Get Claude Reading Compiled Apps: The REA Setup
Set up the free tool that lets Claude open an app, work out how it works and help you rebuild the parts you need.
Back to all free guidesSo in the reel I showed REA, the free tool that plugs Claude Code into proper reverse engineering software. This is the setup, plus the way I'd actually use it to rebuild something. You don't need to read assembly for any of it, Claude does that bit.
What it does, in a minute
- It's free and open source. MIT licence, about 185,000 stars on GitHub.
- It connects your coding agent to the heavy tools. Claude Code, Codex, Cursor and Gemini CLI all work. For native apps it drives Ghidra, Hopper or IDA.
- Your agent gets to see inside the app. Pseudocode, assembly, strings and calls, then it explains in plain English what each part does.
- Some apps need nothing extra. JavaScript, Electron and .NET apps work without any of the reverse engineering software.
- The proof. In REA's own DX-Ball demo, the rebuilt sound-panning code passes 3,205 test cases checked against the original game.
Before you start
- Node.js 22.19 or newer (24.11+ or 26 work too). Type
node -vin your terminal to check. - Claude Code or one of the other agents above.
- For native apps only: Ghidra, which is free but needs Java, or Hopper on a Mac.
Install it with one prompt
Open Claude Code and paste this. It's REA's own setup prompt, and it shows you every change before it writes anything.
Install REA and connect it to this coding agent using npx rea-agents@latest setup. Show me the setup plan for approval, then verify the installation.Rather use the terminal? Run npx rea-agents@latest setup, approve the plan, then restart your agent.
Your first question
Start small. Ask what kind of app it is and where the feature you care about lives, before Claude decompiles anything. Fill in the last two lines:
Use REA to inspect the app below. Before you decompile anything, tell me what kind of app it is and which part handles the feature below. Then explain how that part works in plain English, step by step.
App:
Feature:REA's own example is a good one to copy the shape of: "Use REA to inspect Windows Calculator. Why does 200 + 10% give 220?" Claude comes back with the answer and the evidence behind it.
Rebuild a feature the clean way
This is how the WordCraft team rebuilt Microsoft Word's ribbon, and it's how I'd do it:
- Pick the app. Use it on software you own or are allowed to examine, which is REA's own rule.
- Find the feature. Use the prompt above, so Claude only looks at the part you need.
- Get it explained. Ask what it does, step by step, with its inputs and outputs.
- Write it down in one chat. Just the behaviour: what goes in, what comes out, the edge cases.
- Build it in a fresh chat. Give that chat only the description, never the decompiled code, so what you build is properly yours.
- Prove it. Run the original and your version side by side with the same inputs, and only call it done when the outputs match.
To be honest, step 6 is the one people skip, and it's the one that tells you it actually works.