diff --git a/litellm/llms/bedrock/chat/converse_transformation.py b/litellm/llms/bedrock/chat/converse_transformation.py
index d7ee15cedd7..617ce423d51 100644
--- a/litellm/llms/bedrock/chat/converse_transformation.py
+++ b/litellm/llms/bedrock/chat/converse_transformation.py
@@ -510,6 +510,18 @@ class AmazonConverseConfig(BaseConfig):
             or supports_reasoning(model=base_model, custom_llm_provider=self.custom_llm_provider)
         )
 
+    def _model_reasons_natively_and_rejects_request_param(self, model: str, base_model: str) -> bool:
+        """Whether the model reasons natively and rejects any reasoning request field on Converse.
+
+        The Converse mapping serializes ``thinking`` into ``additionalModelRequestFields`` in Anthropic's
+        shape and ``reasoning_effort`` into a provider-specific shape. DeepSeek reasons on its own and
+        returns a 400 when either field is sent, even though it advertises ``supports_reasoning``, so both
+        must be dropped for it. Every other model either accepts one of those shapes (Claude ``thinking``,
+        gpt-oss / Nova 2 ``reasoning_effort``) or is an opaque ARN we can't introspect, so we leave those
+        untouched rather than silently degrading reasoning.
+        """
+        return "deepseek" in model or "deepseek" in base_model
+
     def get_supported_openai_params(self, model: str) -> List[str]:
         from litellm.utils import supports_function_calling
 
@@ -857,7 +869,7 @@ class AmazonConverseConfig(BaseConfig):
         drop_params: bool,
     ) -> dict:
         is_thinking_enabled = self.is_thinking_enabled(non_default_params)
-        accepts_thinking_param = self._model_accepts_anthropic_thinking_param(
+        drop_reasoning_request_param = self._model_reasons_natively_and_rejects_request_param(
             model=model, base_model=BedrockModelInfo.get_base_model(model)
         )
 
@@ -909,7 +921,7 @@ class AmazonConverseConfig(BaseConfig):
                 optional_params["_parallel_tool_use_config"] = {
                     "tool_choice": {"disable_parallel_tool_use": disable_parallel}
                 }
-            if param == "thinking" and not accepts_thinking_param:
+            if param == "thinking" and drop_reasoning_request_param:
                 verbose_logger.debug(
                     "Dropping unsupported `thinking` param for Bedrock model=%s; it reasons natively and rejects it.",
                     model,
@@ -937,7 +949,7 @@ class AmazonConverseConfig(BaseConfig):
                         litellm.verbose_logger.warning(DROP_UNSUPPORTED_ADAPTIVE_THINKING_WARNING, model)
                 else:
                     optional_params["thinking"] = value
-            elif param == "reasoning_effort" and isinstance(value, str) and not accepts_thinking_param:
+            elif param == "reasoning_effort" and isinstance(value, str) and drop_reasoning_request_param:
                 verbose_logger.debug(
                     "Dropping unsupported `reasoning_effort` param for Bedrock model=%s; it reasons natively and rejects it.",
                     model,
diff --git a/tests/test_litellm/llms/bedrock/chat/test_converse_transformation.py b/tests/test_litellm/llms/bedrock/chat/test_converse_transformation.py
index 93455f00143..87a172f2409 100644
--- a/tests/test_litellm/llms/bedrock/chat/test_converse_transformation.py
+++ b/tests/test_litellm/llms/bedrock/chat/test_converse_transformation.py
@@ -633,6 +633,52 @@ def test_bedrock_deepseek_r1_reasoning_params_not_forwarded_by_map(param):
     assert request.get("additionalModelRequestFields") is None
 
 
+@pytest.mark.parametrize(
+    "model, param, value, kept_key",
+    [
+        (
+            "bedrock/us.anthropic.claude-opus-4-20250514-v1:0",
+            "thinking",
+            {"type": "enabled", "budget_tokens": 1024},
+            "thinking",
+        ),
+        (
+            "bedrock/arn:aws:bedrock:us-east-1:123456789012:application-inference-profile/abc123",
+            "thinking",
+            {"type": "enabled", "budget_tokens": 1024},
+            "thinking",
+        ),
+        (
+            "bedrock/openai.gpt-oss-safeguard-20b-1:0",
+            "reasoning_effort",
+            "high",
+            "reasoning_effort",
+        ),
+        (
+            "bedrock/us.amazon.nova-2-lite-v1:0",
+            "reasoning_effort",
+            "high",
+            "reasoningConfig",
+        ),
+    ],
+)
+def test_bedrock_non_deepseek_reasoning_params_preserved(model, param, value, kept_key):
+    """The DeepSeek leak fix must only drop reasoning request params for DeepSeek.
+
+    Claude behind an application-inference-profile ARN, gpt-oss-safeguard (absent from the
+    cost map so `supports_reasoning` is False), and Nova 2 all reason via a request param and
+    must keep it. Regression guard against gating the drop on a positive allowlist, which
+    silently degraded reasoning for anything the allowlist/ARN introspection missed."""
+    config = AmazonConverseConfig()
+    optional_params = config.map_openai_params(
+        non_default_params={param: value, "max_tokens": 100},
+        optional_params={},
+        model=model,
+        drop_params=False,
+    )
+    assert kept_key in optional_params
+
+
 def test_get_supported_openai_params_bedrock_converse():
     """
     Test that all documented bedrock converse models have the same set of supported openai params when using