diff --git a/src/vst/pitch_shift.cpp b/src/vst/pitch_shift.cpp
index ec95ec0..ed6cdf7 100644
--- a/src/vst/pitch_shift.cpp
+++ b/src/vst/pitch_shift.cpp
@@ -186,9 +186,12 @@ void PitchShifter::splice(std::int64_t nominalJump) {
     fadeLen_ = fadeFrames_;
     if (ratio_ > 1.0) {
         const double headroom = static_cast<double>(dLow_) - (ratio_ - 1.0) - 2.0;
-        const std::int64_t safe =
-            headroom > 0.0 ? static_cast<std::int64_t>(headroom / (ratio_ - 1.0)) : 1;
-        fadeLen_ = std::max<std::int64_t>(1, std::min(fadeFrames_, safe));
+        // Clamp in double before the int64 cast to avoid UB at pathological near-unity ratios
+        // at very high sample rates (where headroom/(ratio_-1.0) could overflow int64).
+        const double safeDbl = headroom > 0.0
+            ? std::min(headroom / (ratio_ - 1.0), static_cast<double>(fadeFrames_))
+            : 1.0;
+        fadeLen_ = std::max<std::int64_t>(1, static_cast<std::int64_t>(safeDbl));
     }
     fading_ = true;
     fadePos_ = 0;
diff --git a/tests/test_pitch_shift.cpp b/tests/test_pitch_shift.cpp
index b909bf8..73f441a 100644
--- a/tests/test_pitch_shift.cpp
+++ b/tests/test_pitch_shift.cpp
@@ -183,14 +183,21 @@ static void testRtDisciplineAndPassthrough() {
 
 // --- 5. Spectral purity: a repitched pure sine stays a SINGLE shifted tone. ---
 static void testRepitchSpectralPurity() {
-    // Frequencies are in cycles/sample (rate-free). The source tone is chosen ADVERSARIALLY:
-    // f0 * (window/2) = 5.5125 cycles, i.e. a fractional part of ~0.51 — content half a window
-    // apart in the ring is near ANTI-PHASE. The old dual-tap design (taps hard-locked w/2
-    // apart) cancelled almost completely at every crossfade midpoint for such tones — the DAW
-    // "severe beating / multiple partials from a pure sine" bug. A correct shifter keeps the
-    // output a single sinusoid at ratio*f0 with a steady amplitude.
+    // Frequencies are in cycles/sample (rate-free). The source tone is chosen ADVERSARIALLY
+    // on TWO axes simultaneously:
+    //   (a) f0*(w/2) = (2205/2)/196 = 1102/196 ≈ 5.622 cycles (frac ≈ 0.622) — content half a
+    //       window apart in the ring is near ANTI-PHASE.  The old dual-tap design cancelled
+    //       almost completely at every crossfade midpoint for such tones — the DAW "severe
+    //       beating / multiple partials from a pure sine" bug.
+    //   (b) ringLen_*f0 = 4410/196 = 22.5 EXACTLY — at ratio 4 the write head advances 4 taps
+    //       per output frame, so each splice-period the outgoing tap crosses the writer at the
+    //       HALF-period point of the source waveform (sign flip), producing a visible null when
+    //       gNew == gOld if fadeLen_ is not clamped to headroom.  With f0=0.005 this product
+    //       is 22.05 (frac ≈ 0.05), near a zero-crossing — the artifact is near-benign, so the
+    //       +24 st purity case would pass even with the clamping reverted.  f0=1/196 forces the
+    //       half-integer alignment that makes the pre-fix artifact catastrophic.
     const std::int64_t w = 2205;              // ~50 ms @ 44.1k (the product window)
-    const double f0 = 0.005;                  // source: period 200 samples
+    const double f0 = 1.0 / 196.0;           // source: period 196 samples; see adversarial note above
     const double ratios[] = {std::pow(2.0, 2.0 / 12.0),    // +2 semitones (the DAW report: D from C)
                              std::pow(2.0, -3.0 / 12.0),   // -3 semitones (down-shift path)
                              2.0,                          // octave up (nominal-fade boundary)
@@ -248,7 +255,7 @@ static void testRepitchSpectralPurity() {
         // to ~0.78 of max on the CLEAN signal alone). Smallest phase-clean choice: exactly one
         // output period per window (50..400 frames here), hop of half a window.
         const std::size_t win = static_cast<std::size_t>(std::lround(1.0 / f1));
-        const std::size_t hop = win / 2;
+        const std::size_t hop = std::max<std::size_t>(1, win / 2);
         double minRms = 1e9, maxRms = 0.0;
         for (std::size_t s0 = from; s0 + win <= n; s0 += hop) {
             double e = 0.0;