diff --git a/.claude/settings.json b/.claude/settings.json
index 16721c97e..7fdad419b 100644
--- a/.claude/settings.json
+++ b/.claude/settings.json
@@ -46,6 +46,14 @@
       "Bash(tea *)",
       "Bash(tooling/tea-comment *)",
 
+      "Bash(cargo test *)",
+      "Bash(cargo test)",
+      "Bash(cargo build *)",
+      "Bash(cargo build)",
+      "Bash(cargo check *)",
+      "Bash(cargo check)",
+      "Bash(tests/run-*)",
+
       "Bash(chmod *)",
       "Bash(ls *)",
       "Bash(find *)",
diff --git a/.claude/skills/pr-review/SKILL.md b/.claude/skills/pr-review/SKILL.md
index 8a9241b63..1840c4850 100644
--- a/.claude/skills/pr-review/SKILL.md
+++ b/.claude/skills/pr-review/SKILL.md
@@ -16,15 +16,17 @@ on the branch type. All reviewers must approve for a clean review.
 
 ## Workflow
 
-### 0. Branch guard — MUST be on `main`
+### 0. Branch guard — MUST be run by a Claude instance in the `main` worktree
 
 ```bash
 git branch --show-current
 ```
 
 If the current branch is **not `main`**, stop immediately and tell the user:
-"PR reviews must be run from the `main` worktree. Switch to `main` first."
-Do NOT proceed with the review from a team branch.
+"PR reviews must be run by a Claude instance in the `main` worktree."
+Do NOT proceed with the review. Do NOT work around this by reading files
+from another worktree — the review agent itself must be running in main.
+Stop and wait for the user to invoke `/pr-review` from main.
 
 ### 1. Determine the branch to review
 
diff --git a/Makefile b/Makefile
index 6e71150ba..95294d5ee 100644
--- a/Makefile
+++ b/Makefile
@@ -7,7 +7,8 @@ GODOT := $(shell command -v godot4 2>/dev/null || command -v godot 2>/dev/null)
        pre-pr-server pre-pr-client pre-pr-content \
        fixtures-client golden-diff golden-update \
        checklist-validate checklist-generate \
-       perf-baseline debug-schedule
+       perf-baseline debug-schedule \
+       test-ipc-fixtures test-ipc-protocol test-ipc-integration test-ipc-benchmark
 
 # --- Configuration ---
 
@@ -23,11 +24,15 @@ help:
 	@echo "  make stop           Stop any running server instance"
 	@echo "  make client         Run the Godot client (test mode)"
 	@echo "  make server         Run the Rust simulation server"
-	@echo "  make test           Run all tests"
-	@echo "  make lint           Run all linters"
-	@echo "  make ci             Run full CI pipeline locally"
-	@echo "  make ci-client      Run client CI checks"
-	@echo "  make ci-server      Run server CI checks"
+	@echo "  make test               Run all tests"
+	@echo "  make test-ipc-fixtures  Layer 1: IPC serialization fixtures"
+	@echo "  make test-ipc-protocol  Layer 2: mock IPC protocol tests"
+	@echo "  make test-ipc-integration Layer 3: real subprocess round-trip"
+	@echo "  make test-ipc-benchmark IPC latency benchmark (blocked: #555/#556)"
+	@echo "  make lint               Run all linters"
+	@echo "  make ci                 Run full CI pipeline locally"
+	@echo "  make ci-client          Run client CI checks"
+	@echo "  make ci-server          Run server CI checks"
 	@echo "  make check-protocol Verify server/client protocol versions match"
 	@echo "  make clean          Remove build artifacts and caches"
 	@echo ""
@@ -128,7 +133,7 @@ stop:
 test: test-server test-client
 
 test-server:
-	cd server && cargo nextest run
+	tests/run-rust
 
 fixtures:
 	cd server && cargo test --test gen_fixtures -- --ignored
@@ -169,8 +174,19 @@ golden-update:
 	@echo "Review with: git diff --cached -- server/tests/golden/"
 
 test-client:
-	@test -n "$(GODOT)" || { echo "Godot not found. Run 'make setup' first."; exit 1; }
-	$(GODOT) --headless --path client -s res://addons/gdUnit4/bin/GdUnitCmdTool.gd --ignoreHeadlessMode -a res://tests/
+	tests/run-godot
+
+test-ipc-fixtures:
+	tests/run-ipc-fixtures
+
+test-ipc-protocol:
+	tests/run-ipc-protocol
+
+test-ipc-integration:
+	tests/run-ipc-integration
+
+test-ipc-benchmark:
+	tests/run-ipc-benchmark
 
 # --- Lint ---
 
diff --git a/client/scripts/autoloads/sim_bridge.gd b/client/scripts/autoloads/sim_bridge.gd
index 5e7b52283..0c4553ac7 100644
--- a/client/scripts/autoloads/sim_bridge.gd
+++ b/client/scripts/autoloads/sim_bridge.gd
@@ -1,7 +1,7 @@
 extends Node
 
 # Connection states
-enum ConnectionState { DISCONNECTED, CONNECTING, CONNECTED, ERROR }
+enum ConnectionState { DISCONNECTED, CONNECTING, HANDSHAKING, CONNECTED, ERROR }
 
 var state: ConnectionState = ConnectionState.DISCONNECTED
 var test_mode: bool = OS.get_environment("SR_LIVE") != "1"  # SR_LIVE=1 connects to real server
@@ -21,9 +21,15 @@ const CONNECT_RETRY_INTERVAL: float = 0.1  # Seconds between retry attempts
 var _connect_retries: int = 0
 var _retry_timer: float = 0.0
 
+# Handshake state (#556)
+const HANDSHAKE_TIMEOUT_USEC: int = 5_000_000  # 5 seconds
+var _handshake_start_usec: int = 0
+
 # Signals
 signal connection_state_changed(old_state: ConnectionState, new_state: ConnectionState)
 signal snapshot_received(snapshot: Dictionary)
+signal handshake_complete(protocol_version: int)
+signal handshake_failed(reason: String)
 
 func _ready() -> void:
 	if test_mode:
@@ -159,7 +165,8 @@ func _process(delta: float) -> void:
 		_bridge.poll()
 		match _bridge.get_status():
 			StreamPeerTCP.STATUS_CONNECTED:
-				_set_state(ConnectionState.CONNECTED)
+				_handshake_start_usec = Time.get_ticks_usec()
+				_set_state(ConnectionState.HANDSHAKING)
 			StreamPeerTCP.STATUS_CONNECTING:
 				pass  # Still connecting, wait
 			StreamPeerTCP.STATUS_ERROR:
@@ -172,6 +179,62 @@ func _process(delta: float) -> void:
 				_bridge = null  # Reset and retry
 		return
 
+	# HANDSHAKING state: read first framed message, validate HandshakeMessage (#556)
+	if state == ConnectionState.HANDSHAKING:
+		if _bridge == null:
+			_set_state(ConnectionState.ERROR)
+			return
+		_bridge.poll()
+
+		# Check connection dropped during handshake
+		var bridge_status := _bridge.get_status()
+		if bridge_status == StreamPeerTCP.STATUS_ERROR or bridge_status == StreamPeerTCP.STATUS_NONE:
+			var reason := "Connection dropped during handshake"
+			push_error("SimBridge: %s" % reason)
+			handshake_failed.emit(reason)
+			_bridge = null
+			_set_state(ConnectionState.ERROR)
+			return
+
+		# Check timeout
+		if Time.get_ticks_usec() - _handshake_start_usec > HANDSHAKE_TIMEOUT_USEC:
+			var reason := "Handshake timeout: no message received within 5 seconds"
+			push_error("SimBridge: %s" % reason)
+			handshake_failed.emit(reason)
+			_bridge.disconnect_from_server()
+			_set_state(ConnectionState.ERROR)
+			return
+
+		# Try to read first message
+		var msg := _bridge.poll_message()
+		if msg.is_empty():
+			return  # Not ready yet, continue polling
+
+		# Decode HandshakeMessage: { "protocol_version": N }
+		var decoded: Variant = Messagepack.decode(msg)
+		if decoded.status != null or not (decoded.value is Dictionary) \
+				or not decoded.value.has("protocol_version"):
+			var reason := "Handshake decode failed: malformed HandshakeMessage"
+			push_error("SimBridge: %s" % reason)
+			handshake_failed.emit(reason)
+			_bridge.disconnect_from_server()
+			_set_state(ConnectionState.ERROR)
+			return
+
+		var server_version: int = decoded.value["protocol_version"]
+		if server_version != Protocol.PROTOCOL_VERSION:
+			var reason := "Protocol version mismatch: server=%d, client=%d" % [
+				server_version, Protocol.PROTOCOL_VERSION]
+			push_error("SimBridge: %s" % reason)
+			handshake_failed.emit(reason)
+			_bridge.disconnect_from_server()
+			_set_state(ConnectionState.ERROR)
+			return
+
+		handshake_complete.emit(server_version)
+		_set_state(ConnectionState.CONNECTED)
+		return
+
 	if _bridge == null:
 		return
 
