feat(adminui): isHistorized + historianTagname as first-class Tag fields

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Uns/TagEditors/HistorianWonderwareTagConfigEditor.razor

@@ -6,17 +6,6 @@
                placeholder="Reactor1.Temperature"
                @onchange="@(e => Update(() => _m.FullName = e.Value?.ToString() ?? string.Empty))" />
         <div class="form-text">The AVEVA Historian tagname the driver reads against.</div></div>
-    <div class="col-md-12">
-        <div class="form-check form-switch">
-            <input type="checkbox" class="form-check-input" checked="@_m.IsHistorized"
-                   @onchange="@(e => Update(() => _m.IsHistorized = e.Value is true))" />
-            <label class="form-check-label">Historized (expose OPC UA HistoryRead)</label>
-        </div>
-    </div>
-    <div class="col-md-12"><label class="form-label">Historian tagname override (optional)</label>
-        <input type="text" class="form-control form-control-sm mono" value="@_m.HistorianTagname"
-               @onchange="@(e => Update(() => _m.HistorianTagname = e.Value?.ToString() ?? string.Empty))" />
-        <div class="form-text">Blank defaults the historian tagname to the FullName above.</div></div>
 </div>
 
 @code {

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Uns/TagEditors/OpcUaClientTagConfigEditor.razor

@@ -6,17 +6,6 @@
                placeholder="nsu=urn:server:ns;s=Line3.Temp"
                @onchange="@(e => Update(() => _m.FullName = e.Value?.ToString() ?? string.Empty))" />
         <div class="form-text">The remote OPC UA NodeId the driver reads/writes/subscribes against. Use the browse picker on the driver page to find it.</div></div>
-    <div class="col-md-12">
-        <div class="form-check form-switch">
-            <input type="checkbox" class="form-check-input" checked="@_m.IsHistorized"
-                   @onchange="@(e => Update(() => _m.IsHistorized = e.Value is true))" />
-            <label class="form-check-label">Historized (expose OPC UA HistoryRead)</label>
-        </div>
-    </div>
-    <div class="col-md-12"><label class="form-label">Historian tagname override (optional)</label>
-        <input type="text" class="form-control form-control-sm mono" value="@_m.HistorianTagname"
-               @onchange="@(e => Update(() => _m.HistorianTagname = e.Value?.ToString() ?? string.Empty))" />
-        <div class="form-text">Blank defaults the historian tagname to the FullName above.</div></div>
 </div>
 
 @code {

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Uns/TagModal.razor

@@ -136,6 +136,39 @@
                             <ValidationMessage For="@(() => _form.TagConfig)" />
                         </div>
 
+                        @* Driver-agnostic server-side HistoryRead intent. Distinct from the native-alarm
+                           "Historize to AVEVA" toggle below: THIS gates TAG-VALUE history (root keys
+                           `isHistorized` / `historianTagname`, read by Phase7Composer.ExtractTagHistorize),
+                           merged onto the canonical TagConfig via the pure TagHistorizeConfig seam so it
+                           composes with the typed editor's driver-specific fields (both preserve unknown keys).
+                           Shown for EVERY driver once one is picked. *@
+                        @if (!string.IsNullOrEmpty(_form.DriverInstanceId))
+                        {
+                            <div class="mb-3">
+                                <label class="form-label">History</label>
+                                <div class="form-check form-switch">
+                                    <input class="form-check-input" type="checkbox" id="tag-historize"
+                                           checked="@_historizeState.IsHistorized"
+                                           @onchange="OnHistorizeChanged" />
+                                    <label class="form-check-label" for="tag-historize">Historize this tag (expose OPC UA HistoryRead)</label>
+                                </div>
+                                <div class="form-text">
+                                    When checked, the server serves OPC UA HistoryRead over this tag's value
+                                    from the configured historian.
+                                </div>
+                                @if (_historizeState.IsHistorized)
+                                {
+                                    <div class="mt-2">
+                                        <label class="form-label" for="tag-historian-tagname">Historian tagname (override, optional)</label>
+                                        <input type="text" class="form-control form-control-sm mono" id="tag-historian-tagname"
+                                               value="@_historizeState.HistorianTagname"
+                                               @onchange="OnHistorianTagnameChanged" />
+                                        <div class="form-text">Blank defaults the historian tagname to this tag's driver FullName.</div>
+                                    </div>
+                                }
+                            </div>
+                        }
+
                         @* Native-alarm options: shown only when the TagConfig carries an `alarm` object (the tag
                            is a Part 9 condition). The "Historize to AVEVA" toggle edits the alarm.historizeToAveva
                            opt-out (bool?, unchecked-via-clear ⇒ absent ⇒ historize default-on at the server gate;
@@ -211,6 +244,11 @@
     private bool _showGalaxyPicker;
     private string _galaxyAddress = "";
 
