diff --git a/gui/src/components/subagents-workspace/SubagentDelegationSection.tsx b/gui/src/components/subagents-workspace/SubagentDelegationSection.tsx
index e631570734..7924c9fedf 100644
--- a/gui/src/components/subagents-workspace/SubagentDelegationSection.tsx
+++ b/gui/src/components/subagents-workspace/SubagentDelegationSection.tsx
@@ -27,6 +27,13 @@ export interface SubagentDelegationSectionProps {
   onUltraModeSave: (patch: UltraModePatch) => void;
   ultraLoadFailed: boolean;
   onUltraModeRetry: () => void;
+  fallback: string[];
+  fallbackPollMs: number;
+  fallbackBusy: boolean;
+  availableModels: string[];
+  onFallbackChange: (models: string[]) => void;
+  onFallbackPollMsChange: (pollMs: number) => void;
+  onFallbackSave: () => void;
 }
 
 export default function SubagentDelegationSection({
@@ -43,6 +50,7 @@ export default function SubagentDelegationSection({
   onUltraModeSave,
   ultraLoadFailed,
   onUltraModeRetry,
+  fallback, fallbackPollMs, fallbackBusy, availableModels, onFallbackChange, onFallbackPollMsChange, onFallbackSave,
 }: SubagentDelegationSectionProps) {
   const t = useT();
   // A present empty/whitespace hint is an upstream override that suppresses the
@@ -96,6 +104,31 @@ export default function SubagentDelegationSection({
         </div>
       </div>
 
+      <div className="swi-delegation-row swi-fallback-editor">
+        <div className="setting-copy">
+          <div className="font-semibold">{t("sub.fallbackLabel")}</div>
+          <div className="muted setting-hint">{t("sub.fallbackHint")}</div>
+        </div>
+        <div className="swi-fallback-controls">
+          {fallback.map((modelName, index) => (
+            <div key={modelName} className="swi-fallback-row">
+              <span>{index + 1}. {modelName}</span>
+              <button type="button" className="btn btn-ghost btn-sm" onClick={() => { const next = [...fallback]; if (index > 0) [next[index - 1], next[index]] = [next[index], next[index - 1]]; onFallbackChange(next); }} disabled={fallbackBusy || index === 0} aria-label={t("sub.moveUp", { m: modelName })}>↑</button>
+              <button type="button" className="btn btn-ghost btn-sm" onClick={() => { const next = [...fallback]; if (index < next.length - 1) [next[index], next[index + 1]] = [next[index + 1], next[index]]; onFallbackChange(next); }} disabled={fallbackBusy || index === fallback.length - 1} aria-label={t("sub.moveDown", { m: modelName })}>↓</button>
+              <button type="button" className="btn btn-ghost btn-sm" onClick={() => onFallbackChange(fallback.filter(item => item !== modelName))} disabled={fallbackBusy}>×</button>
+            </div>
+          ))}
+          <select className="input" value="" onChange={e => { if (e.target.value && !fallback.includes(e.target.value)) onFallbackChange([...fallback, e.target.value]); }} disabled={fallbackBusy}>
+            <option value="">{t("sub.fallbackAdd")}</option>
+            {availableModels.filter(modelName => !fallback.includes(modelName)).map(modelName => <option key={modelName} value={modelName}>{modelName}</option>)}
+          </select>
+          <label className="setting-hint">{t("sub.fallbackPoll")}
+            <input className="input" type="number" min={5000} max={600000} step={1000} value={fallbackPollMs} onChange={e => onFallbackPollMsChange(Number(e.target.value) || 60000)} disabled={fallbackBusy} /> ms