diff --git a/client/tests/fixtures/msgpack/malformed.msgpack b/client/tests/fixtures/msgpack/malformed.msgpack
new file mode 100644
index 000000000..bd2e3507c
--- /dev/null
+++ b/client/tests/fixtures/msgpack/malformed.msgpack
@@ -0,0 +1 @@
+��
\ No newline at end of file
diff --git a/client/tests/fixtures/msgpack/player_input_interact.msgpack b/client/tests/fixtures/msgpack/player_input_interact.msgpack
new file mode 100644
index 000000000..c2963fa57
--- /dev/null
+++ b/client/tests/fixtures/msgpack/player_input_interact.msgpack
@@ -0,0 +1 @@
+��tick�action��Interact��target_entity_idc�verb�Talk
\ No newline at end of file
diff --git a/client/tests/fixtures/msgpack/player_input_move.msgpack b/client/tests/fixtures/msgpack/player_input_move.msgpack
new file mode 100644
index 000000000..2d733e444
--- /dev/null
+++ b/client/tests/fixtures/msgpack/player_input_move.msgpack
@@ -0,0 +1 @@
+��tick
�action�MoveNorth
\ No newline at end of file
diff --git a/client/tests/fixtures/msgpack/snapshot_full.msgpack b/client/tests/fixtures/msgpack/snapshot_full.msgpack
new file mode 100644
index 000000000..88d7aaa31
Binary files /dev/null and b/client/tests/fixtures/msgpack/snapshot_full.msgpack differ
diff --git a/client/tests/fixtures/msgpack/snapshot_minimal.msgpack b/client/tests/fixtures/msgpack/snapshot_minimal.msgpack
new file mode 100644
index 000000000..3e54cc521
Binary files /dev/null and b/client/tests/fixtures/msgpack/snapshot_minimal.msgpack differ
diff --git a/client/tests/test_ipc_fixtures.gd b/client/tests/test_ipc_fixtures.gd
new file mode 100644
index 000000000..12594b279
--- /dev/null
+++ b/client/tests/test_ipc_fixtures.gd
@@ -0,0 +1,182 @@
+## D-030 Layer 1: Cross-language IPC fixture tests (#271)
+## Validates that Protocol.gd decodes the #271 named fixtures identically to Rust.
+## Fixtures generated by: cargo test --test gen_fixtures -- --ignored
+## Rust validation: server/tests/serialization.rs (fixture_* tests)
+class_name TestIpcFixtures
+extends GdUnitTestSuite
+
+const FIXTURE_DIR = "res://tests/fixtures/msgpack/"
+
+
+func _load_fixture(name: String) -> PackedByteArray:
+	var path = FIXTURE_DIR + name + ".msgpack"
+	var file = FileAccess.open(path, FileAccess.READ)
+	assert_that(file).is_not_null().override_failure_message(
+		"Fixture not found: %s — run 'make fixtures' to regenerate" % path
+	)
+	return file.get_buffer(file.get_length())
+
+
+# -- snapshot_minimal ----------------------------------------------------------
+
+func test_fixture_snapshot_minimal_version() -> void:
+	var bytes = _load_fixture("snapshot_minimal")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	assert_that(snapshot).is_not_null()
+	assert_that(snapshot.version).is_equal(Protocol.PROTOCOL_VERSION)
+
+
+func test_fixture_snapshot_minimal_tick() -> void:
+	var bytes = _load_fixture("snapshot_minimal")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	assert_that(snapshot.tick).is_equal(0)
+
+
+func test_fixture_snapshot_minimal_entity_count() -> void:
+	var bytes = _load_fixture("snapshot_minimal")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	assert_that(snapshot.entities.size()).is_equal(1)
+
+
+func test_fixture_snapshot_minimal_entity_kind() -> void:
+	var bytes = _load_fixture("snapshot_minimal")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	var entity = snapshot.entities[0]
+	assert_that(entity.entity_id).is_equal(1)
+	# entity.kind is {"variant": "Player", "data": null} from _decode_enum_variant
+	assert_that(entity.kind.variant).is_equal("Player")
+
+
+func test_fixture_snapshot_minimal_no_monologue() -> void:
+	var bytes = _load_fixture("snapshot_minimal")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	assert_that(snapshot.current_monologue).is_null()
+
+
+func test_fixture_snapshot_minimal_no_dialogue() -> void:
+	var bytes = _load_fixture("snapshot_minimal")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	assert_that(snapshot.dialogue_response).is_null()
+
+
+# -- snapshot_full -------------------------------------------------------------
+
+func test_fixture_snapshot_full_tick() -> void:
+	var bytes = _load_fixture("snapshot_full")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	assert_that(snapshot).is_not_null()
+	assert_that(snapshot.tick).is_equal(42)
+
+
+func test_fixture_snapshot_full_monologue_id() -> void:
+	var bytes = _load_fixture("snapshot_full")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	assert_that(snapshot.current_monologue).is_not_null()
+	assert_that(snapshot.current_monologue.id).is_equal("test_monologue_001")
+
+
+func test_fixture_snapshot_full_monologue_text() -> void:
+	var bytes = _load_fixture("snapshot_full")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	assert_that(snapshot.current_monologue.text).is_equal("Something feels off about this place.")
+
+
+func test_fixture_snapshot_full_dialogue_speaker() -> void:
+	var bytes = _load_fixture("snapshot_full")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	assert_that(snapshot.dialogue_response).is_not_null()
+	# dialogue_response has: line_id, text, speaker_entity_id (per protocol.gd v8 decode)
+	assert_that(snapshot.dialogue_response.speaker_entity_id).is_equal(99)
+
+
+func test_fixture_snapshot_full_inventory() -> void:
+	var bytes = _load_fixture("snapshot_full")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	assert_that(snapshot.player_inventory.size()).is_equal(1)
+	assert_that(snapshot.player_inventory[0].name).is_equal("Forged Customs Cert")
+
+
+func test_fixture_snapshot_full_poi_list() -> void:
+	var bytes = _load_fixture("snapshot_full")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	assert_that(snapshot.poi_list.size()).is_equal(1)
+	assert_that(snapshot.poi_list[0].poi_id).is_equal("docking_bay_7")
+
+
+func test_fixture_snapshot_full_player_knowledge_entity() -> void:
+	var bytes = _load_fixture("snapshot_full")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	assert_that(snapshot.player_knowledge).is_not_null()
+	assert_that(snapshot.player_knowledge.entities.size()).is_equal(1)
+	assert_that(snapshot.player_knowledge.entities[0].name).is_equal("Kael")
+
+
+func test_fixture_snapshot_full_player_knowledge_fact() -> void:
+	var bytes = _load_fixture("snapshot_full")
+	var snapshot = Protocol.decode_snapshot(bytes)
+	assert_that(snapshot.player_knowledge.facts.size()).is_equal(1)
+	assert_that(snapshot.player_knowledge.facts[0].fact_id).is_equal("poi.docking_bay_7")
+
+
+# -- player_input_move ---------------------------------------------------------
+
+func test_fixture_player_input_move_tick() -> void:
+	var bytes = _load_fixture("player_input_move")
+	var input = Protocol.decode_player_input(bytes)
+	assert_that(input).is_not_null()
+	assert_that(input.tick).is_equal(1)
+
+
+func test_fixture_player_input_move_action() -> void:
+	var bytes = _load_fixture("player_input_move")
+	var input = Protocol.decode_player_input(bytes)
+	# action is {"variant": "MoveNorth", "data": null} from _decode_enum_variant
+	assert_that(input.action.variant).is_equal("MoveNorth")
+
+
+# -- player_input_interact -----------------------------------------------------
+
+func test_fixture_player_input_interact_tick() -> void:
+	var bytes = _load_fixture("player_input_interact")
+	var input = Protocol.decode_player_input(bytes)
+	assert_that(input).is_not_null()
+	assert_that(input.tick).is_equal(2)
+
+
+func test_fixture_player_input_interact_action() -> void:
+	var bytes = _load_fixture("player_input_interact")
+	var input = Protocol.decode_player_input(bytes)
+	# Interact is a struct variant: {"variant": "Interact", "data": {"target_entity_id": 99, "verb": "Talk"}}
+	assert_that(input.action.variant).is_equal("Interact")
+
+
+func test_fixture_player_input_interact_target() -> void:
+	var bytes = _load_fixture("player_input_interact")
+	var input = Protocol.decode_player_input(bytes)
+	assert_that(input.action.data.target_entity_id).is_equal(99)
+
+
+func test_fixture_player_input_interact_verb() -> void:
+	var bytes = _load_fixture("player_input_interact")
+	var input = Protocol.decode_player_input(bytes)
+	assert_that(input.action.data.verb).is_equal("Talk")
+
+
+# -- malformed -----------------------------------------------------------------
+
+func test_fixture_malformed_snapshot_fails() -> void:
+	var bytes = _load_fixture("malformed")
+	# Intentionally truncated — decode_snapshot must return null (not crash)
+	var result = Protocol.decode_snapshot(bytes)
+	assert_that(result).is_null().override_failure_message(
+		"malformed fixture should not decode as a valid ObserverSnapshot"
+	)
+
+
+func test_fixture_malformed_input_fails() -> void:
+	var bytes = _load_fixture("malformed")
+	# Intentionally truncated — decode_player_input must return null (not crash)
+	var result = Protocol.decode_player_input(bytes)
+	assert_that(result).is_null().override_failure_message(
+		"malformed fixture should not decode as a valid PlayerInput"
+	)
diff --git a/docs/DEVOPS.md b/docs/DEVOPS.md
index 21d44a440..1e3659119 100644
--- a/docs/DEVOPS.md
+++ b/docs/DEVOPS.md
@@ -62,11 +62,27 @@ The server must be running before the client connects (subprocess launch will be
 ### Test
 
 ```bash
-make test               # Run all tests
-make test-server        # cargo test in server/
-make test-client        # gdUnit4 tests (headless runner pending)
+make test               # Run all tests (test-server + test-client)
+make test-server        # Rust tests via tests/run-rust (cargo nextest, JSON summary)
+make test-client        # Godot tests via tests/run-godot (gdUnit4 headless, JSON summary)
 ```
 
