feat(wallet): give new full-node wallets a BIP39 seed phrase + backup UI

New full-node wallets now get a real 24-word recovery phrase, and users can
reveal/back it up from Settings.

- Pass -usemnemonic=1 to dragonxd. The daemon reads it only inside
  GenerateNewSeed() when a wallet has no seed yet, so it is inert on existing
  wallets (safe to pass unconditionally) and makes every freshly-created
  wallet mnemonic-backed — its phrase is then exportable via z_exportmnemonic
  and portable to SDXLite/ObsidianDragonLite. (Existing/legacy wallets are
  unaffected and keep using the chat identity's z_exportkey fallback.)
- App::exportSeedPhrase() wraps z_exportmnemonic on the RPC worker with
  sodium_memzero wiping on every path; it flags the daemon's "not derived
  from a mnemonic" error as a legacy wallet rather than a failure.
- New "Back up seed phrase" modal (Settings -> Backup & Data, full-node
  gated): reveals the phrase in a numbered word grid, copy (45s clipboard
  auto-clear) + save-to-file (0600), wipes the secret on every close path
  incl. dismiss-mid-fetch. Shared ui/windows/seed_display.h grid helper.
- One-time nudge (settings flag seed_backup_reminded) toasts mnemonic-wallet
  users to back up their phrase; legacy wallets are not nagged.
- 15 new strings translated into all 8 languages (additive, 957->972 keys);
  CJK subset font rebuilt for the new glyphs.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

res/lang/de.json

@@ -641,6 +641,20 @@
     "sb_warming_up": "Aufwärmen...",
     "search_placeholder": "Suchen...",
     "security": "SICHERHEIT",
+    "seed_backup_button": "Wiederherstellungsphrase",
+    "seed_backup_close": "Schließen",
+    "seed_backup_copy": "Kopieren",
+    "seed_backup_intro": "Diese Wörter sind die Master-Sicherung Ihrer Wallet. Wer sie besitzt, kontrolliert Ihre Gelder.",
+    "seed_backup_load_failed": "Die Wiederherstellungsphrase konnte nicht geladen werden.",
+    "seed_backup_loading": "Ihre Wiederherstellungsphrase wird geladen…",
+    "seed_backup_locked": "Entsperren Sie Ihre Wallet, um ihre Wiederherstellungsphrase anzuzeigen.",
+    "seed_backup_none": "Diese Wallet ist älter als Wiederherstellungsphrasen und hat daher keine 24-Wort-Phrase. Sichern Sie sie stattdessen mit „Sicherung...“ oder durch den Export Ihrer privaten Schlüssel.",
+    "seed_backup_reminder": "Ihre Wallet hat eine 24-Wort-Wiederherstellungsphrase. Sichern Sie sie jetzt unter Einstellungen → Node & Sicherheit.",
+    "seed_backup_save": "In Datei speichern…",
+    "seed_backup_save_failed": "Konnte nicht schreiben ",
+    "seed_backup_saved": "Gespeichert unter ",
+    "seed_backup_title": "Wiederherstellungsphrase sichern",
+    "seed_backup_warning": "Schreiben Sie sie der Reihe nach auf, bewahren Sie sie offline auf und teilen oder fotografieren Sie sie niemals. Wenn Sie sie verlieren, können Ihre Gelder nicht wiederhergestellt werden.",
     "select_address": "Adresse auswählen...",
     "select_receiving_address": "Empfangsadresse auswählen...",
     "select_source_address": "Quelladresse auswählen...",
@@ -889,6 +903,7 @@
     "tt_save_ztx": "Z-Adresse-Transaktionsverlauf lokal für schnelleres Laden speichern",
     "tt_scan_themes": "Nach neuen Themes suchen.\\nTheme-Ordner ablegen in:\\n%s",
     "tt_scanline": "CRT-Scanlinieneffekt in der Konsole",
+    "tt_seed_backup": "Die 24-Wort-Wiederherstellungsphrase Ihrer Wallet anzeigen und sichern",
     "tt_set_pin": "Eine 4-8-stellige PIN für schnelles Entsperren festlegen",
     "tt_shield_mining": "Transparente Mining-Belohnungen an eine geschirmte Adresse verschieben",
     "tt_simple_bg": "Einen einfachen Verlauf für den Hintergrund verwenden\\nHotkey: Ctrl+Up",

