Claim 12 — LangGraph dossier

CLAIM 12 / LangGraph

Fault tolerance: "If one or more nodes fail at a given superstep, you can restart your graph from the last successful step," with pending checkpoint writes from successfully completed nodes preserved so they are not re-run

partial

Observed

The superstep recovery mechanism works as documented, with two qualifications re-verified 2026-06-11: restored state whose deserialization fails is silently replaced with None rather than erroring, so a "successful" restart can resume on corrupted state (#6970); and the sync execution path caches ERROR/INTERRUPT writes that the async path skips (#7015), so the same failure yields different checkpoint contents depending on execution mode — a graph that recovers correctly in async mode may replay stale error state in sync mode.

UPDATE 2026-06-28: a new race condition in PregelLoop.put_writes() (#8115, 2026-06-17) causes silent checkpoint data loss under concurrent Send tasks; its fix PR #8114 was closed without merge the same day.

Evidence

[1][2][3][4]