fix: accept vLLM thinking in reasoning or reasoning_content

Newer vLLM parsers put CoT in reasoning; older builds and DeepSeek still use reasoning_content. Canonicalize to the UI field and echo only the original wire field so other ChatOpenAI models stay unchanged. Point qwen3.6 at VllmChatModel.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend-web/src/core/messages/utils.ts

@@ -364,11 +364,16 @@ export function extractReasoningContentFromMessage(message: Message) {
   if (message.type !== "ai") {
     return null;
   }
-  if (
-    message.additional_kwargs &&
-    "reasoning_content" in message.additional_kwargs
-  ) {
-    return message.additional_kwargs.reasoning_content as string | null;
+  if (message.additional_kwargs) {
+    const reasoningContent = message.additional_kwargs.reasoning_content;
+    if (typeof reasoningContent === "string") {
+      return reasoningContent;
+    }
+    // Newer vLLM puts thinking in `reasoning` instead of `reasoning_content`.
+    const reasoning = message.additional_kwargs.reasoning;
+    if (typeof reasoning === "string") {
+      return reasoning;
+    }
   }
   if (Array.isArray(message.content)) {
     const part = message.content[0];
@@ -424,6 +429,9 @@ export function hasReasoning(message: Message) {
   if (typeof message.additional_kwargs?.reasoning_content === "string") {
     return true;
   }
+  if (typeof message.additional_kwargs?.reasoning === "string") {
+    return true;
+  }
   if (Array.isArray(message.content)) {
     const part = message.content[0];
     // Compatible with the Anthropic gateway