If you're building anything with LangChain, OpenAI's Python SDK, or LangGraph in

production, you've probably run into the same class of bugs that have been

quietly breaking real apps for months. Over the last week I dug through ~70

open issues across these libraries while doing client debugging work, and there

are five patterns that come up constantly — each with a non-obvious root

cause and a 5-line fix.

Here they are, ranked by how much pain they cause.

1. _create_usage_metadata crashes when service_tier is set and cached_tokens is missing

Repo: langchain-ai/langchain ( #36657 )

The trap:

prompt_details = response . get ( " prompt_details " , {}) prompt_details .…