diff --git a/src/transport_layer/etcp_tx_stats.c b/src/transport_layer/etcp_tx_stats.c
new file mode 100644
index 00000000..5f153f14
--- /dev/null
+++ b/src/transport_layer/etcp_tx_stats.c
@@ -0,0 +1,52 @@
+#include "etcp_tx_stats.h"
+#include "etcp.h"
+#include "pkt_normalizer.h"
+#include "../utun_instance.h"
+#include "../../lib/debug_config.h"
+
+void etcp_tx_record_ack(struct etcp_tx_history *h, uint64_t now, uint64_t bytes) {
+    if (!h) { DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "TX ACK history missing"); return; }
+    uint64_t tick = now / 100000;
+    struct etcp_ack_bucket *b = &h->buckets[tick % 11];
+    if (b->tick_plus_one != tick + 1) { b->tick_plus_one = tick + 1; b->bytes = 0; }
+    if (bytes > UINT64_MAX - b->bytes || bytes > UINT64_MAX - h->total) {
+        DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "TX ACK counter overflow bytes=%llu", (unsigned long long)bytes); return;
+    }
+    b->bytes += bytes; h->total += bytes;
+}
+
+uint64_t etcp_tx_acked_window(const struct etcp_tx_history *h, uint64_t now) {
+    if (!h) { DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "TX ACK window missing"); return 0; }
+    uint64_t end = now / 100000, start = end > 10 ? end - 10 : 0, bytes = 0;
+    for (unsigned i = 0; i < 11; i++) {
+        const struct etcp_ack_bucket *b = &h->buckets[i];
+        if (b->tick_plus_one && b->tick_plus_one - 1 >= start && b->tick_plus_one - 1 < end) bytes += b->bytes;
+    }
+    return bytes;
+}
+
+/* input_send_q уже входит в unacked_bytes. В normalizer считаем только ещё не переданный остаток. */
+uint64_t etcp_tx_queued(const struct ETCP_CONN *c) {
+    if (!c) { DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "TX queue snapshot missing connection"); return 0; }
+    uint64_t bytes = c->send_input_q ? c->send_input_q->total_bytes : 0;
+    if (c->input_queue) bytes += c->input_queue->total_bytes;
+    if (c->normalizer) {
+        const struct PKTNORM *p = c->normalizer;
+        bytes += p->data_ptr;
+        if (p->pending && p->pending->len >= p->pending_in_ptr) bytes += p->pending->len - p->pending_in_ptr;
+    }
+    return bytes;
+}
+
+int etcp_tx_get_snapshot(struct UTUN_INSTANCE *inst, uint64_t now, struct etcp_tx_snapshot *out) {
+    if (!inst || !out) { DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "TX snapshot invalid arguments"); return -1; }
+    struct etcp_tx_snapshot s = {.acked_1s = etcp_tx_acked_window(&inst->tx_history, now),
+        .window_end_us = now / 100000 * 100000};
+    /* Каждый ETCP_CONN, включая TCP-only/pending, зарегистрирован здесь ровно один раз при create. */
+    for (struct ll_entry *e = inst->connections ? inst->connections->head : NULL; e; e = e->next) {
+        struct ETCP_CONN *c = ((struct conn_queue_entry *)e->data)->conn;
+        if (!c || c->close_requested) continue;
+        s.connections++; s.queued_bytes += etcp_tx_queued(c); s.inflight_bytes += c->unacked_bytes;
+    }
+    *out = s; return 0;
+}
diff --git a/src/transport_layer/etcp_tx_stats.h b/src/transport_layer/etcp_tx_stats.h
new file mode 100644
index 00000000..26472913
--- /dev/null
+++ b/src/transport_layer/etcp_tx_stats.h
@@ -0,0 +1,21 @@
+/* Секундное окно ACK всего ядра: десять завершённых интервалов и один текущий, шаг 100ms.
+ * Владелец UTUN_INSTANCE; все операции в uasync. Reset/close отдельных соединений историю не меняют. */
+#ifndef ETCP_TX_STATS_H
+#define ETCP_TX_STATS_H
+#include <stdint.h>
+#ifdef __cplusplus
+extern "C" {
+#endif
+struct UTUN_INSTANCE;
+struct ETCP_CONN;
+struct etcp_ack_bucket { uint64_t tick_plus_one, bytes; };
+struct etcp_tx_history { struct etcp_ack_bucket buckets[11]; uint64_t total; };
+struct etcp_tx_snapshot { uint64_t queued_bytes, inflight_bytes, acked_1s, window_end_us; unsigned connections; };
+void etcp_tx_record_ack(struct etcp_tx_history *history, uint64_t now_us, uint64_t bytes);
+uint64_t etcp_tx_acked_window(const struct etcp_tx_history *history, uint64_t now_us);
+uint64_t etcp_tx_queued(const struct ETCP_CONN *conn);
+int etcp_tx_get_snapshot(struct UTUN_INSTANCE *inst, uint64_t now_us, struct etcp_tx_snapshot *snapshot);
+#ifdef __cplusplus
+}
+#endif
+#endif