-            multiplierLabel.AutoSize = true;
-            multiplierLabel.Name = "multiplierLabel";
-            multiplierLabel.TabIndex = 0;
-            multiplierLabel.Text = "Kits (multiplier):";
-            //
-            // multiplierBox
-            //
-            multiplierBox.Anchor = System.Windows.Forms.AnchorStyles.Left;
-            multiplierBox.Maximum = new decimal(new int[] { 1000, 0, 0, 0 });
-            multiplierBox.Minimum = new decimal(new int[] { 1, 0, 0, 0 });
-            multiplierBox.Name = "multiplierBox";
-            multiplierBox.Size = new System.Drawing.Size(70, 25);
-            multiplierBox.TabIndex = 1;
-            multiplierBox.TextAlign = System.Windows.Forms.HorizontalAlignment.Right;
-            multiplierBox.Value = new decimal(new int[] { 1, 0, 0, 0 });
-            multiplierBox.ValueChanged += Options_Changed;
+            optionsTable.TabIndex = 3;
             //
             // includeArchivedCheckBox
             //
             includeArchivedCheckBox.Anchor = System.Windows.Forms.AnchorStyles.Left;
             includeArchivedCheckBox.AutoSize = true;
-            includeArchivedCheckBox.Margin = new System.Windows.Forms.Padding(12, 3, 3, 3);
             includeArchivedCheckBox.Name = "includeArchivedCheckBox";
-            includeArchivedCheckBox.TabIndex = 2;
+            includeArchivedCheckBox.TabIndex = 0;
             includeArchivedCheckBox.Text = "Include archived drawings";
             includeArchivedCheckBox.UseVisualStyleBackColor = true;
             includeArchivedCheckBox.CheckedChanged += Options_Changed;
@@ -143,7 +241,7 @@ namespace OpenNest.Forms
             notesLabel.AutoSize = true;
             notesLabel.Margin = new System.Windows.Forms.Padding(12, 0, 3, 0);
             notesLabel.Name = "notesLabel";
-            notesLabel.TabIndex = 3;
+            notesLabel.TabIndex = 1;
             notesLabel.Text = "Release notes:";
             //
             // notesBox
@@ -151,22 +249,24 @@ namespace OpenNest.Forms
             notesBox.Dock = System.Windows.Forms.DockStyle.Fill;
             notesBox.MaxLength = 4000;
             notesBox.Name = "notesBox";
-            notesBox.TabIndex = 4;
+            notesBox.TabIndex = 2;
             //
             // groupGrid
             //
             groupGrid.AllowUserToAddRows = false;
             groupGrid.AllowUserToDeleteRows = false;
-            groupGrid.Columns.AddRange(new System.Windows.Forms.DataGridViewColumn[] { includeColumn, materialColumn, gradeColumn, thicknessColumn, unitsColumn, cutTypeColumn, drawingsColumn, partsColumn, statusColumn });
+            groupGrid.Columns.AddRange(new System.Windows.Forms.DataGridViewColumn[] { includeColumn, materialColumn, gradeColumn, thicknessColumn, unitsColumn, cutTypeColumn, drawingsColumn, partsColumn, targetColumn, statusColumn });
             groupGrid.Dock = System.Windows.Forms.DockStyle.Fill;
+            groupGrid.EditMode = System.Windows.Forms.DataGridViewEditMode.EditOnEnter;
             groupGrid.MultiSelect = false;
             groupGrid.Name = "groupGrid";
             groupGrid.RowHeadersVisible = false;
             groupGrid.SelectionMode = System.Windows.Forms.DataGridViewSelectionMode.FullRowSelect;
             groupGrid.StandardTab = true;
-            groupGrid.TabIndex = 2;
+            groupGrid.TabIndex = 4;
             groupGrid.CellValueChanged += GroupGrid_CellValueChanged;
             groupGrid.CurrentCellDirtyStateChanged += GroupGrid_CurrentCellDirtyStateChanged;
+            groupGrid.DataError += GroupGrid_DataError;
             //
             // includeColumn
             //
@@ -234,6 +334,16 @@ namespace OpenNest.Forms
             partsColumn.SortMode = System.Windows.Forms.DataGridViewColumnSortMode.NotSortable;
             partsColumn.Width = 65;
             //
+            // targetColumn
+            //
+            targetColumn.DisplayStyle = System.Windows.Forms.DataGridViewComboBoxDisplayStyle.DropDownButton;
+            targetColumn.FlatStyle = System.Windows.Forms.FlatStyle.Flat;
+            targetColumn.HeaderText = "Nest";
+            targetColumn.Name = "targetColumn";
+            targetColumn.SortMode = System.Windows.Forms.DataGridViewColumnSortMode.NotSortable;
+            targetColumn.ToolTipText = "Make a new Draft nest, or merge into a Draft nest of the same material and renest it.";
+            targetColumn.Width = 260;
+            //
             // statusColumn
             //
             statusColumn.AutoSizeMode = System.Windows.Forms.DataGridViewAutoSizeColumnMode.Fill;
@@ -247,9 +357,9 @@ namespace OpenNest.Forms
             skippedLabel.AutoSize = true;
             skippedLabel.ForeColor = System.Drawing.SystemColors.GrayText;
             skippedLabel.Margin = new System.Windows.Forms.Padding(3, 6, 3, 0);
-            skippedLabel.MaximumSize = new System.Drawing.Size(920, 0);
+            skippedLabel.MaximumSize = new System.Drawing.Size(1080, 0);
             skippedLabel.Name = "skippedLabel";
-            skippedLabel.TabIndex = 3;
+            skippedLabel.TabIndex = 5;
             skippedLabel.Visible = false;
             //
             // bottomTable
@@ -267,7 +377,7 @@ namespace OpenNest.Forms
             bottomTable.Name = "bottomTable";
             bottomTable.RowCount = 1;
             bottomTable.RowStyles.Add(new System.Windows.Forms.RowStyle());
-            bottomTable.TabIndex = 4;
+            bottomTable.TabIndex = 6;
             //
             // summaryLabel
             //
@@ -302,27 +412,34 @@ namespace OpenNest.Forms
             statusLabel.Margin = new System.Windows.Forms.Padding(3, 6, 3, 0);
             statusLabel.Name = "statusLabel";
             statusLabel.Size = new System.Drawing.Size(100, 20);
-            statusLabel.TabIndex = 5;
+            statusLabel.TabIndex = 7;
+            //
+            // searchTimer
+            //
+            searchTimer.Interval = 250;
+            searchTimer.Tick += SearchTimer_Tick;
             //
             // ReleaseSetForm
             //
             AutoScaleMode = System.Windows.Forms.AutoScaleMode.None;
-            ClientSize = new System.Drawing.Size(944, 521);
+            ClientSize = new System.Drawing.Size(1104, 661);
             Controls.Add(layoutTable);
             Font = new System.Drawing.Font("Segoe UI", 9.75F);
             MinimizeBox = false;
-            MinimumSize = new System.Drawing.Size(760, 400);
+            MinimumSize = new System.Drawing.Size(860, 520);
             Name = "ReleaseSetForm";
             ShowIcon = false;
             ShowInTaskbar = false;
             StartPosition = System.Windows.Forms.FormStartPosition.CenterParent;
-            Text = "Release Drawing Set";
+            Text = "Release Drawing Sets";
             FormClosing += ReleaseSetForm_FormClosing;
             layoutTable.ResumeLayout(false);
             layoutTable.PerformLayout();
+            addSetTable.ResumeLayout(false);
+            addSetTable.PerformLayout();
+            ((System.ComponentModel.ISupportInitialize)setGrid).EndInit();
             optionsTable.ResumeLayout(false);
             optionsTable.PerformLayout();
-            ((System.ComponentModel.ISupportInitialize)multiplierBox).EndInit();
             ((System.ComponentModel.ISupportInitialize)groupGrid).EndInit();
             bottomTable.ResumeLayout(false);
             bottomTable.PerformLayout();
@@ -333,9 +450,17 @@ namespace OpenNest.Forms
 
