Constant RECORD_REPLAY_HASHES_IO_BUFFERS 

pub const RECORD_REPLAY_HASHES_IO_BUFFERS: bool = true;

Whether record/replay verification hashes syscall output buffers, and therefore whether its log comparison can see buffer CONTENT at all.

ONE CONSTANT BECAUSE TWO INDEPENDENT SWITCHES HAD TO AGREE AND SILENTLY DID NOT MATTER. Record/replay carried this decision twice: metadata.rs’s record_or_replay_config decided whether the recorder EMITS the hash, and record_start.rs’s ComparisonOptions decided whether the comparator READS it. Both were hard-coded false, neither was reachable from the command line, and nothing related them. Setting either alone achieves nothing: hash without compare is dead weight, compare without hash finds nothing. Naming the decision once makes the pair impossible to desynchronize, and makes changing it a one-line edit in a place a reader can find.