vitest-dev/vitest · error · Error

Unexpected numerical input for "memoryLimit"

Error message

Unexpected numerical input for "memoryLimit"

What it means

stringToBytes converts a memory limit (a string like '1GB', '50%', or a raw number) into bytes. After parsing, a numeric value must be either a fraction in (0, 1] (read as a percentage of a reference) or a whole number of bytes greater than 1. Any other numeric result has no valid meaning, so the function throws this error instead of returning a broken limit. Note the value 1 exactly is treated as 100%, not 1 byte.

Solutions

1. Set the limit to a positive fraction (0,1] for a percentage, e.g. 0.5 or '50%', or a value greater than 1 for bytes, e.g. '1GB' or 1073741824.
2. Omit the option entirely to fall back to the default from getWorkerMemoryLimit (1 / maxWorkers of system memory).
3. If the value is computed dynamically, clamp it before assignment: Math.max(input, aSmallPositive) or treat values <= 0 as undefined.

Example fix

// before
test: { poolOptions: { threads: { memoryLimit: '0' } } }

// after
test: { poolOptions: { threads: { memoryLimit: '1GB' } } }

function isValidMemoryLimit(input) {
  if (input == null) return true // defers to the default
  const n = typeof input === 'number' ? input : Number.parseFloat(String(input))
  return !Number.isNaN(n) && n > 0
}
// usage:
if (!isValidMemoryLimit(config.memoryLimit)) throw new Error('memoryLimit must be positive')

function isPositiveMemoryLimit(v: unknown): v is number | string {
  if (v == null || (typeof v !== 'number' && typeof v !== 'string')) return false
  const n = typeof v === 'number' ? v : Number.parseFloat(v)
  return !Number.isNaN(n) && n > 0
}

When it happens

Trigger: Calling stringToBytes with a value that parses to a non-positive number: 0, '0', -1, '-512mb', '-50%', or anything Number.parseFloat reduces to NaN/negative. The else branch at memory-limit.ts:99-101 is reached only when the numeric input is not > 0 (after the percentage branch (0,1] and the bytes branch >1 are excluded).

Common situations: Setting poolOptions.threads.memoryLimit or vmMemoryLimit to '0' meaning 'no limit'; a typo like '-2048mb'; env-var-driven config that resolves to an empty or negative value; arithmetic that underflows to zero such as (totalMem - totalMem); negative percentage inputs.

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AI-assisted analysis of vitest-dev/vitest@1fa9837ec2 (2026-08-11). Data as JSON: /api/errors/d290d84258712e12. Report an issue: GitHub.

Appendix: source

Thrown at packages/vitest/src/utils/memory-limit.ts:100

    }
  }

  if (typeof input === 'number') {
    if (input <= 1 && input > 0) {
      if (percentageReference) {
        return Math.floor(input * percentageReference)
      }
      else {
        throw new Error(
          'For a percentage based memory limit a percentageReference must be supplied',
        )
      }
    }
    else if (input > 1) {
      return Math.floor(input)
    }
    else {
      throw new Error('Unexpected numerical input for "memoryLimit"')
    }
  }

  return null
}

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