diff --git a/litellm/__init__.py b/litellm/__init__.py
index 9eb3f075d5ec..d372c737a668 100644
--- a/litellm/__init__.py
+++ b/litellm/__init__.py
@@ -199,6 +199,7 @@
 openai_key: Optional[str] = None
 groq_key: Optional[str] = None
 gigachat_key: Optional[str] = None
+xai_key: Optional[str] = None
 databricks_key: Optional[str] = None
 openai_like_key: Optional[str] = None
 azure_key: Optional[str] = None
diff --git a/litellm/llms/xai/chat/transformation.py b/litellm/llms/xai/chat/transformation.py
index 245e10e45c12..3f9b2085822f 100644
--- a/litellm/llms/xai/chat/transformation.py
+++ b/litellm/llms/xai/chat/transformation.py
@@ -4,6 +4,7 @@
 
 import litellm
 from litellm._logging import verbose_logger
+from litellm.llms.xai.common_utils import XAIModelInfo
 from litellm.litellm_core_utils.prompt_templates.common_utils import (
     filter_value_from_dict,
     strip_name_from_messages,
@@ -26,7 +27,7 @@ def _get_openai_compatible_provider_info(
         self, api_base: Optional[str], api_key: Optional[str]
     ) -> Tuple[Optional[str], Optional[str]]:
         api_base = api_base or get_secret_str("XAI_API_BASE") or XAI_API_BASE  # type: ignore
-        dynamic_api_key = api_key or get_secret_str("XAI_API_KEY")
+        dynamic_api_key = XAIModelInfo.get_api_key(api_key)
         return api_base, dynamic_api_key
 
     def get_supported_openai_params(self, model: str) -> list:
diff --git a/litellm/llms/xai/common_utils.py b/litellm/llms/xai/common_utils.py
index df324cf3ee22..f2c6b935e366 100644
--- a/litellm/llms/xai/common_utils.py
+++ b/litellm/llms/xai/common_utils.py
@@ -46,7 +46,12 @@ def get_api_base(api_base: Optional[str] = None) -> Optional[str]:
 
     @staticmethod
     def get_api_key(api_key: Optional[str] = None) -> Optional[str]:
-        return api_key or get_secret_str("XAI_API_KEY")
+        return (
+            api_key
+            or litellm.xai_key
+            or get_secret_str("XAI_API_KEY")
+            or litellm.api_key
+        )
 
     @staticmethod
     def get_base_model(model: str) -> Optional[str]:
diff --git a/litellm/llms/xai/responses/transformation.py b/litellm/llms/xai/responses/transformation.py
index bd422c8d81e0..740e2a13aeb9 100644
--- a/litellm/llms/xai/responses/transformation.py
+++ b/litellm/llms/xai/responses/transformation.py
@@ -2,6 +2,7 @@
 
 import litellm
 from litellm._logging import verbose_logger
+from litellm.llms.xai.common_utils import XAIModelInfo
 from litellm.llms.openai.responses.transformation import OpenAIResponsesAPIConfig
 from litellm.secret_managers.main import get_secret_str
 from litellm.types.llms.openai import ResponsesAPIOptionalRequestParams
@@ -103,11 +104,7 @@ def validate_environment(
         Uses XAI_API_KEY from environment or litellm_params.
         """
         litellm_params = litellm_params or GenericLiteLLMParams()
-        api_key = (
-            litellm_params.api_key
-            or litellm.api_key
-            or get_secret_str("XAI_API_KEY")
-        )
+        api_key = XAIModelInfo.get_api_key(litellm_params.api_key)
         
         if not api_key:
             raise ValueError(
@@ -143,4 +140,3 @@ def get_complete_url(
         api_base = api_base.rstrip("/")
         
