feat(providers): support DeepSeek V4 vision

tests/providers/test_litellm_kwargs.py

@@ -368,6 +368,46 @@ async def test_deepseek_v4_pro_uses_responses_api() -> None:
     assert "include" not in call_kwargs
 
 
+@pytest.mark.asyncio
+async def test_deepseek_vision_uses_responses_api_with_image_input() -> None:
+    mock_chat = AsyncMock(return_value=_fake_chat_response())
+    mock_responses = AsyncMock(return_value=_fake_responses_response("vision response"))
+    content = [
+        {"type": "text", "text": "describe this image"},
+        {"type": "image_url", "image_url": {"url": "data:image/png;base64,AA=="}},
+    ]
+
+    with patch("nanobot.providers.openai_compat_provider.AsyncOpenAI") as mock_client_class:
+        client_instance = mock_client_class.return_value
+        client_instance.chat.completions.create = mock_chat
+        client_instance.responses.create = mock_responses
+
+        provider = OpenAICompatProvider(
+            api_key="sk-test-key",
+            default_model="deepseek-v4-flash-vision-exp",
+            spec=find_by_name("deepseek"),
+        )
+        result = await provider.chat(
+            messages=[{"role": "user", "content": content}],
+            model="deepseek-v4-flash-vision-exp",
+        )
+
+    assert result.content == "vision response"
+    mock_chat.assert_not_awaited()
+    call_kwargs = mock_responses.call_args.kwargs
+    assert call_kwargs["input"] == [{
+        "role": "user",
+        "content": [
+            {"type": "input_text", "text": "describe this image"},
+            {
+                "type": "input_image",
+                "image_url": "data:image/png;base64,AA==",
+                "detail": "auto",
+            },
+        ],
+    }]
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize(
     ("provider_name", "model"),
@@ -1557,6 +1597,33 @@ def test_deepseek_coerces_list_content_to_string() -> None:
     assert "world" in kw["messages"][0]["content"]
 
 
+def test_deepseek_vision_preserves_multimodal_content() -> None:
+    """DeepSeek's vision model requires OpenAI-compatible content blocks."""
+    spec = find_by_name("deepseek")
+    with patch("nanobot.providers.openai_compat_provider.AsyncOpenAI"):
+        p = OpenAICompatProvider(
+            api_key="k",
+            default_model="deepseek-v4-flash-vision-exp",
+            spec=spec,
+        )
+    content = [
+        {"type": "text", "text": "describe this image"},
+        {"type": "image_url", "image_url": {"url": "data:image/png;base64,AA=="}},
+    ]
+
+    kw = p._build_kwargs(
+        messages=[{"role": "user", "content": content}],
+        tools=None,
+        model="deepseek-v4-flash-vision-exp",
+        max_tokens=1024,
+        temperature=0.7,
+        reasoning_effort=None,
+        tool_choice=None,
+    )
+
+    assert kw["messages"][0]["content"] == content
+
+
 def test_non_deepseek_keeps_list_content() -> None:
     """Only DeepSeek should force string content; OpenAI-compatible providers keep blocks."""
     spec = find_by_name("openai")