diff --git a/rules/schema/analyze-rule.schema.json b/rules/schema/analyze-rule.schema.json
index d2436725..7c2b3ebf 100644
--- a/rules/schema/analyze-rule.schema.json
+++ b/rules/schema/analyze-rule.schema.json
@@ -81,6 +81,12 @@
           "items": { "$ref": "#/$defs/ruleCondition" },
           "minItems": 1
         },
+        "preconditions": {
+          "type": "array",
+          "description": "Optional device-fact gates evaluated BEFORE conditions. ALL preconditions must pass; if any fails the rule is silently skipped — no result, no UI card. Useful for filtering out hardware/OS profiles where the rule does not apply (e.g. virtual machines).",
+          "items": { "$ref": "#/$defs/rulePrecondition" },
+          "default": []
+        },
         "baseConfidence": {
           "type": "integer",
           "description": "Base confidence score (0-100) when required conditions match.",
@@ -223,6 +229,41 @@
       "required": ["signal", "source"],
       "additionalProperties": false
     },
+    "rulePrecondition": {
+      "type": "object",
+      "description": "A device-fact gate evaluated before conditions. Pure boolean filter — does not contribute to evidence or confidence.",
+      "properties": {
+        "source": {
+          "type": "string",
+          "description": "Currently only event_data is supported.",
+          "enum": ["event_data"],
+          "default": "event_data"
+        },
+        "eventType": {
+          "type": "string",
+          "description": "Event type carrying the field to test (e.g., \"hardware_spec\", \"os_info\", \"tpm_status\")."
+        },
+        "dataField": {
+          "type": "string",
+          "description": "Data field to test. Uses dot notation for nested fields."
+        },
+        "operator": {
+          "type": "string",
+          "description": "Comparison operator. Same vocabulary as conditions.",
+          "enum": ["equals", "not_equals", "contains", "not_contains", "regex", "not_regex", "gt", "lt", "gte", "lte", "exists", "not_exists", "in", "not_in"]
+        },
+        "value": {
+          "type": "string",
+          "description": "Value to compare against. Boolean values are stringified (\"true\"/\"false\")."
+        },
+        "description": {
+          "type": "string",
+          "description": "Human-readable note explaining the intent (e.g., \"skip on virtual machines\")."
+        }
+      },
+      "required": ["source", "operator"],
+      "additionalProperties": false
+    },
     "confidenceFactor": {
       "type": "object",
       "description": "A factor that increases confidence when matched.",
diff --git a/src/Backend/AutopilotMonitor.Functions.Tests/RuleEnginePreconditionTests.cs b/src/Backend/AutopilotMonitor.Functions.Tests/RuleEnginePreconditionTests.cs
new file mode 100644
index 00000000..f6c2a7db
--- /dev/null
+++ b/src/Backend/AutopilotMonitor.Functions.Tests/RuleEnginePreconditionTests.cs
@@ -0,0 +1,248 @@
+using AutopilotMonitor.Functions.Services;
+using AutopilotMonitor.Shared.DataAccess;
+using AutopilotMonitor.Shared.Models;
+using Microsoft.Extensions.Logging.Abstractions;
+using Moq;
+
+namespace AutopilotMonitor.Functions.Tests;
+
+/// <summary>
+/// Pins the precondition gate semantics on <see cref="RuleEngine.EvaluateRule"/>:
+/// preconditions evaluate BEFORE conditions, are AND-combined, and a failing precondition
+/// causes the rule to be silently skipped (no <see cref="RuleResult"/> emitted, no UI card,
+/// no telemetry-visible "rule fired"). Distinct from conditions which decide whether the
+/// rule fires given that it applies.
+/// </summary>
+public class RuleEnginePreconditionTests
+{
+    private const string TenantId  = "a1b2c3d4-e5f6-7890-abcd-ef1234567890";
+    private const string SessionId = "b2c3d4e5-f6a7-8901-bcde-f12345678901";
+
+    /// <summary>
+    /// Baseline: rule with no preconditions and a matching condition fires as expected.
+    /// Confirms the test harness is wired correctly before we exercise gating.
+    /// </summary>
+    [Fact]
+    public async Task NoPreconditions_RuleFires_WhenConditionMatches()
+    {
+        var rule = MakeSecureBootRule(preconditions: new List<RulePrecondition>());
+        var events = new List<EnrollmentEvent>
+        {
+            HardwareSpecEvent(isVirtualMachine: "false"),
+            SecureBootStatusEvent(uefiCA2023Status: "unknown", secureBootEnabled: "true")
+        };
+
+        var outcome = await RunAsync(rule, events);
+
+        Assert.Single(outcome.Results);
+        Assert.Equal(rule.RuleId, outcome.Results[0].RuleId);
+    }
+
+    /// <summary>
+    /// Precondition passes (device is NOT a VM) → rule evaluates conditions and fires.
