feat(simulation): integrate knowledge graph into observer snapshot (#366)

VisibleEntity now carries relationship state (D-033 entity color) and
observation type (Visible vs Remembered). compute_observer_snapshot
queries the player's KnowledgeGraph to overlay relationship data on
visible entities and include remembered (not-in-LOS) entities as fog
ghosts at their last known position. Regenerated msgpack fixtures.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/bridge/mod.rs

@@ -89,6 +89,8 @@ pub fn generate_snapshot(
             z,
             kind,
             visibility: VisibilitySector::Forward,
+            relationship: RelationshipState::Unknown,
+            observation: EntityVisibility::Visible,
         });
     }
 

server/src/bridge/types.rs

@@ -5,6 +5,7 @@
 use bevy_ecs::prelude::*;
 use serde::{Deserialize, Serialize};
 
+pub use crate::knowledge::types::{EntityVisibility, KnowledgeConfidence, RelationshipState};
 pub use crate::simulation::time::DayPhase;
 
 /// The ONLY data structure crossing the client-server boundary (D-020)
@@ -95,6 +96,14 @@ pub struct VisibleEntity {
     pub kind: EntityKind,
     /// Which vision cone sector this entity falls in (D-015)
     pub visibility: VisibilitySector,
+    /// Relationship state for D-033 entity color rendering.
+    /// Unknown for entities not yet in the knowledge graph.
+    #[serde(default)]
+    pub relationship: RelationshipState,
+    /// Whether this entity is currently visible or remembered from knowledge.
+    /// Visible = in LOS right now. Remembered = known but not in LOS.
+    #[serde(default)]
+    pub observation: EntityVisibility,
 }
 
 /// Category of visible entity

server/src/knowledge/types.rs

@@ -205,7 +205,7 @@ impl Default for DecayThresholds {
 
 /// How an entity appears in the observer snapshot.
 /// Extends VisibleEntity for knowledge-based rendering.
-#[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub enum EntityVisibility {
     /// Currently in line of sight.
     Visible,
@@ -215,3 +215,9 @@ pub enum EntityVisibility {
         age_ticks: u64,
     },
 }
+
+impl Default for EntityVisibility {
+    fn default() -> Self {
+        Self::Visible
+    }
+}

server/src/perception/observer.rs

@@ -8,6 +8,7 @@ use bevy_ecs::prelude::*;
 use std::collections::HashSet;
 
 use crate::bridge::types::*;
+use crate::knowledge::{EntityRegistry, KnowledgeGraph};
 use crate::perception::shadowcast::compute_fov;
 use crate::perception::vision_cone::{apply_vision_cone, Facing, VisionConeConfig};
 use crate::simulation::movement::{PlayerCharacter, TilePosition, WalkabilityMap};
@@ -20,7 +21,8 @@ use crate::simulation::time::SimulationTime;
 pub fn compute_observer_snapshot(
     time: Res<SimulationTime>,
     walkability: Res<WalkabilityMap>,
-    observer_query: Query<(&TilePosition, Option<&Facing>), With<PlayerCharacter>>,
+    registry: Res<EntityRegistry>,
+    observer_query: Query<(&TilePosition, Option<&Facing>, &KnowledgeGraph), With<PlayerCharacter>>,
     all_entities: Query<(
         Entity,
         &TilePosition,
@@ -29,7 +31,7 @@ pub fn compute_observer_snapshot(
     )>,
     mut buffer: ResMut<SnapshotBuffer>,
 ) {
-    let Ok((observer_pos, facing_opt)) = observer_query.single() else {
+    let Ok((observer_pos, facing_opt, observer_kg)) = observer_query.single() else {
         return;
     };
 
@@ -74,8 +76,9 @@ pub fn compute_observer_snapshot(
         .map(|&(x, y, sector)| ((x, y), sector))
         .collect();
 
-    // Step 5: Filter entities by visibility
+    // Step 5: Filter entities by visibility, overlay knowledge
     let mut entities = Vec::new();
+    let mut visible_entity_bits: HashSet<u64> = HashSet::new();
     for (entity, pos, is_player, is_npc) in all_entities.iter() {
         // Different z-level: not visible
         if pos.z != z {
@@ -101,17 +104,72 @@ pub fn compute_observer_snapshot(
             .copied()
             .unwrap_or(VisibilitySector::Peripheral);
 
