Constant PTY_COALESCE_MAX_BYTES 

pub(super) const PTY_COALESCE_MAX_BYTES: usize = _; // 262_144usize

Hard cap on how many bytes one coalesced batch accumulates before it is flushed regardless of the time window — bounds both broadcast latency and memory during a sustained, very fast burst (e.g. yes piped through a shell pane). 64x a single PTY_READ_BUF_SIZE read: generous headroom for real bursts (a build’s stdout in a 20ms window) while still bounded.