res/lang/es.json

@@ -641,6 +641,20 @@
     "sb_warming_up": "Calentando...",
     "search_placeholder": "Buscar...",
     "security": "SEGURIDAD",
+    "seed_backup_button": "Frase de recuperación",
+    "seed_backup_close": "Cerrar",
+    "seed_backup_copy": "Copiar",
+    "seed_backup_intro": "Estas palabras son el respaldo maestro de tu cartera. Cualquiera que las tenga controla tus fondos.",
+    "seed_backup_load_failed": "No se pudo cargar la frase de recuperación.",
+    "seed_backup_loading": "Cargando tu frase de recuperación…",
+    "seed_backup_locked": "Desbloquea tu cartera para revelar su frase de recuperación.",
+    "seed_backup_none": "Esta cartera es anterior a las frases de recuperación, por lo que no tiene una frase de 24 palabras. Respáldala con «Respaldo...» o exportando tus claves privadas en su lugar.",
+    "seed_backup_reminder": "Tu cartera tiene una frase de recuperación de 24 palabras. Respáldala ahora en Configuración → Nodo y Seguridad.",
+    "seed_backup_save": "Guardar en archivo…",
+    "seed_backup_save_failed": "No se pudo escribir ",
+    "seed_backup_saved": "Guardado en ",
+    "seed_backup_title": "Respaldar frase de recuperación",
+    "seed_backup_warning": "Anótalas en orden, guárdalas sin conexión y nunca las compartas ni las fotografíes. Si las pierdes, tus fondos no se podrán recuperar.",
     "select_address": "Seleccionar dirección...",
     "select_receiving_address": "Seleccionar dirección de recepción...",
     "select_source_address": "Seleccionar dirección de origen...",
@@ -889,6 +903,7 @@
     "tt_save_ztx": "Almacenar historial de transacciones de z-address localmente para carga más rápida",
     "tt_scan_themes": "Buscar nuevos temas.\\nColoque carpetas de temas en:\\n%s",
     "tt_scanline": "Efecto de líneas de escaneo CRT en la consola",
+    "tt_seed_backup": "Muestra y respalda la frase de recuperación de 24 palabras de tu cartera",
     "tt_set_pin": "Establecer un PIN de 4-8 dígitos para desbloqueo rápido",
     "tt_shield_mining": "Mover recompensas de minería transparentes a una dirección blindada",
     "tt_simple_bg": "Usar un gradiente simple para el fondo\\nAtajo: Ctrl+Up",

res/lang/fr.json

@@ -641,6 +641,20 @@
     "sb_warming_up": "Démarrage...",
     "search_placeholder": "Rechercher...",
     "security": "SÉCURITÉ",
+    "seed_backup_button": "Phrase de récupération",
+    "seed_backup_close": "Fermer",
+    "seed_backup_copy": "Copier",
+    "seed_backup_intro": "Ces mots sont la sauvegarde principale de votre portefeuille. Quiconque les possède contrôle vos fonds.",
+    "seed_backup_load_failed": "Impossible de charger la phrase de récupération.",
+    "seed_backup_loading": "Chargement de votre phrase de récupération…",
+    "seed_backup_locked": "Déverrouillez votre portefeuille pour révéler sa phrase de récupération.",
+    "seed_backup_none": "Ce portefeuille est antérieur aux phrases de récupération, il n'a donc pas de phrase de 24 mots. Sauvegardez-le plutôt avec « Sauvegarde » ou en exportant vos clés privées.",
+    "seed_backup_reminder": "Votre portefeuille possède une phrase de récupération de 24 mots. Sauvegardez-la maintenant dans Paramètres → Nœud et sécurité.",
+    "seed_backup_save": "Enregistrer dans un fichier…",
+    "seed_backup_save_failed": "Impossible d'écrire ",
+    "seed_backup_saved": "Enregistré dans ",
+    "seed_backup_title": "Sauvegarder la phrase de récupération",
+    "seed_backup_warning": "Notez-les dans l'ordre, conservez-les hors ligne, et ne les partagez ni ne les photographiez jamais. Si vous les perdez, vos fonds ne pourront pas être récupérés.",
     "select_address": "Sélectionner une adresse...",
     "select_receiving_address": "Sélectionner une adresse de réception...",
     "select_source_address": "Sélectionner une adresse source...",
@@ -889,6 +903,7 @@
     "tt_save_ztx": "Stocker l'historique des transactions z-address localement pour un chargement plus rapide",
     "tt_scan_themes": "Rechercher de nouveaux thèmes.\\nPlacez les dossiers de thèmes dans :\\n%s",
     "tt_scanline": "Effet de lignes de balayage CRT dans la console",
+    "tt_seed_backup": "Afficher et sauvegarder la phrase de récupération de 24 mots de votre portefeuille",
     "tt_set_pin": "Définir un PIN de 4-8 chiffres pour un déverrouillage rapide",
     "tt_shield_mining": "Déplacer les récompenses de minage transparentes vers une adresse blindée",
     "tt_simple_bg": "Utiliser un dégradé simple pour l'arrière-plan\\nRaccourci : Ctrl+Up",

