@pattern-js/runtime-node

The Node runtime adapter for Pattern. Thin by design — it binds external sources to boundary triggers and provides isolation. All platform code lives here so @pattern-js/core stays runtime-neutral.

npm install @pattern-js/core @pattern-js/runtime-node

Project loader (recommended)

import { loadProject } from "@pattern-js/runtime-node";

const { engine, start } = await loadProject();  // reads pattern.config.json
const { ports } = await start();                // derives routes from workflows

loadProject installs mods, loads workflow .json files, and returns a ready HTTP host. See projects & mods.

Hosts

Routing is declarative: the HTTP host derives routes from the boundary.http.request nodes of registered workflows (method/path/port/cors/ body+query JSON-Schema all in config). No programmatic route table.

import { Engine } from "@pattern-js/core";
import { createHttpHost } from "@pattern-js/runtime-node";

const engine = new Engine();
engine.registerWorkflow(api);                 // route declared inside the workflow
const host = createHttpHost(engine, { defaultPort: 3000 });
const { ports } = await host.start();         // re-derives live as workflows change

| Host | Binds | Out-gate | |------|-------|----------| | createHttpHost | boundary.http.request (declarative routes) | boundary.http.response (buffered/sse/chunked) | | createWsHost | boundary.ws.message / open / close | boundary.ws.send | | runCli | boundary.cli | boundary.cli.exit | | createScheduleHost | boundary.schedule (interval or 5-field cron) | result discarded/traced |

Isolation: worker-thread pool

A RunTransport that runs each workflow on a node:worker_threads worker — a drop-in for the in-process transport. Streamed out-gate results are reconstructed on the host; cancellation crosses the seam.

import { WorkerPoolTransport } from "@pattern-js/runtime-node";
const engine = new Engine({ transport: new WorkerPoolTransport({ size: 4 }) });

Also here

• NodeConnectionRegistry — ConnectionRegistry bound to live WebSocket sockets (rooms, broadcast, streamed sends).
• Trace sinks — jsonlTraceSink(path) and sqliteTraceSink(path) for persistence (core only emits).
• loadMods(engine, specifiers) — load external plugin mods by module specifier.
• pattern CLI — pattern graph|validate|dev.

CLI

pattern graph workflow.json      # render the graph in the terminal
pattern validate workflow.json   # located, human-readable validation errors
pattern dev [entry]              # run an entry with file-watch hot-reload