Snapcaster Mage doesn’t give a spell flashback until after its triggered ability resolves.

When your opponent casts a to give something flashback, you get a window of opportunity to do something before that spell can be flashed back. The targeted spell doesn’t immediately have flashback as soon as the Snapcaster hits the field. Once the Snapcaster resolves, its triggered ability goes on the stack and the controller chooses […]

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