res/lang/ja.json

@@ -641,6 +641,20 @@
     "sb_warming_up": "ウォームアップ中...",
     "search_placeholder": "検索...",
     "security": "セキュリティ",
+    "seed_backup_button": "シードフレーズ",
+    "seed_backup_close": "閉じる",
+    "seed_backup_copy": "コピー",
+    "seed_backup_intro": "これらの単語はウォレットのマスターバックアップです。これらを持つ人は誰でもあなたの資金を管理できます。",
+    "seed_backup_load_failed": "シードフレーズを読み込めませんでした。",
+    "seed_backup_loading": "シードフレーズを読み込み中...",
+    "seed_backup_locked": "シードフレーズを表示するにはウォレットのロックを解除してください。",
+    "seed_backup_none": "このウォレットはシードフレーズより前のものなので、24単語のフレーズはありません。代わりに「バックアップ...」で、または秘密鍵をエクスポートしてバックアップしてください。",
+    "seed_backup_reminder": "ウォレットには24単語の復元シードフレーズがあります。今すぐ 設定 → ノードとセキュリティ でバックアップしてください。",
+    "seed_backup_save": "ファイルに保存...",
+    "seed_backup_save_failed": "書き込めませんでした: ",
+    "seed_backup_saved": "保存先: ",
+    "seed_backup_title": "シードフレーズをバックアップ",
+    "seed_backup_warning": "順番どおりに書き写し、オフラインで保管してください。決して共有や撮影をしないでください。紛失すると資金を復元できません。",
     "select_address": "アドレスを選択...",
     "select_receiving_address": "受信アドレスを選択...",
     "select_source_address": "送信元アドレスを選択...",
@@ -889,6 +903,7 @@
     "tt_save_ztx": "z-address トランザクション履歴をローカルに保存して高速読み込み",
     "tt_scan_themes": "新しいテーマをスキャン。\\nテーマフォルダーをここに配置：\\n%s",
     "tt_scanline": "コンソールでの CRT スキャンライン効果",
+    "tt_seed_backup": "ウォレットの24単語の復元シードフレーズを表示してバックアップします",
     "tt_set_pin": "クイックアンロック用の 4-8 桁 PIN を設定",
     "tt_shield_mining": "透明マイニング報酬をシールドアドレスに移動",
     "tt_simple_bg": "背景にシンプルなグラデーションを使用\\nホットキー：Ctrl+Up",

res/lang/ko.json

@@ -641,6 +641,20 @@
     "sb_warming_up": "워밍업 중...",
     "search_placeholder": "검색...",
     "security": "보안",
+    "seed_backup_button": "시드 문구",
+    "seed_backup_close": "닫기",
+    "seed_backup_copy": "복사",
+    "seed_backup_intro": "이 단어들은 지갑의 마스터 백업입니다. 이 단어들을 가진 사람은 누구나 당신의 자금을 통제할 수 있습니다.",
+    "seed_backup_load_failed": "시드 문구를 불러올 수 없습니다.",
+    "seed_backup_loading": "시드 문구를 불러오는 중…",
+    "seed_backup_locked": "시드 문구를 표시하려면 지갑의 잠금을 해제하세요.",
+    "seed_backup_none": "이 지갑은 시드 문구 도입 이전에 만들어져 24단어 문구가 없습니다. 대신 \"백업...\"을 사용하거나 개인 키를 내보내 백업하세요.",
+    "seed_backup_reminder": "지갑에 24단어 복구 시드 문구가 있습니다. 지금 설정 → 노드 및 보안에서 백업하세요.",
+    "seed_backup_save": "파일로 저장…",
+    "seed_backup_save_failed": "쓸 수 없습니다: ",
+    "seed_backup_saved": "저장됨: ",
+    "seed_backup_title": "시드 문구 백업",
+    "seed_backup_warning": "순서대로 종이에 적어 오프라인으로 보관하고, 절대 공유하거나 사진으로 찍지 마세요. 이 단어들을 잃어버리면 자금을 복구할 수 없습니다.",
     "select_address": "주소 선택...",
     "select_receiving_address": "수신 주소 선택...",
     "select_source_address": "보낼 주소 선택...",
@@ -889,6 +903,7 @@
     "tt_save_ztx": "z-address 거래 기록을 로컬에 저장하여 빠른 로딩",
     "tt_scan_themes": "새 테마 검색.\\n테마 폴더를 여기에 배치:\\n%s",
     "tt_scanline": "콘솔에서 CRT 스캔라인 효과",
+    "tt_seed_backup": "지갑의 24단어 복구 시드 문구를 표시하고 백업합니다",
     "tt_set_pin": "빠른 잠금 해제를 위한 4-8자리 PIN 설정",
     "tt_shield_mining": "투명 채굴 보상을 차폐 주소로 이동",
     "tt_simple_bg": "배경에 단순 그라데이션 사용\\n단축키: Ctrl+Up",

res/lang/pt.json

@@ -641,6 +641,20 @@
     "sb_warming_up": "Aquecendo...",
     "search_placeholder": "Pesquisar...",
     "security": "SEGURANÇA",
+    "seed_backup_button": "Frase de recuperação",
+    "seed_backup_close": "Fechar",
+    "seed_backup_copy": "Copiar",
+    "seed_backup_intro": "Estas palavras são o backup mestre da sua carteira. Qualquer pessoa que as tenha controla seus fundos.",
+    "seed_backup_load_failed": "Não foi possível carregar a frase de recuperação.",
+    "seed_backup_loading": "Carregando sua frase de recuperação…",
+    "seed_backup_locked": "Desbloqueie sua carteira para revelar sua frase de recuperação.",
+    "seed_backup_none": "Esta carteira é anterior às frases de recuperação, portanto não possui uma frase de 24 palavras. Faça o backup dela com \"Backup...\" ou exportando suas chaves privadas.",
+    "seed_backup_reminder": "Sua carteira tem uma frase de recuperação de 24 palavras. Faça o backup dela agora em Configurações → Nó e Segurança.",
+    "seed_backup_save": "Salvar em arquivo…",
+    "seed_backup_save_failed": "Não foi possível gravar ",
+    "seed_backup_saved": "Salvo em ",
+    "seed_backup_title": "Backup da frase de recuperação",
+    "seed_backup_warning": "Anote-as em ordem, guarde-as offline e nunca as compartilhe ou fotografe. Se você as perder, seus fundos não poderão ser recuperados.",
     "select_address": "Selecionar endereço...",
     "select_receiving_address": "Selecionar endereço de recebimento...",
     "select_source_address": "Selecionar endereço de origem...",
@@ -889,6 +903,7 @@
     "tt_save_ztx": "Armazenar histórico de transações z-address localmente para carregamento mais rápido",
     "tt_scan_themes": "Procurar novos temas.\\nColoque pastas de temas em:\\n%s",
     "tt_scanline": "Efeito de linhas de varredura CRT no console",
+    "tt_seed_backup": "Mostrar e fazer backup da frase de recuperação de 24 palavras da sua carteira",
     "tt_set_pin": "Definir um PIN de 4-8 dígitos para desbloqueio rápido",
     "tt_shield_mining": "Mover recompensas de mineração transparentes para um endereço blindado",
     "tt_simple_bg": "Usar um gradiente simples para o fundo\\nAtalho: Ctrl+Up",

