diff --git a/CHANGELOG.md b/CHANGELOG.md
index d7c701f3..7e9a7d89 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,12 @@
 
 ## [Unreleased]
 
+## [v0.51.642] — 2026-06-25 — Release WW (a failed steer now shows why, with Retry / Dismiss)
+
+### Fixed
+
+- **When a mid-turn steer can't be delivered, the composer no longer dead-ends on a generic toast.** A `/steer` (or busy-mode auto-fallback) that failed previously surfaced one of two vague toasts and restored your draft, with no explanation and no way forward — in the auto-fallback case this could trap you in a bounce loop. Each of the distinct failure reasons (agent not running, no cached agent, stream ended, session not found, agent lacks steer, network/steer error) now maps to a specific message, shown in a small recovery bar above the composer with **Retry** and **Dismiss** actions. The bar's buttons are theme-aware (readable in both light and dark, including on mobile). Thanks @rodboev. (#4850, closes #4749)
+
 ## [v0.51.641] — 2026-06-25 — Release WV (disabled plugins read as disabled in dark mode, active ones sort first)
 
 ### Fixed
diff --git a/static/commands.js b/static/commands.js
index 63bf57c2..49b484cd 100644
--- a/static/commands.js
+++ b/static/commands.js
@@ -1216,20 +1216,12 @@ async function cmdSteer(args){
   await _trySteer(msg, /*explicitSteer=*/true);
 }
 
-/**
- * Shared implementation for /steer and the busy_input_mode='steer' path.
- *
- * Tries the real steer endpoint first. On any non-accept response (no cached
- * agent, agent lacks steer, stream dead, etc.) it restores the draft and keeps
- * the active stream running. Steer belongs to the active run; a failed Steer
- * must not be silently upgraded into Queue, Interrupt, or Stop-and-send.
- *
- * @param {string} msg - The steer text.
- * @param {boolean} explicitSteer - True if the user explicitly invoked /steer
- *   (vs the busy-mode auto-fallback). Affects toast wording and draft restore.
- * @returns {Promise<boolean>} true when the steer was delivered, false when the
- *   draft was restored and the active stream was left untouched.
- */
+function _steerFailureMessageKey(fallback) {
+  const key = 'steer_fail_' + (fallback || 'unknown');
+  return (typeof LOCALES !== 'undefined' && LOCALES.en && LOCALES.en[key])
+    ? key : 'steer_fail_unknown';
+}
+
 function _showSteerIndicator(text){
   const inner=document.getElementById('msgInner');
   if(!inner) return;
@@ -1250,6 +1242,49 @@ function _showSteerIndicator(text){
   if(typeof scrollToBottom==='function') scrollToBottom();
 }
 
+function _showSteerRecovery(msg, explicitSteer, fallback) {
+  const inner = document.getElementById('msgInner');
+  if (!inner) return;
+  const old = inner.querySelector('.steer-recovery');
+  if (old) old.remove();
+  const el = document.createElement('div');
+  el.className = 'steer-recovery';
+  const label = document.createElement('span');
+  label.className = 'steer-recovery-label';
+  label.textContent = t(_steerFailureMessageKey(fallback));
+  el.appendChild(label);
+  const retryBtn = document.createElement('button');
+  retryBtn.className = 'steer-recovery-retry';
+  retryBtn.textContent = t('steer_recovery_retry');
+  retryBtn.addEventListener('click', () => {
+    el.remove();
+    void _trySteer(msg, explicitSteer).catch(console.error);
+  });
+  el.appendChild(retryBtn);
+  const dismissBtn = document.createElement('button');
+  dismissBtn.className = 'steer-recovery-dismiss';
+  dismissBtn.textContent = t('steer_recovery_dismiss');
+  dismissBtn.addEventListener('click', () => el.remove());
+  el.appendChild(dismissBtn);
+  inner.appendChild(el);
+  if (typeof scrollToBottom === 'function') scrollToBottom();
+}
+
+/**
+ * Shared implementation for /steer and the busy_input_mode='steer' path.
