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src/Policy/StellaOps.Policy.Engine/AdvisoryAI/AdvisoryAiKnobsService.cs

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+using System.Security.Cryptography;
+using System.Text;
+using System.Text.Json;
+
+namespace StellaOps.Policy.Engine.AdvisoryAI;
+
+/// <summary>
+/// In-memory store for Advisory AI knobs (POLICY-ENGINE-31-001).
+/// </summary>
+internal sealed class AdvisoryAiKnobsService
+{
+    private readonly TimeProvider _timeProvider;
+    private readonly object _lock = new();
+    private AdvisoryAiKnobsProfile _current;
+
+    public AdvisoryAiKnobsService(TimeProvider timeProvider)
+    {
+        _timeProvider = timeProvider ?? throw new ArgumentNullException(nameof(timeProvider));
+        _current = BuildProfile(DefaultKnobs());
+    }
+
+    public AdvisoryAiKnobsProfile Get() => _current;
+
+    public AdvisoryAiKnobsProfile Set(IReadOnlyList<AdvisoryAiKnob> knobs)
+    {
+        var normalized = Normalize(knobs);
+        var profile = BuildProfile(normalized);
+        lock (_lock)
+        {
+            _current = profile;
+        }
+
+        return profile;
+    }
+
+    private AdvisoryAiKnobsProfile BuildProfile(IReadOnlyList<AdvisoryAiKnob> knobs)
+    {
+        var json = JsonSerializer.Serialize(knobs, new JsonSerializerOptions
+        {
+            PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+            WriteIndented = false
+        });
+
+        var hash = Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(json)));
+        return new AdvisoryAiKnobsProfile(knobs, hash);
+    }
+
+    private IReadOnlyList<AdvisoryAiKnob> Normalize(IReadOnlyList<AdvisoryAiKnob> knobs)
+    {
+        var normalized = knobs
+            .Where(k => !string.IsNullOrWhiteSpace(k.Name))
+            .Select(k => new AdvisoryAiKnob(
+                Name: k.Name.Trim().ToLowerInvariant(),
+                DefaultValue: k.DefaultValue,
+                Min: k.Min,
+                Max: k.Max,
+                Step: k.Step <= 0 ? 0.001m : k.Step,
+                Description: string.IsNullOrWhiteSpace(k.Description) ? string.Empty : k.Description.Trim()))
+            .OrderBy(k => k.Name, StringComparer.Ordinal)
+            .ToList();
+
+        return normalized;
+    }
+
+    private static IReadOnlyList<AdvisoryAiKnob> DefaultKnobs() =>
+        new[]
+        {
+            new AdvisoryAiKnob("ai_signal_weight", 1.0m, 0m, 2m, 0.01m, "Weight applied to AI signals"),
+            new AdvisoryAiKnob("reachability_boost", 0.2m, 0m, 1m, 0.01m, "Boost when asset is reachable"),
+            new AdvisoryAiKnob("time_decay_half_life_days", 30m, 1m, 365m, 1m, "Half-life for decay"),
+            new AdvisoryAiKnob("evidence_freshness_threshold_hours", 72m, 1m, 720m, 1m, "Max evidence age")
+        };
+}