+          </label>
+          <button type="button" className="btn btn-primary btn-sm" onClick={onFallbackSave} disabled={fallbackBusy}>{t("common.save")}</button>
+        </div>
+      </div>
+
       <div className="swi-delegation-row">
         <div className="setting-copy">
           <div className="font-semibold">{t("dash.syncCodexSubagentDefaults")}</div>
diff --git a/gui/src/components/subagents-workspace/SubagentsWorkspace.tsx b/gui/src/components/subagents-workspace/SubagentsWorkspace.tsx
index 862467da09..230421b6cb 100644
--- a/gui/src/components/subagents-workspace/SubagentsWorkspace.tsx
+++ b/gui/src/components/subagents-workspace/SubagentsWorkspace.tsx
@@ -36,6 +36,12 @@ export interface SubagentsWorkspaceProps {
   onToggle: (m: string) => void;
   onMove: (i: number, dir: -1 | 1) => void;
   onSave: () => void;
+  fallback: string[];
+  fallbackPollMs: number;
+  fallbackBusy: boolean;
+  onFallbackChange: (models: string[]) => void;
+  onFallbackPollMsChange: (pollMs: number) => void;
+  onFallbackSave: () => void;
   delegation: {
     model: string;
     effort: string;
@@ -62,6 +68,7 @@ export default function SubagentsWorkspace({
   onToggle,
   onMove,
   onSave,
+  fallback, fallbackPollMs, fallbackBusy, onFallbackChange, onFallbackPollMsChange, onFallbackSave,
   delegation,
 }: SubagentsWorkspaceProps) {
   const t = useT();
@@ -234,6 +241,13 @@ export default function SubagentsWorkspace({
             onUltraModeSave={delegation.onUltraModeSave}
             ultraLoadFailed={delegation.ultraLoadFailed}
             onUltraModeRetry={delegation.onUltraModeRetry}
+            fallback={fallback}
+            fallbackPollMs={fallbackPollMs}
+            fallbackBusy={fallbackBusy}
+            availableModels={available}
+            onFallbackChange={onFallbackChange}
+            onFallbackPollMsChange={onFallbackPollMsChange}
+            onFallbackSave={onFallbackSave}
           />
         </section>
       </div>
diff --git a/gui/src/i18n/de.ts b/gui/src/i18n/de.ts
index eff4574b7a..c627b1e9cf 100644
--- a/gui/src/i18n/de.ts
+++ b/gui/src/i18n/de.ts
@@ -2361,4 +2361,10 @@ export const de: Record<TKey, string> = {
   "usage.scope.machine": "This machine",
   "usage.scope.hub": "Hub-wide",
   "usage.hubOffline": "Hub usage is unavailable. Local usage was not substituted.",
+  "sub.fallbackLabel": "Fallback-Kette für Sub-Agenten",
+  "sub.fallbackHint": "Modelle in dieser Reihenfolge versuchen, wenn ein Sub-Agent-Modell nicht verfügbar ist oder fehlschlägt.",
+  "sub.fallbackAdd": "Fallback-Modell hinzufügen…",
+  "sub.fallbackPoll": "Intervall der Verfügbarkeitsprüfung",
+  "sub.fallbackSaved": "Fallback-Einstellungen für Sub-Agenten gespeichert.",
+  "sub.fallbackSaveFailed": "Fallback-Einstellungen konnten nicht gespeichert werden",
 };
diff --git a/gui/src/i18n/en.ts b/gui/src/i18n/en.ts
index 8abb9816fa..44f3094ea9 100644
--- a/gui/src/i18n/en.ts
+++ b/gui/src/i18n/en.ts
@@ -2395,6 +2395,12 @@ export const en = {
   "usage.scope.machine": "This machine",
   "usage.scope.hub": "Hub-wide",
   "usage.hubOffline": "Hub usage is unavailable. Local usage was not substituted.",
+  "sub.fallbackLabel": "Sub-agent fallback chain",
+  "sub.fallbackHint": "Ordered models tried when a sub-agent model is unavailable or fails.",
+  "sub.fallbackAdd": "Add fallback model…",
+  "sub.fallbackPoll": "Availability check interval",
