diff --git a/BuildController.gd b/BuildController.gd
index 6be8193..a134678 100644
--- a/BuildController.gd
+++ b/BuildController.gd
@@ -457,12 +457,14 @@ func _refresh_craft_status() -> void:
 	var queued: int = GameState.pending_orders(craft_building_id)
 	var stock: int = GameState.building_stock(craft_building_id)
 	var queue_text: String = "" if queued == 0 else "      Queued %d" % queued
-	craft_status.text = "Interceptor %d   Transporter %d      Here %d%s" % [
-		GameState.SHIP_COST, GameState.TRANSPORTER_COST, stock, queue_text
+	craft_status.text = "Interceptor %d   Transporter %d      Here %d%s      Transporters %d/%d" % [
+		GameState.SHIP_COST, GameState.TRANSPORTER_COST, stock, queue_text,
+		GameState.transporters_claimed(), GameState.transport_capacity()
 	]
 	# Nowhere to station one means the order would be refused, so say so
 	# rather than letting the button look available and do nothing.
-	craft_transporter_button.enabled = GameState.has_transport_hub()
+	craft_transporter_button.enabled = GameState.has_transport_hub() \
+		and GameState.can_station_transporter()
 	craft_transporter_button.queue_redraw()
 
 	craft_store_label.text = "Store ore here\nHold %d" % GameState.fleet_cargo
@@ -527,7 +529,12 @@ func _on_craft_transporter() -> void:
 	if craft_building_id == 0:
 		return
 	if not GameState.queue_order(craft_building_id, GameState.PRODUCT_TRANSPORTER):
-		craft_status.text = "Build a Transport Hub first - a transporter needs somewhere to be stationed"
+		# Two different refusals, and the player needs to know WHICH.
+		if not GameState.has_transport_hub():
+			craft_status.text = "Build a Transport Hub first - a transporter needs somewhere to be stationed"
+		else:
+			craft_status.text = "All %d berths are taken - build another hub, or research Freight Yards" % \
+				GameState.transport_capacity()
 		return
 	_refresh_craft_status()
 
diff --git a/GameState.gd b/GameState.gd
index 98ffa8b..8728c91 100644
--- a/GameState.gd
+++ b/GameState.gd
@@ -145,6 +145,11 @@ const SKILL_TREE: Array = [
 		"x": 0.18, "unlocks": BUILDING_TRANSPORT_HUB,
 		"desc": "Build transport hubs, which supply your other buildings with ore.",
 	},
+	{
+		"id": "freight_yards", "name": "Freight Yards", "cost": 80, "requires": "freight",
+		"x": 0.05, "hub_bonus": 1,
+		"desc": "Permanent: +1 transporter stationed at every hub, including ones already built.",
+	},
 	{
 		"id": "wing", "name": "Wing Doctrine", "cost": 30, "requires": "coordination",
 		"x": 0.82, "fleet_bonus": 1,
@@ -357,6 +362,9 @@ func queue_order(id: int, product: String = PRODUCT_SHIP) -> bool:
 		# Nowhere to station it. Refused rather than queued, so the player is
 		# told now instead of watching an order sit forever.
 		return false
+	if product == PRODUCT_TRANSPORTER and not can_station_transporter():
+		# Every berth is taken or spoken for (#20).
+		return false
 	(b.orders as Array).append(product)
 	return true
 
@@ -374,6 +382,11 @@ func _advance_production() -> void:
 			var cost: int = product_cost(product)
 			if int(b.get("stock", 0)) < cost:
 				break
+			if product == PRODUCT_TRANSPORTER and transporters.size() >= transport_capacity():
+				# A hub was demolished after this was ordered, so the berth it
+				# was going to use is gone. Hold the order rather than
+				# overfilling what is left.
+				break
 			if product == PRODUCT_TRANSPORTER and nearest_hub_to(b.position).is_empty():
 				# Every hub was demolished while this sat in the queue. Leave
 				# it queued and the stock untouched rather than producing a
@@ -548,6 +561,11 @@ func _process(delta: float) -> void:
 # "from", "to"}.
 const TRANSPORTER_SPEED: float = 340.0
 
