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J
Js Reverse Pro MCP
by @a0yark
GitHub Repo(1 stars)

JS reverse engineering MCP server (Pro fork) — hook framework, deobfuscation, AI analysis, sessions, artifacts, portable bundle. Built on Patchright. Adapted from zhizhuodemao/js-reverse-mcp (Apache-2.0) and NoOne-hub/JSReverser-MCP (MIT).

Created 6/17/2026
Updated about 5 hours ago
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JS Reverse MCP

English | 中文

Pro fork: Derived from zhizhuodemao/js-reverse-mcp (Patchright stealth core preserved) and selectively ports capabilities from NoOne-hub/JSReverser-MCP — hook framework, static deobfuscation, AI analysis, session snapshots, artifacts, case library. See LICENSE (Apache-2.0) and LICENSE.JSReverser-MCP (MIT, NoOne-hub).

A JavaScript reverse engineering MCP server that enables AI coding assistants (Claude, Cursor, Codex) to debug and analyze JavaScript code in web pages.

Built on the Patchright anti-detection engine with multi-layered anti-bot bypass capabilities, allowing it to work on sites with bot detection such as Zhihu and Google.

Features

From upstream (preserved)

  • Anti-detection browser — Patchright (Playwright anti-detection fork), 60+ stealth launch arguments
  • Script analysis — list / search / get / save sources
  • Breakpoint debugging — set_breakpoint_on_text, break_on_xhr, step, get_paused_info
  • Function tracing — trace_function (logpoint mode, doesn't pause)
  • Network & WebSocket — request initiator stacks, WS message analysis
  • inject_before_load — CDP Page.addScriptToEvaluateOnNewDocument

Pro fork additions

  • Hook framework — 5 built-in templates (function/crypto/network/encoding/storage), CDP injection + Symbol-keyed sink + CDP Runtime.evaluate drain; survives navigation
  • Static deobfuscation — deobfuscate_code (Babel fast: string-array inline, constant fold, dead branch, _0xabcd rename, bracket→dot; optional webcrack deep)
  • Code collection — collect_code (scans for sign/encrypt/hmac etc. + AST heuristic ranking)
  • AI assist (default OFF) — understand_code / risk_panel, OpenAI / Anthropic / Gemini, dynamic-imported
  • Session snapshots — save/restore/dump/load_session_state, AES-256-GCM round-trip
  • Artifacts tasks — start_reverse_task / record_evidence / export_replay_bundle / export_portable_bundle, shareable .jrmcp.json bundles plus single-file portable / replay JS extraction
  • Two-layer stealth — --cloak opts into CloakBrowser source-level fingerprint patches (canvas / WebGL / audio / GPU); --legacyStealth is the explicit fork-default fallback that keeps the original stealth-args path
  • Tool profile gating — --toolProfile kernel|compact|full (default kernel); restart with compact for broader workflow controls, full to expose every tool
  • Browser state reset — clear_site_data clears cookies, HTTP cache, persistent storage, and sessionStorage for the current page's HTTP(S) frame origins without reloading
  • Network export — export_network_request writes captured request / response bytes, query params, or a metadata bundle to disk (and into the active task's evidence/ directory when taskId is set)
  • Local-file input for evaluate_script — pipe local files into in-page evaluation for replay and fixture-driven runs

Requirements

Installation

This fork is not published to npm; build from source:

git clone https://github.com/a0yark/js-reverse-pro-mcp.git
cd js-reverse-pro-mcp
npm install
npm run build

Claude Code

claude mcp add -s user js-reverse-pro -- node /ABS/PATH/js-reverse-mcp/build/src/index.js

Codex

codex mcp add js-reverse-pro -- node /ABS/PATH/js-reverse-mcp/build/src/index.js

Generic JSON config

{
  "mcpServers": {
    "js-reverse-pro": {
      "command": "node",
      "args": ["/ABS/PATH/js-reverse-mcp/build/src/index.js"]
    }
  }
}

Anti-Detection

Two coexisting stealth layers, selectable per launch:

  • Legacy stealth-args path (fork default; also gated by --legacyStealth): Patchright + 60+ stealth launch arguments. Matches behavior before --cloak existed.
  • Cloak path (--cloak): CloakBrowser stealth-patched Chromium with source-level fingerprint patches (canvas / WebGL / audio / GPU). Binary auto-downloads (~200MB) on first use; identity is persisted per profile in <profile>/.cloak-seed. Conflicts with --browserUrl, --wsEndpoint, --executablePath, --channel.

| Layer | Description | |-------|-------------| | Patchright Engine | C++ level patches, removes navigator.webdriver, avoids Runtime.enable leaks | | 60+ Stealth Args | Removes automation signatures, bypasses headless detection, GPU/network/behavior fingerprint spoofing | | Harmful Args Removal | Excludes --enable-automation and 4 other default Playwright arguments | | Silent CDP Navigation | Navigation tools don't activate CDP domains, captures requests only through Playwright-level listeners | | Google Referer Spoofing | All navigations automatically include referer: https://www.google.com/ | | Persistent Login State | Uses persistent user-data-dir by default, login state preserved across sessions | | Cloak source patches | --cloak only: canvas / WebGL / audio / GPU fingerprint patches applied inside the Chromium build |