+    /// </summary>
+    [Fact]
+    public async Task PreconditionPasses_RuleFires()
+    {
+        var rule = MakeSecureBootRule(preconditions: new List<RulePrecondition>
+        {
+            new() { Source = "event_data", EventType = "hardware_spec", DataField = "isVirtualMachine", Operator = "equals", Value = "false" }
+        });
+        var events = new List<EnrollmentEvent>
+        {
+            HardwareSpecEvent(isVirtualMachine: "false"),
+            SecureBootStatusEvent(uefiCA2023Status: "unknown", secureBootEnabled: "true")
+        };
+
+        var outcome = await RunAsync(rule, events);
+
+        Assert.Single(outcome.Results);
+    }
+
+    /// <summary>
+    /// Precondition fails (device IS a VM) → rule is silently skipped. No result row, even
+    /// though the underlying condition would have matched.
+    /// </summary>
+    [Fact]
+    public async Task PreconditionFails_RuleSilentlySkipped()
+    {
+        var rule = MakeSecureBootRule(preconditions: new List<RulePrecondition>
+        {
+            new() { Source = "event_data", EventType = "hardware_spec", DataField = "isVirtualMachine", Operator = "equals", Value = "false" }
+        });
+        var events = new List<EnrollmentEvent>
+        {
+            HardwareSpecEvent(isVirtualMachine: "true"),
+            SecureBootStatusEvent(uefiCA2023Status: "unknown", secureBootEnabled: "true")
+        };
+
+        var outcome = await RunAsync(rule, events);
+
+        Assert.Empty(outcome.Results);
+        // The rule is still in EvaluatedRules (we attempted it) but no result was produced.
+        Assert.Single(outcome.EvaluatedRules);
+    }
+
+    /// <summary>
+    /// AND-semantics: two preconditions, one passes one fails → rule skipped.
+    /// </summary>
+    [Fact]
+    public async Task TwoPreconditions_AnyFailure_SkipsRule()
+    {
+        var rule = MakeSecureBootRule(preconditions: new List<RulePrecondition>
+        {
+            new() { Source = "event_data", EventType = "hardware_spec", DataField = "isVirtualMachine", Operator = "equals", Value = "false" },
+            new() { Source = "event_data", EventType = "os_info", DataField = "edition", Operator = "equals", Value = "Enterprise" }
+        });
+        var events = new List<EnrollmentEvent>
+        {
+            HardwareSpecEvent(isVirtualMachine: "false"), // first precondition passes
+            OsInfoEvent(edition: "Pro"),                  // second precondition fails
+            SecureBootStatusEvent(uefiCA2023Status: "unknown", secureBootEnabled: "true")
+        };
+
+        var outcome = await RunAsync(rule, events);
+
+        Assert.Empty(outcome.Results);
+    }
+
+    /// <summary>
+    /// Missing event type with non-existence operator: a precondition like
+    /// "not_exists hardware_spec.isVirtualMachine" passes when the event isn't there at all.
+    /// This is the "old agent without the new field" path.
+    /// </summary>
+    [Fact]
+    public async Task NotExistsOperator_PassesWhenEventMissing()
+    {
+        var rule = MakeSecureBootRule(preconditions: new List<RulePrecondition>
+        {
+            new() { Source = "event_data", EventType = "hardware_spec", DataField = "isVirtualMachine", Operator = "not_exists", Value = "" }
+        });
+        var events = new List<EnrollmentEvent>
+        {
+            // No hardware_spec event at all
+            SecureBootStatusEvent(uefiCA2023Status: "unknown", secureBootEnabled: "true")
+        };
+
+        var outcome = await RunAsync(rule, events);
+
+        Assert.Single(outcome.Results);
+    }
+
+    /// <summary>
+    /// Missing event with comparison operator (equals, contains, …) → fail-closed (rule skipped).
+    /// We refuse to fire a rule when its precondition can't be assessed; better silent than wrong.
