README.md

April 8, 2026 · View on GitHub

Leapfrog

Multi-session browser MCP for AI agents.
36 tools. 15 parallel sessions. Stealth. HUD. Self-improvement. Up to 10x fewer tokens.

npm i leapfrog-mcp | Works with Claude Code, Cursor, Windsurf

The Problem

Playwright MCP sends ~14,000 tokens for a content-heavy page like Hacker News. Most of that is noise. Your context window fills up. Your agent gets confused. You pay for it.

Leapfrog sends ~1,400 tokens. Same page. Same information. Up to 10x less noise.

┌─────────────────────────────────────────────────────┐
│  Playwright MCP                                     │
│  ████████████████████████████████████████  ~14,000   │
│                                                     │
│  Leapfrog                                           │
│  █████                                    ~1,400    │
└─────────────────────────────────────────────────────┘
          tokens per page (Hacker News, real test)

Savings range from 2-10x depending on page complexity. Content-heavy pages see the biggest wins. Dense forms see the smallest. The median across real-world sites is ~4-5x.

Quick Start

npx leapfrog-mcp --doctor          # verify everything works
npx leapfrog-mcp --stealth-audit   # test all 19 stealth patches
npx leapfrog-mcp --config          # print MCP config to paste

Add to ~/.mcp.json (Claude Code) or your editor's MCP config:

{
  "leapfrog": {
    "command": "npx",
    "args": ["-y", "leapfrog-mcp"],
    "env": {
      "LEAP_MAX_SESSIONS": "15",
      "LEAP_TILE": "true",
      "LEAP_HUD": "true",
      "LEAP_AUTO_CONSENT": "true"
    }
  }
}

Leapfrog uses playwright-core (15MB) instead of playwright (1.6GB) and does not bundle a browser. Either:

Set LEAP_CHANNEL=chrome to use your installed Chrome/Chromium (recommended)
Or run npx playwright-core install chromium to install the bundled Chromium binary
Or set LEAP_CDP_ENDPOINT to connect to an already-running Chrome instance

Feature Matrix

	Leapfrog	Playwright MCP	agent-browser
Tokens per page	~1,200-2,500	~3,800-15,000	~300
Parallel sessions	15	1	1
Session isolation	Yes	No	No
Multi-tab / popups	Yes	No	No
Network intercept	Yes	No	No
Console capture	Yes	Yes	No
Stealth / anti-bot	Yes	No	No
Smart wait (5 types)	Yes	Basic	No
Crash recovery	Yes	No	No
Batch actions (100/call)	Yes	No	No
Init script injection	Yes	Yes	No
Drag / upload / resize	Yes	Yes	No
Per-session proxy	Yes	No	No
Humanization (opt-in)	Yes	No	No
Auth profile reuse	Yes	No	No
Cookie persistence	Yes	No	No
Page classification (18)	Yes	No	No
Session memory	Yes	No	No
API intelligence	Yes	No	No
Adaptive wait + auto-retry	Yes	No	No
CAPTCHA auto-resolve	Yes	No	No
Self-improvement (9 dims)	Yes	No	No
Record / replay	Yes	No	No
Pagination extraction	Yes	No	No
Incremental snapshots (diff)	Yes	No	No
Stealth self-test CLI	Yes	No	No
SSRF protection	Yes	No	No

Stealth

Leapfrog ships 19 anti-detection patches enabled by default (LEAP_STEALTH=true). Four modes:

true (default) — all 19 patches active
passive — removes automation signals only (webdriver, HeadlessChrome). Does NOT fake identity (WebGL, fonts, audio). Better for sites where trust matters more than evasion.
auto — per-domain EXP3 bandit selects the optimal stealth configuration based on what's worked before
false — no stealth patches

These cover the vectors that fingerprint services like CreepJS and fingerprint-pro actually check:

Client Hints brands (strips HeadlessChrome)
navigator.webdriver forced to undefined
WebGL vendor/renderer (replaces SwiftShader with real GPU strings)
Connection RTT (non-zero)
Alert dismiss timing (human-speed delay)
Window outer/inner height offset
MIME type array population
Platform inference from user agent
chrome.app emulation
iframe contentWindow protection
Media codec spoofing (canPlayType)
document.hasFocus() override
Source URL comment stripping
Custom UA + stealth coexistence (custom user agents no longer disable stealth context)
CDP Runtime.enable detection (Error.prepareStackTrace filter)
Permissions API spoofing (20+ permission types)
AudioContext fingerprint noise (getChannelData/getFloatFrequencyData)
WebRTC IP leak prevention (ICE candidate filtering)
Font enumeration fingerprint spoofing

Per-session stealth control: pass stealth: false in session_create to disable for a specific session.

