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.
npx skills add fellipeutaka/leon --skill zustandgit clone --depth 1 https://github.com/fellipeutaka/leonWrote 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.
[](https://agentmods.dev/skills/fellipeutaka/leon/zustand)<a href="https://agentmods.dev/skills/fellipeutaka/leon/zustand"><img src="https://agentmods.dev/badge/skills/fellipeutaka/leon/zustand/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/fellipeutaka/leon/zustand"><img src="https://agentmods.dev/badge/skills/fellipeutaka/leon/zustand.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00075 | $0.00670 |
| Opus 5 | $0.00037 | $0.00335 |
| Sonnet 5 | $0.00015 | $0.00134 |
| Haiku 4.5 | $0.00007 | $0.00067 |
Grade A, and why
zustand 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 7d 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.
How it starts
The opening of the file, as written. The whole thing — 61 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Zustand
Lightweight state management for React. No providers, no boilerplate. Stores are hooks.
Quick start
import { create } from "zustand"
interface BearState {
bears: number
increase: (by: number) => void
}
const useBearStore = create<BearState>()((set) => ({
bears: 0,
increase: (by) => set((state) => ({ bears: state.bears + by })),
}))
// In components — select only what you need
const bears = useBearStore((state) => state.bears)
Critical rules
- TypeScript: Use curried form
create<T>()(...)— required for type inference - Immutability: Treat state as immutable.
setshallow-merges at one level only - Selectors: Always select specific fields, not the whole store. Use
useShallowfor multi-field selectors returning new references - Middleware order:
devtoolsmust be outermost:devtools(persist(immer(...))) - Next.js: Create stores per-request via
createStore+ Context, NOT globalcreate - Nested updates: Use Immer for deep nesting, spread operator for shallow
When to use what
| Need | Solution |
|---|---|
| Basic React store | create<T>()(...) |
| Vanilla (non-React) store | createStore from zustand/vanilla |
| Use vanilla store in React | useStore(store, selector) |
| Auto-infer types (no interface) | combine middleware |
| Persist to localStorage | persist middleware |
| Redux DevTools | devtools middleware |
| Mutable-style updates | immer middleware |
| Subscribe to slices externally | subscribeWithSelector middleware |
| Multiple fields without rerender | useShallow wrapper |
| Large store modularization | Slices pattern with StateCreator |
| Next.js App Router | createStore + Context + Provider |
| Reset store | set(initialState) or store.getInitialState() |
References
- API reference (create, createStore, hooks, shallow): See references/apis.md
- TypeScript patterns (curried create, slices, middleware typing, custom middleware): See references/typescript.md
- Middlewares (persist, devtools, immer, redux, combine, subscribeWithSelector): See references/middlewares.md
- Patterns & best practices (Next.js, testing, reset, auto-selectors, SSR, deep updates): See references/patterns.md
What ships with it
5 files 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.
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.
- 7d ago First seen · 61 lines · 75 tokens per session scan A 6297bc73d32c
zustand is a skill published in the GitHub repository fellipeutaka/leon (5 stars, last pushed 7d ago), licensed MIT. It adds 75 tokens to every session and 670 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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