Enum LogTarget 

pub enum LogTarget<'a> {
    Live(&'a mut EventLog),
    Buffer(Vec<EventKind>),
}

Where the event KINDS a run produces are sent.

Live appends each kind to the shared single-writer EventLog immediately — the sequential path, byte-for-byte as before. Buffer collects them in order into a Vec and touches no log, so a run can execute concurrently with others; the engine later replays the buffer through its own single-writer emit (roadmap M3 wall-clock overlap). Transcripts are files, not the log, and are written live regardless of the target.

Variants

Live(&'a mut EventLog)

Append straight to the single-writer log (default sequential path).

Buffer(Vec<EventKind>)

Collect kinds in append order; the engine emits them later, serially.