Understanding an application’s behavior and building a similar feature are separate steps. REA supplies inspection tools to a coding agent, while DeepSeek Harness is an agent environment extended with plugins. Start by deciding what evidence you need.
What can REA inspect?
Its repository describes workflows for JavaScript and Electron applications, websites, .NET assemblies and native binaries. An agent can call the tools through MCP, and the same workflows are available from the command line. Review the evidence and limitations behind each finding.
For example, inspection of an extracted Electron app can identify modules and their relationships. Deeper native analysis may need a separate provider such as Hopper, Ghidra, IDA or Kuna, depending on the target. Different targets do not yield the same level of detail.
Where does Harness fit?
DeepSeek describes Harness as an open-source agent environment built around plugins. Its repository calls it a developer preview and warns that compatibility-breaking changes will occur. Treat the agent environment, analysis tool and model access as separate components; availability of one does not mean the others are unlimited or free.
A controlled first inspection
Choose a small target you are authorised to inspect and ask a specific question. Review proposed setup changes and prerequisites, then check the evidence behind the findings. The REA repository says static JavaScript inspection can read supplied files without running the app; runtime capture can interact with the target using your user permissions.
Even when analysis is local, results passed to an agent may reach its model provider, whose data policy applies. Test any resulting implementation separately for the intended behavior, data handling and failure cases.