+  "sub.fallbackSaved": "Sub-agent fallback settings saved.",
+  "sub.fallbackSaveFailed": "Failed to save fallback settings",
 } as const;
 
 export type TKey = keyof typeof en;
diff --git a/gui/src/i18n/fr.ts b/gui/src/i18n/fr.ts
index 4797b8719b..8e0cf44380 100644
--- a/gui/src/i18n/fr.ts
+++ b/gui/src/i18n/fr.ts
@@ -2348,4 +2348,10 @@ export const fr: Record<TKey, string> = {
   "usage.scope.machine": "Cette machine",
   "usage.scope.hub": "Tout le hub",
   "usage.hubOffline": "L'utilisation du hub est indisponible. Les données locales n'ont pas été substituées.",
+  "sub.fallbackLabel": "Chaîne de secours des sous-agents",
+  "sub.fallbackHint": "Modèles essayés dans cet ordre lorsqu’un modèle de sous-agent est indisponible ou échoue.",
+  "sub.fallbackAdd": "Ajouter un modèle de secours…",
+  "sub.fallbackPoll": "Intervalle de vérification de disponibilité",
+  "sub.fallbackSaved": "Paramètres de secours des sous-agents enregistrés.",
+  "sub.fallbackSaveFailed": "Échec de l’enregistrement des paramètres de secours",
 };
diff --git a/gui/src/i18n/ja.ts b/gui/src/i18n/ja.ts
index 0c2a1b69d8..fadd61cea8 100644
--- a/gui/src/i18n/ja.ts
+++ b/gui/src/i18n/ja.ts
@@ -2382,4 +2382,10 @@ export const ja: Record<TKey, string> = {
   "usage.scope.machine": "This machine",
   "usage.scope.hub": "Hub-wide",
   "usage.hubOffline": "Hub usage is unavailable. Local usage was not substituted.",
+  "sub.fallbackLabel": "サブエージェントのフォールバックチェーン",
+  "sub.fallbackHint": "サブエージェントモデルが利用できない、または失敗した場合に試すモデルの順序です。",
+  "sub.fallbackAdd": "フォールバックモデルを追加…",
+  "sub.fallbackPoll": "可用性確認間隔",
+  "sub.fallbackSaved": "サブエージェントのフォールバック設定を保存しました。",
+  "sub.fallbackSaveFailed": "フォールバック設定を保存できませんでした",
 };
diff --git a/gui/src/i18n/ko.ts b/gui/src/i18n/ko.ts
index 898cd67d3e..8dc035ec36 100644
--- a/gui/src/i18n/ko.ts
+++ b/gui/src/i18n/ko.ts
@@ -2383,4 +2383,10 @@ export const ko: Record<TKey, string> = {
   "usage.scope.machine": "이 머신",
   "usage.scope.hub": "허브 전체",
   "usage.hubOffline": "허브 사용량을 불러올 수 없습니다. 로컬 사용량으로 대체하지 않았습니다.",
+  "sub.fallbackLabel": "하위 에이전트 폴백 체인",
+  "sub.fallbackHint": "하위 에이전트 모델을 사용할 수 없거나 실패할 때 이 순서로 시도합니다.",
+  "sub.fallbackAdd": "폴백 모델 추가…",
+  "sub.fallbackPoll": "가용성 확인 간격",
+  "sub.fallbackSaved": "하위 에이전트 폴백 설정을 저장했습니다.",
+  "sub.fallbackSaveFailed": "폴백 설정을 저장하지 못했습니다",
 };
diff --git a/gui/src/i18n/ru.ts b/gui/src/i18n/ru.ts
index 12c47f477c..c3396570eb 100644
--- a/gui/src/i18n/ru.ts
+++ b/gui/src/i18n/ru.ts
@@ -2384,4 +2384,10 @@ export const ru: Record<TKey, string> = {
   "usage.scope.machine": "This machine",
   "usage.scope.hub": "Hub-wide",
   "usage.hubOffline": "Hub usage is unavailable. Local usage was not substituted.",
+  "sub.fallbackLabel": "Цепочка резервных моделей подагентов",
+  "sub.fallbackHint": "Модели, которые пробуются по порядку, если модель подагента недоступна или завершилась ошибкой.",
+  "sub.fallbackAdd": "Добавить резервную модель…",
+  "sub.fallbackPoll": "Интервал проверки доступности",
+  "sub.fallbackSaved": "Настройки резервных моделей подагентов сохранены.",
+  "sub.fallbackSaveFailed": "Не удалось сохранить настройки резервных моделей",
 };
diff --git a/gui/src/i18n/tr.ts b/gui/src/i18n/tr.ts
index 4aaeffec66..fbb65f2b47 100644
--- a/gui/src/i18n/tr.ts
+++ b/gui/src/i18n/tr.ts
@@ -2384,4 +2384,10 @@ export const tr: Record<TKey, string> = {
   "usage.scope.machine": "This machine",
