Coding Agent Skips VMs and Sandboxes With a TypeScript Linux Engine

RapidNative's coding agent generates full-stack React Native apps without spinning up a VM or cloud sandbox anywhere in the request path. Instead of Firecracker-based providers like Vercel Sandbox, E2B, or Daytona, the system runs entirely inside a Vercel Function, using Lifo, an open-source, MIT-licensed OS engine written in TypeScript that reimplements a Linux-like shell, filesystem, and 60+ commands in userland.

The core insight: agent tool calls are overwhelmingly filesystem operations (cat, grep, sed, find) and shell pipelines, not arbitrary native binaries. Lifo's virtual filesystem, bash-like interpreter, and WASM package manager cover this surface without hypervisor-level isolation. Benchmarks show a cold start of roughly 27ms and a ~305KB gzipped footprint, versus ~6.6 seconds and 75-85MB for WebContainers, with the same code running identically in Node and in the browser.

The architecture pairs Lifo's ephemeral virtual filesystem with Supabase Postgres as durable storage, hydrating and committing per turn for atomic, crash-safe writes. Database state is similarly modeled with pg-mem, an in-memory Postgres engine rebuilt per session, with SQL migrations as the single source of truth, validated before they land, and TypeScript types regenerated from the live schema. RLS policies with no rules are treated as build errors, not warnings.

For engineers building AI coding agents, this is a concrete alternative to the sandbox-by-default pattern: treat the OS and database as data structures living inside the request rather than infrastructure to provision, at the cost of not running native Linux binaries.