diff --git a/open-sse/handlers/chatCore.ts b/open-sse/handlers/chatCore.ts
index 5060b72b8c..e75e89cfc4 100644
--- a/open-sse/handlers/chatCore.ts
+++ b/open-sse/handlers/chatCore.ts
@@ -1787,7 +1787,10 @@ export async function handleChatCore({
       ? false
       : resolveStreamFlag(body?.stream, acceptHeader, sourceFormat);
   const settings = cachedSettings ?? (await getCachedSettings());
-  credentials = applyCodexGlobalFastServiceTier(provider, credentials, settings);
+  credentials = applyCodexGlobalFastServiceTier(provider, credentials, settings, {
+    model: requestedModel,
+    body: body && typeof body === "object" ? (body as Record<string, unknown>) : null,
+  });
   effectiveServiceTier = resolveEffectiveServiceTier(body);
   setGeminiThoughtSignatureMode(settings.antigravitySignatureCacheMode);
   const semanticCacheEnabled = settings.semanticCacheEnabled !== false;
diff --git a/src/app/(dashboard)/dashboard/settings/components/CodexFastTierTab.tsx b/src/app/(dashboard)/dashboard/settings/components/CodexFastTierTab.tsx
index 9df5530150..0bcef438dc 100644
--- a/src/app/(dashboard)/dashboard/settings/components/CodexFastTierTab.tsx
+++ b/src/app/(dashboard)/dashboard/settings/components/CodexFastTierTab.tsx
@@ -1,15 +1,30 @@
 "use client";
 
-import { useEffect, useState } from "react";
-import { Card, Toggle } from "@/shared/components";
+import { useEffect, useMemo, useState } from "react";
+import { Card, Toggle, Select } from "@/shared/components";
 import { useTranslations } from "next-intl";
-import { isCodexGlobalFastServiceTierEnabled } from "@/lib/providers/codexFastTier";
+import {
+  CODEX_FAST_TIER_DEFAULT_SUPPORTED_MODELS,
+  resolveCodexGlobalFastServiceTier,
+} from "@/lib/providers/codexFastTier";
+
+type TierValue = "default" | "priority" | "flex";
+
+// Fast-eligible Codex models per OpenAI ~/.codex/models_cache.json (service_tiers: priority).
+// Other future Fast-eligible slugs can be added here without code changes once the user
+// opts them in via the checkbox UI.
+const CODEX_FAST_TIER_CATALOG: readonly string[] = ["gpt-5.5", "gpt-5.4"];
 
 export default function CodexFastTierTab() {
   const [enabled, setEnabled] = useState(false);
+  const [tier, setTier] = useState<TierValue>("priority");
+  const [supportedModels, setSupportedModels] = useState<string[]>(
+    [...CODEX_FAST_TIER_DEFAULT_SUPPORTED_MODELS]
+  );
   const [loading, setLoading] = useState(true);
   const [saving, setSaving] = useState(false);
   const [status, setStatus] = useState<"" | "saved" | "error">("");
+  const [modelsOpen, setModelsOpen] = useState(false);
   const t = useTranslations("settings");
 
   useEffect(() => {
@@ -18,7 +33,10 @@ export default function CodexFastTierTab() {
       .then((res) => res.json())
       .then((data) => {
         if (cancelled) return;
-        setEnabled(isCodexGlobalFastServiceTierEnabled(data));
+        const resolved = resolveCodexGlobalFastServiceTier(data);
+        setEnabled(resolved.enabled);
+        setTier(resolved.tier);
+        setSupportedModels([...resolved.supportedModels]);
         setLoading(false);
       })
       .catch(() => {
@@ -29,33 +47,68 @@ export default function CodexFastTierTab() {
     };
   }, []);
 
