Does the universe have one true order of events?

In this model there is no single privileged "now" or master timeline — any foliation that respects causality (never placing an effect before its cause) is treated as an equally valid reference frame. [setup] What every observer must agree on is the underlying web of cause and effect, the causal graph itself; that shared agreement is guaranteed only if the rule is causally invariant. [setup] So the partial order of cause-and-effect is objective, but the particular total ordering an observer reads off it is frame-dependent — a model-internal claim, not settled physics.