Does Swiftfoot Boots grant hexproof to the creature immediately when equipped or only after the ability resolves?

Swiftfoot Boots grants hexproof via a static ability (not a triggered or activated ability), meaning it generates a continuous effect that applies automatically the moment the Equipment becomes attached to a creature. There is no separate trigger or resolution step for the hexproof itself.

According to CR 604.1 and 604.2, static abilities are always 'on' and create continuous effects as long as the permanent with the ability is in the appropriate zone and meets any conditions. Because Swiftfoot Boots simply says 'Equipped creature has hexproof,' that effect is live the instant the equip action completes and the Equipment is attached.

The equip activated ability (CR 702.6a) does go on the stack and resolve — but that activation is what attaches the Equipment. Once attached (i.e., once the equip ability resolves), the static hexproof ability immediately applies with no further stack interaction needed.

Important nuance: your opponent can respond to the equip activation before it resolves, targeting the creature while it doesn't yet have hexproof. But the instant equip resolves and the boots attach, the creature gains hexproof on the spot — in the middle of that same round of priority.

Example: You activate equip on your Runeclaw Bear. Your opponent lets it resolve. The moment Swiftfoot Boots attaches, Runeclaw Bear has hexproof — your opponent cannot then cast Lightning Bolt targeting it, even though they had a chance to respond before the equip resolved.