diff --git a/litellm/llms/a2a/chat/transformation.py b/litellm/llms/a2a/chat/transformation.py
index be3b5fea601..79208416f52 100644
--- a/litellm/llms/a2a/chat/transformation.py
+++ b/litellm/llms/a2a/chat/transformation.py
@@ -133,13 +133,13 @@ class A2AConfig(BaseConfig):
         return api_base, api_key, headers
 
     def get_supported_openai_params(self, model: str) -> list[str]:
-        """Return list of supported OpenAI parameters"""
-        return [
-            "stream",
-            "temperature",
-            "max_tokens",
-            "top_p",
-        ]
+        """Return list of supported OpenAI parameters.
+
+        Only ``stream`` is forwarded (map_openai_params maps nothing else onto the
+        A2A JSON-RPC payload). Declaring sampling params as supported used to drop
+        them silently; leaving them unsupported makes callers fail loudly instead.
+        """
+        return ["stream"]
 
     def map_openai_params(
         self,
diff --git a/tests/unit/llms/a2a/chat/test_a2a_chat_transformation.py b/tests/unit/llms/a2a/chat/test_a2a_chat_transformation.py
index 76bce26e2e0..8c64bacd6bb 100644
--- a/tests/unit/llms/a2a/chat/test_a2a_chat_transformation.py
+++ b/tests/unit/llms/a2a/chat/test_a2a_chat_transformation.py
@@ -226,3 +226,36 @@ def test_transform_response_reports_an_undecodable_body_as_an_agent_error():
 
     assert exc_info.value.status_code == 502
     assert exc_info.value.message.startswith("Failed to parse A2A response: ")
+
+
+def test_get_supported_openai_params_declares_only_stream():
+    """Sampling params are not mapped onto the A2A JSON-RPC payload, so the config
+    must not declare them as supported - declaring them used to drop them silently."""
+    assert A2AConfig().get_supported_openai_params(model="test-agent") == ["stream"]
+
+
+def test_sampling_params_fail_loudly_instead_of_dropping_silently():
+    """temperature/max_tokens/top_p are not forwarded to the agent; callers must get
+    a named error rather than a call that silently ignores their settings."""
+    from litellm.exceptions import UnsupportedParamsError
+    from litellm.utils import get_optional_params
+
+    for param in ("temperature", "max_tokens", "top_p"):
+        with pytest.raises(UnsupportedParamsError):
+            get_optional_params(model="test-agent", custom_llm_provider="a2a", **{param: 0.7})
+
+
+def test_drop_params_still_drops_unsupported_sampling_params():
+    """With drop_params set, unsupported sampling params are stripped and only the
+    supported stream flag survives."""
+    from litellm.utils import get_optional_params
+
+    result = get_optional_params(
+        model="test-agent",
+        custom_llm_provider="a2a",
+        temperature=0.7,
+        stream=True,
+        drop_params=True,
+    )
+    assert "temperature" not in result
+    assert result.get("stream") is True