xai: support live search (#31379)

https://docs.x.ai/docs/guides/live-search

libs/partners/xai/langchain_xai/chat_models.py

@@ -275,6 +275,8 @@ class ChatXAI(BaseChatOpenAI):  # type: ignore[override]
     """
     xai_api_base: str = Field(default="https://api.x.ai/v1/")
     """Base URL path for API requests."""
+    search_parameters: Optional[dict[str, Any]] = None
+    """Parameters for search requests. Example: ``{"mode": "auto"}``."""
 
     openai_api_key: Optional[SecretStr] = None
     openai_api_base: Optional[str] = None
@@ -371,6 +373,18 @@ class ChatXAI(BaseChatOpenAI):  # type: ignore[override]
             )
         return self
 
+    @property
+    def _default_params(self) -> dict[str, Any]:
+        """Get default parameters."""
+        params = super()._default_params
+        if self.search_parameters:
+            if "extra_body" in params:
+                params["extra_body"]["search_parameters"] = self.search_parameters
+            else:
+                params["extra_body"] = {"search_parameters": self.search_parameters}
+
+        return params
+
     def _create_chat_result(
         self,
         response: Union[dict, openai.BaseModel],
@@ -386,6 +400,11 @@ class ChatXAI(BaseChatOpenAI):  # type: ignore[override]
                 response.choices[0].message.reasoning_content  # type: ignore
             )
 
+        if hasattr(response, "citations"):
+            rtn.generations[0].message.additional_kwargs["citations"] = (
+                response.citations
+            )
+
         return rtn
 
     def _convert_chunk_to_generation_chunk(
@@ -407,6 +426,10 @@ class ChatXAI(BaseChatOpenAI):  # type: ignore[override]
                         reasoning_content
                     )
 
+        if (citations := chunk.get("citations")) and generation_chunk:
+            if isinstance(generation_chunk.message, AIMessageChunk):
+                generation_chunk.message.additional_kwargs["citations"] = citations
+
         return generation_chunk
 
     def with_structured_output(