Constant MAX_RECYCLE_BYTES 

const MAX_RECYCLE_BYTES: usize = _; // 4_194_304usize

Don’t park a buffer larger than this in the free-list. A transiently oversize merge buffer (post-explosion, past the natural ship threshold) held resident would compete with the pager’s budget; drop it and let a fresh default regrow. 2 × the natural ship word count (≈ 4 MiB serialized) keeps normal ship-sized chunks while excluding pathological ones.