What is svelte5-best-practices?

A reference guide for writing, reviewing, and refactoring Svelte 5 and SvelteKit applications with TypeScript. Svelte is a tool for building web interfaces, while SvelteKit is its application framework.

Use it when working with Svelte 5 runes, snippets, component properties, event handlers, SvelteKit loading and form actions, or migrations from Svelte 4.

It helps avoid outdated Svelte patterns and gives developers one place to check current approaches for state, components, events, pages, forms, and performance.

svelte5-best-practices — Skill for Claude Code by ejirocodes

Install

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.

Any agent

npx skills add ejirocodes/agent-skills --skill svelte5-best-practices

Clone the repo

git clone --depth 1 https://github.com/ejirocodes/agent-skills

Made for: Claude Code.

Or install svelte5-best-practices, the plugin that ships this one along with the rest of its 1 skill.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/ejirocodes/agent-skills/svelte5-best-practices/github.svg)](https://agentmods.dev/skills/ejirocodes/agent-skills/svelte5-best-practices)

Your own site

<a href="https://agentmods.dev/skills/ejirocodes/agent-skills/svelte5-best-practices"><img src="https://agentmods.dev/badge/skills/ejirocodes/agent-skills/svelte5-best-practices/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/ejirocodes/agent-skills/svelte5-best-practices"><img src="https://agentmods.dev/badge/skills/ejirocodes/agent-skills/svelte5-best-practices.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 142 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 764 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

Socket pass 18 Mar 2026
Snyk pass 17 Feb 2026

How audits are shown

Origin original No closer match found in the catalogue.

Token cost

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	$0.00142	$0.00764
Opus 5	$0.00071	$0.00382
Sonnet 5	$0.00028	$0.00153
Haiku 4.5	$0.00014	$0.00076

Measured 10d ago against content hash eeb2be3e3208, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

svelte5-best-practices 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 10d 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.

svelte/skills/svelte5-best-practices/SKILL.md · 82 lines

How it starts

The opening of the file, as written. The whole thing — 82 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Svelte 5 Best Practices

Quick Reference

Topic	When to Use	Reference
Runes	$state, $derived, $effect, $props, $bindable, $inspect	runes.md
Snippets	Replacing slots, {#snippet}, {@render}	snippets.md
Events	onclick handlers, callback props, context API	events.md
TypeScript	Props typing, generic components	typescript.md
Migration	Svelte 4 to 5, stores to runes	migration.md
SvelteKit	Load functions, form actions, SSR, page typing	sveltekit.md
Performance	Universal reactivity, avoiding over-reactivity, streaming	performance.md

Essential Patterns

Reactive State

<script>
  let count = $state(0);           // Reactive state
  let doubled = $derived(count * 2); // Computed value
</script>

Component Props

<script>
  let { name, count = 0 } = $props();
  let { value = $bindable() } = $props(); // Two-way binding
</script>

Snippets (replacing slots)

<script>
  let { children, header } = $props();
</script>

{@render header?.()}
{@render children()}

Event Handlers

<!-- Svelte 5: use onclick, not on:click -->
<button onclick={() => count++}>Click</button>

Callback Props (replacing createEventDispatcher)

<script>
  let { onclick } = $props();
</script>

<button onclick={() => onclick?.({ data })}>Click</button>

Common Mistakes

Using let without $state - Variables are not reactive without $state()
Using $effect for derived values - Use $derived instead
Using on:click syntax - Use onclick in Svelte 5
Using createEventDispatcher - Use callback props instead
Using <slot> - Use snippets with {@render}
Forgetting $bindable() - Required for bind: to work
Setting module-level state in SSR - Causes cross-request leaks
Sequential awaits in load functions - Use Promise.all for parallel requests

Read the full file on GitHub · 82 lines

Files

What ships with it

7 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.

Changes

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.

10d ago First seen · 82 lines · 142 tokens per session scan A eeb2be3e3208

Subscribe to this mod's changes

svelte5-best-practices is a skill published in the GitHub repository ejirocodes/agent-skills (6 stars, last pushed 2mo ago), licensed MIT. It adds 142 tokens to every session and 764 once invoked, about $0.0007 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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