jadx-headless-mcp

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Headless MCP server for Android APK static analysis, built directly on jadx-core. No JADX GUI required, no Python adapter, no plugin to install — just one JVM process speaking MCP over stdio.

Why

jadx is two parts: the jadx-core decompiler engine, and a GUI wrapped around it for a human to click through by hand.

Give a capable LLM direct access to jadx-core and the GUI loses its reason to exist. The model walks the same class tree, resolves the same xrefs, reads the same source — headless and scriptable. As models get stronger, Java-layer reverse engineering increasingly runs end to end from the model, without a reverse engineer driving it by hand.

So this server drops the GUI and exposes jadx-core as ~26 MCP tools over stdio.

Tools

Session management

Static analysis (require a loaded APK)

Build

Requires JDK 17+.

./gradlew installDist

Output: build/install/jadx-headless-mcp/bin/jadx-headless-mcp (and .bat on Windows).

For a single portable fat jar:

./gradlew shadowJar
# build/libs/jadx-headless-mcp--all.jar

No build needed? Prebuilt artifacts (fat jar + distribution zip) are attached to every GitHub Release — download one and point your MCP config at it directly.

Run

Empty start (load an APK later via load_apk tool):

./build/install/jadx-headless-mcp/bin/jadx-headless-mcp

Or eager-load on startup:

./build/install/jadx-headless-mcp/bin/jadx-headless-mcp \
  --apk /path/to/app.apk \
  --max-source-bytes 200000

The server speaks MCP over stdio. Logs go to stderr.

Install as a Claude Code plugin

This repo is also a Claude Code plugin — the easiest way to install for Claude Code, no JSON editing and no manual build. It needs JDK 17+ on PATH; on first start it downloads the released fat jar (SHA-256 verified) and caches it.

/plugin marketplace add 1013503897/jadx-headless-mcp
/plugin install jadx-headless@jadx-headless-mcp

This bundles the MCP server plus the /jadx-headless:open-apk skill. See PLUGIN.md for how it works, local development (claude --plugin-dir .), releasing, and community-marketplace submission. If you’d rather wire the server up by hand (or use another client), use the manual configuration below.

MCP client configuration

jadx-headless is a standard stdio MCP server, so any MCP-capable client can drive it — Claude Code, Claude Desktop, Cursor, Windsurf, Cline, Roo Code, VS Code / Copilot, LM Studio, Zed, Codex, Gemini CLI, and others. Claude Code has the smoothest path; the rest take one small config entry — see Other MCP clients.

Claude Code

Quickest: register with the CLI

One command, no JSON editing. -s user writes to the global ~/.claude.json; the default local scope only applies to the current project:

# installDist launcher
claude mcp add jadx-headless -s user -- C:/tools/jadx-headless-mcp/bin/jadx-headless-mcp.bat

# ...or the portable fat jar (single file; needs java on PATH)
claude mcp add jadx-headless -s user -- java -jar C:/tools/jadx-headless-mcp--all.jar

Then ask the AI to call load_apk with the path you want to analyze. Use unload_apk to free memory or switch to a different one — no config edit needed.

Or edit the config by hand

Register one entry, swap APKs at runtime:

{
  "mcpServers": {
    "jadx-headless": {
      "command": "C:/tools/jadx-headless-mcp/bin/jadx-headless-mcp.bat"
    }
  }
}

To point at the portable fat jar instead:

{
  "mcpServers": {
    "jadx-headless": {
      "command": "java",
      "args": ["-jar", "C:/tools/jadx-headless-mcp--all.jar"]
    }
  }
}

If you only ever analyze a single APK and want it ready immediately, append the APK path via args:

{
  "mcpServers": {
    "jadx-headless": {
      "command": "C:/tools/jadx-headless-mcp/bin/jadx-headless-mcp.bat",
      "args": ["--apk", "C:/work/current.apk"]
    }
  }
}

Note: java -jar skips the launcher’s default JVM args (e.g. -XX:MaxRAMPercentage=60). stdout stays clean either way — slf4j-simple logs to stderr and Main.kt redirects System.out to stderr — but if you need a memory ceiling, pass it yourself via JAVA_OPTS / -XX. The installDist launcher keeps those defaults.

