diff --git a/buildings/GasBurnerBuildingDefinition.tres b/buildings/GasBurnerBuildingDefinition.tres
index 6cf34ef..59589aa 100644
--- a/buildings/GasBurnerBuildingDefinition.tres
+++ b/buildings/GasBurnerBuildingDefinition.tres
@@ -21,7 +21,10 @@ definition_id = "gas_burner"
 display_name = "Gas Burner"
 description = "Burns gas into energy at its own site. Hub transporters keep it stocked with gas and collect the energy it makes."
 cost = 40
-build_resource_costs = {"ore": 40, "gas": 22}
+build_resource_costs = {
+"gas": 22,
+"ore": 40
+}
 action_icon = 33
 menu_icon = 33
 visual_scene = ExtResource("2")
diff --git a/tests/test_definitions_intact.gd b/tests/test_definitions_intact.gd
new file mode 100644
index 0000000..9adf52f
--- /dev/null
+++ b/tests/test_definitions_intact.gd
@@ -0,0 +1,130 @@
+extends SceneTree
+
+# Headless test: run with
+#   godot --headless -s res://tests/test_definitions_intact.gd
+#
+# A guard against a failure mode that has now cost this project twice, and
+# both times silently.
+#
+# Opening the project in the Godot editor re-saves .tres files, and its
+# writer DROPS properties it considers default-valued. An empty-looking
+# PackedStringArray is the usual casualty: GasBurnerBuildingDefinition lost
+# `capabilities` and `collected_outputs` once (which took the gas burner's
+# whole conversion with it), and InterceptorVesselDefinition later lost
+# `capabilities`, `hull_points`, `build_time`, `icon` and `glow_color` -
+# which cost the starting vessel its cargo hold, so nothing could be mined.
+#
+# Neither showed up as an error. The resource still loaded; it was just
+# quietly less than it had been, and the failure surfaced somewhere else
+# entirely - a full suite reporting ten unrelated tests broken.
+#
+# So this asserts the SHAPE of the catalog rather than any one field: every
+# definition must carry the things that make it what it is, and a capability
+# a definition claims must have a component behind it. Anything the editor
+# eats fails here first, next to the thing that was eaten.
+#
+# Covers:
+#   A. every vessel is whole - name, cost, icon, hull, and stats
+#   B. a vessel with cargo declares it and has a capacity to go with it
+#   C. every building is whole, and its menu wiring is complete
+#   D. a converter building keeps the fields its conversion needs
+#   E. no definition has lost its component list
+
+var failures: Array = []
+
+
+func _fail(message: String) -> String:
+	failures.append(message)
+	return message
+
+
+# get() answers null for a property a definition's script never declared,
+# and null has no is_empty(). These keep a missing field from looking like
+# an empty one - and from taking the rest of the sweep down with it.
+func _text(definition: Resource, field: String) -> String:
+	var value: Variant = definition.get(field)
+	return "" if value == null else str(value)
+
+
+func _list(definition: Resource, field: String) -> Array:
+	var value: Variant = definition.get(field)
+	if value == null:
+		return []
+	return Array(value.keys() if value is Dictionary else value)
+
+
+func _check_vessels() -> void:
+	for definition in VesselDefinitions.all():
+		var id: String = String(definition.definition_id)
+		# --- A. whole ---------------------------------------------------
+		if String(definition.display_name).strip_edges() == "":
+			_fail("vessel %s has no display name" % id)
+		if definition.base_stats.is_empty():
+			_fail("vessel %s has no stats at all" % id)
+		# Only the hulls that actually join the fleet: a repair drone is a
+		# logistics unit driven by GameState, with nothing bolted to it.
+		if definition.fleet_eligible and definition.component_scenes.is_empty():
+			_fail("vessel %s flies in the fleet with no components - an empty hull" % id)
+		if definition.hull_points.is_empty():
+			_fail("vessel %s has no hull points - it would draw as the fallback triangle" % id)
+		# --- B. cargo --------------------------------------------------
+		var carries: bool = float(definition.base_stats.get("cargo_capacity", 0.0)) > 0.0
+		var claims: bool = "cargo" in definition.capabilities
+		if carries != claims:
+			_fail("vessel %s: cargo_capacity %s but capabilities %s - a hold nothing can fill, or the reverse" \
+				% [id, definition.base_stats.get("cargo_capacity", 0.0), definition.capabilities])
+		if "weapon" in definition.capabilities \
+				and float(definition.base_stats.get("fire_range", 0.0)) <= 0.0:
+			_fail("vessel %s claims a weapon and has no range" % id)
+
+
+func _check_buildings() -> void:
+	for definition in BuildingDefinitions.all():
+		var id: String = String(definition.definition_id)
+		# --- C. whole --------------------------------------------------
+		if String(definition.display_name).strip_edges() == "":
+			_fail("building %s has no display name" % id)
+		if String(definition.description).strip_edges() == "":
+			_fail("building %s has no description - its info popup would be blank" % id)
+		if int(definition.cost) <= 0:
+			_fail("building %s is free" % id)
+		if int(definition.max_hp) <= 0:
+			_fail("building %s has no hit points" % id)
+		# Space-placed structures only: an extractor is a marker on a planet
+		# rather than a thing standing in the world, and has no scene.
+		if definition.placement_mode == "space" and definition.visual_scene == null:
+			_fail("building %s stands in space with nothing to draw" % id)
+		for field in ["menu_button_name", "menu_label_name", "menu_cost_name"]:
+			if str(definition.get(field)).strip_edges() == "":
+				_fail("building %s has no %s - the build menu could not place it" % [id, field])
+		if definition.capabilities.is_empty():
+			_fail("building %s declares no capabilities - it would do nothing at all" % id)
+		# --- D. converters ---------------------------------------------
+		# These live on the LOGISTICS profile, a sub-resource of the
+		# definition, not on the definition itself. Asking the definition
+		# for them answers null and the whole check quietly never fires -
+		# which is how the first draft of this test passed while the gas
+		# burner sat there with its collected_outputs missing.
+		var logistics: Resource = definition.logistics
+		if logistics != null and _text(logistics, "conversion_input") != "":
+			if _text(logistics, "conversion_output") == "":
+				_fail("building %s converts something into nothing" % id)
+			if _list(logistics, "collected_outputs").is_empty():
+				_fail("building %s converts but lists no collected outputs - what it makes would never be fetched" % id)
+			if _list(logistics, "input_buffers").is_empty():
+				_fail("building %s converts with no input buffer" % id)
+
+
+func _initialize() -> void:
+	_check_vessels()
+	_check_buildings()
+	if not failures.is_empty():
+		for message in failures:
+			print("  - %s" % message)
+		print("TEST_DEFINITIONS_INTACT: FAIL (%d definition(s) came back incomplete)" % failures.size())
+		quit(1)
+		return
+	print("%d vessels and %d buildings, all intact" \
+		% [VesselDefinitions.all().size(), BuildingDefinitions.all().size()])
+	print("TEST_DEFINITIONS_INTACT: PASS")
+	quit(0)
diff --git a/tests/test_definitions_intact.gd.uid b/tests/test_definitions_intact.gd.uid
new file mode 100644
index 0000000..d7ebbe4
--- /dev/null
+++ b/tests/test_definitions_intact.gd.uid
@@ -0,0 +1 @@
+uid://d3ury2lcjwer7