Nested tuplets (a sub-tuplet inside a larger tuplet's span) have no offset or bracket-stacking mechanism and will render as two overlapping, colliding brackets

A nested tuplet (e.g. a duplet inside a triplet, or a triplet subdividing one member of an outer quintuplet) is engraved with the outer bracket further from the noteheads and the inner bracket closer, vertically offset so the two never overlap — both remain independently legible.

Gradus's `tuplets` prop is a flat array of `{indices, num, denom}` entries with no relationship or nesting declaration. Two overlapping `tuplets[]` entries (one spanning the full outer group's indices, one spanning a sub-range) would each independently default to `location: LOCATION_TOP` (confirmed, no override exists per tuplet-bracket-and-numeral-must-follow-stem-direction) with no `y_offset` stacking logic anywhere in the render path — producing two brackets drawn at the identical vertical position, overlapping and unreadable.

Gould, Behind Bars, ch. 'Tuplets', nested-tuplet spacing; Ross, The Art of Music Engraving, agrees nested brackets must be vertically staggered, never coincident.

This rule can be decided from pitches, durations and voices — no layout required. A validator can check it before anything is drawn.