langchain-ai/langgraph · error · DuplicateHandlerError

Blob decryptor already registered

Error message

Blob decryptor already registered

What it means

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

Source

Thrown at libs/sdk-py/langgraph_sdk/encryption/__init__.py:173

            async def decrypt_blob(
                ctx: EncryptionContext, blob: bytes
            ) -> bytes | DecryptResult[bytes]:
                # Decrypt the blob using your encryption service
                return decrypted_blob
            ```

        Args:
            fn: The decryption handler function

        Returns:
            The registered handler function

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

    def json(self, fn: _JsonDecryptorT) -> _JsonDecryptorT:
        """Register the JSON decryption handler.

        Example:
            ```python
            @encryption.decrypt.json
            async def decrypt_json(
                ctx: EncryptionContext, data: dict
            ) -> dict | DecryptResult[dict]:
                # Decrypt the data
                return decrypt_data(data)
            ```

        Args:

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/sdk-py/langgraph_sdk/encryption/__init__.py:173 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/4ca3b0f6789588c1. Report an issue: GitHub.