mem0ai/mem0 · error · ValueError

messages must be str, dict, or list[dict], got {type(message

Error message

messages must be str, dict, or list[dict], got {type(messages).__name__}

What it means

Error "messages must be str, dict, or list[dict], got {type(messages).__name__}" thrown in mem0ai/mem0.

Source

Thrown at mem0/client/main.py:213

        Returns:
            A dictionary containing the API response in v1.1 format.

        Raises:
            ValidationError: If the input data is invalid.
            AuthenticationError: If authentication fails.
            RateLimitError: If rate limits are exceeded.
            MemoryQuotaExceededError: If memory quota is exceeded.
            NetworkError: If network connectivity issues occur.
            MemoryNotFoundError: If the memory doesn't exist (for updates/deletes).
        """
        kwargs = {**(options.model_dump(exclude_unset=True) if options else {}), **kwargs}
        # Handle different message input formats (align with OSS behavior)
        if isinstance(messages, str):
            messages = [{"role": "user", "content": messages}]
        elif isinstance(messages, dict):
            messages = [messages]
        elif not isinstance(messages, list):
            raise ValueError(f"messages must be str, dict, or list[dict], got {type(messages).__name__}")

        kwargs = self._prepare_params(kwargs)
        payload = self._prepare_payload(messages, kwargs)
        response = self.client.post("/v3/memories/add/", json=payload)
        response.raise_for_status()
        if "metadata" in kwargs:
            del kwargs["metadata"]
        capture_client_event("client.add", self, {"keys": list(kwargs.keys()), "sync_type": "sync"})
        return response.json()

    @api_error_handler
    def get(self, memory_id: str) -> Dict[str, Any]:
        """Retrieve a specific memory by ID.

        Args:
            memory_id: The ID of the memory to retrieve.

        Returns:

View on GitHub (pinned to 001c235229)

Solutions

1. Pass messages as a string, a dict like {'role':'user','content':'...'}, or a list of such dicts.

When it happens

Trigger: Thrown at mem0/client/main.py:213 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mem0ai/mem0@001c235229 (2026-08-15). Data as JSON: /api/errors/02f2a16e8a23eda3. Report an issue: GitHub.