Durable Execution for AI Agents
Durable execution means an AI agent can lose its process — a crash, a deploy, a killed container — and pick up exactly where it left off, without redoing work or repeating side effects. It's the single property that separates an agent you can put in front of paying customers from a demo that only works when nothing goes wrong.
Checkpoint after every iteration
Full run state — messages, context, pending tool calls — is written to Postgres as an atomic upsert after each step.
Replays state, never effects
On resume, completed tool results are stitched back from the checkpoint. The agent never re-executes a tool it already ran.
Exactly-once side effects
Approved high-risk actions execute exactly once, enforced by a database compare-and-set — a retried worker can't double-charge.
Sibling-safety on suspend
When one of several batched tool calls needs approval, the non-gated siblings run first and persist; resume runs only the approved call.
SIGKILL, across two OS processes, against real Postgres, while a run is durably paused. It restarts, approves, and asserts the run resumes from the exact step — no replay. The same test passes on both a LangGraph graph and a hand-rolled vanilla loop.Durable execution is what makes human-in-the-loop approval safe — a pause that only works while the server stays up isn't really a pause. It works on every SDK; start with LangGraph or read the deep dive on durable human-in-the-loop.
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