res/lang/ru.json

@@ -641,6 +641,20 @@
     "sb_warming_up": "Прогрев...",
     "search_placeholder": "Поиск...",
     "security": "БЕЗОПАСНОСТЬ",
+    "seed_backup_button": "Сид-фраза",
+    "seed_backup_close": "Закрыть",
+    "seed_backup_copy": "Копировать",
+    "seed_backup_intro": "Эти слова — главная резервная копия вашего кошелька. Любой, у кого они есть, управляет вашими средствами.",
+    "seed_backup_load_failed": "Не удалось загрузить сид-фразу.",
+    "seed_backup_loading": "Загрузка вашей сид-фразы…",
+    "seed_backup_locked": "Разблокируйте кошелёк, чтобы показать его сид-фразу.",
+    "seed_backup_none": "Этот кошелёк создан до появления сид-фраз, поэтому у него нет фразы из 24 слов. Создайте резервную копию с помощью «Резервная копия...» или вместо этого экспортируйте свои приватные ключи.",
+    "seed_backup_reminder": "У вашего кошелька есть сид-фраза восстановления из 24 слов. Создайте её резервную копию прямо сейчас в Настройки → Узел и безопасность.",
+    "seed_backup_save": "Сохранить в файл…",
+    "seed_backup_save_failed": "Не удалось записать ",
+    "seed_backup_saved": "Сохранено в ",
+    "seed_backup_title": "Резервная копия сид-фразы",
+    "seed_backup_warning": "Запишите их по порядку, храните офлайн и никогда не делитесь ими и не фотографируйте их. Если вы их потеряете, ваши средства не удастся восстановить.",
     "select_address": "Выбрать адрес...",
     "select_receiving_address": "Выбрать адрес получения...",
     "select_source_address": "Выбрать адрес-источник...",
@@ -889,6 +903,7 @@
     "tt_save_ztx": "Хранить историю транзакций z-адреса локально для более быстрой загрузки",
     "tt_scan_themes": "Поиск новых тем.\\nРазместите папки тем в:\\n%s",
     "tt_scanline": "Эффект развёртки ЭЛТ в консоли",
+    "tt_seed_backup": "Показать и создать резервную копию сид-фразы восстановления вашего кошелька из 24 слов",
     "tt_set_pin": "Установить 4-8-значный PIN для быстрой разблокировки",
     "tt_shield_mining": "Перевести прозрачные вознаграждения за майнинг на экранированный адрес",
     "tt_simple_bg": "Использовать простой градиент для фона\\nГорячая клавиша: Ctrl+Up",

res/lang/zh.json

@@ -641,6 +641,20 @@
     "sb_warming_up": "正在预热...",
     "search_placeholder": "搜索...",
     "security": "安全",
+    "seed_backup_button": "助记词",
+    "seed_backup_close": "关闭",
+    "seed_backup_copy": "复制",
+    "seed_backup_intro": "这些词是您钱包的主备份。任何拥有它们的人都能控制您的资金。",
+    "seed_backup_load_failed": "无法加载助记词。",
+    "seed_backup_loading": "正在加载您的助记词…",
+    "seed_backup_locked": "解锁您的钱包以显示其助记词。",
+    "seed_backup_none": "此钱包早于助记词功能，因此没有 24 词助记词。请改用“备份钱包”或导出私钥来备份它。",
+    "seed_backup_reminder": "您的钱包有一个 24 词恢复助记词。请立即在“设置 → 节点与安全”中备份它。",
+    "seed_backup_save": "保存到文件…",
+    "seed_backup_save_failed": "无法写入 ",
+    "seed_backup_saved": "已保存到 ",
+    "seed_backup_title": "备份助记词",
+    "seed_backup_warning": "请按顺序将它们抄写下来，离线保存，切勿分享或拍照。一旦丢失，您的资金将无法恢复。",
     "select_address": "选择地址...",
     "select_receiving_address": "选择接收地址...",
     "select_source_address": "选择来源地址...",
@@ -889,6 +903,7 @@
     "tt_save_ztx": "将 z-address 交易历史存储在本地以加快加载速度",
     "tt_scan_themes": "扫描新主题。\\n将主题文件夹放在：\\n%s",
     "tt_scanline": "控制台中的 CRT 扫描线效果",
+    "tt_seed_backup": "显示并备份您钱包的 24 词恢复助记词",
     "tt_set_pin": "设置 4-8 位 PIN 以快速解锁",
     "tt_shield_mining": "将透明挖矿奖励转移到屏蔽地址",
     "tt_simple_bg": "使用简单渐变作为背景\\n快捷键：Ctrl+Up",

src/app.cpp

@@ -33,6 +33,7 @@
 #include "ui/windows/network_tab.h"
 #include "ui/windows/console_command_executor.h"
 #include "ui/windows/explorer_tab.h"
+#include "ui/windows/seed_display.h"
 #include "ui/windows/market_tab.h"
 #include "ui/windows/settings_window.h"
 #include "ui/windows/about_dialog.h"
@@ -715,6 +716,9 @@ void App::update()
     // it can act; compiled away when the feature is off (constexpr gate inside).
     maybeProvisionChatIdentity();
 
