Blyp Logger

The silent observer for your applications

Blyp is a high-performance, runtime-adaptive logger for standalone apps and modern TypeScript web frameworks. It combines Bun-friendly runtime detection, structured NDJSON file logging, browser-to-server log ingestion, and framework-specific HTTP logging helpers.

Features

• Runtime detection — Automatically optimizes for Bun vs Node.js
• TypeScript — Full type safety throughout
• Framework integrations — Elysia, Hono, Express, Fastify, NestJS, Next.js App Router, TanStack Start, SvelteKit, Cloudflare Workers
• Expo integration — Mobile client logging for Expo apps with structured backend sync
• PostHog connector — Automatic or manual PostHog log forwarding for server, browser, and Expo flows
• OTLP connector — Automatic or manual OpenTelemetry log forwarding for Grafana, Datadog, Honeycomb, and any OTLP-compatible backend
• Standalone usage — Use without any framework
• Structured file logging — NDJSON with size-based rotation and gzip archives
• Database logging — Serverless-friendly persistence with Prisma and Drizzle adapters for Postgres and MySQL
• Client log sync — Browser logs ingested into your backend stream

Project structure

blyp/
├── exports/
│   ├── client.js              # Public client entry shim
│   ├── connectors/
│   │   └── posthog.js         # Public connector entry shims
│   └── frameworks/
│       └── elysia.js          # Public framework entry shims
├── index.ts                   # Main source export bridge
├── src/
│   ├── core/                  # Logger runtime and file logging internals
│   ├── connectors/            # Connector implementations
│   ├── frameworks/            # Framework implementations
│   ├── shared/                # Shared runtime/error utilities
│   └── types/
│       ├── framework.types.ts # Shared public contracts
│       ├── connectors/
│       │   └── posthog.ts     # Connector-specific source types
│       └── frameworks/
│           └── elysia.ts      # Framework-specific source types
├── types/
│   ├── index.d.ts             # Public type entry shim
│   ├── connectors/
│   │   └── posthog.d.ts       # Public connector type shims
│   └── frameworks/
│       └── elysia.d.ts        # Public framework type shims
├── tests/
│   ├── frameworks/            # One test file per server integration
│   ├── helpers/               # Shared test utilities
│   ├── *.test.ts              # Focused core tests
│   └── README.md              # Test documentation
└── README.md

Installation

bun add blyp-js
npx expo install expo-network

Also: npm install blyp-js | yarn add blyp-js | pnpm add blyp-js

Usage

Basic logger

import { logger } from 'blyp-js';

logger.info('Hello world');
logger.success('Operation completed');
logger.error('Something went wrong');
logger.warning('Warning message');

Structured request batches

Standalone usage:

import { createStructuredLog } from 'blyp-js';

const structuredLog = createStructuredLog('checkout', {
  service: 'web-api',
  level: 'info',
  timestamp: new Date().toISOString(),
});

structuredLog.set({
  user: { id: 1, plan: 'pro' },
  cart: { items: 3, total: 9999 },
});

structuredLog.info('user logged in');
structuredLog.info('item added to cart');
structuredLog.emit({ status: 200 });

Framework usage with Elysia:

import { createStructuredLog } from 'blyp-js';
import { Elysia } from 'elysia';
import { createLogger } from 'blyp-js/elysia';

const app = new Elysia()
  .use(createLogger({ level: 'info' }))
  .post('/hello', ({ set }) => {
    const structuredLog = createStructuredLog<{
      message: string;
      level: string;
      timestamp: string;
      hostname?: string;
      port?: number;
    }>('test', {
      message: 'Hello Elysia',
      level: 'info',
      timestamp: new Date().toISOString(),
      hostname: app.server?.hostname,
      port: app.server?.port,
    });

    structuredLog.info('route started');
    structuredLog.emit({ status: 200 });

    set.status = 200;
    return 'ok';
  });

Inside framework handlers, the imported createStructuredLog(...) automatically binds to the active request-scoped logger. Structured logs are emitted only when you call .emit(). In framework request loggers, a structured emit replaces that request's normal auto request log. If you mix a request-scoped structured logger with the root logger in the same request, Blyp warns once and ignores the root logger call.

Errors

import { createError } from 'blyp-js';

throw createError({ status: 404, message: 'Not found' });

For the full error API (HTTP_CODES, extend, create), see Full documentation.

Framework integrations

Blyp supports Elysia, Hono, Express, Fastify, NestJS, Next.js, TanStack Start, SvelteKit, and Cloudflare Workers. Example with Elysia:

import { Elysia } from 'elysia';
import { createLogger } from 'blyp-js/elysia';

const app = new Elysia()
  .use(createLogger({ level: 'info', autoLogging: true }))
  .get('/', () => 'Hello World')
  .listen(3000);

For other frameworks, client logging, advanced configuration, and utilities, see Full documentation.