+ *
+ * Tries the real steer endpoint first. On any non-accept response (no cached
+ * agent, agent lacks steer, stream dead, etc.) it restores the draft and keeps
+ * the active stream running. Steer belongs to the active run; a failed Steer
+ * must not be silently upgraded into Queue, Interrupt, or Stop-and-send.
+ *
+ * @param {string} msg - The steer text.
+ * @param {boolean} explicitSteer - True if the user explicitly invoked /steer
+ *   (vs the busy-mode auto-fallback). Affects draft restore prefix only;
+ *   toast wording is determined by the failure reason code.
+ * @returns {Promise<boolean>} true when the steer was delivered, false when the
+ *   draft was restored and the active stream was left untouched.
+ */
 async function _trySteer(msg, explicitSteer){
   let result=null;
   try{
@@ -1279,11 +1314,9 @@ async function _trySteer(msg, explicitSteer){
     if(typeof autoResize==='function')autoResize();
   }
   if(typeof renderTray==='function')renderTray();
-  if(explicitSteer){
-    showToast(t('cmd_steer_fallback'),3500);
-  } else {
-    showToast(t('busy_steer_fallback'),3500);
-  }
+  const fallbackCode = result && result.fallback;
+  showToast(t(_steerFailureMessageKey(fallbackCode)), 3500);
+  _showSteerRecovery(msg, explicitSteer, fallbackCode);
   return false;
 }
 
diff --git a/static/i18n.js b/static/i18n.js
index cc450645..62f4c719 100644
--- a/static/i18n.js
+++ b/static/i18n.js
@@ -1,4 +1,4 @@
-// ── i18n: locale bundles and t() helper ──────────────────────────────────────
+// ── i18n: locale bundles and t() helper ──────────────────────────────────────
 // To add a new language: add an entry to LOCALES below with all keys translated.
 // The language code must match a valid BCP 47 tag (used for speech recognition).
 // Keys missing in a non-English locale fall back to English automatically.
@@ -298,6 +298,16 @@ const LOCALES = {
     cmd_steer_delivered: 'Steer delivered — agent will see it on its next tool result',
     steer_leftover_queued: 'Steer queued for next turn',
     busy_steer_fallback: 'Steer unavailable — draft restored',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: 'Interrupted — sending new message',
     settings_label_busy_input_mode: 'Busy input mode',
     settings_desc_busy_input_mode: 'Controls what happens when you send a message while the agent is running. Queue waits; Interrupt cancels and starts fresh; Steer injects a correction mid-turn without interrupting. If Steer is unavailable, the draft is restored so you can choose the next action.',
@@ -1884,6 +1894,16 @@ const LOCALES = {
     cmd_steer_delivered: "Steer consegnato — l'agente lo vedrà al prossimo risultato strumento",
     steer_leftover_queued: 'Steer in coda per il prossimo turno',
     busy_steer_fallback: 'Steer non disponibile — bozza ripristinata',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: 'Interrotto — invio nuovo messaggio',
     settings_label_busy_input_mode: 'Modalità input occupato',
     settings_desc_busy_input_mode: "Controlla cosa succede quando invii un messaggio mentre l'agente è in esecuzione. Coda attende; Interrompi annulla e ricomincia; Steer inietta una correzione a metà turno senza interrompere (fallback a coda se agente o stream non disponibili).",
@@ -3461,6 +3481,16 @@ const LOCALES = {
     cmd_steer_delivered: 'ステア送信完了 — 次のツール結果でエージェントが認識します',
     steer_leftover_queued: 'ステアを次のターンへキュー',
     busy_steer_fallback: 'ステア利用不可 — 下書きを復元しました',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: '中断 — 新しいメッセージを送信中',