+    // One-time reminder to back up the wallet's seed phrase (mnemonic wallets only).
+    maybeRemindSeedBackup();
+
     // Auto-lock check (only when connected + encrypted + unlocked)
     if (state_.connected && state_.isUnlocked()) {
         checkAutoLock();
@@ -1893,6 +1897,10 @@ void App::render()
         renderBackupDialog();
     }
 
+    if (show_seed_backup_) {
+        renderSeedBackupDialog();
+    }
+
     // Security overlay dialogs (encrypt, decrypt, PIN) are rendered AFTER ImGui::End()
     // to ensure they appear on top of all other content
 
@@ -2921,7 +2929,103 @@ void App::renderBackupDialog()
         backup_status_.clear();
         s_backup_confirm_overwrite = false;
     }
-    
+
+    ui::material::EndOverlayDialog();
+}
+
+void App::renderSeedBackupDialog()
+{
+    // Wipe the revealed phrase and reset the dialog's state.
+    auto closeAndWipe = [this]() {
+        if (!seed_backup_phrase_.empty())
+            sodium_memzero(&seed_backup_phrase_[0], seed_backup_phrase_.size());
+        seed_backup_phrase_.clear();
+        seed_backup_status_.clear();
+        seed_backup_fetch_started_ = false;
+        seed_backup_loading_ = false;
+        seed_backup_no_mnemonic_ = false;
+        show_seed_backup_ = false;
+    };
+
+    // Kick off the async z_exportmnemonic fetch once, and only while unlocked.
+    if (!seed_backup_fetch_started_ && !state_.isLocked()) {
+        seed_backup_fetch_started_ = true;
+        seed_backup_loading_ = true;
+        seed_backup_no_mnemonic_ = false;
+        seed_backup_status_.clear();
+        exportSeedPhrase([this](bool ok, bool noMnemonic, const std::string& phrase,
+                                const std::string& error) {
+            if (!show_seed_backup_) return;  // dialog closed while the fetch was in flight
+            seed_backup_loading_ = false;
+            if (ok) {
+                seed_backup_phrase_ = phrase;  // working copy — wiped on close
+            } else if (noMnemonic) {
+                seed_backup_no_mnemonic_ = true;
+            } else {
+                seed_backup_status_ = error.empty() ? std::string(TR("seed_backup_load_failed")) : error;
+            }
+        });
+    }
+
+    if (!ui::material::BeginOverlayDialog(TR("seed_backup_title"), &show_seed_backup_, 540.0f, 0.94f)) {
+        // Dismissed (Esc / outside click / X) — scrub the revealed secret.
+        if (seed_backup_fetch_started_) closeAndWipe();
+        return;
+    }
+
+    ui::material::Type().text(ui::material::TypeStyle::H6, TR("seed_backup_title"));
+    ImGui::Dummy(ImVec2(0, ui::Layout::spacingSm()));
+
+    if (state_.isLocked()) {
+        ImGui::TextWrapped("%s", TR("seed_backup_locked"));
+    } else if (seed_backup_loading_) {
+        ImGui::TextWrapped("%s", TR("seed_backup_loading"));
+    } else if (seed_backup_no_mnemonic_) {
+        ImGui::TextWrapped("%s", TR("seed_backup_none"));
+    } else if (!seed_backup_phrase_.empty()) {
+        ImGui::TextWrapped("%s", TR("seed_backup_intro"));
+        ImGui::Spacing();
+        ImGui::PushStyleColor(ImGuiCol_Text, ui::material::Error());
+        ImGui::TextWrapped("%s", TR("seed_backup_warning"));
+        ImGui::PopStyleColor();
+        ImGui::Spacing();
+        ui::RenderSeedWordGrid(ui::SplitSeedWords(seed_backup_phrase_));
+        ImGui::Spacing();
+        if (!seed_backup_status_.empty()) {
+            ImGui::TextColored(ImVec4(0.3f, 0.8f, 0.3f, 1.0f), "%s", seed_backup_status_.c_str());
+            ImGui::Spacing();
+        }
+        ImGui::Separator();
+        if (ui::material::StyledButton(TR("seed_backup_copy"), ImVec2(120, 0))) {
+            copySecretToClipboard(seed_backup_phrase_);
+        }
+        ImGui::SameLine();
+        if (ui::material::StyledButton(TR("seed_backup_save"), ImVec2(150, 0))) {
+            std::string path = util::Platform::getConfigDir() + "/dragonx-seed-backup.txt";
+            std::string content = seed_backup_phrase_ + "\n";
+            const bool ok = util::Platform::writeFileAtomically(path, content,
+                                                               /*restrictPermissions=*/true);
+            sodium_memzero(&content[0], content.size());
+            seed_backup_status_ = (ok ? std::string(TR("seed_backup_saved"))
+                                      : std::string(TR("seed_backup_save_failed"))) + path;
+        }
+        ImGui::SameLine();
+        if (ui::material::StyledButton(TR("seed_backup_close"), ImVec2(120, 0))) {
+            closeAndWipe();
+            ui::material::EndOverlayDialog();
+            return;
+        }
+        ui::material::EndOverlayDialog();
+        return;
+    } else if (!seed_backup_status_.empty()) {
+        ImGui::TextColored(ImVec4(0.8f, 0.3f, 0.3f, 1.0f), "%s", seed_backup_status_.c_str());
+    }
+
+    ImGui::Spacing();
+    ImGui::Separator();
+    if (ui::material::StyledButton(TR("seed_backup_close"), ImVec2(120, 0))) {
+        closeAndWipe();
+    }
     ui::material::EndOverlayDialog();
 }
 