Humanization (Experimental)

Set LEAP_HUMANIZE=true to enable human-like browser interaction. This is opt-in and adds latency in exchange for more realistic behavior. Six modules:

Mouse — Bezier curve paths with Fitts's Law timing and micro-tremor jitter
Typing — Log-normal inter-key delays (200ms median), key dwell time, bigram-aware speed, rollover typing
Scroll — Inertial simulation with ramp-up and momentum decay (touchpad/mouse-wheel physics)
Pause — Inter-action "think" delays that simulate cognitive gaps between actions
Fingerprint — Coherent browser fingerprint generation (platform, device memory, GPU, timezone)
Utils — Shared math primitives (Box-Muller gaussian, distributions)

Page Classification

Every navigate and snapshot call automatically classifies the page type using weighted signal scoring (no LLM required). 18 types:

login · search-results · product · product-list · checkout · article · dashboard · form · error · challenge · landing · documentation · profile · media · feed · qa · ecommerce · unknown

Classification drives smarter snapshot extraction — login pages surface form fields, articles surface content, dashboards surface interactive elements.

Harness Intelligence

The harness tracks every action in a session and classifies outcomes:

Action outcome classification — SUCCESS, SILENT_CLICK, NAVIGATION, WRONG_ELEMENT, BLOCKED, ERROR, PENDING
Bot redirect detection — detects when a site redirects to a challenge or block page after an action
Loop detection — warns when the agent is stuck clicking the same element, ping-ponging between URLs, or repeating actions
Session memory — session_memory tool recalls actions after context window compression

Persistent browser profiles now use context.cookies() + addCookies() instead of storageState(), which returns empty on persistent contexts. Auth state survives across sessions.

Adaptive Wait + Stealth Escalation

Navigate automatically retries with fallback strategies when pages fail to load:

Try load (fastest) — if empty, retry with networkidle (10s cap)
If networkidle times out (Amazon, ad-heavy sites), fall back to domcontentloaded
If blocked/challenged, escalate stealth: random delays → wait for JS challenge → rotate session with fresh fingerprint
Profile sessions (auth'd) never have their session destroyed — hard-capped at Level 2

Opt-out with autoRetry: false on navigate. Control max escalation with maxRetryLevel (0-5, default 3).

Record / Replay

Export a session's action history as a replayable recording, then replay it in new sessions:

session_export — creates parameterized JSON or Playwright script from session history. @eN refs resolved to stable CSS selectors. Auto-detects emails, passwords, URLs as {{placeholders}}.
session_replay — replays a recording with parameter overrides. Supports onError: 'stop' or 'skip'.

Turn one-off agent workflows into reusable automations.

Pagination Extraction

Extract data across multiple pages in a single tool call:

Click-next — auto-detects "Next" buttons, pagination links, "Load more" buttons
Infinite scroll — scrolls and waits for new content via DOM hash comparison
URL pattern — increments ?page={page} or custom patterns

Replaces 3-4 tool calls per page. Cap: 50 pages, 100K total chars. Stops on: no next button, empty page, duplicate content, or bot detection.

Incremental Snapshots

The diff tool returns only what changed since the last snapshot — additions, removals, changes. Massive token savings for monitoring and polling workflows.

HUD Overlays (`LEAP_HUD=true`)

When running headed, Leapfrog overlays visual feedback on every session:

Click ripple — expanding green circle at click coordinates (agent actions only)
Zoom-to-target — browser zooms to 1.15x on the clicked element briefly so agents (and humans) can visually track what's happening in tiled windows
Scroll-to-target — scrollIntoView before clicks so you can see what the agent is about to click

Minimal by design. No borders, no status bars, no cursor overlay — just the feedback that matters.

Multi-Terminal Tiling (`LEAP_TILE=true`)

Multiple Leapfrog instances share the screen via file-based coordination. Each instance tracks its own windows and a TilesCoordinator assigns global grid slots — no overlap, no manual arrangement. Set LEAP_TILE=true (or LEAP_TILE=master for the primary instance). Padding between tiles is configurable with LEAP_TILE_PADDING (default 8px).

Human Intervention

Leapfrog auto-detects situations that need a human — CAPTCHAs, login forms, OAuth redirects, Cloudflare challenges — and tries to self-resolve before pausing.

Auto-resolves first: clicks reCAPTCHA checkboxes, Cloudflare verify buttons, generic verify/continue buttons, then a second-pass retry — all before asking for help
External solvers: set LEAP_CAPTCHA_PROVIDER + LEAP_CAPTCHA_API_KEY for CapSolver, 2Captcha, or NopeCHA integration
Learns what works: remembers which resolution method succeeded per domain and tries the known-good method first on revisit
Detects reCAPTCHA, hCaptcha, Turnstile, login forms, OAuth redirects, Cloudflare challenges
Tab title changes to "NEEDS HUMAN" when intervention is needed
wait_for_human tool — agent calls when stuck, blocks until you resolve it or navigate past

Automatically dismisses cookie consent banners across 10 frameworks (OneTrust, CookieBot, TrustArc, Quantcast, Didomi, Cookielaw, Osano, Usercentrics, + generic) plus text-matching fallback. Per-domain selector caching for instant replay on revisit.

