Spectra
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Scripting reference

The Spectra DSL: five script kinds, sandboxed bytecode VM, three runtimes.

The Spectra DSL is a small, statically-typed language designed to express trading logic without scaffolding. It compiles to bytecode that runs in three places — chart preview, the backtester, and the 24/7 cloud worker.

What to read first

  • Grammar — keywords, types, and the expression grammar in EBNF.
  • Built-in functions — sma, ema, rsi, crossover, etc.
  • Script kinds — Indicator, Alert, Screener, Drawing, Strategy, with the surface each one targets.
  • Sandbox limits — CPU and memory budgets, what the VM forbids, and how to opt into longer windows.
  • Tick-based scripting — individual executions, on_trade, server alerts, and archive tick replay.

Hello, indicator

// @spectra-script 2
// Plot the 20-period SMA on the price pane.
let m = ta.sma(close, 20)
plot.line("SMA 20", m, color = color.orange, width = 2.0, force_overlay = true)
output m

Hit Run Preview (or Save) and the line draws on the chart. Recompilation on every keystroke fires under 80 ms — you see the line move as you change the period.

The script editor

Open the Scripts panel from the top menu — or View → Add Panel → Scripts — and it docks like any other widget, so you can split it beside the chart. The Editor tab is a first-class code editor:

  • Syntax highlighting across the whole ta. / plot. / param. / color. surface.
  • Autocomplete — start a built-in (e.g. type ta.) and pick from the list; ↑/↓ to move, Enter/Tab to accept.
  • Live diagnostics — a red underline on the offending span plus a Problems strip, recompiled as you type.
  • Pop out to Monaco — the same editor VS Code uses, in a detached window for a full-IDE feel.

On the web build the docked editor is Monaco, mounted right in the panel. A pinned toolbar keeps Save / Revert / Run Preview in reach no matter how long the script gets — the code scrolls inside its own box.

Drag-slider comparing a plain candlestick chart with the same chart after a user-written indicator plots on itBeforeAfter
Before: plain candles. After: your indicator plotted.
Type, save, see it plot — under 80 ms from save to render.

Strategy in five lines

let fast = sma(close, 12)
let slow = sma(close, 26)
if cross_up(fast, slow) { buy(qty: 1) }
if cross_down(fast, slow) { sell(qty: 1) }
output fast - slow

The same file backtests against historical bars in the Strategy panel and fires real orders in live mode — no flag flips required. The auto-flip rule (see Script kinds) ensures indicator-style strategies actually close their positions.

Where to go from here

If you're coming from Pine Script, the most useful page is Grammar — the surface area is similar but the type system is stricter. If you're coming from C-like languages, start at Built-in functions instead.