Prose

Features

Type-safe State Threading

Each step’s return type merges into ctx.state, giving full autocomplete and compile-time checks across the entire pipeline.

Zero Dependencies

Runs in-process with no external infrastructure. Just async/await.

Retries & Backoff

Per-step retry policies with exponential backoff, delay caps, and conditional predicates.

Timeouts & Cancellation

Flow-level and step-level timeouts backed by AbortSignal with cooperative cancellation.

Database Transactions

Wrap steps in db.transaction() — works with Drizzle, Knex, Prisma, or any ORM.

Event Publishing

Emit domain events to named channels with automatic correlation IDs.

Parallel Execution

Run independent steps concurrently with configurable merge strategies.

Observability Hooks

Plug in logging, metrics, or tracing through the observer interface.

Quick Example

import { createFlow, ValidationError } from '@celom/prose';

const onboardUser = createFlow<{ email: string; name: string }>('onboard-user')
  .validate('checkEmail', (ctx) => {
    if (!ctx.input.email.includes('@'))
      throw ValidationError.single('email', 'Invalid email');
  })
  .step('createAccount', async (ctx) => {
    const user = await db.createUser(ctx.input);
    return { user };
  })
  .withRetry({ maxAttempts: 3, delayMs: 200, backoffMultiplier: 2 })
  .step('sendWelcome', async (ctx) => {
    await mailer.send(ctx.state.user.email, 'Welcome!');
  })
  .event('users', (ctx) => ({
    eventType: 'user.onboarded',
    userId: ctx.state.user.id,
  }))
  .build();

const result = await onboardUser.execute(
  { email: 'alice@example.com', name: 'Alice' },
  { db, eventPublisher }
);

Install

npm install @celom/prose