Constant AGDX_KV_CAS_CODE 

pub const AGDX_KV_CAS_CODE: u32 = _; // 1_000_306u32

Managed command code: compare-and-swap a key (optimistic concurrency). Additive over KV_OP_VERSION 1: a backend or server that does not serve it rejects the code, which the client surfaces as an unsupported error. Whether it is served is advertised by the kv_cas capability flag.