Pysa vs Skylos

Pysa is a free, open-source Python static analysis tool that uses taint analysis to identify potential security issues. It follows data from configured sources toward dangerous sinks, such as user-controlled request data reaching an eval call. Users configure sources, sinks, features and rules in taint.config, and annotate code with .pysa model files; built-in and common Python libraries have prewritten models and rules. Sanitizer models describe data that should lose taint, including function parameters and return values. Pysa analyzes the target repository and directories in the configured search_path, but not dependency source outside that scope. When it cannot access a function’s source, it assumes the return value retains taint, which can lead to false positives. Analysis may freeze on similarly sized projects if the machine lacks enough memory. The quickstart installs it with pip install pyre-check in a Python virtual environment. Pyre supports the Language Server Protocol, and a VSCode extension connects to a running server. SAPP can ingest results for viewing and filtering in a local web UI; a GitHub Action can run Pysa in CI and show findings in GitHub’s Security code scanning UI. Pysa requires Python 3.9 or later and relies on type information from Pyrefly. The project says it can analyze codebases with millions of lines. Its repository is MIT-licensed; the Pyre repository was archived on June 26, 2026, and says Pysa moved to its own repository.

Skylos is an open-source static analysis tool that checks source code for security regressions, secrets, dead code, quality issues, and mistakes introduced by AI. It analyzes Python, JavaScript and TypeScript, Go, Java, Kotlin, PHP, Rust, Dart, C#, Shell, and deployment configuration, with analysis depth differing by language. Its CLI runs locally without an account for scans and CI checks. A free VS Code extension offers inline diagnostics and optional AI verification through OpenAI or Anthropic API keys. Cloud options include GitHub pull request workflows, OIDC identity, and optional Slack and Discord notifications. A normal CLI scan remains on the user's machine; Cloud receives data when reports are uploaded, cloud actions are triggered, or the public scan endpoint is used. Uploaded reports may include findings, file paths, snippets, and scan metadata. Skylos says it does not currently claim SOC 2, ISO 27001, or CSA STAR certification. The free plan includes one cloud project, 10 stored scans, and seven-day history. One-time credit packs begin at 9.00 USD. Skylos supports API, extension, Linux, macOS, self-hosted, web, and Windows use.