+    /// </summary>
+    [Fact]
+    public async Task EqualsOperator_FailsClosed_WhenEventMissing()
+    {
+        var rule = MakeSecureBootRule(preconditions: new List<RulePrecondition>
+        {
+            new() { Source = "event_data", EventType = "hardware_spec", DataField = "isVirtualMachine", Operator = "equals", Value = "false" }
+        });
+        var events = new List<EnrollmentEvent>
+        {
+            // No hardware_spec event
+            SecureBootStatusEvent(uefiCA2023Status: "unknown", secureBootEnabled: "true")
+        };
+
+        var outcome = await RunAsync(rule, events);
+
+        Assert.Empty(outcome.Results);
+    }
+
+    /// <summary>
+    /// Empty preconditions array (or null) is the legacy default — must behave identically
+    /// to today: condition match → rule fires.
+    /// </summary>
+    [Fact]
+    public async Task EmptyPreconditions_BehavesLikeBefore()
+    {
+        var rule = MakeSecureBootRule(preconditions: null);
+        var events = new List<EnrollmentEvent>
+        {
+            SecureBootStatusEvent(uefiCA2023Status: "unknown", secureBootEnabled: "true")
+        };
+
+        var outcome = await RunAsync(rule, events);
+
+        Assert.Single(outcome.Results);
+    }
+
+    // ===== Helpers =====
+
+    private static AnalyzeRule MakeSecureBootRule(List<RulePrecondition>? preconditions)
+    {
+        return new AnalyzeRule
+        {
+            RuleId = "ANALYZE-SEC-001",
+            Title = "Secure Boot UEFI CA 2023 certificate not deployed",
+            Severity = "warning",
+            Category = "security",
+            Enabled = true,
+            BaseConfidence = 70,
+            ConfidenceThreshold = 40,
+            Preconditions = preconditions ?? new List<RulePrecondition>(),
+            Conditions = new List<RuleCondition>
+            {
+                new() { Signal = "ca2023_not_updated", Source = "event_data", EventType = "secureboot_status", DataField = "uefiCA2023Status", Operator = "not_equals", Value = "Updated", Required = true },
+                new() { Signal = "secureboot_enabled", Source = "event_data", EventType = "secureboot_status", DataField = "uefiSecureBootEnabled", Operator = "equals", Value = "true", Required = true }
+            },
+            Explanation = "test"
+        };
+    }
+
+    private static EnrollmentEvent HardwareSpecEvent(string isVirtualMachine) => new()
+    {
+        EventId = Guid.NewGuid().ToString(),
+        TenantId = TenantId,
+        SessionId = SessionId,
+        EventType = "hardware_spec",
+        Timestamp = DateTime.UtcNow,
+        Sequence = 1,
+        Data = new Dictionary<string, object> { ["isVirtualMachine"] = isVirtualMachine }
+    };
+
+    private static EnrollmentEvent OsInfoEvent(string edition) => new()
+    {
+        EventId = Guid.NewGuid().ToString(),
+        TenantId = TenantId,
+        SessionId = SessionId,
+        EventType = "os_info",
+        Timestamp = DateTime.UtcNow,
+        Sequence = 2,
+        Data = new Dictionary<string, object> { ["edition"] = edition }
+    };
+
+    private static EnrollmentEvent SecureBootStatusEvent(string uefiCA2023Status, string secureBootEnabled) => new()
+    {
+        EventId = Guid.NewGuid().ToString(),
+        TenantId = TenantId,
+        SessionId = SessionId,
+        EventType = "secureboot_status",
+        Timestamp = DateTime.UtcNow,
+        Sequence = 3,
+        Data = new Dictionary<string, object>
+        {
+            ["uefiCA2023Status"] = uefiCA2023Status,
+            ["uefiSecureBootEnabled"] = secureBootEnabled
+        }
+    };
+
+    private static async Task<AnalysisOutcome> RunAsync(AnalyzeRule rule, List<EnrollmentEvent> events)
+    {
+        var ruleRepo = new Mock<IRuleRepository>();
+        ruleRepo.Setup(r => r.GetAnalyzeRulesAsync("global")).ReturnsAsync(new List<AnalyzeRule> { rule });
+        ruleRepo.Setup(r => r.GetAnalyzeRulesAsync(TenantId)).ReturnsAsync(new List<AnalyzeRule>());
+        ruleRepo.Setup(r => r.GetRuleStatesAsync(It.IsAny<string>())).ReturnsAsync(new Dictionary<string, RuleState>());
+        ruleRepo.Setup(r => r.GetRuleResultsAsync(It.IsAny<string>(), It.IsAny<string>())).ReturnsAsync(new List<RuleResult>());
+
+        var sessionRepo = new Mock<ISessionRepository>();
+        sessionRepo.Setup(s => s.GetSessionEventsAsync(TenantId, SessionId, It.IsAny<int>())).ReturnsAsync(events);
+
+        var ruleService = new AnalyzeRuleService(ruleRepo.Object, NullLogger<AnalyzeRuleService>.Instance);
+        var engine = new RuleEngine(ruleService, ruleRepo.Object, sessionRepo.Object, NullLogger<RuleEnginePreconditionTests>.Instance);
+
+        return await engine.AnalyzeSessionAsync(TenantId, SessionId);
+    }
+}
diff --git a/src/Backend/AutopilotMonitor.Functions/Services/RuleEngine.ConditionEvaluators.cs b/src/Backend/AutopilotMonitor.Functions/Services/RuleEngine.ConditionEvaluators.cs
index 71298255..e7aeb725 100644
--- a/src/Backend/AutopilotMonitor.Functions/Services/RuleEngine.ConditionEvaluators.cs
+++ b/src/Backend/AutopilotMonitor.Functions/Services/RuleEngine.ConditionEvaluators.cs
@@ -11,6 +11,52 @@ namespace AutopilotMonitor.Functions.Services
     /// </summary>
     public partial class RuleEngine
     {
+        /// <summary>
+        /// Evaluates a single precondition (AND-semantics gate, silent skip on failure).
