diff --git a/lib/tcp_io.c b/lib/tcp_io.c
index beacc753..523bd47d 100644
--- a/lib/tcp_io.c
+++ b/lib/tcp_io.c
@@ -205,6 +205,7 @@ static void flush_write_buf(struct tcp_conn* tc) {
                 tc->write_buf = NULL;
                 tc->write_len = 0;
                 tc->write_offset = 0;
+                DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: flush_wbuf done fd=%d", (int)tc->sock);
                 return;
             }
             continue;
@@ -220,19 +221,20 @@ static void flush_write_buf(struct tcp_conn* tc) {
 static void write_queue_fetch_cb(struct ll_queue* q, void* arg) {
     struct tcp_conn* tc = (struct tcp_conn*)arg;
 
-    if (tc->error || tc->fin) return;
+    if (tc->error || tc->fin) { DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: wq_fetch skip fd=%d error=%d fin=%d", (int)tc->sock, tc->error, tc->fin); return; }
 
     if (tc->write_buf) {
         flush_write_buf(tc);
         if (tc->write_buf) return;         // остался остаток, ждём write_cb
     }
 
-    if (!tc->connected) return;             // ждём connect
+    if (!tc->connected) { DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: wq_fetch skip fd=%d not connected", (int)tc->sock); return; }
 
     struct ll_entry* e = queue_data_get(q);
     if (!e) {
         uasync_set_socket_write(tc->ua, tc->socket_id, 0);
         tc->write_monitor = 0;
+        DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: wq_fetch POLLOUT OFF fd=%d (queue empty)", (int)tc->sock);
         queue_resume_callback(q);
         if (tc->on_flushed) {
             void (*cb)(struct tcp_conn*, void*) = tc->on_flushed;
@@ -264,6 +266,7 @@ static void write_queue_fetch_cb(struct ll_queue* q, void* arg) {
         queue_entry_free(e);
         uasync_set_socket_write(tc->ua, tc->socket_id, 1);
         tc->write_monitor = 1;
+        DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: wq_fetch POLLOUT ON fd=%d (partial send, wbuf=%zu bytes)", (int)tc->sock, tc->write_len);
     } else if (n < 0 && (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR)) {
         tc->write_buf = memory_pool_alloc(tc->data_pool);
         if (!tc->write_buf) {
@@ -280,6 +283,7 @@ static void write_queue_fetch_cb(struct ll_queue* q, void* arg) {
         queue_entry_free(e);
         uasync_set_socket_write(tc->ua, tc->socket_id, 1);
         tc->write_monitor = 1;
+        DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: wq_fetch POLLOUT ON fd=%d (EAGAIN, wbuf=%zu bytes)", (int)tc->sock, tc->write_len);
     } else {
         tc->error = 1;
         DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_io: send error fd=%d errno=%d", (int)tc->sock, errno);
@@ -302,6 +306,7 @@ static void write_cb(socket_t sock, void* arg) {
             DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "tcp_io: connect ok fd=%d", (int)tc->sock);
         } else {
             tc->error = 1;
+            DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: write_cb connect fail fd=%d err=%d wmon=%d (POLLOUT still active)", (int)tc->sock, err, tc->write_monitor);
             DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_io: connect fail fd=%d err=%d", (int)tc->sock, err);
             if (tc->on_error) tc->on_error(tc, err ? err : -1, tc->arg);
             return;
@@ -309,7 +314,10 @@ static void write_cb(socket_t sock, void* arg) {
     }
 
     flush_write_buf(tc);
-    if (!tc->write_buf) queue_resume_callback(tc->write_queue);
+    if (!tc->write_buf) {
+        DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: write_cb flushed fd=%d wmon=%d (resume WQ cb)", (int)tc->sock, tc->write_monitor);
+        queue_resume_callback(tc->write_queue);
+    }
 }
 
 // ====================================================================
@@ -321,6 +329,7 @@ static void error_cb(socket_t sock, void* arg) {
     struct tcp_conn* tc = (struct tcp_conn*)arg;
     if (!tc || tc->sock == SOCKET_INVALID) return;
     tc->error = 1;
+    DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: error_cb fd=%d connected=%d fin=%d wmon=%d", (int)tc->sock, tc->connected, tc->fin, tc->write_monitor);
     DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_io: async error fd=%d", (int)tc->sock);
     if (tc->on_error) tc->on_error(tc, -1, tc->arg);
 }