Constant DEFAULT_MAX_OUTPUT_BYTES 

pub const DEFAULT_MAX_OUTPUT_BYTES: usize = _; // 10_485_760usize

Default per-LINE stdout retention cap: 10 MB.

Bounds what a single stdout line may retain in memory — not cumulative throughput, which is streamed through and never held. A line over the cap is dropped (and surfaced as a warning event); the run continues. Override per-run via RunOptions::max_output_bytes.