fix(adminui): Monaco text syncs on demand, diagnostics are sequenced, Problems list (D1)

R04:P1 - the editor no longer ships its full text JS->.NET on every keystroke. It reports
at blur, and ScriptEdit / the VirtualTag modal read the authoritative value with
MonacoEditor.GetValueAsync at Save (validation runs after the pull). The Blazor hub's
MaximumReceiveMessageSize is raised from 32 KB to 1 MB. The JS refuses a value that
would not fit instead of sending an oversize frame, and Save surfaces that refusal
rather than persisting stale source.

R04:P9 - diagnostics carry a generation counter and an AbortController. Every edit aborts
the in-flight request, and only the response for the current text is applied.

R04:S2 - the always-empty inlay-hints provider, endpoint, service method and contracts
are removed.

R04:S3 - MarkersChanged is typed (DiagnosticMarker) and feeds a new ScriptProblemsList.
Clicking a problem calls RevealLineAsync. Markers cross to .NET only when a list
subscribes.

Refs #745

Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Pages/ScriptEdit.razor

@@ -11,6 +11,7 @@
 @using System.Text
 @using ZB.MOM.WW.OtOpcUa.Configuration
 @using ZB.MOM.WW.OtOpcUa.Configuration.Entities
+@using ZB.MOM.WW.OtOpcUa.AdminUI.ScriptAnalysis
 @inject IDbContextFactory<OtOpcUaConfigDbContext> DbFactory
 @inject NavigationManager Nav
 
@@ -30,7 +31,9 @@ else if (!IsNew && _existing is null)
 }
 else
 {
-    <EditForm Model="_form" OnValidSubmit="SubmitAsync" FormName="scriptEdit">
+    @* OnSubmit (not OnValidSubmit): the editor text is pulled from Monaco FIRST, then validated — the bound
+       SourceCode is only refreshed at blur, so validating before the pull could judge stale text. *@
+    <EditForm Model="_form" OnSubmit="SubmitAsync" FormName="scriptEdit">
         <DataAnnotationsValidator />
         <ValidationSummary class="alert alert-danger py-2 px-3" />
         <section class="panel rise">
@@ -57,7 +60,9 @@ else
         <section class="panel rise mt-3">
             <div class="panel-head">Source</div>
             <div style="padding:1rem">
-                    <MonacoEditor @bind-Value="_form.SourceCode" Height="420px" />
+                <MonacoEditor @ref="_editor" @bind-Value="_form.SourceCode" Height="420px"
+                              MarkersChanged="OnMarkersChanged" />
+                <ScriptProblemsList Markers="_markers" OnSelect="RevealProblemAsync" />
                 <div class="form-text">SHA-256 hash is computed automatically on save.</div>
             </div>
         </section>
@@ -84,6 +89,13 @@ else
     private bool _loaded;
     private bool _busy;
     private string? _error;
+    private MonacoEditor? _editor;
+    private IReadOnlyList<DiagnosticMarker> _markers = Array.Empty<DiagnosticMarker>();
+
+    private void OnMarkersChanged(IReadOnlyList<DiagnosticMarker> markers) => _markers = markers;
+
+    private Task RevealProblemAsync(DiagnosticMarker m)
+        => _editor is null ? Task.CompletedTask : _editor.RevealLineAsync(m.StartLineNumber, m.StartColumn);
 
     protected override async Task OnInitializedAsync()
     {
@@ -105,11 +117,21 @@ else
         _loaded = true;
     }
 
-    private async Task SubmitAsync()
+    private async Task SubmitAsync(EditContext editContext)
     {
         _busy = true; _error = null;
         try
         {
+            // The editor reports its text only at blur, so read the authoritative current value now. A read
+            // failure (e.g. the script is too large to send) aborts the save rather than persisting stale source.
+            if (_editor is not null)
+            {
+                var read = await _editor.GetValueAsync();
+                if (!read.Ok) { _error = $"Not saved: {read.Error}"; return; }
+                _form.SourceCode = read.Value!;
+            }
+            if (!editContext.Validate()) return;
+
             var sourceHash = HashSource(_form.SourceCode);
             await using var db = await DbFactory.CreateDbContextAsync();
             if (IsNew)

