pocketflow/docs/async.md

layout	title	parent	nav_order
default	Async	Core Abstraction	5

Async

Async pattern allows the post() step to be asynchronous (post_async()). This is especially helpful if you need to await something in post_async()—for example, user feedback or external async requests.

Warning: Only post() is async. prep() and exec() must be sync (often used for LLM calls).

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1. AsyncNode

Below is a minimal AsyncNode that calls an LLM in exec() (sync) and then awaits user feedback in post_async():

class SummarizeThenVerify(AsyncNode):
    def exec(self, shared, prep_res):
        doc = shared.get("doc", "")
        return call_llm(f"Summarize: {doc}")

    async def post_async(self, shared, prep_res, exec_res):
        user_decision = await gather_user_feedback(exec_res)
        if user_decision == "approve":
            shared["summary"] = exec_res
            return "approve"
        else:
            return "deny"

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2. AsyncFlow

We can build an AsyncFlow around this node. If the user denies, we loop back for another attempt; if approved, we pass to a final node:

summarize_node = SummarizeThenVerify()
final_node = Finalize()

# Chain conditions
summarize_node - "approve" >> final_node
summarize_node - "deny" >> summarize_node  # retry loop

flow = AsyncFlow(start=summarize_node)

async def main():
    shared = {"doc": "Mini LLM Flow is a lightweight LLM framework."}
    await flow.run_async(shared)
    print("Final stored summary:", shared.get("final_summary"))

asyncio.run(main())

• SummarizeThenVerify:
  • exec(): Summarizes text (sync LLM call).
  • post_async(): Waits for user approval.
• Finalize: Makes a final LLM call and prints the summary.
• If user denies, the flow loops back to SummarizeThenVerify.