Constant INSTANCED_VERSION 

pub const INSTANCED_VERSION: u32 = 2;

Instanced format version this encoder writes for a record that CARRIES trailing field 1 (item_id). Decoders accept v1 and any version at or above 2 that declares a valid stride, so this bumps only when a trailing field is APPENDED — never to gate a read. Keep in lockstep with the TS decoder.