LemonBeam: An Open-Source Tool for Verified GitHub Onboarding Guides

Introduction

LemonBeam is an open-source AI tool designed to help developers navigate unfamiliar codebases. It creates onboarding guides that include verifiable citations, ensuring that every piece of information is backed by actual source code. Built by Kanami Anderson, John DeLong, and Tanisha Thompson-Jones, the tool solves a common problem: helping new contributors understand a project quickly and accurately without relying on guesses or hallucinations from AI models.

Benefits

LemonBeam offers several key advantages for developers and project maintainers. First, it provides a structured summary of a repository across six standard sections, including project overview, setup instructions, local running steps, directory structure, testing methods, and a list of uncertainties. This structure makes it easy to find specific information without digging through thousands of lines of code.

Second, the tool prioritizes honesty and accuracy. Instead of making things up, LemonBeam breaks the codebase into smaller pieces, ranks the most useful evidence, and keeps the AI prompt within a safe token budget. Every claim in the guide is automatically validated against the source code. If the tool cannot verify a fact, it removes or flags it rather than presenting it as truth. This feature prevents the common AI issue of hallucination.

Third, LemonBeam is cost-effective and private. The cost to generate a guide is approximately two cents after recent optimizations. The tool uses an MIT license and does not store user data. It follows a bring-your-own-key model where API keys are only used for the active scan request and are never saved by the frontend.

Use Cases

LemonBeam is built for developers joining an unfamiliar codebase, open-source contributors deciding where to start their work, and maintainers who want a quick guide for their team. The tool can be used in three different ways to fit various workflows.

The first option is a web app. This is a clean dashboard where users paste a public GitHub repository URL and enter their API key to generate a guide. This is ideal for visual exploration and team onboarding sessions.

The second option is a command line interface. This is a terminal utility that scans a local project directory or a GitHub URL and generates a Markdown guide. This allows developers to create guides without breaking their existing workflow.

The third option is an MCP server. This is a local server compatible with AI assistants like Claude Code and Claude Desktop. It enables real-time architecture testing and context support within AI coding agents.

Pricing

The tool costs approximately two cents per guide. This low cost was achieved after an early pipeline fix reduced the price from around 70 cents. Users need to provide their own OpenRouter API key to run the scans.

Vibes

LemonBeam represents a shift from general-purpose AI summaries to grounded, inspectable, and consistent repository guides. By prioritizing honesty and verifiability, it helps developers save time and reduce the frustration of navigating complex codebases blindly. The project is open source and welcomes contributions, with documentation available for architecture, API contracts, testing strategies, and architectural decisions.

Additional Information

LemonBeam is currently limited to public GitHub repositories and supports only JavaScript and TypeScript projects. It does not yet support private repositories, monorepos, or non-GitHub providers. Large repositories may have some evidence excluded due to token budgeting. The team plans to expand capabilities with stronger citation validation, better uncertainty summaries, support for larger repositories, broader language support, and private repository access. The project is built with React, TypeScript, Vite, Tailwind CSS, Node.js, Express, SQLite, Tree-sitter, the GitHub API, the OpenRouter API, and tiktoken for token management.