   "usage.scope.hub": "Hub-wide",
   "usage.hubOffline": "Hub usage is unavailable. Local usage was not substituted.",
+  "sub.fallbackLabel": "Alt ajan geri dönüş zinciri",
+  "sub.fallbackHint": "Alt ajan modeli kullanılamadığında veya başarısız olduğunda sırayla denenecek modeller.",
+  "sub.fallbackAdd": "Geri dönüş modeli ekle…",
+  "sub.fallbackPoll": "Kullanılabilirlik denetimi aralığı",
+  "sub.fallbackSaved": "Alt ajan geri dönüş ayarları kaydedildi.",
+  "sub.fallbackSaveFailed": "Geri dönüş ayarları kaydedilemedi",
 };
diff --git a/gui/src/i18n/zh-TW.ts b/gui/src/i18n/zh-TW.ts
index 182fa48751..293605863d 100644
--- a/gui/src/i18n/zh-TW.ts
+++ b/gui/src/i18n/zh-TW.ts
@@ -2346,4 +2346,10 @@ export const zhTW: Record<TKey, string> = {
   "usage.scope.machine": "此機器",
   "usage.scope.hub": "整個 Hub",
   "usage.hubOffline": "Hub 使用量無法使用，未以本機使用量替代。",
+  "sub.fallbackLabel": "子代理備援鏈",
+  "sub.fallbackHint": "子代理模型無法使用或失敗時，會依此順序嘗試模型。",
+  "sub.fallbackAdd": "新增備援模型…",
+  "sub.fallbackPoll": "可用性檢查間隔",
+  "sub.fallbackSaved": "子代理備援設定已儲存。",
+  "sub.fallbackSaveFailed": "無法儲存備援設定",
 };
diff --git a/gui/src/i18n/zh.ts b/gui/src/i18n/zh.ts
index 96f3d939c2..738d389bc9 100644
--- a/gui/src/i18n/zh.ts
+++ b/gui/src/i18n/zh.ts
@@ -2382,4 +2382,10 @@ export const zh: Record<TKey, string> = {
   "usage.scope.machine": "This machine",
   "usage.scope.hub": "Hub-wide",
   "usage.hubOffline": "Hub usage is unavailable. Local usage was not substituted.",
+  "sub.fallbackLabel": "子代理回退链",
+  "sub.fallbackHint": "子代理模型不可用或失败时按此顺序尝试的模型。",
+  "sub.fallbackAdd": "添加回退模型…",
+  "sub.fallbackPoll": "可用性检查间隔",
+  "sub.fallbackSaved": "子代理回退设置已保存。",
+  "sub.fallbackSaveFailed": "保存回退设置失败",
 };
diff --git a/gui/src/pages/Subagents.tsx b/gui/src/pages/Subagents.tsx
index ea36769466..ab1bc11bf2 100644
--- a/gui/src/pages/Subagents.tsx
+++ b/gui/src/pages/Subagents.tsx
@@ -8,7 +8,7 @@ import { useDataSurface } from "../data-surface";
 import { DataSurfaceSkeleton } from "../components/data-surface";
 import { useSubagentDelegation, type UltraModePatch, type UltraModeState } from "./use-subagent-delegation";
 
-type CachedSubagents = { available: string[]; chosen: string[] };
+type CachedSubagents = { available: string[]; chosen: string[]; fallback: string[]; pollMs: number };
 
 function seedSubagents(cacheKey: string): CachedSubagents | null {
   return readSessionListCache<CachedSubagents>(cacheKey);
@@ -19,6 +19,9 @@ export default function Subagents({ apiBase }: { apiBase: string }) {
   const cacheKey = `ocx.subagents.v1:${apiBase}`;
   const cached = seedSubagents(cacheKey);
   const [chosen, setChosen] = useState<string[]>(() => cached?.chosen ?? []);
+  const [fallback, setFallback] = useState<string[]>(() => cached?.fallback ?? []);
+  const [fallbackPollMs, setFallbackPollMs] = useState(() => cached?.pollMs ?? 60000);
+  const [fallbackBusy, setFallbackBusy] = useState(false);
   const [status, setStatus] = useState("");
   const [ok, setOk] = useState(false);
   const [busy, setBusy] = useState(false);
@@ -116,16 +119,24 @@ export default function Subagents({ apiBase }: { apiBase: string }) {
   const loadSubagents = useCallback(async (signal?: AbortSignal): Promise<CachedSubagents> => {
     // The resource layer's deadline abort must reach the wire — a signal dropped
     // here is a store that can only settle by race timeout.
