Select and time signals

These operators select among one-shot signals or introduce durable time into an automation.

`fallback()`

fallback([preferred, backup]) selects by declaration order. A pending earlier input blocks later inputs. Closure advances to the next input; emission or failure is selected.

import { fallback } from "automate.ax"

const recipient = fallback([preferredRecipient, defaultRecipient])

TypeScript requires at least two inputs. Use race when completion order should decide instead.

`race()`

race([first, second]) selects the first causally related input to emit or fail. Closed inputs leave the race, and the race closes only when every input closes.

import { delay, race } from "automate.ax"

const elapsed = race([delay("3d"), delay("1d")]) // emits after one day

Continuation contexts with the same causal roots compete in one durable race. Independent trigger contexts race separately. TypeScript requires at least two inputs.

`delay()`

delay(duration) emits null in a child continuation after a durable relative delay:

import { delay } from "automate.ax"

const elapsed = delay("24h")

delay(duration, signal) starts when the signal emits and re-emits its value later. It preserves the signal’s keyed or global partition.

const followUp = delay("3d", request)

Pass a synchronous section as shorthand for scoping work under the elapsed signal:

delay("3d", () => {
  sendEmail({ subject: "Follow up", text: "Three days have elapsed." })
})

Durations accept type-checked compact strings such as "3d", millisecond numbers, or compatible signals.

`timeout()`

timeout(signal, duration) mirrors the source if it emits or fails before the deadline. If the deadline wins, the result fails with TimeoutError. Source closure leaves the deadline active, so the result fails when the deadline arrives.

import { timeout } from "automate.ax"

const result = timeout(providerResult, "1d")

The deadline can span execution jobs, including a timeout around a multi-day delay. It does not interrupt an action handler already running. timeout preserves the source’s keyed or global partition. See burst control when timing should coordinate repeated occurrences instead of one continuation.

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Select and time signals

`fallback()`

`race()`

`delay()`

`timeout()`

​fallback()

​race()

​delay()

​timeout()

`fallback()`

`race()`

`delay()`

`timeout()`