+        ///
+        /// Semantics:
+        ///   - Source must be <c>event_data</c> (the only currently supported source).
+        ///   - <c>exists</c>: passes when at least one event of <see cref="RulePrecondition.EventType"/>
+        ///     carries a non-null value at <see cref="RulePrecondition.DataField"/>.
+        ///   - <c>not_exists</c>: passes when no event of that type carries the field
+        ///     (also passes when the event type itself is absent — common case for "no VM detected").
+        ///   - All other operators: pass when at least one event of that type matches the
+        ///     <see cref="RulePrecondition.Operator"/> against <see cref="RulePrecondition.Value"/>.
+        ///     Missing event type or missing field → fail closed (rule skipped).
+        /// </summary>
+        private bool EvaluatePrecondition(RulePrecondition precondition, List<EnrollmentEvent> events)
+        {
+            if (!string.Equals(precondition.Source, "event_data", StringComparison.OrdinalIgnoreCase))
+            {
+                _logger.LogWarning("Unsupported precondition source '{Source}' — failing closed", precondition.Source);
+                return false;
+            }
+
+            if (string.IsNullOrEmpty(precondition.EventType) || string.IsNullOrEmpty(precondition.DataField))
+                return false;
+
+            var matchingEvents = events.Where(e => MatchesEventType(e, precondition.EventType)).ToList();
+            var op = precondition.Operator?.ToLowerInvariant() ?? string.Empty;
+
+            if (op == "not_exists")
+            {
+                if (matchingEvents.Count == 0) return true;
+                return matchingEvents.All(e => string.IsNullOrEmpty(GetDataFieldValue(e, precondition.DataField)));
+            }
+
+            if (matchingEvents.Count == 0)
+                return false;
+
+            if (op == "exists")
+                return matchingEvents.Any(e => !string.IsNullOrEmpty(GetDataFieldValue(e, precondition.DataField)));
+
+            return matchingEvents.Any(e =>
+            {
+                var fieldValue = GetDataFieldValue(e, precondition.DataField);
+                return fieldValue != null && MatchesOperator(fieldValue, precondition.Operator ?? string.Empty, precondition.Value ?? string.Empty);
+            });
+        }
+
         private (bool matched, object evidence) EvaluateCondition(RuleCondition condition, List<EnrollmentEvent> events)
         {
             switch (condition.Source)
diff --git a/src/Backend/AutopilotMonitor.Functions/Services/RuleEngine.cs b/src/Backend/AutopilotMonitor.Functions/Services/RuleEngine.cs
index fc208fcd..a7c7f47b 100644
--- a/src/Backend/AutopilotMonitor.Functions/Services/RuleEngine.cs
+++ b/src/Backend/AutopilotMonitor.Functions/Services/RuleEngine.cs
@@ -222,6 +222,23 @@ namespace AutopilotMonitor.Functions.Services
         /// </summary>
         private RuleResult? EvaluateRule(AnalyzeRule rule, List<EnrollmentEvent> events)
         {
+            // Preconditions gate (AND-semantics, silent skip): if any precondition fails the
+            // rule is not evaluated at all — no result row, no UI card. Distinct from
+            // conditions, which decide whether the rule fires given that it applies.
