Shape. The script runs once, registers callbacks, and draws through plot. Everything runs on YOUR machine in a worker: no DOM, no network, 4 seconds per pass.

onBar((bar, i, $) => …) — every candle of the chart's timeframe, oldest first; the live candle again on each tick.
onTick((tick, bar, $) => …) — every coalesced price frame (~10/s). onFinish(($) => …) — after a full pass.

bar = { time, open, high, low, close, volume, delta } · $.close[i], $.high, $.low, $.open, $.volume, $.delta, $.time are typed arrays · $.bars, $.tf (seconds), $.symbol.

plot(name, value, { color, overlay: true|false, style: "line"|"hist"|"dots", width }) — overlay on the price chart, otherwise the script output pane.
plotted(name) — a plot's own values, for crosses and look-backs · hline(value, { color, label, overlay }) · marker(text, { at: "above"|"below", color }) · label(text, price, { color }) · bgcolor(color) · log(…) · input(name, default).

fp(bar) — the footprint rows of a candle, [{ price, buy, sell }] ascending (needs the live stream).

table(id, rows, { at: "top-right", title }) — a table on the chart; a row is an array of cells, a cell a string or { text, color, bg }.

Orders. buy(qty, { stop, target }) · sell(qty, { stop, target }) · close() · position() → { qty, avg, contract }. They fire only on live ticks, once per candle, on the Trade panel's contract and account — and only while allow trading is on, which switches off on every Run. Off, they are logged and marked, not sent.

Live candle. onBar runs again for the last candle on every tick, so accumulate per bar index (or through ta.cum / ta.vwap), never in plain counters.

ta.sma(arr, n, i) · ta.cum(arr, i) · ta.vwap($, i), ta.vwapSd($, i), ta.session(i) · ta.ema · ta.rsi · ta.atr($, n, i) · ta.highest(arr, n, i) · ta.lowest · ta.stdev · ta.change(arr, i, k) · ta.cross(a, b, i) — all computed at index i, cached across the pass.