Stem length under a beam is determined by the beam's slant, not the note's own standard/extended length

Within a beamed group, individual stem lengths vary along the beam's slope so every stem meets the (single, straight) beam line — the group's overall stem length is set by the extreme note (closest to or furthest from the beam), and every other note's stem is stretched or compressed to reach the same beam, not drawn to its own independent standard length.

A beamed passage where interior notes' stems visibly stop short of or cross through the beam line, rather than terminating exactly at it — most likely a Formatter/Beam interaction bug rather than an authoring error, since stem length under a beam is entirely computed by `Beam`'s own geometry pass.

Gould, Behind Bars, Beams chapter (beam slant and stem-length coupling); Ross, ch. on beaming, same — both treat this as inseparable from the beam-direction-uniformity rule (see `beam-group-uniform-stem-direction`).

This rule is about where marks land on the page, so it can only be judged after engraving. Collision and spacing faults live here.