LangChain Content Blocks (Python)

Overview

On Claude, AIMessage.content is list[dict] even for pure text — so any code from an OpenAI-first tutorial that calls message.content.lower() or message.content.split() crashes with AttributeError: 'list' object has no attribute 'lower' on the first production Claude call (P02). Multi-modal code that works on GPT-4o breaks on Claude because pre-1.0 image-block shapes differed across providers (P64). Multi-turn Claude replay with extended thinking fails with anthropic.BadRequestError: missing signature when prior thinking blocks are stripped. Forced tool_choice prevents stop_reason="end_turn" and loops forever (P63).

This is the deep-dive companion to langchain-model-inference. That skill's references/content-blocks.md covers the str vs list[dict] divergence and a safe text extractor. This skill goes further: