deepseek-ai/deepseek-harness · error · Error

${subject} message must have tool source

Error message

${subject} message must have tool source

What it means

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

Source

Thrown at packages/core/session/src/index.ts:340

    || 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(`${subject} message must have model source`)
    }
    return
  }
  if (type !== 'tool/result') return
  if (sourceRecord['kind'] !== 'tool'
    || typeof sourceRecord['callId'] !== 'string'
    || sourceRecord['callId'] === '') {
    throw new Error(`${subject} message must have tool source`)
  }
  const content = messageRecord['content'] as unknown[]
  const block = content[0]
  if (content.length !== 1 || typeof block !== 'object' || block === null
    || (block as Record<string, unknown>)['type'] !== 'tool-result'
    || !Array.isArray((block as Record<string, unknown>)['content'])) {
    throw new Error(`${subject} message must contain one tool-result block`)
  }
  if ((block as Record<string, unknown>)['toolCallId'] !== sourceRecord['callId']) {
    throw new Error(`${subject} message has mismatched tool call ids`)
  }
}

/** Whether an unknown value carries the current provider/model pair. */
function hasProviderModel(value: unknown): boolean {
  if (typeof value !== 'object' || value === null) return false
  const pair = value as Record<string, unknown>
  return typeof pair['provider'] === 'string' && pair['provider'].length > 0

View on GitHub (pinned to b150a551b8)

Solutions

1. Use tool as the source of the subject message.

When it happens

Trigger: Thrown at packages/core/session/src/index.ts:340 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/8ffb768894f8f6e3. Report an issue: GitHub.