         private System.Windows.Forms.TableLayoutPanel layoutTable;
         private System.Windows.Forms.Label setLabel;
+        private System.Windows.Forms.TableLayoutPanel addSetTable;
+        private System.Windows.Forms.Label addSetLabel;
+        private System.Windows.Forms.ComboBox addSetCombo;
+        private System.Windows.Forms.Button addSetButton;
+        private System.Windows.Forms.Button removeSetButton;
+        private System.Windows.Forms.DataGridView setGrid;
+        private System.Windows.Forms.DataGridViewTextBoxColumn setNameColumn;
+        private System.Windows.Forms.DataGridViewTextBoxColumn setCustomerColumn;
+        private System.Windows.Forms.DataGridViewTextBoxColumn setRevisionColumn;
+        private System.Windows.Forms.DataGridViewTextBoxColumn kitsColumn;
         private System.Windows.Forms.TableLayoutPanel optionsTable;
-        private System.Windows.Forms.Label multiplierLabel;
-        private System.Windows.Forms.NumericUpDown multiplierBox;
         private System.Windows.Forms.CheckBox includeArchivedCheckBox;
         private System.Windows.Forms.Label notesLabel;
         private System.Windows.Forms.TextBox notesBox;
@@ -348,6 +473,7 @@ namespace OpenNest.Forms
         private System.Windows.Forms.DataGridViewTextBoxColumn cutTypeColumn;
         private System.Windows.Forms.DataGridViewTextBoxColumn drawingsColumn;
         private System.Windows.Forms.DataGridViewTextBoxColumn partsColumn;
+        private System.Windows.Forms.DataGridViewComboBoxColumn targetColumn;
         private System.Windows.Forms.DataGridViewTextBoxColumn statusColumn;
         private System.Windows.Forms.Label skippedLabel;
         private System.Windows.Forms.TableLayoutPanel bottomTable;
@@ -355,5 +481,6 @@ namespace OpenNest.Forms
         private System.Windows.Forms.Button releaseButton;
         private System.Windows.Forms.Button closeButton;
         private System.Windows.Forms.Label statusLabel;
+        private System.Windows.Forms.Timer searchTimer;
     }
 }
diff --git a/OpenNest/Forms/ReleaseSetForm.cs b/OpenNest/Forms/ReleaseSetForm.cs
index 5ea6b290..945c05c0 100644
--- a/OpenNest/Forms/ReleaseSetForm.cs
+++ b/OpenNest/Forms/ReleaseSetForm.cs
@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
 using System.Linq;
+using System.Net.Http;
 using System.Threading;
 using System.Threading.Tasks;
 using System.Windows.Forms;
@@ -14,27 +15,36 @@ using OpenNest.IO;
 namespace OpenNest.Forms
 {
     /// <summary>
-    /// Drawing Sets &gt; Release: previews how a set splits into one nest per material group
-    /// (<see cref="SetReleasePlan"/>), with a kit multiplier, an archived-drawing toggle and a
-    /// tick per group, then makes those nests through <see cref="SetReleaseSession"/>: each is
-    /// uploaded as a Draft and opened in its own tab, and the release is recorded once every
+    /// Drawing Sets &gt; Release: the operator lists the sets to release, typed in or added from
+    /// the browser, each with a number of kits, and the dialog previews how they split into one
+    /// nest per material group (<see cref="SetReleasePlan"/>), with an archived-drawing toggle
+    /// and a tick per group. Each group makes a new Draft nest or merges into a Draft nest of
+    /// the same material, which is renested. <see cref="SetReleaseSession"/> then builds and
+    /// saves those nests, opens each in its own tab, and records the release once every
     /// chosen nest exists. The dialog shows every group's outcome; a release runs once per
     /// dialog.
     /// </summary>
     public partial class ReleaseSetForm : Form
     {
+        private const string NewNestChoice = "New Draft nest";
+
         private readonly IDrawingSetStore sets;
         private readonly IDrawingLibrary library;
         private readonly INestRepository nests;
         private readonly string serverUrl;
-        private readonly DrawingSetRecord set;
         private readonly Action<Nest, NestRecord> openNest;
         private readonly HashSet<string> excluded = new(StringComparer.Ordinal);
+        // The draft each group merges into, by group key, so the choice survives plan rebuilds.
+        private readonly Dictionary<string, NestRecord> targets = new(StringComparer.Ordinal);
+        // The drafts each group could merge into, by group key; absent while still loading.
+        private readonly Dictionary<string, IReadOnlyList<NestRecord>> drafts = new(StringComparer.Ordinal);
         private SetReleasePlan plan;
         private SetReleaseSession session;
         private CancellationTokenSource cancellation;
+        private CancellationTokenSource searchCancellation;
         private bool populating;
         private bool running;
+        private bool loadingDrafts;
 
         /// <summary>Shows a message and returns the operator's answer; replaced by tests.</summary>
         internal Func<string, MessageBoxButtons, MessageBoxIcon, DialogResult> ShowMessage { get; set; }
@@ -42,11 +52,17 @@ namespace OpenNest.Forms
         /// <summary>Makes the empty nest for a group, as File &gt; New would in its units; replaced by tests.</summary>
         internal Func<SetReleaseGroup, CancellationToken, Task<Nest>> CreateNest { get; set; }
 
+        /// <summary>
+        /// True when a server nest is open in a tab of this desktop. Such a draft is not merged
+        /// into: the tab could hold edits the merge would leave behind.
+        /// </summary>
+        public Func<Guid, bool> IsNestOpen { get; set; } = _ => false;
+
         /// <summary>The finished release, once one has run; otherwise null.</summary>
         public SetReleaseResult Result { get; private set; }
 
-        /// <param name="set">The set read with <see cref="IDrawingSetStore.GetAsync"/>, members joined.</param>
-        /// <param name="openNest">Opens a created nest in its own tab, bound to its server record.</param>
+        /// <param name="set">The first set to release, read with <see cref="IDrawingSetStore.GetAsync"/>, members joined.</param>
+        /// <param name="openNest">Opens a created or merged nest in its own tab, bound to its server record.</param>
         public ReleaseSetForm(IDrawingSetStore sets, IDrawingLibrary library, INestRepository nests, string serverUrl,
             DrawingSetRecord set, Action<Nest, NestRecord> openNest)
         {
@@ -55,47 +71,253 @@ namespace OpenNest.Forms
             this.library = library ?? throw new ArgumentNullException(nameof(library));
             this.nests = nests ?? throw new ArgumentNullException(nameof(nests));
             this.serverUrl = serverUrl ?? "";
-            this.set = set ?? throw new ArgumentNullException(nameof(set));
             this.openNest = openNest ?? throw new ArgumentNullException(nameof(openNest));
+            ArgumentNullException.ThrowIfNull(set);
             ShowMessage = (text, buttons, icon) => MessageBox.Show(this, text, Text, buttons, icon);
             CreateNest = (group, _) => NewNestFactory.CreateAsync(this, group.Units);
 