+        // Look up relationship from knowledge graph (D-033 entity color)
+        let relationship = if is_player.is_some() {
+            RelationshipState::Known // Self
+        } else if let Some(stable_id) = registry.to_stable(entity) {
+            observer_kg.relationship_with(&stable_id)
+        } else {
+            RelationshipState::Unknown
+        };
+
+        visible_entity_bits.insert(entity.to_bits());
         entities.push(VisibleEntity {
-            entity_id: entity.to_bits(), // Temporary: use entity.to_bits() until #362 StableEntityId
+            entity_id: entity.to_bits(),
             x: rx,
             y: ry,
             z: rz,
             kind,
             visibility: sector,
+            relationship,
+            observation: EntityVisibility::Visible,
         });
     }
 
-    // Step 6: Build GameTime from SimulationTime
+    // Step 6: Add remembered entities from knowledge graph (#366)
+    // Entities the observer knows about but can't currently see.
+    for (stable_id, knowledge) in observer_kg.known_entities_iter() {
+        // Skip if currently visible (already in the entity list)
+        if let Some(entity) = registry.to_entity(stable_id) {
+            if visible_entity_bits.contains(&entity.to_bits()) {
+                continue;
+            }
+        }
+
+        // Skip if no known position (never directly observed)
+        let Some(position) = knowledge.last_known_position else {
+            continue;
+        };
+
+        // Direct confidence means the entity should be in LOS — if it isn't,
+        // that's a transient data inconsistency. Skip rather than show a ghost.
+        if knowledge.confidence == KnowledgeConfidence::Direct {
+            continue;
+        }
+
+        let (rx, ry, rz) = position.to_render_coords();
+        let age_ticks = time.tick.saturating_sub(knowledge.last_observed_tick);
+        let entity_id = registry
+            .to_entity(stable_id)
+            .map(|e| e.to_bits())
+            .unwrap_or(stable_id.0);
+
+        entities.push(VisibleEntity {
+            entity_id,
+            x: rx,
+            y: ry,
+            z: rz,
+            kind: EntityKind::Npc, // Remembered entities are NPCs (only NPCs are tracked)
+            visibility: VisibilitySector::Forward, // Not meaningful for remembered entities
+            relationship: knowledge.relationship,
+            observation: EntityVisibility::Remembered {
+                confidence: knowledge.confidence,
+                age_ticks,
+            },
+        });
+    }
+
+    // Step 7: Build GameTime from SimulationTime
     let game_time = GameTime {
         day: time.day(),
         time_of_day: time.time_of_day_minutes(),
@@ -120,13 +178,14 @@ pub fn compute_observer_snapshot(
     };
 
     tracing::trace!(
-        "compute_observer_snapshot: tick={}, entities={}, tiles={}",
+        "compute_observer_snapshot: tick={}, visible={}, remembered={}, tiles={}",
         time.tick,
-        entities.len(),
+        visible_entity_bits.len(),
+        entities.len() - visible_entity_bits.len(),
         visible_tiles.len(),
     );
 
-    // Step 7: Assemble v2 snapshot
+    // Step 8: Assemble snapshot
     buffer.snapshot = Some(ObserverSnapshot {
         version: 2,
         tick: time.tick,
@@ -140,15 +199,17 @@ pub fn compute_observer_snapshot(
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::knowledge::{EntityRegistry, KnowledgeGraph};
     use crate::perception::vision_cone::Facing;
     use bevy_ecs::world::World;
 
-    /// Helper: set up a test world with player and walkability map
+    /// Helper: set up a test world with player, walkability map, and knowledge resources
     fn setup_world(width: i32, height: i32) -> World {
         let mut world = World::new();
         world.insert_resource(SimulationTime::default());
         world.insert_resource(WalkabilityMap::new(width, height, 1));
         world.init_resource::<SnapshotBuffer>();
+        world.init_resource::<EntityRegistry>();
         world
     }
 
