diff --git a/frontend/package-lock.json b/frontend/package-lock.json
index db9a4ea..50ff9f5 100644
--- a/frontend/package-lock.json
+++ b/frontend/package-lock.json
@@ -333,8 +333,6 @@
       "integrity": "sha512-zLpS5asjEb7lq8jYLq37N6XKaE41DIexlY1rF/z4/tIl3wo13Sqm28fRyfIsKZD+NZ8mM5RoKkpW/rBcuoSZSg==",
       "dev": true,
       "license": "MIT",
-      "optional": true,
-      "peer": true,
       "dependencies": {
         "@emnapi/wasi-threads": "1.2.3",
         "tslib": "^2.4.0"
@@ -346,20 +344,6 @@
       "integrity": "sha512-Xz4Tpyki7XyrpbUK1jR1AhdAdaXyhhY4lZ3neLodmhpuWfy2PAQN5B46sAiU4liOXGLkHypn/qU+jvfWSCYYLA==",
       "dev": true,
       "license": "MIT",
-      "optional": true,
-      "peer": true,
-      "dependencies": {
-        "tslib": "^2.4.0"
-      }
-    },
-    "node_modules/@emnapi/wasi-threads": {
-      "version": "1.2.3",
-      "resolved": "https://registry.npmjs.org/@emnapi/wasi-threads/-/wasi-threads-1.2.3.tgz",
-      "integrity": "sha512-ELEBe8PsLvvJ6QMr0zLt8ffvOHW/dc1m3CEzNMg7aJUv3bMaoDtw2TXyDAwkYBuroxxuHEwhRTLJSe5sya547g==",
-      "dev": true,
-      "license": "MIT",
-      "optional": true,
-      "peer": true,
       "dependencies": {
         "tslib": "^2.4.0"
       }
@@ -4053,4 +4037,4 @@
       }
     }
   }
-}
\ No newline at end of file
+}
diff --git a/frontend/src/components/BuildingPopover/BuildingPopover.tsx b/frontend/src/components/BuildingPopover/BuildingPopover.tsx
index c6d5333..7018b89 100644
--- a/frontend/src/components/BuildingPopover/BuildingPopover.tsx
+++ b/frontend/src/components/BuildingPopover/BuildingPopover.tsx
@@ -495,12 +495,11 @@ export function BuildingPopover({
 
               <div className="popover-chat-input-row">
                 <input ref={inputRef} className="popover-chat-input" type="text"
-                  placeholder={`问问关于${building.name}的问题…`}
+                  placeholder={chatLoading ? 'AI 思考中…' : `问问关于${building.name}的问题…`}
                   value={chatInput} onChange={e => setChatInput(e.target.value)}
                   onKeyDown={e => { if (e.key === 'Enter' && !e.shiftKey) { e.preventDefault(); sendQuestion(); } }}
                   onFocus={() => { inputBlurGuard.current = false; }}
-                  onBlur={() => { inputBlurGuard.current = true; setTimeout(() => { inputBlurGuard.current = false; }, 300); }}
-                  disabled={chatLoading} />
+                  onBlur={() => { inputBlurGuard.current = true; setTimeout(() => { inputBlurGuard.current = false; }, 300); }} />
                 <button className="popover-chat-send" onClick={sendQuestion}
                   disabled={!chatInput.trim() || chatLoading} aria-label="发送">
                   <svg width="14" height="14" viewBox="0 0 24 24" fill="none"
diff --git a/frontend/src/components/ChatWidget/ChatWidget.tsx b/frontend/src/components/ChatWidget/ChatWidget.tsx
index 25378b5..beda8ce 100644
--- a/frontend/src/components/ChatWidget/ChatWidget.tsx
+++ b/frontend/src/components/ChatWidget/ChatWidget.tsx
@@ -79,6 +79,13 @@ export function ChatWidget({ selectedBuilding, onViewBuilding }: ChatWidgetProps
         timestamp: Date.now(),
       }]);
       setSuggestions(getRelatedQuestions(text, 3));
+    }).catch(() => {
+      setMessages(prev => [...prev, {
+        id: `a-${Date.now()}`, role: 'assistant',
+        content: '抱歉，AI 服务暂时不可用，请稍后重试。',
+        timestamp: Date.now(),
+      }]);
+    }).finally(() => {
       setIsLoading(false);
     });
   }, [isLoading]);
diff --git a/functions/api/chat.js b/functions/api/chat.js
index c1e5e4c..8f64be6 100644
--- a/functions/api/chat.js
+++ b/functions/api/chat.js
@@ -63,23 +63,37 @@ export async function onRequestPost(context) {
             webResults = await searchWeb(env, question, 3);
         }
 
-        if (env.LLM_API_KEY && env.LLM_API_URL) {
-            answer = await callLLM(env, question, buildingId, buildingName, buildingCtx, qaContext, webResults);
+        if (bestScore >= 60 && qaContext.length > 0) {
+            answer = qaContext[0].answer;
+        } else if (env.LLM_API_KEY && env.LLM_API_URL) {
+            try {
+                answer = await callLLM(env, question, buildingId, buildingName, buildingCtx, qaContext, webResults);
+            } catch (llmErr) {
+                answer = qaContext.length > 0
+                    ? qaContext[0].answer
+                    : null;
+            }
         } else if (qaContext.length > 0) {
             answer = qaContext[0].answer;
         }
 
         if (!answer) {
-            answer = '\u667a\u80fd\u95ee\u7b54\u670d\u52a1\u6682\u672a\u914d\u7f6e\uff0c\u8bf7\u8054\u7cfb\u7ba1\u7406\u5458\u3002';
+            answer = env.LLM_API_KEY
+                ? '\u62b1\u6b49\uff0c\u668a\u80fd\u95ee\u7b54\u670d\u52a1\u6682\u65f6\u4e0d\u53ef\u7528\uff0c\u8bf7\u7a0d\u540e\u91cd\u8bd5\u3002'
+                : '\u667a\u80fd\u95ee\u7b54\u670d\u52a1\u6682\u672a\u914d\u7f6e\uff0c\u8bf7\u8054\u7cfb\u7ba1\u7406\u5458\u3002';
         }
 
         if (db) {
-            await db.prepare(
-                'INSERT INTO chat_logs (id, question, answer, building_id, building_name) VALUES (?, ?, ?, ?, ?)'
-            ).bind(
-                `chat-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`,
-                question, answer, buildingId || null, buildingName || null
-            ).run();
+            try {
+                await db.prepare(
+                    'INSERT INTO chat_logs (id, question, answer, building_id, building_name) VALUES (?, ?, ?, ?, ?)'
+                ).bind(
+                    `chat-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`,
+                    question, answer, buildingId || null, buildingName || null
+                ).run();
+            } catch (logErr) {
+                // 日志写入失败不影响主响应
+            }
         }
 
         return jsonResponse({ answer, sources });
@@ -94,7 +108,21 @@ export async function onRequestPost(context) {
 function jsonResponse(data, status = 200) {
     return new Response(JSON.stringify(data), {
         status,
-        headers: { 'Content-Type': 'application/json; charset=utf-8' },
+        headers: {
+            'Content-Type': 'application/json; charset=utf-8',
+            'Access-Control-Allow-Origin': '*',
+        },
+    });
+}
+
+export async function onRequestOptions() {
+    return new Response(null, {
+        status: 204,
+        headers: {
+            'Access-Control-Allow-Origin': '*',
+            'Access-Control-Allow-Methods': 'POST, OPTIONS',
+            'Access-Control-Allow-Headers': 'Content-Type',
+        },
     });
 }