+    // Driver-agnostic server-side HistoryRead intent (root `isHistorized` / `historianTagname`), reflected
+    // for the "Historize this tag" controls. Re-read from _form.TagConfig whenever the modal (re)opens or
+    // the driver changes; the change handlers merge it back onto _form.TagConfig via TagHistorizeConfig.
+    private TagHistorizeConfig.HistorizeState _historizeState;
+
     // The DriverType of the currently-selected driver (drives editor dispatch). Null when no driver chosen.
     private string? SelectedDriverType =>
         Drivers.FirstOrDefault(d => d.Id == _form.DriverInstanceId).DriverType;
@@ -238,6 +276,8 @@
         _form.TagConfig = "{}";
         // The Galaxy reference belongs to the previous driver; clear the picker's working address too.
         _galaxyAddress = "";
+        // The reset TagConfig carries no history intent — reflect that in the historize controls.
+        _historizeState = TagHistorizeConfig.Read(_form.TagConfig);
     }
 
     // The operator picked a Galaxy reference (tag_name.AttributeName); store it as the canonical
@@ -255,14 +295,32 @@
         ["ConfigJsonChanged"] = EventCallback.Factory.Create<string>(this, v => _form.TagConfig = v),
     };
 
+    // Cache a single NativeAlarmModel parse keyed on the current TagConfig string, so the two computed
+    // properties below don't each re-parse the JSON on every render. Re-parsed only when TagConfig changes.
+    private NativeAlarmModel _nativeAlarm = NativeAlarmModel.FromJson("{}");
+    private string? _nativeAlarmSource;
+
+    private NativeAlarmModel NativeAlarm
+    {
+        get
+        {
+            if (_nativeAlarmSource != _form.TagConfig)
+            {
+                _nativeAlarmSource = _form.TagConfig;
+                _nativeAlarm = NativeAlarmModel.FromJson(_form.TagConfig);
+            }
+            return _nativeAlarm;
+        }
+    }
+
     // True when the current TagConfig carries an `alarm` object — i.e. the tag is materialised as a Part 9
     // native-alarm condition rather than a value variable. Gates the "Historize to AVEVA" toggle's visibility.
-    private bool HasNativeAlarm => NativeAlarmModel.FromJson(_form.TagConfig).IsAlarm;
+    private bool HasNativeAlarm => NativeAlarm.IsAlarm;
 
     // The native alarm's HistorizeToAveva intent reflected for the checkbox: absent (null) ⇒ historize
     // (default-on at the server gate), so the box is checked for both null and explicit true; only an
     // explicit false leaves it unchecked.
-    private bool AlarmHistorizeToAveva => NativeAlarmModel.FromJson(_form.TagConfig).HistorizeToAveva != false;
+    private bool AlarmHistorizeToAveva => NativeAlarm.HistorizeToAveva != false;
 
     // Toggle the alarm.historizeToAveva opt-out in the raw TagConfig. Checked ⇒ remove the key (null ⇒
     // absent ⇒ historize default-on); unchecked ⇒ write an explicit false (suppress the durable AVEVA row).
@@ -271,11 +329,28 @@
     {
         var model = NativeAlarmModel.FromJson(_form.TagConfig);
         if (!model.IsAlarm) { return; }
-        var isChecked = e.Value is bool b && b;
+        model.HistorizeToAveva = e.Value is true ? null : false;
-        model.HistorizeToAveva = isChecked ? null : false;
         _form.TagConfig = model.ToJson();
     }
 
