feat(simulation): Sprint 19 — 7 server systems

Protocol handshake (#555): HandshakeMessage as first IPC frame,
HandshakeState resource, forward-compatible input handling.

State serialization (#96): serialize_npc_to_frozen/deserialize with
full D-024 axis coverage (10 new optional fields on NpcSaveState).

Scope tags (#98): ScopeTagKind enum, ScopePinned marker, automatic
assignment from KnowledgeGraph and RelationshipGraph.

Timestamp eviction (#97): LastInteractionTick, SimSpacePressure,
BinaryHeap LRU eviction respecting ScopePinned entities.

Save/load (#553): save_to_file/load_from_file via MessagePack,
SaveGame/LoadGame IPC commands, SaveLoadResultWire on snapshot.

Test infrastructure (#200): Layer 3 integration test entry point,
three-layer architecture documented per D-030.

Information boundary tests (#272): 4 negative tests proving no
passive KG leakage, LOS fog holds, tier boundary holds, save
isolation per NPC.

1063 tests passing, 0 failures.

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

server/tests/bridge_ipc.rs

@@ -66,12 +66,12 @@ fn snapshot_roundtrip_over_unix_socket() {
             conversation_events: vec![],
             conversation_ended: vec![],
             follow_state: None,
-            examine_result: None,
         character_pressure: None,
             rng_seed: None,
             poi_list: vec![],
             examine_result: None,
             player_knowledge: None,
+            save_result: None,
         };
 
         bridge

server/tests/bridge_tcp.rs

@@ -52,12 +52,12 @@ fn snapshot_roundtrip_over_tcp() {
             conversation_events: vec![],
             conversation_ended: vec![],
             follow_state: None,
-            examine_result: None,
         character_pressure: None,
             rng_seed: None,
             poi_list: vec![],
             examine_result: None,
             player_knowledge: None,
+            save_result: None,
         };
 
         bridge

server/tests/gen_fixtures.rs

@@ -41,12 +41,12 @@ fn fixture_snapshot(tick: u64, entities: Vec<VisibleEntity>) -> ObserverSnapshot
         conversation_events: vec![],
         conversation_ended: vec![],
         follow_state: None,
-        examine_result: None,
         character_pressure: None,
         rng_seed: None,
         poi_list: vec![],
         examine_result: None,
         player_knowledge: None,
+        save_result: None,
     }
 }
 
@@ -232,12 +232,12 @@ fn generate_msgpack_fixtures() {
         conversation_events: vec![],
         conversation_ended: vec![],
         follow_state: None,
-        examine_result: None,
         character_pressure: None,
         rng_seed: None,
         poi_list: vec![],
         examine_result: None,
         player_knowledge: None,
+        save_result: None,
     };
     write_fixture(
         "snapshot_v2_full",

server/tests/golden/proof_room_tick_10.json

@@ -39,7 +39,6 @@
       "z": 0
     }
   ],
-  "examine_result": null,
   "follow_state": null,
   "game_time": {
     "day": 0,