     settings_label_busy_input_mode: 'ビジー時の入力モード',
     settings_desc_busy_input_mode: 'エージェント実行中にメッセージを送信した時の動作を制御します。Queue は待機、Interrupt はキャンセルして再開、Steer は中断せずにターン中に修正を注入します (エージェントやストリームが利用不可ならキューにフォールバック)。',
@@ -4989,6 +5019,16 @@ const LOCALES = {
     cmd_steer_delivered: 'Steer доставлен — агент увидит его в следующем ответе инструмента',
     steer_leftover_queued: 'Steer поставлен в очередь на следующий ход',
     busy_steer_fallback: 'Steer недоступен — черновик восстановлен',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: 'Прервано — отправка нового сообщения',
     settings_label_busy_input_mode: 'Режим ввода при занятости',
     settings_desc_busy_input_mode: 'Определяет поведение при отправке сообщения во время работы агента. Очередь ждёт; Прерывание отменяет и начинает заново; Steer внедряет коррекцию без прерывания.',
@@ -6553,6 +6593,16 @@ const LOCALES = {
     cmd_steer_delivered: 'Steer entregado \u2014 el agente lo ver\u00e1 en su pr\u00f3ximo resultado de herramienta',
     steer_leftover_queued: 'Steer en cola para el pr\u00f3ximo turno',
     busy_steer_fallback: 'Steer no disponible — borrador restaurado',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: 'Interrumpido \u2014 enviando nuevo mensaje',
     settings_label_busy_input_mode: 'Modo de entrada ocupada',
     settings_desc_busy_input_mode: 'Controla qué sucede al enviar mensajes mientras el agente está activo. Cola espera; Interrumpir cancela y empieza de nuevo; Steer inyecta una corrección sin interrumpir (usa cola si el agente no está disponible).',
@@ -8038,6 +8088,16 @@ const LOCALES = {
     cmd_steer_delivered: 'Steer geliefert \u2014 der Agent sieht es bei seinem n\u00e4chsten Tool-Ergebnis',
     steer_leftover_queued: 'Steer f\u00fcr n\u00e4chsten Durchgang eingereiht',
     busy_steer_fallback: 'Steer nicht verf\u00fcgbar \u2014 Entwurf wiederhergestellt',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: 'Unterbrochen \u2014 neue Nachricht wird gesendet',
     settings_label_busy_input_mode: 'Eingabemodus bei Besch\u00e4ftigung',
     settings_desc_busy_input_mode: 'Steuert, was passiert, wenn Sie w\u00e4hrend der Agentenaktivit\u00e4t eine Nachricht senden. Warteschlange wartet; Unterbrechen bricht ab und startet neu; Steer f\u00fcgt eine Korrektur ein ohne zu unterbrechen.',
@@ -9582,6 +9642,16 @@ const LOCALES = {
     cmd_steer_delivered: 'Steer 已交付 — 代理将在下一个工具结果中看到',
     steer_leftover_queued: 'Steer 已加入下轮队列',
     busy_steer_fallback: 'Steer 不可用 — 草稿已恢复',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: '已中断 — 正在发送新消息',
     settings_label_busy_input_mode: '忙碌输入模式',
     settings_desc_busy_input_mode: '控制当代理正在运行时你发送消息会发生什么。队列会等待；中断会取消并重新开始；引导会在不中断的情况下注入中间修正（当流不可用时回退到队列）。',
@@ -11103,6 +11173,16 @@ const LOCALES = {
     cmd_steer_delivered: 'Steer 已送達，Agent 會在下一個工具結果中看到',
     steer_leftover_queued: 'Steer 已加入下一輪佇列',
     busy_steer_fallback: 'Steer 不可用 — 已恢復草稿',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: '已中斷，正在傳送新訊息',
     settings_label_busy_input_mode: '忙碌輸入模式',
     settings_desc_busy_input_mode: '控制 Agent 執行時送出訊息的行為。佇列會等待；中斷會取消並重新開始；Steer 會中途注入修正且不中斷（Agent 或串流無法使用時會退回佇列）。',
@@ -12608,6 +12688,16 @@ const LOCALES = {
     cmd_steer_delivered: 'Steer entregue — agente verá no próximo resultado',
     steer_leftover_queued: 'Steer enfileirado para próximo turno',
     busy_steer_fallback: 'Steer indisponível — rascunho restaurado',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: 'Interrompido — enviando nova mensagem',