Expo

import { createExpoLogger } from 'blyp-js/expo';

const logger = createExpoLogger({
  endpoint: 'https://api.example.com/inngest',
});

logger.info('app mounted');

Expo uses the runtime fetch implementation for delivery and expo-network for connectivity metadata. Install expo-network in your app and use an absolute ingestion URL.

Database logging

Use destination: 'database' when you cannot rely on filesystem writes, such as serverless deployments. Database mode requires an executable config file like blyp.config.ts because Prisma and Drizzle adapters are runtime objects.

Prisma:

import { PrismaClient } from '@prisma/client';
import { createPrismaDatabaseAdapter } from 'blyp-js/database';

const prisma = new PrismaClient();

export default {
  destination: 'database',
  database: {
    dialect: 'postgres',
    adapter: createPrismaDatabaseAdapter({
      client: prisma,
      model: 'blypLog',
    }),
  },
};

Drizzle:

import { createDrizzleDatabaseAdapter } from 'blyp-js/database';
import { db } from './db';
import { blypLogs } from './db/schema/blyp';

export default {
  destination: 'database',
  database: {
    dialect: 'mysql',
    adapter: createDrizzleDatabaseAdapter({
      db,
      table: blypLogs,
    }),
  },
};

In database mode, Blyp keeps connectors working as usual and replaces only the primary local persistence backend. Promise-based framework integrations flush database writes before the request finishes. In callback-style servers, call await logger.flush() at your own boundary when you need a hard durability point.

Use the Blyp CLI to scaffold the schema and migrations:

blyp logs init --adapter prisma --dialect postgres
blyp logs init --adapter drizzle --dialect mysql

Better Stack

Use connectors.betterstack when you want Blyp logs forwarded into Better Stack through @logtail/node:

export default {
  connectors: {
    betterstack: {
      enabled: true,
      mode: 'auto',
      sourceToken: process.env.SOURCE_TOKEN,
      ingestingHost: process.env.INGESTING_HOST,
      errorTracking: {
        dsn: process.env.BETTERSTACK_ERROR_TRACKING_DSN,
        tracesSampleRate: 1.0,
      },
    },
  },
};

INGESTING_HOST must be a full absolute http:// or https:// URL. Blyp does not auto-read SOURCE_TOKEN or INGESTING_HOST; wire them through your config explicitly.

In auto mode, the normal Blyp server loggers forward to Better Stack automatically. In manual mode, use blyp-js/betterstack:

import {
  captureBetterStackException,
  createBetterStackErrorTracker,
  createBetterStackLogger,
  createStructuredBetterStackLogger,
} from 'blyp-js/betterstack';

createBetterStackLogger().info('manual better stack log');
createBetterStackErrorTracker().capture(new Error('manual better stack exception'));
captureBetterStackException(new Error('wrapped better stack exception'));

const structured = createStructuredBetterStackLogger('checkout', {
  orderId: 'ord_123',
});
structured.info('manual start');
structured.emit({ status: 200 });

When connectors.betterstack.errorTracking.dsn is configured, Blyp captures handled server errors into Better Stack error tracking using the Sentry SDK. Client error and critical logs requested through the Better Stack connector are promoted to exceptions as well.

Browser and Expo loggers can request server-side Better Stack forwarding through the existing ingestion endpoint:

import { createClientLogger } from 'blyp-js/client';

const logger = createClientLogger({
  endpoint: '/inngest',
  connector: 'betterstack',
});

import { createExpoLogger } from 'blyp-js/expo';

const logger = createExpoLogger({
  endpoint: 'https://api.example.com/inngest',
  connector: 'betterstack',
});

The browser and Expo connector flow still posts to Blyp first. Blyp forwards to Better Stack only when the server connector is configured. Browser and Expo apps do not use @logtail/browser directly. Workers remain out of scope for this connector.

PostHog

Use blyp.config.ts when you want to read the PostHog project key from the environment:

export default {
  connectors: {
    posthog: {
      enabled: true,
      mode: 'auto',
      projectKey: process.env.POSTHOG_PROJECT_KEY,
      errorTracking: {
        enabled: true,
        mode: 'auto',
      },
    },
  },
};

In auto mode, the normal Blyp server loggers forward to PostHog automatically. In manual mode, use blyp-js/posthog:

import {
  capturePosthogException,
  createPosthogErrorTracker,
  createPosthogLogger,
  createStructuredPosthogLogger,
} from 'blyp-js/posthog';

createPosthogLogger().info('manual posthog log');
createPosthogErrorTracker().capture(new Error('manual posthog exception'));
capturePosthogException(new Error('wrapped posthog exception'));

const structured = createStructuredPosthogLogger('checkout', { orderId: 'ord_123' });
structured.info('manual start');
structured.emit({ status: 200 });

connectors.posthog.errorTracking.mode: 'auto' also captures Blyp handled server errors and can enable uncaught exception / unhandled rejection autocapture through enableExceptionAutocapture.

