What causes "unknown workflow state sync result: %d" in temporalio/temporal?

unknown workflow state sync result: %d

Error message

unknown workflow state sync result: %d

What it means

verifyFirstWorkflowTaskScheduled handling in the history service reaches an unknown sentinel value for a workflow state sync result. The enum workflowresend.SyncWorkflowStateResult only defines Skipped and Applied; any other value means a new enum member was added without updating the switch in resendChildAndVerify. It is an internal invariant violation, not a user error.

Source

Thrown at service/history/api/verifyfirstworkflowtaskscheduled/api.go:267

		},
	)
	if err != nil {
		emitResult(wideevents.ParentChildOutcomeFailed, err, "sync_workflow_state")
		return err
	}
	switch result {
	case workflowresend.SyncWorkflowStateResultSourceNotFound:
		emitResult(
			wideevents.ParentChildOutcomeSourceNotFound,
			serviceerror.NewNotFound("child workflow not found on source cluster"),
			"sync_workflow_state",
		)
		return nil
	case workflowresend.SyncWorkflowStateResultSkipped:
		return errVerify
	case workflowresend.SyncWorkflowStateResultApplied:
	default:
		return fmt.Errorf("unknown workflow state sync result: %d", result)
	}

	_, _, _, err = verifyFirstWorkflowTaskScheduled(ctx, req, workflowConsistencyChecker)
	if err != nil {
		emitResult(wideevents.ParentChildOutcomeFailed, err, "verify_after_resend")
		return err
	}
	emitResult(wideevents.ParentChildOutcomeSucceeded, nil, "")
	return nil
}

func childResendEventDetails(initialError error) map[string]any {
	return map[string]any{
		"initial_error_type": util.ErrorType(initialError),
	}
}

func emitChildResendLifecycleEvent(

View on GitHub (pinned to bde624efd1)

Solutions

Update the switch in resendChildAndVerify (service/history/api/verifyfirstworkflowtaskscheduled/api.go) to handle every SyncWorkflowStateResult enum member
Check that the workflowresend package's enum and the consuming switch are from the same build; redeploy both services from a consistent version
Add a default-case test covering all enum values so new members fail compilation or tests, not runtime

Example fix

// before
case workflowresend.SyncWorkflowStateResultApplied:
default:
	return fmt.Errorf("unknown workflow state sync result: %d", result)
// after
case workflowresend.SyncWorkflowStateResultApplied:
case workflowresend.SyncWorkflowStateResultNewValue:
	// handle the new result
default:
	return fmt.Errorf("unknown workflow state sync result: %d", result)

Defensive patterns

Strategy: try-catch

Try / catch

result, err := resendChildAndVerify(ctx, req)
if err != nil {
	var unk *fmt.Errorf // unknown result sentinel
	if strings.Contains(err.Error(), "unknown workflow state sync result") {
		// treat as invariant violation: alert and fail the operation
	}
	return err
}

Prevention

Keep switch statements over enums exhaustive (use exhaustive linter)
Add tests enumerating all SyncWorkflowStateResult values
Deploy all services from the same build to avoid enum version skew

When it happens

Trigger: resendChildAndVerify receives a result value from a workflowresend sync-workflow-state call that is neither SyncWorkflowStateResultSkipped nor SyncWorkflowStateResultApplied — e.g. after a new result type is added to the enum but the switch statement is not extended.

Common situations: Version skew between binaries during a rolling deploy where one binary emits a new SyncWorkflowStateResult value; custom forks that extend the enum; accidental corruption of the result value in transit (very unlikely since it is an in-process return value).

Related errors

AI-assisted analysis of temporalio/temporal@bde624efd1 (2026-09-01). Data as JSON: /api/errors/e5b5d8ca668f030d. Report an issue: GitHub.