diff --git a/litellm/llms/apodex/chat/transformation.py b/litellm/llms/apodex/chat/transformation.py
index a1b13633f66..5b7e1e8ee6b 100644
--- a/litellm/llms/apodex/chat/transformation.py
+++ b/litellm/llms/apodex/chat/transformation.py
@@ -14,6 +14,7 @@ Ref: https://platform.apodex.ai/docs/chat-completions
 from collections.abc import Mapping
 from typing import Final
 
+import litellm
 from litellm.llms.openai.chat.gpt_transformation import OpenAIGPTConfig
 from litellm.types.llms.openai import AllMessageValues
 
@@ -22,6 +23,7 @@ from ..common_utils import (
     get_apodex_api_base,
     get_apodex_api_key,
     is_deep_research_model,
+    is_responses_only_model,
 )
 
 _DEEP_RESEARCH_PARAMS: Final = (
@@ -87,6 +89,13 @@ class ApodexChatConfig(OpenAIGPTConfig):
         model: str,
         drop_params: bool,
     ) -> dict:  # mutable-ok: matches the base-class signature
+        if is_responses_only_model(model):
+            raise litellm.BadRequestError(
+                message=f"apodex model {model} is only available through /v1/responses",
+                model=model,
+                llm_provider="apodex",
+            )
+
         mapped: Final = super().map_openai_params(
             non_default_params=non_default_params,
             optional_params=optional_params,
@@ -94,7 +103,6 @@ class ApodexChatConfig(OpenAIGPTConfig):
             drop_params=drop_params,
         )
 
-        # Apodex documents max_tokens only.
         renamed: Final = (
             mapped
             if "max_completion_tokens" not in mapped
@@ -109,18 +117,9 @@ class ApodexChatConfig(OpenAIGPTConfig):
         if renamed.get("stream"):
             return renamed
 
-        # The OpenAI chat handler pops `stream` out of the params it forwards
-        # (litellm/llms/openai/openai.py), which would leave the Deep Research tiers
-        # on their streaming default. extra_body is merged into the request body
-        # further down, so it survives that pop.
-        requested_extra_body: Final = renamed.get("extra_body")
-        extra_body: Final = (
-            requested_extra_body if isinstance(requested_extra_body, Mapping) else {}  # mutable-ok: JSON request body
-        )
         return {  # mutable-ok: JSON request body
             **renamed,
             _PIN_NON_STREAMING: True,
-            "extra_body": {**extra_body, "stream": False},  # mutable-ok: JSON request body
         }
 
     def transform_request(
@@ -131,12 +130,12 @@ class ApodexChatConfig(OpenAIGPTConfig):
         litellm_params: dict,  # mutable-ok: matches the base-class signature
         headers: dict,  # mutable-ok: matches the base-class signature
     ) -> dict:  # mutable-ok: JSON request body
-        """Apply the non-streaming pin after LiteLLM merges caller ``extra_body``."""
-        pin_non_streaming: Final = bool(optional_params.pop(_PIN_NON_STREAMING, False))
+        pin_non_streaming: Final = bool(optional_params.get(_PIN_NON_STREAMING, False))
+        forwarded_params: Final = {key: value for key, value in optional_params.items() if key != _PIN_NON_STREAMING}
         transformed: Final = super().transform_request(
             model=model,
             messages=messages,
-            optional_params=optional_params,
+            optional_params=forwarded_params,
             litellm_params=litellm_params,
             headers=headers,
         )
diff --git a/litellm/llms/apodex/common_utils.py b/litellm/llms/apodex/common_utils.py
index ad29673ff4b..12dcb1414b6 100644
--- a/litellm/llms/apodex/common_utils.py
+++ b/litellm/llms/apodex/common_utils.py
@@ -17,6 +17,7 @@ from litellm.secret_managers.main import get_secret_str
 APODEX_API_BASE_URL: Final = "https://api.apodex.ai/v1"
 
 _DEEP_RESEARCH_MARKER: Final = "-deep-"
+_RESPONSES_ONLY_MODELS: Final = frozenset({"apodex-1-1-deep-discover"})
 
 
 def strip_provider_prefix(model: str) -> str:
@@ -28,6 +29,10 @@ def is_deep_research_model(model: str) -> bool:
     return _DEEP_RESEARCH_MARKER in strip_provider_prefix(model)
 
 
+def is_responses_only_model(model: str) -> bool:
+    return strip_provider_prefix(model) in _RESPONSES_ONLY_MODELS
+
+
 def get_apodex_api_key(api_key: str | None = None) -> str | None:
     return api_key or get_secret_str("APODEX_API_KEY")
 
diff --git a/tests/test_litellm/llms/apodex/test_apodex_chat_transformation.py b/tests/test_litellm/llms/apodex/test_apodex_chat_transformation.py
index 2655a14aae7..7cfbefca047 100644
--- a/tests/test_litellm/llms/apodex/test_apodex_chat_transformation.py
+++ b/tests/test_litellm/llms/apodex/test_apodex_chat_transformation.py
@@ -167,8 +167,33 @@ class TestStreamDefault:
 
         assert captured["body"]["stream"] is False
 
+    def test_transform_does_not_mutate_optional_params(self):
+        config = _chat_config("apodex-1.1")
+        optional_params = config.map_openai_params(
+            non_default_params={}, optional_params={}, model="apodex-1.1", drop_params=False
+        )
+        original = optional_params.copy()
+
+        config.transform_request(
+            model="apodex-1.1",
+            messages=[{"role": "user", "content": "hi"}],
+            optional_params=optional_params,
+            litellm_params={"custom_llm_provider": "apodex"},
+            headers={},
+        )
+
+        assert optional_params == original
+
 
 class TestSupportedParams:
+    def test_responses_only_model_rejects_chat_completions(self):
+        with pytest.raises(litellm.BadRequestError, match="only available through /v1/responses"):
+            litellm.completion(
+                model="apodex/apodex-1-1-deep-discover",
+                messages=[{"role": "user", "content": "hi"}],
+                client=_client({}),
+            )
+
     def test_core_models_support_tools(self):
         supported = _chat_config("apodex-1.1").get_supported_openai_params("apodex-1.1")
         assert "tools" in supported