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 agentmods add skills/fellipeutaka/leon/tanstack-formnpx skills add fellipeutaka/leon --skill tanstack-formgit clone --depth 1 https://github.com/fellipeutaka/leonWhat 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 | $0.00076 | $0.01705 |
| Opus 5 | $0.00038 | $0.00852 |
| Sonnet 5 | $0.00015 | $0.00341 |
| Haiku 4.5 | $0.00008 | $0.00170 |
Grade A, and why
tanstack-form 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 2d 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 — 191 lines — stays where its author put it; the contents beside it link to each section on GitHub.
TanStack Form
Version: @tanstack/react-form@latest Requires: React 18.0+, TypeScript 5.0+
Quick Setup
npm install @tanstack/react-form
import { useForm } from '@tanstack/react-form'
function App() {
const form = useForm({
defaultValues: {
firstName: '',
lastName: '',
},
onSubmit: async ({ value }) => {
console.log(value)
},
})
return (
<form
onSubmit={(e) => {
e.preventDefault()
e.stopPropagation()
form.handleSubmit()
}}
>
<form.Field
name="firstName"
validators={{
onChange: ({ value }) =>
!value ? 'Required' : value.length < 3 ? 'Too short' : undefined,
}}
children={(field) => (
<>
<input
value={field.state.value}
onBlur={field.handleBlur}
onChange={(e) => field.handleChange(e.target.value)}
/>
{!field.state.meta.isValid && (
<em>{field.state.meta.errors.join(', ')}</em>
)}
</>
)}
/>
<form.Subscribe
selector={(state) => [state.canSubmit, state.isSubmitting]}
children={([canSubmit, isSubmitting]) => (
<button type="submit" disabled={!canSubmit}>
{isSubmitting ? '...' : 'Submit'}
</button>
)}
/>
</form>
)
}
Production Setup (Recommended)
For production apps, use createFormHook to pre-bind reusable UI components and reduce boilerplate:
import { createFormHookContexts, createFormHook } from '@tanstack/react-form'
import { TextField, NumberField, SubmitButton } from '~/ui-library'
const { fieldContext, formContext } = createFormHookContexts()
export const { useAppForm } = createFormHook({
fieldComponents: { TextField, NumberField },
formComponents: { SubmitButton },
fieldContext,
formContext,
})
Devtools
npm install -D @tanstack/react-devtools @tanstack/react-form-devtools
What ships with it
12 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.
- agents/openai.yaml 186 B
- rules/arr-array-fields.md 3.4 KB
- rules/comp-form-composition.md 4.0 KB
- rules/field-state.md 2.5 KB
- rules/form-setup.md 2.6 KB
- rules/link-linked-fields.md 2.4 KB
- rules/listen-listeners.md 2.2 KB
- rules/ssr-meta-frameworks.md 4.5 KB
- rules/sub-submission.md 2.2 KB
- rules/ui-libraries.md 3.0 KB
- rules/val-schema-validation.md 2.5 KB
- rules/val-validation.md 3.8 KB
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.
- 2d ago First seen · 191 lines · 76 tokens per session scan A 6846c9cfa5e5
tanstack-form is a skill published in the GitHub repository fellipeutaka/leon (5 stars, last pushed 4d ago), licensed MIT. It adds 76 tokens to every session and 1,705 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 2026-08-31.
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