diff --git a/server/src/llm/structuredInvoke.ts b/server/src/llm/structuredInvoke.ts
index 267187d19..a17833289 100644
--- a/server/src/llm/structuredInvoke.ts
+++ b/server/src/llm/structuredInvoke.ts
@@ -108,10 +108,17 @@ function tryFixTruncatedJson(raw: string): string {
   return fixed;
 }
 
+function unwrapSingletonArray(val: unknown): unknown {
+  if (Array.isArray(val) && val.length === 1) {
+    return val[0];
+  }
+  return val;
+}
+
 function tryParseStructuredJsonValue(source: string): { parsed: unknown } | { error: string } {
   try {
     return {
-      parsed: JSON.parse(extractJSONValue(source)) as unknown,
+      parsed: unwrapSingletonArray(JSON.parse(extractJSONValue(source))),
     };
   } catch (error) {
     const fixed = tryFixTruncatedJson(source);
@@ -126,7 +133,7 @@ function tryParseStructuredJsonValue(source: string): { parsed: unknown } | { er
 
     try {
       return {
-        parsed: JSON.parse(extractJSONValue(fixed)) as unknown,
+        parsed: unwrapSingletonArray(JSON.parse(extractJSONValue(fixed))),
       };
     } catch (fixedError) {
       return {
diff --git a/server/src/llm/structuredOutput.ts b/server/src/llm/structuredOutput.ts
index a5323a1f4..eca9c523e 100644
--- a/server/src/llm/structuredOutput.ts
+++ b/server/src/llm/structuredOutput.ts
@@ -355,6 +355,24 @@ export function classifyStructuredOutputFailure(input: {
   if (haystack.includes("zod") || haystack.includes("schema") || haystack.includes("校验错误")) {
     return "schema_mismatch";
   }
+  // Relay/proxy returned HTML instead of JSON (e.g. rate limit page, auth error page)
+  const lowerHaystack = haystack.toLowerCase();
+  if (
+    lowerHaystack.includes("<!doctype") ||
+    lowerHaystack.includes("<html") ||
+    lowerHaystack.includes("<body") ||
+    lowerHaystack.includes("</div>") ||
+    lowerHaystack.includes("</script>") ||
+    lowerHaystack.includes("rate limit") ||
+    lowerHaystack.includes("429") ||
+    lowerHaystack.includes("<title>error") ||
+    lowerHaystack.includes("<title>403") ||
+    lowerHaystack.includes("<title>404") ||
+    lowerHaystack.includes("<title>502") ||
+    lowerHaystack.includes("<title>503")
+  ) {
+    return "transport_error";
+  }
   return "transport_error";
 }