-  const save = async (next: boolean) => {
+  const allCatalogModels = useMemo(() => {
+    // Union of the catalog and any custom models the user has stored, so we don't
+    // silently drop a slug the user added on a future Codex release.
+    const set = new Set<string>([...CODEX_FAST_TIER_CATALOG, ...supportedModels]);
+    return Array.from(set);
+  }, [supportedModels]);
+
+  const save = async (next: {
+    enabled?: boolean;
+    tier?: TierValue;
+    supportedModels?: string[];
+  }) => {
     if (saving || loading) return;
     setSaving(true);
     setStatus("");
-    const previous = enabled;
-    setEnabled(next);
+    const previous = { enabled, tier, supportedModels };
+    const merged = {
+      enabled: next.enabled ?? enabled,
+      tier: next.tier ?? tier,
+      supportedModels: next.supportedModels ?? supportedModels,
+    };
+    setEnabled(merged.enabled);
+    setTier(merged.tier);
+    setSupportedModels(merged.supportedModels);
     try {
       const res = await fetch("/api/settings", {
         method: "PATCH",
         headers: { "Content-Type": "application/json" },
-        body: JSON.stringify({ codexServiceTier: { enabled: next } }),
+        body: JSON.stringify({
+          codexServiceTier: {
+            enabled: merged.enabled,
+            tier: merged.tier,
+            supportedModels: merged.supportedModels,
+          },
+        }),
       });
       if (res.ok) {
         setStatus("saved");
         setTimeout(() => setStatus(""), 2000);
       } else {
-        setEnabled(previous);
+        setEnabled(previous.enabled);
+        setTier(previous.tier);
+        setSupportedModels(previous.supportedModels);
         setStatus("error");
       }
     } catch {
-      setEnabled(previous);
+      setEnabled(previous.enabled);
+      setTier(previous.tier);
+      setSupportedModels(previous.supportedModels);
       setStatus("error");
     } finally {
       setSaving(false);
     }
   };
 
+  const toggleModel = (slug: string, checked: boolean) => {
+    const next = checked
+      ? Array.from(new Set([...supportedModels, slug]))
+      : supportedModels.filter((m) => m !== slug);
+    save({ supportedModels: next });
+  };
+
   return (
     <Card>
       <div className="flex items-center gap-3 mb-3">
@@ -83,14 +136,73 @@ export default function CodexFastTierTab() {
           )}
           <Toggle
             checked={enabled}
-            onChange={(value) => save(value)}
+            onChange={(value) => save({ enabled: value })}
             disabled={loading || saving}
             ariaLabel={t("codexFastTierTitle")}
           />
         </div>
       </div>
 
