Implementation:Helicone Helicone Dev Server Startup

Knowledge Sources	Helicone
Domains	Local Development, Services
Last Updated	2026-02-14 00:00 GMT

Overview

Concrete tool for starting the three main Helicone application services (Jawn, Web, Worker) in development mode, provided by Yarn scripts and Wrangler CLI.

Description

Each application service has its own development start command defined in its package.json:

Jawn (valhalla/jawn/package.json line 7): yarn dev runs concurrently "nodemon" "nodemon -x python3 genTypes.py" which starts the Express.js server with auto-reload and a parallel Python process for generating TypeScript types.
Web (web/package.json line 9): yarn dev:local runs next dev --turbo -p 3000 which starts the Next.js development server with Turbopack for fast rebuilds. An alternative yarn dev:better-auth (line 11) starts on port 3008 with Better Auth environment variables.
Worker (worker/wrangler.toml): Started via npx wrangler dev with --var WORKER_TYPE:OPENAI_PROXY flag. The default development configuration listens on port 8787 and connects to local Supabase, ClickHouse, MinIO, and Jawn.

Usage

Start services in order: Jawn first (port 8585), then Web (port 3000), and optionally Worker (port 8787). Each runs in its own terminal.

Code Reference

Source Location

Repository: Helicone
File: valhalla/jawn/package.json (lines 4-13), web/package.json (lines 8-20), worker/wrangler.toml (lines 1-107)

Signature

# Jawn backend
cd valhalla/jawn && yarn dev

# Web frontend
cd web && yarn dev:local

# Worker proxy
cd worker && npx wrangler dev --local --var WORKER_TYPE:OPENAI_PROXY --port 8787

Import

# Install all monorepo dependencies from the repository root
yarn install

# Wrangler is a dev dependency of the worker package
# No additional global installs needed

I/O Contract

Inputs

Name	Type	Required	Description
Infrastructure services	services	Yes	PostgreSQL, ClickHouse, MinIO must be running
.env files	files	Yes	Environment variables for each service
node_modules	directory	Yes	Dependencies installed via `yarn install`
WORKER_TYPE	string	Worker only	Worker variant: `OPENAI_PROXY`, `ANTHROPIC_PROXY`, `HELICONE_API`, `GATEWAY_API`, `GENERATE_API`

Outputs

Name	Type	Description
Jawn API	HTTP server	Express.js backend at `http://localhost:8585`
Web Dashboard	HTTP server	Next.js frontend at `http://localhost:3000` (or 3008 with better-auth)
Worker Proxy	HTTP server	Cloudflare Workers proxy at `http://localhost:8787`

Usage Examples

Basic Usage

# Terminal 1: Start the Jawn backend API
cd valhalla/jawn
yarn dev
# Output: Server listening on port 8585

Start Web Frontend

# Terminal 2: Start the Next.js web dashboard
cd web
yarn dev:local
# Output: Next.js dev server on http://localhost:3000

Start Web with Better Auth

# Alternative: Start web with Better Auth integration
cd web
yarn dev:better-auth
# Output: Next.js dev server on http://localhost:3008

Start Worker Proxy

# Terminal 3: Start the OpenAI proxy worker
cd worker
npx wrangler dev --local --var WORKER_TYPE:OPENAI_PROXY --port 8787
# Output: Worker listening on http://localhost:8787

Start Different Worker Types

# Anthropic proxy
npx wrangler dev --local --var WORKER_TYPE:ANTHROPIC_PROXY --port 8789

# Helicone API worker
npx wrangler dev --local --var WORKER_TYPE:HELICONE_API --port 8788

# Gateway API worker
npx wrangler dev --local --var WORKER_TYPE:GATEWAY_API --port 8790

Jawn Dev Script Breakdown

The Jawn yarn dev script runs two processes in parallel via concurrently:

concurrently "nodemon" "nodemon -x python3 genTypes.py"

nodemon: Watches TypeScript source files and restarts the Express.js server on changes.
nodemon -x python3 genTypes.py: Watches for changes and regenerates TypeScript types from the API schema.

Related Pages

Implements Principle

Principle:Helicone_Helicone_Application_Services

Requires Environment

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Principle

Implementation

Heuristic

Environment