diff --git a/src/ScadaLink.CentralUI/Components/Shared/AlarmTriggerEditor.razor b/src/ScadaLink.CentralUI/Components/Shared/AlarmTriggerEditor.razor
index bb79bf5..6f098b4 100644
--- a/src/ScadaLink.CentralUI/Components/Shared/AlarmTriggerEditor.razor
+++ b/src/ScadaLink.CentralUI/Components/Shared/AlarmTriggerEditor.razor
@@ -12,6 +12,10 @@
 <div class="border rounded bg-white p-3">
 
     @* ── Monitored attribute ───────────────────────────────────────────── *@
+    @* Expression triggers reference attributes inside the C# expression itself,
+       so they do not use the single-attribute picker. *@
+    @if (TriggerType != AlarmTriggerType.Expression)
+    {
     <div class="mb-3">
         <label for="alarm-attr-select" class="form-label small text-uppercase text-muted fw-semibold mb-1">
             Monitored attribute
@@ -67,6 +71,7 @@
             </div>
         }
     </div>
+    }
 
     @* ── Type-specific block ───────────────────────────────────────────── *@
     @switch (TriggerType)
@@ -83,6 +88,9 @@
         case AlarmTriggerType.HiLo:
             @RenderHiLo();
             break;
+        case AlarmTriggerType.Expression:
+            @RenderExpression();
+            break;
     }
 
     @* ── Hint ──────────────────────────────────────────────────────────── *@
@@ -559,6 +567,30 @@
         await Emit();
     }
 
+    // ── Expression ─────────────────────────────────────────────────────────
+
+    private RenderFragment RenderExpression() => __builder =>
+    {
+        <label class="form-label small text-uppercase text-muted fw-semibold mb-1">Trigger expression</label>
+        <MonacoEditor Height="120px"
+                      Language="csharp"
+                      ScriptKind="ScriptAnalysis.ScriptKind.Template"
+                      ShowToolbar="false"
+                      Value="@(_model.Expression ?? string.Empty)"
+                      ValueChanged="OnExpressionChanged"
+                      SelfAttributes="@TriggerAttributeMapper.SelfAttributes(AvailableAttributes)"
+                      Children="@TriggerAttributeMapper.Children(AvailableAttributes)" />
+        <div class="form-text">
+            A boolean C# expression — e.g. <code>Attributes["Temperature"] &gt; 80</code>.
+        </div>
+    };
+
+    private async Task OnExpressionChanged(string value)
+    {
+        _model.Expression = value;
+        await Emit();
+    }
+
     // ── Hint text ──────────────────────────────────────────────────────────
 
     private string BuildHint()
@@ -582,6 +614,9 @@
 
             AlarmTriggerType.HiLo => BuildHiLoHint(attr),
 
+            AlarmTriggerType.Expression =>
+                "Alarm is active while this expression is true.",
+
             _ => string.Empty
         };
     }
diff --git a/src/ScadaLink.CentralUI/Components/Shared/ScriptTriggerEditor.razor b/src/ScadaLink.CentralUI/Components/Shared/ScriptTriggerEditor.razor
index 0f5a3ae..07f0dad 100644
--- a/src/ScadaLink.CentralUI/Components/Shared/ScriptTriggerEditor.razor
+++ b/src/ScadaLink.CentralUI/Components/Shared/ScriptTriggerEditor.razor
@@ -23,6 +23,7 @@
             <option value="Interval">Interval — run on a fixed timer</option>
             <option value="ValueChange">Value change — run when an attribute changes</option>
             <option value="Conditional">Conditional — run when a condition is met</option>
+            <option value="Expression">Expression — run when a boolean expression becomes true</option>
             <option value="Call">Call — run only when invoked by another script</option>
             @if (_kind == ScriptTriggerKind.Unknown)
             {
@@ -45,6 +46,9 @@
         case ScriptTriggerKind.Conditional:
             @RenderConditional();
             break;
+        case ScriptTriggerKind.Expression:
+            @RenderExpression();
+            break;
         case ScriptTriggerKind.Call:
             <div class="small text-muted">
                 No automatic trigger — this script runs only when another script
@@ -62,7 +66,8 @@
     }
 
     @* ── Hint ──────────────────────────────────────────────────────────── *@
-    @if (_kind is ScriptTriggerKind.Interval or ScriptTriggerKind.ValueChange or ScriptTriggerKind.Conditional)
+    @if (_kind is ScriptTriggerKind.Interval or ScriptTriggerKind.ValueChange
+         or ScriptTriggerKind.Conditional or ScriptTriggerKind.Expression)
     {
         <div class="mt-3 pt-2 border-top small text-muted">@BuildHint()</div>
     }
@@ -244,6 +249,30 @@
         await Emit();
     }
 
