vercel__workflow/packages/nest

@workflow/nest

NestJS integration for Workflow SDK.

Installation

npm install @workflow/nest
# or
pnpm add @workflow/nest

You also need to install the SWC packages required by NestJS's SWC builder:

npm install -D @swc/cli @swc/core
# or
pnpm add -D @swc/cli @swc/core

Quick start

1. Initialize SWC configuration

After installing the package, run the init command to generate the SWC configuration:

npx @workflow/nest init

This creates a .swcrc file configured with the Workflow SWC plugin for client-mode transformations.

Important: Add .swcrc to your .gitignore as it contains machine-specific absolute paths:

echo '/.swcrc' >> .gitignore

2. Configure NestJS to use SWC

Ensure your nest-cli.json has SWC as the builder:

{/@skip-typecheck: Shows nest-cli.json configuration/}

{
  "compilerOptions": {
    "builder": "swc"
  }
}

3. Import the WorkflowModule

In your app.module.ts:

{/@skip-typecheck: Shows WorkflowModule import/}

import { Module } from '@nestjs/common';
import { WorkflowModule } from '@workflow/nest';

@Module({
  imports: [WorkflowModule.forRoot()],
})
export class AppModule {}

4. Create workflow files

Create workflow files in your src/ directory with "use workflow" and "use step" directives:

{/@skip-typecheck: Shows workflow file/}

// src/workflows/example.ts
export async function myStep(data: string) {
  'use step';
  return data.toUpperCase();
}

export async function myWorkflow(input: string) {
  'use workflow';
  const result = await myStep(input);
  return result;
}

5. Add pre-build scripts

Add scripts to regenerate configuration before builds:

{
  "scripts": {
    "prebuild": "npx @workflow/nest init --force",
    "build": "nest build"
  }
}

Configuration options

{/@skip-typecheck: Shows WorkflowModule.forRoot options/}

WorkflowModule.forRoot({
  // Directory to scan for workflow files (default: ['src'])
  dirs: ['src'],

  // Output directory for generated bundles (default: '.nestjs/workflow')
  outDir: '.nestjs/workflow',

  // Skip building in production when bundles are pre-built
  skipBuild: false,

  // SWC module type: 'es6' (default) or 'commonjs'
  // Set to 'commonjs' if your NestJS project compiles to CJS via SWC
  moduleType: 'es6',

  // Directory where NestJS compiles .ts to .js (default: 'dist')
  // Only used when moduleType is 'commonjs'
  // Should match the outDir in your tsconfig.json
  distDir: 'dist',
});

Deploying to Vercel

NestJS is not a Vercel-native framework, so the Workflow SDK emits a Vercel Build Output API directory (.vercel/output) for it. This includes the combined workflow queue-consumer function (registered with experimentalTriggers so Vercel Queue dispatches your runs) alongside your NestJS app bundled as a catch-all function. Without it, deployed workflow runs stay pending because nothing consumes the queue.

1. Add a serverless entry module

Create a _vercel/entry.ts that default-exports a Node request handler backed by your NestJS app (the _vercel/ prefix avoids colliding with Vercel's automatic api/ function detection). Import AppModule from the compiled dist/ output. nest build runs first, and its SWC pass emits the decorator metadata NestJS DI relies on; importing raw src/ TypeScript would route the app back through esbuild, which does not emit emitDecoratorMetadata. Also import reflect-metadata at the top so DI metadata is registered:

{/@skip-typecheck: Shows the Vercel entry module shape/}

// _vercel/entry.ts
import 'reflect-metadata';
import { NestFactory } from '@nestjs/core';
// Compiled by `nest build` before the Vercel Build Output step runs.
import { AppModule } from '../dist/app.module.js';

let ready: Promise<any> | undefined;

async function createHandler() {
  const app = await NestFactory.create(AppModule);
  await app.init();
  return app.getHttpAdapter().getInstance(); // the Express instance
}

export default async function handler(req: any, res: any) {
  ready ??= createHandler();
  const instance = await ready;
  return instance(req, res);
}

