diff --git a/src/game/engine/src/autoloads/event_bus.gd b/src/game/engine/src/autoloads/event_bus.gd
index 2737f97e..b14ad789 100644
--- a/src/game/engine/src/autoloads/event_bus.gd
+++ b/src/game/engine/src/autoloads/event_bus.gd
@@ -289,3 +289,27 @@ signal rally_point_set(building_id: String, hex: Vector2i, command: String)
 signal building_placement_pick_requested(building_id: String, city: Variant, building_def_json: String)
 ## p1-26c: emitted once the player confirms a placement tile for a building.
 signal building_placement_confirmed(building_id: String, city: Variant, tile_pos: Vector2i)
+
+# -- Courier diplomacy signals (p3-01 c5) ------------------------------------
+## Mirrors mc-trade::CourierDispatched. Emitted by turn processor on dispatch.
+signal courier_dispatched(agreement_id: int, from_player: int, to_player: int, courier_unit: String, eta_turns: int)
+## Mirrors mc-trade::CourierIntercepted. Emitted mid-route when courier is killed.
+signal courier_intercepted(agreement_id: int, at_position: Vector2i, by_player: int)
+## Mirrors mc-trade::SharedMapDelivered. Emitted when courier reaches destination.
+signal shared_map_delivered(agreement_id: int, from_player: int, to_player: int, turns_remaining: int)
+## Mirrors mc-trade::SharedMapExpired. Emitted when the shared-map window closes.
+signal shared_map_expired(agreement_id: int)
+## Mirrors mc-trade::OpenBordersSigned. Emitted when open-borders deal is made.
+signal open_borders_signed(agreement_id: int, player_a: int, player_b: int, turns_remaining: int)
+## Mirrors mc-trade::OpenBordersExpired. Emitted when open-borders deal lapses.
+signal open_borders_expired(agreement_id: int)
+## Emitted by Diplomacy module when the human offers an OpenBorders deal.
+signal open_borders_offered(from_player: int, to_player: int, gold: int, luxury_id: String)
+## Emitted by Diplomacy module when the human offers a SharedMap deal.
+signal shared_map_offered(from_player: int, to_player: int, gold: int, luxury_id: String)
+
+# -- Audio diagnostics --------------------------------------------------------
+## Emitted by AudioManager once per key when an SFX cannot be played because
+## the manifest entry is missing or its stream fails to load. UI can wire a
+## toast off this signal; the warning is also pushed to Godot's stderr.
+signal audio_asset_missing(key: String, reason: String)