Signatures: every light signature names its channel and item through Entity.SetSignature

VisibilitySources holds Signature (channel, strength, item); the eight direct writes
go through the one writer; Visibility stays the sum; SignatureOn(channel) splits it.
VisibilityData gains Key(3) Channel. No number changes. Not yet built or tested at this
commit (verification follows).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Assets/Scripts/ServerShared/Behaviors/ConstantWeapon.cs

@@ -170,7 +170,7 @@ public class ConstantWeapon : Weapon, IProgressBehavior, IEventBehavior, IPowerC
 
             CauseWearDamage(dt);
             AddHeat(Evaluate(_data.Heat) * dt);
-            Entity.VisibilitySources[this] = Evaluate(_data.Visibility);
+            Entity.SetSignature(this, SignatureChannel.LaunchFlash, Evaluate(_data.Visibility), Item);
 
             // Cut 4 (docs/fire-control-cut.md): a beam is a sequence of rolls, not a continuous truth -- one
             // FireControl.Fire per BeamResolveInterval, for that interval's worth of Damage, through the same

Assets/Scripts/ServerShared/Behaviors/InstantWeapon.cs

@@ -277,7 +277,7 @@ public class InstantWeapon : Weapon, IProgressBehavior, IEventBehavior, IPowerCo
             }
             CauseWearDamage(1);
             AddHeat(Heat);
-            Entity.VisibilitySources[this] = Visibility;
+            Entity.SetSignature(this, SignatureChannel.LaunchFlash, Visibility, Item);
         }
         return true;
     }

Assets/Scripts/ServerShared/Behaviors/Radiator.cs

@@ -118,7 +118,7 @@ public class Radiator : Behavior, IAlwaysUpdatedBehavior, IInitializableBehavior
         Emissivity = Evaluate(_data.Emissivity);
         var rad = pow(RadiatorTemperature, ItemManager.GameplaySettings.HeatRadiationExponent) * ItemManager.GameplaySettings.HeatRadiationMultiplier * Emissivity;
         RadiatorTemperature -= rad * delta;
-        Entity.VisibilitySources[this] = rad;
+        Entity.SetSignature(this, SignatureChannel.Thermal, rad, Item);
     }
 
     public void Initialize()

Assets/Scripts/ServerShared/Behaviors/Reflector.cs

@@ -43,7 +43,7 @@ public class Reflector : Behavior
 
     public override bool Execute(float dt)
     {
-        Entity.VisibilitySources[this] = Evaluate(_data.CrossSection) * Entity.Zone.GetLight(Entity.Position.xz);
+        Entity.SetSignature(this, SignatureChannel.Reflection, Evaluate(_data.CrossSection) * Entity.Zone.GetLight(Entity.Position.xz), Item);
         
         return true;
     }

Assets/Scripts/ServerShared/Behaviors/Sensor.cs

@@ -114,7 +114,7 @@ public class Sensor : Behavior, IEventBehavior, IPowerConsumer
         // nothing would ever fill this capacitor; bypass it rather than starving such an instance forever.
         if(_pingCooldown < 0 && (Item == null || _capacitor.TrySpend(_capacitor.Capacity)))
         {
-            Entity.VisibilitySources[this] = Evaluate(_data.PingVisibility);
+            Entity.SetSignature(this, SignatureChannel.Emission, Evaluate(_data.PingVisibility), Item); // interim: emissions-heard replaces this with a range-gated emission
             _pinging = true;
             _pingCooldown = 1;
             _pingLerp = 0;

Assets/Scripts/ServerShared/Behaviors/Thruster.cs

@@ -119,8 +119,8 @@ public class Thruster : Behavior, IPowerConsumer
             Entity.TurnRate += turnRate;
             AddHeat(_input * Evaluate(_data.Heat) * dt);
             var vis = _input * Evaluate(_data.Visibility);
-            if (!Entity.VisibilitySources.ContainsKey(this) || vis > Entity.VisibilitySources[this])
-                Entity.VisibilitySources[this] = vis;
+            if (!Entity.VisibilitySources.TryGetValue(this, out var burn) || vis > burn.Strength)
+                Entity.SetSignature(this, SignatureChannel.DrivePlume, vis, Item);
             return true;
         }
         return false;