+# How many transporters one hub can station. Raised for EVERY hub - built
+# already or not - by research, which is the same shape as max_fleet_size()
+# rather than a second mechanism doing the same job.
+const BASE_HUB_CAPACITY: int = 2
+
 const TRANSPORTER_IDLE: String = "idle"
 const TRANSPORTER_TO_MOTHERSHIP: String = "to_mothership"
 const TRANSPORTER_TO_BUILDING: String = "to_building"
@@ -556,6 +574,48 @@ const TRANSPORTER_RETURNING: String = "returning"
 var transporters: Array = []
 
 
+func hub_capacity() -> int:
+	# Per hub.
+	var n: int = BASE_HUB_CAPACITY
+	for id in unlocked:
+		n += int(skill_node(id).get("hub_bonus", 0))
+	return n
+
+
+func hub_count() -> int:
+	var n: int = 0
+	for b in buildings:
+		if b.type == BUILDING_TRANSPORT_HUB:
+			n += 1
+	return n
+
+
+func transport_capacity() -> int:
+	# Total berths: more hubs, or more capacity per hub. Either raises it,
+	# which is exactly the choice #12 asks the player to make.
+	return hub_count() * hub_capacity()
+
+
+func pending_transporter_orders() -> int:
+	var n: int = 0
+	for b in buildings:
+		for o in b.get("orders", []):
+			if o == PRODUCT_TRANSPORTER:
+				n += 1
+	return n
+
+
+func transporters_claimed() -> int:
+	# Built plus already ordered: an order in the queue has a berth reserved,
+	# or a player could queue ten of them against two berths and only find out
+	# when they refused to appear.
+	return transporters.size() + pending_transporter_orders()
+
+
+func can_station_transporter() -> bool:
+	return transporters_claimed() < transport_capacity()
+
+
 func has_transport_hub() -> bool:
 	return not nearest_hub_to(Vector2.ZERO).is_empty()
 
