Issue evidence · Launch · langchain-ai/langgraph

With the default durability="async", one failed checkpoint save permanently drops a state value

GitHub issue: https://github.com/langchain-ai/langgraph/issues/9245

Reproduced, workaround proven

After one failed checkpoint save, a state value written before the failure is gone from the thread for good.

What Badgr ran

Ran the issue's FlakySaver script on LangGraph 1.2.14, then again with durability="sync".

What came back

  • Default: the thread state was {'done': True}, with notes lost.
  • durability="sync": the thread state kept {'notes': {'x': 1}}.

Checked 2026-10-10 in Badgr’s local development environment.

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