Differentiate LangGraph4j and LangChain4j: the toolkit talks to models, RAG, and tools; the graph owns topology, checkpoints, interrupt, and resume. They compose — they are not a bake-off.
LangChain4j
The toolkit: ChatModel, RAG, tools, memory, and AiServices.
LangGraph4j
The conductor: StateGraph, channels, checkpoints, interrupt, and resume.
LangChain4j is not
A durable workflow engine. Restart mid-run and graph topology stay yours.
LangGraph4j is not
A model or RAG kit. Nodes start empty until you put a toolkit inside.
Same job
Tiny samples: AiServices.create().chat() versus StateGraph plus interruptAfter("plan").
Decision
One call or RAG stays in LangChain4j. Pause, resume, and cycles belong in LangGraph4j.