Sessions

A session is a finding's rule, running against a venue: one finding, one executor, one thread in the engine. The rule is rebuilt as a shadow engine warmed on the library up to today; from then on each completed bar is pushed through it, entries go to the risk gate and exits go straight to the venue.

A session started after the open catches up on the bars it missed the same way: the rule is warmed on them and their signals are on the record, but an entry from a bar that closed before the session started is refused (catch-up: …), never sent. Yesterday's signal at today's market is not the trade the finding measured. Exits still go, as under a freeze.

An exit is stamped at the moment it is sent, like an entry, so the two-minute stale rule measures the venue and not the bar. An order that ends at the venue without a fill (cancelled, rejected, expired) is an unfilled event on the record, counts in the session's divergence, and is a line in the day's review.

Start one from the Sessions tab (choose a finding, choose an executor) or the command line. The executors are alpaca-paper, alpaca-live and robinhood-<last four>. Paper is drawn apart from real money everywhere it appears.

What a session does every poll

• fetches new bars (or takes them from the stream) and pushes each one the moment it is over — a daily bar's signal fires overnight and fills at the open, the fill the backtest assumed;
• settles: collects fills and books them on the gate;
• audits its book against the venue's, and freezes on a disagreement.

States

State	Meaning
starting	opening the finding, warming the shadow
running	polling or streaming, taking entries
frozen	entries wait for a person; exits still go. Either the book disagrees with the venue (reconcile, then resume) or the feed has gone dark (lifts itself when the feed returns)
halted	the gate stopped the account: the drawdown halt, or the kill switch. Stays until released
stopped	asked to stop; positions left as they are
failed	the thread ended with an error; the reason is on the row
dropped	the engine hosting it ended without stopping it; the next engine found the record unfinished

A session that was starting or running when the engine went down comes back when the next engine starts, through the ordinary start: the gate runs and the reconcile adopts what the venue holds. A frozen or halted one waits for a person, as it did.

Reconciliation as an incident

A position the venue reports and the gate does not — a fill this process never heard, a hand-placed order, a broker-side liquidation — means the rule can no longer size against a book it trusts. The session freezes and records the discrepancy. Reconcile makes the gate's book the venue's (the venue holds the money); Resume takes entries again, and is refused until a reconcile has happened. Both are events in the record. Nothing resumes on its own.

The promotion gate

A real-money executor takes only a finding that earned it. On start, a session on alpaca-live or a Robinhood account is refused unless:

• the finding's verdict is Supported;
• the finding has run on alpaca-paper for at least five days, by the paper session's record: days on which it took a bar, not calendar days, so a session stopped for a fortnight has not run for one;
• that paper session was not Diverging from the finding when last judged.

The refusal names the gate and every reason at once, so they can be fixed together. Paper needs no promotion. The gate is on the start itself, for people and agents alike: nothing else creates a session.

The Sessions tab asks the gate as soon as a finding and an executor are chosen and shows the road under the form: the finding's verdict, the days on paper and the paper session's verdict, and for a real-money executor either the reasons it refuses or that it allows. The button reads Promote for real money and stays disabled while the gate refuses. The same question is on the API as CheckPromotion, so an agent given the control tier can ask before it tries.

The kill switch

Halt arms the gate and then flattens everything the session holds, in that order, so a proposer racing in is refused rather than opening into the exit. What the venue would not exit is named in the record and on the status; the halt stands either way. From a session's row, from the Operations view, from the tray (Halt trading, every session) or from the command line. How to halt →

What the fills cost

A paper session exists to measure what a backtest cannot: what a fill actually costs against the price the decision was made at. Once anything has filled, the session carries its divergence: mean and worst adverse slippage in basis points across its fills, with the slippage the finding's cost model assumed beside it, the mean signal-to-fill latency, and how many approved orders never filled (never averaged in: a backtest assumes every order fills). It is under the selected session in the Sessions tab and on session list, and the verdict's execution reason reads the same figure.

When a rule stops working

A finding says whether a rule worked on its out-of-sample window. A session answers the question that comes next, in the same vocabulary:

Verdict	Meaning
Holding	the live trades sit inside what the out-of-sample distribution would produce
Diverging	expectancy, drawdown or firing rate has left that range; the reason is named
Inconclusive	too few live trades to say, which is where every session starts

The expectation comes from the finding: its out-of-sample trade distribution, its max drawdown, how often the rule fired, and which regimes its trades landed in. The session's own ledger, with the same journal on every trade, is compared against it as the trades accumulate. A rule that fires a quarter as often as it did is a regime change before it is a loss; entries landing in a regime the finding was never Supported in are a reason before the money says so.

A verdict is not a risk limit. Diverging changes nothing at the gate. It is recorded, raised as an alert, shown on the session and in Operations, and it is the case for demoting the session, decided by a person or the agent. The drawdown halt and the daily loss limit protect the account; the verdict judges the rule.

The verdict is on the session's row in the Sessions tab and in Operations, in session list on the command line, and on the record as a verdict event each time it changes. The expectation the session was judged against is the record's expectation event, written at the start. A session on a walk-forward or a reported finding has no out-of-sample ledger to expect anything from, and stays Inconclusive; the record says so.

The thresholds, so a verdict can be read: the expectancy comparison waits for ten closed live trades and fires when the live mean is more than two standard errors below the finding's; the drawdown reason fires at one and a half times the finding's out-of-sample maximum, at any trade count; the frequency reason once four entries were due and fewer than a quarter, or more than four times, as many came; the regime reason when most entries, and at least three, landed in a regime the finding never traded in; the execution reason after five fills, when slippage is past twice what the cost model assumed.

Since engine 0.4.0

A session started by an older engine shows an empty verdict.

The record

Everything a session does is one JSON line per event in sessions/<finding>@<executor>.jsonl, and every event names what caused it. The audit chain → · Record reference →