Other MCP clients

Point the client at the same launcher (or java -jar the fat jar); only the surrounding config format differs. In every case command is the launcher (or java), and for the fat jar args is ["-jar", "-all.jar"]. --apk / --max-source-bytes and the load_apk / unload_apk tools behave identically no matter which client drives it.

mcpServers JSON — the de-facto standard, accepted by Claude Desktop, Cursor, Windsurf, Cline, Roo Code, LM Studio, Gemini CLI, and most others:

{
  "mcpServers": {
    "jadx-headless": {
      "command": "C:/tools/jadx-headless-mcp/bin/jadx-headless-mcp.bat"
    }
  }
}

Only the file it goes in differs — e.g. Claude Desktop claude_desktop_config.json, Cursor .cursor/mcp.json, Windsurf ~/.codeium/windsurf/mcp_config.json. Check your client’s MCP docs for the exact path.

VS Code / GitHub Copilot uses servers + type (not mcpServers), in .vscode/mcp.json:

{
  "servers": {
    "jadx-headless": {
      "type": "stdio",
      "command": "C:/tools/jadx-headless-mcp/bin/jadx-headless-mcp.bat"
    }
  }
}

TOML-based CLIs (Codex, Grok, …) use an mcp_servers table:

[mcp_servers.jadx-headless]
command = "C:/tools/jadx-headless-mcp/bin/jadx-headless-mcp.bat"
args = []

Remote mode (--transport http)

By default the server speaks stdio, so the MCP client spawns it as a local child process — client and jadx live on the same machine. To split them (client on machine B, jadx and the APK on machine A), run the server with the Streamable HTTP transport and point a remote MCP client at the URL:

# on machine A (where jadx runs and the APK lives)
./bin/jadx-headless-mcp --transport http --host 0.0.0.0 --port 8080 --allowed-host a.example.com

The endpoint is http://: (default http://127.0.0.1:8080/mcp). Point any Streamable-HTTP-capable MCP client at it — e.g. Claude Code:

claude mcp add --transport http jadx-headless http://a.example.com:8080/mcp

The APK always lives on the jadx host. load_apk resolves its path with File(path) on the machine running the server (A) — a remote client only sends a path string that must be valid on A. Copy the APK to A first, then call load_apk with the A-side path. It’s still one APK per process; multiple HTTP sessions share the single loaded APK.

Security:

• DNS-rebinding protection is on by default and only allows loopback Host headers, so a remote client reaching a.example.com is rejected with 403 unless you add --allowed-host a.example.com (or disable the check). This deliberately stops a malicious web page from driving your server.
• The endpoint has no authentication. Prefer binding to 127.0.0.1 and reaching it over an SSH tunnel, or put it behind a reverse proxy / VPN that adds auth. Don’t expose 0.0.0.0 on an untrusted network.

Architecture

Claude Code  ──stdio | Streamable-HTTP JSON-RPC──>  jadx-headless-mcp (JVM)
                                          │
                                          ├── MCP Kotlin SDK (stdio / Ktor CIO HTTP server)
                                          │
                                          └── SessionHolder
                                                 │  (Mutex-serialized load/unload)
                                                 └── JadxSession
                                                        └── JadxDecompiler (jadx-core)

Lazy decompilation: only get_class_source and get_smali_of_class (and get_method_by_name / code search) trigger per-class decompilation. Index building at startup is metadata-only.

Important: max_bytes truncates the response after jadx finishes materializing the class — it does not stop a slow decompile early. Fat obfuscated classes (e.g. large ViewModels) previously could block the whole MCP process for tens of minutes until the client’s multi-hour tool ceiling. As of the decompile-timeout fix:

• Server hard timeout: --decompile-timeout-ms (default 90000)
• On timeout the tool returns an // ERROR: ... timed out ... banner immediately
• Prefer get_class_summary + get_method_by_name for large classes

Memory tuning

The launcher sets -XX:MaxRAMPercentage=60.0 by default. Override via JAVA_OPTS:

JAVA_OPTS="-Xmx8g" ./bin/jadx-headless-mcp

Upstream tracking

Related but not auto-synced (different architecture; manual watch only):

• zinja-coder/jadx-ai-mcp — JADX GUI plugin
• zinja-coder/jadx-mcp-server — Python adapter for the above
• mobilehackinglab/jadx-mcp-plugin — alternative GUI plugin

If those projects ship a new tool worth porting, file an issue here.

Acknowledgements

• skylot/jadx — the underlying decompiler
• modelcontextprotocol/kotlin-sdk — MCP server framework

License

Apache-2.0.