prebuilt==0.1.8

langgraph-prebuilt 0.1.8

Summary of Changes

• Added support for pre-model hooks in agent executors to handle long message histories through trimming or summarization (PR #4059)

Detailed Changes

langgraph.prebuilt.chat_agent_executor.create_react_agent

• Added new pre_model_hook parameter which lets you insert a custom node before LLM calls (PR #4059)
• The pre-model hook can modify message history or provide alternate messages for the LLM without affecting the state
• Useful for managing long conversations through message trimming, summarization, or other preprocessing
• Hook can return either messages (which updates state) or llm_input_messages (which only affects the LLM input)
• Extended graph structure to properly handle the hook in the control flow