+    // ── Expression ─────────────────────────────────────────────────────────
+
+    private RenderFragment RenderExpression() => __builder =>
+    {
+        <label class="form-label small text-uppercase text-muted fw-semibold mb-1">Trigger expression</label>
+        <MonacoEditor Height="120px"
+                      Language="csharp"
+                      ScriptKind="ScriptAnalysis.ScriptKind.Template"
+                      ShowToolbar="false"
+                      Value="@(_model.Expression ?? string.Empty)"
+                      ValueChanged="OnExpressionChanged"
+                      SelfAttributes="@TriggerAttributeMapper.SelfAttributes(AvailableAttributes)"
+                      Children="@TriggerAttributeMapper.Children(AvailableAttributes)" />
+        <div class="form-text">
+            A boolean C# expression — e.g. <code>Attributes["Temperature"] &gt; 80</code>.
+        </div>
+    };
+
+    private async Task OnExpressionChanged(string value)
+    {
+        _model.Expression = value;
+        await Emit();
+    }
+
     // ── Attribute picker (ValueChange + Conditional) ───────────────────────
 
     private RenderFragment RenderAttributePicker(string label) => __builder =>
@@ -315,6 +344,9 @@
                     ? $"Runs when {attr} changes, if {attr} {_model.Operator} {t.ToString("0.###", CultureInfo.InvariantCulture)}."
                     : $"Runs when {attr} changes and meets the configured condition — set a threshold above.",
 
+            ScriptTriggerKind.Expression =>
+                "Runs once each time this expression becomes true.",
+
             _ => string.Empty
         };
     }
diff --git a/src/ScadaLink.CentralUI/Components/Shared/TriggerAttributeMapper.cs b/src/ScadaLink.CentralUI/Components/Shared/TriggerAttributeMapper.cs
new file mode 100644
index 0000000..71874f6
--- /dev/null
+++ b/src/ScadaLink.CentralUI/Components/Shared/TriggerAttributeMapper.cs
@@ -0,0 +1,49 @@
+using ScadaLink.CentralUI.ScriptAnalysis;
+
+namespace ScadaLink.CentralUI.Components.Shared;
+
+/// <summary>
+/// Maps the trigger editors' flattened <see cref="AlarmAttributeChoice"/> list
+/// into the metadata the <see cref="MonacoEditor"/> uses to drive C# completion
+/// inside an expression trigger:
+/// <list type="bullet">
+///   <item>Direct + Inherited choices become <see cref="AttributeShape"/>s,
+///   surfaced under <c>Attributes["..."]</c>.</item>
+///   <item>Composed choices — whose canonical name is dotted, e.g.
+///   <c>CoolingTank.Temp</c> — are grouped by their composition-instance prefix
+///   into <see cref="CompositionContext"/>s, surfaced under
+///   <c>Children["..."].Attributes["..."]</c>.</item>
+/// </list>
+/// </summary>
+public static class TriggerAttributeMapper
+{
+    /// <summary>Direct and inherited attributes, exposed as <c>Attributes["..."]</c>.</summary>
+    public static IReadOnlyList<AttributeShape> SelfAttributes(
+        IReadOnlyList<AlarmAttributeChoice> choices) =>
+        choices
+            .Where(c => c.Source is "Direct" or "Inherited")
+            .Select(c => new AttributeShape(c.CanonicalName, c.DataType))
+            .ToList();
+
+    /// <summary>
+    /// Composed attributes grouped by composition-instance name, exposed as
+    /// <c>Children["X"].Attributes["Y"]</c>. Entries without a dotted prefix
+    /// are skipped (no child scope to attach them to).
+    /// </summary>
+    public static IReadOnlyList<CompositionContext> Children(
+        IReadOnlyList<AlarmAttributeChoice> choices) =>
+        choices
+            .Where(c => c.Source == "Composed" && c.CanonicalName.Contains('.'))
+            .Select(c => new
+            {
+                Child = c.CanonicalName[..c.CanonicalName.IndexOf('.')],
+                Member = c.CanonicalName[(c.CanonicalName.IndexOf('.') + 1)..],
+                c.DataType
+            })
+            .GroupBy(x => x.Child, StringComparer.Ordinal)
+            .Select(g => new CompositionContext(
+                g.Key,
+                g.Select(x => new AttributeShape(x.Member, x.DataType)).ToList(),
+                Array.Empty<ScriptShape>()))
+            .ToList();
+}