mem0ai/mem0 · critical

Zero Entropy API key is required. Set ZERO_ENTROPY_API_KEY e

Error message

Zero Entropy API key is required. Set ZERO_ENTROPY_API_KEY environment variable or pass apiKey in config.

What it means

Thrown by the ZeroEntropyReranker constructor when neither config.apiKey nor the ZERO_ENTROPY_API_KEY environment variable is set. ZeroEntropy's rerank API (default model zerank-1) requires authentication; the check happens at construction time when RerankerFactory builds the reranker from the memory config. The zeroentropy npm peer dependency is imported lazily, so the key is the only early failure.

Source

Thrown at mem0-ts/src/oss/src/rerankers/zeroentropy.ts:17

import { RerankerConfig } from "../types";
import { Reranker, RerankResult } from "./base";
import { loadPeer } from "../utils/load_peer";

const DEFAULT_MODEL = "zerank-1";

export class ZeroEntropyReranker implements Reranker {
  private clientInstance?: any;
  private clientPromise?: Promise<any>;
  private readonly apiKey: string;
  private model: string;
  private topK?: number;

  constructor(config: RerankerConfig) {
    const apiKey = config.apiKey || process.env.ZERO_ENTROPY_API_KEY;
    if (!apiKey) {
      throw new Error(
        "Zero Entropy API key is required. Set ZERO_ENTROPY_API_KEY environment variable or pass apiKey in config.",
      );
    }
    this.apiKey = apiKey;
    this.model = config.model || DEFAULT_MODEL;
    this.topK = config.topK;
  }

  /**
   * Lazily construct (or reuse) the ZeroEntropy client, importing the
   * optional `zeroentropy` peer only when the reranker is first used so
   * consumers that never touch ZeroEntropy don't need it installed.
   */
  private async getClient(): Promise<any> {
    if (this.clientInstance) return this.clientInstance;
    if (!this.clientPromise) {
      this.clientPromise = this.createClient();
    }

View on GitHub (pinned to 001c235229)

Solutions

1. Set ZERO_ENTROPY_API_KEY in the runtime environment of the process
2. Or pass it explicitly: reranker: { provider: 'zeroentropy', config: { apiKey: process.env.ZERO_ENTROPY_API_KEY } }
3. Add a boot-time env assertion so misconfiguration fails at startup, not at first rerank

Example fix

// before
const memory = new Memory({ reranker: { provider: 'zeroentropy', config: {} } });

// after
const memory = new Memory({
  reranker: { provider: 'zeroentropy', config: { apiKey: process.env.ZERO_ENTROPY_API_KEY } },
});

if (!process.env.ZERO_ENTROPY_API_KEY) {
  throw new Error('ZERO_ENTROPY_API_KEY is not set — reranker unavailable');
}

try { new Memory({ ...config, reranker: { provider: 'zeroentropy', config: {} } }); } catch (e) { if (e instanceof Error && e.message.includes('ZERO_ENTROPY_API_KEY')) { /* degrade to no reranker */ } else throw e; }

When it happens

Trigger: Configuring reranker: { provider: 'zeroentropy', config: {...} } with no apiKey while ZERO_ENTROPY_API_KEY is absent from the process environment — env var missing in the deployed container, set in a shell the process never inherited, or misnamed.

Common situations: Secrets defined locally but not in Docker/CI/production; .env loaded after Memory construction; key name typo (ZEROENTROPY_API_KEY); new deployment target without copied secrets.

Related errors

• Cohere API key is required. Set COHERE_API_KEY environment v
• Zero Entropy API key is required. Set ZERO_ENTROPY_API_KEY e
• Cohere API key is required. Set COHERE_API_KEY environment v
• Unsupported reranker provider: ${provider}
• PGVector requires either connectionString or ${missingFields

AI-assisted analysis of mem0ai/mem0@001c235229 (2026-08-15). Data as JSON: /api/errors/c0a2824d7a9a4ca3. Report an issue: GitHub.