-      <p className="text-xs text-text-muted/80 flex items-start gap-1.5 leading-relaxed">
+      {enabled && (
+        <div className="mt-4 flex flex-col gap-4 border-t border-border pt-4">
+          <Select
+            label={t("codexFastTierTierLabel")}
+            value={tier}
+            disabled={loading || saving}
+            onChange={(e) => save({ tier: e.target.value as TierValue })}
+            options={[
+              { value: "priority", label: t("codexFastTierTierPriority") },
+              { value: "flex", label: t("codexFastTierTierFlex") },
+              { value: "default", label: t("codexFastTierTierDefault") },
+            ]}
+          />
+
+          <div>
+            <button
+              type="button"
+              className="flex items-center gap-1.5 text-sm font-medium text-text-main hover:text-text-muted"
+              onClick={() => setModelsOpen((open) => !open)}
+              aria-expanded={modelsOpen}
+            >
+              <span className="material-symbols-outlined text-[18px]" aria-hidden="true">
+                {modelsOpen ? "expand_less" : "expand_more"}
+              </span>
+              {t("codexFastTierModelsLabel")}
+              <span className="ml-1 text-xs text-text-muted">
+                ({supportedModels.length})
+              </span>
+            </button>
+            {modelsOpen && (
+              <div className="mt-3 pl-6 flex flex-col gap-2">
+                <p className="text-xs text-text-muted/80">
+                  {t("codexFastTierModelsHint")}
+                </p>
+                {allCatalogModels.map((slug) => {
+                  const checked = supportedModels.includes(slug);
+                  return (
+                    <label
+                      key={slug}
+                      className="flex items-center gap-2 text-sm cursor-pointer"
+                    >
+                      <input
+                        type="checkbox"
+                        className="h-4 w-4"
+                        checked={checked}
+                        disabled={loading || saving}
+                        onChange={(e) => toggleModel(slug, e.target.checked)}
+                        aria-label={t("codexFastTierModelCheckbox", { model: slug })}
+                      />
+                      <span className="font-mono text-xs">{slug}</span>
+                    </label>
+                  );
+                })}
+              </div>
+            )}
+          </div>
+        </div>
+      )}
+
+      <p className="mt-4 text-xs text-text-muted/80 flex items-start gap-1.5 leading-relaxed">
         <span className="material-symbols-outlined text-[14px] mt-0.5">info</span>
         <span>{t("codexFastTierHint")}</span>
       </p>
diff --git a/src/i18n/messages/ar.json b/src/i18n/messages/ar.json
index 2e3a80cb86..d3c8845c79 100644
--- a/src/i18n/messages/ar.json
+++ b/src/i18n/messages/ar.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/az.json b/src/i18n/messages/az.json
index 93b8f47cfc..fb07678d28 100644
--- a/src/i18n/messages/az.json
+++ b/src/i18n/messages/az.json
@@ -3873,7 +3873,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/bg.json b/src/i18n/messages/bg.json
index 3f6a4e9f5f..738038cd9b 100644
--- a/src/i18n/messages/bg.json
+++ b/src/i18n/messages/bg.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/bn.json b/src/i18n/messages/bn.json
index 0e15d82dba..2fb7dd0e44 100644
--- a/src/i18n/messages/bn.json
+++ b/src/i18n/messages/bn.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/cs.json b/src/i18n/messages/cs.json
index b26e553f28..e051b840fe 100644
--- a/src/i18n/messages/cs.json
+++ b/src/i18n/messages/cs.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/da.json b/src/i18n/messages/da.json
index c418eeb5ac..4dddf96444 100644
--- a/src/i18n/messages/da.json
+++ b/src/i18n/messages/da.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/de.json b/src/i18n/messages/de.json
index 298b21e5b6..a46833b347 100644
--- a/src/i18n/messages/de.json
+++ b/src/i18n/messages/de.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "Codex Fast Tier",
     "codexFastTierDesc": "service_tier=priority global für OpenAI Codex-Anfragen einfügen.",
     "codexFastTierHint": "Wenn aktiviert, fügt OmniRoute ausgehenden Codex-Anfragen service_tier=priority hinzu, sofern für die Verbindung noch kein Tier festgelegt ist. Der Priority-Tier erfordert einen OpenAI Enterprise API-Schlüssel oder den ChatGPT-Auth-Codex-Pfad; andere Schlüsseltypen erhalten von OpenAI einen tier-bezogenen Fehler. Pro-Verbindung-Einstellungen auf der Codex-Provider-Seite haben Vorrang.",
-    "codexFastTierSaveError": "Codex Fast Tier-Einstellung konnte nicht aktualisiert werden"
+    "codexFastTierSaveError": "Codex Fast Tier-Einstellung konnte nicht aktualisiert werden",
+    "codexFastTierTierLabel": "Tier",
+    "codexFastTierTierDefault": "Standard (keine Überschreibung)",
+    "codexFastTierTierPriority": "Priority (Fast)",
+    "codexFastTierTierFlex": "Flex",
+    "codexFastTierModelsLabel": "Angewendet auf Modelle",
+    "codexFastTierModelsHint": "Wird nur wirksam, wenn das Zielmodell der Anfrage in der ausgewählten Liste enthalten ist. Die Standardauswahl entspricht den von OpenAI als Fast-fähig markierten Codex-Modellen.",
+    "codexFastTierModelCheckbox": "Tier-Überschreibung auf {model} anwenden"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/en.json b/src/i18n/messages/en.json
index 42ab8b8248..41f7e9b4d2 100644
--- a/src/i18n/messages/en.json
+++ b/src/i18n/messages/en.json
@@ -4531,7 +4531,14 @@
