iOS Phone Auth fails with ERROR_RECAPTCHA_SDK_NOT_LINKED after toggling reCAPTCHA Enterprise

[irangareddy]

Description

This issue has occurred recently, and no prior bug reports or context are available. Please review it promptly and suggest any necessary changes.

On iOS, Phone Authentication with Firebase fails after accidentally enabling and then disabling reCAPTCHA Enterprise in the Firebase Console.

The error indicates that the reCAPTCHA SDK is not linked, even though Enterprise was disabled and no explicit integration was added.

Client

• Platform: iOS (SwiftUI app)
• firebase-ios-sdk: 12.2.0
• Xcode: Version 26.0 (17A321)
• Device: iPhone 17 Pro (iOS 26)

Notes

• Multiple developers report this issue ([#17557]([firebase_auth]:Error code: [firebase_auth/recaptcha-sdk-not-linked] The reCAPTCHA SDK is not linked to your app. See https://cloud.google.com/recaptcha-enterprise/docs/instrument-ios-apps flutterfire#17557)).
• Problem seems triggered once reCAPTCHA Enterprise API is enabled in the Console, even if later disabled.
• The iOS SDK appears to still expect reCAPTCHA Enterprise integration.

---

✅ Request:
Please clarify whether this is a Firebase Console bug (Enterprise toggle not fully reverting) or whether firebase_auth iOS.

Reproducing the issue

Steps to Reproduce

1. Enable Phone Authentication with FirebaseAuth.instance.verifyPhoneNumber() (or SwiftUI equivalent).

    /// Send phone verification code using Firebase Phone Auth
    @MainActor public func sendPhoneVerification(phoneNumber: String) async throws -> String {
            return try await withCheckedThrowingContinuation { continuation in
              PhoneAuthProvider.provider()
                .verifyPhoneNumber(phoneNumber, uiDelegate: nil) { verificationID, error in
                  if let error = error {
                    continuation.resume(throwing: error)
                    return
                  }
                  continuation.resume(returning: verificationID!)
                }
            }
          }

2. In Firebase Console → Authentication → Settings → reCAPTCHA, click Manage reCAPTCHA (this auto-enables Enterprise).
3. Disable reCAPTCHA Enterprise from Google Cloud.
4. Run the app on iOS and attempt phone verification.

---

Expected Behavior

Phone authentication should work without requiring explicit recaptcha-enterprise-mobile-sdk integration if Enterprise is disabled.

https://github.com/GoogleCloudPlatform/recaptcha-enterprise-mobile-sdk

Actual Behavior

Phone authentication fails with the following errors:

❌ Phone authentication failed
Error: The reCAPTCHA SDK is not linked to your app.
NSError domain: FIRAuthErrorDomain
NSError code: 17208
NSError userInfo: {
  FIRAuthErrorUserInfoNameKey = ERROR_RECAPTCHA_SDK_NOT_LINKED,
  NSLocalizedDescription = The reCAPTCHA SDK is not linked to your app. 
  See https://cloud.google.com/recaptcha-enterprise/docs/instrument-ios-apps
}
🔥 Unknown auth error code: FirebaseAuth.AuthErrorCode(rawValue: 17208)

Phone verification error: Error Domain=FIRAuthErrorDomain Code=17208 "The reCAPTCHA SDK is not linked to your app. See https://cloud.google.com/recaptcha-enterprise/docs/instrument-ios-apps" UserInfo={FIRAuthErrorUserInfoNameKey=ERROR_RECAPTCHA_SDK_NOT_LINKED, NSLocalizedDescription=The reCAPTCHA SDK is not linked to your app. See https://cloud.google.com/recaptcha-enterprise/docs/instrument-ios-apps}
- "the recaptcha sdk is not linked to your app. see https://cloud.google.com/recaptcha-enterprise/docs/instrument-ios-apps"

---

Firebase SDK Version

12.2.0

Xcode Version

Version 26.0 (17A321)

Installation Method

Swift Package Manager

Firebase Product(s)

Authentication

Targeted Platforms

iOS

Relevant Log Output

If using Swift Package Manager, the project's Package.resolved

Expand Package.resolved snippet

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If using CocoaPods, the project's Podfile.lock

Expand Podfile.lock snippet

Replace this line with the contents of your Podfile.lock!

[rizafran]

Thanks for reporting, @irangareddy. I tried to reproduce the issue by following the steps you shared, but I'm unable to get the same error. Here's what I did:

• Enable the reCAPTCHA SMS in Authentication dashboard under Settings
• Go to GCP console and disable the reCAPTCHA Enterprise API
• Run the app
• I'm able to receive otp

Let me know if we're on the same page. Also, have you tried to clean build your project and quit then restart Xcode after disabling the reCAPTCHA Enterprise API? Additionally, I'm wondering if you have tried disabling the reCAPTCHA SMS defense?

[oliver-bevan]

Disabling reCAPTCHA SMS defence works.

The SDK falls back to loading the captcha via SFSafariViewController and providing you handle the URL callback with .onOpenURL or in the AppDelegate everything works as expected. It seems that using the reCAPTCHA SMS defence will require including the SDK separately but I'm not sure where the configured reCAPTCHA client would need to be provided to Firebase Auth.

[oliver-bevan]

Also note that this issue is also present in the Flutter Firebase SDK.