@beparallel/langchain-ts

A CLI tool that pulls prompts from LangSmith Hub and generates TypeScript types and optional JSON exports for offline use.

Features

• Type generation -- produces TypeScript interfaces, enums, and Zod schemas from prompt input/output schemas
• Prompt export -- serializes full prompt content to JSON files so you can load them offline without calling pull() at runtime
• Filtering -- narrow results to a specific prompt by name, or override the Hub tag
• Composable flags -- use --file and --export-dir independently or together in a single run

Installation

Install the package:

pnpm i @beparallel/langchain-ts

Configuration

Add the following environment variables (e.g. in a .env file):

| Variable | Required | Description | | ------------------ | -------- | --------------------------------------------- | | LANGCHAIN_API_KEY| Yes | Your LangSmith API key | | LANGCHAIN_TAG | Yes | The Hub tag to pull (e.g. latest, staging) |

LANGCHAIN_API_KEY=your_api_key
LANGCHAIN_TAG=your_tag

Usage

At least one of --file or --export-dir is required.

CLI flags

| Flag | Description | | ----------------- | ---------------------------------------------------- | | --file=PATH | Output path for the generated TypeScript types file | | --export-dir=DIR| Directory to write per-prompt JSON files | | --name=NAME | Filter prompts by name (partial match) | | --tag=TAG | Override the LANGCHAIN_TAG environment variable |

Examples

# Generate types only
npx langchain-types --file=./prompt.types.ts

# Export prompts as JSON only
npx langchain-types --export-dir=./prompts/

# Both at once
npx langchain-types --file=./prompt.types.ts --export-dir=./prompts/

# Filter to a single prompt
npx langchain-types --file=./prompt.types.ts --name=my-prompt

package.json scripts

A typical setup using dotenv-cli to load env vars:

{
  "scripts": {
    "prompt:generate": "dotenv -f .env run -- npx langchain-types --file=./types/prompts.ts",
    "prompt:export": "dotenv -f .env run -- npx langchain-types --export-dir=./prompts/",
    "prompt:all": "dotenv -f .env run -- npx langchain-types --file=./types/prompts.ts --export-dir=./prompts/"
  }
}

How prompt export works

The --export-dir flag calls LangChain's toJSON() on each ChatPromptTemplate and writes the result to <dir>/<tag>/<prompt-name>.json, organized by tag. For example, with --export-dir=./prompts/ --tag=staging:

prompts/
  staging/
    my-prompt.json
    another-prompt.json

These files contain the full serialized representation (message templates, input variables, output schema) and can be loaded with LangChain's load() deserialization -- no network call to the Hub required.

Programmatic API

The package also exports functions for use in your own scripts:

import { extractPrompts, generateTypes, exportPrompts } from '@beparallel/langchain-ts'

const prompts = await extractPrompts({
  langchainApiKey: process.env.LANGCHAIN_API_KEY!,
  langchainTag: 'latest',
})

generateTypes(prompts, './prompt.types.ts')
exportPrompts(prompts, './prompts/', 'latest')

Contributing

Setup

pnpm i

Environment

export LANGCHAIN_API_KEY=your_api_key
export LANGCHAIN_TAG=your_tag

Running locally

pnpm prompt:generate

Tests

pnpm test

Release

Publishing is automated via GitHub Actions. When a v* tag is pushed, the workflow runs tests, builds, publishes to npm, and creates a GitHub release with auto-generated notes.

# Bump version (patch, minor, or major) -- this updates package.json and creates a git tag
npm version patch   # 1.1.0 -> 1.1.1
npm version minor   # 1.1.0 -> 1.2.0
npm version major   # 1.1.0 -> 2.0.0

# Push the commit and tag to trigger the publish workflow
git push --follow-tags

Prerequisites: the repo needs NPM_TOKEN configured in GitHub Secrets (Settings > Secrets and variables > Actions).

Changelog

1.1.0

• Add --export-dir CLI flag to serialize prompts as JSON files for offline use
• Make --file optional (at least one of --file or --export-dir is now required)
• Add exportPrompts() to the programmatic API
• Clean up dead code in CLI entry point

1.0.0

• Upgrade to LangChain v1 (@langchain/core ^1.x, langchain ^1.x)

0.3.0

• Upgrade dependencies to latest versions
• Refactor parser module to use named import for pull from langchain/hub

0.2.8

• Add --name flag for filtering prompts by name (partial match)
• Add --tag flag for overriding LANGCHAIN_TAG from the command line

0.2.0

• Add ESLint, Jest, and Prettier configuration
• Introduce utility functions for case conversion
• Add unit tests for parser and type generator modules

0.1.0

• Initial release
• CLI for extracting LangSmith Hub prompts and generating TypeScript types
• Enum, interface, and Zod schema generation from prompt JSON schemas

License

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