deepseek-ai/deepseek-harness · error · Error

session header parentSession must be a string

Error message

session header parentSession must be a string

What it means

Error "session header parentSession must be a string" thrown in deepseek-ai/deepseek-harness.

Source

Thrown at packages/core/session/src/index.ts:119

  if (record.version !== SESSION_FORMAT_VERSION) {
    throw new Error(`session header version must be ${SESSION_FORMAT_VERSION}, got ${String(record.version)}`)
  }
  if (record.id !== id) {
    throw new Error(`session header id "${String(record.id)}" does not match session id "${id}"`)
  }
  if (typeof record.createdAt !== 'number'
    || !Number.isSafeInteger(record.createdAt)
    || record.createdAt < 0) {
    throw new Error('session header createdAt must be a non-negative safe integer')
  }
  if (record.cwd !== undefined) {
    if (typeof record.cwd !== 'string') throw new Error('session header cwd must be a string')
    if (!isAbsolute(record.cwd)) {
      throw new Error(`session header cwd must be an absolute path, got "${record.cwd}"`)
    }
  }
  if (record.parentSession !== undefined && typeof record.parentSession !== 'string') {
    throw new Error('session header parentSession must be a string')
  }
  if (record.seedLength !== undefined
    && (typeof record.seedLength !== 'number' || !Number.isSafeInteger(record.seedLength) || record.seedLength < 0)) {
    throw new Error('session header seedLength must be a non-negative safe integer')
  }
  if (record.origin !== undefined && record.origin !== 'subagent') {
    throw new Error('session header origin must be "subagent"')
  }
  if (record.delegationDepth !== undefined
    && (typeof record.delegationDepth !== 'number' || !Number.isSafeInteger(record.delegationDepth) || record.delegationDepth < 0)) {
    throw new Error('session header delegationDepth must be a non-negative safe integer')
  }
  if (record.agentPreset !== undefined && typeof record.agentPreset !== 'string') {
    throw new Error('session header agentPreset must be a string')
  }
  return deepFreeze(record as unknown as SessionHeader)
}

View on GitHub (pinned to b150a551b8)

Solutions

1. Store parentSession as a string in the session header.

When it happens

Trigger: Thrown at packages/core/session/src/index.ts:119 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/3da7e56438a8157c. Report an issue: GitHub.