neuroguard-ai 0.1.0

AI-native code security review powered by Gemma 4 Thinking Mode

NeuroGuard

AI-native code security review powered by Gemma 4 Thinking Mode.

neuroguard-psi.vercel.app · github.com/tyy130/neuroguard

NeuroGuard reviews Python and JavaScript/TypeScript code for security vulnerabilities in real-time — streaming Gemma 4's full cognitive trace on the left while it produces a verified, secure rewrite on the right.

Built for the Dev.to Google Gemma 4 Challenge · Python · JavaScript · TypeScript

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The Problem

65% of AI-generated applications ship to production with critical security vulnerabilities, mirroring classic OWASP Top 10 flaws. The most dangerous failure mode is the hallucinated bypass: an AI agent deletes authentication checks to resolve a compilation error — silently stripping the application of its security infrastructure.

The root cause is opacity. When a black-box model generates insecure code, you can't see why it made that decision — and neither can the model.

The Solution

Gemma 4's <|think|> token turns the model into a glass box. Every reasoning step is visible, auditable, and inspectable before the final output is accepted. NeuroGuard wires this directly into a security workflow:

1. Feed it a Python file or directory
2. Gemma 4 streams its full cognitive trace — you watch it find each vulnerability in real-time
3. It produces a complete, secure rewrite grounded in that explicit reasoning
4. Bandit independently verifies the rewrite is clean

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Demo

The built-in demo file contains 5 intentional vulnerabilities:

• Hardcoded SECRET_KEY in source
• Unauthenticated admin routes (broken access control)
• SQL injection via f-string interpolation (×2)
• eval() on user input (remote code execution)
• Debug mode enabled in production

Before: 4 HIGH/MEDIUM Bandit findings
After:  ✓ CLEAN — Gemma 4's reasoning explains every fix

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Quickstart

pip install neuroguard
export GEMINI_API_KEY=your_key   # free at aistudio.google.com

neuroguard review app.py

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Installation

Requirements: Python 3.12+ · Free Google AI Studio API key · Node.js (optional, for JS/TS projects)

pip install neuroguard

Configure your API key (one-time):

export GEMINI_API_KEY=your_api_key_here

Or add to a .env file in your project root:

GEMINI_API_KEY=your_api_key_here

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Usage

# Review a single Python file
neuroguard review app.py

# Review a JavaScript or TypeScript file
neuroguard review server.js
neuroguard review api.ts

# Review an entire directory (Python + JS/TS)
neuroguard review src/

# Save the secure rewrite
neuroguard review app.py --save app_secure.py

# JSON output (for CI/CD pipelines)
neuroguard review app.py --format json

# Use the MoE model (faster, slightly lower quality)
neuroguard review app.py --model gemma-4-26b-a4b-it

# Skip Bandit SAST verification
neuroguard review app.py --no-sast

# Add as a pre-commit hook
neuroguard install-hooks

# Version
neuroguard --version

Exit codes:

• 0 — file is clean (no HIGH/MEDIUM findings in original)
• 1 — vulnerabilities found in original code

This makes it CI/CD friendly: your pipeline fails if a file with known vulnerabilities is committed without review.

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CI/CD Integration

GitHub Actions

Copy .github/workflows/neuroguard.yml into your repository. Add GEMINI_API_KEY to your repo secrets and NeuroGuard will run on every pull request that touches Python files.

Pre-commit Hook

neuroguard install-hooks
pre-commit install

Or manually add to .pre-commit-config.yaml:

repos:
  - repo: local
    hooks:
      - id: neuroguard
        name: NeuroGuard Security Review
        entry: neuroguard review
        language: python
        types: [python]
        pass_filenames: true
        require_serial: true

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JSON Output

neuroguard review app.py --format json | jq '.original_findings'

Schema:

{
  "file": "app.py",
  "model": "gemma-4-31b-it",
  "original_findings": 4,
  "rewrite_findings": [],
  "rewrite_valid_python": true,
  "thinking": "...",
  "response": "...",
  "secure_code": "..."
}

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Architecture

neuroguard/
├── cli.py             # Typer CLI — review, install-hooks, --version
├── agent.py           # Gemma 4 streaming client (google-genai SDK)
├── thinking_parser.py # Real-time <think>…</think> stream splitter
├── prompts.py         # Language-aware system prompt (activates Thinking Mode via <|think|>)
├── integrations.py    # Slack Block Kit, generic webhook, GitHub PR comments
├── tools/
│   ├── sast.py        # Bandit subprocess wrapper → Python findings
│   └── js_sast.py     # semgrep/regex SAST → JS/TS findings
└── ui.py              # Rich split-pane terminal layout

How Thinking Mode Works

The system prompt begins with <|think|>, which activates Gemma 4's Thinking Mode. The Google AI Studio API delivers reasoning content as thought=True parts in the stream — separate from the final response.

ThinkingStreamParser wraps all thinking chunks in a single <think>…</think> span and routes content to the appropriate pane in real-time, handling tags that split across chunk boundaries.

Models

Model	Type	Active Params	Notes
gemma-4-31b-it	Dense	31B	Default — highest quality
gemma-4-26b-a4b-it	MoE	~4B active / 26B total	Fallback — faster, lower cost

Retries on 429/503 with exponential backoff and automatically falls back to the MoE model on persistent rate limits.

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What NeuroGuard Catches

Vulnerability	OWASP	Python	JS/TS
SQL Injection	A03	✓	✓
Hardcoded secrets	A02	✓	✓
Missing authentication	A01	✓	✓
eval() / code injection	A03	✓	✓
Debug mode in production	A05	✓	✓
Insecure deserialization	A08	✓	—
Weak cryptography / Math.random()	A02	✓	✓
Path traversal	A01	✓	✓
XSS (innerHTML / dangerouslySet)	A03	—	✓
Command injection (exec)	A03	—	✓
Prototype pollution	A08	—	✓

NeuroGuard is a first-pass tool. It does not replace a full penetration test or human security review. Runtime behavior, business logic flaws, and infrastructure misconfigurations are out of scope.

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Why Gemma 4

Standard LLMs are black boxes for security review — you see the output but not the reasoning. Gemma 4's Thinking Mode changes this:

• Auditable: inspect the exact reasoning path before accepting any rewrite
• Trustworthy: the model can't silently delete auth checks if its reasoning is visible
• Compliance-ready: regulated industries can log and audit AI decision-making
• Open weight: Apache 2.0 license — run it air-gapped, no data leaves your infrastructure

This is the shift from vibe coding to AI-native development — treating AI output as an untrusted first draft, verified by both visible reasoning and automated SAST.

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License

Apache 2.0 — same as Gemma 4 itself.