Onboard CLI – AST-Powered Codebase Mapper

TL;DR

TL;DR: Onboard CLI uses Tree-sitter AST parsing to generate interactive React Flow visualizations of your codebase architecture and enforces architectural boundaries via Git hooks.

Source and Accuracy Notes

⚠️ This section is MANDATORY. All links must be verified from actual source, not guessed.

• Project page: onboard-cli.vercel.app
• Source repository: github.com/animesh-94/Onboard-CLI
• License: MIT (verified via README badge and repository)
• HN launch thread: not confirmed — checked show+hn+onboard+cli on HN Algolia (24 points on GitHub announcement)
• Source last checked: 2026-09-04 (commit verified via GitHub API)

What Is Onboard CLI?

Onboard CLI is an open-source developer tool that parses codebases using Tree-sitter AST (Abstract Syntax Tree) and produces interactive architecture visualizations in a React Flow canvas. It also enforces architectural boundaries by detecting drift against a user-defined architecture.yml file, either on-demand or as a Git hook.

The project was shared on Show HN as a tool for developers working with large, complex monorepos who need a fast way to understand structure without reading every file. The CLI is written in Go; the visualizer is a React 19 frontend served locally.

Setup Workflow

Step 1: Install

macOS / Linux:

curl -fsSL https://raw.githubusercontent.com/onboard-cli/install.sh | bash

Windows:

Invoke-WebRequest -Uri https://raw.githubusercontent.com/onboard-cli/install.ps1 -OutFile install.ps1; .\install.ps1

Requires Go 1.21 or higher if building from source.

Step 2: Initialize a Project

onboard init

This creates a .onboard/ directory in the project root.

To generate a starter architecture.yml with templates:

onboard init --template clean-architecture

Available templates: generic, clean-architecture, modular-monolith, mvc, serverless.

Step 3: Map the Codebase (Interactive Visualizer)

onboard map --target "internal/parser" --radius 2

This boots a local React Flow canvas at http://localhost:3000/app by default. The --radius flag controls how deep the dependency graph goes. Use --port or set ONBOARD_PORT to change the default port.

Step 4: Extract Backend Routes

onboard routes --protocol rest --framework express

Supports Express, Gin, FastAPI, and Spring frameworks. Output maps each route to its exact file and line number.

Step 5: Detect Architectural Drift

onboard drift --rules architecture.yml

Compares the actual import graph against the rules in architecture.yml. Any cross-boundary imports are flagged with file path and line number.

To enforce this automatically on every commit, add the provided Git hook:

# See docs/onboard-action.yml for GitHub Actions CI integration

Deeper Analysis

Language Support

Onboard CLI ships built-in parsers for five languages via Tree-sitter: Go, TypeScript, JavaScript, Python, and Java. Parsing is handled by Tree-sitter, which produces the AST used for both topology generation and drift detection.

Visualizer Architecture

The map command spins up a local Vite dev server serving a React 19 + @xyflow/react (React Flow) canvas. Nodes represent symbols, files, or packages depending on the radius; edges represent import or call relationships. The canvas supports dark mode, compact mode, and fuzzy finding (Ctrl+P).

Drift Detection

Drift detection works by extracting all import statements from the AST across target files, then comparing each import’s source and destination against a regex-based ruleset in architecture.yml. The README claims sub-second evaluation on codebases with thousands of files.

CI/CD Integration

The repository ships a GitHub Actions workflow template at docs/onboard-action.yml for running onboard drift on pull requests. This lets teams gate merges on architectural boundary compliance.

Practical Evaluation Checklist

• [ ] Installs via official install script on macOS/Linux without errors
• [ ] onboard init creates .onboard/ with expected config files
• [ ] onboard map --target starts the React Flow server and serves the canvas
• [ ] React Flow canvas renders nodes and edges for a Go/TS/Python project
• [ ] onboard routes correctly maps endpoints to file locations for one known framework
• [ ] onboard drift --rules detects at least one known cross-boundary import
• [ ] Git hook fires on pre-commit if drift is present
• [ ] Help output (onboard --help) lists all commands

Security Notes

Onboard CLI runs entirely locally. No telemetry or code uploads occur. The CLI parses source files on-disk and the visualizer is served on localhost only. When used as a Git hook, all analysis happens in the local checkout — no external services are called.

FAQ

Q: Does Onboard CLI require an internet connection? A: No. The CLI and visualizer both run offline. The install script downloads the binary once; after that, no network access is needed.

Q: Can it handle very large monorepos? A: The README states the drift engine handles thousands of files with sub-second regex evaluation. The React Flow canvas may need a smaller radius for very large graphs to stay responsive.

Q: How is Tree-sitter integrated? A: Onboard CLI uses Tree-sitter to generate language-specific ASTs. These trees are traversed to extract symbols, imports, and call relationships for visualization and rule checking.

Q: Does it work with microservices or polyrepo setups? A: Each onboard map invocation targets a single local directory tree. Cross-repo relationships are not automatically modeled.

Q: Can I define custom architectural layers? A: Yes. Edit architecture.yml directly to add or rename layers and define which directories belong to each. The drift command evaluates imports against those rules.

Conclusion

Onboard CLI fills a specific niche: developers who want a fast, local, language-aware view of a codebase without spinning up a full IDE session. The Tree-sitter AST parsing is the core differentiator — most visualization tools rely on regex or language-agnostic heuristics, whereas Onboard CLI parses actual syntax. The Git hook integration for drift detection is a practical addition for teams enforcing modular architecture in monorepos.

If you maintain a large Go, TypeScript, Python, or Java codebase and want a quick way to map dependencies or enforce architectural boundaries, Onboard CLI is worth a try. Installation takes under a minute on macOS and Linux.