test(integration): deepseek vision image content list reaches the provider unchanged (Pylon #7729)

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

tests/integration/contracts.json

@@ -223,6 +223,9 @@
     "tests/integration/providers/test_xiaomi_mimo_wire.py::test_xiaomi_mimo_tool_call_is_forwarded_and_returned": [
       "other.provider_wire.xiaomi_mimo.tool_call_survives_translation"
     ],
+    "tests/integration/providers/test_deepseek_vision_wire.py::test_deepseek_vision_forwards_image_url_content_list_instead_of_collapsing_to_text": [
+      "other.provider_wire.deepseek.vision_image_content_list_reaches_provider"
+    ],
     "tests/integration/providers/test_fal_ai_video_wire.py::test_fal_h3_video_create_uses_canonical_body_and_status_path": [
       "other.provider_wire.fal_ai.video_queue_create_status_and_content_download"
     ],

tests/integration/providers/test_deepseek_vision_wire.py

@@ -0,0 +1,40 @@
+from typing import Final
+
+import httpx
+import pytest
+from pydantic import JsonValue
+
+from tests.integration._support.client import JSON_OBJECT, Gateway, object_value
+
+_VISION_MODEL: Final = "deepseek-v4-flash-vision-exp"
+_API_KEY: Final = "synthetic-deepseek-key"
+_VISION_CONTENT: Final[JsonValue] = [
+    {"type": "text", "text": "what is in this image?"},
+    {"type": "image_url", "image_url": {"url": "https://example.com/pic.png"}},
+]
+
+
+@pytest.mark.covers("other.provider_wire.deepseek.vision_image_content_list_reaches_provider")
+def test_deepseek_vision_forwards_image_url_content_list_instead_of_collapsing_to_text(gateway: Gateway) -> None:
+    with gateway.scenario() as scenario, httpx.Client(base_url=gateway.upstream_url, trust_env=False) as upstream:
+        upstream.get("/__observations").raise_for_status()
+        model: Final = scenario.model(
+            model=f"deepseek/{_VISION_MODEL}",
+            api_key=_API_KEY,
+            model_info={"mode": "chat", "supports_vision": True},
+        )
+        response: Final = gateway.request(
+            "POST",
+            "/v1/chat/completions",
+            {"model": model, "messages": [{"role": "user", "content": _VISION_CONTENT}]},
+        )
+        assert response.status_code == 200, response.text
+        observations: Final = JSON_OBJECT.validate_json(upstream.get("/__observations").content)["requests"]
+        assert isinstance(observations, list)
+        assert len(observations) == 1, response.text
+        observed: Final = object_value(observations[0])
+        assert observed["path"] == "/v1/chat/completions", response.text
+        assert observed["authorization"] == f"Bearer {_API_KEY}", response.text
+        body: Final = object_value(observed["body"])
+        assert body["model"] == _VISION_MODEL, response.text
+        assert body["messages"] == [{"role": "user", "content": _VISION_CONTENT}], response.text