Bar-close execution, and why it matters
Live strategies act when a bar closes, not on every tick, so live orders match the backtest.
A script re-runs on every tick of the forming bar. A crossover that appears at 10:14:20 can disappear by 10:14:59 if price pulls back. The backtest only ever saw closed bars, so a strategy that traded mid-bar would take trades its backtest never took.
- Intents from a forming bar are dropped. The closed bar's intents arrive with the next update and go through.
- History never emits orders in live modes: arming a strategy does not replay past signals.
- The same signal is never sent twice. Each intent has a content key (script, symbol, interval, bar time, order) that becomes the broker's client order id.
- Tick execution (Settings → Automation) lets forming-bar intents through, for
calc_on_every_tickscripts. Expect live results to drift from the backtest.
What it costs
Acting at the close means entering up to one bar later than an intrabar signal. On a 5-minute chart that is at most five minutes. In exchange, what you backtested is what trades.