diff --git a/public/js/ar/pose.js b/public/js/ar/pose.js
index 12a2fff..b986dd4 100644
--- a/public/js/ar/pose.js
+++ b/public/js/ar/pose.js
@@ -10,6 +10,32 @@ import * as THREE from 'three';
 const _m = new THREE.Matrix4();
 const _q = new THREE.Quaternion();
 
+/* Rotation frame correction. The translation is converted from POS-IT's frame to
+ * the Three.js frame by F = diag(1,-1,-1) (the -t[1]/-t[2] negation). A rotation
+ * must be conjugated by the SAME F to stay in one consistent frame: R' = F R F^T.
+ * Applying F to translation but leaving rotation as-is (mode 'asis') puts position
+ * and orientation in different frames — position tracks but orientation tumbles
+ * (phone pitch leaks into world yaw/roll). Modes are runtime-switchable for on-device
+ * A/B: the debug overlay cycles ROT_MODES and calls setRotMode(). */
+const F = new THREE.Matrix4().set(1,0,0,0, 0,-1,0,0, 0,0,-1,0, 0,0,0,1);
+const Ft = F.clone().transpose();
+export const ROT_MODES = ['frf', 'asis', 'fr', 'rf'];
+let rotMode = 'frf';   // F R F^T — the frame-consistent default
+export function setRotMode(m) { if (ROT_MODES.includes(m)) rotMode = m; }
+export function getRotMode() { return rotMode; }
+
+function correctRotation(R) {
+  // R is a Matrix4 holding the raw POS-IT rotation.
+  switch (rotMode) {
+    case 'asis': return R;
+    case 'fr':   return _m2.multiplyMatrices(F, R);
+    case 'rf':   return _m2.multiplyMatrices(R, F);
+    case 'frf':
+    default:     return _m2.multiplyMatrices(F, R).multiply(Ft);
+  }
+}
+const _m2 = new THREE.Matrix4();
+
 /* Input convention (matches the v1-validated fix): raw centered image coords are
  * passed to POS-IT — NO Y pre-flip. The -t[1]/-t[2] negation below is what converts
  * to the Three.js camera frame. Pre-flipping Y here double-flips the vertical axis
@@ -59,14 +85,15 @@ export class PoseEstimator {
   }
 
   candidate(rot, t, error) {
-    // Rotation as-is (row-major 3x3 -> Matrix4)
+    // Raw POS-IT rotation (row-major 3x3 -> Matrix4)
     _m.set(
       rot[0][0], rot[0][1], rot[0][2], 0,
       rot[1][0], rot[1][1], rot[1][2], 0,
       rot[2][0], rot[2][1], rot[2][2], 0,
       0, 0, 0, 1
     );
-    const quaternion = new THREE.Quaternion().setFromRotationMatrix(_m);
+    // Conjugate into the Three.js frame so rotation matches the flipped translation
+    const quaternion = new THREE.Quaternion().setFromRotationMatrix(correctRotation(_m));
     // Translation: negate Y and Z only (confirmed fix)
     const position = new THREE.Vector3(t[0], -t[1], -t[2]);
     return { position, quaternion, error };