diff --git a/launcher/LaunchController.cpp b/launcher/LaunchController.cpp
index 82c97ecf..190605fd 100644
--- a/launcher/LaunchController.cpp
+++ b/launcher/LaunchController.cpp
@@ -183,6 +183,19 @@ void LaunchController::login() {
                 emitFailed(errorString);
                 return;
             }
+            case AuthSession::GoneOrMigrated: {
+                auto errorString = tr("The account no longer exists on the servers. It may have been migrated, in which case please add the new account you migrated this one to.");
+                QMessageBox::warning(
+                    nullptr,
+                    tr("Account gone"),
+                    errorString,
+                    QMessageBox::StandardButton::Ok,
+                    QMessageBox::StandardButton::Ok
+                );
+                tryagain = false;
+                emitFailed(errorString);
+                return;
+            }
             case AuthSession::PlayableOffline: {
                 // we ask the user for a player name
                 bool ok = false;
diff --git a/launcher/minecraft/auth/AccountTask.cpp b/launcher/minecraft/auth/AccountTask.cpp
index c06be42b..d400ce8d 100644
--- a/launcher/minecraft/auth/AccountTask.cpp
+++ b/launcher/minecraft/auth/AccountTask.cpp
@@ -49,6 +49,8 @@ QString AccountTask::getStateMessage() const
         return tr("Failed to contact the authentication server.");
     case STATE_FAILED_HARD:
         return tr("Failed to authenticate.");
+    case STATE_FAILED_GONE:
+        return tr("Failed to authenticate. The account no longer exists.");
     default:
         return tr("...");
     }
@@ -62,7 +64,7 @@ void AccountTask::changeState(AccountTask::State newState, QString reason)
     {
         emitSucceeded();
     }
-    else if (newState == STATE_FAILED_HARD || newState == STATE_FAILED_SOFT)
+    else if (newState == STATE_FAILED_HARD || newState == STATE_FAILED_SOFT || newState == STATE_FAILED_GONE)
     {
         emitFailed(reason);
     }
diff --git a/launcher/minecraft/auth/AccountTask.h b/launcher/minecraft/auth/AccountTask.h
index fc3488eb..4f3bd52a 100644
--- a/launcher/minecraft/auth/AccountTask.h
+++ b/launcher/minecraft/auth/AccountTask.h
@@ -76,6 +76,7 @@ public:
         STATE_WORKING,
         STATE_FAILED_SOFT, //!< soft failure. this generally means the user auth details haven't been invalidated
         STATE_FAILED_HARD, //!< hard failure. auth is invalid
+        STATE_FAILED_GONE, //!< hard failure. auth is invalid, and the account no longer exists
         STATE_SUCCEEDED
     } m_accountState = STATE_CREATED;
 
diff --git a/launcher/minecraft/auth/AuthSession.h b/launcher/minecraft/auth/AuthSession.h
index d77435b8..f609d5d3 100644
--- a/launcher/minecraft/auth/AuthSession.h
+++ b/launcher/minecraft/auth/AuthSession.h
@@ -18,7 +18,8 @@ struct AuthSession
         RequiresOAuth,
         RequiresPassword,
         PlayableOffline,
-        PlayableOnline
+        PlayableOnline,
+        GoneOrMigrated
     } status = Undetermined;
 