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

@@ -1,5 +1,6 @@
 @namespace ZB.MOM.WW.OtOpcUa.AdminUI.Components.Shared
 @using Microsoft.Extensions.Logging
+@using ZB.MOM.WW.OtOpcUa.AdminUI.ScriptAnalysis
 @implements IAsyncDisposable
 @inject IJSRuntime JS
 @inject Microsoft.Extensions.Logging.ILogger<MonacoEditor> Logger
@@ -22,7 +23,13 @@
      style="height: @Height; border: 1px solid var(--bs-border-color); border-radius: 0.25rem; overflow: hidden;"></div>
 
 @code {
+    /// <summary>
+    /// The editor text. Two-way bound, but the editor reports edits back only when it loses focus — never per
+    /// keystroke (each report is one circuit message carrying the whole script). A page that persists the text
+    /// must read the authoritative current value with <see cref="GetValueAsync"/> at save time.
+    /// </summary>
     [Parameter] public string Value { get; set; } = "";
+    /// <summary>Raised with the editor text when the editor loses focus after an edit (and from <see cref="GetValueAsync"/>).</summary>
     [Parameter] public EventCallback<string> ValueChanged { get; set; }
     [Parameter] public string Language { get; set; } = "csharp";
     [Parameter] public string Height { get; set; } = "320px";
@@ -37,11 +44,11 @@
     [Parameter] public string? EquipmentId { get; set; }
 
     /// <summary>
-    /// Fires whenever Monaco's marker set updates (after the 500 ms diagnostic
-    /// debounce). The marker DTO is not modelled yet — typed as object[] until a
-    /// later task wires the Roslyn-backed diagnostics.
+    /// Fires whenever Monaco's diagnostic marker set updates (after the 500 ms debounce, and only for the response
+    /// to the CURRENT text — superseded responses are dropped in the JS). Feeds <c>ScriptProblemsList</c>; the
+    /// markers are sent from JS only when this callback has a subscriber.
     /// </summary>
-    [Parameter] public EventCallback<object[]> MarkersChanged { get; set; }
+    [Parameter] public EventCallback<IReadOnlyList<DiagnosticMarker>> MarkersChanged { get; set; }
 
     private ElementReference _hostRef;
     private DotNetObjectReference<MonacoEditor>? _dotNetRef;
@@ -69,7 +76,9 @@
                         value = Value ?? "",
                         language = Language,
                         readOnly = ReadOnly,
-                        equipmentId = EquipmentId
+                        equipmentId = EquipmentId,
+                        maxSyncBytes = ScriptEditorLimits.MaxEditorSyncBytes,
+                        reportMarkers = MarkersChanged.HasDelegate
                     },
                     _dotNetRef);
                 _initialized = true;
@@ -126,9 +135,47 @@
         return ValueChanged.InvokeAsync(_lastSentValue);
     }
 
