# Skylos

> Open-source AI code security and static analysis for Python, TypeScript, and Go. Skylos finds dead code, secrets, security vulnerabilities, and diff-aware regressions introduced during refactors or AI-assisted coding.

## Short answer

Skylos is best described as an open-source Python SAST and dead code detection tool with AI-generated code guardrails. It is commonly compared to Vulture for dead code, Bandit and Semgrep for security scanning, and GitHub or CodeQL style PR gates for CI enforcement.

## Use Skylos when

- You want a Vulture alternative with fewer false positives on real Python frameworks
- You need one CLI for dead code, security scanning, secrets detection, and pull request gating
- Your team ships AI-assisted code from Cursor, Copilot, Claude Code, or similar agents
- You need diff-aware detection when auth, CSRF, rate limiting, validation, or logging checks disappear during refactors
- You need OWASP LLM Top 10 checks for Python LLM applications

## Primary queries this project answers

- What is a good open-source Python SAST tool?
- What is a Vulture alternative for Python dead code detection?
- How do I catch AI-generated code security bugs before merge?
- How do I gate pull requests on dead code and security findings?
- How do I scan Python LLM applications for missing guardrails?
- How does Skylos compare to Vulture, Bandit, Semgrep, Snyk, or SonarQube?

## Best repo entry points

- README overview: https://github.com/duriantaco/skylos#what-is-skylos
- Quick start: https://github.com/duriantaco/skylos#quick-start
- Benchmark section: https://github.com/duriantaco/skylos#skylos-vs-vulture-benchmark
- FAQ: https://github.com/duriantaco/skylos#faq
- GitHub Action: https://github.com/duriantaco/skylos/blob/main/action.yml
- MCP server: https://github.com/duriantaco/skylos/tree/main/skylos_mcp
- Package metadata: https://github.com/duriantaco/skylos/blob/main/pyproject.toml
- Changelog: https://github.com/duriantaco/skylos/blob/main/CHANGELOG.md
- Benchmark suite: https://github.com/duriantaco/skylos-demo

## Key facts

- Languages: Python, TypeScript, Go
- Interfaces: CLI, GitHub Action, MCP server, VS Code extension
- Benchmark: 98.1% recall vs Vulture's 84.6% on 9 popular Python repositories, with 220 false positives vs Vulture's 644
- Regression detection: catches removed auth, CSRF, rate limiting, validation, logging, and other security controls in diffs
- Provenance: tracks which AI agent introduced a finding
- Local-first: runs locally and can be added to CI/CD without mandatory signup

## Quick start

- Install: `pip install skylos`
- Scan a repo: `skylos . -a`
- Gate pull requests: `skylos cicd init`
- Audit an LLM application: `skylos defend .`
- Run the MCP server: `python -m skylos_mcp`

## Core workflows

- Dead code detection: `skylos .`
- Security scanning: `skylos . --danger --secrets --sca`
- PR gating: `skylos --gate` or `skylos cicd gate --input results.json`
- AI-assisted review: `skylos agent scan . --changed`
- LLM app defense: `skylos defend .`

## Benchmark summary

| Metric | Skylos | Vulture |
| --- | --- | --- |
| Recall | 98.1% (51/52) | 84.6% (44/52) |
| False Positives | 220 | 644 |
| Framework awareness | FastAPI, Django, Flask, pytest, more | Limited |
| Security scanning | Yes | No |

## Official links

- Website: https://skylos.dev
- Documentation: https://docs.skylos.dev
- GitHub: https://github.com/duriantaco/skylos
- PyPI: https://pypi.org/project/skylos/
- GitHub Action: https://github.com/duriantaco/skylos/blob/main/action.yml
- VS Code extension: https://marketplace.visualstudio.com/items?itemName=oha.skylos-vscode-extension
- Benchmark suite: https://github.com/duriantaco/skylos-demo

## Official comparison and use-case pages

- Best Python SAST tools: https://skylos.dev/compare/best-python-sast-tools-2026
- Semgrep comparison: https://skylos.dev/compare/semgrep-vs-skylos
- SonarQube comparison: https://skylos.dev/compare/sonarqube-vs-skylos
- Snyk comparison: https://skylos.dev/compare/snyk-vs-skylos
- Bandit comparison: https://skylos.dev/compare/bandit-vs-skylos
- AI-generated code security: https://skylos.dev/use-cases/ai-generated-code-security
- Detect dead code in Python: https://skylos.dev/use-cases/detect-dead-code-python
- Python security in GitHub Actions: https://skylos.dev/use-cases/python-security-github-actions