+            if (rule.Preconditions != null && rule.Preconditions.Count > 0)
+            {
+                foreach (var pre in rule.Preconditions)
+                {
+                    if (!EvaluatePrecondition(pre, events))
+                    {
+                        _logger.LogDebug(
+                            "Rule {RuleId} skipped by precondition (eventType={EventType}, field={Field}, op={Op}, value={Value})",
+                            rule.RuleId, pre.EventType, pre.DataField, pre.Operator, pre.Value);
+                        return null;
+                    }
+                }
+            }
+
             var matchedConditions = new Dictionary<string, object>();
             int confidence = rule.BaseConfidence;
             bool allRequiredMet = true;
diff --git a/src/Backend/AutopilotMonitor.Functions/Services/TableStorageService.Rules.cs b/src/Backend/AutopilotMonitor.Functions/Services/TableStorageService.Rules.cs
index 3091551e..b062184f 100644
--- a/src/Backend/AutopilotMonitor.Functions/Services/TableStorageService.Rules.cs
+++ b/src/Backend/AutopilotMonitor.Functions/Services/TableStorageService.Rules.cs
@@ -361,6 +361,7 @@ namespace AutopilotMonitor.Functions.Services
                     ["IsBuiltIn"] = rule.IsBuiltIn,
                     ["IsCommunity"] = rule.IsCommunity,
                     ["Trigger"] = rule.Trigger ?? "single",
+                    ["PreconditionsJson"] = JsonConvert.SerializeObject(rule.Preconditions ?? new List<RulePrecondition>()),
                     ["ConditionsJson"] = JsonConvert.SerializeObject(rule.Conditions ?? new List<RuleCondition>()),
                     ["BaseConfidence"] = rule.BaseConfidence,
                     ["ConfidenceFactorsJson"] = JsonConvert.SerializeObject(rule.ConfidenceFactors ?? new List<ConfidenceFactor>()),
@@ -487,6 +488,7 @@ namespace AutopilotMonitor.Functions.Services
                 IsBuiltIn = entity.GetBoolean("IsBuiltIn") ?? false,
                 IsCommunity = entity.GetBoolean("IsCommunity") ?? false,
                 Trigger = entity.GetString("Trigger") ?? "single",
+                Preconditions = DeserializeJson<List<RulePrecondition>>(entity.GetString("PreconditionsJson")),
                 Conditions = DeserializeJson<List<RuleCondition>>(entity.GetString("ConditionsJson")),
                 BaseConfidence = entity.GetInt32("BaseConfidence") ?? 50,
                 ConfidenceFactors = DeserializeJson<List<ConfidenceFactor>>(entity.GetString("ConfidenceFactorsJson")),
diff --git a/src/Shared/AutopilotMonitor.Shared/Models/Rules/AnalyzeRule.cs b/src/Shared/AutopilotMonitor.Shared/Models/Rules/AnalyzeRule.cs
index ff9d20d8..19e2c830 100644
--- a/src/Shared/AutopilotMonitor.Shared/Models/Rules/AnalyzeRule.cs
+++ b/src/Shared/AutopilotMonitor.Shared/Models/Rules/AnalyzeRule.cs
@@ -69,6 +69,13 @@ namespace AutopilotMonitor.Shared.Models
 
         // ===== MATCHING CONDITIONS =====
 
+        /// <summary>
+        /// Optional device-fact gates evaluated BEFORE conditions. ALL preconditions must pass;
+        /// if any fails the rule is silently skipped — no result, no UI card. Used to filter out
+        /// hardware/OS profiles where a rule does not apply (e.g. "skip on virtual machines").
+        /// </summary>
+        public List<RulePrecondition> Preconditions { get; set; } = new List<RulePrecondition>();
+
         /// <summary>
         /// Conditions that must be evaluated against the event stream
         /// All required conditions must match for the rule to fire
@@ -255,6 +262,47 @@ namespace AutopilotMonitor.Shared.Models
         public string EventAFilterValue { get; set; } = default!;
     }
 
+    /// <summary>
+    /// A device-fact gate evaluated before a rule's conditions. Pure boolean filter —
+    /// does not contribute to evidence or confidence. When any precondition on a rule
+    /// fails, the rule is silently skipped (no result emitted). Currently only
+    /// <c>event_data</c> source is supported.
+    /// </summary>
+    public class RulePrecondition
+    {
+        /// <summary>
+        /// Source of the fact. Currently only <c>event_data</c>.
+        /// </summary>
+        public string Source { get; set; } = "event_data";
+
+        /// <summary>
+        /// Event type carrying the field to test (e.g., <c>hardware_spec</c>, <c>os_info</c>).
