diff --git a/App.tsx b/App.tsx
index 9efd735..72ef5dc 100644
--- a/App.tsx
+++ b/App.tsx
@@ -27,6 +27,9 @@ import './global.css';
 
 const SESSION_KEY = 'saved_session';
 
+// DEBUG-4x3 (remove after diagnosis): build marker — prints once at JS eval.
+console.error('[camdebug-ver] debug build console.error path');
+
 export default function App() {
   const [mode, setMode] = useState<'camera' | 'library'>('camera');
   const [recipes, setRecipes] = useState<Recipe[]>([]);
diff --git a/src/components/Viewfinder.tsx b/src/components/Viewfinder.tsx
index a120473..644a359 100644
--- a/src/components/Viewfinder.tsx
+++ b/src/components/Viewfinder.tsx
@@ -453,7 +453,7 @@ export default function Viewfinder({
           const line = `ft=${ftW}x${ftH} o=${orient} mir=${dbgMir} band=0 feed=[${feed.map((f) => f.toFixed(3)).join(',')}]`;
           if (dbgCount % 60 === 0 || line !== dbgLastSync.getBlocking()) {
             dbgLastSync.setBlocking(line);
-            console.warn('[camdebug] ' + line);
+            console.error('[camdebug] ' + line);
           }
           drawFullFrame();
           return;
@@ -530,7 +530,7 @@ export default function Viewfinder({
         const line = `ft=${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);
+          console.error('[camdebug] ' + line);
         }
         // Fresh paint; its default color is opaque black (Skia default), so
         // the surface fill below needs no explicit color set.
@@ -623,7 +623,7 @@ export default function Viewfinder({
   }, [cameraPhotoRect, vw, vh, feedRectSync]);
   // DEBUG-4x3 (remove): correlate JS view/region state with the worklet log.
   useEffect(() => {
-    console.log(
+    console.error(
       '[camdebug-js] region=' + JSON.stringify(region) +
       ' band=' + regionBand +
       ' ratio=' + aspectRatio +