Hook framework stealth discipline (Pro fork)

The 18 new tools follow strict stealth rules:

  • Injection path: CDP Page.addScriptToEvaluateOnNewDocument (same channel as upstream inject_before_load); no Playwright addInitScript / exposeBinding
  • Data sink: globalThis[Symbol.for('__jr_sink')] array + CDP Runtime.evaluate drain; no fixed string-named property on window, no console pollution
  • Function.prototype.toString self-cloaking: a stealth shim uses WeakMap<wrapped, orig> so Function.prototype.toString.call(fetch) returns function fetch() { [native code] }; the patched toString itself is registered, so Function.prototype.toString.toString() is also native
  • storage template cookie option default OFF: Object.defineProperty(document, 'cookie') leaves a non-native descriptor that advanced fingerprinters can detect
  • AI default OFF: only loads when --enableAI and the matching API key are both set; OpenAI / Anthropic / Gemini SDKs are dynamic-imported

See src/hooks/stealth-shim.ts header comment and the automated test tests/phase-b-smoke.mjs.

Tools (44)

From upstream (23)

Page & Navigation

| Tool | Description | |---|---| | select_page | List/select pages as debugging context | | new_page | Create new page and navigate | | navigate_page | Navigate / back / forward / reload | | select_frame | List/select frame execution context | | take_screenshot | Page screenshot |

Script Analysis

| Tool | Description | |---|---| | list_scripts | List all loaded JS scripts | | get_script_source | Get source by line range or character offset | | save_script_source | Save full source to local file | | search_in_sources | String/regex search across all scripts |

Breakpoint & Execution Control

| Tool | Description | |---|---| | set_breakpoint_on_text | Set breakpoint by code text search | | break_on_xhr | XHR/Fetch breakpoint by URL pattern | | remove_breakpoint | Remove by ID/URL or all | | list_breakpoints | List active breakpoints | | get_paused_info | Paused state, call stack, scope | | pause_or_resume | Toggle pause/resume | | step | Step over/into/out |

Function Tracing & Injection

| Tool | Description | |---|---| | trace_function | Logpoint trace (doesn't pause) | | inject_before_load | Inject pre-load script (raw CDP) |

Network & WebSocket

| Tool | Description | |---|---| | list_network_requests | List/get-detail network requests | | get_request_initiator | JS call stack for a request | | get_websocket_messages | WS connections / message analysis |

Inspection

| Tool | Description | |---|---| | evaluate_script | Run JS in page (paused / main world / file output / local file input supported) | | list_console_messages | Console messages list/detail |

Pro fork (21 new)

Browser state & network export (2)

| Tool | Description | |---|---| | clear_site_data | Clear cookies, HTTP cache, persistent storage, sessionStorage for current page's HTTP(S) frame origins (no reload) | | export_network_request | Export captured request / response bytes, query params, or metadata bundle to disk (and to task evidence/ when taskId is set) |

Hook framework (5)

| Tool | Description | |---|---| | create_hook | Render hook from template, returns hookId (no inject) | | inject_hook | Attach hook to current page + future navigations | | get_hook_data | Drain page-side sink, return per-hook events | | list_hooks | List hooks + injection state + buffer | | clear_hook | Remove CDP injection / purge buffer / delete hook record |

Built-in templates:

  • function — wrap any global by dotted path
  • crypto — CryptoJS / WebCrypto / JSEncrypt
  • network — XHR / fetch / WebSocket, with urlPattern filter + call stack
  • encoding — btoa / atob / TextEncoder / TextDecoder (JSON.* opt-in)
  • storage — localStorage / sessionStorage (cookie opt-in)

Static analysis (4)

| Tool | Description | |---|---| | deobfuscate_code | Babel passes (fast, always) + optional webcrack (deep) | | collect_code | Scan functions matching sign/encrypt/hmac etc. + score | | understand_code | LLM explains code semantics (default disabled) | | risk_panel | Aggregate hook + task signals into a risk report (default disabled) |

Session management (5)

| Tool | Description | |---|---| | save_session_state | Capture cookies + multi-origin localStorage/sessionStorage to memory | | restore_session_state | Apply snapshot to current context | | dump_session_state | Persist to disk, optional AES-256-GCM encryption | | load_session_state | Load from disk into memory (decrypts) | | get_storage | One-shot read of cookies/local/session/all |

Artifacts tasks (5)

| Tool | Description | |---|---| | start_reverse_task | Create task dir .jrmcp/tasks/<id>/ + task.json + timeline.jsonl | | record_evidence | Append evidence (>64KB auto-files into evidence/) | | export_replay_bundle | Export .jrmcp.json self-describing bundle | | export_portable_bundle | Collapse task evidence into single-file run/portable.js (pure extraction) and/or run/replay.js (rebuild capture) | | list_tasks | List all tasks under artifacts root |