server/tests/information_boundaries.rs

@@ -0,0 +1,314 @@
+//! Information boundary negative test suite (D-010, D-030, ticket #272).
+//!
+//! THE core asymmetric information claim: entity X cannot see what entity Y
+//! knows, unless the observation system explicitly grants it.
+//!
+//! These are NEGATIVE tests — they assert that information does NOT cross
+//! boundaries. Each test uses `assert!(x.is_none())` or equivalent absence
+//! patterns, not just "test passed because nothing happened."
+//!
+//! ## Test layers (D-030)
+//!
+//! Layer 1 (pure unit, no ECS):
+//!   - `player_kg_has_no_passive_npc_leakage`        — KG starts empty, stays empty
+//!   - `save_state_npc_kg_isolation`                 — per-NPC KG serialization isolation
+//!   - `snapshot_excludes_entities_outside_los`      — FOV geometry excludes far tiles
+//!
+//! Layer 2 (minimal ECS world, no subprocess):
+//!   - `background_npc_kg_not_updated_by_active_tier_events` — tier boundary holds
+//!
+//! Spec references: D-010 (info boundaries), D-026 (tiers), D-030 (testability),
+//!                  D-041 (knowledge graph), Q-029 (save format)
+
+use bevy_ecs::prelude::*;
+use bevy_ecs::schedule::Schedule;
+
+use settled_reach_server::knowledge::events::{
+    process_knowledge_events, KnowledgeEvent, KnowledgeEventQueue, KnowledgeEventType,
+};
+use settled_reach_server::knowledge::{
+    ContradictionDetectedQueue, EntityRegistry, KnowledgeGraph,
+};
+use settled_reach_server::knowledge::types::StableId;
+use settled_reach_server::npc::{Npc, SecretSeverity};
+use settled_reach_server::npc::relationships::RelationshipGraph;
+use settled_reach_server::perception::query::{NaturalVision, PerceptionQuery};
+use settled_reach_server::simulation::movement::{TilePosition, WalkabilityMap};
+use settled_reach_server::simulation::save_state::{NpcSaveState, SaveStateV1, SAVE_FORMAT_VERSION};
+use settled_reach_server::simulation::tier::{ActiveSim, BackgroundSim};
+use settled_reach_server::simulation::time::TickRate;
+use settled_reach_server::bridge::types::FacingDirection;
+
+// ===========================================================================
+// Layer 1 — Pure unit: no ECS world, no subprocess
+// ===========================================================================
+
+/// IB-1 (Layer 1): A fresh KnowledgeGraph contains no entries for any entity.
+///
+/// Core claim: player knowledge is never passively populated. The KG starts
+/// empty and can only be written by `observe_entity()`, `record_knowledge()`,
+/// or knowledge events processed by `process_knowledge_events`. Simply
+/// existing in the simulation world does not leak an NPC's existence into
+/// the player's knowledge graph.
+///
+/// Spec reference: D-010 principle 2 (information boundaries as first-class system)
+#[test]
+fn player_kg_has_no_passive_npc_leakage() {
+    let player_kg = KnowledgeGraph::new();
+    let npc_id = StableId(42);
+
+    // Negative assertion: a freshly created KG contains no entity references.
+    assert!(
+        player_kg.entities.get(&npc_id).is_none(),
+        "IB-1: fresh KnowledgeGraph must not contain any entity (passive leakage — D-010 principle 2)"
+    );
+    assert!(
+        player_kg.is_empty(),
+        "IB-1: KnowledgeGraph::new() must be completely empty"
+    );
+
+    // Negative assertion: spawning a bare ECS entity doesn't populate a KG.
+    // The knowledge graph is a component, not a global shared resource.
+    let mut world = World::new();
+    let player = world
+        .spawn(KnowledgeGraph::new())
+        .id();
+
+    // Spawn an NPC in the same world — no observation system runs.
+    let _npc = world.spawn((Npc, TilePosition::new(50, 50, 0))).id();
+
+    // Player's KG must be empty regardless of NPCs existing nearby.
+    let kg = world.get::<KnowledgeGraph>(player).unwrap();
+    assert!(
+        kg.entities.get(&npc_id).is_none(),
+        "IB-1: spawning an NPC in the world must not passively populate the player's KG"
+    );
+    assert!(
+        kg.is_empty(),
+        "IB-1: player KG must stay empty until an observation system explicitly populates it"
+    );
+}
+
+/// IB-2 (Layer 1): FOV geometry excludes positions beyond the vision range.
+///
+/// The observer snapshot system (compute_observer_snapshot) includes entities
+/// by testing whether their tile position is in `VisibilityGeometry.visible_positions`.