2. Skip the in-process build on Vercel

The Vercel Build Output already contains the compiled workflow bundles, so tell WorkflowModule not to rebuild them at runtime:

{/@skip-typecheck: Shows WorkflowModule.forRoot on Vercel/}

WorkflowModule.forRoot({ skipBuild: Boolean(process.env.VERCEL) })

3. Wire up the build command

Add a vercel-build script that compiles the app and then emits the Build Output. workflow-nest build emits the Vercel Build Output automatically when the VERCEL env var is set (pass --vercel to force it locally):

{
  "scripts": {
    "vercel-build": "nest build && npx @workflow/nest build"
  }
}

nest build (via SWC) compiles your app, including the decorator metadata and the workflow client transform. Then, @workflow/nest build bundles the app and the workflow functions into .vercel/output.

Note: Native addons (*.node) are not bundled or traced into the deployed function, so NestJS apps that depend on native modules are not yet supported by --vercel.

How it works

The @workflow/nest package provides:

1. WorkflowModule: A NestJS module that handles workflow bundle building and HTTP routing
2. WorkflowController: Handles workflow and step execution requests at .well-known/workflow/v1/
3. NestLocalBuilder: Builds workflow bundles (steps.mjs and workflows.mjs) from your source files. Exposed at the @workflow/nest/builder subpath (not the package root, which stays free of build-time dependencies so importing WorkflowModule never adds the compiler to your runtime bundle).
4. NestVercelBuilder: Emits a Vercel Build Output API directory for deploying on Vercel. Exposed at the @workflow/nest/vercel-builder subpath.
5. CLI: Generates .swcrc configuration with the SWC plugin resolved and builds workflow bundles or the Vercel Build Output

Why the CLI?

NestJS uses its own SWC builder that reads configuration from .swcrc. The Workflow SWC plugin needs to be referenced by path in this file. The CLI resolves the plugin path from @workflow/nest's dependencies, eliminating the need for manual configuration or pnpm hoisting.

Technical details

When you run npx @workflow/nest init, it:

1. Resolves the path to @workflow/swc-plugin (bundled as a dependency of @workflow/nest)
2. Generates .swcrc with the absolute path to the plugin
3. Configures client-mode transformation for workflow files

This approach ensures:

• No manual SWC plugin configuration required
• No pnpm hoisting configuration required in .npmrc
• The plugin is always resolved from the correct location

Why workflows must be in src/

NestJS's SWC builder only compiles files within the sourceRoot directory (typically src/). For the workflow client-mode transform to work, workflow files must be in src/ so they get compiled with the SWC plugin that attaches workflowId properties needed by start().

API reference

WorkflowModule

{/@skip-typecheck: Shows WorkflowModule usage/}

import { WorkflowModule } from '@workflow/nest';

// Basic usage
WorkflowModule.forRoot()

// With options
WorkflowModule.forRoot({
  dirs: ['src/workflows'],
  outDir: '.nestjs/workflow',
  skipBuild: process.env.NODE_ENV === 'production',
  moduleType: 'commonjs',  // if using SWC CommonJS compilation
  distDir: 'dist',          // where compiled .js files live
})

CLI commands

# Generate .swcrc configuration
npx @workflow/nest init

# Force regenerate (overwrites existing)
npx @workflow/nest init --force

# Build workflow bundles for local dev
npx @workflow/nest build

# Emit the Vercel Build Output (.vercel/output); implied when VERCEL is set
npx @workflow/nest build --vercel

# Show help
npx @workflow/nest --help

build options

Flag	Description	Default
--vercel	Emit a Vercel Build Output API directory (.vercel/output) with the workflow queue-consumer function. Implied when the VERCEL env var is set.	off (on under VERCEL)
--dirs <dirs>	Comma-separated workflow source directories to scan.	src
--entry <path>	Vercel app entry module that default-exports a Node request handler.	auto-detected (e.g. _vercel/entry.js)
--out-dir <dir>	Output directory for local-dev bundles (ignored with --vercel).	.nestjs/workflow
--module <type>	SWC module type: es6 or commonjs.	es6

License

Apache-2.0