     settings_label_busy_input_mode: 'Modo de input ocupado',
     settings_desc_busy_input_mode: 'Controla o que acontece ao enviar mensagem com agente rodando. Fila espera; Interromper cancela; Steer injeta correção.',
@@ -14071,6 +14161,16 @@ const LOCALES = {
     cmd_steer_delivered: 'Steer delivered — agent will see it on its next tool result',
     steer_leftover_queued: 'Steer queued for next turn',
     busy_steer_fallback: 'Steer unavailable — draft restored',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: 'Interrupted — sending new message',
     settings_label_busy_input_mode: '작업 중 입력 방식',
     settings_desc_busy_input_mode: '에이전트가 실행 중일 때 메시지를 보내면 어떻게 처리할지 제어합니다. 대기는 다음 차례까지 기다리고, 중단은 현재 작업을 취소하고 새로 시작하며, 조정은 현재 작업을 중단하지 않고 중간 수정 사항을 전달합니다(에이전트 또는 스트림을 사용할 수 없으면 대기로 전환).',
@@ -15632,6 +15732,16 @@ const LOCALES = {
     cmd_steer_delivered: 'Steer livré - l\'agent le verra sur son prochain résultat d\'outil',
     steer_leftover_queued: 'Bœuf en attente pour le prochain tour',
     busy_steer_fallback: 'Steer indisponible – brouillon restauré',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: 'Interrompu — envoi d\'un nouveau message',
     settings_label_busy_input_mode: 'Mode de saisie occupé',
     settings_desc_busy_input_mode: 'Contrôle ce qui se passe lorsque vous envoyez un message pendant l\'exécution de l\'agent. La file d\'attente attend ; L\'interruption s\'annule et recommence ; Steer injecte une correction à mi-tour sans interrompre (revient en file d\'attente lorsque l\'agent ou le flux est indisponible).',
@@ -17169,6 +17279,16 @@ const LOCALES = {
     cmd_steer_delivered: 'Yönlendirme teslim edildi — temsilci bunu bir sonraki takım sonucunda görecek',
     steer_leftover_queued: 'Direksiyon bir sonraki dönüş için kuyruğa alındı',
     busy_steer_fallback: 'Yönlendirme kullanılamıyor — taslak geri yüklendi',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: 'Kesintiye uğradı — yeni mesaj gönderilir',
     settings_label_busy_input_mode: 'Meşgul giriş modu',
     settings_desc_busy_input_mode: 'Aracı çalışırken bir mesaj gönderdiğinizde ne olacağını kontrol eder. Sıra bekler; Interrupt iptal eder ve yeniden başlar; Steer, dönüşün ortasında kesintiye uğramadan bir düzeltme enjekte eder (aracı veya akış mevcut olmadığında kuyruğa geri döner).',
@@ -18732,6 +18852,16 @@ const LOCALES = {
     cmd_steer_delivered: 'Korekta dostarczona — agent zobaczy ją przy następnym wyniku narzędzia',
     steer_leftover_queued: 'Korekta dodana do kolejki na następną turę',
     busy_steer_fallback: 'Korekta niedostępna — przywrócono szkic',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: 'Przerwano — wysyłanie nowej wiadomości',
     settings_label_busy_input_mode: 'Tryb wprowadzania przy zajętości',
     settings_desc_busy_input_mode: 'Kontroluje, co dzieje się, gdy wysyłasz wiadomość, podczas gdy agent pracuje. Kolejkowanie czeka; Przerwanie anuluje i zaczyna od nowa; Kierowanie (Steer) wprowadza korektę w środku tury bez przerywania (cofa się do kolejkowania, gdy agent lub strumień jest niedostępny).',
@@ -20281,6 +20411,16 @@ const LOCALES = {
     cmd_steer_delivered: 'Steer đã được gửi — agent sẽ thấy ở kết quả tool tiếp theo',
     steer_leftover_queued: 'Steer đã được đưa vào hàng chờ lượt tiếp theo',
     busy_steer_fallback: 'Steer không khả dụng — đã đưa vào hàng chờ lượt tiếp theo',
+    steer_fail_no_cached_agent: 'No agent cached for this session — try refreshing',
+    steer_fail_agent_lacks_steer: 'This agent version does not support steer',
