SMS 2FA fails with HTTP 412 when the trusted phone number ID isn't 1

diff --git a/Sources/XKit/GrandSlam/Operations/GrandSlamTwoFactorAuthenticateOperation.swift b/Sources/XKit/GrandSlam/Operations/GrandSlamTwoFactorAuthenticateOperation.swift
index 5a41e02..a0f1dde 100644
--- a/Sources/XKit/GrandSlam/Operations/GrandSlamTwoFactorAuthenticateOperation.swift
+++ b/Sources/XKit/GrandSlam/Operations/GrandSlamTwoFactorAuthenticateOperation.swift
@@ -25,11 +25,37 @@ struct GrandSlamTwoFactorAuthenticateOperation {
     let loginData: GrandSlamLoginData
     unowned let delegate: TwoFactorAuthDelegate
 
+    private struct TrustedPhoneNumber: Decodable {
+        let id: Int
+        var nonFTEU: Bool?
+    }
+
+    private struct PhoneVerificationResponse: Decodable {
+        let trustedPhoneNumbers: [TrustedPhoneNumber]
+    }
+
+    private func sendSMS(to phoneNumber: TrustedPhoneNumber) async throws {
+        try await client.send(GrandSlamSMSAuthRequest(
+            loginData: loginData,
+            phoneNumberID: phoneNumber.id,
+            nonFTEU: phoneNumber.nonFTEU
+        ))
+    }
+
     private func performSMSAuth() async throws {
-        // TODO: parse phone number list from o=complete req?
-        let phoneNumberID = 1
+        var phoneNumber = TrustedPhoneNumber(id: 1)
         do {
-            try await client.send(GrandSlamSMSAuthRequest(loginData: loginData, phoneNumberID: phoneNumberID))
+            do {
+                try await sendSMS(to: phoneNumber)
+            } catch let error as HTTPResponseError where error.status.code == 412 {
+                // the ID is not always 1; Apple lists the valid ones in the 412 response
+                guard let trusted = error.body
+                    .flatMap({ try? JSONDecoder().decode(PhoneVerificationResponse.self, from: Data($0.utf8)) })?
+                    .trustedPhoneNumbers.first
+                else { throw error }
+                phoneNumber = trusted
+                try await sendSMS(to: phoneNumber)
+            }
         } catch let error as HTTPResponseError where error.status.code == 403 {
             d.out.print("""
             warning: Could not send verification code via SMS. Falling back to trusted device authentication...
@@ -37,15 +63,16 @@ struct GrandSlamTwoFactorAuthenticateOperation {
             try await performTrustedDeviceAuth()
             return
         }
-        try await validateCode(phoneNumberID: phoneNumberID)
+        try await validateCode(phoneNumber: phoneNumber)
     }
 
-    private func validateCode(phoneNumberID: Int? = nil) async throws {
+    private func validateCode(phoneNumber: TrustedPhoneNumber? = nil) async throws {
         guard let code = await self.delegate.fetchCode() else { throw Error.userCancelled }
-        let request: any GrandSlamRequest = if let phoneNumberID {
+        let request: any GrandSlamRequest = if let phoneNumber {
             GrandSlamValidateSMSRequest(
                 loginData: loginData,
-                phoneNumberID: phoneNumberID,
+                phoneNumberID: phoneNumber.id,
+                nonFTEU: phoneNumber.nonFTEU,
                 verificationCode: code
             )
         } else {
diff --git a/Sources/XKit/GrandSlam/Requests/Concrete/GrandSlamTrustedDeviceRequest.swift b/Sources/XKit/GrandSlam/Requests/Concrete/GrandSlamTrustedDeviceRequest.swift
index 628ba9f..545a7f4 100644
--- a/Sources/XKit/GrandSlam/Requests/Concrete/GrandSlamTrustedDeviceRequest.swift
+++ b/Sources/XKit/GrandSlam/Requests/Concrete/GrandSlamTrustedDeviceRequest.swift
@@ -39,6 +39,7 @@ struct GrandSlamSMSAuthRequest: GrandSlamTwoFactorRequest {
 
     let loginData: GrandSlamLoginData
     let phoneNumberID: Int
+    var nonFTEU: Bool?
 
     var extraHeaders: [String: String] {
         [
@@ -47,9 +48,15 @@ struct GrandSlamSMSAuthRequest: GrandSlamTwoFactorRequest {
         ]
     }
 
+    private var phoneNumber: [String: Any] {
+        var phoneNumber: [String: Any] = ["id": phoneNumberID]
+        if let nonFTEU { phoneNumber["nonFTEU"] = nonFTEU }
+        return phoneNumber
+    }
+
     func content(anisetteData: AnisetteData) -> GrandSlamRequestContent {
         .put([
-            "phoneNumber": ["id": phoneNumberID],
+            "phoneNumber": phoneNumber,
             "mode": "sms",
         ], type: .json)
     }
diff --git a/Sources/XKit/GrandSlam/Requests/Concrete/GrandSlamValidateRequest.swift b/Sources/XKit/GrandSlam/Requests/Concrete/GrandSlamValidateRequest.swift
index b93c614..b9f1e13 100644
--- a/Sources/XKit/GrandSlam/Requests/Concrete/GrandSlamValidateRequest.swift
+++ b/Sources/XKit/GrandSlam/Requests/Concrete/GrandSlamValidateRequest.swift
@@ -34,6 +34,7 @@ struct GrandSlamValidateSMSRequest: GrandSlamTwoFactorRequest {
 
     let loginData: GrandSlamLoginData
     let phoneNumberID: Int
+    var nonFTEU: Bool?
     let verificationCode: String
 
     var extraHeaders: [String: String] {
@@ -43,10 +44,16 @@ struct GrandSlamValidateSMSRequest: GrandSlamTwoFactorRequest {
         ]
     }
 
+    private var phoneNumber: [String: Any] {
+        var phoneNumber: [String: Any] = ["id": phoneNumberID]
+        if let nonFTEU { phoneNumber["nonFTEU"] = nonFTEU }
+        return phoneNumber
+    }
+
     func content(anisetteData: AnisetteData) -> GrandSlamRequestContent {
         .post([
             "securityCode": ["code": verificationCode],
-            "phoneNumber": ["id": phoneNumberID],
+            "phoneNumber": phoneNumber,
             "mode": "sms",
         ], type: .json)
     }