Seitu Overview

Seitu Overview

Seitu is a type-safe reactive primitives library. Framework-agnostic core with React, Vue, Solid, and Svelte bindings. Every primitive shares the same get() / subscribe() API — no actions, no reducers, no context providers.

Module map

ESM-only. Node >= 22. React >= 19, Vue >= 3.5, Solid >= 1.9, and Svelte >= 5 are optional peer deps.

Mental model

All primitives implement a consistent interface:

subscribe accepts { immediate?: boolean } to fire the callback with the current value on subscribe.

Composition pattern

1. Create the primitive at module level (singleton).
2. Subscribe in a component via useSubscription (React/Vue).
3. Mutate directly from event handlers with .set() — no dispatch layer.

// stores/settings.ts
import { createWebStorage } from 'seitu/web'
import * as z from 'zod'

export const settings = createWebStorage({
  type: 'localStorage',
  schemas: { theme: z.enum(['light', 'dark']) },
  defaultValues: { theme: 'light' },
})

// components/Theme.tsx
'use client'
import { useSubscription } from 'seitu/react'
import { settings } from '../stores/settings'

export function Theme() {
  const { theme } = useSubscription(settings)
  return (
    <button => settings.set({ theme: theme === 'light' ? 'dark' : 'light' })}>
      {theme}
    </button>
  )
}

Decision tree

What do you need?
│
├─ In-memory state
│  ├─ Simple value → createStore
│  ├─ Schema-validated → createSchemaStore
│  └─ Derived from other sources → createComputed
│
├─ Browser persistence
│  ├─ Single key → createWebStorageValue
│  ├─ Multiple keys → createWebStorage
│  └─ Large/async data → createIndexedDbStorage
│
├─ DOM / browser APIs
│  ├─ CSS media query → createMediaQuery
│  ├─ Online/offline → createIsOnline
│  └─ Scroll position → createScrollState
│
├─ Rate limiting
│  ├─ On a subscribable → createDebounced / createThrottled
│  └─ On a function → createDebouncedFn / createThrottledFn
│
└─ Framework integration
   ├─ React → useSubscription (hook) or Subscription (component)
   ├─ Vue → useSubscription (composable)
   ├─ Solid → useSubscription (returns Accessor) or Subscription (component)
   └─ Svelte → useSubscription (returns a Readable store, read with $value)

Framework binding

One hook/composable works with any Seitu primitive — stores, web storage, computed, media queries, scroll state, etc.

const value = useSubscription(store)
const scroll = useSubscription(() => createScrollState({ element: el }), { deps: [el] })
const count = useSubscription(storage, { selector: v => v.count })

const value = useSubscription(store)
const data = useSubscription(computed(() => createWebStorageValue({ ... })))

// Solid — instance or reactive getter; returns an Accessor, read with value()
const value = useSubscription(store)
const data = useSubscription(() => createWebStorageValue({ ... }))

<!-- Svelte — instance or factory; returns a Readable store, read with $value -->
<script lang="ts">
  const value = useSubscription(store)
  const data = useSubscription(() => createWebStorageValue({ ... }))
</script>
<div>{$value}</div>

SSR

All seitu/web primitives return defaults when window / navigator is undefined. Safe to create at module level in SSR frameworks (Next.js, Nuxt). Use defaultMatches on createMediaQuery for SSR-specific defaults.

Validation & repair

Storage primitives accept Standard Schema validators (Zod, Valibot, ArkType). On invalid stored data, they fall back to defaultValue. Use onValidationError to intercept and repair:

import { repairValueObjectWithDefault } from 'seitu/utils'

const settings = createWebStorageValue({
  type: 'localStorage',
  key: 'settings',
  schema: z.object({ a: z.number(), b: z.string() }),
  defaultValue: { a: 0, b: 'default' },
  onValidationError: repairValueObjectWithDefault,
})

Per-function reference

The seitu skill has a reference file per primitive and framework binding in skills/seitu/references/<slug>.md (e.g. create-store.md). Read this overview first, then the specific reference for the function you need.

Common Mistakes

[HIGH] Using useState for shared module-level state

Wrong:

function Counter() {
  const [count, setCount] = useState(0)
}

Correct:

const count = createStore(0)
function Counter() {
  const value = useSubscription(count)
}

Seitu primitives are singletons at module scope; useState resets per component instance.

[MEDIUM] Importing seitu/react in non-React code

Wrong:

import { useSubscription } from 'seitu/react'
count.subscribe(console.log)

Correct:

import { createStore } from 'seitu'
const count = createStore(0)
count.subscribe(console.log)

React bindings are optional peer deps; core and web work without React.

[HIGH] Expecting actions or reducers

Wrong:

store.dispatch({ type: 'increment' })

Correct:

store.set(v => v + 1)

Seitu has no dispatch layer — mutate with .set() directly.

See also

• create-web-storage-value — Decision tree routes persistence tasks to web storage skills.

Source

src/core/index.ts