+    steer_fail_session_not_found: 'Session not found — it may have expired',
+    steer_fail_not_running: 'Agent is not currently running',
+    steer_fail_stream_dead: 'The agent stream has ended',
+    steer_fail_steer_error: 'Steer delivery failed — the agent may have finished',
+    steer_fail_network_error: 'Network error — check your connection',
+    steer_fail_unknown: 'Steer unavailable',
+    steer_recovery_retry: 'Retry',
+    steer_recovery_dismiss: 'Dismiss',
     busy_interrupt_confirm: 'Đã ngắt — đang gửi tin nhắn mới',
     settings_label_busy_input_mode: 'Chế độ nhập khi bận',
     settings_desc_busy_input_mode: 'Điều khiển hành vi khi bạn gửi tin nhắn trong lúc agent đang chạy. Queue sẽ chờ; Interrupt sẽ hủy và bắt đầu mới; Steer sẽ chèn điều chỉnh giữa lượt mà không ngắt (sẽ fallback sang queue nếu agent hoặc stream không khả dụng).',
diff --git a/static/style.css b/static/style.css
index dbd6e194..764d8048 100644
--- a/static/style.css
+++ b/static/style.css
@@ -1735,6 +1735,13 @@
   .steer-indicator{display:flex;align-items:baseline;gap:8px;padding:10px 0;opacity:.65;font-style:italic;color:var(--accent-text);}
   .steer-indicator .steer-body{white-space:pre-wrap;word-break:break-word;}
   .steer-badge{display:inline-block;font-size:10px;font-weight:600;letter-spacing:.04em;text-transform:uppercase;color:var(--accent-text);background:var(--accent-bg);border:1px solid var(--accent-bg-strong);border-radius:4px;padding:1px 6px;vertical-align:middle;line-height:1.6;font-style:normal;flex-shrink:0;}
+  /* Steer recovery bar: dismissible after failure, same lifecycle as steer-indicator */
+  .steer-recovery{display:flex;align-items:center;gap:0.5rem;padding:0.5rem 0.75rem;margin:0.25rem 0;border-radius:var(--radius-md);background:var(--surface-subtle);font-size:0.85rem}
+  .steer-recovery-label{flex:1;min-width:0;color:var(--text)}
+  .steer-recovery button{padding:0.25rem 0.75rem;border-radius:var(--radius-md);border:1px solid var(--border);background:var(--surface);color:var(--text);cursor:pointer;font-size:0.8rem;line-height:1.4;white-space:nowrap}
+  .steer-recovery button:hover{background:var(--hover-bg);color:var(--text)}
+  .steer-recovery-retry{border-color:var(--accent);color:var(--accent);font-weight:600}
+  .steer-recovery-retry:hover{color:var(--accent)}
   .msg-role{font-size:12px;font-weight:500;letter-spacing:.01em;margin-bottom:8px;display:flex;align-items:center;gap:8px;}
   .msg-role.user{color:var(--accent);}
   .msg-role.assistant{color:var(--accent-text);opacity:.6;}
diff --git a/tests/test_1062_busy_input_modes.py b/tests/test_1062_busy_input_modes.py
index 5d8724f9..b7eb9ce5 100644
--- a/tests/test_1062_busy_input_modes.py
+++ b/tests/test_1062_busy_input_modes.py
@@ -110,7 +110,7 @@ class TestSlashCommandHandlers:
         assert "cancelStream" not in helper_body
         assert "inp.value" in helper_body
         # Toast should differ from interrupt to signal it's the steer path
-        assert "cmd_steer_fallback" in helper_body or "steer_fallback" in helper_body
+        assert "_steerFailureMessageKey" in helper_body or "steer_fail_" in helper_body
 
 
 # ── send() busy branch ───────────────────────────────────────────────────
diff --git a/tests/test_issue4749_steer_reason_and_recovery.py b/tests/test_issue4749_steer_reason_and_recovery.py
new file mode 100644
index 00000000..7a946b58
--- /dev/null
+++ b/tests/test_issue4749_steer_reason_and_recovery.py
@@ -0,0 +1,275 @@
+"""Tests for issue #4749: steer failure reason display and recovery bar.