+    // Toggle the root `isHistorized` tag-value history intent in the raw TagConfig, merged via the pure
+    // TagHistorizeConfig seam so the typed editor's driver-specific keys are preserved. Distinct from the
+    // native-alarm "Historize to AVEVA" opt-out above (that gates alarm-transition history, not tag values).
+    private void OnHistorizeChanged(ChangeEventArgs e)
+    {
+        var isHistorized = e.Value is true;
+        _form.TagConfig = TagHistorizeConfig.Set(_form.TagConfig, isHistorized, _historizeState.HistorianTagname);
+        _historizeState = TagHistorizeConfig.Read(_form.TagConfig);
+    }
+
+    // Merge the optional historian-tagname override (root `historianTagname`) into the raw TagConfig.
+    private void OnHistorianTagnameChanged(ChangeEventArgs e)
+    {
+        var tagname = e.Value?.ToString() ?? string.Empty;
+        _form.TagConfig = TagHistorizeConfig.Set(_form.TagConfig, _historizeState.IsHistorized, tagname);
+        _historizeState = TagHistorizeConfig.Read(_form.TagConfig);
+    }
+
     protected override void OnParametersSet()
     {
         // Rebuild the working form whenever the host (re)opens the modal for a fresh target.
@@ -301,6 +376,8 @@
         _showGalaxyPicker = false;
         // Seed the picker's working address from any existing {"FullName":"..."} so it opens pre-populated.
         _galaxyAddress = ReadFullName(_form.TagConfig);
+        // Seed the historize controls from any existing root isHistorized/historianTagname keys.
+        _historizeState = TagHistorizeConfig.Read(_form.TagConfig);
     }
 
     // Best-effort extraction of FullName from a Galaxy TagConfig; returns "" when absent or unparseable.

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Uns/TagEditors/HistorianWonderwareTagConfigModel.cs

@@ -4,26 +4,20 @@ namespace ZB.MOM.WW.OtOpcUa.AdminUI.Uns.TagEditors;
 
 /// <summary>Typed working model for a Wonderware (AVEVA) Historian equipment tag's TagConfig JSON. The
 /// tag binds to a historian tag by its full reference (<c>FullName</c> — the historian tagname/source
-/// the driver reads against), plus the optional driver-agnostic server-side HistoryRead intent
+/// the driver reads against). Preserves unrecognised JSON keys across a load→save.</summary>
-/// (<c>isHistorized</c> / <c>historianTagname</c>). Preserves unrecognised JSON keys across a load→save.</summary>
 /// <remarks>
 ///     The <c>FullName</c> key is intentionally PascalCase: the deploy-time composer + node walker
 ///     (<c>Phase7Composer.ExtractTagFullName</c>, <c>EquipmentNodeWalker</c>) read it via a
 ///     case-sensitive <c>TryGetProperty("FullName", …)</c>, so the editor MUST persist that exact
-///     casing. The history keys (<c>isHistorized</c> / <c>historianTagname</c>) are camelCase to match
+///     casing. The driver-agnostic server-side HistoryRead intent keys (<c>isHistorized</c> /
-///     <c>Phase7Composer.ExtractTagHistorize</c>.
+///     <c>historianTagname</c>) are NOT modelled here — they are owned by the TagModal-merge seam
+///     (<see cref="TagHistorizeConfig"/>) and survive a load→save of this model as preserved unknown keys.
 /// </remarks>
 public sealed class HistorianWonderwareTagConfigModel
 {
     /// <summary>Historian tagname/source the tag binds to (the driver-side full reference). Required.</summary>
     public string FullName { get; set; } = "";
 
-    /// <summary>Whether the server exposes OPC UA HistoryRead over this tag's variable node.</summary>
-    public bool IsHistorized { get; set; }
-
-    /// <summary>Optional historian tagname override; blank means the historian tagname defaults to <see cref="FullName"/>.</summary>
-    public string HistorianTagname { get; set; } = "";
-
     private JsonObject _bag = new();
 
     /// <summary>Loads a model from a TagConfig JSON string, defaulting any absent field and retaining
@@ -35,24 +29,17 @@ public sealed class HistorianWonderwareTagConfigModel
         return new HistorianWonderwareTagConfigModel
         {
             FullName = TagConfigJson.GetString(o, "FullName") ?? "",
-            IsHistorized = TagConfigJson.GetBool(o, "isHistorized"),
-            HistorianTagname = TagConfigJson.GetString(o, "historianTagname") ?? "",
             _bag = o,
         };
     }
 
