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task-cancellation.md

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title Task Cancellation
sidebarTitle Cancellation
description Transactional cancellation request, execution fencing, and settlement.

{/* [LAYER: INFRASTRUCTURE] */}

Task cancellation

Cancellation is a two-step lifecycle transaction owned by TaskLifecycleFunnel.

  1. RequestCancellation commits a new lifecycle revision with cancellation requested.
  2. New ExecutionFunnel admission and permit validation fail closed for that generation.
  3. Task.abortTask() signals and joins task-owned in-flight resources.
  4. SettleCancellation commits terminal outcome cancelled.

The request is the execution fence; the settlement is the terminal result. A boolean cannot substitute for either fact. TaskState.abort is a read-only projection that is true while cancellation is requested or after terminal cancellation.

Duplicate UI cancellation calls are coalesced by Controller, but that promise is not lifecycle authority. It invokes the same task method and returns the funnel result.

Races

  • Cancellation before dispatch prevents permit-protected dispatch.
  • Cancellation during execution allows the admitted operation to settle but prohibits another dispatch.
  • Completion after the cancellation fence is rejected unless CompletionFunnel proves its durable fact predates the request.
  • Cancellation after terminal completion is rejected.
  • A stale-generation cancellation request is rejected.
  • Parent cancellation propagates typed requests and settlements to attached children; detached children are unaffected.

For the full state machine and conflict policy, see Task lifecycle authority.