diff --git a/src/components/Viewfinder.tsx b/src/components/Viewfinder.tsx
index 882bc68..a120473 100644
--- a/src/components/Viewfinder.tsx
+++ b/src/components/Viewfinder.tsx
@@ -374,6 +374,9 @@ export default function Viewfinder({
   // the preview flicker. All live values flow through the synchronizables.
   type SkiaCameraOnFrame = NonNullable<ComponentProps<typeof SkiaCamera>['onFrame']>;
   const toneFailLogged = useMemo(() => createSynchronizable<boolean>(false), []);
+  // DEBUG-4x3 (remove after diagnosis): log actual stream geometry at runtime.
+  const dbgCountSync = useMemo(() => createSynchronizable<number>(0), []);
+  const dbgLastSync = useMemo(() => createSynchronizable<string>(''), []);
   // Composition band fed to the frame worklet: [active, viewAspect, fx, fy,
   // fw, fh] where (fx,fy,fw,fh) is the photo-area rect (ratio band / polaroid
   // window / wall window) normalized to the view. While active the worklet
@@ -438,14 +441,23 @@ export default function Viewfinder({
         // sensor there. Equal-aspect bands (ratio 4:3 == native 3:4 sensor)
         // then show the ENTIRE sensor; narrower bands crop like the export.
         const feed = feedRectSync.getBlocking();
-        const bandActive = feed[0] > 0;
-        if (!bandActive) {
-          drawFullFrame();
-          return;
-        }
         const ftW = frameTexture.width();
         const ftH = frameTexture.height();
         const orient = frame.orientation;
+        const dbgMir = frame.isMirrored === true;
+        const dbgCount = dbgCountSync.getBlocking();
+        dbgCountSync.setBlocking(dbgCount + 1);
+        const bandActive = feed[0] > 0;
+        if (!bandActive) {
+          // DEBUG-4x3 (remove): stream ground truth, no-band branch
+          const line = `ft=${ftW}x${ftH} o=${orient} mir=${dbgMir} band=0 feed=[${feed.map((f) => f.toFixed(3)).join(',')}]`;
+          if (dbgCount % 60 === 0 || line !== dbgLastSync.getBlocking()) {
+            dbgLastSync.setBlocking(line);
+            console.warn('[camdebug] ' + line);
+          }
+          drawFullFrame();
+          return;
+        }
         const isLand = orient === 'left' || orient === 'right';
         const ow = isLand ? ftH : ftW;
         const oh = isLand ? ftW : ftH;
@@ -514,6 +526,12 @@ export default function Viewfinder({
         const dh = s * ftH;
         const dx = u0 + (rw - dw) / 2;
         const dy = v0 + (rh - dh) / 2;
+        // DEBUG-4x3 (remove): full geometry log for the band branch
+        const line = `ft=${ftW}x${ftH} o=${orient} mir=${dbgMir} band=1 feed=[${feed.map((f) => f.toFixed(3)).join(',')}] up=${ow}x${oh} ac=${ac.toFixed(4)} vis=${visX.toFixed(3)}x${visY.toFixed(3)} X0=${X0.toFixed(0)} Y0=${Y0.toFixed(0)} X1=${X1.toFixed(0)} Y1=${Y1.toFixed(0)} raw=${u0.toFixed(0)},${v0.toFixed(0)} ${rw.toFixed(0)}x${rh.toFixed(0)} s=${s.toFixed(4)} d=${dx.toFixed(0)},${dy.toFixed(0)}`;
+        if (dbgCount % 60 === 0 || line !== dbgLastSync.getBlocking()) {
+          dbgLastSync.setBlocking(line);
+          console.warn('[camdebug] ' + line);
+        }
         // Fresh paint; its default color is opaque black (Skia default), so
         // the surface fill below needs no explicit color set.
         const blackPaint = Skia.Paint();
@@ -603,6 +621,18 @@ export default function Viewfinder({
         : [0, 0, 0, 0, 0, 0]
     );
   }, [cameraPhotoRect, vw, vh, feedRectSync]);
+  // DEBUG-4x3 (remove): correlate JS view/region state with the worklet log.
+  useEffect(() => {
+    console.log(
+      '[camdebug-js] region=' + JSON.stringify(region) +
+      ' band=' + regionBand +
+      ' ratio=' + aspectRatio +
+      ' frame=' + selectedFrame +
+      ' view=' + vw + 'x' + vh +
+      ' feed=' + (cameraPhotoRect ? JSON.stringify([1, vw / vh, cameraPhotoRect.x / vw, cameraPhotoRect.y / vh, cameraPhotoRect.w / vw, cameraPhotoRect.h / vh]) : 'null')
+    );
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [region, regionBand, aspectRatio, selectedFrame, cameraPhotoRect]);
   const onLibTouchStart = (e: any) => {
     const ts = e.nativeEvent.touches;
     if (ts.length >= 2) {