langchain-ai/langgraph · error · ImportError

Pycryptodome is not installed. Please install it with `pip…

Error message

Pycryptodome is not installed. Please install it with `pip install pycryptodome`.

What it means

Optional-dependency guard in EncryptedSerializer.from_pycryptodome_aes: the classmethod tries `from Crypto.Cipher import AES` to build an AES cipher; the ImportError is intercepted and re-raised as this actionable ImportError. It fires only because the pycryptodome distribution is absent from the environment — the input at fault is the environment, not any argument.

Solutions

1. Install the optional dependency: pip install pycryptodome
2. Or add langgraph-checkpoint[encryption] if such an extra is declared in your install
3. Verify with `python -c "from Crypto.Cipher import AES"` after installing

When it happens

Trigger: Thrown at libs/checkpoint/langgraph/checkpoint/serde/encrypted.py:46 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of langchain-ai/langgraph@38031739e5 (2026-08-26). Data as JSON: /api/errors/bf89a44eb6fadee6. Report an issue: GitHub.

Appendix: source

Thrown at libs/checkpoint/langgraph/checkpoint/serde/encrypted.py:46

        # unencrypted data
        if "+" not in enc_cipher:
            return self.serde.loads_typed(data)
        # extract cipher name
        typ, ciphername = enc_cipher.split("+", 1)
        # decrypt data
        decrypted_data = self.cipher.decrypt(ciphername, ciphertext)
        # deserialize data
        return self.serde.loads_typed((typ, decrypted_data))

    @classmethod
    def from_pycryptodome_aes(
        cls, serde: SerializerProtocol = JsonPlusSerializer(), **kwargs: Any
    ) -> "EncryptedSerializer":
        """Create an `EncryptedSerializer` using AES encryption."""
        try:
            from Crypto.Cipher import AES
        except ImportError:
            raise ImportError(
                "Pycryptodome is not installed. Please install it with `pip install pycryptodome`."
            ) from None

        # check if AES key is provided
        if "key" in kwargs:
            key: bytes = kwargs.pop("key")
        else:
            key_str = os.getenv("LANGGRAPH_AES_KEY")
            if key_str is None:
                raise ValueError("LANGGRAPH_AES_KEY environment variable is not set.")
            key = key_str.encode()
            if len(key) not in (16, 24, 32):
                raise ValueError("LANGGRAPH_AES_KEY must be 16, 24, or 32 bytes long.")

        # set default mode to EAX if not provided
        if kwargs.get("mode") is None:
            kwargs["mode"] = AES.MODE_EAX

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