# Error reference

This page contains guides around resolving common errors you may find while building with LangChain.
Errors referenced below will have an `lc_error_code` property corresponding to one of the below codes when they are thrown in code.

- [GRAPH_RECURSION_LIMIT](/langgraphjs/troubleshooting/errors/GRAPH_RECURSION_LIMIT)
- [INVALID_CONCURRENT_GRAPH_UPDATE](/langgraphjs/troubleshooting/errors/INVALID_CONCURRENT_GRAPH_UPDATE)
- [INVALID_GRAPH_NODE_RETURN_VALUE](/langgraphjs/troubleshooting/errors/INVALID_GRAPH_NODE_RETURN_VALUE)
- [MULTIPLE_SUBGRAPHS](/langgraphjs/troubleshooting/errors/MULTIPLE_SUBGRAPHS)
- [UNREACHABLE_NODE](/langgraphjs/troubleshooting/errors/UNREACHABLE_NODE)