     "codexFastTierTitle": "Codex Fast Tier",
     "codexFastTierDesc": "Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "Tier",
+    "codexFastTierTierDefault": "Default (no override)",
+    "codexFastTierTierPriority": "Priority (Fast)",
+    "codexFastTierTierFlex": "Flex",
+    "codexFastTierModelsLabel": "Applied to models",
+    "codexFastTierModelsHint": "Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/es.json b/src/i18n/messages/es.json
index 6f556a2fde..36742aafec 100644
--- a/src/i18n/messages/es.json
+++ b/src/i18n/messages/es.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "Codex Fast Tier",
     "codexFastTierDesc": "Inyectar globalmente service_tier=priority para las solicitudes de OpenAI Codex.",
     "codexFastTierHint": "Cuando está habilitado, OmniRoute añade service_tier=priority a las solicitudes salientes de Codex para las conexiones que aún no especifican un tier. El tier priority requiere una clave API de OpenAI Enterprise o la ruta de Codex con autenticación ChatGPT; otros tipos de claves recibirán un error relacionado con el tier de OpenAI. Los ajustes por conexión en la página del proveedor Codex tienen prioridad.",
-    "codexFastTierSaveError": "Error al actualizar el ajuste de Codex Fast Tier"
+    "codexFastTierSaveError": "Error al actualizar el ajuste de Codex Fast Tier",
+    "codexFastTierTierLabel": "Tier",
+    "codexFastTierTierDefault": "Predeterminado (sin sobrescritura)",
+    "codexFastTierTierPriority": "Priority (Fast)",
+    "codexFastTierTierFlex": "Flex",
+    "codexFastTierModelsLabel": "Aplicado a los modelos",
+    "codexFastTierModelsHint": "Solo surte efecto cuando el modelo de destino de la solicitud está en la lista seleccionada. La selección predeterminada coincide con los modelos Codex elegibles para Fast de OpenAI.",
+    "codexFastTierModelCheckbox": "Aplicar la sobrescritura de tier a {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/fa.json b/src/i18n/messages/fa.json
index e518417cc7..db88247d07 100644
--- a/src/i18n/messages/fa.json
+++ b/src/i18n/messages/fa.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/fi.json b/src/i18n/messages/fi.json
index 5ab5af9d36..76feef3558 100644
--- a/src/i18n/messages/fi.json
+++ b/src/i18n/messages/fi.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/fr.json b/src/i18n/messages/fr.json
index 32b0035749..d2bf644422 100644
--- a/src/i18n/messages/fr.json
+++ b/src/i18n/messages/fr.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "Codex Fast Tier",
     "codexFastTierDesc": "Injecter globalement service_tier=priority pour les requêtes OpenAI Codex.",
     "codexFastTierHint": "Lorsqu'activé, OmniRoute ajoute service_tier=priority aux requêtes Codex sortantes pour les connexions qui n'ont pas déjà défini un tier. Le tier priority nécessite une clé API OpenAI Enterprise ou le chemin Codex avec authentification ChatGPT ; les autres types de clés recevront une erreur liée au tier de la part d'OpenAI. Les paramètres par connexion sur la page du provider Codex prévalent.",
-    "codexFastTierSaveError": "Échec de la mise à jour du paramètre Codex Fast Tier"
+    "codexFastTierSaveError": "Échec de la mise à jour du paramètre Codex Fast Tier",
+    "codexFastTierTierLabel": "Tier",
+    "codexFastTierTierDefault": "Par défaut (aucune surcharge)",
+    "codexFastTierTierPriority": "Priority (Fast)",
+    "codexFastTierTierFlex": "Flex",
+    "codexFastTierModelsLabel": "Appliqué aux modèles",
+    "codexFastTierModelsHint": "Prend effet uniquement lorsque le modèle cible de la requête figure dans la liste sélectionnée. La sélection par défaut correspond aux modèles Codex éligibles au tier Fast d'OpenAI.",
+    "codexFastTierModelCheckbox": "Appliquer la surcharge de tier à {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/gu.json b/src/i18n/messages/gu.json
index 805aaf0d9e..2a9cc758cf 100644
--- a/src/i18n/messages/gu.json
+++ b/src/i18n/messages/gu.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/he.json b/src/i18n/messages/he.json
index afb300292a..f30b347203 100644
--- a/src/i18n/messages/he.json
+++ b/src/i18n/messages/he.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/hi.json b/src/i18n/messages/hi.json
index bc24cba4a7..14bd47e8a5 100644
--- a/src/i18n/messages/hi.json
+++ b/src/i18n/messages/hi.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/hu.json b/src/i18n/messages/hu.json
index 1ee976dc1f..c410b0754b 100644
--- a/src/i18n/messages/hu.json
+++ b/src/i18n/messages/hu.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/id.json b/src/i18n/messages/id.json
index e7bcfa9b07..38f336d597 100644
--- a/src/i18n/messages/id.json
+++ b/src/i18n/messages/id.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/in.json b/src/i18n/messages/in.json
index b2e6964dc0..c28cd17f68 100644
--- a/src/i18n/messages/in.json
+++ b/src/i18n/messages/in.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/it.json b/src/i18n/messages/it.json
index 901e69fd7c..8c1606b55e 100644
--- a/src/i18n/messages/it.json
+++ b/src/i18n/messages/it.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/ja.json b/src/i18n/messages/ja.json
index e05b26b448..155c4de1fc 100644
--- a/src/i18n/messages/ja.json
+++ b/src/i18n/messages/ja.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/ko.json b/src/i18n/messages/ko.json
index 1c5f9d4ac1..30f456e492 100644
--- a/src/i18n/messages/ko.json
+++ b/src/i18n/messages/ko.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/mr.json b/src/i18n/messages/mr.json
index 7704973d8b..46ca370a38 100644
--- a/src/i18n/messages/mr.json