     /// <summary>Serialises this model back to a TagConfig JSON string over the preserved key bag.
-    /// <c>FullName</c> is written PascalCase (the composer/walker contract key); the history keys are
+    /// <c>FullName</c> is written PascalCase (the composer/walker contract key); any history keys merged
-    /// written camelCase and dropped when default (absent <c>isHistorized</c> ⇒ false at the composer;
+    /// by the TagModal (<c>isHistorized</c> / <c>historianTagname</c>) are carried through untouched as
-    /// blank <c>historianTagname</c> ⇒ defaults to <c>FullName</c>).</summary>
+    /// preserved unknown keys.</summary>
     public string ToJson()
     {
         TagConfigJson.Set(_bag, "FullName", FullName.Trim());
-        // Drop isHistorized when false so the persisted blob stays minimal and matches the
-        // composer's "absent ⇒ false" convention; same for a blank historianTagname override.
-        TagConfigJson.Set(_bag, "isHistorized", IsHistorized ? true : null);
-        TagConfigJson.Set(_bag, "historianTagname",
-            string.IsNullOrWhiteSpace(HistorianTagname) ? null : HistorianTagname.Trim());
         return TagConfigJson.Serialize(_bag);
     }
 

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Uns/TagEditors/OpcUaClientTagConfigModel.cs

@@ -4,27 +4,21 @@ namespace ZB.MOM.WW.OtOpcUa.AdminUI.Uns.TagEditors;
 
 /// <summary>Typed working model for an OPC UA Client (gateway) equipment tag's TagConfig JSON. The tag
 /// is bound to the upstream OPC UA server node by its full reference (<c>FullName</c> — the persisted
-/// stable <c>nsu=…;s=…</c> or plain <c>ns=2;s=…</c> NodeId the driver reads/writes/subscribes against),
+/// stable <c>nsu=…;s=…</c> or plain <c>ns=2;s=…</c> NodeId the driver reads/writes/subscribes against).
-/// plus the optional driver-agnostic server-side HistoryRead intent (<c>isHistorized</c> /
+/// Preserves unrecognised JSON keys across a load→save.</summary>
-/// <c>historianTagname</c>). Preserves unrecognised JSON keys across a load→save.</summary>
 /// <remarks>
 ///     The <c>FullName</c> key is intentionally PascalCase: the deploy-time composer + node walker
 ///     (<c>Phase7Composer.ExtractTagFullName</c>, <c>EquipmentNodeWalker</c>) read it via a
 ///     case-sensitive <c>TryGetProperty("FullName", …)</c>, so the editor MUST persist that exact
-///     casing. The history keys (<c>isHistorized</c> / <c>historianTagname</c>) are camelCase to match
+///     casing. The driver-agnostic server-side HistoryRead intent keys (<c>isHistorized</c> /
-///     <c>Phase7Composer.ExtractTagHistorize</c>.
+///     <c>historianTagname</c>) are NOT modelled here — they are owned by the TagModal-merge seam
+///     (<see cref="TagHistorizeConfig"/>) and survive a load→save of this model as preserved unknown keys.
 /// </remarks>
 public sealed class OpcUaClientTagConfigModel
 {
     /// <summary>Upstream OPC UA node reference the tag binds to (the driver-side full reference). Required.</summary>
     public string FullName { get; set; } = "";
 
-    /// <summary>Whether the server exposes OPC UA HistoryRead over this tag's variable node.</summary>
-    public bool IsHistorized { get; set; }
-
-    /// <summary>Optional historian tagname override; blank means the historian tagname defaults to <see cref="FullName"/>.</summary>
-    public string HistorianTagname { get; set; } = "";
-
     private JsonObject _bag = new();
 
     /// <summary>Loads a model from a TagConfig JSON string, defaulting any absent field and retaining
@@ -36,24 +30,17 @@ public sealed class OpcUaClientTagConfigModel
         return new OpcUaClientTagConfigModel
         {
             FullName = TagConfigJson.GetString(o, "FullName") ?? "",
-            IsHistorized = TagConfigJson.GetBool(o, "isHistorized"),
-            HistorianTagname = TagConfigJson.GetString(o, "historianTagname") ?? "",
             _bag = o,
         };
     }
 
