diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index d43233ed..82f652a3 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -9,6 +9,7 @@ This is an UNSTABLE release. It includes many experimental features, as well as
 * HDF5: NXmx `underload_value`, the lowest valid pixel value, is now written.
 * A DECTRIS detector sending signed images is no longer declared unsigned in the image stream and in HDF5.
 * rugnux: `_process.h5` now describes the pixel format of the images it links to, instead of the container rugnux processes in.
+* HDF5: the detector tilt (`rot1`/`rot2`/`rot3`) is now exported correctly in the NXmx transformation chain; a tilted geometry was previously written so that other programs placed the detector wrongly (tens of mm at a few degrees of tilt). Untilted geometries are unaffected.
 
 ### 1.0.0-rc.161
 This is an UNSTABLE release. It includes many experimental features, as well as many AI generated fixes. We recommend using rc.152 for production use.
diff --git a/writer/HDF5NXmx.cpp b/writer/HDF5NXmx.cpp
index 0bcb9e5f..8f0261d8 100644
--- a/writer/HDF5NXmx.cpp
+++ b/writer/HDF5NXmx.cpp
@@ -336,7 +336,7 @@ std::unique_ptr<HDF5DataSet> NXmx::VDS(const StartMessage &start,
 void NXmx::Detector(const StartMessage &start) {
     HDF5Group group(*hdf5_file, "/entry/instrument/detector");
     group.NXClass("NXdetector");
-    SaveScalar(group, "depends_on", "/entry/instrument/detector/transformations/rot3");
+    SaveScalar(group, "depends_on", "/entry/instrument/detector/transformations/translation");
 
     // beam_center_x/y and the transformations chain (translation + rot1/2/3) are the refinable geometry;
     // they are written once at Finalize (see Metrology) from the values refined by the offline analysis.
@@ -611,8 +611,14 @@ void NXmx::Metrology(const StartMessage &start, const EndMessage &end) {
     double vector_length = sqrt(vector[0] * vector[0] + vector[1] * vector[1] + vector[2] * vector[2]);
     std::vector<double> vector_norm{vector[0] / vector_length, vector[1]/vector_length, vector[2]/vector_length};
 
+    // The translation hangs off rot1, not off ".", so the tilt pivots about the SAMPLE: the rotations
+    // then act on the whole sample->pixel vector including the distance, which is what
+    // DiffractionGeometry does (poni_rot * {dx, dy, distance}). With the translation at the root the
+    // panel origin stays put and only its orientation turns, displacing the origin by tens of mm at a
+    // degree of tilt.
     SaveScalar(transformations, "translation", vector_length)->
-            Transformation("m", ".", "detector", "detector_arm", "translation", vector_norm);
+            Transformation("m", "/entry/instrument/detector/transformations/rot1",
+                           "detector", "detector_arm", "translation", vector_norm);
 
     // https://manual.nexusformat.org/classes/base_classes/NXdetector_module.html?highlight=nxdetector_module
     // The order of indices (i, j or i, j, k) is slow to fast.
@@ -622,28 +628,34 @@ void NXmx::Metrology(const StartMessage &start, const EndMessage &end) {
     std::vector<int32_t> size = {static_cast<int32_t>(start.image_size_y),
                                  static_cast<int32_t>(start.image_size_x)};
 
+    // Jungfraujoch holds the tilt in the PyFAI PONI convention, poni_rot = Rz(-rot3)*Rx(-rot2)*Ry(+rot1)
+    // (DiffractionGeometry::UpdatePoniRotMatrix), written in the internal frame: x along increasing
+    // column, y along increasing row, z along the beam. NXmx uses McStas, which is that frame turned
+    // 180 degrees about x - a proper rotation, not a mirror - so rotations about y and z reverse sense
+    // while those about x keep it. Hence the axis vectors below. A depends_on chain applies the
+    // DEEPEST dependency first, so rot3 sits at the root to make the product R_rot3*R_rot2*R_rot1.
     SaveScalar(transformations, "rot1", rot1)->
-            Transformation("rad",
-                           "/entry/instrument/detector/transformations/translation",
-                           "detector", "detector_arm",
-                           "rotation",
-                           std::vector<double>{1.0, 0.0, 0.0});
-
-    SaveScalar(transformations, "rot2", rot2)->
-            Transformation("rad",
-                           "/entry/instrument/detector/transformations/rot1",
-                           "detector", "detector_arm",
-                           "rotation",
-                           std::vector<double>{0.0, -1.0, 0.0});
-
-    SaveScalar(transformations, "rot3", rot3)->
             Transformation("rad",
                            "/entry/instrument/detector/transformations/rot2",
                            "detector", "detector_arm",
                            "rotation",
+                           std::vector<double>{0.0, -1.0, 0.0});
+
+    SaveScalar(transformations, "rot2", rot2)->
+            Transformation("rad",
+                           "/entry/instrument/detector/transformations/rot3",
+                           "detector", "detector_arm",
+                           "rotation",
+                           std::vector<double>{1.0, 0.0, 0.0});
+
+    SaveScalar(transformations, "rot3", rot3)->
+            Transformation("rad",
+                           ".",
+                           "detector", "detector_arm",
+                           "rotation",
                            std::vector<double>{0.0, 0.0, -1.0});
 
-    DetectorModule("module", origin, size, {-1,0,0}, {0,-1,0}, "rot3",
+    DetectorModule("module", origin, size, {-1,0,0}, {0,-1,0}, "translation",
                    start.pixel_size_x);
 }