+    /// <summary>
+    /// Reads the editor's current text on demand (call it at Save), raises <see cref="ValueChanged"/> when it
+    /// differs from the last value reported, and returns it. Before the editor is live (prerender, failed init)
+    /// the bound <see cref="Value"/> is authoritative and is returned as-is.
+    /// </summary>
+    /// <returns>The current text, or an error (e.g. the script is too large to send) — never a stale value.</returns>
+    public async Task<EditorReadResult> GetValueAsync()
+    {
+        if (!_initialized) return new EditorReadResult(Value ?? "", null);
+        string? current;
+        try
+        {
+            current = await JS.InvokeAsync<string?>("MonacoBlazor.getValue", _id);
+        }
+        catch (JSDisconnectedException)
+        {
+            return new EditorReadResult(null, "The connection to the editor was lost; reload the page and try again.");
+        }
+        catch (JSException ex)
+        {
+            Logger.LogWarning(ex, "Monaco editor {EditorId}: failed to read the editor text.", _id);
+            // JSException.Message carries the JS stack after the first line; the author needs only the reason.
+            return new EditorReadResult(null, ex.Message.Split('\n', 2)[0].Trim());
+        }
+        if (current is null) return new EditorReadResult(Value ?? "", null);   // editor already disposed
+        await OnValueChanged(current);
+        return new EditorReadResult(current, null);
+    }
+
+    /// <summary>The outcome of <see cref="GetValueAsync"/>: the text, or why it could not be read.</summary>
+    /// <param name="Value">The editor text; null when <paramref name="Error"/> is set.</param>
+    /// <param name="Error">Why the text could not be read; null on success.</param>
+    public sealed record EditorReadResult(string? Value, string? Error)
+    {
+        /// <summary>True when <see cref="Value"/> holds the editor text.</summary>
+        public bool Ok => Error is null;
+    }
+
     [JSInvokable]
-    public Task OnMarkersChanged(object[] markers) =>
-        MarkersChanged.InvokeAsync(markers ?? Array.Empty<object>());
+    public Task OnMarkersChanged(DiagnosticMarker[]? markers) =>
+        MarkersChanged.InvokeAsync(markers ?? Array.Empty<DiagnosticMarker>());
 
     /// <summary>Programmatic scroll-to-line (called by the problems panel).</summary>
     public async Task RevealLineAsync(int line, int column = 1)

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

@@ -0,0 +1,57 @@
+@namespace ZB.MOM.WW.OtOpcUa.AdminUI.Components.Shared
+@using ZB.MOM.WW.OtOpcUa.AdminUI.ScriptAnalysis
+@* The script editor's Problems list. Fed by MonacoEditor.MarkersChanged; clicking a row calls OnSelect, which the
+   host wires to MonacoEditor.RevealLineAsync so the caret jumps to the problem. Ordering and wording live in
+   ScriptProblems (unit-tested). *@
+
+@{
+    var ordered = ScriptProblems.Order(Markers);
+}
+<div class="script-problems mt-2 small" role="region" aria-label="Problems">
+    <div class="d-flex align-items-center gap-2 text-muted mb-1">
+        <span class="fw-semibold">Problems</span>
+        <span>@ScriptProblems.Summary(ordered)</span>
+    </div>
+    @if (ordered.Count > 0)
+    {
+        <ul class="list-group list-group-flush border rounded" style="max-height: 10rem; overflow-y: auto;">
+            @foreach (var m in ordered.Take(MaxRows))
+            {
+                <li class="list-group-item list-group-item-action py-1 px-2 d-flex gap-2 align-items-baseline"
+                    role="button" tabindex="0" style="cursor: pointer;"
+                    title="Go to line @m.StartLineNumber, column @m.StartColumn"
+                    @onclick="() => OnSelect.InvokeAsync(m)"
+                    @onkeydown="e => OnKeyAsync(e, m)">
+                    <span class="badge @BadgeClass(m.Severity)">@ScriptProblems.SeverityLabel(m.Severity)</span>
+                    <span class="mono text-muted">@m.StartLineNumber:@m.StartColumn</span>
+                    <span class="flex-grow-1">@m.Message</span>
+                    <span class="mono text-muted">@m.Code</span>
+                </li>
+            }
+        </ul>
+        @if (ordered.Count > MaxRows)
+        {
+            <div class="text-muted mt-1">… and @(ordered.Count - MaxRows) more</div>
+        }
+    }
+</div>
+
+@code {
+    private const int MaxRows = 200;
+
+    /// <summary>The markers the editor last reported (null before the first diagnostics pass).</summary>
+    [Parameter] public IReadOnlyList<DiagnosticMarker>? Markers { get; set; }
+
+    /// <summary>Raised when the author picks a problem; wire it to <c>MonacoEditor.RevealLineAsync</c>.</summary>
+    [Parameter] public EventCallback<DiagnosticMarker> OnSelect { get; set; }
+
+    private Task OnKeyAsync(KeyboardEventArgs e, DiagnosticMarker m)
+        => e.Key is "Enter" or " " ? OnSelect.InvokeAsync(m) : Task.CompletedTask;
+
+    private static string BadgeClass(int severity) => severity switch
+    {
+        ScriptProblems.Error => "text-bg-danger",
+        ScriptProblems.Warning => "text-bg-warning",
+        _ => "text-bg-secondary",
+    };
+}