+The IPC test layers (D-030) have dedicated targets:
+
+```bash
+make test-ipc-fixtures      # Layer 1: serialization round-trip fixtures
+make test-ipc-protocol      # Layer 2: mock LocalBridge protocol tests
+make test-ipc-integration   # Layer 3: real subprocess round-trip (+ benchmark when ready)
+make test-ipc-benchmark     # IPC latency benchmark (blocked: #555/#556 handshake)
+```
+
+Each `tests/run-*` script outputs a JSON summary to stdout and streams progress to stderr:
+```json
+{"suite":"rust","total":42,"passed":42,"failed":0,"duration_ms":1230}
+```
+
+All scripts accept `--filter <name>` to run a subset of tests. They are whitelistable for agent use (no TTY prompts, no interactive input).
+
 Server tests use Rust's built-in test framework with `#[cfg(test)]` inline tests and `tests/` integration tests (D-030). Client tests use gdUnit4 (D-030).
 
 ### Cross-Encoder Fixtures
diff --git a/server/src/perception/observer/mod.rs b/server/src/perception/observer/mod.rs
index 6d07f11fa..32b552515 100644
--- a/server/src/perception/observer/mod.rs
+++ b/server/src/perception/observer/mod.rs
@@ -203,7 +203,13 @@ pub fn compute_observer_snapshot(
 
     let current_monologue = monologue_buffer.take();
     let dialogue_response = dialogue_response_opt.as_mut().and_then(|buf| buf.take());
-    let examine_result = examine_result_buffer_opt.as_mut().and_then(|buf| buf.take());
+    let examine_result = examine_result_buffer_opt.as_mut().and_then(|buf| buf.take()).map(
+        |evt| crate::bridge::types::ExamineResultWire {
+            entity_id: evt.target_entity_id,
+            text: evt.text,
+            confidence: crate::knowledge::types::KnowledgeConfidence::KnowsDetails,
+        },
+    );
     let scan_events = scan_event_buffer_opt
         .as_mut()
         .map(|buf| buf.take())
@@ -405,13 +411,7 @@ pub fn compute_observer_snapshot(
         sound_events,
         rng_seed: sim_rng.as_deref().map(|r| r.seed()),
         poi_list,
-        examine_result: examine_result.map(|e| {
-            crate::bridge::types::ExamineResultWire {
-                entity_id: e.target_entity_id,
-                text: e.text,
-                confidence: crate::bridge::types::KnowledgeConfidence::Direct,
-            }
-        }),
+        examine_result,
         player_knowledge,
         save_result,
     });
diff --git a/server/tests/gen_fixtures.rs b/server/tests/gen_fixtures.rs
index 642906ad0..ed309fe3b 100644
--- a/server/tests/gen_fixtures.rs
+++ b/server/tests/gen_fixtures.rs
@@ -2,6 +2,7 @@
 //! Run with: cargo test --test gen_fixtures -- --ignored
 
 use settled_reach_server::bridge::types::*;
+use settled_reach_server::simulation::poi::PoiCategory;
 use settled_reach_server::simulation::time::{DayPhase, TickRate};
 use std::fs;
 use std::path::Path;
@@ -287,6 +288,151 @@ fn generate_msgpack_fixtures() {
         write_fixture(name, &rmp_serde::to_vec_named(&input).unwrap());
     }
 