src/app.h

@@ -295,6 +295,13 @@ public:
     
     // Wallet backup
     void backupWallet(const std::string& destination, std::function<void(bool, const std::string&)> callback);
+    // Export the wallet's BIP39 seed phrase (z_exportmnemonic). The callback receives
+    // (ok, noMnemonic, phrase, error): ok+phrase on success; noMnemonic=true when the
+    // wallet's seed is not mnemonic-derived (legacy wallet). Full-node only; the phrase
+    // is a secret and is wiped after the callback returns.
+    void exportSeedPhrase(std::function<void(bool ok, bool noMnemonic,
+                                             const std::string& phrase,
+                                             const std::string& error)> callback);
 
     // Transaction operations
     void sendTransaction(const std::string& from, const std::string& to,
@@ -344,6 +351,7 @@ public:
     void showImportKeyDialog() { show_import_key_ = true; }
     void showExportKeyDialog() { show_export_key_ = true; }
     void showBackupDialog() { show_backup_ = true; }
+    void showSeedBackupDialog() { show_seed_backup_ = true; }
     void showAboutDialog() { show_about_ = true; }
     
     // Legacy tab compat — maps int to NavPage
@@ -599,6 +607,9 @@ private:
     // variants); derives via deriveChatIdentityFromSecret and wipes the secret. No-op when the
     // feature is off, already provisioned, in flight, or unavailable.
     void maybeProvisionChatIdentity();
+    // One-time nudge: on a full-node wallet that has a mnemonic, remind the user (once per
+    // install) to back up their seed phrase. Cheap early-outs keep it idle until it can act.
+    void maybeRemindSeedBackup();
     void provisionChatIdentityFromSecret(std::string secret);
     std::string chatReplyZaddr();                                // a stable (persisted) wallet z-addr for chat
     std::string generateChatLocalId(const char* prefix, int numBytes) const;  // unique echo id / cid
@@ -656,6 +667,16 @@ private:
     bool show_import_key_ = false;
     bool show_export_key_ = false;
     bool show_backup_ = false;
+    bool show_seed_backup_ = false;
+
+    // Seed-phrase backup dialog state. seed_backup_phrase_ holds a SECRET (the revealed
+    // mnemonic) and is wiped with sodium_memzero when the dialog closes.
+    std::string seed_backup_phrase_;
+    std::string seed_backup_status_;
+    bool seed_backup_fetch_started_ = false;
+    bool seed_backup_loading_ = false;
+    bool seed_backup_no_mnemonic_ = false;
+    bool seed_backup_reminder_in_flight_ = false;  // guards the one-time backup nudge probe
 
     // Embedded daemon state
     bool use_embedded_daemon_ = wallet::supportsEmbeddedDaemon(wallet::currentWalletCapabilities());
@@ -918,6 +939,7 @@ private:
     void renderImportKeyDialog();
     void renderExportKeyDialog();
     void renderBackupDialog();
+    void renderSeedBackupDialog();  // full-node "Back up seed phrase" modal (z_exportmnemonic)
     void renderFirstRunWizard();
     void renderLockScreen();
     void renderEncryptWalletDialog();

src/app_network.cpp

@@ -2863,6 +2863,69 @@ void App::importPrivateKey(const std::string& rawKey, std::function<void(bool, c
     });
 }
 