@@ -159,6 +220,7 @@ mod tests {
             PlayerCharacter,
             TilePosition::new(16, 16, 0),
             Facing::default(),
+            KnowledgeGraph::new(),
         ));
 
         let mut schedule = bevy_ecs::schedule::Schedule::default();
@@ -170,6 +232,7 @@ mod tests {
         assert_eq!(snapshot.version, 2);
         assert_eq!(snapshot.entities.len(), 1);
         assert!(matches!(snapshot.entities[0].kind, EntityKind::Player));
+        assert_eq!(snapshot.entities[0].observation, EntityVisibility::Visible);
     }
 
     #[test]
@@ -179,6 +242,7 @@ mod tests {
             PlayerCharacter,
             TilePosition::new(16, 16, 0),
             Facing(FacingDirection::North),
+            KnowledgeGraph::new(),
         ));
         // NPC directly north of player (in forward cone)
         world.spawn((crate::npc::Npc, TilePosition::new(16, 14, 0)));
@@ -196,6 +260,7 @@ mod tests {
             .find(|e| matches!(e.kind, EntityKind::Npc))
             .expect("NPC should be visible");
         assert_eq!(npc.visibility, VisibilitySector::Forward);
+        assert_eq!(npc.observation, EntityVisibility::Visible);
     }
 
     #[test]
@@ -205,6 +270,7 @@ mod tests {
             PlayerCharacter,
             TilePosition::new(16, 16, 0),
             Facing(FacingDirection::North),
+            KnowledgeGraph::new(),
         ));
         // Wall between player and NPC
         let mut walkability = world.resource_mut::<WalkabilityMap>();
@@ -234,6 +300,7 @@ mod tests {
             PlayerCharacter,
             TilePosition::new(16, 16, 0),
             Facing(FacingDirection::North),
+            KnowledgeGraph::new(),
         ));
         // NPC far behind player (south, in blind spot)
         world.spawn((crate::npc::Npc, TilePosition::new(16, 26, 0)));
@@ -259,6 +326,7 @@ mod tests {
             PlayerCharacter,
             TilePosition::new(16, 16, 0),
             Facing::default(),
+            KnowledgeGraph::new(),
         ));
         // NPC on different z-level
         world.spawn((crate::npc::Npc, TilePosition::new(16, 14, 1)));
@@ -288,6 +356,7 @@ mod tests {
             PlayerCharacter,
             TilePosition::new(16, 16, 0),
             Facing::default(),
+            KnowledgeGraph::new(),
         ));
 
         let mut schedule = bevy_ecs::schedule::Schedule::default();
@@ -311,6 +380,7 @@ mod tests {
             PlayerCharacter,
             TilePosition::new(16, 16, 0),
             Facing::default(),
+            KnowledgeGraph::new(),
         ));
 