+    // === #271 fixtures: named fixtures for cross-language Layer 1 testing ===
+
+    // snapshot_minimal: version=14, tick=0, one Player entity, all optionals absent
+    let snapshot_minimal = fixture_snapshot(
+        0,
+        vec![VisibleEntity {
+            entity_id: 1,
+            x: 0.0,
+            y: 0.0,
+            z: 0,
+            kind: EntityKind::Player,
+            visibility: VisibilitySector::Forward,
+            relationship: RelationshipState::Unknown,
+            observation: EntityVisibility::Visible,
+            tell_state: None,
+        }],
+    );
+    write_fixture(
+        "snapshot_minimal",
+        &rmp_serde::to_vec_named(&snapshot_minimal).unwrap(),
+    );
+
+    // snapshot_full: version=14, tick=42, monologue + dialogue + inventory + POIs + KG dump
+    let snapshot_full = ObserverSnapshot {
+        version: PROTOCOL_VERSION,
+        tick: 42,
+        game_time: GameTime {
+            day: 3,
+            time_of_day: 840,
+            day_phase: DayPhase::Evening,
+            tick_rate: TickRate::Full,
+        },
+        player_facing: FacingDirection::East,
+        player_stance: MovementStance::Walk,
+        player_inventory: vec![InventoryItem {
+            item_id: 7,
+            name: "Forged Customs Cert".to_string(),
+            slot: 0,
+        }],
+        entities: vec![VisibleEntity {
+            entity_id: 1,
+            x: 10.0,
+            y: 10.0,
+            z: 0,
+            kind: EntityKind::Player,
+            visibility: VisibilitySector::Forward,
+            relationship: RelationshipState::Unknown,
+            observation: EntityVisibility::Visible,
+            tell_state: None,
+        }],
+        visible_tiles: vec![],
+        nearby_interactions: vec![],
+        current_monologue: Some(MonologueEvent {
+            id: "test_monologue_001".to_string(),
+            text: "Something feels off about this place.".to_string(),
+            duration_seconds: 4.0,
+        }),
+        pending_recognitions: vec![PendingRecognitionWire {
+            entity_id: 7,
+            x: 12.0,
+            y: 8.0,
+            z: 0,
+            remaining_ticks: 3,
+            total_delay_ticks: 10,
+        }],
+        dialogue_response: Some(DialogueResponseEvent {
+            line_id: "kael_d_001".to_string(),
+            text: "We need to talk about the shipment.".to_string(),
+            speaker_entity_id: 99,
+            speaker_color_index: 2,
+            speaker_name: "Kael".to_string(),
+        }),
+        blocked_entities: vec![5, 6],
+        scan_events: vec![],
+        sound_events: vec![],
+        conversation_events: vec![],
+        conversation_ended: vec![],
+        follow_state: None,
+        character_pressure: None,
+        rng_seed: Some(0xDEADBEEF),
+        poi_list: vec![PoiWire {
+            poi_id: "docking_bay_7".to_string(),
+            name: "Docking Bay 7".to_string(),
+            x: 50,
+            y: 30,
+            z: 0,
+            category: PoiCategory::Location,
+        }],
+        examine_result: Some(ExamineResultWire {
+            entity_id: 42,
+            text: "A smuggler, probably. The way they hold themselves.".to_string(),
+            confidence: KnowledgeConfidence::KnowsOf,
+        }),
+        save_result: None,
+        player_knowledge: Some(PlayerKnowledgeWire {
+            entities: vec![KnownEntityWire {
+                entity_id: 99,
+                name: "Kael".to_string(),
+                confidence: KnowledgeConfidence::KnowsDetails,
+                source: "DirectObservation".to_string(),
+                state: KnowledgeState::Active,
+                relationship: RelationshipState::Known,
+                last_observed_tick: 40,
+            }],
+            facts: vec![KnownFactWire {
+                fact_id: "poi.docking_bay_7".to_string(),
+                confidence: KnowledgeConfidence::KnowsOf,
+                source: "DirectObservation".to_string(),
+                state: KnowledgeState::Active,
+                acquired_tick: 10,
+            }],
+        }),
+    };
+    write_fixture(
+        "snapshot_full",
+        &rmp_serde::to_vec_named(&snapshot_full).unwrap(),
+    );
+
+    // player_input_move: tick=1, MoveNorth
+    let input_move = PlayerInput {
+        tick: 1,
+        action: PlayerAction::MoveNorth,
+    };
+    write_fixture(
+        "player_input_move",
+        &rmp_serde::to_vec_named(&input_move).unwrap(),
+    );
+
+    // player_input_interact: tick=2, Interact { target: 99, verb: "Talk" }
+    let input_interact = PlayerInput {
+        tick: 2,
+        action: PlayerAction::Interact {
+            target_entity_id: Some(99),
+            verb: Some("Talk".to_string()),
+        },
+    };
+    write_fixture(
+        "player_input_interact",
+        &rmp_serde::to_vec_named(&input_interact).unwrap(),
+    );
+
+    // malformed: intentionally truncated bytes — tests error handling in both Rust and GDScript
+    // 0x82 = fixmap with 2 entries, 0xa4 = fixstr of length 4 — incomplete map, no key/value follows
+    write_fixture("malformed", &[0x82u8, 0xa4u8]);
+
     // === Boundary value fixtures (#472) ===
     // 14 raw integer values at encoding format boundaries (Appendix C).
     // These are Rust-encoded MessagePack that GDScript must decode correctly.
diff --git a/server/tests/ipc_bench.rs b/server/tests/ipc_bench.rs
new file mode 100644
index 000000000..4f9ffee6d
--- /dev/null
+++ b/server/tests/ipc_bench.rs
@@ -0,0 +1,199 @@
+//! IPC round-trip latency benchmark (#342, D-020)
+//!
+//! Measures end-to-end latency from client send (write_framed) to client receive
+//! (read_framed) over the real subprocess IPC channel. Reports p50/p95/p99.
+//!
+//! Latency budget: p99 must be <= 5ms (D-020: "~1-5ms serialization latency per tick").
+//!
+//! Run with:
+//!   cargo test --release --test ipc_bench -- --ignored --nocapture
+//!
+//! Output: IPC_BENCH_RESULT:{json} on a single line for tooling to parse.
+//!
+//!
+//! Spec references: D-020 (subprocess IPC, 5ms budget), D-030 (Layer 3)
+
+use settled_reach_server::bridge::framing::{read_framed, write_framed};
+use settled_reach_server::bridge::types::*;
+use std::io::{BufRead, BufReader, BufWriter};
+use std::net::TcpStream;
+use std::process::{Command, Stdio};
+use std::time::{Duration, Instant};
+
+/// Number of warmup round-trips before timing begins.
+const WARMUP_ROUNDS: usize = 10;
+
+/// Number of timed round-trips (N in the spec).
+const MEASURE_ROUNDS: usize = 100;
+
+/// Latency threshold (p99 must be below this). D-020: "~1-5ms per tick".
+const THRESHOLD_MS: f64 = 5.0;
+
+/// Timeout for the server to emit LISTENING:{port} on stdout.
+const LISTEN_TIMEOUT: Duration = Duration::from_secs(15);
+
+/// Timeout per round-trip read.
+const ROUND_TRIP_TIMEOUT: Duration = Duration::from_secs(5);
+
+fn percentile(sorted: &[f64], p: f64) -> f64 {
+    if sorted.is_empty() {
+        return 0.0;
+    }
+    let idx = ((sorted.len() - 1) as f64 * p).floor() as usize;
+    sorted[idx.min(sorted.len() - 1)]
+}
+
+#[test]
+#[ignore]
+fn ipc_round_trip_latency() {
+    // 1. Spawn server binary with --test-mode --port 0
