deepseek-ai/deepseek-harness · error · Error

agent "${id}": sessionId and resumeSessionId are mutually ex

Error message

agent "${id}": sessionId and resumeSessionId are mutually exclusive

What it means

Error "agent "${id}": sessionId and resumeSessionId are mutually exclusive" thrown in deepseek-ai/deepseek-harness.

Source

Thrown at packages/core/agent-loop/src/index.ts:283

    /** Optional stable identity; remounts resume its materialized history, while first use creates it fresh. */
    sessionId?: SessionId
    /** Optional workspace for a fresh session. */
    cwd?: string
    /** Persisted session to resume instead of creating a fresh session. */
    resumeSessionId?: SessionId
  })[]
}

/** Agent-loop configuration after defaults and load-time validation. */
type ResolvedConfig = Config & { maxParallelToolCalls: number }

/** Reject self-contained identity conflicts before any configured agent starts. */
function validateConfiguredAgents(agents: Config['agents']): void {
  const exactIdentities = new Map<SessionId, string>()
  for (const { id, sessionId, resumeSessionId } of agents) {
    const hasResumeId = resumeSessionId !== undefined && resumeSessionId !== ''
    if (sessionId !== undefined && hasResumeId) {
      throw new Error(`agent "${id}": sessionId and resumeSessionId are mutually exclusive`)
    }
    const exactIdentity = hasResumeId ? resumeSessionId : sessionId
    if (exactIdentity === undefined) continue
    const firstId = exactIdentities.get(exactIdentity)
    if (firstId !== undefined) {
      throw new Error(`agents "${firstId}" and "${id}" use duplicate exact session identity "${exactIdentity}"`)
    }
    exactIdentities.set(exactIdentity, id)
  }
}

/** Concrete agent factory and driver service. */
export class AgentLoop extends Service implements AgentFactory {
  static inject = ['agents', 'sessions', 'llm', 'tools', 'systemPrompt']

  /** Runtime schema for declarative agents. */
  static Config = z.object({
    maxParallelToolCalls: z.number().step(1).min(1).default(DEFAULT_MAX_PARALLEL_TOOL_CALLS),

View on GitHub (pinned to b150a551b8)

Solutions

1. Pass only one of sessionId or resumeSessionId, not both.

When it happens

Trigger: Thrown at packages/core/agent-loop/src/index.ts:283 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/a214abd1738e7796. Report an issue: GitHub.