diff --git a/src/transport_layer/stcp.c b/src/transport_layer/stcp.c
index 634334ae..70c1a279 100644
--- a/src/transport_layer/stcp.c
+++ b/src/transport_layer/stcp.c
@@ -148,6 +148,26 @@ int stcp_try_send(struct stcp_conn *c, uint8_t *data, size_t len) {
     return 0;
 }
 
+// Write-error больше не закрывает conn синхронно: do_close → on_close →
+// tcp_link_close_cb → etcp_link_close освобождает ETCP_LINK, поэтому при
+// синхронном send-пути (stcp_link_send → flush → try_send) каскад уходил бы
+// в стек вызывающего (keepalive_timer_cb/etcp_tcp_send) — use-after-free.
+static void stcp_close_deferred(void *arg) {
+    struct stcp_conn *c = (struct stcp_conn *)arg;
+    if (!c) return;
+    c->close_call_soon = NULL;
+    DEBUG_DEBUG(DEBUG_CATEGORY_ETCP, "stcp write-error close deferred: err=%d state=%d sock=%d",
+                c->close_err, (int)c->state, (int)c->sock);
+    stcp_conn_do_close(c, c->close_err);
+}
+
+static void stcp_schedule_close(struct stcp_conn *c, int err) {
+    if (!c) return;
+    if (c->close_call_soon) return;          // уже запланирован — первый err остаётся
+    c->close_err = err;
+    c->close_call_soon = uasync_call_soon(c->ua, c, stcp_close_deferred);
+}
+
 void stcp_write_cb(socket_t sock, void *arg) {
     struct stcp_conn *c = (struct stcp_conn *)arg;
     if (!c->send_buf) { uasync_set_socket_write(c->ua, c->socket_id, 0); return; }
@@ -156,7 +176,7 @@ void stcp_write_cb(socket_t sock, void *arg) {
         int err = socket_get_error();
         if (err == ERR_AGAIN || err == ERR_WOULDBLOCK) return;
         DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "stcp_write_cb send failed err=%d", err);
-        if (c->on_write_error) c->on_write_error(c, err);
+        stcp_schedule_close(c, err);
         return;
     }
     c->send_offset += (size_t)sent;
@@ -169,7 +189,7 @@ void stcp_write_cb(socket_t sock, void *arg) {
 }
 
 void stcp_flush_pending(struct stcp_conn *c) {
-    if (!c) return;
+    if (!c || c->state != STCP_STATE_DATA) return;   // conn закрыт/не DATA — слать нечего
     while (!c->send_buf && c->pending_head) {
         struct pending_entry *pe = c->pending_head;
         c->pending_head = pe->next;
@@ -180,14 +200,14 @@ void stcp_flush_pending(struct stcp_conn *c) {
         if (!enc) { DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "stcp_flush_pending malloc enc failed len=%zu", pe->len); if (pe->data) u_free(pe->data); u_free(pe); continue; }
         if (stcp_frame_encrypt(c, pe->data, pe->len, enc, &enc_len)) {
             DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "stcp_flush_pending encrypt failed"); u_free(enc); if (pe->data) u_free(pe->data); u_free(pe);
-            if (c->on_write_error) c->on_write_error(c, ECANCELED);
+            stcp_schedule_close(c, ECANCELED);
             return;
         }
         if (pe->data) u_free(pe->data);
         u_free(pe);
 
         int r = stcp_try_send(c, enc, enc_len);
-        if (r < 0) { u_free(enc); if (c->on_write_error) c->on_write_error(c, ECANCELED); return; }
+        if (r < 0) { u_free(enc); stcp_schedule_close(c, ECANCELED); return; }
         if (r > 0) return;
     }
 }
@@ -321,6 +341,7 @@ void stcp_conn_do_close(struct stcp_conn *c, int err) {
     stcp_server_remove_conn(c);
 
     if (c->hs_timer) { uasync_cancel_timeout(c->ua, c->hs_timer); c->hs_timer = NULL; }
+    if (c->close_call_soon) { uasync_call_soon_cancel(c->ua, c->close_call_soon); c->close_call_soon = NULL; }
 
     DEBUG_INFO(DEBUG_CATEGORY_ETCP, "stcp_conn close is_server=%d prev_state=%d err=%d sock=%d", c->is_server, prev, err, (int)c->sock);
 
diff --git a/src/transport_layer/stcp.h b/src/transport_layer/stcp.h
index 5ec5d9bd..40ff8de0 100644
--- a/src/transport_layer/stcp.h
+++ b/src/transport_layer/stcp.h
@@ -124,7 +124,6 @@ struct stcp_conn {
 
     struct pending_entry *pending_head;
     struct pending_entry *pending_tail;
-    void (*on_write_error)(struct stcp_conn *c, int err);
 
     void (*on_ready)(struct stcp_conn *conn, void *arg);
     void *ready_arg;
@@ -134,6 +133,8 @@ struct stcp_conn {
 
     void *hs_timer;          // handshake timeout handle, NULL when not active
     void *free_on_close;     // если не NULL — uasync_call_soon для u_free(arg) при закрытии
+    void *close_call_soon;   // handle отложенного do_close при write-error; NULL = не запланирован
+    int   close_err;         // сохранённый err для отложенного close
 
     // recv state machine (stcp_recv_try)
     size_t  recv_need;       // expected next chunk size (0 = disabled)
diff --git a/src/transport_layer/stcp_client.c b/src/transport_layer/stcp_client.c
index bc2e9a59..16e02f15 100644
--- a/src/transport_layer/stcp_client.c
+++ b/src/transport_layer/stcp_client.c
@@ -274,7 +274,6 @@ struct stcp_client *stcp_client_connect(struct UASYNC *ua, const char *addr, uin
     c->ua = ua; c->state = STCP_STATE_INIT; c->is_server = 0; c->my_keys = *keys;
     c->on_ready = ready_cb; c->ready_arg = arg;
     c->on_close = close_cb; c->close_arg = close_arg;
-    c->on_write_error = stcp_conn_do_close;
     c->tx_cb = stcp_tx_queue_cb;
     c->got_initial_pkt = got_initial_pkt;
     c->etcp_conn = etcp_conn;
diff --git a/src/transport_layer/stcp_server.c b/src/transport_layer/stcp_server.c
index 13914d12..6285a3cf 100644
--- a/src/transport_layer/stcp_server.c
+++ b/src/transport_layer/stcp_server.c
@@ -299,7 +299,6 @@ static void server_accept_cb(socket_t listen_sock, void *arg) {
     c->state = STCP_STATE_HS_SERVER_WAIT;
     c->is_server = 1;
     c->allocated = 1;
-    c->on_write_error = stcp_conn_do_close;
     c->tx_cb = stcp_tx_queue_cb;
     c->my_keys = srv->my_keys;
     memcpy(c->my_ed25519_pubkey, srv->my_ed25519_pubkey, SC_PUBKEY_SIZE);