Constant REPLY_QUEUE_DEPTH_CEILING 

pub const REPLY_QUEUE_DEPTH_CEILING: u16 = 1024; // 1_024u16

Inclusive upper bound for per-channel reply_queue_depth_max. The lower bound is 0, where 0 means “use DEFAULT_REPLY_QUEUE_DEPTH at the pacing-wrapper construction site.” A non-zero value pins the bound explicitly. Validator rejects values above this ceiling.