+
+Covers:
+  1. i18n contract — all expected keys exist in the en locale block
+  2. Reason map contract — _steerFailureMessageKey returns correct keys
+  3. Backend parity — frontend reason map covers all backend fallback codes
+  4. Recovery DOM — _showSteerRecovery creates correct structure; dismiss removes it
+"""
+import re
+import subprocess
+import sys
+import textwrap
+from pathlib import Path
+
+REPO = Path(__file__).parent.parent
+I18N_JS = REPO / "static" / "i18n.js"
+COMMANDS_JS = REPO / "static" / "commands.js"
+STREAMING_PY = REPO / "api" / "streaming.py"
+
+EXPECTED_I18N_KEYS = [
+    "steer_fail_no_cached_agent",
+    "steer_fail_agent_lacks_steer",
+    "steer_fail_session_not_found",
+    "steer_fail_not_running",
+    "steer_fail_stream_dead",
+    "steer_fail_steer_error",
+    "steer_fail_network_error",
+    "steer_fail_unknown",
+    "steer_recovery_retry",
+    "steer_recovery_dismiss",
+]
+
+BACKEND_CODES = {
+    "no_cached_agent",
+    "agent_lacks_steer",
+    "session_not_found",
+    "not_running",
+    "stream_dead",
+    "steer_error",
+}
+
+FRONTEND_NETWORK_CODE = "network_error"
+
+
+def test_i18n_steer_failure_keys_exist():
+    """All 10 expected i18n keys are present in the en locale block."""
+    text = I18N_JS.read_text(encoding="utf-8")
+    # Find the en locale block: from 'en:' or 'en =' up to the next top-level locale key
+    en_match = re.search(r"\ben\s*:\s*\{", text)
+    assert en_match, "Could not locate 'en:' locale block in i18n.js"
+    # Grab a large slice starting at the en block; the block is thousands of lines
+    en_block = text[en_match.start():]
+    for key in EXPECTED_I18N_KEYS:
+        pattern = rf"^\s+{re.escape(key)}\s*:"
+        assert re.search(pattern, en_block, re.MULTILINE), (
+            f"Expected i18n key '{key}' not found in the en locale block"
+        )
+
+
+def test_reason_map_contract():
+    """_steerFailureMessageKey maps each known code to the correct key."""