+++ b/src/i18n/messages/mr.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/ms.json b/src/i18n/messages/ms.json
index 2cb29af364..ded8062aa2 100644
--- a/src/i18n/messages/ms.json
+++ b/src/i18n/messages/ms.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/nl.json b/src/i18n/messages/nl.json
index d838006e86..60ddab6d6a 100644
--- a/src/i18n/messages/nl.json
+++ b/src/i18n/messages/nl.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/no.json b/src/i18n/messages/no.json
index ef10fd7456..2660df198f 100644
--- a/src/i18n/messages/no.json
+++ b/src/i18n/messages/no.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/phi.json b/src/i18n/messages/phi.json
index 54e663e101..3ec9d7138d 100644
--- a/src/i18n/messages/phi.json
+++ b/src/i18n/messages/phi.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/pl.json b/src/i18n/messages/pl.json
index 8981a6d801..6dbe963a7b 100644
--- a/src/i18n/messages/pl.json
+++ b/src/i18n/messages/pl.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/pt-BR.json b/src/i18n/messages/pt-BR.json
index f0212b0bbd..7dd8a57826 100644
--- a/src/i18n/messages/pt-BR.json
+++ b/src/i18n/messages/pt-BR.json
@@ -3972,7 +3972,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "Motor RTK",
diff --git a/src/i18n/messages/pt.json b/src/i18n/messages/pt.json
index 653be9deec..e6ab349c78 100644
--- a/src/i18n/messages/pt.json
+++ b/src/i18n/messages/pt.json
@@ -3967,7 +3967,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/ro.json b/src/i18n/messages/ro.json
index 5da81c6c6a..fe1ffaf424 100644
--- a/src/i18n/messages/ro.json
+++ b/src/i18n/messages/ro.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/ru.json b/src/i18n/messages/ru.json
index 975a5be4fa..6afb36407f 100644
--- a/src/i18n/messages/ru.json
+++ b/src/i18n/messages/ru.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/sk.json b/src/i18n/messages/sk.json
index a8cd6eaa2e..4c2d83189a 100644
--- a/src/i18n/messages/sk.json
+++ b/src/i18n/messages/sk.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/sv.json b/src/i18n/messages/sv.json
index 9bc4d7d697..a26e142f56 100644
--- a/src/i18n/messages/sv.json
+++ b/src/i18n/messages/sv.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/sw.json b/src/i18n/messages/sw.json
index b2e6964dc0..c28cd17f68 100644
--- a/src/i18n/messages/sw.json
+++ b/src/i18n/messages/sw.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/ta.json b/src/i18n/messages/ta.json
index 377ee4f2c0..df1861f27b 100644
--- a/src/i18n/messages/ta.json
+++ b/src/i18n/messages/ta.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/te.json b/src/i18n/messages/te.json
index 975e4fc01a..555b865d8a 100644
--- a/src/i18n/messages/te.json
+++ b/src/i18n/messages/te.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/th.json b/src/i18n/messages/th.json
index 00ee842a5c..4aa3255dcf 100644
--- a/src/i18n/messages/th.json
+++ b/src/i18n/messages/th.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/tr.json b/src/i18n/messages/tr.json
index 401c5ae0c3..ea7ef3a3fa 100644
--- a/src/i18n/messages/tr.json
+++ b/src/i18n/messages/tr.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/uk-UA.json b/src/i18n/messages/uk-UA.json
index 7f97aad7e4..306c67e057 100644
--- a/src/i18n/messages/uk-UA.json
+++ b/src/i18n/messages/uk-UA.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/ur.json b/src/i18n/messages/ur.json
index 5cb8845c6d..1f10ea9c54 100644
--- a/src/i18n/messages/ur.json
+++ b/src/i18n/messages/ur.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/vi.json b/src/i18n/messages/vi.json
index ecd98554c6..85fd7bb4c4 100644
--- a/src/i18n/messages/vi.json
+++ b/src/i18n/messages/vi.json
@@ -3970,7 +3970,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK Engine",
diff --git a/src/i18n/messages/zh-CN.json b/src/i18n/messages/zh-CN.json
index 08f3ebc0c4..6896f6838c 100644
--- a/src/i18n/messages/zh-CN.json
+++ b/src/i18n/messages/zh-CN.json
@@ -4002,7 +4002,14 @@
     "codexFastTierTitle": "__MISSING__:Codex Fast Tier",
     "codexFastTierDesc": "__MISSING__:Globally inject service_tier=priority for OpenAI Codex requests.",
     "codexFastTierHint": "__MISSING__:When enabled, OmniRoute adds service_tier=priority to outbound Codex requests for connections that don't already specify a tier. Priority tier requires an OpenAI Enterprise API key or the ChatGPT-auth Codex path; other key types will receive a tier-related error from OpenAI. Per-connection settings on the Codex provider page take precedence.",
-    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting"
+    "codexFastTierSaveError": "__MISSING__:Failed to update Codex Fast Tier setting",
+    "codexFastTierTierLabel": "__MISSING__:Tier",
+    "codexFastTierTierDefault": "__MISSING__:Default (no override)",
+    "codexFastTierTierPriority": "__MISSING__:Priority (Fast)",
+    "codexFastTierTierFlex": "__MISSING__:Flex",
+    "codexFastTierModelsLabel": "__MISSING__:Applied to models",
+    "codexFastTierModelsHint": "__MISSING__:Only takes effect when the request target model is in the selected list. Default selection matches OpenAI Fast-eligible Codex models.",
+    "codexFastTierModelCheckbox": "__MISSING__:Apply tier override to {model}"
   },
   "contextRtk": {
     "title": "RTK 引擎",
diff --git a/src/lib/providers/codexFastTier.ts b/src/lib/providers/codexFastTier.ts
index d74ec03ff0..cdcc1337c5 100644
--- a/src/lib/providers/codexFastTier.ts
+++ b/src/lib/providers/codexFastTier.ts
@@ -6,20 +6,72 @@ function asRecord(value: unknown): JsonRecord {
   return value && typeof value === "object" && !Array.isArray(value) ? (value as JsonRecord) : {};
 }
 
