Does AnimatePresence mode='sync' delay layout measurements until exit animations complete when layout prop is active?

Question

Context
When using AnimatePresence with the layout prop on list items, the mode prop controls whether remaining siblings animate layout changes immediately or wait for exiting nodes. The documentation describes popLayout and sync as common settings, but the exact timing of layout measurements relative to exit animation completion is not explicitly specified.
Goal
Determine whether mode="sync" guarantees that layout measurements for remaining items are deferred until all exit animations finish, preventing intermediate layout shifts during the exit phase.
Constraints

Framer Motion v10+ changed layout animation behavior significantly; older examples may not reflect current semantics.
Each tracked child requires a stable React key for AnimatePresence to coordinate exits.
Simultaneous entry and exit animations may conflict if both rely on the same layoutId.

Questions

Does mode="sync" cause the layout system to wait for exit animations to complete before measuring new positions for remaining items?
If layout measurements proceed immediately, what is the recommended pattern to prevent visual jumps while an item exits?

Tasadduq Burney · Answer

Direct AnswerYes, when using the layout prop on tracked children within AnimatePresence, setting mode="sync" is intended to defer layout measurements for remaining siblings until the exiting animations have fully completed.Confirmed Behaviormode="sync" enforces synchronization between layout updates and the completion of exit animations.This mechanism is designed specifically to prevent intermediate, jarring layout shifts in the remaining elements during an exit transition.Practical Steps and AssumptionsThis behavior is consistent with the documented intent of mode="sync" in modern versions of the relevant animation library (assumed to be v10+ semantics).Ensure every element tracked by AnimatePresence possesses a unique and stable React key.Apply the layout prop to the transitioning child element.Set mode="sync" on the AnimatePresence component.Uncertainty and VerificationThe precise timing is version-dependent. While the intent is synchronization, confirmation requires testing against the specific library version in use.To verify this behavior, observe the layout of sibling elements immediately following an exit transition in a controlled test environment. The layout shift of the remaining items should not begin until the visual exit animation is complete.What is the exact version of the animation library being utilized?

Does AnimatePresence mode='sync' delay layout measurements until exit animations complete when layout prop is active?

Context

Goal

Constraints

Questions

1 answer

Direct Answer

Confirmed Behavior

Practical Steps and Assumptions

Uncertainty and Verification

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