Event streams

Event streams record every completed Action as an immutable Event and deliver it, in order, to Triggers, Watches, live readers and replays.

ContractCopy Anchor Link

• Every change of an Action's status appends one Event, named in the past tense: Order.refunded, Lesson.booked.
• Events are ordered per namespace by sequence number and kept forever.
• One selector grammar matches Events everywhere: Triggers, Watches, Meters, Task completion rules and control tests.
• A Trigger wakes a Workflow on a match. A Watch delivers each match to a URL, signed, retried and replayable from any point.
• Only declared Event names feed Metrics. Undeclared names stay raw telemetry.
• Telemetry may be sampled. A billed Event never is.
• Outside events enter through one verified webhook door and are written as Events before any Workflow acts on them.

VerbsCopy Anchor Link

InterfacesCopy Anchor Link

• API
• SDK
• CLI
• MCP
• Webhooks

ExampleCopy Anchor Link

import { $ } from 'startup-builder'

// A course platform sends completions to a partner's learning system, then replays a missed week.
const { watch, secret } = await $.Watch.create({
  selector: 'Enrollment.completed where course = course_sql',
  url: 'https://lms.partner.example/hooks/completions',
})
// The secret is shown once: hand it to the receiver now.
await $.Watch.replay({ watch: watch.$id, from: '2026-10-01' })