The coarse-path fallback now expands each 10 Hz step to five 50 Hz steps so its diagonals still yield bar anchors; fine band widths are injectable to test it. Offset pooling is clipped to the current segment, and auto anchors need audioSec > 0 unless midiSec is 0. Tests: forced fallback, wrong manual anchor, p90 bound; debug output gated behind ALIGN_DEBUG. Co-Authored-By: Claude Opus 5.5 <[email protected]>