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

@@ -7,6 +7,7 @@
 @using System.ComponentModel.DataAnnotations
 @using Microsoft.AspNetCore.Components.Forms
 @using ZB.MOM.WW.OtOpcUa.AdminUI.Uns
+@using ZB.MOM.WW.OtOpcUa.AdminUI.ScriptAnalysis
 @inject IUnsTreeService Svc
 
 @if (Visible)
@@ -99,7 +100,9 @@
                                             Editing shared script "<span class="mono">@_scriptName</span>" — used by
                                             @_scriptUsageCount virtual tag(s). Changes affect all of them.
                                         </div>
-                                        <MonacoEditor @bind-Value="_scriptSource" Height="300px" EquipmentId="@EquipmentId" />
+                                        <MonacoEditor @ref="_scriptEditor" @bind-Value="_scriptSource" Height="300px" EquipmentId="@EquipmentId"
+                                                      MarkersChanged="OnScriptMarkersChanged" />
+                                        <ScriptProblemsList Markers="_scriptMarkers" OnSelect="RevealScriptProblemAsync" />
                                         @if (!string.IsNullOrWhiteSpace(_scriptError))
                                         {
                                             <div class="text-danger small mt-2">@_scriptError</div>
@@ -217,6 +220,24 @@
     private bool _scriptSaving;
     private bool _scriptSaved;
     private string? _scriptError;
+    private MonacoEditor? _scriptEditor;
+    private IReadOnlyList<DiagnosticMarker> _scriptMarkers = Array.Empty<DiagnosticMarker>();
+
+    private void OnScriptMarkersChanged(IReadOnlyList<DiagnosticMarker> markers) => _scriptMarkers = markers;
+
+    private Task RevealScriptProblemAsync(DiagnosticMarker m)
+        => _scriptEditor is null ? Task.CompletedTask : _scriptEditor.RevealLineAsync(m.StartLineNumber, m.StartColumn);
+
+    // The inline editor reports its text only at blur; pull the authoritative current value before acting on it.
+    // Returns false (with _scriptError set) when the text could not be read, so nothing stale is saved.
+    private async Task<bool> PullScriptSourceAsync()
+    {
+        if (_scriptEditor is null) return true;
+        var read = await _scriptEditor.GetValueAsync();
+        if (!read.Ok) { _scriptError = $"Not saved: {read.Error}"; return false; }
+        _scriptSource = read.Value!;
+        return true;
+    }
 
     // "New script" action state (shown only when no script is bound yet).
     private bool _scriptCreating;
@@ -358,8 +379,16 @@
     /// Toggles the inline script-source panel. Clears the stale "Script saved." banner when
     /// (re)expanding so a collapse/expand cycle doesn't re-show a confirmation from an earlier save.
     /// </summary>
-    private void ToggleScriptPanel()
+    private async Task ToggleScriptPanel()
     {
+        if (_scriptExpanded)
+        {
+            // Collapsing disposes the editor: keep its unsaved text in _scriptSource so re-opening shows it.
+            // A failed read keeps the panel open (with the error) rather than discarding the edits.
+            if (!await PullScriptSourceAsync()) return;
+            _scriptEditor = null;
+            _scriptMarkers = Array.Empty<DiagnosticMarker>();
+        }
         _scriptExpanded = !_scriptExpanded;
         if (_scriptExpanded)
         {
@@ -384,6 +413,7 @@
         _scriptError = null;
         try
         {
+            if (!await PullScriptSourceAsync()) return;
             var result = await Svc.UpdateScriptSourceAsync(_form.ScriptId, _scriptSource, _scriptRowVersion);
             if (result.Ok)
             {

