mem0ai/mem0 · error

messages array cannot contain only blank content. Provide at

Error message

messages array cannot contain only blank content. Provide at least one message with non-empty content.

What it means

Thrown by the OSS Memory.add() method when the messages argument is an array in which every message has string content that is empty or whitespace-only. The SDK refuses to spend an LLM/embedding call on input that carries no information. It is a client-side validation guard that fires before any provider call.

Source

Thrown at mem0-ts/src/oss/src/memory/index.ts:750

    }

    // 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(
      config?.metadata,
    );

    await this._ensureInitialized();
    await this._captureEvent("add", {
      message_count: Array.isArray(messages) ? messages.length : 1,
      has_metadata: !!config.metadata,
      has_filters: !!config.filters,

View on GitHub (pinned to 001c235229)

Solutions

1. Filter or reject blank messages before calling add(): messages.filter(m => typeof m.content !== 'string' || m.content.trim() !== '')
2. If the array becomes empty after filtering, validate earlier in your pipeline and skip the add() call entirely
3. Check that message objects actually carry the content field and it was not renamed (e.g. 'text') during mapping

Example fix

// before
await memory.add([{ role: 'user', content: '   ' }]);

// after
const msgs = transcript.filter(m => m.content?.trim());
if (msgs.length) {
  await memory.add(msgs);
}

const hasContent = (msgs) =>
  Array.isArray(msgs)
    ? msgs.some((m) => typeof m.content !== 'string' || m.content.trim() !== '')
    : msgs.trim() !== '';
if (!hasContent(messages)) throw new Error('nothing to memorize');

try { await memory.add(messages, { userId }); } catch (e) { if (e instanceof Error && e.message.includes('blank content')) { /* skip empty input */ } else throw e; }

When it happens

Trigger: Calling memory.add(messages) where messages is a non-empty array and messages.every(m => typeof m.content === 'string' && m.content.trim() === '') is true, e.g. memory.add([{ role: 'user', content: ' ' }]). Non-string content (e.g. image parts) makes every() false, so only all-blank string arrays trigger it.

Common situations: Passing user input straight from a form/chat UI where the user submitted whitespace; upstream trimming that reduces content to ''; transcript arrays whose text fields were dropped during JSON transformation.

Related errors

• messages string cannot be empty. Provide non-empty content.
• One of the filters: userId, agentId or runId is required!
• Either memoryId or --all is required
• At least one entity ID is required for deleteEntities.
• Unknown LLM provider: ${providerId}

AI-assisted analysis of mem0ai/mem0@001c235229 (2026-08-15). Data as JSON: /api/errors/b3bf9962d2685874. Report an issue: GitHub.