+void App::exportSeedPhrase(std::function<void(bool, bool, const std::string&, const std::string&)> callback)
+{
+    if (!state_.connected || !rpc_ || !worker_) {
+        if (callback) callback(false, false, std::string(), "Not connected to the daemon.");
+        return;
+    }
+    worker_->post([this, callback]() -> rpc::RPCWorker::MainCb {
+        std::string phrase;   // SECRET — wiped after the callback runs
+        std::string err;
+        bool ok = false;
+        bool noMnemonic = false;
+        rpc::RPCClient::TraceScope trace("Settings / Export seed phrase");
+        try {
+            auto response = rpc_->call("z_exportmnemonic");
+            if (response.contains("mnemonic") && response["mnemonic"].is_string()) {
+                auto& m = response["mnemonic"].get_ref<std::string&>();
+                phrase = m;
+                if (!m.empty()) sodium_memzero(&m[0], m.size());  // scrub the json's own copy
+                ok = !phrase.empty();
+            } else {
+                err = "The daemon returned no seed phrase.";
+            }
+        } catch (const rpc::RpcError& e) {
+            err = e.what();
+            // The daemon errors with this specific message when the wallet's seed is not
+            // mnemonic-derived (a legacy wallet). Any other error (e.g. locked) stays generic.
+            if (err.find("not derived from a mnemonic") != std::string::npos)
+                noMnemonic = true;
+        } catch (const std::exception& e) {
+            err = e.what();
+        }
+        return [callback, ok, noMnemonic, phrase = std::move(phrase), err]() mutable {
+            if (callback) callback(ok, noMnemonic, phrase, err);
+            if (!phrase.empty()) sodium_memzero(&phrase[0], phrase.size());
+        };
+    });
+}
+
+// One-time nudge to back up the seed phrase on a mnemonic-backed full-node wallet. Fires at
+// most one z_exportmnemonic probe per install; the phrase is not retained (the probe only
+// learns whether a mnemonic exists). Legacy (non-mnemonic) wallets are not nagged.
+void App::maybeRemindSeedBackup()
+{
+    if (lite_wallet_) return;                                  // lite has its own seed UX
+    if (!settings_ || settings_->getSeedBackupReminded()) return;
+    if (!state_.connected || !state_.encryption_state_known) return;
+    if (state_.isLocked()) return;                            // wait until unlocked to read it
+    if (seed_backup_reminder_in_flight_) return;
+    seed_backup_reminder_in_flight_ = true;
+    exportSeedPhrase([this](bool ok, bool noMnemonic, const std::string& /*phrase*/,
+                            const std::string& /*error*/) {
+        seed_backup_reminder_in_flight_ = false;
+        // Only mark "reminded" once we have a definitive answer, so a transient failure retries
+        // next session rather than silently suppressing the reminder forever.
+        if (ok || noMnemonic) {
+            settings_->setSeedBackupReminded(true);
+            settings_->save();
+        }
+        if (ok)
+            ui::Notifications::instance().info(TR("seed_backup_reminder"), 12.0f);
+    });
+}
+
 void App::backupWallet(const std::string& destination, std::function<void(bool, const std::string&)> callback)
 {
     if (!state_.connected || !rpc_) {

src/config/settings.cpp

@@ -199,6 +199,7 @@ bool Settings::load(const std::string& path)
             }
         }
         loadScalar(j, "wizard_completed", wizard_completed_);
+        loadScalar(j, "seed_backup_reminded", seed_backup_reminded_);
         loadScalar(j, "auto_lock_timeout", auto_lock_timeout_);
         loadScalar(j, "unlock_duration", unlock_duration_);
         loadScalar(j, "pin_enabled", pin_enabled_);
@@ -432,6 +433,7 @@ bool Settings::save(const std::string& path)
         j["address_meta"] = meta_obj;
     }
     j["wizard_completed"] = wizard_completed_;
+    j["seed_backup_reminded"] = seed_backup_reminded_;
     j["auto_lock_timeout"] = auto_lock_timeout_;
     j["unlock_duration"] = unlock_duration_;
     j["pin_enabled"] = pin_enabled_;

src/config/settings.h

@@ -246,6 +246,10 @@ public:
     bool getWizardCompleted() const { return wizard_completed_; }
     void setWizardCompleted(bool v) { wizard_completed_ = v; }
 
+    // Whether the one-time "back up your seed phrase" reminder has already been shown.
+    bool getSeedBackupReminded() const { return seed_backup_reminded_; }
+    void setSeedBackupReminded(bool v) { seed_backup_reminded_ = v; }
+
     // Security — auto-lock timeout (seconds; 0 = disabled)
     int getAutoLockTimeout() const { return auto_lock_timeout_; }
     void setAutoLockTimeout(int seconds) { auto_lock_timeout_ = seconds; }
@@ -444,6 +448,7 @@ private:
     std::set<std::string> favorite_addresses_;
     std::map<std::string, AddressMeta> address_meta_;
     bool wizard_completed_ = false;
+    bool seed_backup_reminded_ = false;
     int auto_lock_timeout_ = 900;   // 15 minutes
     int unlock_duration_ = 600;     // 10 minutes
     bool pin_enabled_ = false;

src/daemon/embedded_daemon.cpp

@@ -212,6 +212,11 @@ std::vector<std::string> EmbeddedDaemon::getChainParams()
         "-addnode=node4.dragonx.is",
         "-experimentalfeatures",
         "-developerencryptwallet",
+        // Create fresh wallets from a BIP39 mnemonic so their 24-word phrase can be
+        // exported (z_exportmnemonic) and is portable to SDXLite/ObsidianDragonLite.
+        // The daemon reads this ONLY inside GenerateNewSeed() when a wallet has no seed
+        // yet, so it is inert on existing wallets — safe to pass unconditionally.
+        "-usemnemonic=1",
         dbcache_arg
     };
 }

