How to fix provider_email_needs_verification: Email verification required by OAuth provider in Supabase

The primary fix is to ensure the email address is verified with the OAuth provider:

For Google accounts:
1. Go to https://myaccount.google.com/
2. Click "Security" in the left menu
3. Verify that your email is confirmed (it should show a checkmark)
4. If not verified, click "Email address" and follow the verification steps
5. Check your email inbox for verification link from Google

For GitHub accounts:
1. Go to https://github.com/settings/emails
2. Check the "Primary email address" section
3. If there's a yellow warning, click "Resend" to verify
4. Check your email inbox for GitHub verification link
5. Ensure "Keep my email address private" is not blocking public email access

For other OAuth providers:
- Check their account settings for email verification
- Look for "Verified Emails" or similar section
- Complete any pending email verification steps

After verifying your email with the OAuth provider, the changes may take a few minutes to propagate:

1. Clear your browser's local storage and cache:
- Open browser DevTools (F12 or right-click → Inspect)
- Go to Application tab
- Clear localStorage and sessionStorage
- Close all app tabs

2. Close your browser completely
3. Re-open and try the OAuth login again

Alternatively, use incognito/private mode to avoid cached data:
- Chrome: Press Ctrl+Shift+N (Windows) or Cmd+Shift+N (Mac)
- Firefox: Press Ctrl+Shift+P (Windows) or Cmd+Shift+P (Mac)
- Safari: Press Cmd+Shift+N

Verify your Supabase project's email configuration:

1. Go to Supabase Dashboard → Authentication → Providers
2. Look for "Email" provider settings
3. Check the "Confirm email" setting:
- Enabled: Users must verify email before signing in
- Disabled: Email is auto-confirmed, allowing immediate access

For OAuth providers specifically:
1. Go to Supabase Dashboard → Authentication → Providers
2. Expand the OAuth provider (Google, GitHub, etc.)
3. Check if there's an "Auto-confirm OAuth email" or similar option
4. Enable it if available to auto-confirm emails from trusted OAuth providers

Note: Having Confirm Email disabled assumes the OAuth provider's email verification is sufficient security.

Verify your OAuth provider configuration:

1. Go to Supabase Dashboard → Authentication → Providers
2. Click on the failing OAuth provider (Google, GitHub, etc.)
3. Verify credentials are correct:
- Client ID matches provider's console
- Client secret is valid
- Redirect URL matches provider's configuration

4. For Google OAuth specifically:
- Go to Google Cloud Console → APIs & Services
- Click the project with your OAuth credentials
- Go to Credentials
- Click the OAuth 2.0 Client ID
- Under "Authorized redirect URIs", ensure it includes:
- https://[project-ref].supabase.co/auth/v1/callback

5. For GitHub OAuth:
- Go to GitHub Settings → Developer settings → OAuth Apps
- Click your application
- Verify "Authorization callback URL" is:
- https://[project-ref].supabase.co/auth/v1/callback

Add error handling in your client code to catch and respond to this error. Create a function to sign in with OAuth and handle the provider_email_needs_verification error specifically.

In your authentication handler:
- Check if error.message includes 'provider_email_needs_verification'
- Show user-friendly message explaining email verification is needed
- Direct user to provider's email settings
- Offer retry option after verification

For example:
- Catch the error from signInWithOAuth call
- Display message: "Email not verified - Please verify your email with [Provider] and try again"
- Handle identity linking errors separately from initial signup errors
- Log full error details for debugging

If the error occurs when attempting to link OAuth to existing account:

1. Review Supabase Dashboard → Authentication → User Management
2. Check the user's "Identities" tab to see linked accounts
3. Verify "Manual Linking" is enabled if users need to manually link accounts:
- Go to Supabase Dashboard → Authentication → Providers
- Look for "Manual Linking" option in OAuth provider settings
- Enable if users should manually link identities

4. Check for conflicting identities:
- In Supabase SQL editor, look up the user's identities
- Verify each identity has email_verified status
- Check if email exists with unconfirmed identity

If the email is verified with the OAuth provider but the error persists:

For Google accounts:
- Go to https://support.google.com/accounts
- Search for "email verification"
- Verify account security settings are correct

For GitHub accounts:
- Go to https://github.com/contact
- Report account access issues
- Verify no suspicious login attempts

For other providers:
- Check their official support documentation
- Verify email is on account settings
- Look for email verification or confirmation status

Also test the OAuth flow with detailed logging to see what data Supabase receives from the provider.