diff --git a/tools/chatgui/src/stream_publish_engine.cpp b/tools/chatgui/src/stream_publish_engine.cpp
index 447e27ae..a33f19de 100644
--- a/tools/chatgui/src/stream_publish_engine.cpp
+++ b/tools/chatgui/src/stream_publish_engine.cpp
@@ -4,6 +4,7 @@
 #include "../transport/stream_bridge.h"
 #include "debug_config.h"
 #include <QGuiApplication>
+#include <QThread>
 #include <QScreen>
 #include <QRandomGenerator>
 #include <QTransform>
@@ -75,6 +76,7 @@ struct StreamPublishEngine::Impl {
     uint64_t audioFrames = 0;
     int channels = 2;
     uint64_t capturedFrames = 0;
+    uint64_t convertedCaptureFrames = 0;
     int64_t captureReport = 0;
     std::atomic<const char*> videoStage{"stopped"};
     std::atomic<int64_t> videoStageAt{0};
@@ -233,7 +235,7 @@ bool StreamPublishEngine::openSource(const StreamPublishConfig& config) {
 #ifdef HAVE_STREAM_CAPTURE
     uint64_t generation;
     { std::lock_guard<std::mutex> guard(m->lock); generation = ++m->sourceGeneration;
-      m->backendOrigin = m->backendAnchor = -1; m->capturedFrames = 0; m->lastImageCaptureAt = 0; }
+      m->backendOrigin = m->backendAnchor = -1; m->capturedFrames = m->convertedCaptureFrames = 0; m->lastImageCaptureAt = 0; }
     m->session = std::make_unique<QMediaCaptureSession>(); m->sink = std::make_unique<QVideoSink>(this);
     m->session->setVideoSink(m->sink.get());
     connect(m->sink.get(), &QVideoSink::videoFrameChanged, this, [this, generation](const QVideoFrame& frame) {
@@ -267,6 +269,7 @@ bool StreamPublishEngine::openSource(const StreamPublishConfig& config) {
         }
         /* QVideoFrame conversion stays on Qt's persistent multimedia callback thread.
          * Qt worker-thread storage was preventing the short-lived publisher thread from exiting on Windows. */
+        int64_t convertAt = monotonicUs();
         QImage image = frame.toImage();
         if (image.isNull()) {
             DEBUG_ERROR(DEBUG_CATEGORY_VIDEO, "desktop captured frame conversion failed generation=%llu format=%d size=%dx%d",
@@ -284,6 +287,11 @@ bool StreamPublishEngine::openSource(const StreamPublishConfig& config) {
             std::lock_guard<std::mutex> guard(m->lock);
             if (!m->running || generation != m->sourceGeneration) return;
             m->latestImage = image; m->frame = std::move(image); m->framePts = framePts; m->frameGeneration = m->generation;
+            if (!m->convertedCaptureFrames++) DEBUG_INFO(DEBUG_CATEGORY_VIDEO,
+                "desktop first image conversion complete generation=%llu size=%dx%d callback_tid=%llu gui_thread=%d convert_us=%lld",
+                (unsigned long long)generation, m->latestImage.width(), m->latestImage.height(),
+                (unsigned long long)(quintptr)QThread::currentThreadId(), QThread::currentThread() == qApp->thread(),
+                (long long)(monotonicUs() - convertAt));
         }
         m->wake.notify_all();
     }, Qt::DirectConnection);