The "${prefix}" env prefix is invalid in JS. Allowing all en

Error message

The "${prefix}" env prefix is invalid in JS. Allowing all env keys that are valid in JS (without any prefix).

What it means

When env.prefix is a single string, it must match /^[a-zA-Z_$][a-zA-Z0-9_$]*$/ because prefixed variables become import.meta.env.<PREFIX><KEY> identifiers in JS. An invalid prefix cannot produce valid JS keys, so with no defaultPrefix available the function warns and allows all JS-valid env keys without any prefix.

Source

Thrown at app-vite/lib/utils/env.js:58

  .reduce((acc, key) => {
    acc[key] = process.env[key]
    return acc
  }, {})

function getEnvFilesPrefix({ prefix, defaultPrefix, banner }) {
  if (!prefix) {
    if (!defaultPrefix) return ''
    warn(
      `No env prefix specified, using default "${defaultPrefix}" instead.`,
      banner
    )
    return defaultPrefix
  }

  if (!Array.isArray(prefix)) {
    if (!validEnvKeyRE.test(prefix)) {
      if (!defaultPrefix) {
        warn(
          `The "${prefix}" env prefix is invalid in JS. Allowing all env keys that are valid in JS (without any prefix).`,
          banner
        )
        return ''
      }

      warn(
        `Invalid env prefix specified, using default "${defaultPrefix}" instead.`,
        banner
      )
      return defaultPrefix
    }

    return prefix
  }

  const validPrefixList = []
  for (const entry of prefix) {

View on GitHub (pinned to 4841521b5f)

Solutions

Change the prefix to a valid JS identifier, e.g. 'MYAPP_' instead of 'MY-APP_'.
Rename related .env variable prefixes to match the corrected prefix.
If you truly want all valid env keys exposed, remove the prefix option instead of passing an invalid one.

Example fix

// before (quasar.config)
env: { prefix: 'MY-APP_' }
// after
env: { prefix: 'MYAPP_' }

Defensive patterns

Strategy: validation

Validate before calling

const validEnvKeyRE = /^[a-zA-Z_$][a-zA-Z0-9_$]*$/
const p = conf.env?.prefix
if (typeof p === 'string' && p && !validEnvKeyRE.test(p)) {
  throw new Error(`env.prefix "${p}" is not a valid JS identifier`)
}

Type guard

function isValidEnvPrefix(v) {
  return typeof v === 'string' && /^[a-zA-Z_$][a-zA-Z0-9_$]*$/.test(v)
}

Prevention

Use only [A-Za-z0-9_$] with a non-digit first character; prefer uppercase with trailing underscore.
Avoid hyphens/spaces in prefixes even if your .env keys use them.
Lint quasar.config with a quick regex check in CI.

When it happens

Trigger: quasar dev/build with quasar.config > env > prefix set to a string failing validEnvKeyRE (e.g. 'MY-APP_', '2APP_', contains spaces/hyphen/%%) and defaultPrefix being empty; called from the prefix/clientPrefix/backendPrefix getters.

Common situations: Using kebab-case names, copying OS env var names like 'ProgramFiles(x86)' style, or accidentally passing a number/boolean-ish value as prefix.

Related errors

AI-assisted analysis of quasarframework/quasar@4841521b5f (2026-08-30). Data as JSON: /api/errors/45a7e6f9b2bf3f94. Report an issue: GitHub.