The session record

sessions/<finding>@<executor>.jsonl in the project: one JSON line per event — {"at": ..., "event": ..., "detail": ...} — appended as things happen, surviving the session and the engine. The desktop's Sessions tab reads it from disk; session explain walks it.

Event	Detail	Caused by
started	which session this is (session, finding, executor), the experiment, how far the library warmed the shadow
expectation	what the finding's out-of-sample trades lead the session to expect: trades, expectancy, deviation, max_drawdown, entries_per_bar, regimes, slippage_bps; or none and why	the finding
instrument	lot, tick, hours, multiplier the gate sizes against	the source
feed	{streaming, source}
feed_up, feed_down, feed_ended	the stream's state, with the reason
reconciled	at every start, flat included: adopted as (symbol, quantity, entry) for what the venue already held, cancelled, stranded; mid-session: corrected and the whole positions book. The review rebuilds its book from these, so an empty adopted closes any lot the record still held	a start, or a Reconcile
bar	at, close, how many signals it produced
signal	id (<bar>#<n>), bar, side, quantity, price, exit, and the journal: rule, signal, regime	the bar
submitted	{signal, order}	the signal, accepted by the gate
refused	{signal, why} — a gate rejection, or frozen	the signal
exit	{signal, why, order} — sent without asking the gate	the signal
ignored	a sell to open, which no hosted rule does
filled	the execution: order, side, quantity, decision and fill prices and instants, proposer, and the position it left	the order
frozen	{discrepancies} or {stale}	the audit, or the feed
resumed	why, when the feed came back	a Resume, or the feed
resume_refused, reconcile_failed, audit_failed, fetch_failed, settle_failed	the reason
halted	why; for the kill switch also what flattened and what failed	the gate, or a Halt
warning	entered and cleared, the limits by name, and near, everything the session is near now in the gate's words: drawdown 8.1% of a 10.0% limit. Written when the set changes, not when a figure moves	a bar, or a settle
verdict	holding, diverging or inconclusive, and for diverging the reason (expectancy, drawdown, frequency, regime, execution) with what was seen and what was expected. Written when it changes	a settle
stopped		a Stop, or the engine stopping
failed	the reason	the loop ending on an error
dropped	after, the event the record ended on, and noticed_at. Stamped with the time of the record's last line, which is when the session ended, not when it was noticed	the next engine to start

A record ends with stopped, failed or dropped. An engine that is killed writes nothing on its way out, so its sessions' records stop wherever they were. The next engine to start on the project finds each one, adds the dropped line, raises an alert, and lists the session as dropped until it is started again. Stop an engine with arvo-engine shutdown and every record ends with stopped instead.

Either way, the sessions that were running come back. sessions/hosted.json lists what the engine has up, rewritten as that changes and left alone when the engine goes down. The next engine starts each one through the ordinary start, so the promotion gate runs and the reconcile adopts what the venue holds. A session that was frozen or halted is not brought back: it was waiting for a person. One the gate refuses is named in an alert.

Times are UTC. Every failure also raises an alert on the engine's event channel, which the window's alerts list and the Operations view show.