+    node = _find_node()
+    script = textwrap.dedent("""
+        const LOCALES = { en: {
+            steer_fail_no_cached_agent: 'x',
+            steer_fail_agent_lacks_steer: 'x',
+            steer_fail_session_not_found: 'x',
+            steer_fail_not_running: 'x',
+            steer_fail_stream_dead: 'x',
+            steer_fail_steer_error: 'x',
+            steer_fail_network_error: 'x',
+            steer_fail_unknown: 'x',
+        }};
+
+        function _steerFailureMessageKey(fallback) {
+            const key = 'steer_fail_' + (fallback || 'unknown');
+            return (typeof LOCALES !== 'undefined' && LOCALES.en && LOCALES.en[key])
+                ? key : 'steer_fail_unknown';
+        }
+
+        const codes = [
+            'no_cached_agent', 'agent_lacks_steer', 'session_not_found',
+            'not_running', 'stream_dead', 'steer_error', 'network_error',
+        ];
+        let ok = true;
+        for (const c of codes) {
+            const got = _steerFailureMessageKey(c);
+            const want = 'steer_fail_' + c;
+            if (got !== want) {
+                console.error('FAIL code=' + c + ' got=' + got + ' want=' + want);
+                ok = false;
+            }
+        }
+        // unknown code
+        const unk = _steerFailureMessageKey('something_unknown_xyz');
+        if (unk !== 'steer_fail_unknown') {
+            console.error('FAIL unknown: got=' + unk);
+            ok = false;
+        }
+        // null / undefined
+        const n = _steerFailureMessageKey(null);
+        if (n !== 'steer_fail_unknown') {
+            console.error('FAIL null: got=' + n);
+            ok = false;
+        }
+        const u = _steerFailureMessageKey(undefined);
+        if (u !== 'steer_fail_unknown') {
+            console.error('FAIL undefined: got=' + u);
+            ok = false;
+        }
+        process.exit(ok ? 0 : 1);
+    """)
+    result = subprocess.run([node, "-e", script], capture_output=True, text=True)
+    assert result.returncode == 0, (
+        f"_steerFailureMessageKey contract failed:\n{result.stdout}\n{result.stderr}"
+    )
+
+
+def test_backend_parity():
+    """Frontend reason map covers all backend fallback codes from _handle_chat_steer."""
+    streaming_text = STREAMING_PY.read_text(encoding="utf-8")
+    # Extract fallback codes from _handle_chat_steer function only
+    fn_match = re.search(r"def _handle_chat_steer\b.*?(?=\ndef |\Z)", streaming_text, re.DOTALL)
+    assert fn_match, "Could not find _handle_chat_steer in streaming.py"
+    fn_body = fn_match.group(0)
+    # Exclude placeholder strings like "<reason>" that appear in docstrings
+    found_codes = set(
+        c for c in re.findall(r'"fallback":\s*"([^"<>]+)"', fn_body)
+        if c  # non-empty after filtering
+    )
+    assert found_codes, "No fallback codes found in _handle_chat_steer"
+    assert found_codes == BACKEND_CODES, (
+        f"Backend fallback codes mismatch.\n"
+        f"  Found:    {sorted(found_codes)}\n"
+        f"  Expected: {sorted(BACKEND_CODES)}"
+    )
+    # Also confirm frontend adds network_error
+    commands_text = COMMANDS_JS.read_text(encoding="utf-8")
+    assert FRONTEND_NETWORK_CODE in commands_text, (
+        "network_error not found in commands.js"
+    )
+    # Confirm the dynamic key builder and recovery bar are present in commands.js
+    assert "_steerFailureMessageKey" in commands_text, (
+        "_steerFailureMessageKey not found in commands.js"
+    )
+    assert "_showSteerRecovery" in commands_text, (
+        "_showSteerRecovery not found in commands.js"
+    )
+    # The builder uses the 'steer_fail_' prefix pattern
+    assert "steer_fail_" in commands_text, (
+        "'steer_fail_' prefix not found in commands.js"
+    )
+
+
+def test_recovery_dom_structure():
+    """_showSteerRecovery creates a div with label, retry, dismiss; dismiss removes it."""
