The audit chain and the trade journal

Why did Arvo own 137 shares at 14:37:22? needs one chain: bar → signal → gate decision → order → acknowledgement → fill → position. Arvo records it twice, in the same words.

In a session's record

Each event names its cause: a signal names the bar it was decided on (id is <bar>#<n>), submitted, refused and exit name the signal, a filled names the order and the position it left, a reconciled names the whole book after. So the record is a chain rather than a log, and one reader walks it:

arvo-engine session explain <finding>@<executor> 2026-09-21T14:00:00Z

AAPL.AIEX: 297 at 2026-09-21T14:00:00+00:00
  fill 1 of 1
    bar       2026-09-21T13:45:00 close 335.73
    signal    2026-09-21 13:45:00#0  buy 297 @ 335.73  rule: close above the opening range = 0.101  regime: ranging
    gate      accepted; order fe043155-… acknowledged 2026-09-21T13:55:11
    fill      buy 297 @ 335.89 at 2026-09-21T13:55:12  (decided @ 335.73 → position 297)

A position the session adopted through a reconcile says so instead of inventing a bar behind it. How to explain a position →

Losses, grouped

A single loss is a ledger row. What says how a rule is failing is losses grouped by the condition that fired, the regime at entry and the exit reason, with the finding's out-of-sample figure for the same group beside each. "Stop exits in ranging regimes" is a diagnosis; a list of red rows is not. The Trades tab and the after-close review both show the grouping.

The operator's behaviour

The record also holds what the person did: positions adopted because something traded by hand, halts and resumes, a session stopped after a losing day, a ruleset edited while a session ran on it. The after-close review counts these beside the day's P&L, because intervening after losses is the most common way a Supported rule underperforms its backtest.

On every trade

Backtest and live alike, each trade carries a journal: the condition that fired in the rule's words, the value it was judged on (a spread, a distance in ATRs, a deviation), the regime the instrument was in at entry (trending up, trending down, ranging) and the quantity the rule asked for before the gate sized it. The Trades tab of a finding shows them; the CSV export writes them; an agent asked why did this trade fail has something to reason from.