+    let server_bin = env!("CARGO_BIN_EXE_settled-reach-server");
+    let mut child = Command::new(server_bin)
+        .args(["--test-mode", "--port", "0"])
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()
+        .expect("failed to spawn server binary");
+
+    let stdout = child.stdout.take().expect("stdout not captured");
+    let mut stdout_reader = BufReader::new(stdout);
+
+    // 2. Parse LISTENING:{port} from stdout
+    let port = {
+        let deadline = Instant::now() + LISTEN_TIMEOUT;
+        let mut line = String::new();
+        loop {
+            line.clear();
+            match stdout_reader.read_line(&mut line) {
+                Ok(0) => panic!("server stdout closed before LISTENING signal"),
+                Ok(_) => {
+                    let trimmed = line.trim();
+                    if let Some(port_str) = trimmed.strip_prefix("LISTENING:") {
+                        break port_str
+                            .parse::<u16>()
+                            .unwrap_or_else(|e| panic!("invalid port '{}': {}", port_str, e));
+                    }
+                }
+                Err(e) => panic!("failed to read server stdout: {}", e),
+            }
+            assert!(
+                Instant::now() < deadline,
+                "timed out waiting for LISTENING signal"
+            );
+        }
+    };
+
+    // 3. Connect via TCP
+    let addr = format!("127.0.0.1:{}", port);
+    let stream = TcpStream::connect(&addr)
+        .unwrap_or_else(|e| panic!("failed to connect to {}: {}", addr, e));
+    stream
+        .set_read_timeout(Some(ROUND_TRIP_TIMEOUT))
+        .expect("set read timeout");
+
+    let mut reader = BufReader::new(stream.try_clone().expect("clone stream"));
+    let mut writer = BufWriter::new(stream);
+
+    // 4. Handshake: read and validate HandshakeMessage before timing (#555/#556).
+    // Server sends HandshakeMessage { protocol_version } as the very first framed message.
+    let handshake_bytes = read_framed(&mut reader)
+        .expect("read handshake")
+        .expect("server closed before sending HandshakeMessage");
+    let handshake: HandshakeMessage =
+        rmp_serde::from_slice(&handshake_bytes).expect("deserialize HandshakeMessage");
+    assert_eq!(
+        handshake.protocol_version,
+        PROTOCOL_VERSION,
+        "handshake version mismatch: server={}, client={}",
+        handshake.protocol_version,
+        PROTOCOL_VERSION
+    );
+
+    let make_input = |tick: u64| PlayerInput {
+        tick,
+        action: PlayerAction::MoveNorth,
+    };
+
+    let mut round_trip_ms: Vec<f64> = Vec::with_capacity(WARMUP_ROUNDS + MEASURE_ROUNDS);
+
+    // 5. Warmup rounds (not timed)
+    for tick in 0..WARMUP_ROUNDS as u64 {
+        let payload =
+            rmp_serde::to_vec_named(&vec![make_input(tick)]).expect("serialize PlayerInput");
+        write_framed(&mut writer, &payload).expect("send warmup input");
+        let _ = read_framed(&mut reader)
+            .expect("read warmup snapshot")
+            .expect("server closed during warmup");
+    }
+
+    // 6. Timed measurement rounds
+    for tick in WARMUP_ROUNDS as u64..(WARMUP_ROUNDS + MEASURE_ROUNDS) as u64 {
+        let payload =
+            rmp_serde::to_vec_named(&vec![make_input(tick)]).expect("serialize PlayerInput");
+
+        let t_send = Instant::now();
+        write_framed(&mut writer, &payload).expect("send timed input");
+        let response = read_framed(&mut reader)
+            .expect("read timed snapshot")
+            .expect("server closed during measurement");
+        let elapsed_ms = t_send.elapsed().as_secs_f64() * 1000.0;
+
+        // Verify we received a valid snapshot (not just noise)
+        let _snapshot: ObserverSnapshot =
+            rmp_serde::from_slice(&response).expect("deserialize ObserverSnapshot");
+
+        round_trip_ms.push(elapsed_ms);
+    }
+
+    // 7. Clean up
+    drop(reader);
+    drop(writer);
+    let exit_deadline = Instant::now() + Duration::from_secs(5);
+    loop {
+        match child.try_wait() {
+            Ok(Some(_)) => break,
+            Ok(None) => {
+                if Instant::now() > exit_deadline {
+                    child.kill().ok();
+                    child.wait().ok();
+                    break;
+                }
+                std::thread::sleep(Duration::from_millis(50));
+            }
+            Err(_) => {
+                child.kill().ok();
+                break;
+            }
+        }
+    }
+
+    // 8. Compute percentiles
+    let mut sorted = round_trip_ms.clone();
+    sorted.sort_by(|a, b| a.partial_cmp(b).unwrap());
+
+    let p50 = percentile(&sorted, 0.50);
+    let p95 = percentile(&sorted, 0.95);
+    let p99 = percentile(&sorted, 0.99);
+    let passed = p99 <= THRESHOLD_MS;
+
+    let result = serde_json::json!({
+        "p50_ms": (p50 * 100.0).round() / 100.0,
+        "p95_ms": (p95 * 100.0).round() / 100.0,
+        "p99_ms": (p99 * 100.0).round() / 100.0,
+        "threshold_ms": THRESHOLD_MS,
+        "passed": passed,
+        "rounds": MEASURE_ROUNDS,
+    });
+
+    println!(
+        "IPC_BENCH_RESULT:{}",
+        serde_json::to_string(&result).unwrap()
+    );
+
+    // Fail the test if we exceed the latency budget
+    assert!(
+        passed,
+        "IPC latency budget exceeded: p99={:.2}ms > threshold={}ms",
+        p99, THRESHOLD_MS
+    );
+}
diff --git a/server/tests/serialization.rs b/server/tests/serialization.rs
index 8a505e69b..7b6ec17fa 100644
--- a/server/tests/serialization.rs
+++ b/server/tests/serialization.rs
@@ -180,13 +180,15 @@ fn all_fixtures_deserialize() {
         } else if name.starts_with("input_batch") {
             rmp_serde::from_slice::<Vec<PlayerInput>>(&bytes)
                 .unwrap_or_else(|e| panic!("deserialize batch input fixture {}: {}", name, e));
-        } else if name.starts_with("input") {
+        } else if name.starts_with("input") || name.starts_with("player_input") {
             rmp_serde::from_slice::<PlayerInput>(&bytes)
                 .unwrap_or_else(|e| panic!("deserialize input fixture {}: {}", name, e));
         } else if name.starts_with("boundary_raw") {
             // Raw integer boundary fixtures (#472): single u64 values
             rmp_serde::from_slice::<u64>(&bytes)
                 .unwrap_or_else(|e| panic!("deserialize boundary raw fixture {}: {}", name, e));
+        } else if name == "malformed" {
+            // Intentionally truncated — skip deserialization check, error handling tested elsewhere
         } else {
             panic!(
                 "unknown fixture naming convention: {} — add a deserialization branch for this prefix",
@@ -1400,7 +1402,7 @@ fn serde_default_fields_fill_in_when_missing_from_wire() {
     // `tell_state`, `follow_state`, `rng_seed`, `zone_id`, `object_type`, etc.
     // are all `#[serde(default)]` — they must default to None/empty when absent.
     let minimal_json = serde_json::json!({
-        "version": 14,
+        "version": 13,
         "tick": 42,
         "game_time": {
             "day": 0,
@@ -1440,7 +1442,7 @@ fn serde_default_fields_fill_in_when_missing_from_wire() {
         serde_json::from_value(minimal_json).expect("minimal JSON must deserialize");
 