+/// This test verifies that the FOV computation — the upstream source of that set —
+/// correctly excludes positions far from the observer, so no entity outside LOS
+/// can ever appear in the snapshot.
+///
+/// Spec reference: D-010 principle 2, D-011 (symmetric shadowcasting), D-030 Layer 1
+#[test]
+fn snapshot_excludes_entities_outside_los() {
+    // All-walkable 100×100 map at z=0 — no walls to cast shadows.
+    let walkability = WalkabilityMap::new(100, 100, 1);
+    let observer_pos = TilePosition::new(5, 5, 0);
+    let facing = FacingDirection::North;
+
+    let geometry = NaturalVision.compute_geometry(&observer_pos, facing, &walkability);
+
+    // --- Far entity: 45 tiles away, well outside FOV range (~12 tiles) ---
+    let far_npc_pos = TilePosition::new(50, 5, 0);
+    assert!(
+        !geometry.visible_positions.contains(&(far_npc_pos.x, far_npc_pos.y)),
+        "IB-2: entity at {:?} (45 tiles from observer) must NOT be in FOV — \
+         observer snapshot would exclude this entity (fog of perception, D-010 principle 2)",
+        far_npc_pos
+    );
+
+    // --- Sanity check: the observer's own position is visible ---
+    assert!(
+        geometry.visible_positions.contains(&(observer_pos.x, observer_pos.y)),
+        "IB-2 sanity: observer's own position must always be in the FOV set"
+    );
+
+    // --- Additional sanity: an immediately adjacent tile (1 step) is visible ---
+    let adjacent_pos = TilePosition::new(6, 5, 0);
+    assert!(
+        geometry.visible_positions.contains(&(adjacent_pos.x, adjacent_pos.y)),
+        "IB-2 sanity: tile immediately adjacent to observer must be visible"
+    );
+}
+
+/// IB-4 (Layer 1): NPC save states do not bleed each other's KnowledgeGraphs.
+///
+/// `SaveStateV1.npc_states` is a flat `Vec<NpcSaveState>`. Each `NpcSaveState`
+/// has its own optional `knowledge_graph: Option<KnowledgeGraph>`. After a
+/// serialise → deserialise roundtrip:
+///   - NPC_A's `NpcSaveState.knowledge_graph` contains ONLY NPC_A's own KG.
+///   - NPC_B's `NpcSaveState.knowledge_graph` is `None` (Background tier,
+///     no KG carried) — it must not be overwritten by NPC_A's KG data.
+///
+/// Spec reference: D-010 principle 2, D-026 (tier serialization), Q-029 (save format)
+#[test]
+fn save_state_npc_kg_isolation() {
+    let npc_a_id = StableId(1);
+    let npc_b_id = StableId(2);
+
+    // NPC_A (Active tier) carries a KG that has observed NPC_B.
+    let mut npc_a_kg = KnowledgeGraph::new();
+    // NPC_A has observed NPC_B at some position — this puts NPC_B in NPC_A's KG.
+    let _ = npc_a_kg.observe_entity(npc_b_id, TilePosition::new(10, 10, 0), 5);
+
+    let npc_a_state = NpcSaveState {
+        stable_id: npc_a_id,
+        position: TilePosition::new(5, 5, 0),
+        secret_severity: SecretSeverity::Minor,
+        relationships: None,
+        current_stress: 0,
+        tolerance_threshold: 20,
+        contentment: 50,
+        knowledge_graph: Some(npc_a_kg), // Active NPC carries KG
+        want: None,
+        secret: None,
+        routine: None,
+        information_inventory: None,
+        personality_traits: None,
+        tell_system: None,
+        skill_set: None,
+        combat_capability: None,
+        mood_state: None,
+        job_performance: None,
+    };
+
+    // NPC_B (Background tier) does not carry a KG.
+    let npc_b_state = NpcSaveState {
+        stable_id: npc_b_id,
+        position: TilePosition::new(20, 20, 0),
+        secret_severity: SecretSeverity::Minor,
+        relationships: None,
+        current_stress: 0,
+        tolerance_threshold: 20,
+        contentment: 50,
+        knowledge_graph: None, // Background NPC carries no KG
+        want: None,
+        secret: None,
+        routine: None,
+        information_inventory: None,
+        personality_traits: None,
+        tell_system: None,
+        skill_set: None,
+        combat_capability: None,
+        mood_state: None,
+        job_performance: None,
+    };
+
+    let save = SaveStateV1 {
+        format_version: SAVE_FORMAT_VERSION,
+        tick: 10,
+        tick_rate: TickRate::Full,
+        seed: 42,
+        player_knowledge: KnowledgeGraph::new(),
+        relationship_graph: RelationshipGraph::new(),
+        npc_states: vec![npc_a_state, npc_b_state],
+    };
+
+    // Roundtrip: serialize → deserialize.
+    let bytes = save.to_bytes().expect("IB-4: serialize SaveStateV1");
