cdp-connect-kit

Playwright connect_over_cdp kit — parse MLX Launcher ports, health-check CDP, retry Playwright attach with metrics.

pip install cdp-connect-kit
cdp-connect ping 127.0.0.1:9222

CLI: cdp-connect · Python 3.10+ · optional [mlx] for Launcher helpers

CDP connection toolkit — parse Chrome DevTools Protocol endpoints, validate WebSocket URLs, connect Playwright with retry + timeout + health metrics, and watch endpoint uptime.

Optional [mlx] extra: start Multilogin X profiles via Launcher API → auto connect_over_cdp.

Partner (optional): Production CDP attach goes through MLX Launcher (isolated profiles). Multilogin X · SAAS50 / MIN50 on eligible new purchases. ping / playwright work on any CDP server without MLX. Affiliate disclosure · Multilogin promo codes.

Problem

Connecting Playwright to a remote or antidetect browser over CDP fails for predictable reasons:

• Wrong URL shape (ws:// vs http://127.0.0.1:PORT)
• Browser not finished starting
• Fragile one-shot connect_over_cdp with no metrics

cdp-connect normalizes endpoints, waits for /json/version, retries connections, and reports health.

Install

pip install cdp-connect-kit
playwright install chromium

MLX Launcher integration:

pip install cdp-connect-kit[mlx]

Quick start

# Ping a CDP endpoint (HTTP or WebSocket URL)
cdp-connect ping ws://127.0.0.1:9222/devtools/browser/abc

# Connect Playwright and screenshot
cdp-connect playwright --endpoint http://127.0.0.1:9222 --screenshot out.png

# Watch health — JSON Lines for farm-runner piping
cdp-connect watch --endpoint 127.0.0.1:9222 --interval 5 | tee health.jsonl

Connection flow

sequenceDiagram
    participant MLX as MLX Launcher
    participant CDP as CDP HTTP :PORT
    participant PW as Playwright

    MLX->>MLX: GET /profile/.../start
    MLX-->>CDP: data.port → http://127.0.0.1:PORT
    PW->>CDP: GET /json/version
    CDP-->>PW: webSocketDebuggerUrl
    PW->>PW: connect_over_cdp(http://127.0.0.1:PORT)

CLI

Command	Description
cdp-connect ping ENDPOINT	Validate /json/version, print WebSocket URL
cdp-connect playwright --endpoint URL [--screenshot FILE]	Connect with retry, emit metrics JSON
cdp-connect watch --endpoint URL	Poll health as JSON Lines (default)
cdp-connect watch --format plain	Human-readable UP/DOWN lines
cdp-connect playwright --max-retries N	Connect with exponential backoff
cdp-connect mlx-start --profile-id UUID [--print-cdp-url]	Start MLX profile, wait for CDP ([mlx])
cdp-connect mlx-stop --profile-id UUID	Stop MLX profile — idempotent ([mlx])
cdp-connect mlx-list	List running Launcher sessions ([mlx])

Endpoint formats: http://127.0.0.1:9222, ws://127.0.0.1:9222/devtools/browser/…, 127.0.0.1:9222 (shorthand; default port 9222).

MLX launcher flow

1. GET launcher.mlx.yt:45001/api/v2/profile/f/{folder}/p/{profile}/start?automation_type=playwright
2. Read data.port from JSON response
3. CDP HTTP base = http://127.0.0.1:{port}
4. GET /json/version → webSocketDebuggerUrl
5. playwright.chromium.connect_over_cdp(http://127.0.0.1:{port})

Canonical MLX bridge for the monorepo: docs/MLX_INTEGRATION.md · Env: docs/ENV.md

export MLX_TOKEN="..."
export MLX_FOLDER_ID="..."
export MLX_LAUNCHER_URL="https://launcher.mlx.yt:45001"   # optional

# Scripting: CDP URL on stdout
CDP_URL=$(cdp-connect mlx-start --profile-id PROFILE_UUID --print-cdp-url)

cdp-connect mlx-list
cdp-connect mlx-stop --profile-id PROFILE_UUID

API

from cdp_connect_kit import CdpClient, connect_playwright, parse_endpoint
import asyncio

async def main():
    client = CdpClient("127.0.0.1:9222")
    print(client.resolve_websocket_url())
    browser, pw, metrics = await connect_playwright("127.0.0.1:9222", max_retries=5)
    print(metrics.to_dict())
    await browser.close()
    await pw.stop()

asyncio.run(main())

