diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 5edd7c8..8fc3573 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -64,12 +64,13 @@ target_link_libraries(message_fragment_store PUBLIC
 
 ########################################
 
-add_executable(convert_frag_to_obj
+add_executable(convert_message_object_store
 	fragment_store/convert_frag_to_obj.cpp
 )
 
-target_link_libraries(convert_frag_to_obj PUBLIC
+target_link_libraries(convert_message_object_store PUBLIC
 	fragment_store
+	message_fragment_store
 )
 
 ########################################
diff --git a/src/fragment_store/convert_frag_to_obj.cpp b/src/fragment_store/convert_frag_to_obj.cpp
index eccc9e9..41a69bd 100644
--- a/src/fragment_store/convert_frag_to_obj.cpp
+++ b/src/fragment_store/convert_frag_to_obj.cpp
@@ -2,6 +2,7 @@
 #include "./backends/filesystem_storage.hpp"
 #include "./meta_components.hpp"
 #include "./serializer_json.hpp"
+#include "./message_fragment_store.hpp"
 
 #include <solanaceae/util/utils.hpp>
 
@@ -31,6 +32,13 @@ int main(int argc, const char** argv) {
 	backend::FilesystemStorage fsb_src(os_src, argv[1]);
 	backend::FilesystemStorage fsb_dst(os_dst, argv[2]);
 
+	Contact3Registry cr; // dummy
+	RegistryMessageModel rmm(cr); // dummy
+	// they only exist for the serializers (for now)
+	// TODO: version
+	MessageFragmentStore mfs_src(cr, rmm, os_src, fsb_src);
+	MessageFragmentStore mfs_dst(cr, rmm, os_dst, fsb_dst);
+
 	// add message fragment store too (adds meta?)
 
 	// hookup events
diff --git a/src/fragment_store/message_fragment_store.cpp b/src/fragment_store/message_fragment_store.cpp
index c44b511..85f47b4 100644
--- a/src/fragment_store/message_fragment_store.cpp
+++ b/src/fragment_store/message_fragment_store.cpp
@@ -71,6 +71,7 @@ namespace Message::Components {
 } // Message::Components
 
 namespace ObjectStore::Components {
+	NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(MessagesVersion, v)
 	NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(MessagesTSRange, begin, end)
 	NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(MessagesContact, id)
 
@@ -228,6 +229,7 @@ void MessageFragmentStore::handleMessage(const Message3Handle& m) {
 
 			fh.emplace_or_replace<ObjComp::Ephemeral::MetaCompressionType>().comp = Compression::ZSTD;
 			fh.emplace_or_replace<ObjComp::DataCompressionType>().comp = Compression::ZSTD;
+			fh.emplace_or_replace<ObjComp::MessagesVersion>(); // default is current
 
 			auto& new_ts_range = fh.emplace_or_replace<ObjComp::MessagesTSRange>();
 			new_ts_range.begin = msg_ts;
@@ -464,7 +466,11 @@ bool MessageFragmentStore::syncFragToStorage(ObjectHandle fh, Message3Registry&
 				continue;
 			}
 
-			s_cb_it->second(_sc, {reg, m}, j_entry[storage.type().name()]);
+			try {
+				s_cb_it->second(_sc, {reg, m}, j_entry[storage.type().name()]);
+			} catch (...) {
+				std::cerr << "MFS error: failed to serialize " << storage.type().name() << "(" << type_id << ")\n";
+			}
 		}
 	}
 
@@ -502,12 +508,14 @@ MessageFragmentStore::MessageFragmentStore(
 	_rmm.subscribe(this, RegistryMessageModel_Event::message_destroy);
 
 	auto& sjc = _os.registry().ctx().get<SerializerJsonCallbacks<Object>>();
+	sjc.registerSerializer<ObjComp::MessagesVersion>();
+	sjc.registerDeSerializer<ObjComp::MessagesVersion>();
 	sjc.registerSerializer<ObjComp::MessagesTSRange>();
 	sjc.registerDeSerializer<ObjComp::MessagesTSRange>();
 	sjc.registerSerializer<ObjComp::MessagesContact>();
 	sjc.registerDeSerializer<ObjComp::MessagesContact>();
 
-	// old
+	// old frag names
 	sjc.registerSerializer<FragComp::MessagesTSRange>(sjc.component_get_json<ObjComp::MessagesTSRange>);
 	sjc.registerDeSerializer<FragComp::MessagesTSRange>(sjc.component_emplace_or_replace_json<ObjComp::MessagesTSRange>);
 	sjc.registerSerializer<FragComp::MessagesContact>(sjc.component_get_json<ObjComp::MessagesContact>);
@@ -625,6 +633,15 @@ float MessageFragmentStore::tick(float) {
 			return 0.05f;
 		}
 
+		if (!fh.all_of<ObjComp::MessagesVersion>()) {
+			// missing version, adding
+			fh.emplace<ObjComp::MessagesVersion>();
+		}
+		if (fh.get<ObjComp::MessagesVersion>().v != 1) {
+			std::cerr << "MFS: object with version mismatch\n";
+			return 0.05f;
+		}
+
 		// get ts range of frag and collide with all curser(s/ranges)
 		const auto& frag_range = fh.get<ObjComp::MessagesTSRange>();
 
@@ -837,6 +854,11 @@ bool MessageFragmentStore::onEvent(const ObjectStore::Events::ObjectConstruct& e
 	if (!e.e.all_of<ObjComp::MessagesTSRange, ObjComp::MessagesContact>()) {
 		return false; // not for us
 	}
+	if (!e.e.all_of<ObjComp::MessagesVersion>()) {
+		// missing version, adding
+		// version check is later
+		e.e.emplace<ObjComp::MessagesVersion>();
+	}
 
 	// TODO: are we sure it is a *new* fragment?
 
diff --git a/src/fragment_store/message_fragment_store.hpp b/src/fragment_store/message_fragment_store.hpp
index 91f355d..b23d054 100644
--- a/src/fragment_store/message_fragment_store.hpp
+++ b/src/fragment_store/message_fragment_store.hpp
@@ -55,6 +55,12 @@ namespace Message::Components {
 } // Message::Components
 
 namespace ObjectStore::Components {
+	struct MessagesVersion {
+		// messages Object version
+		// 1 -> text_json
+		uint16_t v {1};
+	};
+
 	struct MessagesTSRange {
 		// timestamp range within the fragment
 		uint64_t begin {0}; // newer msg -> higher number