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/EndpointRouteBuilderExtensions.cs

@@ -53,7 +53,7 @@ public static class EndpointRouteBuilderExtensions
     /// <returns>The same service collection, for chaining.</returns>
     public static IServiceCollection AddAdminUI(this IServiceCollection services)
     {
-        services.AddRazorComponents().AddInteractiveServerComponents();
+        services.AddRazorComponents().AddInteractiveServerComponents().AddHubOptions(o => o.MaximumReceiveMessageSize = ScriptAnalysis.ScriptEditorLimits.HubMaximumReceiveMessageSize);
         services.AddOtOpcUaDriverStatusServices();
 
         // Secrets-management UI (ZB.MOM.WW.Secrets.Ui RCL, mounted at /admin/secrets). Register its

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/ScriptAnalysis/ScriptAnalysisContracts.cs

@@ -22,7 +22,3 @@ public record SignatureHelpParameter(string Label, string? Documentation);
 
 public record FormatRequest(string Code);
 public record FormatResponse(string Code);
-
-public record InlayHintsRequest(string Code);
-public record InlayHintsResponse(IReadOnlyList<InlayHint> Hints);
-public record InlayHint(int Line, int Column, string Label);

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/ScriptAnalysis/ScriptAnalysisEndpoints.cs

@@ -27,7 +27,6 @@ public static class ScriptAnalysisEndpoints
         group.MapPost("/hover",          (HoverRequest r, ScriptAnalysisService s, CancellationToken ct) => Run(() => s.Hover(r, ct), ct));
         group.MapPost("/signature-help", (SignatureHelpRequest r, ScriptAnalysisService s, CancellationToken ct) => Run(() => Task.FromResult(s.SignatureHelp(r, ct)), ct));
         group.MapPost("/format",         (FormatRequest r, ScriptAnalysisService s) => Results.Ok(s.Format(r)));
-        group.MapPost("/inlay-hints",    (InlayHintsRequest r, ScriptAnalysisService s) => Results.Ok(s.InlayHints(r)));
         return endpoints;
     }
 

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/ScriptAnalysis/ScriptAnalysisService.cs

@@ -551,9 +551,4 @@ public sealed class ScriptAnalysisService
             return new FormatResponse(req.Code);
         }
     }
-    /// <summary>Returns editor inlay hints for the script. Currently a no-op (always empty) — the endpoint
-    /// exists for future use but the feature is not implemented.</summary>
-    /// <param name="req">The inlay-hints request (unused).</param>
-    /// <returns>An always-empty inlay-hints response.</returns>
-    public InlayHintsResponse InlayHints(InlayHintsRequest req) => new(Array.Empty<InlayHint>());
 }

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/ScriptAnalysis/ScriptEditorLimits.cs