Symbol	Description
parse_endpoint(url)	Normalize HTTP / WS / host:port
CdpClient	/json/version, /json/list, health_snapshot()
connect_playwright(endpoint)	Retry wrapper → (browser, playwright, ConnectMetrics)
watch_endpoint(endpoint)	Async health polling

ConnectMetrics

{
  "endpoint": "http://127.0.0.1:9222",
  "web_socket_url": "ws://127.0.0.1:9222/devtools/browser/...",
  "attempts": 1,
  "connect_ms": 842.1,
  "ready_ms": 120.5,
  "target_count": 3
}

When connect_over_cdp keeps failing (playbook)

Most failures are endpoint shape or browser not ready — not Playwright bugs.

Error pattern	Likely cause	Fix
Connection refused	Port not open yet	cdp-connect ping in a loop; MLX: mlx-start --wait-timeout
Invalid URL / WS mismatch	Passed raw ws://… without version fetch	Use HTTP base http://127.0.0.1:PORT; let client resolve WS
Works once, flaky in farm	Race on profile start	watch --endpoint URL → JSONL for farm-runner; retry connect_playwright
Chrome 136+ local profile	Default user-data-dir blocks CDP	Custom profile dir or antidetect Launcher port
MLX 401 / timeout	Agent not running or wrong token	MLX_TOKEN, desktop agent up; see docs/ENV.md

MLX → Playwright pipeline:

export MLX_TOKEN=... MLX_FOLDER_ID=...
CDP_URL=$(cdp-connect mlx-start --profile-id PROFILE_UUID --print-cdp-url)
cdp-connect ping "$CDP_URL"
cdp-connect playwright --endpoint "$CDP_URL" --max-retries 5
# farm scripts: export CDP_URL for child processes
cdp-probe run --cdp-endpoint "$CDP_URL" --url https://example.com
cdp-connect mlx-stop --profile-id PROFILE_UUID

Coupon hub: Multilogin promo codes — guides for SAAS50 / MIN50, pricing comparisons, and workflow playbooks. Farm-scale partner note: Folder pools need stable Launcher CDP — Multilogin X is the [mlx] target stack. Code SAAS50 (browser) · coupons: cdp-connect --show-deal.

Canonical API details: docs/MLX_INTEGRATION.md.

Limitations

• Chromium CDP only — connect_over_cdp targets Chromium-based browsers.
• MLX requires local agent — Launcher API needs Multilogin desktop running.
• Watch mode uses HTTP discovery only; JSONL output is designed for automation-farm-runner ingestion.
• Not a fingerprint tool — connects to browsers; does not modify profiles.

Production

Use cdp-connect mlx-start → connect_playwright in farm scripts and probes; pair with farm-runner (automation-farm-runner) for folder pools. Export CDP_URL for human-input-kit warmup and playwright-cdp-probe checks on the same Launcher session.

Partner note (affiliate): When Playwright must attach to Multilogin X Launcher CDP ports (not vanilla --remote-debugging-port), isolated profiles are the intended production path. Eligible new browser purchases may accept code SAAS50 at multilogin.com — verify terms before checkout. ping / playwright / watch work on any CDP server without MLX. Full disclosure: docs/AFFILIATE.md. Deals hub: anti-detect.github.io. Coupon details only via cdp-connect --show-deal (never printed by default).

FAQ: docs/FAQ.md — Playwright connect_over_cdp, Multilogin Launcher, CDP health check.

Related tools (on PyPI)

Package	CLI	Role
playwright-cdp-probe	cdp-probe	CDP / WebDriver exposure score
cookie-jar-bridge	cookie-bridge	Netscape ↔ Playwright cookies
proxy-lane-checker	proxy-lane	Proxy TCP / HTTP / geo / DNSBL
fingerprint-coherence	fp-coherence	UA / screen / timezone lint

Toolkit pipeline: proxy-lane check → fp-coherence audit → automate → cdp-probe run → cookie-bridge validate

License

MIT

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Production antidetect (partner): Multilogin X · Code SAAS50 (-50% browser) · MIN50 (-50% cloud phone)
Affiliate disclosure — we may earn a commission; offers change on the vendor site. More scripts: @Multilogin_Scripts_Bot · Multilogin promo codes