deepseek-ai/deepseek-harness · error · TerminalError

FOREIGN_SESSION

FOREIGN_SESSION

Error message

PTY session ${id} belongs to another agent

What it means

Error "PTY session ${id} belongs to another agent" thrown in deepseek-ai/deepseek-harness.

Source

Thrown at packages/terminal/terminal/src/index.ts:390

  }

  private async abortPendingSpawns(owner: Agent | undefined, reason: TerminalError): Promise<void> {
    const pending = owner === undefined
      ? [...this.pendingSpawns.values()].flatMap(owned => [...owned])
      : [...(this.pendingSpawns.get(owner) ?? [])]
    for (const spawn of pending) spawn.controller.abort(reason)
    await Promise.all(pending.map(spawn => spawn.settled))
    const failures = pending.flatMap(spawn => spawn.cleanupFailure === undefined ? [] : [spawn.cleanupFailure.error])
    for (const spawn of pending) this.removePendingSpawn(spawn)
    if (failures.length > 0) {
      throw new AggregateError(failures, 'failed to roll back unpublished PTY setup')
    }
  }

  private expectOwned(owner: Agent, id: TerminalSessionId): SessionRecord {
    const record = this.sessions.get(id)
    if (record === undefined) throw new TerminalError(`unknown PTY session ${id}`, 'NO_SESSION')
    if (record.owner !== owner) throw new TerminalError(`PTY session ${id} belongs to another agent`, 'FOREIGN_SESSION')
    return record
  }

  private snapshot(record: SessionRecord): TerminalSessionSnapshot
  private snapshot(record: SessionRecord, motd: string): TerminalSpawnResult
  private snapshot(record: SessionRecord, motd?: string): TerminalSpawnResult | TerminalSessionSnapshot {
    return {
      sessionId: record.id,
      ...record.name !== undefined ? { name: record.name } : {},
      type: record.type,
      ...record.session.pid !== undefined ? { pid: record.session.pid } : {},
      status: record.session.status(),
      ...motd !== undefined ? { motd } : {},
    }
  }

  private async abortAndClose(owner: Agent | undefined, abortReason: TerminalError, closeReason: string): Promise<void> {
    const failures: unknown[] = []

View on GitHub (pinned to b150a551b8)

Solutions

1. Operate only on PTY sessions owned by the calling agent.

When it happens

Trigger: Thrown at packages/terminal/terminal/src/index.ts:390 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/44be9e60986db595. Report an issue: GitHub.