# How to learn how a feature in another app works with rea

Repo: [morluto/rea](https://github.com/morluto/rea) | Difficulty: Intermediate | Time: 45 minutes | Basis: Seen in the wild

Point your agent at an installed app and get an explanation of one feature, with the evidence behind it.

**Who it is for:** Indie developer who likes a feature in a desktop app and wants to understand how it is built

**The problem:** The app has no public source code, so you cannot tell how the feature is put together.

**The outcome:** A written explanation of how the feature works, with the evidence listed and unknowns flagged.

## Steps

1. Run npx rea-agents setup, pick your agent, approve the changes, then restart the agent.
2. Ask your agent to investigate one specific feature in the target app using REA.
3. Ask it to show the evidence for each claim and mark anything it is guessing.
4. Read the explanation and ask follow-up questions about the parts you will reuse.

## Prompt to paste into your agent

```text
Use REA to work out how <feature> works in <app> at <path>. Show the evidence, flag what you are guessing, and summarize the design in plain words. Verify every claim points to a file, symbol or observed behavior.
```

## Caveat

Only analyze software you own or are licensed to inspect, and check the app's license terms. REA can only infer backend logic from what the client exposes.

## Seen in the wild

- X (Oct 2026): https://x.com/i/web/status/2112187888741822588
- Reddit: https://www.reddit.com/r/singularity/comments/1x2rrsi/reverse_engineer_anything_is_a_great_toolkit_what/

Dual-use notice: only use this on software, sites and systems you own or are authorized to test.

Disclaimer: Third-party repos we don't own or vouch for. AI-generated use cases can be wrong: review everything and run at your own risk. Full text: https://dedupedai.com/disclaimer/

URL: https://dedupedai.com/use-cases/morluto-rea/learn-how-app-feature-works/