+            GridStyle.Apply(setGrid);
             GridStyle.Apply(groupGrid);
-            Text = $"Release '{set.Name}'";
-            setLabel.Text = string.IsNullOrWhiteSpace(set.Customer)
-                ? $"{set.Name} — revision {set.Revision}"
-                : $"{set.Name} ({set.Customer}) — revision {set.Revision}";
-            BuildPlan();
+            AddLine(set, 1);
         }
 
+        /// <summary>The sets listed, in order, with their kits.</summary>
+        internal IReadOnlyList<SetReleasePlanLine> Lines() =>
+            setGrid.Rows.Cast<DataGridViewRow>()
+                .Select(r => new SetReleasePlanLine((DrawingSetRecord)r.Tag, Kits(r)))
+                .ToList();
+
+        /// <summary>
+        /// Adds a set read from the server (members joined) with <paramref name="kits"/>; false,
+        /// with the reason shown, when it is archived or already listed.
+        /// </summary>
+        internal bool AddLine(DrawingSetRecord set, int kits)
+        {
+            ArgumentNullException.ThrowIfNull(set);
+            var listed = setGrid.Rows.Cast<DataGridViewRow>().FirstOrDefault(r => ((DrawingSetRecord)r.Tag).Id == set.Id);
+            if (listed != null)
+            {
+                listed.Selected = true;
+                statusLabel.Text = $"'{set.Name}' is already listed. Change its kits instead.";
+                return false;
+            }
+            if (set.Archived)
+            {
+                statusLabel.Text = $"'{set.Name}' is archived. Restore it before releasing it.";
+                return false;
+            }
+
+            var row = new DataGridViewRow { Tag = set };
+            row.CreateCells(setGrid, set.Name, set.Customer, set.Revision, kits.ToString(CultureInfo.CurrentCulture));
+            setGrid.Rows.Add(row);
+            statusLabel.Text = "";
+            BuildPlan();
+            return true;
+        }
+
+        private static int Kits(DataGridViewRow row) =>
+            int.TryParse(Convert.ToString(row.Cells["kitsColumn"].Value, CultureInfo.CurrentCulture), NumberStyles.Integer,
+                CultureInfo.CurrentCulture, out var kits) ? kits : 1;
+
         private void Options_Changed(object sender, EventArgs e)
         {
             if (!running && Result == null)
                 BuildPlan();
         }
 
-        // Commit a checkbox click at once so the summary follows the tick.
+        private void SetGrid_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)
+        {
+            if (e.ColumnIndex != kitsColumn.Index)
+                return;
+            var valid = int.TryParse(Convert.ToString(e.FormattedValue, CultureInfo.CurrentCulture), NumberStyles.Integer,
+                CultureInfo.CurrentCulture, out var kits) && kits >= 1 && kits <= SetReleaseRules.MaxQuantity;
+            setGrid.Rows[e.RowIndex].ErrorText = valid ? "" : $"Kits must be a whole number from 1 to {SetReleaseRules.MaxQuantity}.";
+            e.Cancel = !valid;
+        }
+
+        private void SetGrid_CellValueChanged(object sender, DataGridViewCellEventArgs e)
+        {
+            if (e.RowIndex >= 0 && e.ColumnIndex == kitsColumn.Index && !running && Result == null)
+                BuildPlan();
+        }
+
+        private void SetGrid_SelectionChanged(object sender, EventArgs e) => UpdateCommands();
+
+        private void RemoveSetButton_Click(object sender, EventArgs e)
+        {
+            if (setGrid.Rows.Count < 2 || setGrid.CurrentRow == null)
+                return;
+            setGrid.Rows.Remove(setGrid.CurrentRow);
+            BuildPlan();
+        }
+
+        // Type-ahead: the set list is queried once typing pauses.
+        private void AddSetCombo_TextUpdate(object sender, EventArgs e)
+        {
+            searchTimer.Stop();
+            searchTimer.Start();
+        }
+
+        private async void SearchTimer_Tick(object sender, EventArgs e)
+        {
+            searchTimer.Stop();
+            await SearchSetsAsync(addSetCombo.Text);
+        }
+
+        private async void AddSetCombo_KeyDown(object sender, KeyEventArgs e)
+        {
+            if (e.KeyCode != Keys.Enter)
+                return;
+            e.Handled = e.SuppressKeyPress = true;
+            await AddTypedSetAsync();
+        }
+
+        private async void AddSetButton_Click(object sender, EventArgs e) => await AddTypedSetAsync();
+
+        /// <summary>Lists active sets whose name, customer or notes contain <paramref name="text"/>.</summary>
+        internal async Task SearchSetsAsync(string text)
+        {
+            searchCancellation?.Cancel();
+            searchCancellation?.Dispose();
+            searchCancellation = new CancellationTokenSource();
+            var token = searchCancellation.Token;
+            DrawingSetPage page;
+            try
+            {
+                page = await sets.QueryAsync(new DrawingSetQuery { Search = text ?? "", Limit = 20, Sort = DrawingSetSortField.Name, Descending = false }, token);
+            }
+            catch (OperationCanceledException) when (token.IsCancellationRequested)
+            {
+                return;
+            }
+            catch (Exception ex) when (ex is IOException or HttpRequestException or TaskCanceledException or System.Text.Json.JsonException)
+            {
+                if (!IsDisposed)
+                    statusLabel.Text = $"Could not search the sets: {ex.Message}";
+                return;
+            }
+
+            if (IsDisposed || token.IsCancellationRequested)
+                return;
+            // Refilling the list resets the text, so the operator's typing is put back.
+            var typed = addSetCombo.Text;
+            var caret = addSetCombo.SelectionStart;
+            addSetCombo.BeginUpdate();
+            addSetCombo.Items.Clear();
+            foreach (var found in page.Items)
+                addSetCombo.Items.Add(new SetChoice(found));
+            addSetCombo.EndUpdate();
+            addSetCombo.Text = typed;
+            addSetCombo.SelectionStart = System.Math.Min(caret, typed.Length);
+            if (addSetCombo.Focused && page.Items.Count > 0)
+                addSetCombo.DroppedDown = true;
+        }
+
+        /// <summary>
+        /// Adds the set picked in the list, or the one active set whose name is exactly what was
+        /// typed, read with its members.
+        /// </summary>
+        internal async Task AddTypedSetAsync()
+        {
+            if (running || Result != null)
+                return;
+            var typed = (addSetCombo.Text ?? "").Trim();
+            try
+            {
+                Guid id;
+                if (addSetCombo.SelectedItem is SetChoice choice && choice.ToString() == addSetCombo.Text)
+                {
+                    id = choice.Set.Id;
+                }
+                else
+                {
+                    if (typed.Length == 0)
+                        return;
+                    var page = await sets.QueryAsync(new DrawingSetQuery { Search = typed, Limit = 50 });
+                    var exact = page.Items.Where(s => string.Equals(s.Name.Trim(), typed, StringComparison.OrdinalIgnoreCase)).ToList();
+                    if (exact.Count != 1)
+                    {
+                        statusLabel.Text = exact.Count == 0
+                            ? $"No active set is named '{typed}'. Pick one from the list."
+                            : $"{exact.Count} sets are named '{typed}'. Pick one from the list.";
+                        return;
+                    }
+                    id = exact[0].Id;
+                }
+
+                var read = await sets.GetAsync(id);
+                if (IsDisposed)
+                    return;
+                if (read == null)
+                {
+                    statusLabel.Text = "That set no longer exists on the server.";
+                    return;
+                }
+                if (AddLine(read, 1))
+                    addSetCombo.Text = "";
+            }
+            catch (Exception ex) when (ex is IOException or HttpRequestException or TaskCanceledException or System.Text.Json.JsonException)
+            {
+                if (!IsDisposed)
+                    statusLabel.Text = $"Could not read the set: {ex.Message}";
+            }
+        }
+
+        // Commit a checkbox click or a target choice at once so the summary follows it.
         private void GroupGrid_CurrentCellDirtyStateChanged(object sender, EventArgs e)
         {
-            if (groupGrid.IsCurrentCellDirty && groupGrid.CurrentCell?.OwningColumn == includeColumn)
+            if (groupGrid.IsCurrentCellDirty
+                && (groupGrid.CurrentCell?.OwningColumn == includeColumn || groupGrid.CurrentCell?.OwningColumn == targetColumn))
                 groupGrid.CommitEdit(DataGridViewDataErrorContexts.Commit);
         }
 
