Bun Sveltekit Skill for Claude

by secondsky

Use when building or running SvelteKit apps on Bun, including SSR, adapters, and Bun-specific APIs

2k tokens

context cost

the whole folder, loaded on every use

files

instructions only

copies elsewhere

how many repositories repackaged it

202

stars on the repo

on the repository, not the skill itself

Install

one command, takes just this skill from the repository

npx skills add https://github.com/secondsky/claude-skills --skill bun-sveltekit

The instruction itself

20 sections, as written by the author

Bun SvelteKit

Run SvelteKit applications with Bun for faster development and builds.

Quick Start

# Create new SvelteKit project
bunx sv create my-app
cd my-app

# Install dependencies
bun install

# Development
bun run dev

# Build
bun run build

# Preview
bun run preview

Secure Installation

Scaffolding tools like bunx sv create download and execute remote code. Before running, follow supply chain security best practices:

Block post-install scripts — Bun disables them by default; allow specific packages via trustedDependencies in package.json
Cooldown period — Configure minimumReleaseAge in bunfig.toml to wait 7 days for new versions
Audit before installing — Run socket package score npm <pkg> or use socket npm install <pkg> to check packages

Load the dependency-upgrade skill for full security configuration including Socket CLI integration, cooldown setup, lockfile validation, and CI enforcement.

Project Setup

package.json

{
  "scripts": {
    "dev": "vite dev",
    "build": "vite build",
    "preview": "vite preview"
  },
  "devDependencies": {
    "@sveltejs/adapter-auto": "^7.0.0",
    "@sveltejs/kit": "^2.0.0",
    "svelte": "^5.0.0",
    "vite": "^7.3.0"
  }
}

Use Bun Adapter

bun add -D svelte-adapter-bun

// svelte.config.js
import adapter from "svelte-adapter-bun";
import { vitePreprocess } from "@sveltejs/vite-plugin-svelte";

/** @type {import('@sveltejs/kit').Config} */
export default {
  preprocess: vitePreprocess(),
  kit: {
    adapter: adapter(),
  },
};

Using Bun APIs

Server Load Functions

// src/routes/users/+page.server.ts
import { Database } from "bun:sqlite";
import type { PageServerLoad } from "./$types";

export const load: PageServerLoad = async () => {
  const db = new Database("data.sqlite");
  const users = db.query("SELECT * FROM users").all();
  db.close();

  return { users };
};

Form Actions

// src/routes/users/+page.server.ts
import { Database } from "bun:sqlite";
import type { Actions } from "./$types";
import { fail } from "@sveltejs/kit";

export const actions: Actions = {
  create: async ({ request }) => {
    const data = await request.formData();
    const name = data.get("name") as string;

    if (!name) {
      return fail(400, { error: "Name required" });
    }

    const db = new Database("data.sqlite");
    db.run("INSERT INTO users (name) VALUES (?)", [name]);
    db.close();

    return { success: true };
  },

  delete: async ({ request }) => {
    const data = await request.formData();
    const id = data.get("id") as string;

    const db = new Database("data.sqlite");
    db.run("DELETE FROM users WHERE id = ?", [id]);
    db.close();

    return { success: true };
  },
};

API Routes

// src/routes/api/users/+server.ts
import { Database } from "bun:sqlite";
import { json } from "@sveltejs/kit";
import type { RequestHandler } from "./$types";

export const GET: RequestHandler = async () => {
  const db = new Database("data.sqlite");
  const users = db.query("SELECT * FROM users").all();
  db.close();

  return json(users);
};

export const POST: RequestHandler = async ({ request }) => {
  const { name } = await request.json();

  const db = new Database("data.sqlite");
  const result = db.run("INSERT INTO users (name) VALUES (?)", [name]);
  db.close();

  return json({ id: result.lastInsertRowid });
};

File Operations

// src/routes/api/files/[name]/+server.ts
import type { RequestHandler } from "./$types";

export const GET: RequestHandler = async ({ params }) => {
  const file = Bun.file(`./data/${params.name}`);

  if (!(await file.exists())) {
    return new Response("Not found", { status: 404 });
  }

  return new Response(file);
};

export const PUT: RequestHandler = async ({ params, request }) => {
  const content = await request.text();
  await Bun.write(`./data/${params.name}`, content);

  return new Response("Saved");
};

Server Hooks

// src/hooks.server.ts
import type { Handle } from "@sveltejs/kit";
import { Database } from "bun:sqlite";

// Initialize database on startup
const db = new Database("data.sqlite");
db.run(`
  CREATE TABLE IF NOT EXISTS users (
    id INTEGER PRIMARY KEY,
    name TEXT NOT NULL
  )
`);

export const handle: Handle = async ({ event, resolve }) => {
  // Add database to locals
  event.locals.db = db;

  // Auth check
  const session = event.cookies.get("session");
  if (session) {
    event.locals.user = await getUser(session);
  }

  return resolve(event);
};

// src/app.d.ts
import type { Database } from "bun:sqlite";

declare global {
  namespace App {
    interface Locals {
      db: Database;
      user?: { id: number; name: string };
    }
  }
}

Svelte 5 Components

<!-- src/routes/users/+page.svelte -->
<script lang="ts">
  import type { PageData } from "./$types";

  let { data }: { data: PageData } = $props();
  let { users } = $derived(data);

  let name = $state("");
</script>

<h1>Users</h1>

<form method="POST" action="?/create">
  <input type="text" name="name" bind:value={name} />
  <button type="submit">Add User</button>
</form>

<ul>
  {#each users as user}
    <li>
      {user.name}
      <form method="POST" action="?/delete" style="display: inline">
        <input type="hidden" name="id" value={user.id} />
        <button type="submit">Delete</button>
      </form>
    </li>
  {/each}
</ul>

Deployment

Build for Bun

bun run build
bun ./build/index.js

Docker

FROM oven/bun:1 AS builder

WORKDIR /app
COPY package.json bun.lockb ./
RUN bun install --frozen-lockfile

COPY . .
RUN bun run build

FROM oven/bun:1

WORKDIR /app
COPY --from=builder /app/build ./build
COPY --from=builder /app/package.json ./

EXPOSE 3000

CMD ["bun", "./build/index.js"]

Adapter Options

// svelte.config.js
import adapter from "svelte-adapter-bun";

export default {
  kit: {
    adapter: adapter({
      out: "build",
      precompress: true, // Generate .gz and .br files
      envPrefix: "",     // Environment variable prefix
      development: false,
      dynamic_origin: true,
      xff_depth: 1,
    }),
  },
};

Environment Variables

# .env
DATABASE_URL=./data.sqlite
PUBLIC_API_URL=https://api.example.com

// Access in server code
import { DATABASE_URL } from "$env/static/private";
import { PUBLIC_API_URL } from "$env/static/public";

// Or dynamic
import { env } from "$env/dynamic/private";
const dbUrl = env.DATABASE_URL;

Common Errors

| Error | Cause | Fix |

|-------|-------|-----|

| Cannot find bun:sqlite | Wrong adapter | Use svelte-adapter-bun |

| Vite error | Build issue | Clear .svelte-kit |

| Hydration failed | Server/client diff | Check load functions |

| 404 on refresh | SPA fallback | Configure adapter |

When to Load References

Load references/adapter-config.md when:

Advanced adapter options
Static prerendering
Edge deployment

Load references/performance.md when:

Caching strategies
Lazy loading
Streaming SSR

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How to use it

Copy the folder

Take secondsky/bun-sveltekit from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

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Install what it needs

The instructions reference npm. Without those the skill loads but fails at the first command.