deepseek-ai/deepseek-harness · error · MaterializeError

undefined is not JSON data

Error message

undefined is not JSON data

What it means

Error "undefined is not JSON data" thrown in deepseek-ai/deepseek-harness.

Source

Thrown at packages/workflow/workflow-worker-thread/src/realm.ts:94

}

function materialize(value: unknown, path: string, seen: Set<object>): unknown {
  switch (typeof value) {
    case 'boolean':
    case 'string':
      return value
    case 'number': {
      if (!Number.isFinite(value)) throw new MaterializeError(path, 'non-finite numbers are not JSON data')
      return value
    }
    case 'bigint':
      throw new MaterializeError(path, 'bigints are not JSON data')
    case 'function':
      throw new MaterializeError(path, 'functions are not plain JSON data')
    case 'symbol':
      throw new MaterializeError(path, 'symbols are not plain JSON data')
    case 'undefined':
      throw new MaterializeError(path, 'undefined is not JSON data')
    case 'object':
      break
  }
  if (value === null) return null
  const objectValue: object = value
  if (seen.has(objectValue)) throw new MaterializeError(path, 'circular references are not JSON data')
  seen.add(objectValue)
  try {
    if (Array.isArray(objectValue)) return materializeArray(objectValue, path, seen)
    return materializeObject(objectValue, path, seen)
  } finally {
    seen.delete(objectValue)
  }
}

function materializeArray(value: unknown[], path: string, seen: Set<object>): unknown[] {
  const out: unknown[] = []
  for (let index = 0; index < value.length; index++) {

View on GitHub (pinned to b150a551b8)

Solutions

1. Replace undefined with null or omit the property before returning the value.

When it happens

Trigger: Thrown at packages/workflow/workflow-worker-thread/src/realm.ts:94 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of deepseek-ai/deepseek-harness@b150a551b8 (2026-08-24). Data as JSON: /api/errors/6df94e5995709e67. Report an issue: GitHub.