+        /// </summary>
+        public string EventType { get; set; } = default!;
+
+        /// <summary>
+        /// Data field to test (dot notation supported for nested fields).
+        /// </summary>
+        public string DataField { get; set; } = default!;
+
+        /// <summary>
+        /// Comparison operator. Same vocabulary as <see cref="RuleCondition.Operator"/>
+        /// minus the count_/correlation-specific operators.
+        /// </summary>
+        public string Operator { get; set; } = default!;
+
+        /// <summary>
+        /// Value to compare against. Boolean values are stringified (<c>"true"</c>/<c>"false"</c>).
+        /// </summary>
+        public string Value { get; set; } = default!;
+
+        /// <summary>
+        /// Optional human-readable note explaining the intent
+        /// (e.g., <c>"skip on virtual machines"</c>). Not evaluated.
+        /// </summary>
+        public string? Description { get; set; }
+    }
+
     /// <summary>
     /// A factor that increases confidence when matched
     /// </summary>
diff --git a/src/Web/autopilot-monitor-web/app/analyze-rules/components/AnalyzeRuleCard.tsx b/src/Web/autopilot-monitor-web/app/analyze-rules/components/AnalyzeRuleCard.tsx
index 2d55a71f..3f28a54b 100644
--- a/src/Web/autopilot-monitor-web/app/analyze-rules/components/AnalyzeRuleCard.tsx
+++ b/src/Web/autopilot-monitor-web/app/analyze-rules/components/AnalyzeRuleCard.tsx
@@ -192,6 +192,27 @@ export default function AnalyzeRuleCard({
             <p className="text-sm text-gray-600 leading-relaxed">{rule.description}</p>
           </div>
 
+          {rule.preconditions && rule.preconditions.length > 0 && (
+            <div>
+              <h4 className="text-sm font-semibold text-gray-700 mb-2">Preconditions ({rule.preconditions.length})</h4>
+              <p className="text-xs text-gray-500 mb-2">Rule is silently skipped if any of these fails.</p>
+              <div className="space-y-2">
+                {rule.preconditions.map((pre, idx) => (
+                  <div key={idx} className="bg-amber-50 border border-amber-200 rounded-lg p-3 text-sm">
+                    <p className="text-gray-700">
+                      <span className="text-gray-600 font-medium">Event:</span> {pre.eventType}
+                      {pre.dataField && (<span> | <span className="text-gray-600 font-medium">Field:</span> <code className="bg-amber-100 px-1 rounded text-xs">{pre.dataField}</code></span>)}
+                      {" "}
+                      <code className="bg-amber-100 px-1 rounded text-xs">{pre.operator}</code>
+                      {pre.value !== "" && (<> <code className="bg-amber-100 px-1 rounded text-xs">{pre.value}</code></>)}
+                    </p>
+                    {pre.description && (<p className="text-xs text-gray-500 italic mt-1">{pre.description}</p>)}
+                  </div>
+                ))}
+              </div>
+            </div>
+          )}
+
           {rule.conditions.length > 0 && (
             <div>
               <h4 className="text-sm font-semibold text-gray-700 mb-2">Conditions ({rule.conditions.length})</h4>
diff --git a/src/Web/autopilot-monitor-web/app/analyze-rules/components/AnalyzeRuleFormFields.tsx b/src/Web/autopilot-monitor-web/app/analyze-rules/components/AnalyzeRuleFormFields.tsx
index 355a6a4b..0bd82c13 100644
--- a/src/Web/autopilot-monitor-web/app/analyze-rules/components/AnalyzeRuleFormFields.tsx
+++ b/src/Web/autopilot-monitor-web/app/analyze-rules/components/AnalyzeRuleFormFields.tsx
@@ -1,9 +1,9 @@
 "use client";
 
 import {
-  RuleForm, RuleCondition,
-  CATEGORIES, SEVERITIES, TRIGGERS, OPERATORS, SOURCES,
-  EMPTY_CONDITION, EMPTY_FACTOR,
+  RuleForm, RuleCondition, RulePrecondition,
+  CATEGORIES, SEVERITIES, TRIGGERS, OPERATORS, SOURCES, PRECONDITION_OPERATORS,
+  EMPTY_CONDITION, EMPTY_FACTOR, EMPTY_PRECONDITION,
 } from "../types";
 
 interface AnalyzeRuleFormFieldsProps {
@@ -63,6 +63,47 @@ export default function AnalyzeRuleFormFields({ form, setForm, showRuleId, exist
         </div>
       </div>
 
+      {/* Preconditions (device-fact gates evaluated BEFORE conditions) */}