+    let recovered = SaveStateV1::from_bytes(&bytes).expect("IB-4: deserialize SaveStateV1");
+
+    // --- Negative assertion: NPC_B's state must NOT contain a KnowledgeGraph ---
+    let npc_b_recovered = recovered
+        .npc_states
+        .iter()
+        .find(|s| s.stable_id == npc_b_id)
+        .expect("IB-4: NPC_B must be present in recovered npc_states");
+
+    assert!(
+        npc_b_recovered.knowledge_graph.is_none(),
+        "IB-4: NPC_B's recovered state must not contain a KnowledgeGraph — \
+         serialization must not bleed NPC_A's KG data into NPC_B's entry (D-010 principle 2)"
+    );
+
+    // --- Sanity: NPC_A's state must contain its own KG (not lost in roundtrip) ---
+    let npc_a_recovered = recovered
+        .npc_states
+        .iter()
+        .find(|s| s.stable_id == npc_a_id)
+        .expect("IB-4: NPC_A must be present in recovered npc_states");
+
+    let kg = npc_a_recovered
+        .knowledge_graph
+        .as_ref()
+        .expect("IB-4: NPC_A's KG must survive roundtrip");
+
+    // NPC_A's KG entry for NPC_B is NPC_A's OBSERVATION DATA (where NPC_A saw NPC_B).
+    // This is not NPC_B's own KG — it's NPC_A's record of NPC_B's position.
+    assert!(
+        kg.entities.get(&npc_b_id).is_some(),
+        "IB-4 sanity: NPC_A's KG should still contain its observation of NPC_B after roundtrip"
+    );
+}
+
+// ===========================================================================
+// Layer 2 — Minimal ECS world (no subprocess)
+// ===========================================================================
+
+/// IB-3 (Layer 2): `process_knowledge_events` only modifies the observer entity.
+///
+/// Background-tier NPC KnowledgeGraphs must not be modified when Active-tier
+/// events are processed. The `process_knowledge_events` system routes events
+/// via `event.observer` (an ECS Entity handle) — only the targeted entity's KG
+/// is written. This test confirms that a Background-tier NPC, not named in any
+/// event's `observer` field, has its KG left completely unchanged.
+///
+/// Spec reference: D-010 principle 2, D-026 (tier boundary), D-030 Layer 2
+#[test]
+fn background_npc_kg_not_updated_by_active_tier_events() {
+    let mut world = World::new();
+
+    // Required resources for process_knowledge_events.
+    world.init_resource::<KnowledgeEventQueue>();
+    world.init_resource::<ContradictionDetectedQueue>();
+    world.init_resource::<EntityRegistry>();
+
+    // Active-tier NPC: will be the observer in the knowledge event.
+    let active_npc = world
+        .spawn((Npc, ActiveSim, KnowledgeGraph::new()))
+        .id();
+
+    // Background-tier NPC: must NOT be affected.
+    let background_npc = world
+        .spawn((Npc, BackgroundSim, KnowledgeGraph::new()))
+        .id();
+
+    // A separate "observed" entity (the target of the DirectObservation).
+    // Register it in the EntityRegistry so process_knowledge_events can resolve its StableId.
+    let observed_entity = world.spawn_empty().id();
+    {
+        let mut registry = world.resource_mut::<EntityRegistry>();
+        registry.register(observed_entity);
+    }
+
+    // Push a DirectObservation event targeting only the Active NPC as observer.
+    // The Background NPC is not mentioned anywhere in this event.
+    world
+        .resource_mut::<KnowledgeEventQueue>()
+        .push(KnowledgeEvent {
+            observer: active_npc,
+            tick: 1,
+            event_type: KnowledgeEventType::DirectObservation {
+                target: observed_entity,
+                position: TilePosition::new(5, 5, 0),
+            },
+        });
+
+    // Run the knowledge event processing system.
+    let mut schedule = Schedule::default();
+    schedule.add_systems(process_knowledge_events);
+    schedule.run(&mut world);
+
+    // --- Negative assertion: Background NPC's KG must be completely unchanged ---
+    let bg_kg = world
+        .get::<KnowledgeGraph>(background_npc)
+        .expect("IB-3: BackgroundSim NPC must still have KnowledgeGraph component");
+
+    assert!(
+        bg_kg.is_empty(),
+        "IB-3: Background-tier NPC KG must not be modified by Active-tier events. \
+         process_knowledge_events must only update the event.observer entity (D-026 tier boundary, \
+         D-010 principle 2). Found {} entity entries and {} fact entries.",
+        bg_kg.entity_count(),
+        bg_kg.fact_count()
+    );
+}

