logprobs not returned when using the response api

### Checked other resources - [x] This is a bug, not a usage question. - [x] I added a clear and descriptive title that summarizes this issue. - [x] I used the GitHub search to find a similar question and didn't find it. - [x] I am sure that this is a bug in LangChain rather than my code. - [x] The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package). - [x] This is not related to the langchain-community package. - [x] I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS. ### Package (Required) - [ ] langchain - [x] langchain-openai - [ ] langchain-anthropic - [ ] langchain-classic - [ ] langchain-core - [ ] langchain-model-profiles - [ ] langchain-tests - [ ] langchain-text-splitters - [ ] langchain-chroma - [ ] langchain-deepseek - [ ] langchain-exa - [ ] langchain-fireworks - [ ] langchain-groq - [ ] langchain-huggingface - [ ] langchain-mistralai - [ ] langchain-nomic - [ ] langchain-ollama - [ ] langchain-openrouter - [ ] langchain-perplexity - [ ] langchain-qdrant - [ ] langchain-xai - [ ] Other / not sure / general ### Related Issues / PRs ### Reproduction Steps / Example Code (Python) ```python from langchain_openai import ChatOpenAI client = ChatOpenAI( model="gpt-5.2", use_responses_api=True, logprobs=True ) response = client.invoke("say hello world") ``` ### Error Message and Stack Trace (if applicable) ```shell Traceback (most recent call last): File "<input>", line 12, in <module> File "C:\Users\ml-na\PycharmProjects\pipeline-llm\.venv\Lib\site-packages\langchain_core\language_models\chat_models.py", line 402, in invoke self.generate_prompt( ~~~~~~~~~~~~~~~~~~~~^ [self._convert_input(input)], ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...<6 lines>... **kwargs, ^^^^^^^^^ ).generations[0][0], ^ File "C:\Users\ml-na\PycharmProjects\pipeline-llm\.venv\Lib\site-packages\langchain_core\language_model…