LangChain Reference home page

GitHub
Main Docs

LangChain

Browser
Universal
Hub
Node
Load
Serializable
Encoder Backed
File System
In Memory
Tools

LangChain Core

Text Splitters

MCP Adapters

⌘I

LangChain Assistant

Ask a question to get started

Enter to send•Shift+Enter new line

Menu

Browser Universal Hub Node Load Serializable Encoder Backed File System In Memory Tools

Agents Caches Base Dispatch Web Manager Promises Chat History Context Base Langsmith Documents Embeddings Errors Example Selectors Indexing Base Chat Models Compat Event Llms Openai Completions Stream Profile Stream Structured Output Load Serializable Memory Messages Tool Output Parsers Openai Functions Openai Tools Outputs Prompt Values Prompts Retrievers Document Compressors Runnables Graph Singletons Stores Structured Query Testing Tools Base Console Log Stream Run Collector Tracer Langchain Stream Async Caller Chunk Array Context Env Event Source Parse Format Function Calling Hash Json Patch Json Schema Math Ssrf Standard Schema Stream Testing Tiktoken Types Uuid Vectorstores

Language

Theme

JavaScript@langchain/coremessagesMessageStructureproperties

Property●Since v1.0

properties

Copy

properties: Partial<__type>

View source on GitHub

Optional mapping of message types to arbitrary property objects. Allows attaching custom metadata or other information to specific message types.