     // client token
diff --git a/launcher/minecraft/auth/MinecraftAccount.cpp b/launcher/minecraft/auth/MinecraftAccount.cpp
index 4231d6b0..2d76f9ac 100644
--- a/launcher/minecraft/auth/MinecraftAccount.cpp
+++ b/launcher/minecraft/auth/MinecraftAccount.cpp
@@ -227,32 +227,60 @@ void MinecraftAccount::authFailed(QString reason)
     auto session = m_currentTask->getAssignedSession();
     // This is emitted when the yggdrasil tasks time out or are cancelled.
     // -> we treat the error as no-op
-    if (m_currentTask->accountState() == AccountTask::STATE_FAILED_SOFT)
-    {
-        if (session)
-        {
-            session->status = accountStatus() == Verified ? AuthSession::PlayableOffline : AuthSession::RequiresPassword;
-            session->auth_server_online = false;
-            fillSession(session);
+    switch (m_currentTask->accountState()) {
+        case AccountTask::STATE_FAILED_SOFT: {
+            if (session)
+            {
+                if(accountStatus() == Verified) {
+                    session->status = AuthSession::PlayableOffline;
+                }
+                else {
+                    if(data.type == AccountType::MSA) {
+                        session->status = AuthSession::RequiresOAuth;
+                    }
+                    else {
+                        session->status = AuthSession::RequiresPassword;
+                    }
+                }
+                session->auth_server_online = false;
+                fillSession(session);
+            }
         }
-    }
-    else
-    {
-        // FIXME: MSA ...
-        data.yggdrasilToken.token = QString();
-        data.yggdrasilToken.validity = Katabasis::Validity::None;
-        data.validity_ = Katabasis::Validity::None;
-        emit changed();
-        if (session)
-        {
-            if(data.type == AccountType::MSA) {
-                session->status = AuthSession::RequiresOAuth;
+        break;
+        case AccountTask::STATE_FAILED_HARD: {
+            // FIXME: MSA data clearing
+            data.yggdrasilToken.token = QString();
+            data.yggdrasilToken.validity = Katabasis::Validity::None;
+            data.validity_ = Katabasis::Validity::None;
+            emit changed();
+            if (session)
+            {
+                if(data.type == AccountType::MSA) {
+                    session->status = AuthSession::RequiresOAuth;
+                }
+                else {
+                    session->status = AuthSession::RequiresPassword;
+                }
+                session->auth_server_online = true;
+                fillSession(session);
             }
-            else {
-                session->status = AuthSession::RequiresPassword;
+        }
+        break;
+        case AccountTask::STATE_FAILED_GONE: {
+            data.validity_ = Katabasis::Validity::None;
+            emit changed();
+            if (session)
+            {
+                session->status = AuthSession::GoneOrMigrated;
+                session->auth_server_online = true;
+                fillSession(session);
             }
-            session->auth_server_online = true;
-            fillSession(session);
+        }
+        break;
+        case AccountTask::STATE_CREATED:
+        case AccountTask::STATE_WORKING:
+        case AccountTask::STATE_SUCCEEDED: {
+            // Not reachable here, as they are not failures.
         }
     }
     m_currentTask.reset();
diff --git a/launcher/minecraft/auth/flows/Yggdrasil.cpp b/launcher/minecraft/auth/flows/Yggdrasil.cpp
index 7cea059c..c2935d05 100644
--- a/launcher/minecraft/auth/flows/Yggdrasil.cpp
+++ b/launcher/minecraft/auth/flows/Yggdrasil.cpp
@@ -255,10 +255,17 @@ void Yggdrasil::processReply()
     case QNetworkReply::ContentAccessDenied:
     case QNetworkReply::ContentOperationNotPermittedError:
         break;
+    case QNetworkReply::ContentGoneError: {
+        changeState(
+            STATE_FAILED_GONE,
+            tr("The Mojang account no longer exists. It may have been migrated to a Microsoft account.")
+        );
+    }
     default:
-        changeState(STATE_FAILED_SOFT,
-                    tr("Authentication operation failed due to a network error: %1 (%2)")
-                        .arg(m_netReply->errorString()).arg(m_netReply->error()));
+        changeState(
+            STATE_FAILED_SOFT,
+            tr("Authentication operation failed due to a network error: %1 (%2)").arg(m_netReply->errorString()).arg(m_netReply->error())
+        );
         return;
     }
 
@@ -283,10 +290,10 @@ void Yggdrasil::processReply()
         }
         else
         {
-            changeState(STATE_FAILED_SOFT, tr("Failed to parse authentication server response "
-                                              "JSON response: %1 at offset %2.")
-                                               .arg(jsonError.errorString())
-                                               .arg(jsonError.offset));
+            changeState(
+                STATE_FAILED_SOFT,
+                tr("Failed to parse authentication server response JSON response: %1 at offset %2.").arg(jsonError.errorString()).arg(jsonError.offset)
+            );
             qCritical() << replyData;
         }
         return;
@@ -301,19 +308,18 @@ void Yggdrasil::processReply()
         // We were able to parse the server's response. Woo!
         // Call processError. If a subclass has overridden it then they'll handle their
         // stuff there.
-        qDebug() << "The request failed, but the server gave us an error message. "
-                        "Processing error.";
+        qDebug() << "The request failed, but the server gave us an error message. Processing error.";
         processError(doc.object());
     }
     else
     {
         // The server didn't say anything regarding the error. Give the user an unknown
         // error.
-        qDebug()
-            << "The request failed and the server gave no error message. Unknown error.";
-        changeState(STATE_FAILED_SOFT,
-                    tr("An unknown error occurred when trying to communicate with the "
-                       "authentication server: %1").arg(m_netReply->errorString()));
+        qDebug() << "The request failed and the server gave no error message. Unknown error.";
+        changeState(
+            STATE_FAILED_SOFT,
+            tr("An unknown error occurred when trying to communicate with the authentication server: %1").arg(m_netReply->errorString())
+        );
     }
 }
 
@@ -325,8 +331,13 @@ void Yggdrasil::processError(QJsonObject responseData)
 
     if (errorVal.isString() && errorMessageValue.isString())
     {
-        m_error = std::shared_ptr<Error>(new Error{
-            errorVal.toString(""), errorMessageValue.toString(""), causeVal.toString("")});
+        m_error = std::shared_ptr<Error>(
+            new Error {
+                errorVal.toString(""),
+                errorMessageValue.toString(""),
+                causeVal.toString("")
+            }
+        );
         changeState(STATE_FAILED_HARD, m_error->m_errorMessageVerbose);
     }
     else