diff --git a/src/RelayYesstr.cpp b/src/RelayYesstr.cpp
index 0c7c00f..6f8d151 100644
--- a/src/RelayYesstr.cpp
+++ b/src/RelayYesstr.cpp
@@ -39,6 +39,8 @@ void RelayServer::runYesstr(ThreadPool<MsgYesstr>::Thread &thr) {
             conns[connId].try_emplace(reqId);
             auto &s = conns[connId][reqId];
 
+            LI << "Yesstr sync. filter: '" << filterStr << "'";
+
             if (filterStr == "{}") {
                 qdb->checkout("events");
                 uint64_t nodeId = qdb->getHeadNodeId(txn);
@@ -51,8 +53,6 @@ void RelayServer::runYesstr(ThreadPool<MsgYesstr>::Thread &thr) {
                 // FIXME: The following blocks the whole thread for the query duration. Should interleave it
                 // with other requests like RelayReqWorker does.
 
-                LI << "Yesstr sync: Running filter: " << filterStr;
-
                 std::vector<uint64_t> quadEventIds;
                 auto filterGroup = NostrFilterGroup::unwrapped(tao::json::from_string(filterStr));
                 Subscription sub(1, "junkSub", filterGroup);
@@ -97,7 +97,6 @@ void RelayServer::runYesstr(ThreadPool<MsgYesstr>::Thread &thr) {
 
             qdb->withMemStore(s->m, [&]{
                 qdb->writeToMemStore = true;
-                LI << "ZZZ NODE " << qdb->getHeadNodeId(txn);
                 resps = qdb->handleSyncRequests(txn, qdb->getHeadNodeId(txn), reqs, 100'000);
             });
 
@@ -137,7 +136,11 @@ void RelayServer::runYesstr(ThreadPool<MsgYesstr>::Thread &thr) {
                 const auto *req = parseYesstrRequest(msg->yesstrMessage); // validated by ingester
                 const auto *reqSync = req->payload_as<Yesstr::RequestSync>();
 
-                states.handleRequest(txn, msg->connId, req->requestId(), sv(reqSync->filter()), sv(reqSync->reqsEncoded()));
+                try {
+                    states.handleRequest(txn, msg->connId, req->requestId(), sv(reqSync->filter()), sv(reqSync->reqsEncoded()));
+                } catch (std::exception &e) {
+                    sendNoticeError(msg->connId, std::string("yesstr failure: ") + e.what());
+                }
             } else if (auto msg = std::get_if<MsgYesstr::CloseConn>(&newMsg.msg)) {
                 states.closeConn(msg->connId);
             }
diff --git a/src/WSConnection.h b/src/WSConnection.h
index ef596a0..73ecb5e 100644
--- a/src/WSConnection.h
+++ b/src/WSConnection.h
@@ -21,7 +21,7 @@ class WSConnection {
     WSConnection(const std::string &url) : url(url) {}
 
     std::function<void()> onConnect;
-    std::function<void(std::string_view, size_t)> onMessage;
+    std::function<void(std::string_view, uWS::OpCode, size_t)> onMessage;
     std::function<void()> onTrigger;
     bool reconnect = true;
     uint64_t reconnectDelayMilliseconds = 5'000;
@@ -101,7 +101,7 @@ class WSConnection {
             if (!onMessage) return;
 
             try {
-                onMessage(std::string_view(message, length), compressedSize);
+                onMessage(std::string_view(message, length), opCode, compressedSize);
             } catch (std::exception &e) {
                 LW << "onMessage failure: " << e.what();
             }
diff --git a/src/cmd_stream.cpp b/src/cmd_stream.cpp
index eb51bdf..49f6ff1 100644
--- a/src/cmd_stream.cpp
+++ b/src/cmd_stream.cpp
@@ -42,7 +42,7 @@ void cmd_stream(const std::vector<std::string> &subArgs) {
         }
     };
 
-    ws.onMessage = [&](auto msg, size_t){
+    ws.onMessage = [&](auto msg, uWS::OpCode, size_t){
         auto origJson = tao::json::from_string(msg);
 
         if (origJson.is_array()) {
diff --git a/src/cmd_sync.cpp b/src/cmd_sync.cpp
index 5a1d92e..deb9643 100644
--- a/src/cmd_sync.cpp
+++ b/src/cmd_sync.cpp
@@ -120,8 +120,11 @@ void cmd_sync(const std::vector<std::string> &subArgs) {
     std::map<std::string, docopt::value> args = docopt::docopt(USAGE, subArgs, true, "");
 
     std::string url = args["<url>"].asString();
+
     std::string filterStr;
     if (args["--filter"]) filterStr = args["--filter"].asString();
+    else filterStr = "{}";
+
     std::string dir = args["--dir"] ? args["--dir"].asString() : "down";
     if (dir != "up" && dir != "down" && dir != "both") throw herr("invalid direction: ", dir, ". Should be one of up/down/both");
     if (dir != "down") throw herr("only down currently supported"); // FIXME
@@ -147,8 +150,16 @@ void cmd_sync(const std::vector<std::string> &subArgs) {
     if (filterStr.size()) {
         std::vector<uint64_t> quadEventIds;
 
-        std::string filterStr = args["--filter"].asString();
-        auto filterGroup = NostrFilterGroup::unwrapped(tao::json::from_string(filterStr));
+        tao::json::value filterJson;
+
+        try {
+            filterJson = tao::json::from_string(filterStr);
+        } catch (std::exception &e) {
+            LE << "Couldn't parse filter JSON: " << filterStr;
+            ::exit(1);
+        }
+
+        auto filterGroup = NostrFilterGroup::unwrapped(filterJson);
 
         Subscription sub(1, "junkSub", filterGroup);
 
@@ -196,7 +207,7 @@ void cmd_sync(const std::vector<std::string> &subArgs) {
         controller->sendRequests(txn, filterStr);
     };
 
-    ws.onMessage = [&](auto msg, size_t compressedSize){
+    ws.onMessage = [&](auto msg, uWS::OpCode opCode, size_t compressedSize){
         auto txn = env.txn_ro();
 
         if (!controller) {
@@ -204,6 +215,11 @@ void cmd_sync(const std::vector<std::string> &subArgs) {
             return;
         }
 
+        if (opCode == uWS::OpCode::TEXT) {
+            LW << "Unexpected non-yesstr message from relay: " << msg;
+            return;
+        }
+
         LI << "RECV size=" << msg.size() << " compressed=" << compressedSize;
         controller->handleResponses(txn, msg);
 
@@ -211,6 +227,7 @@ void cmd_sync(const std::vector<std::string> &subArgs) {
             LI << "Syncing done, writing/sending events";
             controller->finish(txn,
                 [&](std::string_view newLeaf){
+                    // FIXME: relay could crash client here by sending invalid JSON
                     writer.inbox.push_move(tao::json::from_string(std::string(newLeaf)));
                 },
                 [&](std::string_view){