Introduction to Stacy Static Analyzer

Smart contracts are powerful, but once deployed, they’re permanent. That means any bugs or vulnerabilities can lead to major consequences. As someone working on Clarity smart contracts for the Stacks blockchain, I recently rewrote the tokenomics in one of my contracts. To ensure it was secure, I used Stacy, a static analysis tool built specifically for Clarity.

In this article, I’ll walk you through what static analysis is, why it matters, and how Stacy works and helped me catch potential issues before they became problems.

What is Static Analysis?

Static analysis is the process of examining your code without running it. Unlike testing or debugging, which requires code execution, static analysis reads the source code and identifies potential problems just by looking at the structure and logic.

Think of it like proofreading a document before submitting it, you're making sure everything looks right, even before you try it out.

Definition and Purpose

The primary goal of static analysis is to:

✅ Catch bugs early in development
✅ Enforce coding standards and best practices
✅ Improve readability and maintainability
✅ Prevent security vulnerabilities

In the context of smart contracts (especially on blockchains like Stacks), these goals become even more important because once a smart contract is deployed to the blockchain, it becomes immutable, meaning it cannot be changed or updated directly. Any changes require deploying a new contract and potentially migrating users and data, which can be complex and risky.

Static vs. Dynamic Analysis

Feature	Static Analysis	Dynamic Analysis
Code Execution	❌ Not required	✅ Requires running the code
When It Happens	During development	During or after execution
What It Detects	Syntax issues, logic flaws	Runtime errors, performance issues
Speed	Fast	Slower, especially with tests
Tool Examples	Stacy, ESLint, Slither	Debuggers, Unit Test Frameworks

Static analysis is ideal before deployment to ensure code quality and security, while dynamic analysis is used to find bugs that only appear when the program runs.

Benefits of Static Analysis for Smart Contracts

Smart contracts are immutable, meaning once deployed, they can't be edited or fixed. That makes early error detection absolutely critical.

Here’s why static analysis is valuable for smart contract developers:

🛡️ Improves security by finding vulnerabilities early
🔍 Highlights dead code, unused variables, or weak logic
📏 Enforces best practices across your codebase
🚫 Prevents costly mistakes before going on-chain
🧪 Simplifies auditing, especially for large contracts

What is Stacy?

Stacy (Stacks Static Analyzer for Clarity) is an open-source tool created by CoinFabrik, a Web3-focused R&D company. Stacy scans Clarity smart contracts and detects:

Security risks
Logic errors
Outdated patterns
Poor coding practices

It’s designed for developers and auditors who want to build robust, secure contracts on the Stacks blockchain.

How to Install Stacy

Stacy is a Python-based tool. You can install it with the following commands:

pip install git+https://github.com/xlittlerag/tree-sitter-clarity@6eb27feb
pip install stacy-analyzer

Make sure you have Python and pip installed before running these commands.

How to Use Stacy

Once installed, you can run Stacy on your smart contract files using:

stacy-analyzer lint tests

This will recursively search for .clar files inside the tests directory (or any other directory you specify) and analyze them for issues. Stacy will report all detected vulnerabilities, warnings, and enhancements.

What Stacy Detects

Stacy uses detectors to find known issues in Clarity code. Here are some examples of what it looks for:

DETECTOR ID	WHAT IT DETECTS	SEVERITY
`assert-block-height`	Using `block-height` as a time tracker	Critical
`call-inside-as-contract`	Loss of context when calling another contract	Critical
`divide-before-multiply`	Precision loss due to operation order	Critical
`tx-sender-in-assert`	Risky usage of `tx-sender` in `assert`	High
`todo-comment`	Leftover TODO comments	Enhancement
`private-function-not-used`	Dead private functions (unused code)	Enhancement
`unused-arguments`	Function arguments that are passed but never used	Enhancement
`var-could-be-constant`	Variables that could be replaced with constants	Enhancement

Severity is based on worst-case scenarios, so developers should review each finding in context.

Who built Stacy?

Stacy was developed by CoinFabrik, a well-known Web3 company with deep experience in cybersecurity and blockchain development. Since 2014, they've worked on over 180 blockchain projects across ecosystems like Ethereum, Solana, Algorand, Polkadot, and Stacks.

They also maintain active academic collaborations and open-source contributions, which gives Stacy a strong technical foundation.

Final Thoughts

If you’re building smart contracts in Clarity, Stacy is an essential tool in your development toolkit. It’s fast, lightweight, and beginner-friendly.

I highly recommend running Stacy as part of your contract development workflow to:

Catch security flaws
Improve your code quality
Build smarter and safer on Stacks

🛡️ How to Use Stacy to Analyze and Secure Your Clarity Smart Contracts