diff --git a/src/components/openclaw/AgentsDefaultsPanel.tsx b/src/components/openclaw/AgentsDefaultsPanel.tsx
index 03d5af3f9..c4a9abf18 100644
--- a/src/components/openclaw/AgentsDefaultsPanel.tsx
+++ b/src/components/openclaw/AgentsDefaultsPanel.tsx
@@ -17,7 +17,6 @@ const AgentsDefaultsPanel: React.FC = () => {
   const { data: agentsData, isLoading } = useOpenClawAgentsDefaults();
   const saveAgentsMutation = useSaveOpenClawAgentsDefaults();
   const [defaults, setDefaults] = useState<OpenClawAgentsDefaults | null>(null);
-  const [primaryModel, setPrimaryModel] = useState("");
   const [fallbacks, setFallbacks] = useState("");
 
   // Extra known fields from agents.defaults
@@ -26,13 +25,15 @@ const AgentsDefaultsPanel: React.FC = () => {
   const [contextTokens, setContextTokens] = useState("");
   const [maxConcurrent, setMaxConcurrent] = useState("");
 
+  // Primary model is read-only — set via the "Set as default model" button on provider cards
+  const primaryModel = agentsData?.model?.primary ?? "";
+
   useEffect(() => {
     // agentsData is undefined while loading, null when config section is absent
     if (agentsData === undefined) return;
     setDefaults(agentsData);
 
     if (agentsData) {
-      setPrimaryModel(agentsData.model?.primary ?? "");
       setFallbacks((agentsData.model?.fallbacks ?? []).join(", "));
 
       // Extract known extra fields
@@ -48,17 +49,21 @@ const AgentsDefaultsPanel: React.FC = () => {
       // Preserve all unknown fields from original data
       const updated: OpenClawAgentsDefaults = { ...defaults };
 
-      // Model configuration
+      // Model configuration — primary is read-only, preserve original value
       const fallbackList = fallbacks
         .split(",")
         .map((s) => s.trim())
         .filter(Boolean);
 
-      if (primaryModel.trim()) {
+      const origPrimary = defaults?.model?.primary;
+      if (origPrimary) {
         updated.model = {
-          primary: primaryModel.trim(),
+          primary: origPrimary,
           ...(fallbackList.length > 0 ? { fallbacks: fallbackList } : {}),
         };
+      } else if (fallbackList.length > 0) {
+        // No primary set but user provided fallbacks — keep fallbacks only
+        updated.model = { primary: "", fallbacks: fallbackList };
       }
 
       // Optional fields
@@ -122,12 +127,9 @@ const AgentsDefaultsPanel: React.FC = () => {
             <Label className="mb-1.5 block">
               {t("openclaw.agents.primaryModel")}
             </Label>
-            <Input
-              value={primaryModel}
-              onChange={(e) => setPrimaryModel(e.target.value)}
-              placeholder="provider/model-id"
-              className="font-mono text-xs"
-            />
+            <div className="h-9 px-3 flex items-center rounded-md border border-input bg-muted/50 font-mono text-xs text-muted-foreground">
+              {primaryModel || t("openclaw.agents.notSet")}
+            </div>
             <p className="text-xs text-muted-foreground mt-1">
               {t("openclaw.agents.primaryModelHint")}
             </p>
diff --git a/src/i18n/locales/en.json b/src/i18n/locales/en.json
index bba813d43..9e5a393fc 100644
--- a/src/i18n/locales/en.json
+++ b/src/i18n/locales/en.json
@@ -1218,7 +1218,8 @@
       "description": "Manage agents.defaults in openclaw.json (default model, runtime parameters, etc.)",
       "modelSection": "Model Configuration",
       "primaryModel": "Primary Model",
-      "primaryModelHint": "Format: provider/model-id",
+      "primaryModelHint": "Set via the \"Set as Default Model\" button in the provider list",
+      "notSet": "Not set",
       "fallbackModels": "Fallback Models",
       "fallbackModelsHint": "Comma-separated, ordered by priority",
       "runtimeSection": "Runtime Parameters",
diff --git a/src/i18n/locales/ja.json b/src/i18n/locales/ja.json
index d417863f1..4d1bedcb7 100644
--- a/src/i18n/locales/ja.json
+++ b/src/i18n/locales/ja.json
@@ -1218,7 +1218,8 @@
       "description": "openclaw.json の agents.defaults 設定を管理（デフォルトモデル、ランタイムパラメータなど）",
       "modelSection": "モデル設定",
       "primaryModel": "プライマリモデル",
-      "primaryModelHint": "形式: provider/model-id",
+      "primaryModelHint": "プロバイダ一覧の「デフォルトモデルに設定」ボタンで設定します",
+      "notSet": "未設定",
       "fallbackModels": "フォールバックモデル",
       "fallbackModelsHint": "カンマ区切り、優先度順",
       "runtimeSection": "ランタイムパラメータ",
diff --git a/src/i18n/locales/zh.json b/src/i18n/locales/zh.json
index 5c64357d9..df93dcb85 100644
--- a/src/i18n/locales/zh.json
+++ b/src/i18n/locales/zh.json
@@ -1218,7 +1218,8 @@
       "description": "管理 openclaw.json 中的 agents.defaults 配置（默认模型、运行参数等）",
       "modelSection": "模型配置",
       "primaryModel": "主模型",
-      "primaryModelHint": "格式：provider/model-id",
+      "primaryModelHint": "在供应商列表中通过「设为默认模型」按钮设置",
+      "notSet": "未设置",
       "fallbackModels": "回退模型",
       "fallbackModelsHint": "逗号分隔，按优先级排列",
       "runtimeSection": "运行参数",