Show HN: PromptSonar – Static analysis for LLM prompt security

1 point

3 months ago

I built PromptSonar because I kept seeing LLM security discussions focus entirely on runtime interception — but nobody was scanning the prompt strings written directly into source code before they ship.

PromptSonar is a static analyzer that scans your codebase for prompt injection, jailbreaks, PII leaks, and privilege escalation patterns in LLM prompt strings. It works across TypeScript, JavaScript, Python, Go, Rust, Java, and C#.

What it catches: - Direct prompt injection and jailbreak patterns - Unicode evasion: Cyrillic homoglyphs, zero-width character injection, Base64-encoded jailbreaks - PII exposure in prompts (SSN, credit card, API keys) - Privilege escalation and role manipulation - RAG poisoning patterns - Insecure output handling

Maps findings to OWASP LLM Top 10. Outputs SARIF v2.1.0 for GitHub Code Scanning integration. 100% local, zero telemetry, no API calls.

Available as VS Code extension, CLI, and GitHub Action.

npx @promptsonar/cli scan ./src

I wrote up the Unicode evasion detection methodology separately if anyone is interested in how the normalization pipeline works: https://medium.com/@meghal86/detecting-unicode-homoglyph-and...