diff --git a/src/resources/extensions/sf/preferences-validation.ts b/src/resources/extensions/sf/preferences-validation.ts
index f093fadc0..c7c4c253b 100644
--- a/src/resources/extensions/sf/preferences-validation.ts
+++ b/src/resources/extensions/sf/preferences-validation.ts
@@ -295,6 +295,20 @@ export function validatePreferences(preferences: SFPreferences): {
     }
   }
 
+  // ─── Service Tier ───────────────────────────────────────────────────
+  // OpenAI service tier for gpt-5.4 models. "off" explicitly disables the
+  // whole feature (hooks, footer, command refuse enable). Undefined = not
+  // configured. Historical gap: this field wasn't wired through validation
+  // so even "priority" / "flex" were being silently dropped.
+  if (preferences.service_tier !== undefined) {
+    const validTiers = new Set(["priority", "flex", "off"]);
+    if (typeof preferences.service_tier === "string" && validTiers.has(preferences.service_tier)) {
+      validated.service_tier = preferences.service_tier as SFPreferences["service_tier"];
+    } else {
+      errors.push(`service_tier must be one of: priority, flex, off`);
+    }
+  }
+
   // ─── Search Provider ─────────────────────────────────────────────
   if (preferences.search_provider !== undefined) {
     const validSearchProviders = new Set(["brave", "tavily", "ollama", "combosearch", "native", "auto"]);