WASM runtime backend

A WebContainers-style backend: Node compiled to WASM running in-process/in-browser, so pnpm install and JS toolchains run with zero host setup, fully cross-platform.

Why deferred: It does not meet the generic-any-repo goal: WASM Node runs no native binaries (sharp, esbuild native, anything with a node-gyp addon) and is meaningfully CPU-slower. The os backend is the path to real native support and is the priority; a third backend splits effort.

Revisit when: The vfs and os backends are stable and there is concrete demand for a browser-only or zero-host-setup target (in-browser playground, untrusted client-side execution) where the no-native limitation is acceptable.

Cheaper interim: The vfs backend already covers in-process pure-JS runs cross-platform without WASM. For browser specifically, @webcontainer/api can be used directly rather than rebuilt.

Snapshot upper on tmpfs

Put the warm snapshot's overlay upper in RAM instead of the disk-backed global cache.

Whole-repo routing

Route every command through the sandbox by default — a transparent shim or single switch instead of per-command prefixes.