VideoContentBlock ValueError: Block of type video is not supported

### Submission checklist - [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 - [x] 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 VideoContentBlock ValueError: Block of type video is not supported ### Reproduction Steps / Example Code (Python) ```python from langchain.messages import VideoContentBlock, HumanMessage, TextContentBlock from langchain.chat_models import init_chat_model model = init_chat_model( model="qwen3.6-35b-a3b", base_url="https://dashscope.aliyuncs.com/compatible-mode/v1" ) messages = HumanMessage(content_blocks=[ TextContentBlock(text="描述一下这个视频？", type="text"), VideoContentBlock(url="https://test.com/test.mp4", type="video", mime_type="video/mp4") ]) response = model.invoke([messages]) ``` ### Error Message and Stack Trace (if applicable) ```shell File ~/project/python/me/langchain-example/.venv/lib/python3.12/site-packages/langchain_core/messages/block_translators/openai.py:150, in convert_to_openai_data_block(block, api)…