nodejs/node · error · InvalidArgumentError

UND_ERR_INVALID_ARG

UND_ERR_INVALID_ARG

Error message

maxSize must be a number greater than 0

What it means

Thrown by the dump interceptor's `DumpHandler` constructor (`InvalidArgumentError`, code `UND_ERR_INVALID_ARG`) when `maxSize` is provided and is either not finite or less than 1. The dump interceptor reads and discards response bodies up to a cap so that request hooks (redirect handling, retry decisions) can see the response without buffering huge payloads; `maxSize` (default 1 MiB) is the byte ceiling it enforces. Values below 1 or non-finite (`NaN`, `Infinity`) are rejected because they make the cap meaningless.

Source

Thrown at deps/undici/src/lib/interceptor/dump.js:16

'use strict'

const { InvalidArgumentError, RequestAbortedError } = require('../core/errors')
const DecoratorHandler = require('../handler/decorator-handler')

class DumpHandler extends DecoratorHandler {
  #maxSize = 1024 * 1024
  #dumped = false
  #size = 0
  #controller = null
  aborted = false
  reason = false

  constructor ({ maxSize, signal }, handler) {
    if (maxSize != null && (!Number.isFinite(maxSize) || maxSize < 1)) {
      throw new InvalidArgumentError('maxSize must be a number greater than 0')
    }

    super(handler)

    this.#maxSize = maxSize ?? this.#maxSize
    // this.#handler = handler
  }

  #abort (reason) {
    this.aborted = true
    this.reason = reason
  }

  onRequestStart (controller, context) {
    controller.abort = this.#abort.bind(this)
    this.#controller = controller

    return super.onRequestStart(controller, context)

View on GitHub (pinned to 1b2de5e052)

Solutions

1. Pass a finite integer ≥1, e.g. `maxSize: 4 * 1024 * 1024` for 4 MiB.
2. If loading from config/env, coerce with `Number(...)` and check `Number.isFinite(v) && v >= 1`.
3. To use the default, omit the option entirely (1 MiB default applies).

Example fix

// before
new DumpHandler({ maxSize: 0 }, handler)
dispatch({ ..., dumpMaxSize: process.env.DUMP_SIZE })

// after
new DumpHandler({ maxSize: 2 * 1024 * 1024 }, handler)
dispatch({ ..., dumpMaxSize: Number(process.env.DUMP_SIZE) })

function validateMaxSize(v) {
  if (v == null) return undefined
  const n = Number(v)
  if (!Number.isFinite(n) || n < 1) {
    throw new Error('maxSize must be a finite number >= 1')
  }
  return n
}

function isValidMaxSize(v) {
  return typeof v === 'number' && Number.isFinite(v) && v >= 1
}

When it happens

Trigger: Passing `maxSize: 0`, a negative number, `NaN`, a string, or `Infinity`. Constructed via `new DumpHandler({ maxSize }, handler)` or through the interceptor with `dumpMaxSize` in dispatch opts. Note the constructor checks `maxSize < 1`, so the minimum is 1 byte.

Common situations: Setting `dumpMaxSize: 0` intending 'don't dump' (it errors instead); reading the cap from env as a string; passing a human-readable size. The interceptor's `createDumpInterceptor` reads `opts.dumpMaxSize`, so the validation surfaces when you dispatch with an invalid per-request override.

Related errors

• expected opts.maxBufferSize to be a positive finite number,
• expected opts.methods to be an array, got ${typeof methods}
• expected opts.skipHeaderNames to be an array, got ${typeof s
• expected opts.excludeHeaderNames to be an array, got ${typeo
• Invalid maxTTL. Must be a positive number

AI-assisted analysis of nodejs/node@1b2de5e052 (2026-08-13). Data as JSON: /api/errors/28ccaf64e329f654. Report an issue: GitHub.