nextauthjs/next-auth · error · TypeError

option priority is invalid: ${options.priority}

Error message

option priority is invalid: ${options.priority}

What it means

serialize() accepts `priority` only as one of the strings 'low', 'medium', or 'high' (case-insensitive; the value is lowercased before the switch). Any other truthy value — a misspelled priority, a number, or a non-string object — falls through to the default branch and throws a TypeError. Cookie Priority is a standardized attribute with a closed value set, so anything else is invalid.

Source

Thrown at packages/core/src/lib/vendored/cookie.ts:337

  }

  if (options.priority) {
    const priority =
      typeof options.priority === "string"
        ? options.priority.toLowerCase()
        : undefined
    switch (priority) {
      case "low":
        str += "; Priority=Low"
        break
      case "medium":
        str += "; Priority=Medium"
        break
      case "high":
        str += "; Priority=High"
        break
      default:
        throw new TypeError(`option priority is invalid: ${options.priority}`)
    }
  }

  if (options.sameSite) {
    const sameSite =
      typeof options.sameSite === "string"
        ? options.sameSite.toLowerCase()
        : options.sameSite
    switch (sameSite) {
      case true:
      case "strict":
        str += "; SameSite=Strict"
        break
      case "lax":
        str += "; SameSite=Lax"
        break
      case "none":
        str += "; SameSite=None"

View on GitHub (pinned to a1a16a5a77)

Solutions

1. Use exactly 'low', 'medium', or 'high' (any casing)
2. Add a TypeScript union type: priority?: 'low' | 'medium' | 'high' so invalid values fail at compile time
3. Normalize/validate user- or config-supplied priorities against the allowed set before calling serialize
4. If priority is optional in your logic, omit the field entirely for non-standard values rather than passing a guess

Example fix

// before
serialize('sid', val, { priority: 'critical' })
// after
serialize('sid', val, { priority: 'high' })

const PRIORITIES = new Set(['low', 'medium', 'high'])
function isValidPriority(v) {
  return typeof v === 'string' && PRIORITIES.has(v.toLowerCase())
}
if (opts.priority && !isValidPriority(opts.priority)) throw new TypeError(`option priority is invalid: ${opts.priority}`)

type CookiePriority = 'low' | 'medium' | 'high'
function isCookiePriority(v: unknown): v is CookiePriority {
  return typeof v === 'string' && ['low', 'medium', 'high'].includes(v.toLowerCase())
}

let cookie
try {
  cookie = serialize('sid', val, { priority })
} catch (err) {
  if (err instanceof TypeError && err.message.startsWith('option priority is invalid')) {
    console.warn(`Dropping invalid priority '${priority}'`)
    cookie = serialize('sid', val, {})
  } else throw err
}

When it happens

Trigger: serialize(name, val, { priority: 'High ' }) with trailing whitespace is fine after trim but { priority: 'urgent' }, { priority: 1 }, { priority: 'critical' } all throw; also non-lowercase variants are OK ('HIGH' works) but anything outside the three enum values throws.

Common situations: Config value mapping where authors assumed other levels exist ('critical', 'normal'); passing a numeric enum instead of a string; upstream data with priorities from a different system; typos like 'hight' or 'meduim'.

Related errors

• option domain is invalid: ${options.domain}
• option path is invalid: ${options.path}
• option expires is invalid: ${options.expires}
• option sameSite is invalid: ${options.sameSite}
• argument name is invalid: ${name}

AI-assisted analysis of nextauthjs/next-auth@a1a16a5a77 (2026-08-28). Data as JSON: /api/errors/ef0d1edc4a6738a1. Report an issue: GitHub.