-export function isCodexGlobalFastServiceTierEnabled(settings: unknown): boolean {
+export type CodexFastTierValue = "priority" | "flex";
+
+export const CODEX_FAST_TIER_DEFAULT_SUPPORTED_MODELS: readonly string[] = [
+  "gpt-5.5",
+  "gpt-5.4",
+];
+
+export interface CodexGlobalFastServiceTierResolved {
+  enabled: boolean;
+  tier: CodexFastTierValue;
+  supportedModels: readonly string[];
+}
+
+/**
+ * Resolve the global Codex Fast Tier settings. Handles three legacy shapes:
+ *  - { codexServiceTier: true }                      (oldest boolean)
+ *  - { codexServiceTier: { enabled: true } }         (PR #2440 shape)
+ *  - { codexServiceTier: { enabled, tier, supportedModels } } (this follow-up)
+ *  - { codexFastServiceTier: true }                  (very early flag)
+ *
+ * Defaults when fields are absent on an enabled config:
+ *  - tier            = "priority"  (back-compat: PR #2440 only injected priority)
+ *  - supportedModels = ["gpt-5.5", "gpt-5.4"] (OpenAI Fast-eligible per models_cache.json)
+ */
+export function resolveCodexGlobalFastServiceTier(
+  settings: unknown
+): CodexGlobalFastServiceTierResolved {
   const record = asRecord(settings);
-  const codexServiceTier = record.codexServiceTier;
+  const raw = record.codexServiceTier;
 
