Invalid env prefix specified, using default "${defaultPrefix

Error message

Invalid env prefix specified, using default "${defaultPrefix}" instead.

What it means

Same invalid-single-string-prefix case as the no-default variant, but here a defaultPrefix exists: the invalid configured prefix is discarded and the default (e.g. 'QCLI_') is used instead, after warning. The invalid prefix never takes effect.

Source

Thrown at app-vite/lib/utils/env.js:65

    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) {
    if (!entry) continue

    if (!validEnvKeyRE.test(entry)) {
      warn(
        `Invalid env prefix "${entry}" specified in the array. Skipping it.`,
        banner
      )

View on GitHub (pinned to 4841521b5f)

Solutions

Correct the prefix to a valid JS identifier in quasar.config > env.
If the default prefix is fine, delete the invalid prefix option and accept the (info-level) default warning.
Grep .env files and rename variables to the corrected or default prefix.

Example fix

// before (quasar.config)
env: { prefix: 'app-env_' }
// after
env: { prefix: 'APP_ENV_' }

Defensive patterns

Strategy: validation

Validate before calling

const validEnvKeyRE = /^[a-zA-Z_$][a-zA-Z0-9_$]*$/
const p = conf.env?.prefix
if (typeof p === 'string' && p && !validEnvKeyRE.test(p)) {
  console.warn(`env.prefix "${p}" invalid; falling back to default 'QCLI_'`)
}

Type guard

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

Prevention

Test the prefix against /^[a-zA-Z_$][a-zA-Z0-9_$]*$/ before committing config.
Remember the fallback default is 'QCLI_' for client builds; rename .env vars accordingly if you rely on defaults.

When it happens

Trigger: quasar dev/build with env.prefix (or clientPrefix/backendPrefix source) set to a string failing /^[a-zA-Z_$][a-zA-Z0-9_$]*$/ while the caller has a defaultPrefix; getEnvFilesPrefix falls back to it.

Common situations: Typos like 'q-cli_' vs 'QCLI_', hyphenated team prefixes, or forgetting prefixes must be valid JS identifier starts.

Related errors

AI-assisted analysis of quasarframework/quasar@4841521b5f (2026-08-30). Data as JSON: /api/errors/a13e31bbdb493495. Report an issue: GitHub.