diff --git a/.env.example b/.env.example
index bb4e46f4..a2741294 100644
--- a/.env.example
+++ b/.env.example
@@ -8,7 +8,8 @@ VITE_SUPABASE_ANON_KEY=your-anon-key
 VITE_GOOGLE_WEB_CLIENT_ID=your-web-client-id.apps.googleusercontent.com
 
 # Cloudflare Turnstile (signup bot gate) — public site key only
-# Matching secret key is a Supabase Edge Function secret: TURNSTILE_SECRET_KEY
+# Matching secret key goes in Supabase Dashboard → Authentication → CAPTCHA
+# protection (Turnstile), NOT in a VITE_* var. Client sends it via captchaToken.
 VITE_TURNSTILE_SITE_KEY=0x4AAAAA...your-turnstile-site-key
 
 # PostHog analytics (optional — skip in local dev)
diff --git a/src/services/authService.js b/src/services/authService.js
index d53de2a4..6ec1c0d8 100644
--- a/src/services/authService.js
+++ b/src/services/authService.js
@@ -137,7 +137,10 @@ export async function signInWithGoogleIdToken(
   turnstileToken
 ) {
   const supabase = requireClient();
-  const /** @type {Record<string, any>} */ options = {
+  // signInWithIdToken does not accept user `data` metadata. Turnstile must go
+  // through options.captchaToken → gotrue_meta_security.captcha_token (verified
+  // by GoTrue when Auth CAPTCHA protection is enabled).
+  const /** @type {Record<string, any>} */ credentials = {
       provider: 'google',
       token: idToken,
       nonce,
@@ -145,10 +148,10 @@ export async function signInWithGoogleIdToken(
     };
 
   if (turnstileToken) {
-    options.data = { cf_turnstile_response: turnstileToken };
+    credentials.options = { captchaToken: turnstileToken };
   }
 
-  const { error } = await supabase.auth.signInWithIdToken(options);
+  const { error } = await supabase.auth.signInWithIdToken(credentials);
 
   if (error) {
     throw error;
diff --git a/src/services/authService.test.js b/src/services/authService.test.js
index 20cec552..c5608e80 100644
--- a/src/services/authService.test.js
+++ b/src/services/authService.test.js
@@ -90,7 +90,7 @@ describe('authService', () => {
     });
   });
 
-  it('signInWithGoogleIdToken includes Turnstile token in user metadata when provided', async () => {
+  it('signInWithGoogleIdToken passes Turnstile token as captchaToken', async () => {
     await authService.signInWithGoogleIdToken(
       'token-123',
       undefined,
@@ -103,7 +103,7 @@ describe('authService', () => {
       token: 'token-123',
       nonce: undefined,
       access_token: undefined,
-      data: { cf_turnstile_response: 'turnstile-token' },
+      options: { captchaToken: 'turnstile-token' },
     });
   });
 
@@ -146,7 +146,7 @@ describe('authService', () => {
       token: 'google-id-token',
       nonce: undefined,
       access_token: undefined,
-      data: { cf_turnstile_response: 'cf-turnstile-ok' },
+      options: { captchaToken: 'cf-turnstile-ok' },
     });
   });
 
diff --git a/supabase/functions/before-signup/index.ts b/supabase/functions/before-signup/index.ts
index c70ef6a8..2f1dd6fe 100644
--- a/supabase/functions/before-signup/index.ts
+++ b/supabase/functions/before-signup/index.ts
@@ -49,45 +49,6 @@ function getServiceClient() {
   );
 }
 
-/**
- * Verify a Cloudflare Turnstile token via the siteverify endpoint.
- * Returns { success: boolean } — always succeeds if TURNSTILE_SECRET_KEY is
- * unset (graceful fallback for local dev or when Turnstile is not configured).
- */
-async function verifyTurnstileToken(
-  token: string | undefined
-): Promise<{ success: boolean }> {
-  const secretKey = Deno.env.get('TURNSTILE_SECRET_KEY');
-
-  if (!secretKey) {
-    return { success: true };
-  }
-
-  if (!token) {
-    return { success: false };
-  }
-
-  try {
-    const formData = new URLSearchParams();
-    formData.append('secret', secretKey);
-    formData.append('response', token);
-
-    const result = await fetch(
-      'https://challenges.cloudflare.com/turnstile/v0/siteverify',
-      {
-        method: 'POST',
-        body: formData,
-      }
-    );
-
-    const data = await result.json();
-    return { success: data.success === true };
-  } catch (err) {
-    console.error('before-signup: Turnstile verification error', err);
-    return { success: false };
-  }
-}
-
 export async function handleRequest(req) {
   if (req.method !== 'POST') {
     // Probes/scanners hit this URL with GET — log only, no Telegram noise.
@@ -127,14 +88,11 @@ export async function handleRequest(req) {
       return await reject('missing_ip');
     }
 
-    const turnstileToken = user.raw_user_meta_data?.cf_turnstile_response;
-    const turnstile = await verifyTurnstileToken(
-      typeof turnstileToken === 'string' ? turnstileToken : undefined
-    );
-
-    if (!turnstile.success) {
-      return await reject('turnstile_failed', { email, ip });
-    }
+    // Turnstile is NOT checked here. Google OIDC uses signInWithIdToken, which
+    // cannot attach custom raw_user_meta_data. The client sends the token as
+    // options.captchaToken; enable Auth → CAPTCHA protection (Turnstile) in the
+    // Supabase dashboard so GoTrue verifies it before this hook runs.
+    // This hook still enforces IP bans + signup rate limits.
 
     const supabase = getServiceClient();