langchain-ai/langgraph · error · DuplicateHandlerError

Blob encryptor already registered

Error message

Blob encryptor already registered

What it means

Error "Blob encryptor already registered" thrown in langchain-ai/langgraph.

Source

Thrown at libs/sdk-py/langgraph_sdk/encryption/__init__.py:104

            ```python
            @encryption.encrypt.blob
            async def encrypt_blob(ctx: EncryptionContext, blob: bytes) -> bytes:
                # Encrypt the blob using your encryption service
                return encrypted_blob
            ```

        Args:
            fn: The encryption handler function

        Returns:
            The registered handler function

        Raises:
            DuplicateHandlerError: If blob encryptor already registered
            TypeError: If handler has invalid signature
        """
        if self._parent._blob_encryptor is not None:
            raise DuplicateHandlerError("Blob encryptor already registered")
        _validate_handler(fn, "Blob encryptor")
        self._parent._blob_encryptor = fn
        return fn

    def json(self, fn: types.JsonEncryptor) -> types.JsonEncryptor:
        """Register the JSON encryption handler.

        Example:
            ```python
            @encryption.encrypt.json
            async def encrypt_json(ctx: EncryptionContext, data: dict) -> dict:
                # Encrypt the data
                return encrypt_data(data)
            ```

        Args:
            fn: The encryption handler function

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/sdk-py/langgraph_sdk/encryption/__init__.py:104 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/b170e041de643578. Report an issue: GitHub.