diff --git a/tests/sdk/llm/test_llm_attr_forwarding.py b/tests/sdk/llm/test_llm_attr_forwarding.py
new file mode 100644
index 0000000000..2dea79457c
--- /dev/null
+++ b/tests/sdk/llm/test_llm_attr_forwarding.py
@@ -0,0 +1,73 @@
+from __future__ import annotations
+
+from unittest.mock import patch
+
+from pydantic import SecretStr
+
+from openhands.sdk.llm import LLM, Message, TextContent
+from tests.conftest import create_mock_litellm_response
+
+
+@patch("openhands.sdk.llm.llm.litellm_completion")
+def test_all_config_attrs_are_forwarded_to_litellm_completion(mock_completion):
+    """Verify LLM forwards key attributes to litellm.completion.
+
+    This covers both sampling options managed by select_chat_options
+    (temperature/top_p/top_k, max tokens) and transport-level options
+    not handled there (base_url, api_version, drop_params, seed,
+    custom_llm_provider). If any are not forwarded, the test fails.
+    """
+    mock_completion.return_value = create_mock_litellm_response("ok")
+
+    llm = LLM(
+        model="gpt-4o",  # non-reasoning path keeps sampling params present
+        api_key=SecretStr("sk-test-123"),
+        base_url="https://example.com/v1",
+        api_version="2024-01-01",
+        custom_llm_provider="my-provider",
+        timeout=42,
+        drop_params=False,
+        seed=1234,
+        temperature=0.5,
+        top_p=0.8,
+        top_k=5,
+        max_output_tokens=99,
+        usage_id="forwarding-test",
+    )
+
+    _ = llm.completion(
+        messages=[Message(role="user", content=[TextContent(text="hi")])]
+    )
+
+    # Collect the actual kwargs forwarded to litellm.completion
+    assert mock_completion.called, "Expected litellm.completion to be called"
+    called_kwargs = mock_completion.call_args.kwargs
+
+    # Expectations: direct passthrough (not via select_chat_options)
+    assert called_kwargs.get("model") == "gpt-4o"
+    assert called_kwargs.get("api_key") == "sk-test-123"
+    assert called_kwargs.get("base_url") == "https://example.com/v1"
+    assert called_kwargs.get("api_version") == "2024-01-01"
+    assert called_kwargs.get("timeout") == 42
+    assert called_kwargs.get("drop_params") is False
+    assert called_kwargs.get("seed") == 1234
+
+    # Expectations: values that flow through select_chat_options
+    # - top_k/top_p/temperature should be present as-is for non-reasoning models
+    assert called_kwargs.get("top_k") == 5, "Expected top_k to be forwarded"
+    assert called_kwargs.get("top_p") == 0.8, "Expected top_p to be forwarded"
+    assert called_kwargs.get("temperature") == 0.5, (
+        "Expected temperature to be forwarded"
+    )
+
+    # - max_output_tokens is normalized to `max_completion_tokens` for OpenAI chat
+    #   (Azure uses `max_tokens`, but this test uses non-Azure model id)
+    assert called_kwargs.get("max_completion_tokens") == 99, (
+        "Expected max_output_tokens -> max_completion_tokens forwarding"
+    )
+
+    # Known bug: custom_llm_provider not forwarded; check this last so it doesn't
+    # hide earlier failures
+    assert called_kwargs.get("custom_llm_provider") == "my-provider", (
+        "custom_llm_provider was not forwarded"
+    )
diff --git a/tests/sdk/llm/test_llm_responses_attr_forwarding.py b/tests/sdk/llm/test_llm_responses_attr_forwarding.py
new file mode 100644
index 0000000000..ecaeff6f67
--- /dev/null
+++ b/tests/sdk/llm/test_llm_responses_attr_forwarding.py
@@ -0,0 +1,92 @@
+from __future__ import annotations
+
+from unittest.mock import patch
+
+from pydantic import SecretStr
+
+from openhands.sdk.llm import LLM, Message, TextContent
+
+
+@patch("openhands.sdk.llm.llm.litellm_responses")
+def test_responses_api_forwards_all_relevant_attrs(mock_responses):
+    """Ensure LLM.responses forwards key attributes to LiteLLM Responses API.
+
+    This covers both:
+    - transport-level options not handled by select_responses_options
+      (model, api_key, api_base/base_url, api_version, timeout, drop_params, seed)
+    - responses options normalized by select_responses_options
+      (temperature, tool_choice, include, store, reasoning, max_output_tokens)
+
+    The known gap custom_llm_provider is asserted at the end to avoid masking
+    any other potential failures.
+    """
+
+    # Return a minimal valid ResponsesAPIResponse to let the call path complete
+    # and avoid exceptions before our assertions.
+    from litellm.types.llms.openai import ResponsesAPIResponse
+
+    mock_responses.return_value = ResponsesAPIResponse(
+        id="resp_test_1",
+        created_at=1234567890,
+        output=[],
+    )
+
+    llm = LLM(
+        # Choose a model that triggers the Responses API path per model_features
+        # See RESPONSES_API_PATTERNS in model_features.py (e.g., 'gpt-5*')
+        model="gpt-5-mini",
+        api_key=SecretStr("sk-test-456"),
+        base_url="https://example.com/v1",
+        api_version="2024-01-01",
+        custom_llm_provider="my-provider",
+        timeout=7,
+        drop_params=False,
+        seed=4321,
+        max_output_tokens=123,
+        enable_encrypted_reasoning=True,  # ensures include carries encrypted content
+        usage_id="responses-forwarding",
+    )
+
+    _ = llm.responses(
+        messages=[
+            Message(role="system", content=[TextContent(text="You are helpful")]),
+            Message(role="user", content=[TextContent(text="hi")]),
+        ]
+    )
+
+    assert mock_responses.called, "Expected litellm.responses to be called"
+    called_kwargs = mock_responses.call_args.kwargs
+
+    # Transport-level passthrough
+    assert called_kwargs.get("model") == "gpt-5-mini"
+    assert called_kwargs.get("api_key") == "sk-test-456"
+    # responses() uses api_base for base URL
+    assert called_kwargs.get("api_base") == "https://example.com/v1"
+    assert called_kwargs.get("api_version") == "2024-01-01"
+    assert called_kwargs.get("timeout") == 7
+    assert called_kwargs.get("drop_params") is False
+    assert called_kwargs.get("seed") == 4321
+
+    # Responses path options
+    assert called_kwargs.get("temperature") == 1.0
+    assert called_kwargs.get("tool_choice") == "auto"
+    assert called_kwargs.get("input") is not None
+    assert called_kwargs.get("instructions") is not None
+    # store defaults to False unless provided
+    assert called_kwargs.get("store") is False
+    # include should contain encrypted reasoning content when store=False
+    include = called_kwargs.get("include") or []
+    assert "reasoning.encrypted_content" in include
+    # reasoning payload present with effort derived from llm
+    reasoning = called_kwargs.get("reasoning") or {}
+    assert reasoning.get("effort") in {"low", "medium", "high", "none"}
+    assert "summary" in reasoning
+
+    # max_output_tokens should be forwarded directly on Responses path
+    assert called_kwargs.get("max_output_tokens") == 123
+
+    # Known bug: custom_llm_provider not forwarded; check this last so it doesn't
+    # hide earlier failures
+    assert called_kwargs.get("custom_llm_provider") == "my-provider", (
+        "custom_llm_provider was not forwarded in Responses API call"
+    )