+    node = _find_node()
+    script = textwrap.dedent("""
+        // Minimal DOM stubs
+        const elements = {};
+        function createElement(tag) {
+            const el = {
+                tag, className: '', textContent: '', children: [],
+                listeners: {},
+                appendChild(c) { this.children.push(c); },
+                addEventListener(ev, fn) { this.listeners[ev] = fn; },
+                remove() { el._removed = true; },
+                querySelector(sel) {
+                    // only handle .steer-recovery for old-removal check
+                    return null;
+                },
+            };
+            elements[tag + '_' + Math.random()] = el;
+            return el;
+        }
+        const inner = createElement('div');
+        inner.querySelector = (sel) => null; // no existing recovery bar
+        const document = {
+            getElementById(id) { return id === 'msgInner' ? inner : null; },
+            createElement,
+        };
+        function t(key) { return key; }
+        function _steerFailureMessageKey(fallback) {
+            const key = 'steer_fail_' + (fallback || 'unknown');
+            const LOCALES = { en: {
+                steer_fail_not_running: 'Agent is not currently running',
+                steer_fail_unknown: 'Steer unavailable',
+                steer_recovery_retry: 'Retry',
+                steer_recovery_dismiss: 'Dismiss',
+            }};
+            return (LOCALES.en && LOCALES.en[key]) ? key : 'steer_fail_unknown';
+        }
+        function _trySteer() {}  // stub for retry handler
+
+        function _showSteerRecovery(msg, explicitSteer, fallback) {
+            const inner = document.getElementById('msgInner');
+            if (!inner) return;
+            const old = inner.querySelector('.steer-recovery');
+            if (old) old.remove();
+            const el = document.createElement('div');
+            el.className = 'steer-recovery';
+            const label = document.createElement('span');
+            label.className = 'steer-recovery-label';
+            label.textContent = t(_steerFailureMessageKey(fallback));
+            el.appendChild(label);
+            const retryBtn = document.createElement('button');
+            retryBtn.className = 'steer-recovery-retry';
+            retryBtn.textContent = t('steer_recovery_retry');
+            retryBtn.addEventListener('click', () => {
+                el.remove();
+                _trySteer(msg, explicitSteer);
+            });
+            el.appendChild(retryBtn);
+            const dismissBtn = document.createElement('button');
+            dismissBtn.className = 'steer-recovery-dismiss';
+            dismissBtn.textContent = t('steer_recovery_dismiss');
+            dismissBtn.addEventListener('click', () => el.remove());
+            el.appendChild(dismissBtn);
+            inner.appendChild(el);
+        }
+
+        _showSteerRecovery('hello', false, 'not_running');
+
+        const bar = inner.children[inner.children.length - 1];
+        let ok = true;
+
+        if (bar.className !== 'steer-recovery') {
+            console.error('FAIL: bar className=' + bar.className);
+            ok = false;
+        }
+        const [lbl, retry, dismiss] = bar.children;
+        if (!lbl || lbl.className !== 'steer-recovery-label') {
+            console.error('FAIL: label missing or wrong class');
+            ok = false;
+        }
+        if (!retry || retry.className !== 'steer-recovery-retry') {
+            console.error('FAIL: retry btn missing or wrong class');
+            ok = false;
+        }
+        if (!dismiss || dismiss.className !== 'steer-recovery-dismiss') {
+            console.error('FAIL: dismiss btn missing or wrong class');
+            ok = false;
+        }
+        // Simulate dismiss click
+        dismiss.listeners['click']();
+        if (!bar._removed) {
+            console.error('FAIL: bar not removed after dismiss');
+            ok = false;
+        }
+        process.exit(ok ? 0 : 1);
+    """)
+    result = subprocess.run([node, "-e", script], capture_output=True, text=True)
+    assert result.returncode == 0, (
+        f"Recovery DOM structure test failed:\n{result.stdout}\n{result.stderr}"
+    )
+
+
+def _find_node():
+    """Return path to node.exe, skipping wrapper scripts."""
+    import shutil
+    candidates = ["node", "node.exe"]
+    for c in candidates:
+        path = shutil.which(c)
+        if path:
+            # Verify it's actually node, not a wrapper
+            try:
+                r = subprocess.run([path, "--version"], capture_output=True, text=True, timeout=5)
+                if r.returncode == 0 and r.stdout.strip().startswith("v"):
+                    return path
+            except Exception:
+                continue
+    pytest_skip = getattr(sys.modules.get("pytest"), "skip", None)
+    if pytest_skip:
+        pytest_skip("node.js not found — skipping node-executed tests")
+    raise RuntimeError("node.js not found")