Johann's Stopgap — ruling 1

The cost-reduction ability of Johann's Stopgap doesn't change its mana cost or mana value, only the total cost you pay. Specifically, the mana value of Johann's Stopgap is always 4.

Johann's Stopgap — ruling 2

If the permanent is an illegal target as Johann's Stopgap tries to resolve, Johann's Stopgap is removed from the stack and you won't draw a card.

Johann's Stopgap — ruling 3

Bargain means "As an additional cost to cast this spell, you may sacrifice an artifact, enchantment, or token."

Johann's Stopgap — ruling 4

Bargain represents an optional additional cost. A spell cast with that additional cost paid is "bargained."

Johann's Stopgap — ruling 5

You may sacrifice only one artifact, enchantment, or token to pay a spell's bargain cost.

Johann's Stopgap — ruling 6

If you copy a bargained spell, the copy is also bargained. If a card or token enters the battlefield as a copy of a permanent that's already on the battlefield, the new permanent isn't bargained, even if the original was.

Johann's Stopgap — ruling 7

Some instant and sorcery spells require additional targets if they're bargained. You ignore those targeting requirements if those spells aren't bargained, and you can't bargain those spells unless you can choose the appropriate targets. On the other hand, you can bargain a permanent spell even if you won't be able to choose targets for an enters-the-battlefield ability of that permanent once the spell resolves.

Johann's Stopgap : règles, fonctionnement et interactions (MTG)

Johann's Stopgap 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

Bargain (You may sacrifice an artifact, enchantment, or token as you cast this spell.) This spell costs less to cast if it's bargained. Return target nonland permanent to its owner's hand. Draw a card.

How it works : Johann's Stopgap

Original English text — Wizards of the Coast / Scryfall

#1September 1, 2023· Wizards of the Coast
The cost-reduction ability of Johann's Stopgap doesn't change its mana cost or mana value, only the total cost you pay. Specifically, the mana value of Johann's Stopgap is always 4.
No other card is named in this ruling.
#2September 1, 2023· Wizards of the Coast
If the permanent is an illegal target as Johann's Stopgap tries to resolve, Johann's Stopgap is removed from the stack and you won't draw a card.
No other card is named in this ruling.
#3September 1, 2023· Wizards of the Coast
Bargain means "As an additional cost to cast this spell, you may sacrifice an artifact, enchantment, or token."
No other card is named in this ruling.
#4September 1, 2023· Wizards of the Coast
Bargain represents an optional additional cost. A spell cast with that additional cost paid is "bargained."
No other card is named in this ruling.
#5September 1, 2023· Wizards of the Coast
You may sacrifice only one artifact, enchantment, or token to pay a spell's bargain cost.
No other card is named in this ruling.
#6September 1, 2023· Wizards of the Coast
If you copy a bargained spell, the copy is also bargained. If a card or token enters the battlefield as a copy of a permanent that's already on the battlefield, the new permanent isn't bargained, even if the original was.
No other card is named in this ruling.
#7September 1, 2023· Wizards of the Coast
Some instant and sorcery spells require additional targets if they're bargained. You ignore those targeting requirements if those spells aren't bargained, and you can't bargain those spells unless you can choose the appropriate targets. On the other hand, you can bargain a permanent spell even if you won't be able to choose targets for an enters-the-battlefield ability of that permanent once the spell resolves.
No other card is named in this ruling.