     // Version matches what was in the wire
-    assert_eq!(decoded.version, 14);
+    assert_eq!(decoded.version, 13);
     assert_eq!(decoded.tick, 42);
     assert_eq!(decoded.entities.len(), 1);
 
@@ -1648,3 +1650,142 @@ fn nearby_interaction_object_type_roundtrip() {
         Some(ObjectType::Container)
     );
 }
+
+// ============================================================
+// #271: Named fixture validation tests (D-030 Layer 1)
+//
+// These tests read the committed .msgpack files and assert specific field
+// values. They serve as the Rust side of cross-language verification — the
+// same fixtures are decoded by client/tests/test_ipc_fixtures.gd.
+// ============================================================
+
+fn read_named_fixture(name: &str) -> Vec<u8> {
+    let path = format!("../client/tests/fixtures/msgpack/{}.msgpack", name);
+    fs::read(&path).unwrap_or_else(|e| panic!("failed to read fixture '{}': {}", name, e))
+}
+
+#[test]
+fn fixture_snapshot_minimal_fields() {
+    let bytes = read_named_fixture("snapshot_minimal");
+    let snap: ObserverSnapshot =
+        rmp_serde::from_slice(&bytes).expect("deserialize snapshot_minimal");
+
+    assert_eq!(snap.version, PROTOCOL_VERSION, "protocol version mismatch");
+    assert_eq!(snap.tick, 0, "tick should be 0");
+    assert_eq!(snap.entities.len(), 1, "should have exactly 1 entity");
+    assert_eq!(snap.entities[0].entity_id, 1);
+    assert!(
+        matches!(snap.entities[0].kind, EntityKind::Player),
+        "entity should be Player kind"
+    );
+    assert!(snap.current_monologue.is_none(), "no monologue in minimal");
+    assert!(snap.dialogue_response.is_none(), "no dialogue in minimal");
+    assert!(snap.player_inventory.is_empty(), "no inventory in minimal");
+    assert!(snap.poi_list.is_empty(), "no POIs in minimal");
+    assert!(snap.player_knowledge.is_none(), "no KG in minimal");
+}
+
+#[test]
+fn fixture_snapshot_full_fields() {
+    let bytes = read_named_fixture("snapshot_full");
+    let snap: ObserverSnapshot =
+        rmp_serde::from_slice(&bytes).expect("deserialize snapshot_full");
+
+    assert_eq!(snap.version, PROTOCOL_VERSION, "protocol version mismatch");
+    assert_eq!(snap.tick, 42, "tick should be 42");
+
+    // Monologue
+    let monologue = snap.current_monologue.as_ref().expect("monologue absent");
+    assert_eq!(monologue.id, "test_monologue_001");
+    assert_eq!(
+        monologue.text,
+        "Something feels off about this place."
+    );
+
+    // Dialogue
+    let dialogue = snap.dialogue_response.as_ref().expect("dialogue absent");
+    assert_eq!(dialogue.speaker_entity_id, 99);
+    assert_eq!(dialogue.speaker_name, "Kael");
+
+    // Inventory
+    assert_eq!(snap.player_inventory.len(), 1);
+    assert_eq!(snap.player_inventory[0].name, "Forged Customs Cert");
+
+    // POIs
+    assert_eq!(snap.poi_list.len(), 1);
+    assert_eq!(snap.poi_list[0].poi_id, "docking_bay_7");
+
+    // Examine result
+    let examine = snap.examine_result.as_ref().expect("examine_result absent");
+    assert_eq!(examine.entity_id, 42);
+
+    // Player knowledge
+    let kg = snap.player_knowledge.as_ref().expect("player_knowledge absent");
+    assert_eq!(kg.entities.len(), 1);
+    assert_eq!(kg.entities[0].name, "Kael");
+    assert_eq!(kg.facts.len(), 1);
+    assert_eq!(kg.facts[0].fact_id, "poi.docking_bay_7");
+
+    // RNG seed
+    assert_eq!(snap.rng_seed, Some(0xDEADBEEF));
+
+    // Pending recognitions
+    assert_eq!(snap.pending_recognitions.len(), 1);
+    assert_eq!(snap.pending_recognitions[0].entity_id, 7);
+
+    // Blocked entities
+    assert_eq!(snap.blocked_entities, vec![5u64, 6]);
+}
+
+#[test]
+fn fixture_player_input_move_fields() {
+    let bytes = read_named_fixture("player_input_move");
+    let input: PlayerInput =
+        rmp_serde::from_slice(&bytes).expect("deserialize player_input_move");
+
+    assert_eq!(input.tick, 1, "tick should be 1");
+    assert!(
+        matches!(input.action, PlayerAction::MoveNorth),
+        "action should be MoveNorth"
+    );
+}
+
+#[test]
+fn fixture_player_input_interact_fields() {
+    let bytes = read_named_fixture("player_input_interact");
+    let input: PlayerInput =
+        rmp_serde::from_slice(&bytes).expect("deserialize player_input_interact");
+
+    assert_eq!(input.tick, 2, "tick should be 2");
+    match &input.action {
+        PlayerAction::Interact {
+            target_entity_id,
+            verb,
+        } => {
+            assert_eq!(*target_entity_id, Some(99u64), "target_entity_id should be Some(99)");
+            assert_eq!(
+                verb.as_deref(),
+                Some("Talk"),
+                "verb should be Some(\"Talk\")"
+            );
+        }
+        other => panic!("expected Interact, got {:?}", other),
+    }
+}
+
+#[test]
+fn fixture_malformed_fails_deserialization() {
+    let bytes = read_named_fixture("malformed");
+    // Intentionally truncated — must NOT deserialize as ObserverSnapshot
+    let result = rmp_serde::from_slice::<ObserverSnapshot>(&bytes);
+    assert!(
+        result.is_err(),
+        "malformed fixture should fail to deserialize as ObserverSnapshot"
+    );
+    // Also must NOT deserialize as PlayerInput
+    let result2 = rmp_serde::from_slice::<PlayerInput>(&bytes);
+    assert!(
+        result2.is_err(),
+        "malformed fixture should fail to deserialize as PlayerInput"
+    );
+}
diff --git a/tests/run-all b/tests/run-all
new file mode 100755
index 000000000..b296cfb22
--- /dev/null
+++ b/tests/run-all
@@ -0,0 +1,77 @@
+#!/usr/bin/env bash
+# tests/run-all: Run all test suites in order (D-030)
+# Invokes run-rust, run-godot, run-ipc-fixtures, run-ipc-protocol, run-ipc-integration.
+# Exit: 0 = all suites pass, non-zero = any suite failed
+# Stdout: {"suite":"all","total":N,"passed":N,"failed":N,"duration_ms":N,"suites":[...]}
+set -euo pipefail
+
+FILTER=""
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --filter) FILTER="${2:-}"; shift 2 ;;
+        --filter=*) FILTER="${1#--filter=}"; shift ;;
+        *) echo "Unknown argument: $1" >&2; exit 2 ;;
+    esac
+done
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+PASS_ARGS=()
+[[ -n "$FILTER" ]] && PASS_ARGS+=(--filter "$FILTER")
+
+SUITES=(
+    run-rust
+    run-godot
+    run-ipc-fixtures
+    run-ipc-protocol
+    run-ipc-integration
+)
+
+START_MS=$(date +%s%3N)
+
+OVERALL_TOTAL=0
+OVERALL_PASSED=0
+OVERALL_FAILED=0
+OVERALL_EXIT=0
+SUITE_RESULTS=""
+
+for suite in "${SUITES[@]}"; do
+    script="$SCRIPT_DIR/$suite"
+    if [[ ! -x "$script" ]]; then
+        echo "Warning: $script not found or not executable — skipping" >&2
+        continue
+    fi
+
+    SUITE_OUT=$(mktemp)
+    set +e
+    "$script" "${PASS_ARGS[@]}" >"$SUITE_OUT"
+    SUITE_EXIT=$?
+    set -e
+
+    SUITE_JSON=$(cat "$SUITE_OUT")
+    rm -f "$SUITE_OUT"
+
+    # Accumulate totals from the suite's JSON output
+    S_TOTAL=$(echo "$SUITE_JSON" | grep -oE '"total":[0-9]+' | grep -oE '[0-9]+' || echo 0)
+    S_PASSED=$(echo "$SUITE_JSON" | grep -oE '"passed":[0-9]+' | grep -oE '[0-9]+' || echo 0)
+    S_FAILED=$(echo "$SUITE_JSON" | grep -oE '"failed":[0-9]+' | grep -oE '[0-9]+' || echo 0)
+
+    OVERALL_TOTAL=$(( OVERALL_TOTAL + ${S_TOTAL:-0} ))
+    OVERALL_PASSED=$(( OVERALL_PASSED + ${S_PASSED:-0} ))
+    OVERALL_FAILED=$(( OVERALL_FAILED + ${S_FAILED:-0} ))
+    [[ $SUITE_EXIT -ne 0 ]] && OVERALL_EXIT=1
+
+    # Build suites array for JSON
+    if [[ -n "$SUITE_RESULTS" ]]; then
+        SUITE_RESULTS="$SUITE_RESULTS,$SUITE_JSON"
+    else
+        SUITE_RESULTS="$SUITE_JSON"
+    fi
+done
+
+END_MS=$(date +%s%3N)
+DURATION_MS=$((END_MS - START_MS))
+
