Transitions.dev is a CSS motion library agents can edit in place
Transitions.dev, by a developer publishing as Jakubantalik, ships 43 CSS motion transitions as a free CLI, a hosted showcase and an agent skill that lets Claude Code, Codex and Cursor pull a transition into a project or refine the ones already there. The repository has 4,702 stars on GitHub and ranked 11th on Trendshift's daily list on 10 October.
Image: GitHub
Why it mattersA product designer who asks a coding agent for an animation gets back a cubic-bezier curve the agent invented on the spot, and a named library that the agent can read and refine means the motion on a page is consistent across routes without a designer rebuilding it by hand.
A product team asking a coding agent for a smooth card-resize animation ends up with a cubic-bezier curve the agent wrote once, which is a different cubic-bezier curve the next time the same question is asked. Transitions.dev, by a developer publishing as Jakubantalik, is a library of 43 CSS transitions with a CLI, a live showcase and an agent skill that lets Claude Code, Codex and Cursor pull a transition in or edit the ones already there. The repository has 4,702 stars on GitHub, 196 forks and 511 commits, and ranked 11th on Trendshift's daily list on 10 October.
The library is CSS, not JavaScript. The README states that a transition is a self-contained snippet of semantic CSS custom properties on :root, transition rules under t-* class names, and a @media (prefers-reduced-motion: reduce) guard. Dropping one into a project is one npx transitions-dev add card-resize on the command line, with no account and no API key, or the agent skill route for a coding agent to do it in place.
What the agent skill does
The agent skill installs with npx skills add Jakubantalik/transitions.dev and tells the coding agent what the library is and how to pick a transition for a UI pattern. Supported hosts are listed as Cursor, Claude Code, Codex and other AI coding tools that read Agent Skills.
A second command, npx transitions-refine live, is a tool the README calls Refine. It injects a timeline and a panel into a running page. A reader clicks Refine on a transition that is already in the page, and the coding agent aligns the selected CSS motion to the library's tokens or replaces it with a library transition. The round trip is in-browser rather than copy and paste. The live showcase at transitions.dev shows every transition with a copy-ready CSS snippet, and the README's main table details 18 of the 43 named transitions.
Where the terms sit
The licence is split. The CLI, the agent skill and Refine are MIT. The library itself ships under a custom licence that stops redistribution as a competing library, which is a decision a reader should see before adopting it. Reusing a transition inside a product is fine, repackaging the set and shipping it as a rival library is not.
A design system usually has consistent motion only when a designer wrote the rules down and a front-end team kept to them. A coding agent asked for an animation on a Tuesday will not match the one it wrote on a Thursday, because nothing in its session memory refers back. A named library the agent can install and later align to is a different trade: the first motion the agent writes is from the library, and a Refine pass pulls earlier motion into line with the rest.
Source
This item was written by an AI system from the linked source. Reveneau is responsible for what it publishes.
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