Constant MAX_LINE 

pub const MAX_LINE: usize = _; // 524_288usize

The ceiling on a single output line before it is truncated.

MAX_CAPTURE bounds the total kept, but a reader that accumulates until a newline can exhaust memory on one line that never ends. An agent emitting a huge tool result as one JSON object is the ordinary case; a broken or hostile one emitting an endless line is the case this exists for.