Configuration Options

Upstream flags

| Option | Description | Default | |---|---|---| | --browserUrl, -u | Connect to running Chrome | - | | --wsEndpoint, -w | WebSocket endpoint | - | | --headless | Headless mode | false | | --executablePath, -e | Custom Chrome path | - | | --isolated | Temporary user-data-dir (fresh each time) | false | | --channel | stable/canary/beta/dev | stable | | --viewport | Viewport size, e.g. 1280x720 | real size | | --hideCanvas | Canvas fingerprint noise | false | | --blockWebrtc | Block WebRTC for IP leak | false | | --disableWebgl | Disable WebGL | false | | --noStealth | Disable stealth args (debug only) | false | | --proxyServer | Proxy config | - | | --logFile | Debug log path | - |

Pro fork flags

| Option | Description | Default | |---|---|---| | --artifactsDir | Artifacts root | ${cwd}/.jrmcp/tasks | | --sessionEncryptionKey | Session-dump default secret (also reads JRMCP_SESSION_KEY env) | - | | --hookBufferSize | Per-hook ring buffer capacity | 1000 | | --enableAI | Enable understand_code / risk_panel | false | | --llmProvider | openai / anthropic / gemini | - | | --cloak | Use CloakBrowser stealth-patched Chromium with source-level fingerprint patches (auto-downloads ~200MB) | false | | --legacyStealth | Explicitly select the legacy stealth-args path (conflicts with --cloak) | false | | --toolProfile | Which MCP tools are exposed at startup: kernel (high-value reverse-workflow tools only), compact (broader debugging), full (every tool) | kernel | | --listTools | Print the names of the tools selected by --toolProfile and exit without starting the MCP server | false |

Example configurations

Full setup (AI + enhanced stealth):

OPENAI_API_KEY=sk-... node build/src/index.js \
  --browserUrl=http://localhost:9222 \
  --enableAI --llmProvider=openai \
  --blockWebrtc \
  --artifactsDir=./my-tasks

Isolated (no persistent login, fresh each time):

{
  "mcpServers": {
    "js-reverse-pro": {
      "command": "node",
      "args": ["/ABS/PATH/build/src/index.js", "--isolated"]
    }
  }
}

Connect to running Chrome

Launch Chrome (close all Chrome windows first):

Windows

"C:\Program Files\Google\Chrome\Application\chrome.exe" --remote-debugging-port=9222 --user-data-dir="%TEMP%\chrome-debug"

macOS

/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --remote-debugging-port=9222 --user-data-dir=/tmp/chrome-debug

Then connect with --browserUrl=http://127.0.0.1:9222.

Workflow Cases

See scripts/cases/ for end-to-end workflows:

General workflow:

1. start_reverse_task creates a task
2. new_page to target site → list_network_requests to find signed requests
3. get_request_initiator to inspect call stack
4. create_hook(network, urlPattern=...) + inject_hook
5. trigger requests → get_hook_data for context
6. create_hook(crypto) + inject_hook → see which algorithms run
7. get_script_source for the chunk → deobfuscate_code(level=deep)
8. collect_code on deobfuscated source to locate the sign function
9. understand_code (optional) lets the LLM explain it
10. record_evidence per finding
11. export_replay_bundle (shareable `.jrmcp.json`) or export_portable_bundle (single-file `run/portable.js` / `run/replay.js`)

Troubleshooting

Blocked by anti-bot systems

If you are blocked when visiting certain sites (e.g. Zhihu returning error 40362):

  1. Clear the contaminated profile: delete ~/.cache/chrome-devtools-mcp/chrome-profile
  2. Use isolated mode: add --isolated
  3. Enable Canvas noise: add --hideCanvas

Hook captures no events

  1. Confirm inject_hook returned INJECTED (use list_hooks)
  2. Confirm rendered hook source has no syntax errors (start with --logFile)
  3. Re-injecting the same hook on a loaded page nests the wrap; clear_hook(hookId) first or reload

deobfuscate_code level=deep complains about webcrack

webcrack is an optional dependency that itself requires @babel/core. This fork already promotes @babel/core to dependencies; if it still complains, run npm install to refresh.

Security Notice

This tool exposes browser content to MCP clients, allowing inspection, debugging, and modification of any data in the browser. Do not use it on pages containing sensitive information.

License

Apache-2.0, inherited from upstream zhizhuodemao/js-reverse-mcp.

Pro fork ports reference NoOne-hub/JSReverser-MCP (MIT, original license preserved at LICENSE.JSReverser-MCP).

Quick Setup
Installation guide for this server

Install Package (if required)

npx @modelcontextprotocol/server-js-reverse-pro-mcp

Cursor configuration (mcp.json)

{ "mcpServers": { "a0yark-js-reverse-pro-mcp": { "command": "npx", "args": [ "a0yark-js-reverse-pro-mcp" ] } } }