Tracing (`LEAP_TRACE=true`)

Per-session Playwright tracing with screenshots + DOM snapshots. Export ZIP files viewable at trace.playwright.dev via the session_export_trace tool. Auto-saves on session destroy.

Self-Improvement

Leapfrog learns from every visit. Per-domain knowledge persists at ~/.leapfrog/domains/{domain}.json — 9 dimensions, all automatic:

#	Dimension	What it does
1	Wait strategies	Learns optimal wait method per domain (`networkidle` vs `domcontentloaded` vs `load`) + running average timing
2	Stealth tiers	Auto-escalates 0→3 when blocks are detected (2+ blocks in 1 hour). Starts at learned tier on revisit
3	Consent selectors	Remembers cookie banner dismiss selectors, auto-clicks on revisit
4	Challenge resolution	Records which CAPTCHA method worked (reCAPTCHA checkbox, Cloudflare verify, etc.), tries known-good method first
5	Stable element suppression	Identifies nav/footer/sidebar elements seen 3+ visits, suppresses from snapshots (30-40% token savings on mature domains)
6	Selector healing	Remembers element fingerprints → selectors, heals broken refs across visits
7	API endpoint caching	Discovered API endpoints persist across sessions
8	Interaction heat maps	Tracks which elements agents actually use, suppresses untouched elements (coming)
9	Strategy selection	Adversarial bandit (EXP3) for stealth config optimization. Use `LEAP_STEALTH=auto` to enable.

LRU eviction at 500 domains. Inspect with the domain_knowledge tool.

SSRF Hardening

URL validation blocks hex-encoded IPs (0x7f000001), octal notation (0177.0.0.1), CGNAT ranges (100.64.0.0/10), and redirect chains that resolve to internal addresses. Localhost and 127.0.0.0/8 are allowed by default for local dev workflows — set LEAP_BLOCK_LOCALHOST=true to block them.

The Ecosystem

Leapfrog uses pond metaphors to keep things memorable. Your agent is the frog.

Concept	Leapfrog term	What it means
Sessions	Ponds	Isolated browser contexts — cookies, storage, state
Tabs	Lily pads	Where the frog lands within a pond
Navigate	Leap	Jump to a URL, get a compact snapshot back
Snapshots	Surface	What you see on the surface — interactive `@eN` refs
Network traffic	Ripple	HTTP requests flowing under the surface
Console errors	Croak	Something went wrong in the browser
Stealth mode	Camouflage	Anti-bot evasion patches

All 36 Tools

Pond Management (11)

Tool	What it does
`session_create`	Open a new pond — isolated cookies, state, viewport, locale, timezone, stealth, proxy
`session_destroy`	Drain a pond and free the slot
`session_list`	See all active ponds with URLs and idle times
`session_save_profile`	Save auth state to disk for future ponds
`session_list_profiles`	List saved auth profiles
`pool_status`	Pool stats, memory, uptime
`session_health`	Is the pond healthy? Browser connected, page responsive?
`profile_list`	List saved persistent browser profiles
`profile_delete`	Delete a saved persistent browser profile and its data
`profile_import_from_chrome`	Import cookies and state from an installed Chrome profile
`profile_warm`	Pre-warm a profile by loading key URLs to establish cookies/state

Tool	What it does
`navigate`	Leap to a URL, return a compact `@eN` snapshot. Adaptive wait + stealth escalation built in.
`snapshot`	Re-read the surface (scope with CSS selector)
`diff`	Incremental snapshot — returns only what changed since last snapshot
`act`	Click, fill, type, check, select, press, scroll, hover, mousemove, drag, upload, resize, back, forward
`batch_actions`	Up to 100 sequential actions in one MCP call — eliminates round-trip overhead
`paginate`	Extract data across multiple pages in one call (click-next, scroll, URL pattern)
`add_init_script`	Inject JS that runs before every page load, persists across navigations
`wait_for`	Wait for element / text / network idle / navigation / JS expression
`screenshot`	Capture PNG (full page or element)
`extract`	Pull text, HTML, title, URL, or evaluate JS
`session_memory`	Recall actions performed in this session — recovers context after compression
`session_export`	Export session history as a replayable JSON recording or Playwright script

Tab Management (3)

Tool	What it does
`tabs_list`	List all pads in a pond
`tab_switch`	Hop to another pad (-1 for most recent popup)
`tab_close`	Close a pad (can't close the last one)

Agent Intelligence (3)

