TaskContext

The TaskContext object is supplied as the second argument to task handlers when an execution begins.

export interface TaskContext {
  readonly signal: AbortSignal;
  readonly executionId: string;
  readonly attempt: number;
  readonly idempotencyKey: string;

  reportProgress(progress: TaskProgress): void;
  throwIfCancelled(): void;
}

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Properties & Methods

signal: AbortSignal

Standard web AbortSignal triggered when the execution is cancelled, superseded by a concurrency policy, timed out, or destroyed by component lifecycle. Pass this to fetch() or HttpClient request options.

executionId: string

Unique identifier for this specific execution attempt.

attempt: number

Execution counter (1 for initial run, 2+ for retries via task.retryLast()).

idempotencyKey: string

Deterministic key generated for this execution to support safe idempotency in API calls.

reportProgress(progress: TaskProgress): void

Emits progress payload ({ loaded?: number, total?: number, percentage?: number, statusText?: string }) to task.progress and execution.progress signals.

throwIfCancelled(): void

Helper method that throws a TaskCancelledError if signal.aborted is true. Useful inside long-running CPU loops or step-by-step logic.

---

Example Usage

const uploadTask = createTask(
  async (files: File[], context: TaskContext) => {
    for (let i = 0; i < files.length; i++) {
      // Check cancellation before processing each file
      context.throwIfCancelled();

      context.reportProgress({
        loaded: i,
        total: files.length,
        percentage: Math.round((i / files.length) * 100),
        statusText: `Uploading file ${i + 1} of ${files.length}`,
      });

      await uploadFile(files[i], { signal: context.signal });
    }
  }
);