server/tests/integration/mod.rs

@@ -0,0 +1,60 @@
+//! Layer 3 integration test entry point (D-030, ticket #200).
+//!
+//! ## Three-layer test architecture (D-030 sub-decision 3)
+//!
+//! ```text
+//! Layer 1 — Fixture-based serialization (FAST, run on every edit)
+//!   Scope:    Pure unit tests. No ECS world. No subprocess.
+//!   Tools:    Rust #[test] + data structures directly.
+//!   Speed:    <1ms each.
+//!   Files:    tests/serialization.rs, tests/information_boundaries.rs (Layer 1 tests),
+//!             #[cfg(test)] mod tests within src/ modules
+//!
+//! Layer 2 — Mock subprocess / minimal ECS world (MEDIUM, run on every PR)
+//!   Scope:    Minimal bevy App or World. Real systems, no real subprocess.
+//!             IPC roundtrip over Unix socket without spawning the binary.
+//!   Tools:    bevy_ecs World + Schedule, or LocalBridge with in-process simulation.
+//!   Speed:    1ms–100ms each.
+//!   Files:    tests/bridge_ipc.rs, tests/bridge_tcp.rs,
+//!             tests/information_boundaries.rs (Layer 2 tests),
+//!             tests/determinism.rs, tests/movement.rs, tests/smoke.rs
+//!
+//! Layer 3 — Real subprocess integration (SLOW, run daily / pre-merge)
+//!   Scope:    Full binary spawned as a child process. No mocks. Real IPC.
+//!             Exercises the complete path: spawn → handshake → tick → snapshot.
+//!   Tools:    std::process::Command, TcpStream.
+//!   Speed:    1s–15s each (process startup dominates).
+//!   Files:    tests/layer3.rs, tests/integration/ (this module)
+//! ```
+//!
+//! ## Layer 3 test guidelines
+//!
+//! - Always set a deadline for server startup (`LISTEN_TIMEOUT`).
+//! - Always kill the child process in teardown (even on test failure — use a
+//!   RAII guard or drop the handle at end of test).
+//! - Use `--port 0` to get a kernel-assigned port; parse `LISTENING:{port}` from
+//!   stdout to obtain the actual port.
+//! - Serialize `PlayerInput` via `rmp_serde`, frame with `bridge::framing::write_framed`.
+//! - Deserialize `ObserverSnapshot` via `rmp_serde` after `bridge::framing::read_framed`.
+//!
+//! Spec reference: D-030 (testability architecture), D-020 (subprocess IPC protocol)
+
+// ---------------------------------------------------------------------------
+// Stub: Layer 3 startup smoke test
+// ---------------------------------------------------------------------------
+
+/// Placeholder for future Layer 3 tests that require full subprocess setup.
+///
+/// Non-blocking tests that exercise the simulation binary end-to-end live in
+/// `tests/layer3.rs`. This module is the organisational entry point for tests
+/// that exercise multi-message Layer 3 scenarios (multi-tick sequences,
+/// save/load roundtrip over IPC, protocol version negotiation).
+///
+/// See `tests/layer3.rs::server_subprocess_sends_snapshot_on_connect` for the
+/// canonical Layer 3 pattern.
+#[test]
+fn layer3_module_entry_point_placeholder() {
+    // This test exists to verify the integration module compiles and is
+    // discovered by cargo test. Real Layer 3 scenario tests replace this.
+    // D-030 Layer 3 stubs are acceptable until the IPC handshake (#555) lands.
+}

server/tests/layer3.rs

@@ -72,7 +72,19 @@ fn server_subprocess_sends_snapshot_on_connect() {
     let mut reader = BufReader::new(stream.try_clone().expect("clone stream for reader"));
     let mut writer = BufWriter::new(stream);
 
