diff --git a/Mods/Editor/Src/EditorServer.cpp b/Mods/Editor/Src/EditorServer.cpp
index d35c0dbb..056dbc49 100644
--- a/Mods/Editor/Src/EditorServer.cpp
+++ b/Mods/Editor/Src/EditorServer.cpp
@@ -106,8 +106,10 @@ void EditorServer::OnMessage(WebSocket* p_Socket, std::string_view p_Message) no
 
 	std::optional<int64_t> s_MessageId;
 
-	if (s_JsonMsg["msgId"].type() == simdjson::ondemand::json_type::number) {
-		s_MessageId = s_JsonMsg["msgId"];
+	if (s_JsonMsg.find_field("msgId").error() == simdjson::SUCCESS) {
+		if (s_JsonMsg["msgId"].type() == simdjson::ondemand::json_type::number) {
+			s_MessageId = s_JsonMsg["msgId"];
+		}
 	}
 
 	if (s_Type == "hello") {
@@ -551,6 +553,7 @@ void EditorServer::SendEntityList(EditorServer::WebSocket* p_Socket, std::shared
 
 		s_EventStream << "{";
 		s_EventStream << write_json("id") << ":" << write_json(std::format("{:016x}", s_Node->EntityId)) << ",";
+		s_EventStream << write_json("source") << ":" << write_json("game") << ",";
 		s_EventStream << write_json("tblu") << ":" << write_json(std::format("{:016X}", s_Node->TBLU.GetID())) << ",";
 		s_EventStream << write_json("type") << ":" << write_json((*s_Node->Entity->GetType()->m_pInterfaces)[0].m_pTypeId->typeInfo()->m_pTypeName);
 
@@ -625,11 +628,13 @@ void EditorServer::WriteEntityDetails(std::ostream& p_Stream, ZEntityRef p_Entit
 			p_Stream << write_json("name") << ":" << write_json(s_Name) << ",";
 		}
 
+		p_Stream << write_json("source") << ":" << write_json("game") << ",";
+
 		p_Stream << write_json("tblu") << ":" << write_json(std::format("{:016X}", s_Factory->m_ridResource.GetID())) << ",";
 	}
 	else {
 		// TODO: Name.
-		p_Stream << write_json("byEditor") << ":" << write_json(true) << ",";
+		p_Stream << write_json("source") << ":" << write_json("editor") << ",";
 	}
 
 	// Write type and interfaces.
@@ -842,12 +847,6 @@ EntitySelector EditorServer::ReadEntitySelector(simdjson::ondemand::value p_Sele
 		};
 	}
 
-	const bool s_ByEditor = p_Selector["byEditor"];
-
-	if (!s_ByEditor) {
-		throw std::runtime_error("Entity selector 'byEditor' field cannot be `false` when 'tblu' is not present.");
-	}
-
 	return {
 		.EntityId = s_Id64,
 		.TbluHash = std::nullopt,
diff --git a/Mods/Editor/editor.d.ts b/Mods/Editor/editor.d.ts
index 7f2e5efe..808a2f03 100644
--- a/Mods/Editor/editor.d.ts
+++ b/Mods/Editor/editor.d.ts
@@ -53,19 +53,20 @@ interface PropertyValue {
 
 interface GameEntity {
 	id: EntityId;
+	source: "game";
 	tblu: ResourceId;
 }
 
 interface EditorEntity {
 	id: EntityId;
-	byEditor: true;
+	source: "editor";
 }
 
 // Rules used to select either an entity spawned by the game or by the editor.
-// When `tblu` is defined and set to a blueprint (TBLU) resource id / hash,
+// When `source` is set to "game" and `tblu` is defined and set to a blueprint (TBLU) resource id / hash,
 // the entity will be looked up based on the provided `id` in the collection of entities
 // spawned by the game based on that blueprint.
-// Otherwise, when `byEditor` is defined and set to `true`, the entity will be looked up
+// Otherwise, the entity will be looked up
 // in the collection of entities spawned by the editor at runtime.
 type EntitySelector = GameEntity | EditorEntity;