         let mut schedule = bevy_ecs::schedule::Schedule::default();
@@ -330,4 +400,153 @@ mod tests {
             .any(|t| t.x == 16 && t.y == 16 && t.z == 0);
         assert!(has_observer_tile, "observer tile should be visible");
     }
+
+    #[test]
+    fn visible_npc_has_relationship_from_knowledge() {
+        let mut world = setup_world(32, 32);
+        let mut registry = EntityRegistry::new(0);
+
+        let npc = world
+            .spawn((crate::npc::Npc, TilePosition::new(16, 14, 0)))
+            .id();
+        let npc_sid = registry.register(npc);
+
+        // Player knows NPC is hostile
+        let mut kg = KnowledgeGraph::new();
+        kg.observe_entity(npc_sid, TilePosition::new(16, 14, 0), 50);
+        kg.set_relationship(&npc_sid, RelationshipState::Hostile);
+
+        world.spawn((
+            PlayerCharacter,
+            TilePosition::new(16, 16, 0),
+            Facing(FacingDirection::North),
+            kg,
+        ));
+
+        world.insert_resource(registry);
+
+        let mut schedule = bevy_ecs::schedule::Schedule::default();
+        schedule.add_systems(compute_observer_snapshot);
+        schedule.run(&mut world);
+
+        let buffer = world.resource::<SnapshotBuffer>();
+        let snapshot = buffer.snapshot.as_ref().unwrap();
+        let npc_entity = snapshot
+            .entities
+            .iter()
+            .find(|e| matches!(e.kind, EntityKind::Npc))
+            .expect("NPC should be visible");
+        assert_eq!(npc_entity.relationship, RelationshipState::Hostile);
+        assert_eq!(npc_entity.observation, EntityVisibility::Visible);
+    }
+
+    #[test]
+    fn remembered_entity_appears_as_ghost() {
+        let mut world = setup_world(32, 32);
+        let mut registry = EntityRegistry::new(0);
+
+        // NPC exists but is behind a wall (not visible)
+        let npc = world
+            .spawn((crate::npc::Npc, TilePosition::new(16, 10, 0)))
+            .id();
+        let npc_sid = registry.register(npc);
+
+        // Player previously saw NPC, now it left LOS (KnowsDetails)
+        let mut kg = KnowledgeGraph::new();
+        kg.observe_entity(npc_sid, TilePosition::new(16, 14, 0), 50);
+        kg.observe_entity_leaving_los(&npc_sid, 60);
+        kg.set_relationship(&npc_sid, RelationshipState::PersonOfInterest);
+
+        let player = world
+            .spawn((
+                PlayerCharacter,
+                TilePosition::new(16, 16, 0),
+                Facing(FacingDirection::North),
+                kg,
+            ))
+            .id();
+        registry.register(player);
+
+        // Wall blocks LOS to NPC's actual position
+        let mut walkability = world.resource_mut::<WalkabilityMap>();
+        walkability.set_walkable(&TilePosition::new(16, 12, 0), false);
+
+        world.insert_resource(registry);
+        world.insert_resource(SimulationTime { tick: 100, paused: false });
+
+        let mut schedule = bevy_ecs::schedule::Schedule::default();
+        schedule.add_systems(compute_observer_snapshot);
+        schedule.run(&mut world);
+
+        let buffer = world.resource::<SnapshotBuffer>();
+        let snapshot = buffer.snapshot.as_ref().unwrap();
+
+        // Should have player (visible) + NPC (remembered)
+        let remembered: Vec<_> = snapshot
+            .entities
+            .iter()
+            .filter(|e| matches!(e.observation, EntityVisibility::Remembered { .. }))
+            .collect();
+        assert_eq!(remembered.len(), 1, "should have one remembered entity");
+        assert_eq!(remembered[0].relationship, RelationshipState::PersonOfInterest);
+
+        // Remembered entity should be at last_known_position (16, 14) not actual (16, 10)
+        assert_eq!(remembered[0].x, 16.5);
+        assert_eq!(remembered[0].y, 14.5);
+
+        if let EntityVisibility::Remembered { confidence, age_ticks } = &remembered[0].observation {
+            assert_eq!(*confidence, KnowledgeConfidence::KnowsDetails);
+            assert_eq!(*age_ticks, 50); // tick 100 - last_observed 50
+        }
+    }
+
+    #[test]
+    fn direct_confidence_not_shown_as_remembered() {
+        let mut world = setup_world(32, 32);
+        let mut registry = EntityRegistry::new(0);
+
+        // NPC exists but not in LOS
+        let npc = world
+            .spawn((crate::npc::Npc, TilePosition::new(16, 10, 0)))
+            .id();
+        let npc_sid = registry.register(npc);
+
+        // Knowledge still shows Direct (transient inconsistency)
+        let mut kg = KnowledgeGraph::new();
+        kg.observe_entity(npc_sid, TilePosition::new(16, 14, 0), 50);
+        // Still Direct — don't show as ghost
+
+        let player = world
+            .spawn((
+                PlayerCharacter,
+                TilePosition::new(16, 16, 0),
+                Facing(FacingDirection::North),
+                kg,
+            ))
+            .id();
+        registry.register(player);
+
+        // Wall blocks actual NPC position
+        let mut walkability = world.resource_mut::<WalkabilityMap>();
+        walkability.set_walkable(&TilePosition::new(16, 12, 0), false);
+
+        world.insert_resource(registry);
+
+        let mut schedule = bevy_ecs::schedule::Schedule::default();
+        schedule.add_systems(compute_observer_snapshot);
+        schedule.run(&mut world);
+
+        let buffer = world.resource::<SnapshotBuffer>();
+        let snapshot = buffer.snapshot.as_ref().unwrap();
+
+        let remembered: Vec<_> = snapshot
+            .entities
+            .iter()
+            .filter(|e| matches!(e.observation, EntityVisibility::Remembered { .. }))
+            .collect();
+        assert!(
+            remembered.is_empty(),
+            "Direct-confidence entities should not appear as remembered ghosts"
+        );
+    }
 }