         private void GroupGrid_CellValueChanged(object sender, DataGridViewCellEventArgs e)
         {
-            if (populating || e.RowIndex < 0 || e.ColumnIndex != includeColumn.Index)
+            if (populating || e.RowIndex < 0)
                 return;
             var row = groupGrid.Rows[e.RowIndex];
-            if (row.Tag is SetReleaseGroup group)
+            if (row.Tag is not SetReleaseGroup group)
+                return;
+            if (e.ColumnIndex == includeColumn.Index)
             {
                 if (row.Cells[includeColumn.Index].Value is true)
                     excluded.Remove(group.Key);
                 else
                     excluded.Add(group.Key);
             }
+            else if (e.ColumnIndex == targetColumn.Index)
+            {
+                ChooseTarget(row, group, row.Cells[targetColumn.Index].Value as string);
+            }
             UpdateCommands();
         }
 
+        // A combo value that is not in a rebuilt list is reset rather than reported.
+        private void GroupGrid_DataError(object sender, DataGridViewDataErrorEventArgs e) => e.ThrowException = false;
+
+        /// <summary>Makes <paramref name="group"/> merge into the draft named by <paramref name="choice"/>, or a new nest.</summary>
+        internal void ChooseTarget(DataGridViewRow row, SetReleaseGroup group, string choice)
+        {
+            var draft = drafts.TryGetValue(group.Key, out var candidates)
+                ? candidates.FirstOrDefault(d => DraftChoice(d) == choice)
+                : null;
+            if (draft != null && IsNestOpen(draft.Id))
+            {
+                ShowMessage($"'{draft.Name}' is open in a tab here. Close it first, so no edits there are left behind by the merge.",
+                    MessageBoxButtons.OK, MessageBoxIcon.Information);
+                draft = null;
+            }
+
+            if (draft == null)
+                targets.Remove(group.Key);
+            else
+                targets[group.Key] = draft;
+            populating = true;
+            row.Cells[targetColumn.Index].Value = draft == null ? NewNestChoice : DraftChoice(draft);
+            row.Cells[statusColumn.Index].Value = GroupNote(group);
+            populating = false;
+        }
+
         private async void ReleaseButton_Click(object sender, EventArgs e)
         {
             if (Result is { Release: null, ReleaseError.Length: > 0 })
@@ -109,7 +331,7 @@ namespace OpenNest.Forms
             if (running)
             {
                 cancellation?.Cancel();
-                statusLabel.Text = "Stopping after the nest being uploaded...";
+                statusLabel.Text = "Stopping after the nest being saved...";
                 closeButton.Enabled = false;
                 return;
             }
@@ -123,39 +345,57 @@ namespace OpenNest.Forms
             if (!running)
                 return;
             e.Cancel = true;
-            cancellation?.Cancel();
+            CloseButton_Click(sender, e);
         }
 
         /// <summary>The groups ticked for release, in plan order.</summary>
         internal IReadOnlyList<SetReleaseGroup> ChosenGroups() =>
             plan.Groups.Where(g => g.CanRelease && !excluded.Contains(g.Key)).ToList();
 
+        /// <summary>The chosen groups that merge into a draft, with that draft.</summary>
+        internal IReadOnlyDictionary<SetReleaseGroup, NestRecord> ChosenMerges() =>
+            ChosenGroups().Where(g => targets.ContainsKey(g.Key)).ToDictionary(g => g, g => targets[g.Key]);
+
         /// <summary>
-        /// Confirms, then makes one Draft nest per ticked group, opens each in its own tab and
-        /// records the release. Every group's outcome is shown in the grid.
+        /// Confirms, then makes or merges one Draft nest per ticked group, opens each in its own
+        /// tab and records the release. Every group's outcome is shown in the grid.
         /// </summary>
         internal async Task ReleaseAsync()
         {
-            if (running || Result != null || !groupGrid.EndEdit())
+            if (running || Result != null || !setGrid.EndEdit() || !groupGrid.EndEdit())
                 return;
             var chosen = ChosenGroups();
             if (chosen.Count == 0)
                 return;
-            var multiplier = plan.Lines[0].Quantity;
-            if (ShowMessage($"Create {chosen.Count} Draft nest{(chosen.Count == 1 ? "" : "s")} from set '{set.Name}'"
-                    + (multiplier == 1 ? "" : $" ×{multiplier}") + "? Each opens in its own tab.",
-                    MessageBoxButtons.OKCancel, MessageBoxIcon.Question) != DialogResult.OK)
+            var merges = ChosenMerges();
+            if (merges.Values.FirstOrDefault(d => IsNestOpen(d.Id)) is { } open)
+            {
+                ShowMessage($"'{open.Name}' is open in a tab here. Close it, or choose a new nest for its group.",
+                    MessageBoxButtons.OK, MessageBoxIcon.Information);
+                return;
+            }
+
+            var lines = plan.Lines;
+            var setsText = lines.Count == 1
+                ? $"set '{lines[0].Set.Name}'" + (lines[0].Quantity == 1 ? "" : $" ×{lines[0].Quantity}")
+                : $"{lines.Count} sets";
+            var created = chosen.Count - merges.Count;
+            var text = $"Release {setsText} into {chosen.Count} Draft nest{(chosen.Count == 1 ? "" : "s")}";
+            if (merges.Count > 0)
+                text += $": {created} new and {merges.Count} merged into existing drafts. A merged draft loses its "
+                    + "current layout and is nested again; Undo Release restores it";
+            if (ShowMessage(text + ". Each opens in its own tab.", MessageBoxButtons.OKCancel, MessageBoxIcon.Question) != DialogResult.OK)
                 return;
 
             running = true;
             cancellation = new CancellationTokenSource();
             closeButton.Text = "Cancel";
             UpdateCommands();
-            session = new SetReleaseSession(sets, library, nests, serverUrl, ReadPackage, WriteNest, CreateNest);
+            session = new SetReleaseSession(sets, library, nests, serverUrl, ReadPackage, WriteNest, CreateNest, ReadNest);
             var progress = new Progress<SetReleaseProgress>(ShowProgress);
             try
             {
-                Result = await session.RunAsync(plan, chosen, Environment.UserName, notesBox.Text, progress, cancellation.Token);
+                Result = await session.RunAsync(plan, chosen, Environment.UserName, notesBox.Text, progress, cancellation.Token, merges);
             }
             finally
             {
@@ -167,14 +407,14 @@ namespace OpenNest.Forms
                 }
             }
 
