Batou - Runtime SAST For Claude Code

A security scanner that catches vulnerabilities in real-time as AI writes code. Built as a Claude Code hook, Batou analyzes every file write across 17 languages using regex, AST, taint analysis, and interprocedural call graph tracking.

High-confidence findings (confirmed by multiple layers) block the write. Lower-confidence findings produce hints — Claude sees the advice without being interrupted by false positives.

How It Works

Claude writes code → Batou intercepts → 4-layer scan → Confidence scoring → Block / Hint

Layer	What	How
1. Regex	Pattern rules across 45 categories	Fast pattern matching for known vulnerability signatures
2. AST	Tree-sitter structural parsing	Suppresses false positives in comments, structural analysis
3. Taint	Source-to-sink dataflow tracking	Tracks user input through variables to dangerous functions
4. Call Graph	Interprocedural analysis across files	Persistent cross-function taint tracking within a session

Parsed trees and taint flows are shared across layers — each file is parsed once.

Findings confirmed by multiple layers block the write. Single-layer regex matches produce hints instead — Claude sees the advice without being interrupted by false positives.

Installation

Homebrew (recommended)

brew install turenlabs/tap/batou && batou-setup

This installs the binary and configures Claude Code hooks automatically.

To update:

brew upgrade batou

Install script

# Quick install (downloads binary + configures hooks globally)
curl -fsSL https://raw.githubusercontent.com/turenlabs/batou/main/install.sh | bash

# Install + configure hooks for a specific project
curl -fsSL https://raw.githubusercontent.com/turenlabs/batou/main/install.sh | bash -s -- --setup /path/to/project

# Or install + configure hooks globally
curl -fsSL https://raw.githubusercontent.com/turenlabs/batou/main/install.sh | bash -s -- --global

Build from source

# Requires Go 1.21+, CGo, gcc/clang
git clone https://github.com/turenlabs/batou.git && cd batou && make build && make install

What It Detects

Injection, XSS, path traversal, crypto weaknesses, hardcoded secrets, SSRF, auth issues, XXE, deserialization, CORS, SSTI, JWT flaws, session issues, file upload, race conditions, log injection, input validation, memory safety, and framework-specific misconfigs (Spring, Express, Django, Flask, Rails, Laravel, React, Tauri).

Languages: Go, Python, JavaScript/TypeScript, Java, PHP, Ruby, C, C++, Kotlin, Swift, Rust, C#, Perl, Lua, Groovy, Zig

False Positive Suppression

Suppress findings with inline directives when you know the code is safe:

// batou:ignore BATOU-INJ-001 -- query uses parameterized input
db.Query("SELECT * FROM users WHERE id = " + id)

# batou:ignore secrets -- test fixture, not a real credential
password = "test-password-for-ci"

Block suppression for multiple lines:

// batou:ignore-start injection
rows := db.Query(dynamicSQL)
process(rows)
// batou:ignore-end

Targets: specific rule ID (BATOU-INJ-001), category (injection), or all. Always include a reason after --.

Adding Batou to Your Project's CLAUDE.md

Copy the snippet from docs/claude-md-snippet.md into your project's CLAUDE.md so Claude understands how Batou works and can respond to its findings correctly.

Testing

make test          # Run all tests with race detector
make test-cover    # Run with coverage

License

MIT