See a feature in an app that you want in your own product? Give the app to your agent—even without its source code. With REA, the agent can investigate the feature, explain how it works, show its evidence, and build a version adapted to your stack and requirements.
REA gives agents one consistent way to investigate software. Today that includes deep native analysis through Hopper, complete function dossiers, reproducible Evidence v2 records, controlled process capture, passive website and Electron observation, and bounded JavaScript/source-map reconstruction. The longer-term toolkit extends the same agent workflow to APIs, protocols, mobile artifacts, firmware, richer runtime behavior, and differences between versions.
Reverse engineering normally makes the operator choose a tool, learn its API, move evidence between programs, and decide what to inspect next. REA gives that work to the agent through commands, skills, structured results, and repeatable investigation workflows.
Installing the CLI does not update Homebrew, Node.js, npm, Hopper, or agent configuration. `rea setup` detects what is already present, prints every proposed change, and asks before applying it.
REA detects Claude Code, Claude Desktop, Codex, Cursor, Gemini CLI, Windsurf, and Devin. Registrations are additive, backup-first, and read back after writing. You can safely rerun setup.
Pass installer options after `bash -s --`, for example `--dry-run`, `--no-setup`, or `--version 1.0.0`. The curl wrapper never installs prerequisites or configures integrations itself. See [Installation and setup](docs/installation.md) for its exact mutation boundary.
Ask your agent to set up REA. It will check your Mac, explain anything it needs to install, ask for approval, and guide you through system prompts. After setup, restart the agent if it asks you to load the full REA toolset.
Review the setup plan, approve it if appropriate, then describe the app or feature you want to understand. Hopper can run in its free demo mode; if it shows a first-run prompt, choose the demo or enter an existing license.
Deep binary analysis currently uses [Hopper](https://www.hopperapp.com/), a separate desktop application with its own license. Setup reuses an existing installation. If Hopper is missing, interactive setup proposes the official package and includes it in the confirmation plan. Unattended installation requires `rea setup --yes --install-hopper`.
`rea doctor --json` is read-only and distinguishes unsupported hosts, missing dependencies, a missing local analysis engine, configuration drift, and healthy checks. Paid-license activation is optional: on Linux, REA runs the supported Hopper demo build on a private Xvfb display and selects Hopper's offered demo mode for each analysis session.
On macOS, approved setup downloads Hopper's official DMG, verifies it, and installs the app into `~/Applications` without Homebrew or administrator privileges. Hopper may show its demo or license prompt when first opened; no manual drag-and-drop is required.
On Ubuntu 24.04+, Fedora 41+, and 64-bit Arch Linux, approved setup downloads the pinned official Hopper 6.4.2 package, restricts downloads to Hopper's public origin, verifies the published size and checksum, and invokes `apt-get`, `dnf`, or `pacman` to install Hopper and the Xvfb, Python, X11, and XTEST packages used by demo sessions. When REA is not already running as root, `pkexec` presents the system authorization prompt. REA never invokes `sudo`. Demo sessions run on an isolated 1280×1024 Xvfb display. REA verifies the exact supported Hopper binary, its owned process ancestry, the expected dialog geometry, and bridge state before selecting `Try the Demo`; any mismatch fails closed.
Install the missing distribution packages and rerun `rea setup`. Linux demo automation requires `Xvfb`, Python 3, `libX11.so.6`, and `libXtst.so.6`; approved setup installs those direct runtime dependencies and does not interact with the user's desktop display. Hopper's free demo supports analysis with vendor-defined limits, and a paid license is optional. The curl installer places the `rea` command in `~/.local/bin` on Linux; add that directory to future shell `PATH` values if it is not already present.
REA defaults `HOPPER_LAUNCHER_PATH` to `/Applications/Hopper Disassembler.app/Contents/MacOS/hopper` on macOS and `/opt/hopper/bin/Hopper` on Linux. Explicit configuration always takes precedence.
To remove only REA-owned MCP registrations and the managed skill:
```bash
rea uninstall
rea uninstall --purge-data # also removes only ~/.rea/cache and ~/.rea/state
Uninstall preserves Hopper, Node.js, evidence, captures, external evidence roots, unrelated skills, and other MCP servers. It refuses malformed client configuration and never follows purge-data symlinks.
Exports never replace an existing file unless `--overwrite` is explicit. Imports are size/depth bounded, validate every Evidence v2 ID and manifest, and never execute bundle content.
The public interface describes what the agent is trying to learn. Providers decide how to answer. macOS utilities handle common semantic inspection without launching Hopper; Hopper handles deeper native analysis; the process harness implements controlled behavioral capture.
- Attach to a user-owned Chrome-family browser over a configured loopback CDP endpoint; capture exact-origin web structure, safe metadata, approved value-free payload shapes, bundle/source-map evidence, WebMCP declarations, user-action timelines, capture diffs, and explicitly approved screenshots without navigation or JavaScript evaluation.
- Inspect Electron `file://` renderer pages through a separate canonical-root permission boundary without invoking Electron APIs; script contents remain separately approved and byte bounded.
- Capture approved PTY scenarios as Process Capture v4 Evidence, including committed run manifests, raw and rendered terminal frames, scripted interactions, descendant settlement, named filesystem checkpoints, deterministic command shims, and loopback HTTP/WebSocket exchanges.
- Compare complete artifact inventories by stable path, content, metadata, and relations; incomplete evidence never implies equivalence.
