fixing-motion-performance

fixing-motion-performance is a skill for Claude Code, Codex from fellipeutaka/leon. It costs 45 tokens per session (1,184 once invoked), scanned A, a copy of fixing-motion-performance, MIT.

A set of rules for finding and fixing slow or jerky web animations. It covers how browser layout, drawing, and compositing affect animation performance.

In plain words
What is it for?
Use it when adding, changing, or reviewing CSS or JavaScript animations, transitions, scrolling effects, or animated layout and visual effects.
Why use it?
It helps identify animation code that causes unnecessary page recalculation, drawing work, blur cost, or scroll-related stuttering.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/fellipeutaka/leon/fixing-motion-performance
Any agent
npx skills add fellipeutaka/leon --skill fixing-motion-performance
Clone the repo
git clone --depth 1 https://github.com/fellipeutaka/leon

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for fixing-motion-performance

README.md
[![agentmods](https://agentmods.dev/badge/skills/fellipeutaka/leon/fixing-motion-performance.svg)](https://agentmods.dev/skills/fellipeutaka/leon/fixing-motion-performance)
Your own site
<a href="https://agentmods.dev/skills/fellipeutaka/leon/fixing-motion-performance"><img src="https://agentmods.dev/badge/skills/fellipeutaka/leon/fixing-motion-performance.svg" alt="Measured on agentmods" height="20"></a>
Per session 45 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,184 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00045 $0.01184
Opus 5 $0.00023 $0.00592
Sonnet 5 $0.00009 $0.00237
Haiku 4.5 $0.00005 $0.00118

Measured 4d ago against content hash 0a2d654902bc, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fixing-motion-performance scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

100% identical to fixing-motion-performance — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/fixing-motion-performance/SKILL.md · 152 lines

How it starts

The opening of the file, as written. The whole thing — 152 lines — stays where its author put it; the contents beside it link to each section on GitHub.

fixing-motion-performance

Fix animation performance issues.

how to use

  • /fixing-motion-performance Apply these constraints to any UI animation work in this conversation.

  • /fixing-motion-performance <file> Review the file against all rules below and report:

    • violations (quote the exact line or snippet)
    • why it matters (one short sentence)
    • a concrete fix (code-level suggestion)

Do not migrate animation libraries unless explicitly requested. Apply rules within the existing stack.

when to apply

Reference these guidelines when:

  • adding or changing UI animations (CSS, WAAPI, Motion, rAF, GSAP)
  • refactoring janky interactions or transitions
  • implementing scroll-linked motion or reveal-on-scroll
  • animating layout, filters, masks, gradients, or CSS variables
  • reviewing components that use will-change, transforms, or measurement

rendering steps glossary

  • composite: transform, opacity
  • paint: color, borders, gradients, masks, images, filters
  • layout: size, position, flow, grid, flex

rule categories by priority

priority category impact
1 never patterns critical
2 choose the mechanism critical
3 measurement high
4 scroll high
5 paint medium-high
6 layers medium
7 blur and filters medium
8 view transitions low
9 tool boundaries critical

quick reference

1. never patterns (critical)

  • do not interleave layout reads and writes in the same frame
  • do not animate layout continuously on large or meaningful surfaces
  • do not drive animation from scrollTop, scrollY, or scroll events
  • no requestAnimationFrame loops without a stop condition
  • do not mix multiple animation systems that each measure or mutate layout

2. choose the mechanism (critical)

  • default to transform and opacity for motion
  • use JS-driven animation only when interaction requires it
  • paint or layout animation is acceptable only on small, isolated surfaces
  • one-shot effects are acceptable more often than continuous motion
  • prefer downgrading technique over removing motion entirely

Read the full file on GitHub · 152 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 4d ago First seen · 152 lines · 45 tokens per session scan A 0a2d654902bc

Subscribe to this mod's changes

fixing-motion-performance is a skill published in the GitHub repository fellipeutaka/leon (5 stars, last pushed yesterday), licensed MIT. It adds 45 tokens to every session and 1,184 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to fixing-motion-performance, differing in 0 lines, and is treated as a copy.

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