         return f"{api_base}/responses"
-
diff --git a/tests/litellm/llms/xai/test_xai_key_fallback.py b/tests/litellm/llms/xai/test_xai_key_fallback.py
new file mode 100644
index 000000000000..a678d961ad54
--- /dev/null
+++ b/tests/litellm/llms/xai/test_xai_key_fallback.py
@@ -0,0 +1,100 @@
+import os
+import litellm
+from litellm.llms.xai.chat.transformation import XAIChatConfig
+from litellm.llms.xai.common_utils import XAIModelInfo
+from litellm.llms.xai.responses.transformation import XAIResponsesAPIConfig
+
+
+def test_get_api_key_priority():
+    """
+    Test the fallback order of XAI API key resolution:
+    1. api_key parameter
+    2. litellm.xai_key
+    3. XAI_API_KEY environment variable
+    4. litellm.api_key
+    5. None
+    """
+
+    original_env = os.environ.get("XAI_API_KEY")
+    had_env = "XAI_API_KEY" in os.environ
+    original_xai_key = litellm.xai_key
+    original_api_key = litellm.api_key
+
+    try:
+        # Case 1: api_key parameter is passed
+        litellm.xai_key = "xai_key_value"
+        litellm.api_key = "common_api_key"
+        os.environ["XAI_API_KEY"] = "env_api_key"
+        result = XAIModelInfo.get_api_key("param_api_key")
+        assert result == "param_api_key"
+
+        # Case 2: api_key not passed, use litellm.xai_key
+        result = XAIModelInfo.get_api_key(None)
+        assert result == "xai_key_value"
+
+        # Case 3: api_key and xai_key not set, prefer XAI_API_KEY over litellm.api_key
+        litellm.xai_key = None
+        result = XAIModelInfo.get_api_key(None)
+        assert result == "env_api_key"
+
+        # Case 4: Empty XAI_API_KEY falls through to litellm.api_key
+        os.environ["XAI_API_KEY"] = ""
+        result = XAIModelInfo.get_api_key(None)
+        assert result == "common_api_key"
+
+        # Case 5: None of the above, return None
+        os.environ.pop("XAI_API_KEY", None)
+        litellm.api_key = None
+        result = XAIModelInfo.get_api_key(None)
+        assert result is None
+    finally:
+        if had_env:
+            os.environ["XAI_API_KEY"] = original_env
+        else:
+            os.environ.pop("XAI_API_KEY", None)
+        litellm.xai_key = original_xai_key
+        litellm.api_key = original_api_key
+
+
+def test_chat_config_uses_xai_key_fallback():
+    original_env = os.environ.get("XAI_API_KEY")
+    had_env = "XAI_API_KEY" in os.environ
+    original_xai_key = litellm.xai_key
+    original_api_key = litellm.api_key
+
+    try:
+        litellm.xai_key = "xai_key_value"
+        litellm.api_key = None
+        os.environ.pop("XAI_API_KEY", None)
+        _, api_key = XAIChatConfig()._get_openai_compatible_provider_info(None, None)
+        assert api_key == "xai_key_value"
+    finally:
+        if had_env:
+            os.environ["XAI_API_KEY"] = original_env
+        else:
+            os.environ.pop("XAI_API_KEY", None)
+        litellm.xai_key = original_xai_key
+        litellm.api_key = original_api_key
+
+
+def test_responses_config_uses_xai_key_fallback():
+    original_env = os.environ.get("XAI_API_KEY")
+    had_env = "XAI_API_KEY" in os.environ
+    original_xai_key = litellm.xai_key
+    original_api_key = litellm.api_key
+
+    try:
+        litellm.xai_key = "xai_key_value"
+        litellm.api_key = None
+        os.environ.pop("XAI_API_KEY", None)
+        headers = XAIResponsesAPIConfig().validate_environment(
+            {}, "xai/grok-3-mini", None
+        )
+        assert headers["Authorization"] == "Bearer xai_key_value"
+    finally:
+        if had_env:
+            os.environ["XAI_API_KEY"] = original_env
+        else:
+            os.environ.pop("XAI_API_KEY", None)
+        litellm.xai_key = original_xai_key
+        litellm.api_key = original_api_key