Assets/Scripts/ServerShared/Behaviors/Visibility.cs

@@ -15,6 +15,9 @@ public class VisibilityData : BehaviorData
 
     [Inspectable, JsonProperty("visibilityDecay"), Key(2)]  
     public PerformanceStat VisibilityDecay = new PerformanceStat();
+
+    [Inspectable, JsonProperty("channel"), Key(3)]
+    public SignatureChannel Channel = SignatureChannel.Thermal;
     
     public override Behavior CreateInstance(EquippedItem item)
     {
@@ -41,7 +44,7 @@ public class Visibility : Behavior
 
     public override bool Execute(float dt)
     {
-        Entity.VisibilitySources[this] = Evaluate(_data.Visibility);
+        Entity.SetSignature(this, _data.Channel, Evaluate(_data.Visibility), Item);
         return true;
     }
 }

Assets/Scripts/ServerShared/Entity.cs

@@ -85,7 +85,12 @@ public abstract class Entity
     // public Dictionary<Guid, float> Personality = new Dictionary<Guid, float>();
     
     public readonly Dictionary<string, float> Messages = new Dictionary<string, float>();
-    public readonly Dictionary<object, float> VisibilitySources = new Dictionary<object, float>();
+    public readonly Dictionary<object, Signature> VisibilitySources = new Dictionary<object, Signature>();
+
+    // The one writer of VisibilitySources (the decay loop in Update is the one decayer). Every light signature
+    // names its channel and the item that produced it (null for the hull).
+    public void SetSignature(object source, SignatureChannel channel, float strength, EquippedItem item) =>
+        VisibilitySources[source] = new Signature(channel, strength, item);
     public readonly ReactiveDictionary<Entity, float> EntityInfoGathered = new ReactiveDictionary<Entity, float>();
 
     public (List<Weapon> weapons, List<EquippedItem> items)[] WeaponGroups;
@@ -158,7 +163,9 @@ public abstract class Entity
     public ItemManager ItemManager { get; }
     public int AssignedPopulation => PopulationAssignments.Sum(pa => pa.AssignedPopulation);
     public float Mass { get; private set; }
-    public float Visibility => VisibilitySources.Values.Sum();
+    public float Visibility => VisibilitySources.Values.Sum(s => s.Strength);
+    public float SignatureOn(SignatureChannel channel) =>
+        VisibilitySources.Values.Where(s => s.Channel == channel).Sum(s => s.Strength);
 
     public Subject<Entity> IncomingHit = new Subject<Entity>();
     public Subject<(int2 pos, float damage)> ArmorDamage = new Subject<(int2, float)>();
@@ -1423,9 +1430,9 @@ public abstract class Entity
 
         foreach (var v in VisibilitySources.Keys.ToArray())
         {
-            VisibilitySources[v] = decay(VisibilitySources[v], ItemManager.GameplaySettings.VisibilityDecay, delta);
+            VisibilitySources[v] = VisibilitySources[v].WithStrength(decay(VisibilitySources[v].Strength, ItemManager.GameplaySettings.VisibilityDecay, delta));
  
-            if (VisibilitySources[v] < 0.1f) VisibilitySources.Remove(v);
+            if (VisibilitySources[v].Strength < 0.1f) VisibilitySources.Remove(v);
         }
 
         UpdateTemperature(delta);
@@ -1616,7 +1623,7 @@ public abstract class Entity
                 MaxTemp = NewTemperature[v.x, v.y];
         }
 
-        VisibilitySources[this] = radiation;
+        SetSignature(this, SignatureChannel.Thermal, radiation, null);
         var swap = Temperature;
         Temperature = NewTemperature;
         NewTemperature = swap;

Assets/Scripts/ServerShared/Sensing.cs

@@ -0,0 +1,30 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+// Light signatures split by channel (ruling visibility-per-capability-reveal): an observer learns what a ship
+// is by which channel carries the light. Append-only: values are serialized in VisibilityData.
+public enum SignatureChannel
+{
+    Thermal,
+    Reflection,
+    DrivePlume,
+    LaunchFlash,
+    Emission
+}
+
+public readonly struct Signature
+{
+    public readonly SignatureChannel Channel;
+    public readonly float Strength;
+    public readonly EquippedItem Item;
+
+    public Signature(SignatureChannel channel, float strength, EquippedItem item)
+    {
+        Channel = channel;
+        Strength = strength;
+        Item = item;
+    }
+
+    public Signature WithStrength(float strength) => new Signature(Channel, strength, Item);
+}

Assets/Scripts/ServerShared/Sensing.cs.meta

@@ -0,0 +1,11 @@
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