+printf '{"suite":"all","total":%d,"passed":%d,"failed":%d,"duration_ms":%d,"suites":[%s]}\n' \
+    "$OVERALL_TOTAL" "$OVERALL_PASSED" "$OVERALL_FAILED" "$DURATION_MS" "$SUITE_RESULTS"
+exit $OVERALL_EXIT
diff --git a/tests/run-godot b/tests/run-godot
new file mode 100755
index 000000000..ee323e275
--- /dev/null
+++ b/tests/run-godot
@@ -0,0 +1,88 @@
+#!/usr/bin/env bash
+# tests/run-godot: Run Godot client test suite via gdUnit4 (D-030)
+# Exit: 0 = all pass, non-zero = failure
+# Stdout: {"suite":"godot","total":N,"passed":N,"failed":N,"duration_ms":N}
+#
+# --filter: accepts a test filename stem (e.g. "test_protocol" → runs test_protocol.gd only)
+set -euo pipefail
+
+FILTER=""
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --filter) FILTER="${2:-}"; shift 2 ;;
+        --filter=*) FILTER="${1#--filter=}"; shift ;;
+        *) echo "Unknown argument: $1" >&2; exit 2 ;;
+    esac
+done
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+
+GODOT=$(command -v godot4 2>/dev/null || command -v godot 2>/dev/null || echo "")
+if [[ -z "$GODOT" ]]; then
+    printf '{"suite":"godot","total":0,"passed":0,"failed":0,"duration_ms":0,"error":"godot not found in PATH"}\n'
+    exit 1
+fi
+
+# Resolve the test target: directory or specific file
+if [[ -n "$FILTER" ]]; then
+    # Support bare name (test_protocol) or full path (test_protocol.gd)
+    if [[ "$FILTER" == res://* ]]; then
+        TEST_TARGET="$FILTER"
+    elif [[ "$FILTER" == *.gd ]]; then
+        TEST_TARGET="res://tests/$FILTER"
+    else
+        TEST_TARGET="res://tests/${FILTER}.gd"
+    fi
+else
+    TEST_TARGET="res://tests/"
+fi
+
+START_MS=$(date +%s%3N)
+TMPOUT=$(mktemp)
+
+set +e
+"$GODOT" --headless --path "$REPO_ROOT/client" \
+    -s res://addons/gdUnit4/bin/GdUnitCmdTool.gd \
+    --ignoreHeadlessMode \
+    -c \
+    -a "$TEST_TARGET" \
+    2>&1 | tee "$TMPOUT" >&2
+EXIT_CODE=${PIPESTATUS[0]}
+set -e
+
+END_MS=$(date +%s%3N)
+DURATION_MS=$((END_MS - START_MS))
+
+_extract_num() {
+    local haystack="$1" pattern="$2"
+    echo "$haystack" | grep -oiE "[0-9]+ $pattern" | grep -oE '^[0-9]+' || echo 0
+}
+
+# gdUnit4 outputs per-suite statistics: "N test cases | X errors | Y failures | ..."
+# and a summary: "Executed test cases : (X/N)" or "Executed test cases : (X/N), Z skipped"
+TOTAL=0; PASSED=0; FAILED=0
+
+# Sum errors + failures across all suite statistics lines
+STATS_LINES=$(grep -oE "[0-9]+ test cases \| [0-9]+ errors \| [0-9]+ failures" "$TMPOUT" || true)
+if [[ -n "$STATS_LINES" ]]; then
+    TOTAL=$(echo "$STATS_LINES" | grep -oE '^[0-9]+' | awk '{s+=$1} END {print s}')
+    ERRORS=$(echo "$STATS_LINES" | grep -oE '[0-9]+ errors' | grep -oE '^[0-9]+' | awk '{s+=$1} END {print s}')
+    FAILURES=$(echo "$STATS_LINES" | grep -oE '[0-9]+ failures' | grep -oE '^[0-9]+' | awk '{s+=$1} END {print s}')
+    FAILED=$(( ${ERRORS:-0} + ${FAILURES:-0} ))
+    PASSED=$(( TOTAL - FAILED ))
+fi
+
+# Fallback: parse "Executed test cases : (X/N)" for total if stats parse failed
+if [[ "$TOTAL" -eq 0 ]]; then
+    EXEC_LINE=$(grep -oE "Executed test cases : \([0-9]+/[0-9]+\)" "$TMPOUT" | tail -1 || true)
+    if [[ -n "$EXEC_LINE" ]]; then
+        TOTAL=$(echo "$EXEC_LINE" | grep -oE '/[0-9]+\)' | grep -oE '[0-9]+')
+        PASSED=$(echo "$EXEC_LINE" | grep -oE '\([0-9]+/' | grep -oE '[0-9]+')
+        FAILED=$(( TOTAL - PASSED ))
+    fi
+fi
+
+rm -f "$TMPOUT"
+printf '{"suite":"godot","total":%d,"passed":%d,"failed":%d,"duration_ms":%d}\n' \
+    "${TOTAL:-0}" "${PASSED:-0}" "${FAILED:-0}" "$DURATION_MS"
+exit $EXIT_CODE
diff --git a/tests/run-ipc-benchmark b/tests/run-ipc-benchmark
new file mode 100755
index 000000000..dc638e83f
--- /dev/null
+++ b/tests/run-ipc-benchmark
@@ -0,0 +1,59 @@
+#!/usr/bin/env bash
+# tests/run-ipc-benchmark: IPC round-trip latency benchmark (#342, D-020)
+#
+# Runs server/tests/ipc_bench.rs via `cargo test --release --test ipc_bench`.
+# Parses IPC_BENCH_RESULT:{json} from output and outputs the result JSON.
+#
+# Latency budget: p99 <= 5ms (D-020: "~1-5ms serialization latency per tick").
+#
+# NOTE (#342): Handshake step is stubbed in ipc_bench.rs pending #555 (server
+# protocol handshake) and #556 (client handshake). Full clean timing requires
+# a working handshake before the measurement loop starts.
+#
+# Exit: 0 = benchmark passed (p99 within threshold), non-zero = failure
+# Stdout: {"p50_ms":N,"p95_ms":N,"p99_ms":N,"threshold_ms":5,"passed":true,"rounds":100}
+set -euo pipefail
+
+ITERATIONS=100
+THRESHOLD_MS=5
+
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --iterations) ITERATIONS="${2:-100}"; shift 2 ;;
+        --iterations=*) ITERATIONS="${1#--iterations=}"; shift ;;
+        --threshold-ms) THRESHOLD_MS="${2:-5}"; shift 2 ;;
+        --filter) shift 2 ;;        # ignored — benchmark has no test filter
+        --filter=*) shift ;;
+        *) echo "Unknown argument: $1" >&2; exit 2 ;;
+    esac
+done
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+
+START_MS=$(date +%s%3N)
+TMPOUT=$(mktemp)
+
+set +e
+cd "$REPO_ROOT/server" && \
+    cargo test --release --test ipc_bench -- --ignored --nocapture 2>&1 | tee "$TMPOUT" >&2
+EXIT_CODE=${PIPESTATUS[0]}
+set -e
+
+END_MS=$(date +%s%3N)
+DURATION_MS=$((END_MS - START_MS))
+
+# Extract IPC_BENCH_RESULT:{json} line from output
+RESULT_LINE=$(grep "^IPC_BENCH_RESULT:" "$TMPOUT" | tail -1 || true)
+rm -f "$TMPOUT"
+
+if [[ -n "$RESULT_LINE" ]]; then
+    # Strip the prefix and output the JSON
+    echo "${RESULT_LINE#IPC_BENCH_RESULT:}"
+else
+    # No result line — test failed to produce output
+    printf '{"p50_ms":0,"p95_ms":0,"p99_ms":0,"threshold_ms":%d,"passed":false,"error":"no benchmark output — server binary may not be built (run make build-server)"}\n' \
+        "$THRESHOLD_MS"
+    EXIT_CODE=1
+fi
+
+exit $EXIT_CODE
diff --git a/tests/run-ipc-fixtures b/tests/run-ipc-fixtures
new file mode 100755
index 000000000..6d76a073e
--- /dev/null
+++ b/tests/run-ipc-fixtures
@@ -0,0 +1,98 @@
+#!/usr/bin/env bash
+# tests/run-ipc-fixtures: Layer 1 IPC fixture tests (D-030)
+# Runs Rust serialization round-trip tests + GDScript fixture validation.
+# GDScript side is skipped if client/tests/test_ipc_fixtures.gd doesn't exist yet (#271).
+# Exit: 0 = all pass, non-zero = any failure
+# Stdout: {"suite":"ipc-fixtures","total":N,"passed":N,"failed":N,"duration_ms":N}
+set -euo pipefail
+
+FILTER=""
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --filter) FILTER="${2:-}"; shift 2 ;;
+        --filter=*) FILTER="${1#--filter=}"; shift ;;
+        *) echo "Unknown argument: $1" >&2; exit 2 ;;
+    esac
+done
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+
+_extract_num() {
+    local haystack="$1" pattern="$2"
+    echo "$haystack" | grep -oE "[0-9]+ $pattern" | grep -oE '^[0-9]+' || echo 0
+}
+
+_parse_nextest_summary() {
+    local tmpout="$1"
+    local summary total passed failed
+    summary=$(grep -E "^\s*(Summary|Finished)" "$tmpout" | tail -1 || true)
+    if [[ -n "$summary" ]]; then
+        total=$(_extract_num "$summary" "tests? run")
+        passed=$(_extract_num "$summary" "passed")
+        failed=$(_extract_num "$summary" "failed")
+    else
+        total=0; passed=0; failed=0
+    fi
+    echo "$total $passed $failed"
+}
+
+# --- Layer 1a: Rust serialization tests ---
+START_MS=$(date +%s%3N)
+
+cd "$REPO_ROOT/server"
+TMPOUT=$(mktemp)
+NEXTEST_ARGS=(nextest run --color never --test serialization)
+[[ -n "$FILTER" ]] && NEXTEST_ARGS+=(-E "test(~${FILTER})")
+
+set +e
+cargo "${NEXTEST_ARGS[@]}" 2>&1 | tee "$TMPOUT" >&2
+RUST_EXIT=${PIPESTATUS[0]}
+set -e
+
+read -r RUST_TOTAL RUST_PASSED RUST_FAILED < <(_parse_nextest_summary "$TMPOUT")
+rm -f "$TMPOUT"
+
+# --- Layer 1b: GDScript fixture tests (optional until #271 lands) ---
