ModulesOn this pageModulesLangChain provides standard, extendable interfaces and external integrations for the following modules, listed from least to most complex:Model I/O​Interface with language modelsRetrieval​Interface with application-specific dataChains​Construct sequences of callsAgents​Let chains choose which tools to use given high-level directivesMemory​Persist application state between runs of a chainCallbacks​Log and stream intermediate steps of any chainPreviousLangChain Expression Language (LCEL)NextModel I/O