diff --git a/rugnux/Rugnux.cpp b/rugnux/Rugnux.cpp
index 2b317db0c..c08a7617e 100644
--- a/rugnux/Rugnux.cpp
+++ b/rugnux/Rugnux.cpp
@@ -584,15 +584,6 @@ static void LogXDSGeometry(const DiffractionExperiment &experiment) {
 // ROTATION ONLY. Stills fire the FFT once per image across every worker and routinely run with a
 // known cell, so widening the transform there would cost the whole serial run for nothing; the
 // caller applies this inside its rotation branch.
-// The short-axis first-pass hypothesis below runs by default; RUGNUX_SHORT_AXIS_PASS=0 holds it off.
-// It is an extra pair of FFTs on a rotation run and it can only replace the standard answer when the
-// alternative both has a near-integer smaller primitive volume and ties the standard cell on the
-// validation frames, so the escape hatch is here for diagnosis rather than for routine use.
-static bool ShortAxisPassEnabled() {
-    const char *v = std::getenv("RUGNUX_SHORT_AXIS_PASS");
-    return v == nullptr || std::string(v) != "0";
-}
-
 static void RaiseFFTBoundForKnownCell(IndexingSettings &settings, const DiffractionExperiment &x) {
     const auto cell = x.GetUnitCell();
     if (!cell.has_value() || !cell->is_finite())
@@ -3088,7 +3079,7 @@ ProcessResult Rugnux::RunPipeline(RugnuxObserver *observer, bool write_output, b
             // its settings from experiment_, which never carried the RAISED max bound, so on a cell
             // longer than the default search it could only ever return a harmonic of what was asked
             // for, tie on frames the way a sub-multiple always does, and be adopted over it.
-            if (!cancelled_ && !experiment_.GetUnitCell().has_value() && ShortAxisPassEnabled()) {
+            if (!cancelled_ && !experiment_.GetUnitCell().has_value()) {
                 auto short_settings = experiment_.GetIndexingSettings();
                 short_settings.FFT_MinUnitCell_A(IndexingSettings::fft_min_unit_cell_limit_A);
                 short_settings.IndexingThreads(2);
@@ -3140,6 +3131,34 @@ ProcessResult Rugnux::RunPipeline(RugnuxObserver *observer, bool write_output, b
                         continue;
                     }
 
+                    // The premise of this pass, checked rather than asserted. The pass exists because a
+                    // lattice row shorter than the standard floor is reported at its first HARMONIC
+                    // above it, so a cell it may rightfully adopt has a reduced axis BELOW that floor -
+                    // and the floor is applied to the reduced cell, which is the one to measure. Where
+                    // the alternative has no such axis the floor cannot be what the standard pass
+                    // tripped over, and an integer volume ratio is then an ordinary axis multiple: the
+                    // question the axis-harmonic arbiter settles just above on the occupancy of the
+                    // class the multiple adds. That is intensity-class evidence about the very
+                    // reflections in dispute, where the tie below is a frame count this comment already
+                    // says a sublattice cannot lose - so where the two disagree the arbiter is right and
+                    // this block must not overrule it. Measured on the corpus: the four small-molecule
+                    // sets the pass is for all have a reduced axis under 9 A, and the two protein sets
+                    // it halved have 35 and 47 A.
+                    const auto alt_reduced = alt.lattice.ToPrimitive(alt.search_result.centering)
+                                                        .NiggliReduce().GetUnitCell();
+                    const float alt_shortest = std::min({alt_reduced.a, alt_reduced.b, alt_reduced.c});
+                    const float standard_floor = experiment_.GetIndexingSettings().GetFFT_MinUnitCell_A();
+                    if (alt_shortest >= standard_floor) {
+                        logger.Info("Short-axis pass (floor {:.0f} A), scheme '{}': a {:.0f}x sub-cell "
+                                    "(vol {:.0f} A^3), but its shortest reduced axis is {:.1f} A, above "
+                                    "the {:.1f} A floor the standard pass already searched - the floor "
+                                    "is not why that cell was missed, so this is an ordinary axis "
+                                    "multiple and not this pass's to decide; keeping the standing cell",
+                                    IndexingSettings::fft_min_unit_cell_limit_A, name, nearest, vol,
+                                    alt_shortest, standard_floor);
+                        continue;
+                    }
+
                     const int alt_score = count_indexed(*indexer, alt);
                     // A pass that indexes nothing is not tied with a pass that indexes nothing. Without
                     // this, 0 against 0 passes the tie band and the volume ratio alone decides, which is