Compared
LangMem is LangChain’s memory. This is a database that also plugs in.
LangMem’s README says it "helps agents learn and adapt from their interactions over time," extracts information from conversations, and integrates with LangGraph’s storage layer. The background manager it describes uses an LLM. The install line it publishes is pip install -U langmem, plus an API key for a model provider.
What they say they are
That is the LangMem README , fetched 30 September 2026. If you are all-in on LangGraph, it is the path its own maintainers ship. FluctlightDB’s LangChain adapter is FluctlightMemory and FluctlightChatMessageHistory. The page about it records a re-run from main in which .messages returned the session turns. That fix is not in the published package yet.
When to pick which
Pick LangMem when you want the memory tools LangGraph already knows. Pick FluctlightDB when the same brain should also be reachable from plain Python, and you want the durability of a directory you can checkpoint. The short form is on the comparison .