Workflow SDK 5 beta adds native AbortController and AbortSignal support across workflow and step boundaries. Create a controller inside a workflow, pass its signal into steps, and cancel in-flight operations using the same API fetch already uses.
The signal survives suspensions and deterministic replay. A step running in a separate function invocation still sees the cancellation. Cancellation is cooperative: steps must inspect the signal or pass it to an API that supports AbortSignal. No silent kills.
The practical uses are concrete: stop a slow step when a durable timeout wins a race, cancel remaining requests after the first successful response, or halt parallel work when an external condition changes. Install workflow@beta and read the cancellation documentation to see how signal threading works across multi-step pipelines.
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