-            foreach (var created in Result.Created)
-                openNest(created.Nest, created.Record);
+            foreach (var done in Result.Created)
+                openNest(done.Nest, done.Record);
             if (IsDisposed)
                 return;
             ShowOutcome();
         }
 
-        /// <summary>Posts the release again after every nest was created but recording it failed.</summary>
+        /// <summary>Posts the release again after every nest was saved but recording it failed.</summary>
         internal async Task RetryRecordAsync()
         {
             if (running || session == null || !session.HasPendingRelease)
@@ -187,7 +427,7 @@ namespace OpenNest.Forms
                 var release = await session.RetryReleaseAsync();
                 Result = Result.WithRelease(release);
             }
-            catch (Exception ex) when (ex is IOException || ex is System.Net.Http.HttpRequestException
+            catch (Exception ex) when (ex is IOException || ex is HttpRequestException
                 || ex is TaskCanceledException || ex is System.Text.Json.JsonException)
             {
                 if (!IsDisposed)
@@ -204,7 +444,8 @@ namespace OpenNest.Forms
 
         private void BuildPlan()
         {
-            plan = SetReleasePlan.Build(set, (int)multiplierBox.Value, includeArchivedCheckBox.Checked);
+            plan = SetReleasePlan.Build(Lines(), includeArchivedCheckBox.Checked);
+            Text = plan.Lines.Count == 1 ? $"Release '{plan.Lines[0].Set.Name}'" : $"Release {plan.Lines.Count} Drawing Sets";
             populating = true;
             groupGrid.Rows.Clear();
             foreach (var group in plan.Groups)
@@ -219,10 +460,12 @@ namespace OpenNest.Forms
                     group.IsUnassigned ? "" : group.CutType.ToString(),
                     group.Items.Count,
                     group.TotalQuantity,
-                    group.CanRelease ? string.Join(" ", group.Warnings) : group.Refusal);
+                    null,
+                    GroupNote(group));
                 // A refused group cannot be ticked.
                 row.Cells[includeColumn.Index].ReadOnly = !group.CanRelease;
                 groupGrid.Rows.Add(row);
+                FillTargets(row, group);
             }
             populating = false;
 
@@ -234,8 +477,82 @@ namespace OpenNest.Forms
                 + (skipped.Count > 5 ? $" and {skipped.Count - 5} more" : "")
                 + ". Tick Include archived drawings to release them.";
             UpdateCommands();
+            _ = LoadDraftsAsync();
         }
 
+        // The target list of one group: a new nest, then each draft it could merge into.
+        private void FillTargets(DataGridViewRow row, SetReleaseGroup group)
+        {
+            var cell = (DataGridViewComboBoxCell)row.Cells[targetColumn.Index];
+            cell.Items.Clear();
+            cell.Items.Add(NewNestChoice);
+            if (group.CanRelease && drafts.TryGetValue(group.Key, out var candidates))
+            {
+                foreach (var draft in candidates)
+                    cell.Items.Add(DraftChoice(draft));
+            }
+            if (targets.TryGetValue(group.Key, out var target) && !cell.Items.Contains(DraftChoice(target)))
+                targets.Remove(group.Key);
+            cell.Value = targets.TryGetValue(group.Key, out target) ? DraftChoice(target) : NewNestChoice;
+            cell.ReadOnly = !group.CanRelease;
+        }
+
+        /// <summary>Looks up, once per group, the Draft nests it could merge into, then fills the lists.</summary>
+        internal async Task LoadDraftsAsync()
+        {
+            if (loadingDrafts || plan == null)
+                return;
+            loadingDrafts = true;
+            try
+            {
+                while (plan.Groups.FirstOrDefault(g => g.CanRelease && !drafts.ContainsKey(g.Key)) is { } group)
+                {
+                    try
+                    {
+                        drafts[group.Key] = await SetReleasePlan.FindDraftsAsync(nests, group);
+                    }
+                    catch (Exception ex) when (ex is IOException or HttpRequestException or TaskCanceledException
+                        or System.Text.Json.JsonException or NotSupportedException)
+                    {
+                        drafts[group.Key] = Array.Empty<NestRecord>();
+                        if (!IsDisposed)
+                            statusLabel.Text = $"Could not list the draft nests to merge into: {ex.Message}";
+                    }
+                    if (IsDisposed)
+                        return;
+                }
+            }
+            finally
+            {
+                loadingDrafts = false;
+            }
+
+            if (IsDisposed || running || Result != null)
+                return;
+            populating = true;
+            foreach (DataGridViewRow row in groupGrid.Rows)
+            {
+                if (row.Tag is SetReleaseGroup group)
+                    FillTargets(row, group);
+            }
+            populating = false;
+        }
+
+        private string GroupNote(SetReleaseGroup group)
+        {
+            if (!group.CanRelease)
+                return group.Refusal;
+            var notes = group.Warnings.ToList();
+            if (targets.TryGetValue(group.Key, out var draft))
+                notes.Insert(0, $"Merging discards the layout of '{draft.Name}' ({draft.PlateCount} sheet"
+                    + $"{(draft.PlateCount == 1 ? "" : "s")}) and nests everything again; Undo Release restores it.");
+            return string.Join(" ", notes);
+        }
+
+        private static string DraftChoice(NestRecord draft) =>
+            $"Merge into {draft.Name} ({draft.PlateCount} sheet{(draft.PlateCount == 1 ? "" : "s")}, saved "
+            + $"{draft.SavedAt.ToLocalTime().ToString("g", CultureInfo.CurrentCulture)})";
+
         private void ShowProgress(SetReleaseProgress progress)
         {
             // Progress is posted, so a report can arrive after the run ended; the outcome wins.
@@ -244,7 +561,7 @@ namespace OpenNest.Forms
             statusLabel.Text = progress.Stage switch
             {
                 SetReleaseStage.Preparing => $"Preparing nest {progress.Index + 1} of {progress.Count}: {Describe(progress.Group)}...",
-                SetReleaseStage.Uploading => $"Uploading nest {progress.Index + 1} of {progress.Count}: {Describe(progress.Group)}...",
+                SetReleaseStage.Uploading => $"Saving nest {progress.Index + 1} of {progress.Count}: {Describe(progress.Group)}...",
                 _ => "Recording the release...",
             };
         }
@@ -256,28 +573,29 @@ namespace OpenNest.Forms
                 var outcome = Result.Groups.FirstOrDefault(g => ReferenceEquals(g.Group, row.Tag));
                 if (outcome == null)
                     continue;
+                var notes = outcome.Warnings.Count == 0 ? "" : " — " + string.Join(" ", outcome.Warnings);
                 row.Cells[statusColumn.Index].Value = outcome.Outcome switch
                 {
-                    SetReleaseGroupOutcome.Created => $"Created {outcome.Record!.Name}"
-                        + (outcome.Warnings.Count == 0 ? "" : " — " + string.Join(" ", outcome.Warnings)),
+                    SetReleaseGroupOutcome.Created when outcome.MergedInto != null => $"Merged into {outcome.Record!.Name}" + notes,
+                    SetReleaseGroupOutcome.Created => $"Created {outcome.Record!.Name}" + notes,
                     SetReleaseGroupOutcome.Refused => "Refused: " + outcome.Error,
                     SetReleaseGroupOutcome.Failed => "Failed: " + outcome.Error,
                     _ => "Not started",
                 };
             }
 