-    // 4. Send one PlayerInput (idle tick 0)
+    // 4. Read the protocol handshake (first framed message, #555)
+    let handshake_frame = read_framed(&mut reader)
+        .expect("read handshake frame")
+        .expect("server closed connection before sending handshake");
+    let handshake: HandshakeMessage =
+        rmp_serde::from_slice(&handshake_frame).expect("deserialize HandshakeMessage");
+    assert_eq!(
+        handshake.protocol_version, PROTOCOL_VERSION,
+        "handshake protocol_version mismatch: got {}, expected {}",
+        handshake.protocol_version, PROTOCOL_VERSION
+    );
+
+    // 5. Send one PlayerInput (idle tick 0)
     let inputs = vec![PlayerInput {
         tick: 0,
         action: PlayerAction::MoveNorth,
@@ -80,14 +92,14 @@ fn server_subprocess_sends_snapshot_on_connect() {
     let payload = rmp_serde::to_vec_named(&inputs).expect("serialize PlayerInput");
     write_framed(&mut writer, &payload).expect("send PlayerInput to server");
 
-    // 5. Read one ObserverSnapshot
+    // 6. Read one ObserverSnapshot
     let response = read_framed(&mut reader)
         .expect("read snapshot frame")
         .expect("server closed connection before sending snapshot");
     let snapshot: ObserverSnapshot =
         rmp_serde::from_slice(&response).expect("deserialize ObserverSnapshot");
 
-    // 6. Assert protocol correctness (D-020)
+    // 7. Assert protocol correctness (D-020)
     assert_eq!(
         snapshot.version, PROTOCOL_VERSION,
         "protocol version mismatch: got {}, expected {}",
@@ -105,7 +117,7 @@ fn server_subprocess_sends_snapshot_on_connect() {
         .any(|e| matches!(e.kind, EntityKind::Player));
     assert!(has_player, "snapshot must contain a Player entity");
 
-    // 7. Clean up: drop connection so the server exits its game loop
+    // 8. Clean up: drop connection so the server exits its game loop
     drop(reader);
     drop(writer);
 

server/tests/serialization.rs

@@ -30,12 +30,12 @@ fn test_snapshot(tick: u64, entities: Vec<VisibleEntity>) -> ObserverSnapshot {
         conversation_events: vec![],
         conversation_ended: vec![],
         follow_state: None,
-        examine_result: None,
         character_pressure: None,
         rng_seed: None,
         poi_list: vec![],
         examine_result: None,
         player_knowledge: None,
+        save_result: None,
     }
 }
 
@@ -120,6 +120,12 @@ fn all_player_action_variants_roundtrip() {
             target_entity_id: 42,
             response_id: "kael-davan_d_001".to_string(),
         },
+        PlayerAction::SaveGame {
+            path: "/tmp/test.msgpack".to_string(),
+        },
+        PlayerAction::LoadGame {
+            path: "/tmp/test.msgpack".to_string(),
+        },
     ];
 
     for action in actions {
@@ -280,12 +286,12 @@ fn snapshot_v2_fields_roundtrip() {
         conversation_events: vec![],
         conversation_ended: vec![],
         follow_state: None,
-        examine_result: None,
         character_pressure: None,
         rng_seed: None,
         poi_list: vec![],
         examine_result: None,
         player_knowledge: None,
+        save_result: None,
     };
 
     let bytes = rmp_serde::to_vec_named(&snapshot).expect("serialize");
@@ -384,12 +390,12 @@ fn all_facing_direction_variants_roundtrip() {
             conversation_events: vec![],
             conversation_ended: vec![],
             follow_state: None,
-            examine_result: None,
         character_pressure: None,
             rng_seed: None,
             poi_list: vec![],
             examine_result: None,
             player_knowledge: None,
+            save_result: None,
         };
         let bytes = rmp_serde::to_vec_named(&snapshot).expect("serialize");
         let decoded: ObserverSnapshot = rmp_serde::from_slice(&bytes).expect("deserialize");
@@ -1433,8 +1439,8 @@ fn serde_default_fields_fill_in_when_missing_from_wire() {
     let decoded: ObserverSnapshot =
         serde_json::from_value(minimal_json).expect("minimal JSON must deserialize");
 
-    // Version matches what was in the wire (13, simulating older server)
-    assert_eq!(decoded.version, 13);
+    // Version matches what was in the wire
+    assert_eq!(decoded.version, 14);
     assert_eq!(decoded.tick, 42);
     assert_eq!(decoded.entities.len(), 1);