Tool	What it does
`wait_for_human`	Pause for human intervention — blocks until user clicks Done on the `@..@` overlay
`domain_knowledge`	Inspect what Leapfrog has learned about a domain (wait strategies, stealth tiers, endpoints)
`session_export_trace`	Export a Playwright trace ZIP — viewable at trace.playwright.dev

Network & API Intelligence (7)

Tool	What it does
`network_log`	See HTTP traffic — filter by URL, method, status, content-type
`console_log`	Read browser console output, filtered by level
`network_intercept`	Block, mock, or log requests by URL pattern
`api_discover`	List JSON APIs the page has called, classified by category (data, tracking, auth, cdn, ads)
`api_export`	Generate an OpenAPI v3 spec from observed API traffic
`execute`	Run a Playwright script in a sandboxed environment — replaces 5-20 sequential MCP round trips
`session_replay`	Replay a recording in the current session with parameter overrides

Environment Variables

Variable	Default	Description
`LEAP_MAX_SESSIONS`	`15`	Max concurrent sessions
`LEAP_IDLE_TIMEOUT`	`1800000`	Session idle timeout in ms (30 min). Set `0` to disable.
`LEAP_HEADLESS`	`true`	Set `false` to watch the browser
`LEAP_HEADED`	`false`	Set `true` to watch the browser (positive alternative to `LEAP_HEADLESS`)
`LEAP_CHANNEL`	(bundled chromium)	Set `chrome` to use your installed Chrome
`LEAP_CDP_ENDPOINT`	(none)	Connect to a running Chrome instance (e.g. `http://localhost:9222`)
`LEAP_EXTENSIONS`	(none)	Comma-separated paths to browser extensions to load
`LEAP_ALLOW_JS`	`true`	Allow JS evaluation in `extract` and `wait_for`
`LEAP_STEALTH`	`true`	Stealth mode: `true` \| `passive` \| `auto` \| `false`. See Stealth section.
`LEAP_STEALTH_PROFILES`	`false`	Enable stealth patches on profile (auth'd) sessions
`LEAP_CDP_STEALTH`	`true`	CDP detection evasion (`Runtime.enable` filtering)
`LEAP_HUMANIZE`	`false`	Experimental. Human-like mouse movement, typing cadence, and scroll behavior.
`LEAP_ALLOW_EXECUTE`	`true`	Allow the `execute` tool (sandboxed Playwright scripts)
`LEAP_BLOCK_LOCALHOST`	`false`	Block localhost/127.x.x.x (allowed by default for local dev)
`LEAP_PROFILES_DIR`	`~/.leapfrog/chrome-profiles`	Directory for persistent browser profiles
`LEAP_TILE`	`false`	Tile sessions in a grid (`true` \| `master` \| `false`)
`LEAP_TILE_PADDING`	`8`	Padding between tiled windows (px)
`LEAP_MULTI_TILE`	`false`	Multi-terminal tiling coordination across Leapfrog instances
`LEAP_SCREEN_WIDTH`	(auto)	Explicit screen width for tiling calculations
`LEAP_SCREEN_HEIGHT`	(auto)	Explicit screen height for tiling calculations
`LEAP_HUD`	`false`	Click ripple, zoom-to-target, scroll-to-target on agent actions
`LEAP_AUTO_CONSENT`	`true`	Auto-dismiss cookie consent banners (10 frameworks + fallback)
`LEAP_TRACE`	`false`	Per-session Playwright tracing (screenshots + DOM snapshots)
`LEAP_RECORD`	`false`	Session recording (action history export)
`LEAP_REBROWSER`	`false`	Enable Rebrowser integration
`LEAP_AUTO_WARM`	`false`	Auto-warm profiles by loading key URLs on session create
`LEAP_CAPTCHA_PROVIDER`	(none)	External CAPTCHA solver: `capsolver` \| `2captcha` \| `nopecha`
`LEAP_CAPTCHA_API_KEY`	(none)	API key for the configured CAPTCHA provider
`LEAP_MAX_SESSIONS_PER_CLIENT`	(none)	Per-client session pool limit
`LEAP_LOG_LEVEL`	`info`	`debug` / `info` / `warn` / `error`

Tests

 769 passing across 31 suites

Session management, snapshot engine, snapshot differ, network intelligence, tab management, security, SSRF protection, stealth patches (19), stealth enhanced, humanization (mouse, typing, scroll), page classification, harness intelligence, API intelligence, script executor, extended actions, HUD overlays, human intervention, cookie consent, domain knowledge, selector healing, stable elements, tile manager, bug regression, integration smoke, stress tests, benchmarks.

npm test

Requirements

Node.js >= 20
Chromium — use system Chrome (LEAP_CHANNEL=chrome) or install via npx playwright-core install chromium

License

MIT