pbakaus/impeccable · error · Error

SvelteKit live adapter requires a numeric port

Error message

SvelteKit live adapter requires a numeric port

What it means

Thrown by applySvelteKitLiveAdapter when the port argument cannot be coerced to a finite number. The adapter writes the live mount component with the port baked in, so a non-numeric port would produce a broken component; the guard fails fast before touching any files.

Source

Thrown at plugin/skills/impeccable/scripts/live/sveltekit-adapter.mjs:64

  if (!hasTemplateMarkers) return null;

  const hasSvelteConfig = fs.existsSync(path.join(cwd, 'svelte.config.js'))
    || fs.existsSync(path.join(cwd, 'svelte.config.mjs'))
    || fs.existsSync(path.join(cwd, 'svelte.config.cjs'))
    || fs.existsSync(path.join(cwd, 'svelte.config.ts'));
  const hasKitPackage = packageHasSvelteKit(cwd);
  if (!hasSvelteConfig && !hasKitPackage) return null;

  return {
    appHtml,
    layoutFile: findSvelteKitLayout(cwd),
    rootComponent: SVELTE_LIVE_ROOT_COMPONENT,
  };
}

export function applySvelteKitLiveAdapter({ cwd = process.cwd(), port, token, config = null } = {}) {
  if (!Number.isFinite(Number(port))) {
    throw new Error('SvelteKit live adapter requires a numeric port');
  }
  const detected = detectSvelteKitProject(cwd, config);
  if (!detected) return null;

  ensureSvelteLiveRootComponent(cwd, Number(port), token);

  const layoutRel = detected.layoutFile;
  const layoutAbs = path.join(cwd, layoutRel);
  fs.mkdirSync(path.dirname(layoutAbs), { recursive: true });
  const layoutExisted = fs.existsSync(layoutAbs);
  const before = layoutExisted ? fs.readFileSync(layoutAbs, 'utf-8') : defaultSvelteLayout();
  const after = patchSvelteLayout(before, { rev: svelteAdapterRev(token) });
  fs.writeFileSync(layoutAbs, after, 'utf-8');

  return {
    file: layoutRel,
    adapter: 'sveltekit',
    inserted: after !== before || !layoutExisted,

View on GitHub (pinned to d14711ae3d)

Solutions

1. Pass a numeric port: applySvelteKitLiveAdapter({ port: 4321 }).
2. Coerce from env: port: Number(process.env.IMPECCABLE_PORT) and validate it is finite before calling.
3. Ensure the boot flow assigns a concrete port before invoking the adapter.

Example fix

// before
applySvelteKitLiveAdapter({ cwd, port: undefined, token });

// after
const port = Number(process.env.IMPECCABLE_PORT ?? 4321);
if (!Number.isFinite(port)) throw new Error('port must be numeric');
applySvelteKitLiveAdapter({ cwd, port, token });

function isValidPort(port) {
  const n = Number(port);
  return Number.isFinite(n) && n > 0 && n < 65536;
}

function isNumericPort(port) {
  return Number.isFinite(Number(port));
}

try {
  applySvelteKitLiveAdapter({ cwd, port, token });
} catch (err) {
  if (err.message === 'SvelteKit live adapter requires a numeric port') {
    port = 4321; // default and retry
    applySvelteKitLiveAdapter({ cwd, port, token });
  } else throw err;
}

When it happens

Trigger: Calling applySvelteKitLiveAdapter({ port: undefined }), port: null, port: 'abc', or port: NaN. Number(port) is non-finite and the throw fires before detectSvelteKitProject.

Common situations: The boot did not parse a --port flag, an env var (PORT) was unset and flowed through as undefined, or a string port was passed uncoerced.

Related errors

• TanStack Start live adapter requires a numeric port
• SvelteKit live adapter requires a numeric port
• --target requires a path value (use --target <path> or --tar
• Invalid svelte-component source file
• Svelte-component source file escapes project root

AI-assisted analysis of pbakaus/impeccable@d14711ae3d (2026-08-13). Data as JSON: /api/errors/1a6569b307d71148. Report an issue: GitHub.