Configuration: Environment

Application code reads two exported constants from @shadow-js/core:

Export	Meaning
`isDev`	`true` in development builds. In production builds the dev-only code (warnings, full error text) is compiled away and this is `false`.
`isServer`	`true` in the server build, where effects never run and rendering produces strings.

src/environment.tsts

import { isDev, isServer } from "@shadow-js/core";

console.log(`isDev=${isDev} isServer=${isServer}`);

Expected output

isDev=true isServer=false

The same module compiled and run as the server does:

src/environment-server.tsts

import { isDev, isServer } from "@shadow-js/core";

console.log(`isDev=${isDev} isServer=${isServer}`);

Expected output

isDev=true isServer=true

Behind them are four constants the ShadowJS packages are built with: __DEV__, __SERVER__, __TEST__ and __VERSION__ (declared in types/build-constants.d.ts). The bundler replaces them when the packages are built, so they do not exist in your app and you cannot rely on them; use isDev and isServer. Each package ships several builds, and the export conditions pick one:

Condition (in order checked)	Build	`__DEV__`	`__SERVER__`
`browser` + `development`	`dist/dev`	true	false
`browser` + otherwise	`dist/prod` (minified)	false	false
`node`, `worker`, `deno` or `bun` + `development`	`dist/server-dev`	true	true
`node`, `worker`, `deno` or `bun` + otherwise	`dist/server` (minified)	false	true
none of the above, `development`	`dist/dev`	true	false
none of the above	`dist/prod`	false	false

This table is the exports map of @shadow-js/core; @shadow-js/web has the dev and prod builds for its main entry and the server builds for @shadow-js/web/server. Vite adds the development condition outside production builds, so vite dev and Vitest get development builds and vite build gets production builds. In development builds warnings are logged and errors carry their full text; in production builds an error keeps its code and name (SHADOW_...) and warnings are removed.