langgraph-human-in-the-loop

To pause a LangGraph workflow for human approval, trigger an interrupt at a decision point and resume execution with the human's input using Command(resume=...). This enables robust draft-and-approve flows by continuing the graph from the exact point of interruption.

The human-in-the-loop pattern in LangGraph is a mechanism to pause graph execution for human oversight. It is needed for interrupt-driven approvals, validation loops, and multi-branch routing, allowing a human to review, edit, or approve a model's proposed action before the graph continues.

To persist LangGraph state across multiple sessions during an interrupt, use checkpointer-based persistence and thread_id tracking. This ensures reliable recovery across subgraphs and parallel branches, maintaining state integrity until you resume execution with Command(resume=...).

To avoid duplicate side effects when resuming a LangGraph graph, implement idempotent side effects and use Command(resume=...) for safe resumption from the exact interruption point. This standardized pattern provides clear guidance on preventing duplicate actions during human-in-the-loop workflows.

Yes, LangGraph supports human-in-the-loop routing within subgraphs. The pattern applies to interrupt-driven approvals, validation loops, and multi-branch routing, with checkpointer persistence and thread_id tracking enabling reliable recovery across parallel branches and nested graph structures.