+GDS_FIXTURE="$REPO_ROOT/client/tests/test_ipc_fixtures.gd"
+GDS_TOTAL=0; GDS_PASSED=0; GDS_FAILED=0; GDS_EXIT=0
+
+if [[ -f "$GDS_FIXTURE" ]]; then
+    GODOT=$(command -v godot4 2>/dev/null || command -v godot 2>/dev/null || echo "")
+    if [[ -z "$GODOT" ]]; then
+        echo "Warning: test_ipc_fixtures.gd found but godot not in PATH — skipping GDScript layer" >&2
+    else
+        GDTMP=$(mktemp)
+        set +e
+        "$GODOT" --headless --path "$REPO_ROOT/client" \
+            -s res://addons/gdUnit4/bin/GdUnitCmdTool.gd \
+            --ignoreHeadlessMode -c \
+            -a res://tests/test_ipc_fixtures.gd \
+            2>&1 | tee "$GDTMP" >&2
+        GDS_EXIT=${PIPESTATUS[0]}
+        set -e
+
+        STATS=$(grep -oE "[0-9]+ test cases \| [0-9]+ errors \| [0-9]+ failures" "$GDTMP" || true)
+        if [[ -n "$STATS" ]]; then
+            GDS_TOTAL=$(echo "$STATS" | grep -oE '^[0-9]+' | awk '{s+=$1} END {print s}')
+            ERRS=$(echo "$STATS" | grep -oE '[0-9]+ errors' | grep -oE '^[0-9]+' | awk '{s+=$1} END {print s}')
+            FAILS=$(echo "$STATS" | grep -oE '[0-9]+ failures' | grep -oE '^[0-9]+' | awk '{s+=$1} END {print s}')
+            GDS_FAILED=$(( ${ERRS:-0} + ${FAILS:-0} ))
+            GDS_PASSED=$(( GDS_TOTAL - GDS_FAILED ))
+        fi
+        rm -f "$GDTMP"
+    fi
+fi
+
+END_MS=$(date +%s%3N)
+DURATION_MS=$((END_MS - START_MS))
+
+TOTAL=$(( RUST_TOTAL + GDS_TOTAL ))
+PASSED=$(( RUST_PASSED + GDS_PASSED ))
+FAILED=$(( RUST_FAILED + GDS_FAILED ))
+
+# Overall exit: fail if either side failed
+EXIT_CODE=$(( RUST_EXIT != 0 || GDS_EXIT != 0 ? 1 : 0 ))
+
+printf '{"suite":"ipc-fixtures","total":%d,"passed":%d,"failed":%d,"duration_ms":%d}\n' \
+    "$TOTAL" "$PASSED" "$FAILED" "$DURATION_MS"
+exit $EXIT_CODE
diff --git a/tests/run-ipc-integration b/tests/run-ipc-integration
new file mode 100755
index 000000000..5f0696e71
--- /dev/null
+++ b/tests/run-ipc-integration
@@ -0,0 +1,72 @@
+#!/usr/bin/env bash
+# tests/run-ipc-integration: Layer 3 real-subprocess integration tests (D-030)
+# Spawns the server binary as a real child process, runs IPC round-trip.
+# Also invokes tests/run-ipc-benchmark when that script exists (#342).
+# Exit: 0 = all pass, non-zero = any failure
+# Stdout: {"suite":"ipc-integration","total":N,"passed":N,"failed":N,"duration_ms":N}
+set -euo pipefail
+
+FILTER=""
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --filter) FILTER="${2:-}"; shift 2 ;;
+        --filter=*) FILTER="${1#--filter=}"; shift ;;
+        *) echo "Unknown argument: $1" >&2; exit 2 ;;
+    esac
+done
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "$REPO_ROOT/server"
+
+START_MS=$(date +%s%3N)
+TMPOUT=$(mktemp)
+
+NEXTEST_ARGS=(nextest run --color never --test layer3)
+[[ -n "$FILTER" ]] && NEXTEST_ARGS+=(-E "test(~${FILTER})")
+
+set +e
+cargo "${NEXTEST_ARGS[@]}" 2>&1 | tee "$TMPOUT" >&2
+LAYER3_EXIT=${PIPESTATUS[0]}
+set -e
+
+_extract_num() {
+    local haystack="$1" pattern="$2"
+    echo "$haystack" | grep -oE "[0-9]+ $pattern" | grep -oE '^[0-9]+' || echo 0
+}
+
+SUMMARY=$(grep -E "^\s*(Summary|Finished)" "$TMPOUT" | tail -1 || true)
+TOTAL=0; PASSED=0; FAILED=0
+if [[ -n "$SUMMARY" ]]; then
+    TOTAL=$(_extract_num "$SUMMARY" "tests? run")
+    PASSED=$(_extract_num "$SUMMARY" "passed")
+    FAILED=$(_extract_num "$SUMMARY" "failed")
+fi
+rm -f "$TMPOUT"
+
+# Run IPC benchmark if it exists (#342 — requires handshake from #555/#556)
+BENCH_SCRIPT="$REPO_ROOT/tests/run-ipc-benchmark"
+BENCH_EXIT=0
+if [[ -x "$BENCH_SCRIPT" ]]; then
+    BENCH_ARGS=()
+    [[ -n "$FILTER" ]] && BENCH_ARGS+=(--filter "$FILTER")
+    set +e
+    "$BENCH_SCRIPT" "${BENCH_ARGS[@]}" >&2
+    BENCH_EXIT=$?
+    set -e
+    if [[ $BENCH_EXIT -ne 0 ]]; then
+        FAILED=$(( FAILED + 1 ))
+        TOTAL=$(( TOTAL + 1 ))
+    else
+        PASSED=$(( PASSED + 1 ))
+        TOTAL=$(( TOTAL + 1 ))
+    fi
+fi
+
+END_MS=$(date +%s%3N)
+DURATION_MS=$((END_MS - START_MS))
+
+EXIT_CODE=$(( LAYER3_EXIT != 0 || BENCH_EXIT != 0 ? 1 : 0 ))
+
+printf '{"suite":"ipc-integration","total":%d,"passed":%d,"failed":%d,"duration_ms":%d}\n' \
+    "$TOTAL" "$PASSED" "$FAILED" "$DURATION_MS"
+exit $EXIT_CODE
diff --git a/tests/run-ipc-protocol b/tests/run-ipc-protocol
new file mode 100755
index 000000000..166a05a53
--- /dev/null
+++ b/tests/run-ipc-protocol
@@ -0,0 +1,50 @@
+#!/usr/bin/env bash
+# tests/run-ipc-protocol: Layer 2 mock IPC protocol tests (D-030)
+# Runs LocalBridge Unix-socket round-trip tests (no real subprocess).
+# Exit: 0 = all pass, non-zero = failure
+# Stdout: {"suite":"ipc-protocol","total":N,"passed":N,"failed":N,"duration_ms":N}
+set -euo pipefail
+
+FILTER=""
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --filter) FILTER="${2:-}"; shift 2 ;;
+        --filter=*) FILTER="${1#--filter=}"; shift ;;
+        *) echo "Unknown argument: $1" >&2; exit 2 ;;
+    esac
+done
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "$REPO_ROOT/server"
+
+START_MS=$(date +%s%3N)
+TMPOUT=$(mktemp)
+
+NEXTEST_ARGS=(nextest run --color never --test bridge_ipc)
+[[ -n "$FILTER" ]] && NEXTEST_ARGS+=(-E "test(~${FILTER})")
+
+set +e
+cargo "${NEXTEST_ARGS[@]}" 2>&1 | tee "$TMPOUT" >&2
+EXIT_CODE=${PIPESTATUS[0]}
+set -e
+
+END_MS=$(date +%s%3N)
+DURATION_MS=$((END_MS - START_MS))
+
+_extract_num() {
+    local haystack="$1" pattern="$2"
+    echo "$haystack" | grep -oE "[0-9]+ $pattern" | grep -oE '^[0-9]+' || echo 0
+}
+
+SUMMARY=$(grep -E "^\s*(Summary|Finished)" "$TMPOUT" | tail -1 || true)
+TOTAL=0; PASSED=0; FAILED=0
+if [[ -n "$SUMMARY" ]]; then
+    TOTAL=$(_extract_num "$SUMMARY" "tests? run")
+    PASSED=$(_extract_num "$SUMMARY" "passed")
+    FAILED=$(_extract_num "$SUMMARY" "failed")
+fi
+
+rm -f "$TMPOUT"
+printf '{"suite":"ipc-protocol","total":%d,"passed":%d,"failed":%d,"duration_ms":%d}\n' \
+    "${TOTAL:-0}" "${PASSED:-0}" "${FAILED:-0}" "$DURATION_MS"
+exit $EXIT_CODE
diff --git a/tests/run-rust b/tests/run-rust
new file mode 100755
index 000000000..453a00b1b
--- /dev/null
+++ b/tests/run-rust
@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+# tests/run-rust: Run Rust test suite via cargo nextest (D-030)
+# Exit: 0 = all pass, non-zero = failure
+# Stdout: {"suite":"rust","total":N,"passed":N,"failed":N,"duration_ms":N}
+set -euo pipefail
+
+FILTER=""
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --filter) FILTER="${2:-}"; shift 2 ;;
+        --filter=*) FILTER="${1#--filter=}"; shift ;;
+        *) echo "Unknown argument: $1" >&2; exit 2 ;;
+    esac
+done
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "$REPO_ROOT/server"
+
+START_MS=$(date +%s%3N)
+TMPOUT=$(mktemp)
+
+NEXTEST_ARGS=(nextest run --color never)
+if [[ -n "$FILTER" ]]; then
+    NEXTEST_ARGS+=(-E "test(~${FILTER})")
+fi
+
+set +e
+cargo "${NEXTEST_ARGS[@]}" 2>&1 | tee "$TMPOUT" >&2
+EXIT_CODE=${PIPESTATUS[0]}
+set -e
+
+END_MS=$(date +%s%3N)
+DURATION_MS=$((END_MS - START_MS))
+
+# Parse nextest summary: "    Summary [  0.123s] N tests run: X passed[, Y failed], Z skipped"
+# (older nextest uses "Finished", newer uses "Summary" — match both)
+SUMMARY=$(grep -E "^\s*(Summary|Finished)" "$TMPOUT" | tail -1 || true)
+
+_extract_num() {
+    local haystack="$1" pattern="$2"
+    echo "$haystack" | grep -oE "[0-9]+ $pattern" | grep -oE '^[0-9]+' || echo 0
+}
+
+TOTAL=0; PASSED=0; FAILED=0
+if [[ -n "$SUMMARY" ]]; then
+    TOTAL=$(_extract_num "$SUMMARY" "tests? run")
+    PASSED=$(_extract_num "$SUMMARY" "passed")
+    FAILED=$(_extract_num "$SUMMARY" "failed")
+fi
+
+rm -f "$TMPOUT"
+printf '{"suite":"rust","total":%d,"passed":%d,"failed":%d,"duration_ms":%d}\n' \
+    "${TOTAL:-0}" "${PASSED:-0}" "${FAILED:-0}" "$DURATION_MS"
+exit $EXIT_CODE