LangChain4j is an idiomatic, open-source Java library for building LLM-powered applications on the JVM. It offers a unified API over popular LLM providers and vector stores, and makes implementing tool calling (including MCP support), agents and RAG easy. It integrates seamlessly with enterprise Java frameworks like Quarkus and Spring Boot.
What it is, and how people use it
LangChain4j is an idiomatic, open-source Java library for building LLM-powered applications on the JVM. It offers a unified API over popular LLM providers and vector stores, and makes implementing tool calling (including MCP support), agents and RAG easy. It integrates seamlessly with enterprise Java frameworks like Quarkus and Spring Boot. It sits on the Dev Agents & Programs shelf of the catalog, maintained by @langchain4j.
Why builders keep it installedDev Agents & Programs benefits
These CLIs and dashboards solve one job well and install with a single command. Value shows up in the first hour, not after a config weekend.
Most of them ship an MCP server, skill or hooks - so the same tool you use manually becomes an action your agent can call safely.
Star counts here track repos people actually run daily: the issue history shows bug classes fixed under production pressure, not demo-week polish.
Every tool on this page ships under an open license and can be self-hosted. Your usage data and your configs stay yours.
Contributorsloading from GitHub…
Languagesestimated from snapshot
- Java 87.8%
- Shell 12.2%