     /// <summary>Serialises this model back to a TagConfig JSON string over the preserved key bag.
-    /// <c>FullName</c> is written PascalCase (the composer/walker contract key); the history keys are
+    /// <c>FullName</c> is written PascalCase (the composer/walker contract key); any history keys merged
-    /// written camelCase and dropped when default (absent <c>isHistorized</c> ⇒ false at the composer;
+    /// by the TagModal (<c>isHistorized</c> / <c>historianTagname</c>) are carried through untouched as
-    /// blank <c>historianTagname</c> ⇒ defaults to <c>FullName</c>).</summary>
+    /// preserved unknown keys.</summary>
     public string ToJson()
     {
         TagConfigJson.Set(_bag, "FullName", FullName.Trim());
-        // Drop isHistorized when false so the persisted blob stays minimal and matches the
-        // composer's "absent ⇒ false" convention; same for a blank historianTagname override.
-        TagConfigJson.Set(_bag, "isHistorized", IsHistorized ? true : null);
-        TagConfigJson.Set(_bag, "historianTagname",
-            string.IsNullOrWhiteSpace(HistorianTagname) ? null : HistorianTagname.Trim());
         return TagConfigJson.Serialize(_bag);
     }
 

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Uns/TagEditors/TagHistorizeConfig.cs

@@ -0,0 +1,47 @@
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.Uns.TagEditors;
+
+/// <summary>
+/// Pure, driver-agnostic merge helper for the two server-side HistoryRead intent keys at the ROOT of a
+/// tag's <c>TagConfig</c> JSON: <c>isHistorized</c> (camelCase bool — omit/false default) and
+/// <c>historianTagname</c> (camelCase string override — omit when blank). These map to what the server's
+/// <c>Phase7Composer.ExtractTagHistorize</c> reads (see <c>docs/Historian.md</c>).
+///
+/// <para>
+/// This is the TagModal-merge seam: the TagModal owns the canonical TagConfig JSON; the driver's typed
+/// editor reads/writes its driver-specific fields on that same JSON, and the modal's "Historize this tag"
+/// checkbox + "Historian tagname (override)" textbox read/write these two keys through this helper. They
+/// COMPOSE because both sides preserve every unrecognised key (delegated to
+/// <see cref="TagConfigJson.ParseOrNew"/> / <see cref="TagConfigJson.Set"/>), so neither clobbers the
+/// other's fields. These keys are intentionally NOT carried inside any per-driver typed model.
+/// </para>
+/// </summary>
+public static class TagHistorizeConfig
+{
+    /// <summary>The two history-intent values parsed from a TagConfig JSON's root.</summary>
+    /// <param name="IsHistorized">Whether the server exposes OPC UA HistoryRead over this tag's node.</param>
+    /// <param name="HistorianTagname">Optional historian tagname override; <c>""</c> means default to the tag's FullName.</param>
+    public readonly record struct HistorizeState(bool IsHistorized, string HistorianTagname);
+
+    /// <summary>Reads the history-intent keys from a TagConfig JSON, defaulting any absent key
+    /// (null/blank/malformed input ⇒ <c>(false, "")</c>).</summary>
+    public static HistorizeState Read(string? json)
+    {
+        var o = TagConfigJson.ParseOrNew(json);
+        return new HistorizeState(
+            TagConfigJson.GetBool(o, "isHistorized"),
+            TagConfigJson.GetString(o, "historianTagname") ?? "");
+    }
+
+    /// <summary>Merges the two history-intent keys into <paramref name="json"/>, preserving every other
+    /// (driver-specific or unknown) key. <c>isHistorized</c> is dropped when false (absent ⇒ false at the
+    /// composer); <c>historianTagname</c> is dropped when null/blank (absent ⇒ defaults to FullName) and
+    /// trimmed otherwise.</summary>
+    public static string Set(string? json, bool isHistorized, string? historianTagname)
+    {
+        var o = TagConfigJson.ParseOrNew(json);
+        TagConfigJson.Set(o, "isHistorized", isHistorized ? true : null);
+        TagConfigJson.Set(o, "historianTagname",
+            string.IsNullOrWhiteSpace(historianTagname) ? null : historianTagname.Trim());
+        return TagConfigJson.Serialize(o);
+    }
+}

tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/Uns/HistorianWonderwareTagConfigModelTests.cs

@@ -16,66 +16,38 @@ public sealed class HistorianWonderwareTagConfigModelTests
         var m = HistorianWonderwareTagConfigModel.FromJson(json);
 
         m.FullName.ShouldBe("");
-        m.IsHistorized.ShouldBeFalse();
-        m.HistorianTagname.ShouldBe("");
     }
 