-    const res = await fetch(`${apiBase}/api/subagent-models`, { signal });
-    const response = await readJsonOrThrow<{ available?: string[]; chosen?: string[] }>(res, t("sub.loadFail"));
-    if (!response) throw new Error(t("sub.loadFail"));
-    const available = response.available ?? [];
+    const [rosterRes, fallbackRes] = await Promise.all([
+      fetch(`${apiBase}/api/subagent-models`, { signal }),
+      fetch(`${apiBase}/api/subagent-model-fallback`, { signal }),
+    ]);
+    const response = await readJsonOrThrow<{ available?: string[]; chosen?: string[] }>(rosterRes, t("sub.loadFail"));
+    const fallbackResponse = await readJsonOrThrow<{ available?: string[]; models?: string[]; pollMs?: number }>(fallbackRes, t("sub.loadFail"));
+    if (!response || !fallbackResponse) throw new Error(t("sub.loadFail"));
+    const available = response.available ?? fallbackResponse.available ?? [];
     const availableSet = new Set(available);
     const next = {
       available,
       chosen: (response.chosen ?? []).filter(model => availableSet.has(model)),
+      fallback: (fallbackResponse.models ?? []).filter(model => availableSet.has(model)),
+      pollMs: fallbackResponse.pollMs ?? 60000,
     };
     setChosen(next.chosen);
+    setFallback(next.fallback);
+    setFallbackPollMs(next.pollMs);
     writeSessionListCache(cacheKey, next);
     return next;
   }, [apiBase, cacheKey, t]);
@@ -173,7 +184,7 @@ export default function Subagents({ apiBase }: { apiBase: string }) {
       const d = await readJsonOrThrow<{ applied?: string[] }>(r, t("sub.saveFailed"));
       const applied = d?.applied ?? chosen;
       if (d?.applied) setChosen(d.applied);
-      writeSessionListCache(cacheKey, { available, chosen: applied });
+      writeSessionListCache(cacheKey, { available, chosen: applied, fallback, pollMs: fallbackPollMs });
       setOk(true);
       setStatus(t("sub.saved", { n: applied.length, cmd: "ocx sync" }));
     } catch (error) {
@@ -185,6 +196,28 @@ export default function Subagents({ apiBase }: { apiBase: string }) {
     }
   };
 
+  const saveFallback = async () => {
+    if (fallbackBusy) return;
+    setFallbackBusy(true);
+    try {
+      const r = await fetch(`${apiBase}/api/subagent-model-fallback`, {
+        method: "PUT",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ models: fallback, pollMs: fallbackPollMs }),
+      });
+      const d = await readJsonOrThrow<{ models?: string[]; pollMs?: number }>(r, t("sub.fallbackSaveFailed"));
+      if (d?.models) setFallback(d.models);
+      if (d?.pollMs) setFallbackPollMs(d.pollMs);
+      setOk(true);
+      setStatus(t("sub.fallbackSaved"));
+    } catch (error) {
+      setOk(false);
+      setStatus(error instanceof Error && error.message ? error.message : t("sub.networkError"));
+    } finally {
+      setFallbackBusy(false);
+    }
+  };
+
   // The skeleton owns the live region while this resource has no content yet.
