Contributing to LangChain.js

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Ways to Contribute

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Report Bugs

1. Search existing issues: Check GitHub Issues to see if the bug has already been reported
2. Create a new issue: Include a minimal reproducible example and follow the issue template
3. Be patient: Maintainers will triage the issue and may ask for additional information

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Request Features

1. Search existing requests: Look through GitHub Issues for similar feature requests
2. Start a discussion: Propose your idea in the appropriate category for community feedback
3. Describe the use case: Explain why it would be valuable, provide examples or mockups, and outline test cases

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Contribute Code

• Find an issue: Look for issues labeled “good first issue” or “help wanted”
• Assign yourself: Comment on the issue or ask a maintainer to assign it to you to avoid duplicate work

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Add an Integration

• Discoverability: LangChain has over 20 million monthly downloads
• Interoperability: Standard interfaces allow developers to easily swap components
• Best Practices: Built-in support for streaming, async operations, and callbacks

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Getting Started

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Prerequisites

• Node.js v24.x (check with node -v)
• pnpm v10.14.0 (package manager)

nvm use

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Initial Setup

1. Fork and clone the repository using the “fork and pull request” workflow
2. Install dependencies from the project root:

cd langchainjs
pnpm install

3. Build the core package (required before working on other packages):

pnpm --filter @langchain/core build

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Common Tasks

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Package Filters

• --filter langchain - main langchain package
• --filter @langchain/core - core package
• --filter @langchain/community - community integrations
• --filter @langchain/openai - OpenAI integration (similar for other providers)

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Building

pnpm --filter langchain build
pnpm --filter @langchain/core build

pnpm watch

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Linting

pnpm --filter langchain lint
pnpm --filter @langchain/community lint

pnpm --filter langchain lint:fix

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Formatting

pnpm --filter langchain format

pnpm --filter langchain format:check

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Testing

pnpm --filter langchain test
pnpm --filter @langchain/core test

pnpm --filter langchain test:integration

pnpm --filter <package> test:single <path-to-test>

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Pull Request Guidelines

1. Fill out the PR template - Describe what your PR does, why it’s needed, and provide context
2. Link related issues - Use closing keywords like Fixes #123 to auto-close issues
3. Keep PRs focused - One feature or fix per PR makes review easier and faster
4. Add tests - Include unit tests for new functionality; integration tests for external APIs
5. Update documentation - If your change affects public APIs, update the relevant docs
6. Run checks locally - Ensure pnpm lint, pnpm format:check, and pnpm test pass before pushing

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Review Process

• A maintainer will review your PR and may request changes
• Please respond to feedback in a timely manner
• Once approved, a maintainer will merge your PR

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Getting Help

• Contact a maintainer - We want to help you get unblocked and improve the process for future contributors
• Don’t let standards block you - If linting or formatting is difficult, reach out for help. We don’t want these to prevent good code from being contributed

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Communication

• LangChain Forum - Technical questions, ideas, and feedback
• GitHub Issues - Bug reports and feature requests
• Slack - LangChain Community

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Release Process

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Dev Releases

1. Go to Actions → 📦 Publish
2. Click “Run workflow”
3. Select the branch (defaults to main)
4. Optionally change the npm tag (defaults to dev)
5. Click “Run workflow”

# Latest dev release
npm install @langchain/core@dev

# Specific dev version
npm install @langchain/[email protected]

• Testing bug fixes before official release
• Validating new features in downstream projects
• CI/CD pipelines that need to test against latest changes

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Next Steps