src/ui/pages/settings_page.cpp

@@ -1304,8 +1304,10 @@ void RenderSettingsPage(App* app) {
                 naturalW += ImGui::CalcTextSize(r1[i]).x + btnPadX;
             float wizW = showFullNodeLifecycleActions ? ImGui::CalcTextSize(wizLabel).x + btnPadX : 0.0f;
             float bsW = showFullNodeLifecycleActions ? ImGui::CalcTextSize(bsLabel).x + btnPadX : 0.0f;
+            // Full-node-only "Seed phrase" button trails the Backup button (see below).
+            float seedW = showFullNodeLifecycleActions ? ImGui::CalcTextSize(TR("seed_backup_button")).x + btnPadX : 0.0f;
             float totalW = naturalW + sp * 5;
-            if (showFullNodeLifecycleActions) totalW += wizW + bsW + sp * 2;
+            if (showFullNodeLifecycleActions) totalW += wizW + bsW + seedW + sp * 3;
 
             float scale = (totalW > contentW) ? contentW / totalW : 1.0f;
             if (scale < 1.0f) ImGui::SetWindowFontScale(scale);
@@ -1326,6 +1328,13 @@ void RenderSettingsPage(App* app) {
             if (TactileButton(r1[3], ImVec2(0, 0), btnFont))
                 app->showBackupDialog();
             if (ImGui::IsItemHovered()) material::Tooltip("%s", t1[3]);
+            if (showFullNodeLifecycleActions) {
+                // Back up the wallet's BIP39 seed phrase (full-node mnemonic wallets).
+                ImGui::SameLine(0, scaledSp);
+                if (TactileButton(TR("seed_backup_button"), ImVec2(0, 0), btnFont))
+                    app->showSeedBackupDialog();
+                if (ImGui::IsItemHovered()) material::Tooltip("%s", TR("tt_seed_backup"));
+            }
             ImGui::SameLine(0, scaledSp);
             if (TactileButton(r1[4], ImVec2(0, 0), btnFont))
                 ExportTransactionsDialog::show();

src/ui/windows/seed_display.h

@@ -0,0 +1,46 @@
+#pragma once
+
+// Shared helpers for rendering a BIP39 seed phrase as a numbered word grid and for
+// splitting a whitespace-separated phrase into words. Used by the full-node seed-phrase
+// backup dialog and the "migrate to a seed wallet" flow so both present the phrase the
+// same way the lite welcome wizard does.
+
+#include <cstdio>
+#include <string>
+#include <vector>
+
+#include "imgui.h"
+
+namespace dragonx {
+namespace ui {
+
+// Split a whitespace-separated seed phrase into its individual words.
+inline std::vector<std::string> SplitSeedWords(const std::string& phrase)
+{
+    std::vector<std::string> words;
+    std::string cur;
+    for (char c : phrase) {
+        if (c == ' ' || c == '\t' || c == '\n' || c == '\r') {
+            if (!cur.empty()) { words.push_back(cur); cur.clear(); }
+        } else {
+            cur.push_back(c);
+        }
+    }
+    if (!cur.empty()) words.push_back(cur);
+    return words;
+}
+
+// Render the words as a numbered 4-column grid (matches the lite welcome wizard layout).
+inline void RenderSeedWordGrid(const std::vector<std::string>& words, float colSpacingPx = 130.0f)
+{
+    for (size_t i = 0; i < words.size(); ++i) {
+        char cell[96];
+        std::snprintf(cell, sizeof(cell), "%2zu. %s", i + 1, words[i].c_str());
+        ImGui::TextUnformatted(cell);
+        if ((i % 4) != 3 && i + 1 < words.size())
+            ImGui::SameLine(((i % 4) + 1) * colSpacingPx);
+    }
+}
+
+}  // namespace ui
+}  // namespace dragonx

src/util/i18n.cpp

@@ -233,6 +233,22 @@ void I18n::loadBuiltinEnglish()
         strings_["chat_toast_compose_failed"] = "Could not compose the message (too long?).";
         strings_["chat_toast_request_compose_failed"] = "Could not compose the contact request (invalid address / text?).";
         strings_["chat_toast_request_queued"] = "Contact request queued.";
+        // Seed-phrase backup (full-node)
+        strings_["seed_backup_button"] = "Seed phrase";
+        strings_["tt_seed_backup"] = "Show and back up your wallet's 24-word recovery seed phrase";
+        strings_["seed_backup_title"] = "Back up seed phrase";
+        strings_["seed_backup_intro"] = "These words are the master backup of your wallet. Anyone who has them controls your funds.";
+        strings_["seed_backup_warning"] = "Write them down in order, store them offline, and never share or photograph them. If you lose them, your funds cannot be recovered.";
+        strings_["seed_backup_loading"] = "Loading your seed phrase…";
+        strings_["seed_backup_locked"] = "Unlock your wallet to reveal its seed phrase.";
+        strings_["seed_backup_none"] = "This wallet predates seed phrases, so it has no 24-word phrase. Back it up with \"Backup wallet\" or by exporting your private keys instead.";
+        strings_["seed_backup_load_failed"] = "Could not load the seed phrase.";
+        strings_["seed_backup_copy"] = "Copy";
+        strings_["seed_backup_save"] = "Save to file…";
+        strings_["seed_backup_saved"] = "Saved to ";
+        strings_["seed_backup_save_failed"] = "Could not write ";
+        strings_["seed_backup_close"] = "Close";
+        strings_["seed_backup_reminder"] = "Your wallet has a 24-word recovery seed phrase. Back it up now in Settings → Node & Security.";
         strings_["contacts_search_placeholder"] = "Search contacts...";
         strings_["contacts_search_no_match"] = "No matching contacts";
         strings_["address_book_confirm_delete"] = "Confirm delete?";