     [Fact]
-    public void FromJson_reads_all_fields()
+    public void FromJson_reads_FullName()
     {
         var m = HistorianWonderwareTagConfigModel.FromJson(
-            """{"FullName":"SysTimeSec","isHistorized":true,"historianTagname":"Reactor1.Temp"}""");
+            """{"FullName":"Reactor1.Temp"}""");
 
-        m.FullName.ShouldBe("SysTimeSec");
+        m.FullName.ShouldBe("Reactor1.Temp");
-        m.IsHistorized.ShouldBeTrue();
-        m.HistorianTagname.ShouldBe("Reactor1.Temp");
     }
 
     [Fact]
-    public void Round_trip_preserves_all_fields()
+    public void Round_trip_preserves_FullName()
     {
-        var m = new HistorianWonderwareTagConfigModel
+        var m = new HistorianWonderwareTagConfigModel { FullName = "Reactor1.Temp" };
-        {
-            FullName = "Reactor1.Temp",
-            IsHistorized = true,
-            HistorianTagname = "Reactor1.Temp.Override",
-        };
 
         var json = m.ToJson();
         var m2 = HistorianWonderwareTagConfigModel.FromJson(json);
 
         m2.FullName.ShouldBe("Reactor1.Temp");
-        m2.IsHistorized.ShouldBeTrue();
-        m2.HistorianTagname.ShouldBe("Reactor1.Temp.Override");
     }
 
     [Fact]
-    public void ToJson_emits_PascalCase_FullName_and_camelCase_history_keys()
+    public void ToJson_emits_PascalCase_FullName()
     {
-        var m = new HistorianWonderwareTagConfigModel
+        var m = new HistorianWonderwareTagConfigModel { FullName = "Reactor1.Temp" };
-        {
-            FullName = "Reactor1.Temp",
-            IsHistorized = true,
-            HistorianTagname = "Reactor1.Temp.Override",
-        };
 
         var json = m.ToJson();
 
         // FullName is the composer/walker contract key — PascalCase, case-sensitive.
         json.ShouldContain("\"FullName\":\"Reactor1.Temp\"");
         json.ShouldNotContain("\"fullName\"", Case.Sensitive);
-        json.ShouldContain("\"isHistorized\":true");
-        json.ShouldContain("\"historianTagname\":\"Reactor1.Temp.Override\"");
-    }
-
-    [Fact]
-    public void ToJson_omits_history_keys_when_default()
-    {
-        var json = new HistorianWonderwareTagConfigModel { FullName = "Reactor1.Temp" }.ToJson();
-
-        json.ShouldContain("\"FullName\":\"Reactor1.Temp\"");
-        json.ShouldNotContain("isHistorized");
-        json.ShouldNotContain("historianTagname");
     }
 
     [Fact]
@@ -91,6 +63,20 @@ public sealed class HistorianWonderwareTagConfigModelTests
         json.ShouldContain("\"FullName\":\"Reactor1.Temp\"");
     }
 
+    [Fact]
+    public void FromJson_then_ToJson_preserves_TagModal_merged_history_keys()
+    {
+        // The TagModal-merge seam writes isHistorized/historianTagname at the TagConfig root; this model
+        // does NOT model them, so they must survive a load→save untouched as preserved unknown keys.
+        var json = HistorianWonderwareTagConfigModel
+            .FromJson("""{"FullName":"Reactor1.Temp","isHistorized":true,"historianTagname":"Reactor1.Temp.Override"}""")
+            .ToJson();
+
+        json.ShouldContain("\"isHistorized\":true");
+        json.ShouldContain("\"historianTagname\":\"Reactor1.Temp.Override\"");
+        json.ShouldContain("\"FullName\":\"Reactor1.Temp\"");
+    }
+
     [Fact]
     public void ToJson_trims_FullName()
     {

tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/Uns/OpcUaClientTagConfigModelTests.cs

@@ -16,66 +16,38 @@ public sealed class OpcUaClientTagConfigModelTests
         var m = OpcUaClientTagConfigModel.FromJson(json);
 
         m.FullName.ShouldBe("");
-        m.IsHistorized.ShouldBeFalse();
-        m.HistorianTagname.ShouldBe("");
     }
 
