Vivien's Jaguar — ruling 1

If a Vivien planeswalker and Vivien's Jaguar are both dealt lethal damage at the same time (most likely in combat), they'll be put into their owner's graveyard at the same time. You won't be able to activate the last ability of Vivien's Jaguar before Vivien leaves the battlefield.

Vivien's Jaguar : règles, fonctionnement et interactions (MTG)

Vivien's Jaguar is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Reach (This creature can block creatures with flying.) : Return this card from your graveyard to your hand. Activate only if you control a Vivien planeswalker.

How it works : Vivien's Jaguar

Original English text — Wizards of the Coast / Scryfall

#1July 13, 2018· Wizards of the Coast
If a Vivien planeswalker and Vivien's Jaguar are both dealt lethal damage at the same time (most likely in combat), they'll be put into their owner's graveyard at the same time. You won't be able to activate the last ability of Vivien's Jaguar before Vivien leaves the battlefield.
No other card is named in this ruling.