+      <div>
+        <div className="flex items-center justify-between mb-2">
+          <div>
+            <label className="block text-sm font-semibold text-gray-700">Preconditions</label>
+            <p className="text-xs text-gray-500">Optional. Rule is silently skipped (no result) when ANY precondition fails. Useful e.g. to skip on virtual machines.</p>
+          </div>
+          <button type="button" onClick={() => setForm({ ...form, preconditions: [...form.preconditions, { ...EMPTY_PRECONDITION }] })} className="text-xs text-indigo-600 hover:text-indigo-800 font-medium">+ Add Precondition</button>
+        </div>
+        {form.preconditions.length === 0 ? (
+          <p className="text-xs text-gray-400 italic">No preconditions. Rule applies to every device.</p>
+        ) : (
+          <div className="space-y-2">
+            {form.preconditions.map((pre, idx) => {
+              const updatePre = (patch: Partial<RulePrecondition>) => {
+                const p = [...form.preconditions];
+                p[idx] = { ...p[idx], ...patch };
+                setForm({ ...form, preconditions: p });
+              };
+              return (
+                <div key={idx} className="border border-amber-200 bg-amber-50 rounded-lg p-3 space-y-2">
+                  <div className="flex items-center justify-between">
+                    <span className="text-xs font-medium text-amber-700">Precondition {idx + 1}</span>
+                    <button type="button" onClick={() => setForm({ ...form, preconditions: form.preconditions.filter((_, i) => i !== idx) })} className="text-xs text-red-500 hover:text-red-700">Remove</button>
+                  </div>
+                  <div className="grid grid-cols-1 sm:grid-cols-4 gap-2">
+                    <input type="text" value={pre.eventType} onChange={(e) => updatePre({ eventType: e.target.value })} placeholder="Event type (e.g. hardware_spec)" autoComplete="off" className="px-3 py-1.5 border border-amber-300 rounded text-sm text-gray-900 placeholder-gray-400 focus:outline-none focus:ring-1 focus:ring-amber-500" />
+                    <input type="text" value={pre.dataField} onChange={(e) => updatePre({ dataField: e.target.value })} placeholder="Data field (e.g. isVirtualMachine)" autoComplete="off" className="px-3 py-1.5 border border-amber-300 rounded text-sm text-gray-900 placeholder-gray-400 focus:outline-none focus:ring-1 focus:ring-amber-500" />
+                    <select value={pre.operator} onChange={(e) => updatePre({ operator: e.target.value })} className="px-3 py-1.5 border border-amber-300 rounded text-sm text-gray-900 bg-white focus:outline-none focus:ring-1 focus:ring-amber-500">
+                      {PRECONDITION_OPERATORS.map((o) => (<option key={o} value={o}>{o}</option>))}
+                    </select>
+                    <input type="text" value={pre.value} onChange={(e) => updatePre({ value: e.target.value })} placeholder="Value (e.g. false)" autoComplete="off" className="px-3 py-1.5 border border-amber-300 rounded text-sm text-gray-900 placeholder-gray-400 focus:outline-none focus:ring-1 focus:ring-amber-500" />
+                  </div>
+                  <input type="text" value={pre.description ?? ""} onChange={(e) => updatePre({ description: e.target.value })} placeholder="Description (optional, e.g. 'skip on VMs')" autoComplete="off" className="w-full px-3 py-1.5 border border-amber-200 rounded text-sm text-gray-700 placeholder-gray-400 bg-white focus:outline-none focus:ring-1 focus:ring-amber-500" />
+                </div>
+              );
+            })}
+          </div>
+        )}
+      </div>
+
       {/* Conditions */}
       <div>
         <div className="flex items-center justify-between mb-2">
diff --git a/src/Web/autopilot-monitor-web/app/analyze-rules/page.tsx b/src/Web/autopilot-monitor-web/app/analyze-rules/page.tsx
index 83bdee4c..dc9f126c 100644
--- a/src/Web/autopilot-monitor-web/app/analyze-rules/page.tsx
+++ b/src/Web/autopilot-monitor-web/app/analyze-rules/page.tsx
@@ -261,6 +261,7 @@ export default function AnalyzeRulesPage() {