-            var created = Result.Created.Count;
-            var nestsText = $"{created} nest{(created == 1 ? "" : "s")}";
+            var done = Result.Created.Count;
+            var nestsText = $"{done} nest{(done == 1 ? "" : "s")}";
             if (Result.Release != null)
-                statusLabel.Text = $"Released: {nestsText} created and opened, and the release recorded.";
+                statusLabel.Text = $"Released: {nestsText} saved and opened, and the release recorded.";
             else if (Result.ReleaseError.Length > 0)
                 statusLabel.Text = Result.ReleaseError + " Choose Record Release to try again.";
             else if (Result.Canceled)
-                statusLabel.Text = $"Canceled: {nestsText} created; no release recorded.";
+                statusLabel.Text = $"Canceled: {nestsText} saved; no release recorded.";
             else
-                statusLabel.Text = created == 0
-                    ? "Nothing was created. See the Status column."
-                    : $"Stopped: {nestsText} created; no release recorded. See the Status column.";
+                statusLabel.Text = done == 0
+                    ? "Nothing was saved. See the Status column."
+                    : $"Stopped: {nestsText} saved; no release recorded. See the Status column.";
             UpdateCommands();
         }
 
@@ -285,24 +603,35 @@ namespace OpenNest.Forms
         {
             var chosen = plan == null ? Array.Empty<SetReleaseGroup>() : ChosenGroups();
             var editable = !running && Result == null;
-            multiplierBox.Enabled = editable;
+            setGrid.ReadOnly = !editable;
+            addSetCombo.Enabled = editable;
+            addSetButton.Enabled = editable;
+            removeSetButton.Enabled = editable && setGrid.Rows.Count > 1 && setGrid.CurrentRow != null;
             includeArchivedCheckBox.Enabled = editable;
             notesBox.ReadOnly = !editable;
             includeColumn.ReadOnly = !editable;
+            targetColumn.ReadOnly = !editable;
             if (editable)
             {
                 foreach (DataGridViewRow row in groupGrid.Rows)
-                    row.Cells[includeColumn.Index].ReadOnly = row.Tag is SetReleaseGroup { CanRelease: false };
+                {
+                    var refused = row.Tag is SetReleaseGroup { CanRelease: false };
+                    row.Cells[includeColumn.Index].ReadOnly = refused;
+                    row.Cells[targetColumn.Index].ReadOnly = refused;
+                }
             }
 
             var retry = Result is { Release: null, ReleaseError.Length: > 0 };
             releaseButton.Text = retry ? "Record Release" : "Release";
             releaseButton.Enabled = !running && (retry || (editable && chosen.Count > 0));
             var parts = chosen.Sum(g => (long)g.TotalQuantity);
+            var merged = chosen.Count(g => targets.ContainsKey(g.Key));
             summaryLabel.Text = plan == null || plan.Groups.Count == 0
-                ? "This set has nothing to release."
+                ? "These sets have nothing to release."
                 : $"{chosen.Count} of {plan.Groups.Count} group{(plan.Groups.Count == 1 ? "" : "s")} chosen: "
-                    + $"{chosen.Count} Draft nest{(chosen.Count == 1 ? "" : "s")}, {parts:N0} part{(parts == 1 ? "" : "s")}";
+                    + $"{chosen.Count - merged} new Draft nest{(chosen.Count - merged == 1 ? "" : "s")}"
+                    + (merged == 0 ? "" : $", {merged} merge{(merged == 1 ? "" : "s")}")
+                    + $", {parts:N0} part{(parts == 1 ? "" : "s")}";
         }
 
         private static string Describe(SetReleaseGroup group) =>
@@ -319,11 +648,24 @@ namespace OpenNest.Forms
             return new LibraryPackage(bytes, contents.Drawing, contents.Units, contents.Warnings);
         }
 
