diff --git a/public/sceneViewer.html b/public/sceneViewer.html
index e74c287..9a45daa 100644
--- a/public/sceneViewer.html
+++ b/public/sceneViewer.html
@@ -858,6 +858,17 @@ function rebuild() {
     }
   }
 
+  // Debug: log model marker IDs and visibility state
+  try {
+    console.log('sceneViewer:model', {
+      tModel: document.getElementById('tModel')?.checked,
+      modelIds: Object.keys(modelPositions || {}),
+      gModelChildren: gModel.children.length
+    });
+  } catch (e) {
+    console.warn('sceneViewer: failed to log model info', e);
+  }
+
   // ── observed markers + normals + error lines ──
   const obs = {};
   if (arucoData) {
@@ -875,6 +886,17 @@ function rebuild() {
     }
   }
 
+  // Debug: log observed markers and observed-toggle
+  try {
+    console.log('sceneViewer:observations', {
+      tObserved: document.getElementById('tObserved')?.checked,
+      arucoMarkers: (arucoData?.markers?.length ?? 0),
+      obsIds: Object.keys(obs || {})
+    });
+  } catch (e) {
+    console.warn('sceneViewer: failed to log observations', e);
+  }
+
   const errors = [];
   const normalErrors = [];
   for (const [midStr, {pos: opos, nor: oNor}] of Object.entries(obs)) {