- Compare explicit function dossiers across text, calls, references, strings, and address-normalized CFG topology with per-facet unknowns.
- Compare canonical Evidence bundles by exact membership, explicit observation pairs, and residual-unknown histories without turning omissions into behavioral absence.
- Aggregate runtime comparisons into observed behavior changes while keeping static artifact/function differences labeled as candidates.
- Build bounded, Evidence-cited direct call paths by exact address without treating missing dossiers as graph leaves.
- Correlate exact static/runtime findings through explicit hypotheses without claiming causality from cochange.
- Verify finite behavioral and structural reconstruction specifications with pass, fail, and unknown kept distinct.
- Track residual unknowns through immutable CAS revisions, evidence-qualified resolution, contradictions, probes, and validated dependency relationships.
- With explicit `unknown_registry_approved: true`, record bounded trace/capture residuals, typed provider unavailability, and capture disagreements automatically.
- Start six [guided MCP workflows](docs/mcp-prompts.md) with live, session-aware completion for documents, procedures, providers, evidence, captures, artifact IDs, and active unknowns.
Hopper is the first provider, not the boundary of the project. Some current workflows still require Hopper and macOS; every evidence record identifies the provider and limitations behind its result.
REA can inspect an already-running Chrome-family browser that you own. Browser observation is disabled by default and requires a literal loopback CDP endpoint plus exact approved page origins:
All eight browser tools expose the same Evidence v2 contracts over CLI and MCP. Inspection is passive: REA does not evaluate page JavaScript, navigate, click, close the page, or close the browser. Query values, credentials, cookies, authorization headers, storage values, and raw JSON or WebSocket values are never retained. Separately approved captures can retain bounded redacted console primitives, value-free JSON/WebSocket shapes, script sources, accessibility text, or screenshot pixels. Existing activity before attach is explicitly unavailable. See [Website observation with CDP](docs/browser-observation.md) for browser startup, schemas, limits, and the threat model.
2.**Web and Electron investigation** — extend the shipped passive CDP, bundle, visual-diff, and file-page observation with approved interaction, controlled replay, Electron IPC observation, semantic UI differences, and deeper JavaScript reconstruction.
4.**JavaScript and source recovery** — bundle indexing, AST/module reconstruction, source-map discovery, historical-source matching, and CodeDB-backed cross-references.
5.**Runtime observation** — approval-gated LLDB, Frida, system logs, process and filesystem observers, and native API tracing.
6.**More static-analysis providers** — native platform utilities first, followed by Ghidra, IDA/Hex-Rays, Binary Ninja, Rizin, LIEF, and other engines behind provider-neutral capabilities.
7.**More targets and platforms** — Windows-native providers and ConPTY verification, Linux parity, websites and APIs, mobile artifacts, firmware, document formats, and other software-defined systems.
Roadmap items describe direction, not shipped support. New providers must produce the same evidence and safety metadata as existing capabilities before they become part of the public workflow. Once REA has multiple optional toolchains, setup can become capability-selective; the consent rules for that future work are recorded in the [installation roadmap](docs/roadmap.md).
Setup currently configures Claude Desktop and Cursor automatically. Any agent that supports local MCP servers can use REA with the configuration below.
The CLI and MCP server use the same application workflows and evidence contracts. A provider declares which capabilities it supports and the side effects those capabilities may have. Terminal commands are short-lived; an MCP session can retain an active target and evidence ledger across an investigation. Approved persistent workspaces keep canonical Evidence and resumable run checkpoints across both process and session lifetimes.
REA starts Hopper when needed; Hopper does not need to be running first. Hopper's launcher internally activates the application, so opening a target may bring Hopper to the foreground. REA asks macOS to start Hopper hidden and in the background when possible, but cannot guarantee that it will remain behind the current application.
REA derives explicit format and architecture arguments to prevent common FAT and ARM selection dialogs. Other Hopper or macOS dialogs may still require a person. REA reports timeouts and remediation through CLI or MCP results instead of attempting to answer UI prompts.
REA does not provide a hosted analysis service. Hopper communication uses an authenticated private local socket. Dynamic capabilities are disabled by default and require both operator policy and explicit per-call approval. REA is not a security sandbox: providers and launched targets run with the current user's permissions, and each capability reports its side effects and limitations. Report vulnerabilities through the private process in [SECURITY.md](SECURITY.md).
Hopper's launcher internally activates the application. REA requests background startup, but macOS and Hopper may still bring a window or dialog forward. See [Hopper application behavior](#hopper-application-behavior).
No. Setup can install Hopper for you, but Hopper remains separate software with its own license. REA supplies the CLI, MCP server, and workflows that make it usable by agents.
REA has no hosted analysis service. Current providers analyze artifacts and capture behavior locally. Your agent or model provider may have its own data policy, so review that separately.
<summary><strong>Can REA recover the original source code?</strong></summary>
No decompiler can guarantee the original source. REA gives an agent pseudocode, assembly, symbols, strings, metadata, and relationships that it can use to explain or compatibly recreate observed behavior.
</details>
<details>
<summary><strong>Which agents can use REA?</strong></summary>
Any agent that can run a local MCP server can use the manual configuration. Setup currently detects and configures Claude Desktop and Cursor automatically.
See [CONTRIBUTING.md](CONTRIBUTING.md) for setup, architecture, tests, and release instructions. Generated API documentation is available under [`docs/api`](docs/api/index.html).
