mem0ai/mem0 · error · ImportError

Could not import reranker for provider '{provider_name}': {e

Error message

Could not import reranker for provider '{provider_name}': {e}

What it means

Raised by RerankerFactory.create when dynamic import of the provider's reranker class via load_class(class_path) raises ImportError or AttributeError — i.e. the module mem0.reranker.<provider>_reranker cannot be imported (missing optional dependency) or the class attribute does not exist in it. The original exception text is appended, so the message tells you exactly which import failed.

Source

Thrown at mem0/utils/factory.py:278

        """
        if provider_name not in cls.provider_to_class:
            raise ValueError(f"Unsupported reranker provider: {provider_name}")

        class_path, config_class = cls.provider_to_class[provider_name]

        # Handle configuration
        if config is None:
            config = config_class(**kwargs)
        elif isinstance(config, dict):
            config = config_class(**config, **kwargs)
        elif not isinstance(config, BaseRerankerConfig):
            raise ValueError(f"Config must be a {config_class.__name__} instance or dict")

        # Import and create the reranker class
        try:
            reranker_class = load_class(class_path)
        except (ImportError, AttributeError) as e:
            raise ImportError(f"Could not import reranker for provider '{provider_name}': {e}")

        return reranker_class(config)

View on GitHub (pinned to 001c235229)

Solutions

Read the appended original error: it names the module/package that failed to import and install that package (e.g. pip install cohere or pip install sentence-transformers)
Reinstall mem0ai cleanly: pip install --force-reinstall mem0ai to restore mem0.reranker modules
Verify the class path resolves: from mem0.reranker.cohere_reranker import CohereReranker
Pin a known-good mem0ai version if a recent upgrade broke the import

Example fix

# before (ImportError: Could not import reranker ... No module named 'cohere')
reranker = RerankerFactory.create('cohere', config={'api_key': key})

# after
# pip install cohere
reranker = RerankerFactory.create('cohere', config={'api_key': key})

Defensive patterns

Strategy: validation

Validate before calling

import importlib.util
MISSING = [m for m in ('cohere',) if importlib.util.find_spec(m) is None]
if MISSING and cfg.get('reranker', {}).get('provider') == 'cohere':
    raise ConfigError(f'install reranker deps first: {MISSING}')

Type guard

def reranker_deps_available(provider: str) -> bool:
    import importlib.util
    need = {'cohere': ['cohere'], 'sentence_transformer': ['sentence_transformers'], 'huggingface': ['sentence_transformers']}
    return all(importlib.util.find_spec(m) for m in need.get(provider, []))

Try / catch

try:
    reranker = RerankerFactory.create(provider, config)
except ImportError as e:
    if 'Could not import reranker' in str(e):
        log.error('optional dependency missing for %s: %s', provider, e)
        raise
    raise

Prevention

Install optional reranker SDKs alongside mem0ai in the same requirements file
Smoke-test factory.create for each configured provider at deploy time
Pin dependency versions so imports do not drift

When it happens

Trigger: Selecting 'huggingface' or 'sentence_transformer' rerankers without sentence-transformers/torch installed; selecting 'cohere' without the cohere SDK installed; a broken/partial mem0 install where mem0.reranker.* modules are missing; a version mismatch where the class was renamed.

Common situations: Installing bare mem0ai without optional extras then enabling reranking; a venv truncated mid-install; upgrading mem0ai while old compiled deps (torch) are missing on the new Python version.

Related errors

AI-assisted analysis of mem0ai/mem0@001c235229 (2026-08-15). Data as JSON: /api/errors/211cada23e357ae2. Report an issue: GitHub.