-  if (typeof codexServiceTier === "boolean") {
-    return codexServiceTier;
+  let enabled = false;
+  let tier: CodexFastTierValue = "priority";
+  let supportedModels: readonly string[] = CODEX_FAST_TIER_DEFAULT_SUPPORTED_MODELS;
+
+  if (typeof raw === "boolean") {
+    enabled = raw;
+  } else if (raw && typeof raw === "object" && !Array.isArray(raw)) {
+    const obj = raw as JsonRecord;
+    if (obj.enabled === true) enabled = true;
+
+    if (typeof obj.tier === "string") {
+      const t = obj.tier.trim().toLowerCase();
+      if (t === "priority" || t === "flex") {
+        tier = t;
+      } else if (t === "default") {
+        // Explicit "default" means: do not inject any override.
+        enabled = false;
+      }
+    }
+
+    if (Array.isArray(obj.supportedModels)) {
+      const list = obj.supportedModels
+        .filter((m): m is string => typeof m === "string")
+        .map((m) => m.trim())
+        .filter((m) => m.length > 0);
+      if (list.length > 0) supportedModels = list;
+    }
+  } else if (record.codexFastServiceTier === true) {
+    enabled = true;
   }
 
-  const codexServiceTierRecord = asRecord(codexServiceTier);
-  if (codexServiceTierRecord.enabled === true) {
-    return true;
-  }
+  return { enabled, tier, supportedModels };
+}
 