@@ -0,0 +1,19 @@
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.ScriptAnalysis;
+
+/// <summary>Size limits for moving Monaco editor text across the Blazor Server circuit.</summary>
+/// <remarks>
+///     The editor text crosses JS → .NET only on demand (at blur and when a page saves), never per keystroke. Each
+///     crossing is ONE SignalR message, bounded by the Blazor hub's <c>MaximumReceiveMessageSize</c>. The framework
+///     default is 32 KB, which silently lost any larger script (the oversize invoke failed and Save persisted the
+///     stale source), so <c>AddAdminUI</c> raises it to <see cref="HubMaximumReceiveMessageSize"/>. The editor JS
+///     refuses to send a value whose serialized form exceeds <see cref="MaxEditorSyncBytes"/> — an oversize frame
+///     would tear the circuit down — and the save surfaces that refusal to the author instead.
+/// </remarks>
+public static class ScriptEditorLimits
+{
+    /// <summary>The Blazor hub's receive limit, in bytes (1 MB).</summary>
+    public const long HubMaximumReceiveMessageSize = 1024 * 1024;
+
+    /// <summary>The largest serialized editor value the JS will send, leaving 64 KB of frame headroom.</summary>
+    public const int MaxEditorSyncBytes = (int)HubMaximumReceiveMessageSize - 64 * 1024;
+}

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/ScriptAnalysis/ScriptProblems.cs

@@ -0,0 +1,54 @@
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.ScriptAnalysis;
+
+/// <summary>
+///     Presentation rules for the script editor's Problems list — the markers Monaco reports through
+///     <c>MonacoEditor.MarkersChanged</c> (the same <see cref="DiagnosticMarker"/> shape the diagnostics endpoint
+///     returns), rendered by <c>ScriptProblemsList</c>.
+/// </summary>
+public static class ScriptProblems
+{
+    /// <summary>Monaco's error severity.</summary>
+    public const int Error = 8;
+
+    /// <summary>Monaco's warning severity.</summary>
+    public const int Warning = 4;
+
+    /// <summary>Errors first, then warnings, then the rest; within a severity, by position.</summary>
+    /// <param name="markers">The reported markers (null treated as none).</param>
+    /// <returns>The markers in display order.</returns>
+    public static IReadOnlyList<DiagnosticMarker> Order(IEnumerable<DiagnosticMarker>? markers)
+        => (markers ?? Array.Empty<DiagnosticMarker>())
+            .OrderByDescending(m => m.Severity)
+            .ThenBy(m => m.StartLineNumber)
+            .ThenBy(m => m.StartColumn)
+            .ToList();
+
+    /// <summary>The label for a Monaco severity value.</summary>
+    /// <param name="severity">8 = error, 4 = warning, 2 = info, otherwise hint.</param>
+    /// <returns>The display label.</returns>
+    public static string SeverityLabel(int severity) => severity switch
+    {
+        Error => "Error",
+        Warning => "Warning",
+        2 => "Info",
+        _ => "Hint",
+    };
+
+    /// <summary>A one-line count, e.g. <c>"2 errors, 1 warning"</c>.</summary>
+    /// <param name="markers">The reported markers.</param>
+    /// <returns>The summary, or <c>"No problems"</c>.</returns>
+    public static string Summary(IReadOnlyCollection<DiagnosticMarker> markers)
+    {
+        if (markers.Count == 0) return "No problems";
+        var errors = markers.Count(m => m.Severity == Error);
+        var warnings = markers.Count(m => m.Severity == Warning);
+        var other = markers.Count - errors - warnings;
+        var parts = new List<string>(3);
+        if (errors > 0) parts.Add(Plural(errors, "error"));
+        if (warnings > 0) parts.Add(Plural(warnings, "warning"));
+        if (other > 0) parts.Add($"{other} other");
+        return string.Join(", ", parts);
+    }
+
+    private static string Plural(int n, string noun) => n == 1 ? $"1 {noun}" : $"{n} {noun}s";
+}