+        private static Nest ReadNest(byte[] bytes)
+        {
+            using var stream = new MemoryStream(bytes, writable: false);
+            return new NestReader(stream) { BestFitStore = BestFitCacheStore.Shared }.Read();
+        }
+
         private static byte[] WriteNest(Nest nest)
         {
             using var stream = new MemoryStream();
             new NestWriter(nest) { BestFitStore = BestFitCacheStore.Shared }.Write(stream);
             return stream.ToArray();
         }
+
+        /// <summary>A set in the type-ahead list, shown by name and customer.</summary>
+        private sealed record SetChoice(DrawingSetRecord Set)
+        {
+            public override string ToString() =>
+                string.IsNullOrWhiteSpace(Set.Customer) ? Set.Name : $"{Set.Name} ({Set.Customer})";
+        }
     }
 }
diff --git a/OpenNest/Forms/SetReleasesForm.Designer.cs b/OpenNest/Forms/SetReleasesForm.Designer.cs
index 33cae613..76a11af4 100644
--- a/OpenNest/Forms/SetReleasesForm.Designer.cs
+++ b/OpenNest/Forms/SetReleasesForm.Designer.cs
@@ -34,10 +34,12 @@ namespace OpenNest.Forms
             statusColumn = new System.Windows.Forms.DataGridViewTextBoxColumn();
             nestCustomerColumn = new System.Windows.Forms.DataGridViewTextBoxColumn();
             modifiedColumn = new System.Windows.Forms.DataGridViewTextBoxColumn();
+            changeColumn = new System.Windows.Forms.DataGridViewTextBoxColumn();
             bottomTable = new System.Windows.Forms.TableLayoutPanel();
             previousButton = new System.Windows.Forms.Button();
             nextButton = new System.Windows.Forms.Button();
             summaryLabel = new System.Windows.Forms.Label();
+            undoButton = new System.Windows.Forms.Button();
             closeButton = new System.Windows.Forms.Button();
             layoutTable.SuspendLayout();
             ((System.ComponentModel.ISupportInitialize)releaseGrid).BeginInit();
@@ -146,7 +148,7 @@ namespace OpenNest.Forms
             //
             nestGrid.AllowUserToAddRows = false;
             nestGrid.AllowUserToDeleteRows = false;
-            nestGrid.Columns.AddRange(new System.Windows.Forms.DataGridViewColumn[] { nestNameColumn, groupColumn, statusColumn, nestCustomerColumn, modifiedColumn });
+            nestGrid.Columns.AddRange(new System.Windows.Forms.DataGridViewColumn[] { nestNameColumn, groupColumn, changeColumn, statusColumn, nestCustomerColumn, modifiedColumn });
             nestGrid.Dock = System.Windows.Forms.DockStyle.Fill;
             nestGrid.MultiSelect = false;
             nestGrid.Name = "nestGrid";
@@ -170,6 +172,14 @@ namespace OpenNest.Forms
             groupColumn.SortMode = System.Windows.Forms.DataGridViewColumnSortMode.NotSortable;
             groupColumn.Width = 260;
             //
+            // changeColumn
+            //
+            changeColumn.HeaderText = "Release did";
+            changeColumn.Name = "changeColumn";
+            changeColumn.SortMode = System.Windows.Forms.DataGridViewColumnSortMode.NotSortable;
+            changeColumn.ToolTipText = "Whether the release created the nest or merged into it, and what undoing it did.";
+            changeColumn.Width = 190;
+            //
             // statusColumn
             //
             statusColumn.HeaderText = "Status";
@@ -194,15 +204,17 @@ namespace OpenNest.Forms
             // bottomTable
             //
             bottomTable.AutoSize = true;
-            bottomTable.ColumnCount = 4;
+            bottomTable.ColumnCount = 5;
             bottomTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle());
             bottomTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle());
             bottomTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle(System.Windows.Forms.SizeType.Percent, 100F));
             bottomTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle());
+            bottomTable.ColumnStyles.Add(new System.Windows.Forms.ColumnStyle());
             bottomTable.Controls.Add(previousButton, 0, 0);
             bottomTable.Controls.Add(nextButton, 1, 0);
             bottomTable.Controls.Add(summaryLabel, 2, 0);
-            bottomTable.Controls.Add(closeButton, 3, 0);
+            bottomTable.Controls.Add(undoButton, 3, 0);
+            bottomTable.Controls.Add(closeButton, 4, 0);
             bottomTable.Dock = System.Windows.Forms.DockStyle.Fill;
             bottomTable.Margin = new System.Windows.Forms.Padding(0, 6, 0, 0);
             bottomTable.Name = "bottomTable";
@@ -237,12 +249,22 @@ namespace OpenNest.Forms
             summaryLabel.Name = "summaryLabel";
             summaryLabel.TabIndex = 2;
             //
+            // undoButton
+            //
+            undoButton.AutoSize = true;
+            undoButton.Enabled = false;
+            undoButton.Name = "undoButton";
+            undoButton.TabIndex = 3;
+            undoButton.Text = "Undo Release...";
+            undoButton.UseVisualStyleBackColor = true;
+            undoButton.Click += UndoButton_Click;
+            //
             // closeButton
             //
             closeButton.AutoSize = true;
             closeButton.DialogResult = System.Windows.Forms.DialogResult.Cancel;
             closeButton.Name = "closeButton";
-            closeButton.TabIndex = 3;
+            closeButton.TabIndex = 4;
             closeButton.Text = "Close";
             closeButton.UseVisualStyleBackColor = true;
             //
@@ -250,7 +272,7 @@ namespace OpenNest.Forms
             //
             AutoScaleMode = System.Windows.Forms.AutoScaleMode.None;
             CancelButton = closeButton;
-            ClientSize = new System.Drawing.Size(824, 541);
+            ClientSize = new System.Drawing.Size(1004, 541);
             Controls.Add(layoutTable);
             Font = new System.Drawing.Font("Segoe UI", 9.75F);
             MinimizeBox = false;
@@ -286,6 +308,7 @@ namespace OpenNest.Forms
         private System.Windows.Forms.DataGridView nestGrid;
         private System.Windows.Forms.DataGridViewTextBoxColumn nestNameColumn;
         private System.Windows.Forms.DataGridViewTextBoxColumn groupColumn;
+        private System.Windows.Forms.DataGridViewTextBoxColumn changeColumn;
         private System.Windows.Forms.DataGridViewTextBoxColumn statusColumn;
         private System.Windows.Forms.DataGridViewTextBoxColumn nestCustomerColumn;
         private System.Windows.Forms.DataGridViewTextBoxColumn modifiedColumn;
@@ -293,6 +316,7 @@ namespace OpenNest.Forms
         private System.Windows.Forms.Button previousButton;
         private System.Windows.Forms.Button nextButton;
         private System.Windows.Forms.Label summaryLabel;
+        private System.Windows.Forms.Button undoButton;
         private System.Windows.Forms.Button closeButton;
     }
 }
diff --git a/OpenNest/Forms/SetReleasesForm.cs b/OpenNest/Forms/SetReleasesForm.cs
index c23f2a42..96474d28 100644
--- a/OpenNest/Forms/SetReleasesForm.cs
+++ b/OpenNest/Forms/SetReleasesForm.cs
@@ -11,9 +11,12 @@ using OpenNest.Data;
 namespace OpenNest.Forms
 {
     /// <summary>
-    /// Drawing Sets &gt; Releases: one set's releases, newest first, a bounded page at a time,
-    /// each with its progress ("2 of 3 cut"), and the nests of the selected release with their
-    /// current status, or Deleted. The server joins every nest's current metadata on each read.
+    /// Drawing Sets &gt; Releases: the releases that include one set, newest first, a bounded
+    /// page at a time, each with its progress ("2 of 3 cut"), and the nests of the selected
+    /// release with what the release did to each and their current status, or Deleted. The
+    /// server joins every nest's current metadata on each read. Undo Release deletes the nests
+    /// a release created and restores the drafts it merged into, all or nothing; nests changed
+    /// since can be left as they are.
     /// </summary>
     public partial class SetReleasesForm : Form
     {
@@ -24,6 +27,10 @@ namespace OpenNest.Forms
         private SetReleasePage page;
         private int offset;
         private int pageRequest;
+        private bool undoing;
+
+        /// <summary>Shows a message and returns the operator's answer; replaced by tests.</summary>
+        internal Func<string, MessageBoxButtons, MessageBoxIcon, DialogResult> ShowMessage { get; set; }
 
         public SetReleasesForm(IDrawingSetStore sets, DrawingSetRecord set)
         {
@@ -33,6 +40,7 @@ namespace OpenNest.Forms
             GridStyle.Apply(releaseGrid);
             GridStyle.Apply(nestGrid);
             Text = $"Releases of '{set.Name}'";
+            ShowMessage = (text, buttons, icon) => MessageBox.Show(this, text, Text, buttons, icon);
         }
 
         private async void SetReleasesForm_Shown(object sender, EventArgs e) => await LoadPageAsync(0);
@@ -42,8 +50,72 @@ namespace OpenNest.Forms
 
         private async void NextButton_Click(object sender, EventArgs e) => await LoadPageAsync(offset + PageSize);
 
