temporalio/temporal · error · UnprocessableTaskError

cannot deserialize task %v

Error message

cannot deserialize task %v

What it means

Error "cannot deserialize task %v" thrown in temporalio/temporal.

Source

Thrown at service/history/timer_queue_task_executor_base.go:229

	// meaning start version check will always pass.
	// Also, there's no way we can perform version check before first run may already be deleted due to retention
}

func (t *timerQueueTaskExecutorBase) executeSingleStateMachineTimer(
	ctx context.Context,
	workflowContext historyi.WorkflowContext,
	ms historyi.MutableState,
	deadline time.Time,
	timer *persistencespb.StateMachineTaskInfo,
	execute func(node *hsm.Node, task hsm.Task) error,
) error {
	def, ok := t.shardContext.StateMachineRegistry().TaskSerializer(timer.Type)
	if !ok {
		return queueserrors.NewUnprocessableTaskError(fmt.Sprintf("deserializer not registered for task type %v", timer.Type))
	}
	smt, err := def.Deserialize(timer.Data, hsm.TaskAttributes{Deadline: deadline})
	if err != nil {
		return fmt.Errorf(
			"%w: %w",
			queueserrors.NewUnprocessableTaskError(fmt.Sprintf("cannot deserialize task %v", timer.Type)),
			err,
		)
	}
	ref := hsm.Ref{
		WorkflowKey:     ms.GetWorkflowKey(),
		StateMachineRef: timer.Ref,
		Validate:        smt.Validate,
	}
	// TODO(bergundy): Duplicated this logic from the Access method. We specify write access here because
	// validateNotZombieWorkflow only blocks write access to zombie workflows.
	if err := t.validateNotZombieWorkflow(ms, hsm.AccessWrite); err != nil {
		return err
	}
	if err := t.validateStateMachineRef(ctx, workflowContext, ms, ref, false); err != nil {
		return err
	}

View on GitHub (pinned to bde624efd1)

When it happens

Trigger: Thrown at service/history/timer_queue_task_executor_base.go:229 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of temporalio/temporal@bde624efd1 (2026-09-01). Data as JSON: /api/errors/1d334a38e7a7010a. Report an issue: GitHub.