-  return record.codexFastServiceTier === true;
+export function isCodexGlobalFastServiceTierEnabled(settings: unknown): boolean {
+  return resolveCodexGlobalFastServiceTier(settings).enabled;
 }
 
 export function getCodexEffectiveFastServiceTier(
@@ -32,13 +84,55 @@ export function getCodexEffectiveFastServiceTier(
   );
 }
 
+function modelMatchesSupportedList(
+  model: string | null | undefined,
+  supportedModels: readonly string[]
+): boolean {
+  if (typeof model !== "string" || model.length === 0) return false;
+  const normalizedModel = model.trim().toLowerCase();
+  if (!normalizedModel) return false;
+  for (const supported of supportedModels) {
+    const candidate = supported.trim().toLowerCase();
+    if (!candidate) continue;
+    if (normalizedModel === candidate || normalizedModel.startsWith(candidate)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+export interface ApplyCodexGlobalFastServiceTierOptions {
+  /**
+   * Target model for the current request. When provided, the global override is only
+   * injected if the model matches the user-selected supportedModels list.
+   * When omitted, the gate is skipped (back-compat with the original signature).
+   */
+  model?: string | null;
+  /**
+   * Outbound request body. When provided and the tier is "flex", the helper writes
+   * body.service_tier directly so the value survives the requestDefaults normalizer
+   * (which only canonicalizes priority/fast). Per-request body.service_tier is left
+   * untouched if already set.
+   */
+  body?: Record<string, unknown> | null;
+}
+
 export function applyCodexGlobalFastServiceTier<T extends JsonRecord | null | undefined>(
   provider: string | null | undefined,
   credentials: T,
-  settings: unknown
+  settings: unknown,
+  options: ApplyCodexGlobalFastServiceTierOptions = {}
 ): T {
-  if (provider !== "codex" || !isCodexGlobalFastServiceTierEnabled(settings)) {
-    return credentials;
+  if (provider !== "codex") return credentials;
+
+  const resolved = resolveCodexGlobalFastServiceTier(settings);
+  if (!resolved.enabled) return credentials;
+
+  // Per-model gate. Skip when caller did not pass a model (back-compat call sites).
+  if (options.model !== undefined) {
+    if (!modelMatchesSupportedList(options.model, resolved.supportedModels)) {
+      return credentials;
+    }
   }
 
   if (!credentials || typeof credentials !== "object" || Array.isArray(credentials)) {
@@ -48,10 +142,27 @@ export function applyCodexGlobalFastServiceTier<T extends JsonRecord | null | un
   const providerSpecificData = asRecord(credentials.providerSpecificData);
   const requestDefaults = asRecord(providerSpecificData.requestDefaults);
 
+  // Per-connection requestDefaults.serviceTier wins over global. Mirrors the
+  // executor's body.service_tier > requestDefaults.serviceTier > global precedence.
   if (normalizeCodexServiceTier(requestDefaults.serviceTier)) {
     return credentials;
   }
 
+  if (resolved.tier === "flex") {
+    // requestDefaults.serviceTier is normalized downstream and "flex" would be stripped.
+    // Write to the outbound body instead, but only if the caller did not already set it.
+    const body = options.body;
+    if (body && typeof body === "object" && !Array.isArray(body)) {
+      const existing = (body as JsonRecord).service_tier;
+      if (typeof existing !== "string" || existing.trim().length === 0) {
+        (body as JsonRecord).service_tier = "flex";
+      }
+    }
+    return credentials;
+  }
+
+  // tier === "priority": existing behavior — inject via requestDefaults so the
+  // executor's normal precedence chain picks it up and cost accounting reflects it.
   return {
     ...credentials,
     providerSpecificData: {
diff --git a/src/shared/validation/settingsSchemas.ts b/src/shared/validation/settingsSchemas.ts
index d808007b32..bd7000b0cb 100644
--- a/src/shared/validation/settingsSchemas.ts
+++ b/src/shared/validation/settingsSchemas.ts
@@ -37,7 +37,13 @@ export const updateSettingsSchema = z.object({
   debugMode: z.boolean().optional(),
   hiddenSidebarItems: z.array(z.enum(HIDEABLE_SIDEBAR_ITEM_IDS)).optional(),
   comboConfigMode: z.enum(COMBO_CONFIG_MODES).optional(),
-  codexServiceTier: z.object({ enabled: z.boolean() }).optional(),
+  codexServiceTier: z
+    .object({
+      enabled: z.boolean().optional(),
+      tier: z.enum(["default", "priority", "flex"]).optional(),
+      supportedModels: z.array(z.string().max(200)).max(200).optional(),
+    })
+    .optional(),
   // Routing settings (#134)
   fallbackStrategy: z.enum(ACCOUNT_FALLBACK_STRATEGY_VALUES).optional(),
   wildcardAliases: z.array(z.object({ pattern: z.string(), target: z.string() })).optional(),