Constant MAX_BYTES 

pub const MAX_BYTES: usize = godspeed_sdk::ipc::MAX_PAYLOAD; // 4_096usize

The largest message body, in bytes: one page (CLAUDE.md 8.5).

Bigger than this is not a tuning problem, it is a protocol problem - stream it in pieces, the way crate::fs does, rather than looking for a way to raise the limit.