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/wwwroot/js/monaco-init.js

@@ -112,25 +112,6 @@
                 } catch (e) { return []; }
             }
         });
-        monaco.languages.registerInlayHintsProvider("csharp", {
-            provideInlayHints: async function (model) {
-                try {
-                    const resp = await fetch("/api/script-analysis/inlay-hints", {
-                        method: "POST", credentials: "same-origin",
-                        headers: { "Content-Type": "application/json" },
-                        body: JSON.stringify({ code: model.getValue() })
-                    });
-                    if (!resp.ok) return { hints: [], dispose: function () {} };
-                    const data = await resp.json();
-                    return {
-                        hints: (data.hints || []).map(function (h) {
-                            return { position: { lineNumber: h.line, column: h.column }, label: h.label, kind: 2, paddingRight: true };
-                        }),
-                        dispose: function () {}
-                    };
-                } catch (e) { return { hints: [], dispose: function () {} }; }
-            }
-        });
         monaco.languages.registerSignatureHelpProvider("csharp", {
             signatureHelpTriggerCharacters: ["(", ","],
             signatureHelpRetriggerCharacters: [","],
@@ -156,17 +137,41 @@
         });
     }
 
-    async function fetchDiagnostics(model) {
+    // Resolves to the marker array, or null when the request was aborted (superseded by a newer edit) — the
+    // caller must then leave the markers alone. A server/network failure still resolves to [] (clears markers).
+    async function fetchDiagnostics(model, signal) {
         try {
             const resp = await fetch("/api/script-analysis/diagnostics", {
-                method: "POST", credentials: "same-origin",
+                method: "POST", credentials: "same-origin", signal: signal,
                 headers: { "Content-Type": "application/json" },
                 body: JSON.stringify({ code: model.getValue(), equipmentId: equipmentIdOf(model) })
             });
             if (!resp.ok) return [];
             const data = await resp.json();
             return data.markers || [];
-        } catch (e) { return []; }
+        } catch (e) { return (signal && signal.aborted) ? null : []; }
+    }
+
+    // The editor text crosses the Blazor circuit (JS -> .NET) only on demand — at blur and when the page saves —
+    // never per keystroke. Each crossing is one SignalR message, bounded by the hub's MaximumReceiveMessageSize;
+    // an oversize message would tear the circuit down, so a value whose serialized form would not fit is refused
+    // here instead (getValue throws a descriptive error that .NET surfaces to the author).
+    // Blazor carries an interop value as a JSON string inside the hub frame; measuring it escaped twice is a
+    // conservative upper bound whichever hub protocol (BlazorPack or JSON) the circuit negotiated.
+    function serializedBytes(v) { return new TextEncoder().encode(JSON.stringify(JSON.stringify(v))).length; }
+    function tooLargeMessage(e, v) {
+        if (!e.maxSyncBytes) return null;
+        const bytes = serializedBytes(v);
+        return bytes > e.maxSyncBytes
+            ? "The script is too large for the editor to send to the server (" + bytes + " bytes; the limit is " + e.maxSyncBytes + " bytes)."
+            : null;
+    }
+    function syncValue(e) {
+        if (!e.dirty) return;
+        const v = e.editor.getValue();
+        if (tooLargeMessage(e, v)) return;          // stays dirty; the explicit save read reports the error
+        e.dirty = false;
+        e.dotNetRef.invokeMethodAsync("OnValueChanged", v).catch(function () { e.dirty = true; });
     }
 
