mem0ai/mem0 · error

messages array cannot be empty. Provide at least one message

Error message

messages array cannot be empty. Provide at least one message with non-empty content.

What it means

The second input validation in Memory.add(): when messages is an array it must be non-empty — an empty array throws with this message before any LLM or embedding work starts. It prevents wasting a pipeline run (and API cost) on input that could not produce a memory.

Source

Thrown at mem0-ts/src/oss/src/memory/index.ts:742

    if (config?.timestamp !== undefined) {
      await this._getNoticeTelemetryId();
      throw new Error(
        await getTemporalFeatureErrorMessage(this, {
          triggerFunction: "add",
          triggerParameter: "timestamp",
        }),
      );
    }

    // Validate messages input
    if (messages === undefined || messages === null) {
      throw new Error(
        "messages is required and cannot be undefined or null. Provide a string or array of messages.",
      );
    }
    if (Array.isArray(messages)) {
      if (messages.length === 0) {
        throw new Error(
          "messages array cannot be empty. Provide at least one message with non-empty content.",
        );
      }
      const allBlank = messages.every(
        (m) => typeof m.content === "string" && m.content.trim() === "",
      );
      if (allBlank) {
        throw new Error(
          "messages array cannot contain only blank content. Provide at least one message with non-empty content.",
        );
      }
    } else if (messages.trim() === "") {
      throw new Error(
        "messages string cannot be empty. Provide non-empty content.",
      );
    }

    const temporalUsageNotice = detectTemporalUsageFromMetadata(

View on GitHub (pinned to 001c235229)

Solutions

1. Skip the call when the array is empty: if (messages.length === 0) return;
2. Fix upstream filtering so the array retains intended content; log the pre-call length when debugging.
3. In chat loops, call add() only after at least one real message exists.
4. Batch emitters should drop empty chunks before invoking Memory.

Example fix

// before
await memory.add(history.filter((m) => m.role === 'user'), opts); // [] when bot-only history -> throws

// after
const userMsgs = history.filter((m) => m.role === 'user');
if (userMsgs.length > 0) {
  await memory.add(userMsgs, opts);
}

function hasNonEmptyMessages(messages: unknown): boolean {
  return Array.isArray(messages) && messages.length > 0;
}

function isNonEmptyMessageArray(messages: unknown): messages is { role: string; content: string }[] {
  return (
    Array.isArray(messages) &&
    messages.length > 0 &&
    messages.some((m) => typeof m?.content === 'string' && m.content.trim() !== '')
  );
}

When it happens

Trigger: Calling memory.add([], { filters: { userId: 'u1' } }), or passing a filtered/mapped array that ended up empty — e.g. messages.filter(m => m.role === 'user') when no user messages exist.

Common situations: Chat pipelines where the transcript hasn't received messages yet (add called at conversation start), arrays emptied by filtering, slicing beyond length, or spreading an empty list; batching code that emits zero-item chunks.

Related errors

• messages is required and cannot be undefined or null. Provid
• Either memoryId or --all is required
• At least one entity ID is required for deleteEntities.
• Unknown LLM provider: ${providerId}
• Unknown embedder provider: ${providerId}

AI-assisted analysis of mem0ai/mem0@001c235229 (2026-08-15). Data as JSON: /api/errors/af737eb90ce63926. Report an issue: GitHub.