   if (state.showSkeleton && !snapshot) {
     return <DataSurfaceSkeleton label={t("sub.loading")} rows={4} />;
@@ -213,7 +246,13 @@ export default function Subagents({ apiBase }: { apiBase: string }) {
         busy={busy}
         onToggle={toggle}
         onMove={move}
-        onSave={() => { void save(); }}
+          onSave={() => { void save(); }}
+          fallback={fallback}
+          fallbackPollMs={fallbackPollMs}
+          fallbackBusy={fallbackBusy}
+          onFallbackChange={setFallback}
+          onFallbackPollMsChange={setFallbackPollMs}
+          onFallbackSave={() => { void saveFallback(); }}
         delegation={{
           model: delegation.model,
           effort: delegation.effort,
diff --git a/src/codex/subagent-model-fallback.ts b/src/codex/subagent-model-fallback.ts
index 27eea1e53d..ddd5b67e60 100644
--- a/src/codex/subagent-model-fallback.ts
+++ b/src/codex/subagent-model-fallback.ts
@@ -7,7 +7,7 @@
  */
 import { existsSync, readdirSync, readFileSync } from "node:fs";
 import { join } from "node:path";
-import { hasOwnProvider } from "../config";
+import { DEFAULT_SUBAGENT_MODELS, hasOwnProvider } from "../config";
 import { isRateLimitOrQuotaFailureMessage } from "../lib/errors";
 import type { OcxParsedRequest, OcxConfig } from "../types";
 import { slugsEquivalent } from "../providers/slug-codec";
@@ -609,9 +609,14 @@ export function applySubagentModelFallback(
   resolvedFallbackChain?: readonly string[] | null,
 ): { from?: string; to?: string; skipped?: string[] } | null {
   if (!isThreadSpawnRequest(headers)) return null;
-  const fallbackChain = resolvedFallbackChain === undefined
+  const configuredFallbackChain = resolvedFallbackChain === undefined
     ? resolveSubagentFallbackChain(parsed, config)
     : resolvedFallbackChain;
+  // Native-only encrypted V2 tasks need a readable ChatGPT backend even when the
+  // operator configured no fallback chain. Keep ordinary routed spawns unchanged.
+  const fallbackChain = configuredFallbackChain === null && nativeFallbackOnly
+    ? normalizedChain(parsed.modelId, config, [], DEFAULT_SUBAGENT_MODELS)
+    : configuredFallbackChain;
   if (!fallbackChain) return null;
   const selection = selectAvailableSubagentModel(
     parsed.modelId,
diff --git a/tests/subagent-model-fallback.test.ts b/tests/subagent-model-fallback.test.ts
index 75b2359ad5..d600072798 100644
--- a/tests/subagent-model-fallback.test.ts
+++ b/tests/subagent-model-fallback.test.ts
@@ -1056,6 +1056,29 @@ describe("subagent model fallback chain", () => {
     expect((parsed._rawBody as { model?: string }).model).toBe("alibaba-token-plan/qwen3.8-max");
   });
 
+  test("encrypted routed spawn gets an automatic native fallback when none is configured", () => {
+    const config = cfg({
+      subagentModelFallback: undefined,
+      defaultProvider: "xai",
+    });
+    const parsed = {
+      modelId: "xai/grok-4.5",
+      options: {},
+      context: { messages: [] },
+      _rawBody: { model: "xai/grok-4.5" },
+    };
+    const result = applySubagentModelFallback(
+      parsed as never,
+      new Headers({ "x-openai-subagent": "collab_spawn" }),
+      config,
+      "pool-a",
+      Date.now(),
+      true,
+    );
+    expect(result?.to).toBe("gpt-5.5");
+    expect(parsed.modelId).toBe("gpt-5.5");
+  });
+
   test("applySubagentModelFallback is a no-op for main turns", () => {
     updateAccountQuota("pool-a", 95);
     const parsed = {