Constant HEADERS_PER_FETCH_CEILING 

pub const HEADERS_PER_FETCH_CEILING: usize = 1024;

Ceiling on the headers a fetch response may carry, for header sync and commit sync alike. The server truncates its response to its own max_headers_per_header_sync_fetch or max_headers_per_commit_sync_fetch, both validated against this at startup, so a client can reject a response past it as misbehaviour while still accepting a peer configured above its own cap. Enforced while decoding each response message, before its entries are materialised.