The Human Is an Async API — Melanie Warrick, Temporal
This talk addresses the challenge of building durable, stateful AI agents that must interact with humans, who are inherently asynchronous and non-deterministic. The speaker demonstrates how Temporal's primitives—specifically Wait Conditions and Signals—allow multi-agent systems (like those built with Google ADK and LangGraph) to pause, wait for human input (which can take minutes or weeks), and resume execution without losing state or failing, even if the underlying worker service is temporarily killed and restarted.
Key takeaways
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Human Interaction as an Async API
5:38
Because humans are not tools, treating human input as a synchronous function call (a blocking call) will cause the entire system to fail or lose state. The solution is to treat the human as an asynchronous API.
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Durability Belongs in the Harness
7:38
For complex multi-agent systems, durability must be managed by the agent harness (e.g., Temporal) to ensure the system remains operational and stateful, regardless of external failures or long waits.
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Core Primitives for State Management
10:27
Temporal provides three main primitives: the Worker (runs the code), the Workflow (tracks the steps/logic), and the Activity (handles external interactions, like model or tool calls). This structure ensures state is tracked deterministically.
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Non-Blocking Human-in-the-Loop
13:22
To handle human input, use a combination of a Wait Condition (to pause the workflow and store the state) and a Signal (to inject the human's response back into the running workflow) without blocking the entire system.