diff --git a/tests/Makefile.am b/tests/Makefile.am
index e8f60ba1..c9187e45 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -82,6 +82,7 @@ check_PROGRAMS = \
 	test_chat_join_e2e \
 	test_dm_e2e \
 	test_dm_media \
+	test_dm_worker \
 	test_call \
 	test_call_headless \
 	test_radio \
@@ -477,6 +478,10 @@ test_dm_media_SOURCES = test_dm_media.c
 test_dm_media_CFLAGS = $(test_dm_e2e_CFLAGS)
 test_dm_media_LDADD = $(LIBUTUN) $(CRYPTO_LIBS) $(COMMON_LIBS)
 
+test_dm_worker_SOURCES = test_dm_worker.c
+test_dm_worker_CFLAGS = $(test_dm_e2e_CFLAGS)
+test_dm_worker_LDADD = $(LIBUTUN) $(CRYPTO_LIBS) $(COMMON_LIBS)
+
 test_call_SOURCES = test_call.c
 test_call_CFLAGS = -I$(top_srcdir)/src -I$(top_srcdir)/src/chat -I$(top_srcdir)/src/dm -I$(top_srcdir)/src/call -I$(top_srcdir)/src/routing_layer -I$(top_srcdir)/src/transport_layer -I$(top_srcdir)/lib
 test_call_LDADD = $(LIBUTUN) $(CRYPTO_LIBS) $(COMMON_LIBS)
diff --git a/tests/test_dm_worker.c b/tests/test_dm_worker.c
new file mode 100644
index 00000000..b9c28486
--- /dev/null
+++ b/tests/test_dm_worker.c
@@ -0,0 +1,100 @@
+/* Длительное потоковое шифрование PM не мешает heartbeat uasync. */
+#include <stdio.h>
+#include <string.h>
+#include <pthread.h>
+#include <openssl/sha.h>
+
+#include "../lib/platform_compat.h"
+#include "../lib/u_async.h"
+#include "../lib/debug_config.h"
+#include "../src/dm/dm_crypto.h"
+#include "../src/media_async/media_async.h"
+
+struct worker_test {
+    struct UASYNC* ua;
+    struct media_async* ma;
+    pthread_t event_thread;
+    void* heartbeat;
+    unsigned beats, encryptions;
+    uint64_t start, last, max_gap;
+    int result, completed;
+};
+
+static void work(void* arg) {
+    struct worker_test* t = arg;
+    t->result = -1;
+    if (pthread_equal(pthread_self(), t->event_thread)) {
+        DEBUG_ERROR(DEBUG_CATEGORY_DM, "PM crypto executed in the event thread"); return;
+    }
+    FILE* source = tmpfile();
+    FILE* cipher = tmpfile();
+    FILE* plain = tmpfile();
+    if (!source || !cipher || !plain) { DEBUG_ERROR(DEBUG_CATEGORY_DM, "worker fixture file creation failed"); goto done; }
+    uint8_t data[65536], key[32] = {11}, id[16] = {23}, hash[32], expected[32], actual[32];
+    memset(data, 0xa7, sizeof(data));
+    SHA256_CTX digest;
+    SHA256_Init(&digest);
+    for (unsigned i = 0; i < 128; i++) {
+        if (fwrite(data, 1, sizeof(data), source) != sizeof(data)) goto done;
+        SHA256_Update(&digest, data, sizeof(data));
+    }
+    SHA256_Final(expected, &digest);
+    uint64_t until = get_time_tb() + 5000; /* Не менее 0,5 с реальной файловой криптографии. */
+    uint64_t size = 0;
+    do {
+        rewind(source); rewind(cipher);
+        /* Каждый новый шифротекст получает отдельный media_id. */
+        memcpy(id, &t->encryptions, sizeof(t->encryptions));
+        if (dm_media_encrypt_stream(key, 42, id, source, cipher, &size, hash)) goto done;
+        t->encryptions++;
+    } while (get_time_tb() < until);
+    rewind(cipher);
+    if (size != 8 * 1024 * 1024 || dm_media_decrypt_stream(key, 42, id, size, hash, cipher, plain)) goto done;
+    rewind(plain);
+    SHA256_Init(&digest);
+    size_t n;
+    while ((n = fread(data, 1, sizeof(data), plain))) SHA256_Update(&digest, data, n);
+    if (ferror(plain)) goto done;
+    SHA256_Final(actual, &digest);
+    t->result = memcmp(expected, actual, sizeof(actual)) ? -1 : 0;
+done:
+    if (source) fclose(source);
+    if (cipher) fclose(cipher);
+    if (plain) fclose(plain);
+    if (t->result) DEBUG_ERROR(DEBUG_CATEGORY_DM, "PM worker crypto verification failed");
+}
+
+static void done(void* arg, int error) {
+    struct worker_test* t = arg;
+    if (error || !pthread_equal(pthread_self(), t->event_thread)) t->result = -1;
+    t->completed = 1;
+    uasync_stop(t->ua);
+}
+
+static void heartbeat(void* arg) {
+    struct worker_test* t = arg;
+    t->heartbeat = NULL;
+    uint64_t now = get_time_tb(), gap = now - t->last;
+    if (gap > t->max_gap) t->max_gap = gap;
+    t->last = now; t->beats++;
+    if (now - t->start > 100000) { DEBUG_ERROR(DEBUG_CATEGORY_DM, "PM worker timeout"); uasync_stop(t->ua); return; }
+    t->heartbeat = uasync_set_timeout(t->ua, 100, t, heartbeat, "pm_worker_heartbeat");
+    if (!t->heartbeat) { DEBUG_ERROR(DEBUG_CATEGORY_DM, "heartbeat allocation failed"); uasync_stop(t->ua); }
+}
+
+int main(void) {
+    debug_config_init(); debug_set_level(DEBUG_LEVEL_ERROR);
+    struct worker_test t = {0};
+    t.event_thread = pthread_self(); t.ua = uasync_create(); t.ma = media_async_create();
+    if (!t.ua || !t.ma) return 1;
+    t.start = t.last = get_time_tb();
+    t.heartbeat = uasync_set_timeout(t.ua, 100, &t, heartbeat, "pm_worker_heartbeat");
+    media_async_submit(t.ma, t.ua, work, &t, done, &t);
+    if (!t.completed) uasync_mainloop(t.ua);
+    if (t.heartbeat) uasync_cancel_timeout(t.ua, t.heartbeat);
+    int ok = t.completed && !t.result && t.beats >= 10;
+    media_async_destroy(t.ma); uasync_destroy(t.ua, 0);
+    printf("test_dm_worker: 8MiB encrypt/decrypt, runs=%u heartbeat=%u max_gap=%.1fms %s\n",
+           t.encryptions, t.beats, t.max_gap / 10.0, ok ? "PASS" : "FAIL");
+    return !ok;
+}