Exercise capture conversion failure with distinct source generations

tools/chatgui/tests/test_stream_publish.cpp

@@ -731,6 +731,29 @@ private slots:
         if (initialFailure) { QVERIFY(requests.isEmpty()); QCOMPARE(hardwareOpens.load(), 0u); QCOMPARE(softwareOpens.load(), 0u); QCOMPARE(audioEncodes.load(), 0u); }
 #else
         QSKIP("Capture and encoder instrumentation unavailable");
+#endif
+    }
+    void captureConversionFailure() {
+#if defined(HAVE_STREAM_CAPTURE) && defined(TEST_NULL_AUDIO)
+        if (!qEnvironmentVariableIsSet("UTUN_TEST_SCREEN_CAPTURE")) QSKIP("Run under isolated Xvfb");
+        StreamPublishEngine engine;
+        StreamPublishConfig config; config.audio = false; config.showCursor = false;
+        config.video.width = 320; config.video.height = 180; config.video.fps = 15;
+        for (const auto& source : engine.sources()) if (source.kind == StreamVideoSource::Screen) { config.source = source; break; }
+        QVERIFY(!config.source.id.isEmpty());
+        QSignalSpy errors(&engine, &StreamPublishEngine::errorOccurred);
+        QVERIFY(engine.start(group, config));
+        auto* sink = engine.findChild<QVideoSink*>(); QVERIFY(sink);
+        // Валидная оболочка кадра, но повреждённый JPEG: ошибка image worker обязана остановить текущий source.
+        QVideoFrame frame(QVideoFrameFormat(QSize(16, 16), QVideoFrameFormat::Format_Jpeg));
+        QVERIFY(frame.isValid()); QVERIFY(frame.map(QVideoFrame::WriteOnly));
+        memset(frame.bits(0), 0, frame.mappedBytes(0)); frame.unmap();
+        sink->setVideoFrame(frame);
+        QTRY_VERIFY_WITH_TIMEOUT(!errors.isEmpty(), 3000);
+        QVERIFY(errors.front().front().toString().contains("Video frame conversion failed"));
+        QTRY_VERIFY_WITH_TIMEOUT(!engine.active(), 5000);
+#else
+        QSKIP("Capture fixture unavailable");
 #endif
     }
     void screenAndWindowCapture() {