       explanation: form.explanation.trim(),
       baseConfidence: form.baseConfidence,
       confidenceThreshold: form.confidenceThreshold,
+      preconditions: form.preconditions.filter(p => p.eventType.trim() && p.operator.trim()),
       conditions: form.conditions.filter(c => c.signal.trim()),
       confidenceFactors: form.confidenceFactors.filter(f => f.signal.trim()),
       remediation: form.remediation.filter(r => r.title.trim()),
@@ -310,6 +311,7 @@ export default function AnalyzeRulesPage() {
       explanation: form.explanation.trim(),
       baseConfidence: form.baseConfidence,
       confidenceThreshold: form.confidenceThreshold,
+      preconditions: form.preconditions.filter(p => p.eventType.trim() && p.operator.trim()),
       conditions: form.conditions.filter(c => c.signal.trim()),
       confidenceFactors: form.confidenceFactors.filter(f => f.signal.trim()),
       remediation: form.remediation.filter(r => r.title.trim()),
diff --git a/src/Web/autopilot-monitor-web/app/analyze-rules/types.ts b/src/Web/autopilot-monitor-web/app/analyze-rules/types.ts
index 0adb8025..4a7351a4 100644
--- a/src/Web/autopilot-monitor-web/app/analyze-rules/types.ts
+++ b/src/Web/autopilot-monitor-web/app/analyze-rules/types.ts
@@ -31,6 +31,15 @@ export interface RuleCondition {
   eventAFilterValue?: string;
 }
 
+export interface RulePrecondition {
+  source: string;
+  eventType: string;
+  dataField: string;
+  operator: string;
+  value: string;
+  description?: string;
+}
+
 export interface TemplateVariable {
   name: string;
   label: string;
@@ -53,6 +62,7 @@ export interface AnalyzeRule {
   enabled: boolean;
   isBuiltIn: boolean;
   isCommunity: boolean;
+  preconditions?: RulePrecondition[];
   conditions: RuleCondition[];
   baseConfidence: number;
   confidenceFactors: ConfidenceFactor[];
@@ -81,6 +91,7 @@ export interface RuleForm {
   explanation: string;
   baseConfidence: number;
   confidenceThreshold: number;
+  preconditions: RulePrecondition[];
   conditions: RuleCondition[];
   confidenceFactors: ConfidenceFactor[];
   remediation: RemediationStep[];
@@ -92,6 +103,7 @@ export const SEVERITIES = ["info", "warning", "high", "critical"] as const;
 export const TRIGGERS = ["single", "correlation"] as const;
 export const OPERATORS = ["equals", "not_equals", "contains", "not_contains", "regex", "not_regex", "gt", "lt", "gte", "lte", "exists", "not_exists", "count_gte", "count_per_group_gte", "in", "not_in"] as const;
 export const SOURCES = ["event_type", "event_data", "phase_duration", "event_count", "event_correlation"] as const;
+export const PRECONDITION_OPERATORS = ["equals", "not_equals", "contains", "not_contains", "regex", "not_regex", "gt", "lt", "gte", "lte", "exists", "not_exists", "in", "not_in"] as const;
 
 export const SEVERITY_COLORS: Record<string, { bg: string; text: string; border: string; dot: string }> = {
   critical: { bg: "bg-red-100", text: "text-red-800", border: "border-red-300", dot: "bg-red-500" },
@@ -139,6 +151,15 @@ export const EMPTY_FACTOR: ConfidenceFactor = {
   weight: 10,
 };
 
+export const EMPTY_PRECONDITION: RulePrecondition = {
+  source: "event_data",
+  eventType: "",
+  dataField: "",
+  operator: "equals",
+  value: "",
+  description: "",
+};
+
 export const EMPTY_FORM: RuleForm = {
   ruleId: "",
   title: "",
@@ -149,6 +170,7 @@ export const EMPTY_FORM: RuleForm = {
   explanation: "",
   baseConfidence: 50,
   confidenceThreshold: 40,
+  preconditions: [],
   conditions: [{ ...EMPTY_CONDITION }],
   confidenceFactors: [],
   remediation: [],
@@ -166,6 +188,7 @@ export function ruleToForm(rule: AnalyzeRule): RuleForm {
     explanation: rule.explanation || "",
     baseConfidence: rule.baseConfidence,
     confidenceThreshold: rule.confidenceThreshold,
+    preconditions: (rule.preconditions ?? []).map(p => ({ ...p })),
     conditions: rule.conditions.length > 0 ? rule.conditions.map(c => ({ ...c })) : [{ ...EMPTY_CONDITION }],
     confidenceFactors: rule.confidenceFactors.map(f => ({ ...f })),
     remediation: rule.remediation.map(r => ({ title: r.title, steps: [...r.steps] })),