     [Fact]
-    public void FromJson_reads_all_fields()
+    public void FromJson_reads_FullName()
     {
         var m = OpcUaClientTagConfigModel.FromJson(
-            """{"FullName":"nsu=urn:srv;s=Line3.Temp","isHistorized":true,"historianTagname":"Line3_Temp"}""");
+            """{"FullName":"nsu=urn:srv;s=Line3.Temp"}""");
 
         m.FullName.ShouldBe("nsu=urn:srv;s=Line3.Temp");
-        m.IsHistorized.ShouldBeTrue();
-        m.HistorianTagname.ShouldBe("Line3_Temp");
     }
 
     [Fact]
-    public void Round_trip_preserves_all_fields()
+    public void Round_trip_preserves_FullName()
     {
-        var m = new OpcUaClientTagConfigModel
+        var m = new OpcUaClientTagConfigModel { FullName = "ns=2;s=Line3.Temp" };
-        {
-            FullName = "ns=2;s=Line3.Temp",
-            IsHistorized = true,
-            HistorianTagname = "Line3_Temp",
-        };
 
         var json = m.ToJson();
         var m2 = OpcUaClientTagConfigModel.FromJson(json);
 
         m2.FullName.ShouldBe("ns=2;s=Line3.Temp");
-        m2.IsHistorized.ShouldBeTrue();
-        m2.HistorianTagname.ShouldBe("Line3_Temp");
     }
 
     [Fact]
-    public void ToJson_emits_PascalCase_FullName_and_camelCase_history_keys()
+    public void ToJson_emits_PascalCase_FullName()
     {
-        var m = new OpcUaClientTagConfigModel
+        var m = new OpcUaClientTagConfigModel { FullName = "ns=2;s=Line3.Temp" };
-        {
-            FullName = "ns=2;s=Line3.Temp",
-            IsHistorized = true,
-            HistorianTagname = "Line3_Temp",
-        };
 
         var json = m.ToJson();
 
         // FullName is the composer/walker contract key — PascalCase, case-sensitive.
         json.ShouldContain("\"FullName\":\"ns=2;s=Line3.Temp\"");
         json.ShouldNotContain("\"fullName\"", Case.Sensitive);
-        json.ShouldContain("\"isHistorized\":true");
-        json.ShouldContain("\"historianTagname\":\"Line3_Temp\"");
-    }
-
-    [Fact]
-    public void ToJson_omits_history_keys_when_default()
-    {
-        var json = new OpcUaClientTagConfigModel { FullName = "ns=2;s=X" }.ToJson();
-
-        json.ShouldContain("\"FullName\":\"ns=2;s=X\"");
-        json.ShouldNotContain("isHistorized");
-        json.ShouldNotContain("historianTagname");
     }
 
     [Fact]
@@ -91,6 +63,20 @@ public sealed class OpcUaClientTagConfigModelTests
         json.ShouldContain("\"FullName\":\"ns=2;s=X\"");
     }
 
+    [Fact]
+    public void FromJson_then_ToJson_preserves_TagModal_merged_history_keys()
+    {
+        // The TagModal-merge seam writes isHistorized/historianTagname at the TagConfig root; this model
+        // does NOT model them, so they must survive a load→save untouched as preserved unknown keys.
+        var json = OpcUaClientTagConfigModel
+            .FromJson("""{"FullName":"ns=2;s=X","isHistorized":true,"historianTagname":"Line3_Temp"}""")
+            .ToJson();
+
+        json.ShouldContain("\"isHistorized\":true");
+        json.ShouldContain("\"historianTagname\":\"Line3_Temp\"");
+        json.ShouldContain("\"FullName\":\"ns=2;s=X\"");
+    }
+
     [Fact]
     public void ToJson_trims_FullName()
     {

tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/Uns/TagHistorizeConfigTests.cs

