Constant AGENT_LINE_BUFFER_CAP 

const AGENT_LINE_BUFFER_CAP: usize = _; // 1_048_576usize

Append data to a block’s terminal output file, publish a WPS event, Maximum size of the per-block line buffer used by the agent-event translation path. Past this, the buffer is reset (a producer that never emits a newline can’t grow it unboundedly). 1 MiB is far beyond any plausible stream-json frame size.