Browser and Expo loggers can request server-side PostHog forwarding through the existing ingestion endpoint:

import { createClientLogger } from 'blyp-js/client';

const logger = createClientLogger({
  endpoint: '/inngest',
  connector: 'posthog',
});

Client error and critical logs requested through the PostHog connector are promoted to PostHog exceptions only when server-side PostHog error tracking is enabled in auto mode.

The client and Expo connector flow still posts to Blyp first. Blyp forwards to PostHog only when the server connector is configured, and browser or Expo apps do not use posthog-node directly. Workers remain out of scope for this connector.

Sentry

Use connectors.sentry when you want Blyp logs forwarded into Sentry Logs:

export default {
  connectors: {
    sentry: {
      enabled: true,
      mode: 'auto',
      dsn: process.env.SENTRY_DSN,
      environment: process.env.SENTRY_ENVIRONMENT,
      release: process.env.SENTRY_RELEASE,
    },
  },
};

In auto mode, normal Blyp server loggers forward to Sentry automatically. In manual mode, use blyp-js/sentry:

import { createSentryLogger, createStructuredSentryLogger } from 'blyp-js/sentry';

createSentryLogger().info('manual sentry log');

const structured = createStructuredSentryLogger('checkout', {
  orderId: 'ord_123',
});
structured.info('manual start');
structured.emit({ status: 200 });

Browser and Expo loggers can request server-side forwarding through Blyp's ingestion endpoint:

import { createClientLogger } from 'blyp-js/client';

const logger = createClientLogger({
  endpoint: '/inngest',
  connector: 'sentry',
});

import { createExpoLogger } from 'blyp-js/expo';

const logger = createExpoLogger({
  endpoint: 'https://api.example.com/inngest',
  connector: 'sentry',
});

The browser and Expo Sentry flow still posts to Blyp first. Blyp forwards to Sentry only when the server connector is configured. If Sentry was already initialized by the app, Blyp reuses that client instead of replacing it.

OTLP

Use connectors.otlp when you want to send logs to named OTLP-compatible backends such as Grafana Cloud, Datadog, Honeycomb, or a self-hosted OpenTelemetry Collector:

export default {
  connectors: {
    otlp: [
      {
        name: 'grafana',
        enabled: true,
        mode: 'auto',
        endpoint: 'http://localhost:4318',
        headers: {
          'x-scope-orgid': process.env.GRAFANA_SCOPE_ID!,
        },
        auth: process.env.GRAFANA_AUTH,
      },
      {
        name: 'honeycomb',
        enabled: true,
        mode: 'manual',
        endpoint: 'https://api.honeycomb.io',
        headers: {
          'x-honeycomb-team': process.env.HONEYCOMB_API_KEY!,
        },
      },
    ],
  },
};

In auto mode, normal Blyp server loggers forward to every ready OTLP target automatically. In manual mode, use blyp-js/otlp and select a named target:

import { createOtlpLogger, createStructuredOtlpLogger } from 'blyp-js/otlp';

createOtlpLogger({
  name: 'grafana',
}).info('manual otlp log');

const structured = createStructuredOtlpLogger(
  'checkout',
  { orderId: 'ord_123' },
  { name: 'honeycomb' }
);
structured.info('manual start');
structured.emit({ status: 200 });

Browser and Expo loggers can request server-side forwarding to a named OTLP target through the existing ingestion endpoint:

import { createClientLogger } from 'blyp-js/client';

const logger = createClientLogger({
  endpoint: '/inngest',
  connector: { type: 'otlp', name: 'grafana' },
});

import { createExpoLogger } from 'blyp-js/expo';

const logger = createExpoLogger({
  endpoint: 'https://api.example.com/inngest',
  connector: { type: 'otlp', name: 'grafana' },
});

The browser and Expo OTLP flows still post to Blyp first. Blyp forwards to the named OTLP target only when that server connector is configured and ready.

Log levels, HTTP request logging, and file logging (rotation, archives, reading stored logs) are documented in docs.

Testing

Run tests:

bun run test

The suite covers runtime detection, standalone and client logger, file logging, and all framework integrations. For more commands and previews, see tests/README.md.

Development

Prerequisites: Bun 1.2+ (or Node.js 18+), TypeScript 5.0+

git clone https://github.com/Blyphq/blyp.git
cd blyp
bun install
bun run test
bun run build
bun run type-check

Publishing

GitHub Actions publishes the package to npm when a GitHub Release is published. Add an NPM_TOKEN repository secret before using the workflow.

Contributing

Contributions are welcome. See CONTRIBUTING.md for how to get set up and submit changes.

License

This project is licensed under the MIT License — see the LICENSE file for details.

Acknowledgments

Winston · Elysia · Chalk · Bun

Links

• GitHub Repository
• NPM Package
• Documentation
• Issues

Blyp silently watches over your applications, logging everything that happens under its watchful gaze.