LangChain xAI 1.2.0 improves streaming and token accounting; OpenAI adapter updates GPT-5 limits

LangChain xAI 1.2.0 improves streaming and token accounting; OpenAI adapter updates GPT-5 limits

LangChain released langchain-xai 1.2.0 with fixes that stream citations only once and enable usage metadata streaming by default, plus a core serialization patch. The OpenAI adapter now filters function_call blocks in token counting and updates max input tokens for the GPT-5 series, and chunk_position is standardized via langchain-core.