diff --git a/tests/test_hub_capacity.gd b/tests/test_hub_capacity.gd
new file mode 100644
index 0000000..46bae11
--- /dev/null
+++ b/tests/test_hub_capacity.gd
@@ -0,0 +1,143 @@
+extends SceneTree
+
+# Headless gameplay test: run with
+#   godot --headless -s res://tests/test_hub_capacity.gd
+# Forgejo #20 (part 7 of #12): a hub stations a limited number of
+# transporters. More hubs, or research, raise it.
+#
+# Verifies:
+#   1. capacity is per hub, so a second hub raises the total
+#   2. ordering past the cap is REFUSED, not silently swallowed - the ticket
+#      is explicit that the player has to be told
+#   3. a queued-but-unbuilt transporter still holds its berth, or ten could
+#      be ordered against two and only fail on arrival
+#   4. researching Freight Yards raises capacity for hubs ALREADY BUILT, not
+#      just ones placed afterwards
+#   5. the extra berth is immediately usable
+
+var game_state: Node
+var scene: Node
+var field: Node
+var crafter_id: int = 0
+var stage: int = 0
+var elapsed: float = 0.0
+
+const CRAFTER_AT: Vector2 = Vector2(400.0, 0.0)
+const HUB_A: Vector2 = Vector2(-500.0, 0.0)
+const HUB_B: Vector2 = Vector2(-500.0, 600.0)
+
+
+func _initialize() -> void:
+	game_state = root.get_node("GameState")
+	game_state.buildings.clear()
+	game_state.extractors.clear()
+	game_state.transporters.clear()
+	game_state.rocks = 900
+	game_state.fleet_cargo = 0
+	game_state.ships_owed = 0
+	game_state.unlocked = ["shipyards", "logistics", "freight"]
+	scene = load("res://Main.tscn").instantiate()
+	root.add_child(scene)
+	field = scene.get_node("BuildingField")
+
+
+func _fill_berths(n: int) -> void:
+	# Queue and immediately fund n transporters.
+	for i in range(n):
+		if game_state.queue_order(crafter_id, GameState.PRODUCT_TRANSPORTER):
+			game_state.deposit_to_building(crafter_id, GameState.TRANSPORTER_COST)
+
+
+func _process(delta: float) -> bool:
+	elapsed += delta
+	match stage:
+		0:
+			scene.get_node("AsteroidField").set_process(false)
+			scene.get_node("EnemySpawner").set_process(false)
+			field.place(GameState.BUILDING_MOTHERSHIP, Vector2.ZERO)
+			field.place(GameState.BUILDING_SHIP_CRAFTER, CRAFTER_AT)
+			crafter_id = int(game_state.buildings[-1].id)
+			field.place(GameState.BUILDING_TRANSPORT_HUB, HUB_A)
+			elapsed = 0.0
+			stage = 1
+			return false
+		1:
+			if elapsed < 0.3:
+				return false
+			var per_hub: int = game_state.hub_capacity()
+			if game_state.transport_capacity() != per_hub:
+				print("TEST_HUB_CAPACITY: FAIL (one hub gives %d berths, per-hub capacity is %d)" % [
+					game_state.transport_capacity(), per_hub
+				])
+				quit(1)
+				return true
+			print("1 hub -> %d berths (%d per hub)" % [game_state.transport_capacity(), per_hub])
+
+			# --- 2 + 3. fill it, then try to exceed it ------------------
+			_fill_berths(per_hub)
+			if game_state.transporters_claimed() != per_hub:
+				print("TEST_HUB_CAPACITY: FAIL (claimed %d berths after ordering %d)" % [
+					game_state.transporters_claimed(), per_hub
+				])
+				quit(1)
+				return true
+			# Still only QUEUED at this point - the berth must already count.
+			if game_state.queue_order(crafter_id, GameState.PRODUCT_TRANSPORTER):
+				print("TEST_HUB_CAPACITY: FAIL (queued a transporter past the %d-berth cap)" % per_hub)
+				quit(1)
+				return true
+			print("cap enforced at %d, including orders not yet built" % per_hub)
+
+			# --- 1. a second hub raises the total -----------------------
+			field.place(GameState.BUILDING_TRANSPORT_HUB, HUB_B)
+			elapsed = 0.0
+			stage = 2
+			return false
+		2:
+			if elapsed < 0.3:
+				return false
+			if game_state.transport_capacity() != game_state.hub_capacity() * 2:
+				print("TEST_HUB_CAPACITY: FAIL (2 hubs give %d berths, expected %d)" % [
+					game_state.transport_capacity(), game_state.hub_capacity() * 2
+				])
+				quit(1)
+				return true
+			print("2 hubs -> %d berths" % game_state.transport_capacity())
+			if not game_state.can_station_transporter():
+				print("TEST_HUB_CAPACITY: FAIL (second hub did not free a berth)")
+				quit(1)
+				return true
+
+			# Fill the second hub too, so capacity is exhausted again.
+			_fill_berths(game_state.transport_capacity() - game_state.transporters_claimed())
+			if game_state.can_station_transporter():
+				print("TEST_HUB_CAPACITY: FAIL (still room after filling every berth)")
+				quit(1)
+				return true
+
+			# --- 4. research raises it for hubs ALREADY built -----------
+			var before: int = game_state.transport_capacity()
+			game_state.unlocked.append("freight_yards")
+			var after: int = game_state.transport_capacity()
+			print("researched Freight Yards: %d -> %d berths across %d existing hubs" % [
+				before, after, game_state.hub_count()
+			])
+			if after != before + game_state.hub_count():
+				print("TEST_HUB_CAPACITY: FAIL (research gave %d berths, expected +1 per existing hub)" % (after - before))
+				quit(1)
+				return true
+
+			# --- 5. and the new berth is usable straight away -----------
+			if not game_state.can_station_transporter():
+				print("TEST_HUB_CAPACITY: FAIL (research raised the number but left no usable berth)")
+				quit(1)
+				return true
+			if not game_state.queue_order(crafter_id, GameState.PRODUCT_TRANSPORTER):
+				print("TEST_HUB_CAPACITY: FAIL (could not order into the berth research just added)")
+				quit(1)
+				return true
+			print("ordered into the newly researched berth")
+			print("TEST_HUB_CAPACITY: PASS")
+			quit(0)
+			return true
+	return false