ios-animation-code-review

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Reviews iOS animation code for correctness, performance, accessibility, and Apple API best practices. Use when reviewing .swift files containing animation code — withAnimation, .animation(), PhaseAnimator, KeyframeAnimator, matchedGeometryEffect, navigationTransition, CABasicAnimation, CASpringAnimation, UIViewPropertyAnimator, UIDynamicAnimator, symbolEffect, scrollTransition, contentTransition, or custom Transition conformances.

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Sourceexistential-birds/beagle

Added on2026-04-15

NPX Install

npx skill4agent add existential-birds/beagle ios-animation-code-review

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iOS Animation Code Review

Quick Reference

Issue Type	Reference
Spring parameters, withAnimation misuse, phase/keyframe bugs	references/swiftui-animation-patterns.md
Frame drops, offscreen rendering, main thread blocking	references/performance.md
Reduce Motion, VoiceOver, motion sensitivity	references/accessibility.md
Transition protocol, matchedGeometryEffect, navigation transitions	references/transitions.md

Output Format

Report each finding as:

[FILE:LINE] ISSUE_TITLE

Example:

[AnimatedCard.swift:42] Missing Reduce Motion fallback for spring animation

All details, code suggestions, and rationale follow after the header line.

Review Checklist

```
@Environment(\.accessibilityReduceMotion)
```
checked — animations have Reduce Motion fallback
Animation is not the sole feedback channel — important state changes pair with haptics (
```
.sensoryFeedback
```
) or audio
Custom animation isn't duplicating system-provided motion (standard nav transitions, sheet presentation, SF Symbol effects)
Animations on frequent interactions are brief and unobtrusive — or absent (system handles it)
All animations are interruptible — user is never forced to wait for completion before interacting
Spring animations use
```
duration
```
/
```
bounce
```
parameters (not raw mass/stiffness/damping unless UIKit/CA)
No deprecated
```
.animation()
```
without
```
value:
```
parameter
```
withAnimation
```
wraps state changes, not view declarations
```
matchedGeometryEffect
```
IDs are stable and unique within the namespace
```
geometryGroup()
```
used when parent geometry animates with child views appearing
Looping animations (
```
PhaseAnimator
```
,
```
symbolEffect
```
) have finite phases or appropriate trigger
No
```
CATransaction.setAnimationDuration()
```
in UIView-backed layers (use UIView.animate instead)
Interactive animations handle interruption (re-trigger mid-flight doesn't break state)
Shadow animations provide explicit
```
shadowPath
```
(avoids per-frame recalculation)
Gesture-driven animations preserve velocity on release for natural completion
Gesture-driven feedback follows spatial expectations (dismiss direction matches reveal direction)
No animation of
```
.id()
```
modifier (destroys view identity — use
```
transition
```
or
```
matchedGeometryEffect
```
instead)

When to Load References

Incorrect spring setup or
```
withAnimation
```
scope issues → swiftui-animation-patterns.md
Hitches, dropped frames, or expensive animations in scroll views → performance.md
Missing Reduce Motion handling or motion accessibility → accessibility.md
```
matchedGeometryEffect
```
glitches or custom
```
Transition
```
bugs → transitions.md

Review Questions

Does every animation have a Reduce Motion fallback that preserves the information conveyed? Is animation the only feedback channel, or are haptics/audio supplementing it?
Is this custom animation necessary, or does the system already provide it (standard transitions, SF Symbol effects, Liquid Glass)?
Could this animation cause frame drops — is it animating expensive properties (blur, shadow without path, mask) in a list or scroll view?
Are all animations interruptible? Can the user act without waiting for completion? Does gesture-driven feedback follow spatial expectations?
Is
```
withAnimation
```
scoped to the minimal state change needed, or is it wrapping unrelated mutations?
For
```
matchedGeometryEffect
```
— are source and destination using the same ID and namespace, and is only one visible at a time?