vercel/next.js · error · Error

Draft mode cannot be disabled during build-time instant vali

Error message

Draft mode cannot be disabled during build-time instant validation.

What it means

The companion to error 151: the instant-validation DraftModeProvider.disable() stub throws because disabling draft mode is meaningless during build-time validation (draft mode is never enabled there). Any call to draftMode().disable() in code exercised by instant validation triggers it.

Source

Thrown at packages/next/src/server/app-render/instant-validation/instant-samples.ts:244

/**
 * Creates a DraftModeProvider that always returns isEnabled: false.
 */
export function createDraftModeForValidation(): DraftModeProvider {
  // Create a minimal DraftModeProvider-compatible object
  // that always reports draft mode as disabled.
  //
  // private properties that can't be set from outside the class.
  return {
    get isEnabled() {
      return false
    },
    enable() {
      throw new Error(
        'Draft mode cannot be enabled during build-time instant validation.'
      )
    },
    disable() {
      throw new Error(
        'Draft mode cannot be disabled during build-time instant validation.'
      )
    },
  } as Partial<DraftModeProvider> as DraftModeProvider
}

/**
 * Creates params wrapped with an exhaustive proxy.
 * Accessing a param not declared in the sample will throw an error.
 */
export function createExhaustiveParamsProxy<TParams extends Params>(
  underlyingParams: TParams,
  declaredParamNames: Set<string>,
  route: string
): TParams {
  return new Proxy(underlyingParams, {
    get(target, prop, receiver) {
      if (

View on GitHub (pinned to 0ae8c72462)

Solutions

1. Guard draftMode().disable() so it does not run during build/validation.
2. Place draft-mode disable logic in a runtime-only route handler excluded from validation.
3. Condition the call on a real request context (e.g. presence of a query param).
4. Ensure the disable path is not reachable from statically-validated routes.

Example fix

// before
// export default function Handler() { draftMode().disable() }

// after
// if (process.env.NEXT_RUNTIME) draftMode().disable()

// Skip draft-mode disablement during build/validation.
function disablePreview() {
  if (process.env.NEXT_PHASE === 'phase-production-build') return
  draftMode().disable()
}

When it happens

Trigger: During instant validation, application code calls draftMode().disable(). The validation provider's disable() throws.

Common situations: A 'disable preview' route handler or a component that clears draft mode is run during validation; shared cleanup code unconditionally disables draft mode; preview-exit logic invoked at build time.

Related errors

• Draft mode cannot be enabled during build-time instant valid
• Invalid sample: Defining cookies via a "cookie" header is no
• Expected sample param value for segment '${rawSegment}' to b
• Expected sample param value for segment '${rawSegment}' to b
• Invalid --top value: ${topRaw}

AI-assisted analysis of vercel/next.js@0ae8c72462 (2026-08-06). Data as JSON: /api/errors/c1676227d8ef7f8e. Report an issue: GitHub.