diff --git a/tools/chatgui-android/tests/jni_utf8/EventSink.java b/tools/chatgui-android/tests/jni_utf8/EventSink.java
new file mode 100644
index 00000000..a56f6cc4
--- /dev/null
+++ b/tools/chatgui-android/tests/jni_utf8/EventSink.java
@@ -0,0 +1,13 @@
+/** Настоящий Java callback для проверки регистрации, замены и исключений доставки JNI. */
+public final class EventSink {
+    public int calls;
+    public int type;
+    public int bytes;
+    public boolean fail;
+    public void onEvent(int eventType, byte[] data) {
+        calls++;
+        type = eventType;
+        bytes = data == null ? 0 : data.length;
+        if (fail) throw new IllegalStateException("injected event callback failure");
+    }
+}
diff --git a/tools/chatgui-android/tests/jni_utf8/run.py b/tools/chatgui-android/tests/jni_utf8/run.py
index cfb65265..c3d6fef7 100644
--- a/tools/chatgui-android/tests/jni_utf8/run.py
+++ b/tools/chatgui-android/tests/jni_utf8/run.py
@@ -25,12 +25,13 @@ def main():
                 root / "src/chat", root / "src/media_async", root / "lib"]
     with tempfile.TemporaryDirectory(prefix="utun-jni-utf8-") as output:
         binary = Path(output) / "test_jni_utf8"
+        subprocess.run([str(java_home / "bin/javac"), "-d", output, str(directory / "EventSink.java")], check=True, timeout=30)
         command = shlex.split(os.environ.get("CC", "cc")) + ["-std=c99", "-D_DEFAULT_SOURCE", "-D__ANDROID__", "-DUSE_OPENSSL",
                    "-ffunction-sections", "-fdata-sections", "-Wl,--gc-sections", "-pthread", "-Wno-incompatible-pointer-types"]
         command += [f"-I{path}" for path in includes]
         command += [str(directory / "test_jni_utf8.c"), f"-L{server}", f"-Wl,-rpath,{server}", "-ljvm", "-o", str(binary)]
         subprocess.run(command, check=True, timeout=90)
-        subprocess.run([str(binary)], check=True, timeout=30)
+        subprocess.run([str(binary)], cwd=output, check=True, timeout=30)
 
 
 if __name__ == "__main__":
diff --git a/tools/chatgui-android/tests/jni_utf8/test_jni_utf8.c b/tools/chatgui-android/tests/jni_utf8/test_jni_utf8.c
index b40d7233..c56c7c98 100644
--- a/tools/chatgui-android/tests/jni_utf8/test_jni_utf8.c
+++ b/tools/chatgui-android/tests/jni_utf8/test_jni_utf8.c
@@ -34,10 +34,37 @@ int main(void) {
     CHECK(!(*env)->ThrowNew(env, exception, "preserved"));
     CHECK(!jni_utf8(env, original) && !jni_text(env, expected) && (*env)->ExceptionCheck(env));
     (*env)->ExceptionClear(env);
+    g_jvm = vm;
+    jclass sink_class = (*env)->FindClass(env, "EventSink"); CHECK(sink_class);
+    jmethodID constructor = (*env)->GetMethodID(env, sink_class, "<init>", "()V"); CHECK(constructor);
+    jobject sink = (*env)->NewObject(env, sink_class, constructor); CHECK(!(*env)->ExceptionCheck(env) && sink);
+    jfieldID calls = (*env)->GetFieldID(env, sink_class, "calls", "I"); CHECK(calls);
+    jfieldID type = (*env)->GetFieldID(env, sink_class, "type", "I"); CHECK(type);
+    jfieldID size = (*env)->GetFieldID(env, sink_class, "bytes", "I"); CHECK(size);
+    jfieldID fail = (*env)->GetFieldID(env, sink_class, "fail", "Z"); CHECK(fail);
+    Java_com_utun_chat_data_NativeLib_nativeSetEventCallback(env, NULL, sink); CHECK(!(*env)->ExceptionCheck(env));
+    const uint8_t payload[] = {1, 2, 3};
+    jni_on_event(7, payload, sizeof(payload));
+    CHECK((*env)->GetIntField(env, sink, calls) == 1 && (*env)->GetIntField(env, sink, type) == 7);
+    CHECK((*env)->GetIntField(env, sink, size) == sizeof(payload));
+    (*env)->SetBooleanField(env, sink, fail, JNI_TRUE);
+    jni_on_event(8, payload, sizeof(payload)); CHECK(!(*env)->ExceptionCheck(env));
+    (*env)->SetBooleanField(env, sink, fail, JNI_FALSE);
+    jni_on_event(9, NULL, 0); CHECK((*env)->GetIntField(env, sink, calls) == 3 && !(*env)->GetIntField(env, sink, size));
+    jobject replacement = (*env)->NewObject(env, sink_class, constructor); CHECK(!(*env)->ExceptionCheck(env) && replacement);
+    Java_com_utun_chat_data_NativeLib_nativeSetEventCallback(env, NULL, replacement); CHECK(!(*env)->ExceptionCheck(env));
+    jni_on_event(10, payload, sizeof(payload));
+    CHECK((*env)->GetIntField(env, replacement, calls) == 1 && (*env)->GetIntField(env, sink, calls) == 3);
+    CHECK(!(*env)->ThrowNew(env, exception, "preserved event exception"));
+    jni_on_event(11, payload, sizeof(payload)); CHECK((*env)->ExceptionCheck(env)); (*env)->ExceptionClear(env);
+    jni_on_event(12, NULL, 3); CHECK((*env)->GetIntField(env, replacement, calls) == 1);
+    Java_com_utun_chat_data_NativeLib_nativeSetEventCallback(env, NULL, NULL); CHECK(!(*env)->ExceptionCheck(env));
+    jni_on_event(13, NULL, 0); CHECK(!(*env)->ExceptionCheck(env));
+    (*env)->DeleteLocalRef(env, replacement); (*env)->DeleteLocalRef(env, sink); (*env)->DeleteLocalRef(env, sink_class);
     jstring empty = jni_text(env, ""); CHECK(empty && !(*env)->GetStringLength(env, empty));
     (*env)->DeleteLocalRef(env, empty); (*env)->DeleteLocalRef(env, exception);
     (*env)->DeleteLocalRef(env, embedded); (*env)->DeleteLocalRef(env, original);
     CHECK(!(*env)->ExceptionCheck(env) && (*vm)->DestroyJavaVM(vm) == JNI_OK);
-    puts("JNI UTF-8: 1024 real JVM roundtrips, allocation failure/retry, embedded NUL and pending exception PASS");
+    puts("JNI UTF-8/events: real JVM roundtrips, allocation failure/retry, NUL, callback replacement and exceptions PASS");
     return 0;
 }