Vite

Do not add the localslip npm package just to read a port. That package pulls better-sqlite3. Use the CLI (already on PATH if you claimed the slip):

import { execSync } from 'node:child_process';
import { defineConfig } from 'vite';

function localslipPort(name: string, fallback: number): number {
	try {
		const out = execSync(`localslip get ${name}`, { encoding: 'utf8', timeout: 5000, windowsHide: true });
		const port = Number(out.trim());
		return Number.isInteger(port) && port > 0 ? port : fallback;
	} catch {
		return fallback;
	}
}

export default defineConfig({
	server: { host: '127.0.0.1', port: localslipPort('foo', 5173), strictPort: true }
});

execSync runs through the shell, so the Windows localslip.cmd shim resolves without passing shell: true alongside an argument list (Node 24 warns about that). The fallback applies only when get fails: LocalSlip is not on PATH, or there is no claim. The missing-claim message still prints to the terminal.

Pin host to 127.0.0.1. Vite’s default localhost is often [::1] on Windows while the claim is IPv4.

import { localslipListen } from 'localslip/port' is only for the LocalSlip app itself. It opens the lease database.

strictPort: true is required for the stable mapping. Without it Vite can pick another port and ignore the claim.

If the claimed port is busy, Vite exits. LocalSlip does not move the lease. Use localslip ls and localslip scan to see the claim versus the listener.

For a phone tile, start Vite with --host (or server.host: true) so the process listens past loopback. A loopback claim does not stop you from doing that. --lan is what records the intended bind and firewall rule.