API reference

ES Runtime is ESM-only; the embeddable library is deny-by-default (the esrun CLI grants all capabilities). Host functionality is exposed as ES modules under the runtime: scheme — never as ambient globals — and every operation is gated on an explicit capability.

The runtime: scheme

Built-in modules are imported with a runtime: specifier. They are served from a baked, in-binary registry before any injected loader runs, and never touch the filesystem. The security boundary is the op, not the module: importing always succeeds, but an operation throws unless its capability has been granted.

import { env, args } from "runtime:process";

Built-in modules