diff --git a/internal/workflow/workflow.go b/internal/workflow/workflow.go
index ff50cd7..f097fc5 100644
--- a/internal/workflow/workflow.go
+++ b/internal/workflow/workflow.go
@@ -378,7 +378,7 @@
 	return w, nil
 }
 
-// Run runs a workflow to successful completion and returns its outputs.
+// Run runs a workflow to completion or quiescence and returns its outputs.
 // listener.TaskStateChanged will be called when each task starts and
 // finishes. It should be used only for monitoring and persistence purposes -
 // to read task results, register Outputs.
@@ -420,6 +420,17 @@
 			}(*task)
 		}
 
+		// Exit if we've run everything we can given errors.
+		running := 0
+		for _, task := range w.tasks {
+			if task.started && !task.finished {
+				running++
+			}
+		}
+		if running == 0 {
+			return nil, fmt.Errorf("workflow has progressed as far as it can")
+		}
+
 		select {
 		case <-ctx.Done():
 			return nil, ctx.Err()