server/tests/bridge_ipc.rs

@@ -49,6 +49,8 @@ fn snapshot_roundtrip_over_unix_socket() {
                 z: 0,
                 kind: EntityKind::Npc,
                 visibility: VisibilitySector::Forward,
+                relationship: RelationshipState::Unknown,
+                observation: EntityVisibility::Visible,
             }],
             visible_tiles: vec![],
         };

server/tests/bridge_tcp.rs

@@ -35,6 +35,8 @@ fn snapshot_roundtrip_over_tcp() {
                 z: 0,
                 kind: EntityKind::Npc,
                 visibility: VisibilitySector::Forward,
+                relationship: RelationshipState::Unknown,
+                observation: EntityVisibility::Visible,
             }],
             visible_tiles: vec![],
         };

server/tests/gen_fixtures.rs

@@ -45,6 +45,8 @@ fn generate_msgpack_fixtures() {
             z: 0,
             kind: EntityKind::Npc,
             visibility: VisibilitySector::Forward,
+            relationship: RelationshipState::Unknown,
+            observation: EntityVisibility::Visible,
         }],
     );
     write_fixture(
@@ -86,6 +88,8 @@ fn generate_msgpack_fixtures() {
             z: 0,
             kind: EntityKind::Player,
             visibility: VisibilitySector::Forward,
+            relationship: RelationshipState::Unknown,
+            observation: EntityVisibility::Visible,
         }],
     );
     write_fixture(
@@ -104,6 +108,8 @@ fn generate_msgpack_fixtures() {
                 z: 0,
                 kind: EntityKind::Player,
                 visibility: VisibilitySector::Forward,
+                relationship: RelationshipState::Known,
+                observation: EntityVisibility::Visible,
             },
             VisibleEntity {
                 entity_id: 2,
@@ -112,6 +118,8 @@ fn generate_msgpack_fixtures() {
                 z: 0,
                 kind: EntityKind::Npc,
                 visibility: VisibilitySector::Peripheral,
+                relationship: RelationshipState::Unknown,
+                observation: EntityVisibility::Visible,
             },
             VisibleEntity {
                 entity_id: 3,
@@ -120,6 +128,8 @@ fn generate_msgpack_fixtures() {
                 z: 1,
                 kind: EntityKind::Object,
                 visibility: VisibilitySector::Forward,
+                relationship: RelationshipState::Unknown,
+                observation: EntityVisibility::Visible,
             },
             VisibleEntity {
                 entity_id: 4,
@@ -128,6 +138,8 @@ fn generate_msgpack_fixtures() {
                 z: -1,
                 kind: EntityKind::Terrain,
                 visibility: VisibilitySector::Forward,
+                relationship: RelationshipState::Unknown,
+                observation: EntityVisibility::Visible,
             },
         ],
     );
@@ -154,6 +166,8 @@ fn generate_msgpack_fixtures() {
             z: 0,
             kind: EntityKind::Player,
             visibility: VisibilitySector::Forward,
+            relationship: RelationshipState::Unknown,
+            observation: EntityVisibility::Visible,
         }],
         visible_tiles: vec![
             VisibleTile {

server/tests/serialization.rs

@@ -32,6 +32,8 @@ fn observer_snapshot_roundtrip() {
             z: 0,
             kind: EntityKind::Npc,
             visibility: VisibilitySector::Forward,
+            relationship: RelationshipState::Unknown,
+            observation: EntityVisibility::Visible,
         }],
     );
 
@@ -158,6 +160,8 @@ fn all_entity_kind_variants_roundtrip() {
             z: 0,
             kind,
             visibility: VisibilitySector::Forward,
+            relationship: RelationshipState::Unknown,
+            observation: EntityVisibility::Visible,
         };
         let snapshot = test_snapshot(0, vec![entity]);
         let bytes = rmp_serde::to_vec_named(&snapshot).expect("serialize");
@@ -190,6 +194,8 @@ fn snapshot_v2_fields_roundtrip() {
             z: 0,
             kind: EntityKind::Player,
             visibility: VisibilitySector::Forward,
+            relationship: RelationshipState::Unknown,
+            observation: EntityVisibility::Visible,
         }],
         visible_tiles: vec![
             VisibleTile {