SkinLibrary

Fix release — /skin did not work correctly on any Minecraft version other than the one the mod was compiled against.

Fixed

• /skin crashed the server on 1.21.9 and 1.21.10. The mod called ServerPlayer.getServer(), which those releases no longer have. The NoSuchMethodError landed in the server tick loop, so the whole server went down, not just the command.
• /skin failed on 1.21 through 1.21.8. Messages went out via ServerPlayer.sendSystemMessage, which only appeared in 1.21.9.
• /skin reset failed on 1.21.9+. The player name came from GameProfile.getName(), but in newer authlib GameProfile is a record with name().

All three had the same root cause: one jar for the whole version range reaching for API that part of that range does not have. Commands now use only CommandSourceStack — the one API with the same shape across 1.21 – 1.21.10.

Changed

• Supported range is now 1.21 – 1.21.10. 1.21.11 is out: it no longer has CommandSourceStack.hasPermission, which the requireOperator option relies on.

Added

• tools/check_api.py — checks a built jar against the mappings of every supported version and rejects it if the mod calls anything missing from any of them. It also flags casts to Minecraft types and direct authlib usage, the exact traps behind the bugs above.

Verified with a bot on test servers running 1.21.10 and 1.21.1: list, paging, library skin, random, reset, player, url and an unknown name.