No Use Effect

What it does

When your agent uses it

• Tasks that involve React components
• Tasks that involve Refactoring

Example prompts

• “just in case.”
• “/no-use-effect”

Workflow steps

3 steps, taken from the step headings in SKILL.md.

1. 1Identify the useEffect
2. 2Apply the Correct Replacement Pattern
3. 3Verify

What it can do on your machine

Read from SKILL.md and the folder at commit 984f521. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md (its code samples are typescript).

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • react.dev

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

No Use Effect loads about 1.7k tokens when it runs. Until then it costs about 78 tokens; SKILL.md has 431 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~78

When it runs · the whole SKILL.md, loaded when a task matches

~1.7k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from mattiacerutti/supernova at commit 984f521, republished under its MIT licence (© mattiacerutti). 431 words, ~1,731 tokens.

name

no-use-effect

description

Enforce the no-useEffect rule when writing or reviewing React code. ACTIVATE when writing React components, refactoring existing useEffect calls, reviewing PRs with useEffect, or when an agent adds useEffect "just in case." Provides the five replacement patterns and the useMountEffect escape hatch.

export function useMountEffect(effect: () => void | (() => void)) {
  /* eslint-disable no-restricted-syntax */
  useEffect(effect, []);
}

// BAD: Two render cycles - first stale, then filtered
function ProductList() {
  const [products, setProducts] = useState([]);
  const [filteredProducts, setFilteredProducts] = useState([]);

  useEffect(() => {
    setFilteredProducts(products.filter((p) => p.inStock));
  }, [products]);
}

// GOOD: Compute inline in one render
function ProductList() {
  const [products, setProducts] = useState([]);
  const filteredProducts = products.filter((p) => p.inStock);
}

// BAD: Race condition risk
function ProductPage({productId}) {
  const [product, setProduct] = useState(null);

  useEffect(() => {
    fetchProduct(productId).then(setProduct);
  }, [productId]);
}

// GOOD: Query library handles cancellation/caching/staleness
function ProductPage({productId}) {
  const {data: product} = useQuery(["product", productId], () => fetchProduct(productId));
}

// BAD: Effect as an action relay
function LikeButton() {
  const [liked, setLiked] = useState(false);

  useEffect(() => {
    if (liked) {
      postLike();
      setLiked(false);
    }
  }, [liked]);

  return <button onClick={() => setLiked(true)}>Like</button>;
}

// GOOD: Direct event-driven action
function LikeButton() {
  return <button onClick={() => postLike()}>Like</button>;
}

// BAD: Guard inside effect
function VideoPlayer({ isLoading }) {
  useEffect(() => {
    if (!isLoading) playVideo();
  }, [isLoading]);
}

// GOOD: Mount only when preconditions are met
function VideoPlayerWrapper({ isLoading }) {
  if (isLoading) return <LoadingScreen />;
  return <VideoPlayer />;
}

function VideoPlayer() {
  useMountEffect(() => playVideo());
}

// BAD: useEffect with dependency that never changes
useEffect(() => {
  connectionManager.on("connected", handleConnect);
  return () => connectionManager.off("connected", handleConnect);
}, [connectionManager]); // connectionManager is a singleton from context

// GOOD: useMountEffect for stable dependencies

useMountEffect(() => {
  connectionManager.on("connected", handleConnect);
  return () => connectionManager.off("connected", handleConnect);
});

// BAD: Effect attempts to emulate remount behavior
function VideoPlayer({ videoId }) {
  useEffect(() => {
    loadVideo(videoId);
  }, [videoId]);
}

// GOOD: key forces clean remount
function VideoPlayer({ videoId }) {
  useMountEffect(() => {
    loadVideo(videoId);
  });
}

function VideoPlayerWrapper({ videoId }) {
  return <VideoPlayer key={videoId} videoId={videoId} />;
}

export function FeatureComponent({ featureId }: ComponentProps) {
  // Hooks first
  const { data, isLoading } = useQueryFeature(featureId);

  // Local state
  const [isOpen, setIsOpen] = useState(false);

  // Computed values (NOT useEffect + setState)
  const displayName = user?.name ?? 'Unknown';

  // Event handlers
  const handleClick = () => { setIsOpen(true); };

  // Early returns
  if (isLoading) return <Loading />;

  // Render
  return <Flex direction="column" gap="lg">...</Flex>;
}

© mattiacerutti, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .agents/skills/no-use-effect of mattiacerutti/supernova.

Open the folder on GitHubat commit 984f521

Used in 2 other repositories

We found 2 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 2 other GitHub owners. This page covers the copy in mattiacerutti/supernova, which our catalogue first saw on October 7, 2026.

• trycompai/crm.agents/skills/no-use-effect
• Factory-AI/factory-pluginsplugins/typescript/skills/no-use-effect