What changed
LangChain released a streamlined 1.0 agent API with middleware and standard content blocks, while LangGraph 1.0 stabilized its lower-level durable runtime for long-running, stateful and human-reviewed agent workflows.
Why it matters
Two widely used agent layers gained a major-version stability commitment and clearer separation between quick agent construction and explicit workflow control.
What to do
Use LangChain for a bounded tool loop and LangGraph where runs must pause, resume or branch. Add human approval middleware before any consequential tool.
Caveat
A stable API does not make agents reliable. Migration moves legacy functionality, provider semantics still differ, and durable execution requires application-specific state and idempotency design.