@@ -0,0 +1,126 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.AdminUI.Uns.TagEditors;
+
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.Tests.Uns;
+
+/// <summary>
+/// Unit tests for the driver-agnostic <see cref="TagHistorizeConfig"/> merge helper — the pure seam the
+/// TagModal uses to read/write the root <c>isHistorized</c> / <c>historianTagname</c> history keys on the
+/// canonical TagConfig JSON WITHOUT disturbing the driver's own (typed-editor) fields. Both this helper and
+/// every typed editor preserve unknown keys, so they compose over the same JSON blob.
+/// </summary>
+public sealed class TagHistorizeConfigTests
+{
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("   ")]
+    [InlineData("{}")]
+    [InlineData("not json")]
+    public void Read_returns_defaults_for_empty_or_malformed(string? json)
+    {
+        var h = TagHistorizeConfig.Read(json);
+
+        h.IsHistorized.ShouldBeFalse();
+        h.HistorianTagname.ShouldBe("");
+    }
+
+    [Fact]
+    public void Read_reads_both_keys()
+    {
+        var h = TagHistorizeConfig.Read("""{"FullName":"ns=2;s=X","isHistorized":true,"historianTagname":"Line3_Temp"}""");
+
+        h.IsHistorized.ShouldBeTrue();
+        h.HistorianTagname.ShouldBe("Line3_Temp");
+    }
+
+    [Fact]
+    public void Set_true_with_tagname_writes_both_camelCase_keys()
+    {
+        var json = TagHistorizeConfig.Set("""{"FullName":"ns=2;s=X"}""", isHistorized: true, historianTagname: "Line3_Temp");
+
+        json.ShouldContain("\"isHistorized\":true");
+        json.ShouldContain("\"historianTagname\":\"Line3_Temp\"");
+        // The driver field is untouched.
+        json.ShouldContain("\"FullName\":\"ns=2;s=X\"");
+    }
+
+    [Fact]
+    public void Set_true_round_trips_through_Read()
+    {
+        var json = TagHistorizeConfig.Set("{}", isHistorized: true, historianTagname: "Reactor1.Temp");
+
+        var h = TagHistorizeConfig.Read(json);
+        h.IsHistorized.ShouldBeTrue();
+        h.HistorianTagname.ShouldBe("Reactor1.Temp");
+    }
+
+    [Fact]
+    public void Set_false_removes_isHistorized_key()
+    {
+        var json = TagHistorizeConfig.Set(
+            """{"FullName":"ns=2;s=X","isHistorized":true,"historianTagname":"Line3_Temp"}""",
+            isHistorized: false, historianTagname: "Line3_Temp");
+
+        json.ShouldNotContain("isHistorized");
+        json.ShouldContain("\"FullName\":\"ns=2;s=X\"");
+    }
+
+    [Fact]
+    public void Set_blank_tagname_removes_historianTagname_key()
+    {
+        var json = TagHistorizeConfig.Set(
+            """{"isHistorized":true,"historianTagname":"Old"}""",
+            isHistorized: true, historianTagname: "   ");
+
+        json.ShouldContain("\"isHistorized\":true");
+        json.ShouldNotContain("historianTagname");
+    }
+
+    [Fact]
+    public void Set_null_tagname_removes_historianTagname_key()
+    {
+        var json = TagHistorizeConfig.Set(
+            """{"isHistorized":true,"historianTagname":"Old"}""",
+            isHistorized: true, historianTagname: null);
+
+        json.ShouldContain("\"isHistorized\":true");
+        json.ShouldNotContain("historianTagname");
+    }
+
+    [Fact]
+    public void Set_trims_historianTagname()
+    {
+        var json = TagHistorizeConfig.Set("{}", isHistorized: true, historianTagname: "  Line3_Temp  ");
+
+        json.ShouldContain("\"historianTagname\":\"Line3_Temp\"");
+    }
+
+    [Fact]
+    public void Set_preserves_driver_specific_unknown_keys()
+    {
+        var json = TagHistorizeConfig.Set(
+            """{"register":40001,"scale":0.1,"nested":{"a":1}}""",
+            isHistorized: true, historianTagname: "T");
+
+        json.ShouldContain("register");
+        json.ShouldContain("40001");
+        json.ShouldContain("scale");
+        json.ShouldContain("0.1");
+        json.ShouldContain("nested");
+        json.ShouldContain("\"isHistorized\":true");
+        json.ShouldContain("\"historianTagname\":\"T\"");
+    }
+
+    [Fact]
+    public void Set_on_malformed_input_starts_from_empty_object()
+    {
+        var json = TagHistorizeConfig.Set("not json", isHistorized: true, historianTagname: null);
+
+        json.ShouldContain("\"isHistorized\":true");
+        // No crash, valid object emitted.
+        json.ShouldStartWith("{");
+        json.ShouldEndWith("}");
+    }
+}