langchain-ai/langchainjs @langchain/core@1.3.1 on GitHub

#12026 178af31 Thanks @eliornl! - fix(core): deliver callbacks once to a handler registered twice by merged configs
Merging two runnable configs that both carry the same callback handler, as happens when an agent's streamEvents() runs inside a LangGraph node with tracing on, registered that handler twice, so it received every callback twice: every streamed chunk arrived twice. The configured callback manager now keeps each handler once, in order, including a handler passed as a plain object of methods that merged configs wrapped twice.
#12042 50343ba Thanks @sera-wi! - fix(core): include node metadata in Graph.toJSON() output when set, matching Python
#12048 304d190 Thanks @sera-wi! - fix(core): escape drawMermaid node metadata labels and leave out object values, so metadata with brackets or objects no longer breaks Mermaid parsing