deepseek-ai/deepseek-harness · error · Error

${subject} message must have role "${expectedRole}"

Error message

${subject} message must have role "${expectedRole}"

What it means

Error "${subject} message must have role "${expectedRole}"" thrown in deepseek-ai/deepseek-harness.

Source

Thrown at packages/core/session/src/index.ts:318

/** Validate only the event-specific invariants needed to safely replay a message. */
function assertMessageEventShape(event: Record<string, unknown>, subject: string): void {
  const type = event['type']
  if (type !== 'user/message' && type !== 'assistant/message'
    && type !== 'tool/result') return
  const data = event['data']
  const record = typeof data === 'object' && data !== null
    ? data as Record<string, unknown>
    : undefined
  const message = type === 'user/message' ? record : record?.['message']
  if (typeof message !== 'object' || message === null
    || typeof (message as Record<string, unknown>)['id'] !== 'string'
    || (message as Record<string, unknown>)['id'] === '') {
    throw new Error(`${subject} lacks an identified message`)
  }
  const messageRecord = message as Record<string, unknown>
  const expectedRole = type === 'assistant/message' ? 'assistant' : 'user'
  if (messageRecord['role'] !== expectedRole) {
    throw new Error(`${subject} message must have role "${expectedRole}"`)
  }
  const source = messageRecord['source']
  if (typeof source !== 'object' || source === null
    || typeof (source as Record<string, unknown>)['kind'] !== 'string'
    || (source as Record<string, unknown>)['kind'] === '') {
    throw new Error(`${subject} message has invalid source`)
  }
  if (!Array.isArray(messageRecord['content'])) {
    throw new Error(`${subject} message has invalid content`)
  }
  const sourceRecord = source as Record<string, unknown>
  if (type === 'assistant/message') {
    if (sourceRecord['kind'] !== 'model' || !hasProviderModel(sourceRecord)) {
      throw new Error(`${subject} message must have model source`)
    }
    return
  }
  if (type !== 'tool/result') return

View on GitHub (pinned to b150a551b8)

Solutions

1. Use the expected role for the subject message.

When it happens

Trigger: Thrown at packages/core/session/src/index.ts:318 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/b147e520cf4055d1. Report an issue: GitHub.