-        private void ReleaseGrid_CurrentCellChanged(object sender, EventArgs e) =>
+        private void ReleaseGrid_CurrentCellChanged(object sender, EventArgs e)
+        {
             ShowNests(releaseGrid.CurrentRow?.Tag as SetReleaseRecord);
+            UpdateUndo();
+        }
+
+        private async void UndoButton_Click(object sender, EventArgs e) => await UndoSelectedAsync();
+
+        private SetReleaseRecord SelectedRelease => releaseGrid.CurrentRow?.Tag as SetReleaseRecord;
+
+        private void UpdateUndo() => undoButton.Enabled = !undoing && SelectedRelease is { IsUndone: false };
+
+        /// <summary>
+        /// Confirms, then undoes the selected release. When nests changed since it, lists them and
+        /// offers to undo the others, leaving those as they are.
+        /// </summary>
+        internal async Task UndoSelectedAsync()
+        {
+            if (undoing || SelectedRelease is not { IsUndone: false } release)
+                return;
+            var created = release.Nests.Count(n => n.Kind == SetReleaseNestKind.Created);
+            var merged = release.Nests.Count - created;
+            var question = "Undo this release?"
+                + (created == 0 ? "" : $"\n\n{created} nest{(created == 1 ? " it created is" : "s it created are")} deleted (they can be recovered).")
+                + (merged == 0 ? "" : $"\n\n{merged} draft{(merged == 1 ? " it merged into goes" : "s it merged into go")} back to how {(merged == 1 ? "it was" : "they were")} before.");
+            if (ShowMessage(question, MessageBoxButtons.OKCancel, MessageBoxIcon.Question) != DialogResult.OK)
+                return;
+
+            undoing = true;
+            UpdateUndo();
+            try
+            {
+                var request = new SetReleaseUndoRequest { UndoneBy = Environment.UserName };
+                try
+                {
+                    await sets.UndoReleaseAsync(release.Id, request);
+                }
+                catch (SetReleaseUndoConflictException conflict) when (conflict.Conflict.Reason == SetReleaseUndoRefusal.NestsChanged
+                    && conflict.Conflict.ChangedNests.Count < release.Nests.Count)
+                {
+                    if (IsDisposed || ShowMessage(SetReleaseText.UndoRefusal(conflict.Conflict) + "\n\nUndo the others now?",
+                            MessageBoxButtons.YesNo, MessageBoxIcon.Warning) != DialogResult.Yes)
+                        return;
+                    request.SkipNests = conflict.Conflict.ChangedNests.Select(n => n.Id).ToList();
+                    await sets.UndoReleaseAsync(release.Id, request);
+                }
+            }
+            catch (SetReleaseUndoConflictException conflict)
+            {
+                if (!IsDisposed)
+                    ShowMessage(SetReleaseText.UndoRefusal(conflict.Conflict), MessageBoxButtons.OK, MessageBoxIcon.Information);
+            }
+            catch (Exception ex) when (ex is IOException || ex is HttpRequestException || ex is TaskCanceledException
+                || ex is System.Text.Json.JsonException)
+            {
+                if (!IsDisposed)
+                    ShowMessage($"Could not undo the release: {ex.Message}", MessageBoxButtons.OK, MessageBoxIcon.Warning);
+            }
+            finally
+            {
+                undoing = false;
+            }
+
+            if (!IsDisposed)
+                await LoadPageAsync(offset);
+        }
 
         /// <summary>Reads one page of releases; a later request discards an earlier one's result.</summary>
         internal async Task LoadPageAsync(int requestedOffset)
@@ -97,6 +169,7 @@ namespace OpenNest.Forms
                 if (!IsDisposed && request == pageRequest)
                 {
                     previousButton.Enabled = offset > 0;
+                    UpdateUndo();
                     nextButton.Enabled = page != null && offset + page.Items.Count < page.Total;
                 }
             }
@@ -117,6 +190,7 @@ namespace OpenNest.Forms
                 nestGrid.Rows.Add(
                     record?.Name ?? nest.NestId.ToString(),
                     SetReleaseText.Group(nest),
+                    SetReleaseText.Change(nest),
                     SetReleaseText.NestState(nest),
                     record?.Customer ?? "",
                     record == null || record.DateModified == default
diff --git a/docs/nest-storage.md b/docs/nest-storage.md
index cc65eda4..3777eed4 100644
--- a/docs/nest-storage.md
+++ b/docs/nest-storage.md
@@ -389,31 +389,49 @@ newer there than in the nest is listed first, then the set editor opens for
 review and Save; nothing is stored before then.
 
 **Release...** (the Sets tab, when the dialog was opened from a nest) reads the
-selected active set with its members and opens the release dialog. It lists one
-row per material group (`OpenNest.Data.SetReleasePlan`): material, grade,
-thickness, units, cut type, drawings, parts and status. **Kits (multiplier)**
-multiplies every quantity (1 to 1000); **Include archived drawings** puts
-archived members back in, otherwise they are named below the grid as left out.
-Each group has a **Release** tick; refused groups (two drawings with one name,
-or drawings without material or thickness) show why and cannot be ticked, and a
-tick survives changing the multiplier or the archived toggle. **Release**
-confirms, then runs `OpenNest.Data.SetReleaseSession`: every ticked group's nest
-is made as File > New would (the server's next nest name, the saved plate
-defaults and clamps), in the group's units, with the saved plate size and
-spacings converted (25.4 mm per inch) when those differ; the nest takes the
-group's material, grade and thickness, the set's customer and the **Draft**
-status. Each created nest opens in its own tab, bound to its server record, and
-the release (with the release notes) is recorded. The grid then shows every
-group's outcome: Created with the nest name, Refused or Failed with the reason,
-or Not started. Cancel stops between uploads, never during one. When every nest
-was created but recording failed, the button becomes **Record Release** and
-posts the same release again. A dialog runs one release.
+selected active set with its members and opens the release dialog with it listed.
+More sets are added by typing in **Add a set** (the list of matching active sets
+fills as you type; Enter or **Add** takes the picked set, or the one set whose
+name is exactly what was typed) and removed with **Remove Set**; each set's
+**Kits** (1 to 1000) multiplies its quantities, and a set is listed once. The
+grid below has one row per material group across all the sets
+(`OpenNest.Data.SetReleasePlan`): material, grade, thickness, units, cut type,
+drawings, parts, **Nest** and status. **Include archived drawings** puts archived
+members back in, otherwise they are named below the grid as left out. Each group
+has a **Release** tick; refused groups (two drawings with one name, or drawings
+without material or thickness) show why and cannot be ticked, and a tick
+survives changing the sets, kits or the archived toggle.
+
+**Nest** is **New Draft nest** or **Merge into** one of the Draft nests of the
+group's material, grade and thickness, listed with their sheet count and when
+they were saved. A merge discards that draft's layout and nests the whole demand
+again (the status column says so); **Undo Release** restores it. A draft open in
+a tab of this desktop is refused, since that tab could hold edits the merge would
+leave behind: close it first.
+
+**Release** confirms, then runs `OpenNest.Data.SetReleaseSession`: every ticked
+group's new nest is made as File > New would (the server's next nest name, the
+saved plate defaults and clamps), in the group's units, with the saved plate size
+and spacings converted (25.4 mm per inch) when those differ; the nest takes the
+group's material, grade and thickness, the sets' customer when they share one,
+and the **Draft** status. A merged draft is saved only while nobody else has
+saved it since it was listed. Each created or merged nest opens in its own tab,
+bound to its server record, and the release (with the release notes) is
+recorded. The grid then shows every group's outcome: Created or Merged into with
+the nest name, Refused or Failed with the reason, or Not started. Cancel stops
+between saves, never during one. When every nest was saved but recording failed,
+the button becomes **Record Release** and posts the same release again. A dialog
+runs one release.
 
 **Releases...** lists the releases that include the selected set, newest first:
 when, by whom, the set revision, the kits of this set (and how many other sets
 the release had), the number of nests, progress such as "2 of 3 cut" (deleted
-nests are not counted) or "Undone", and the notes. The selected
-release's nests show their material group and current status, or Deleted.
+nests are not counted) or "Undone", and the notes. The selected release's nests
+show their material group, what the release did ("Created", "Merged (revision
+3 → 4)", and what undo did) and current status, or Deleted. **Undo Release...**
+deletes the nests the release created (they can be recovered) and restores the
+drafts it merged into. When some nests were changed after the release, it lists
+them and offers to undo the others, leaving those as they are.
 
 **Nest > Edit** (Nest Info) shows, beside its buttons, the newest release that
 made or merged into a server nest ("Released from set 'Kit A' revision 3 ×2 on