A 2 AM Serialization Bug in LangChain Memory — And How pytest Stopped It Forever

At 2:17 AM, my monitoring alert yanked me out of sleep: the customer service bot had suddenly lost its memory. Users were asking “Where is my order?” three times in a row, and it kept asking for their phone number as if they were complete strangers. I opened the logs and saw that ConversationBufferMemory was loading empty message lists. The key was still there in Redis, but somehow deserialization had silently swallowed the data. I rolled back the code from my bed and spent three hours tracing t