diff --git a/src/rotator_library/core/__init__.py b/src/rotator_library/core/__init__.py
index c88a75a5..aa405479 100644
--- a/src/rotator_library/core/__init__.py
+++ b/src/rotator_library/core/__init__.py
@@ -28,6 +28,7 @@
     NoAvailableKeysError,
     PreRequestCallbackError,
     CredentialNeedsReauthError,
+    IFlowNoAPIKeyError,
     EmptyResponseError,
     TransientQuotaError,
     StreamedAPIError,
@@ -59,6 +60,7 @@
     "NoAvailableKeysError",
     "PreRequestCallbackError",
     "CredentialNeedsReauthError",
+    "IFlowNoAPIKeyError",
     "EmptyResponseError",
     "TransientQuotaError",
     "StreamedAPIError",
diff --git a/src/rotator_library/core/errors.py b/src/rotator_library/core/errors.py
index 5acd9fc7..8d0268e1 100644
--- a/src/rotator_library/core/errors.py
+++ b/src/rotator_library/core/errors.py
@@ -18,6 +18,7 @@
     NoAvailableKeysError,
     PreRequestCallbackError,
     CredentialNeedsReauthError,
+    IFlowNoAPIKeyError,
     EmptyResponseError,
     TransientQuotaError,
     # Error classification
@@ -67,6 +68,7 @@ def __init__(self, message: str, data=None):
     "NoAvailableKeysError",
     "PreRequestCallbackError",
     "CredentialNeedsReauthError",
+    "IFlowNoAPIKeyError",
     "EmptyResponseError",
     "TransientQuotaError",
     "StreamedAPIError",
diff --git a/src/rotator_library/error_handler.py b/src/rotator_library/error_handler.py
index 9fd252c7..8eeca2a4 100644
--- a/src/rotator_library/error_handler.py
+++ b/src/rotator_library/error_handler.py
@@ -159,6 +159,34 @@ def __init__(self, credential_path: str, message: str = ""):
         super().__init__(self.message)
 
 
+class IFlowNoAPIKeyError(Exception):
+    """
+    Raised when an iFlow account has not set up an API key yet.
+
+    This occurs when using cookie-based authentication with a new iFlow account
+    that hasn't created an API key through the web interface.
+
+    Unlike ValueError, this exception can be caught programmatically to:
+    - Trigger OAuth authentication (which auto-creates an API key)
+    - Provide clear guidance to the user
+    - Distinguish from other authentication failures
+
+    Attributes:
+        message: Human-readable message with guidance on how to fix
+        account_identifier: Optional identifier for the account (e.g., email or name)
+    """
+
+    def __init__(self, message: str = "", account_identifier: str = ""):
+        self.account_identifier = account_identifier
+        self.message = message or (
+            "This iFlow account has not set up an API key yet. "
+            "Please either:\n"
+            "1. Use OAuth authentication (run with --oauth flag) which will automatically create an API key, OR\n"
+            "2. Manually create an API key at https://platform.iflow.cn/ and try again"
+        )
+        super().__init__(self.message)
+
+
 class EmptyResponseError(Exception):
     """
     Raised when a provider returns an empty response after multiple retry attempts.
diff --git a/src/rotator_library/providers/iflow_auth_base.py b/src/rotator_library/providers/iflow_auth_base.py
index 0ac03208..cc386db8 100644
--- a/src/rotator_library/providers/iflow_auth_base.py
+++ b/src/rotator_library/providers/iflow_auth_base.py
@@ -29,7 +29,11 @@
 from ..utils.headless_detection import is_headless_environment
 from ..utils.reauth_coordinator import get_reauth_coordinator
 from ..utils.resilient_io import safe_write_json
-from ..error_handler import CredentialNeedsReauthError
+from ..error_handler import (
+    CredentialNeedsReauthError,
+    IFlowNoAPIKeyError,
+    mask_credential,
+)
 
 lib_logger = logging.getLogger("rotator_library")
 
@@ -676,6 +680,15 @@ async def _fetch_api_key_info_with_cookie(self, cookie: str) -> Dict[str, Any]:
             error_msg = result.get("message", "Unknown error")
             raise ValueError(f"Cookie authentication failed: {error_msg}")
 
+        # Check if data is explicitly None (null) - indicates no API key exists yet
+        if result.get("data") is None:
+            lib_logger.warning(
+                "iFlow API returned null data - account has no API key configured"
+            )
+            bx_auth_value = extract_bx_auth(cookie) or ""
+            masked_identifier = f"BXAuth={mask_credential(bx_auth_value)};"
+            raise IFlowNoAPIKeyError(account_identifier=masked_identifier)
+
         data = result.get("data") or {}
 
         # Handle case where apiKey is masked - use apiKeyMask if apiKey is empty