API-First Registration + Turnstile Bypass — Lovable.dev Example

Context

Session: 2026-08-04. Goal: register accounts on lovable.dev. The signup is blocked by Cloudflare Turnstile (CDP detection). The site uses SolidStart (SolidJS) with Firebase Auth backend.

GET https://lovable.dev/signup — initial page with email-only field
Enter email → hits POST https://api.lovable.dev/auth/check-auth-provider {email}
- Returns provider list, userExists flag, domainLock, recoveryState
Password form appears → Turnstile widget rendered with sitekey 0x4AAAAAAChnKAZBY0iFpFHC
Form submit:
- Calls POST https://api.lovable.dev/auth/turnstile-signup {email, token} → 204
- Then Firebase createUserWithEmailAndPassword(email, password)
After account creation → redirect to /verify-email or login

SolidStart Server Function Pattern

The form uses SolidStart RPC: /_serverFn/<sha256hash>. These hash-based endpoints proxy to api.lovable.dev.

/_serverFn/[REDACTED-KEY] — email check (GET)
Refresh between page loads — hashes change per deploy

2captcha Configuration

import requests, time

def solve_turnstile(sitekey, pageurl, action="signup_email_password", api_key="[REDACTED-KEY]", timeout=60):
    r = requests.get("https://2captcha.com/in.php", params={
        "key": api_key, "method": "turnstile",
        "sitekey": sitekey, "pageurl": pageurl,
        "action": action, "json": 1
    }, timeout=10)
    if r.json().get("status") != 1:
        return None
    cid = r.json()["request"]
    for _ in range(timeout // 3):
        time.sleep(3)
        r2 = requests.get("https://2captcha.com/res.php", params={
            "key": api_key, "action": "get", "id": cid, "json": 1
        }, timeout=10)
        if r2.json().get("status") == 1:
            return r2.json()["request"]
    return None

Key params: method=turnstile, action=signup_email_password (must match the widget's action). Token is ~837 chars.

Turnstile CDP Detection

Chrome DevTools Protocol is detected by Turnstile's implicit challenge mode
Clicking the checkbox via CDP tools (mcp__chrome_devtools__click) produces: URL changes from /new/normal to /failure_retry/normal, iframe shows "Сбой проверки" (Verification failure)
Multiple retries with 2captcha tokens still fail because the form framework (turnstile.getResponse()) returns empty even when the hidden input is set
The Turnstile iframe also resets itself between clicks, each time showing /new/normal

Key API Endpoint

POST https://api.lovable.dev/auth/turnstile-signup

Headers required:

Content-Type: application/json
Origin: https://lovable.dev
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36

Body: {"email": "user@example.com", "token": "<2captcha-solved-token>"}

Returns: 204 No Content on success.

Rate limit: 2000/hour (x-ratelimit-remaining starts at 2000).

Temp-Mail Domain Blocklist

Lovable maintains a large blocked-domain Set (po) with ~300 entries in the JS bundle. Common blocked patterns:

yopmail.com, guerrillamail.com, mail.tm, tempmail domains
Any .sbs, .rest TLDs
Domains with + in the local part (plus-addressing) unless on whitelist (lovable.dev only)
Full list visible in the LoginSignupForm* JS bundle under po = new Set([...])

JS Bundle Discovery Pattern

Load page → extract modulepreloads from <link rel="modulepreload">
Read importmap <script type="importmap"> — maps old hash names to current ones
Target files: signup-*.js, LoginSignupForm-*.js, _auth-*.js
Search for turnstile-sitekey, serverFn calls, API endpoints
The importmap format: {"/assets/old-name.js": "/assets/new-name.js"}

Firebase Auth Integration

After turnstile validation, the client-side bundle calls Firebase Auth REST API via identitytoolkit.googleapis.com/v1/accounts:signUp?key=<API_KEY>. The API key is embedded in the webpack/rolldown bundle (not on window.firebase).

What Didn't Work

Setting cf-turnstile-response input value directly — form still shows disabled button
Clicking Turnstile checkbox via CDP — detected and rejected
Puppeteer-extra-stealth via browser_navigate tool — Chrome crashes with sandbox error
Standard HTTP client (requests) — blocked by Cloudflare

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