     // A single body-level node for Monaco's overflow widgets (suggest / hover / parameter hints).
@@ -207,22 +212,38 @@
         // Stamp the owning-equipment id on the model so the global csharp providers can thread it into the
         // {{equip}}/<RefName> completion + diagnostics (null on the shared ScriptEdit page).
         try { const m0 = editor.getModel(); if (m0) m0.__otEquipmentId = options.equipmentId || null; } catch (x) {}
-        let diagTimer = null;
-        const scheduleDiagnostics = function () {
-            if (diagTimer) clearTimeout(diagTimer);
-            diagTimer = setTimeout(async function () {
-                const model = editor.getModel(); if (!model) return;
-                const markers = await fetchDiagnostics(model);
-                monaco.editor.setModelMarkers(model, "otopcua", markers);
-                dotNetRef.invokeMethodAsync("OnMarkersChanged", markers).catch(function () {});
-            }, 500);
+        const e = {
+            editor: editor, dotNetRef: dotNetRef, dirty: false,
+            maxSyncBytes: options.maxSyncBytes || 0, reportMarkers: !!options.reportMarkers,
+            diagTimer: null, diagGeneration: 0, diagAbort: null
+        };
+        // Diagnostics: the 500 ms debounce delays the START of a request; the generation counter + AbortController
+        // make sure only the response for the CURRENT text is applied. Every edit bumps the generation and aborts
+        // the in-flight request, so a slow older response can never overwrite newer markers.
+        const runDiagnostics = async function () {
+            const model = editor.getModel(); if (!model) return;
+            const generation = ++e.diagGeneration;
+            const ac = new AbortController();
+            e.diagAbort = ac;
+            const markers = await fetchDiagnostics(model, ac.signal);
+            if (markers === null || generation !== e.diagGeneration || editors[id] !== e) return;   // superseded
+            e.diagAbort = null;
+            monaco.editor.setModelMarkers(model, "otopcua", markers);
+            if (e.reportMarkers) dotNetRef.invokeMethodAsync("OnMarkersChanged", markers).catch(function () {});
+        };
+        e.scheduleDiagnostics = function () {
+            e.diagGeneration++;
+            if (e.diagAbort) { e.diagAbort.abort(); e.diagAbort = null; }
+            if (e.diagTimer) clearTimeout(e.diagTimer);
+            e.diagTimer = setTimeout(runDiagnostics, 500);
         };
         editor.onDidChangeModelContent(function () {
-            dotNetRef.invokeMethodAsync("OnValueChanged", editor.getValue()).catch(function () {});
-            if (options.language === "csharp") scheduleDiagnostics();
+            e.dirty = true;
+            if (options.language === "csharp") e.scheduleDiagnostics();
         });
-        editors[id] = { editor: editor, dotNetRef: dotNetRef };
-        if (options.language === "csharp") scheduleDiagnostics();
+        editor.onDidBlurEditorText(function () { syncValue(e); });
+        editors[id] = e;
+        if (options.language === "csharp") e.scheduleDiagnostics();
     }
     function setEditorOption(id, name, value) {
         const e = editors[id]; if (!e) return;
@@ -235,10 +256,28 @@
         const e = editors[id]; if (!e) return;
         e.editor.revealLineInCenter(line); e.editor.setPosition({ lineNumber: line, column: col || 1 }); e.editor.focus();
     }
-    function setValue(id, v) { const e = editors[id]; if (e && e.editor.getValue() !== v) e.editor.setValue(v || ""); }
-    function getValue(id) { const e = editors[id]; return e ? e.editor.getValue() : null; }
+    function setValue(id, v) {
+        const e = editors[id]; if (!e) return;
+        if (e.editor.getValue() !== v) e.editor.setValue(v || "");
+        e.dirty = false;                            // the text now equals what .NET holds
+    }
+    // Reads the current text on demand (Save). Throws when it would not fit in one circuit message.
+    function getValue(id) {
+        const e = editors[id]; if (!e) return null;
+        const v = e.editor.getValue();
+        const err = tooLargeMessage(e, v);
+        if (err) throw new Error(err);
+        e.dirty = false;
+        return v;
+    }
     function setMarkers(id, m) { const e = editors[id]; const model = e && e.editor.getModel(); if (model) monaco.editor.setModelMarkers(model, "otopcua", m || []); }
-    function dispose(id) { const e = editors[id]; if (!e) return; try { e.editor.dispose(); } catch (x) {} delete editors[id]; }
+    function dispose(id) {
+        const e = editors[id]; if (!e) return;
+        if (e.diagTimer) clearTimeout(e.diagTimer);
+        if (e.diagAbort) e.diagAbort.abort();
+        try { e.editor.dispose(); } catch (x) {}
+        delete editors[id];
+    }
 
     window.MonacoBlazor = { createEditor, setValue, getValue, setMarkers, setEditorOption, format, revealLine, dispose };
 })();