diff --git a/tests/integration/contracts.json b/tests/integration/contracts.json
index d12e3ae4620..7a586f6b7a2 100644
--- a/tests/integration/contracts.json
+++ b/tests/integration/contracts.json
@@ -159,6 +159,9 @@
     "tests/integration/routing/test_redis_recovery.py::test_owned_redis_outage_recovers_requests_and_real_response_cache": [
       "other.routing.redis.owned_outage_recovers_serving_and_response_cache"
     ],
+    "tests/integration/providers/test_anthropic_advisor_wire.py::test_advisor_sub_call_reaches_the_router_deployment_with_its_key_instead_of_anthropic_unauthenticated": [
+      "providers.anthropic_messages_advisor.sub_call_uses_the_configured_advisor_deployment"
+    ],
     "tests/integration/providers/test_anthropic_wire.py::test_anthropic_tool_history_and_cache_tokens_keep_wire_and_accounting_contracts": [
       "other.provider_wire.anthropic.tool_history_system_cache_and_internal_fields",
       "quota_management.spend_tracking.cache_tokens.disjoint_classes_use_explicit_rates"
diff --git a/tests/integration/providers/test_anthropic_advisor_wire.py b/tests/integration/providers/test_anthropic_advisor_wire.py
new file mode 100644
index 00000000000..77fa27cd2a9
--- /dev/null
+++ b/tests/integration/providers/test_anthropic_advisor_wire.py
@@ -0,0 +1,113 @@
+import json
+import uuid
+from typing import Final
+
+import pytest
+from integration._support.client import Gateway
+from integration._support.wire import Reply, Request, wire_server
+
+_ADVISOR_KEY: Final = "synthetic-advisor-key"
+_QUESTION: Final = "which index should this query use"
+_ADVICE: Final = "use the composite index on (tenant_id, created_at)"
+_FINAL_ANSWER: Final = "done, the composite index is the right one"
+
+
+_ADVISOR_CALL_MESSAGE: Final = {
+    "role": "assistant",
+    "content": None,
+    "tool_calls": [
+        {
+            "id": "advisor-call",
+            "type": "function",
+            "function": {"name": "advisor", "arguments": json.dumps({"question": _QUESTION})},
+        }
+    ],
+}
+_FINAL_MESSAGE: Final = {"role": "assistant", "content": _FINAL_ANSWER}
+
+
+def _chat_completion(identity: str, message: dict[str, object], finish_reason: str) -> Reply:
+    return Reply(
+        body=json.dumps(
+            {
+                "id": f"chatcmpl-{identity}",
+                "object": "chat.completion",
+                "created": 1,
+                "model": "llama-3.3-70b-versatile",
+                "choices": [{"index": 0, "message": message, "finish_reason": finish_reason}],
+                "usage": {"prompt_tokens": 10, "completion_tokens": 4, "total_tokens": 14},
+            }
+        ).encode()
+    )
+
+
+def _executor_reply(body: dict[str, object], identity: str) -> Reply:
+    messages: Final = body["messages"]
+    assert isinstance(messages, list)
+    if any(message.get("role") == "tool" for message in messages):
+        assert messages[-1]["content"] == _ADVICE
+        return _chat_completion(identity, _FINAL_MESSAGE, "stop")
+    tools: Final = body["tools"]
+    assert isinstance(tools, list)
+    assert tools[0]["function"]["name"] == "advisor"
+    return _chat_completion(identity, _ADVISOR_CALL_MESSAGE, "tool_calls")
+
+
+@pytest.mark.covers("providers.anthropic_messages_advisor.sub_call_uses_the_configured_advisor_deployment")
+def test_advisor_sub_call_reaches_the_router_deployment_with_its_key_instead_of_anthropic_unauthenticated(
+    gateway: Gateway,
+) -> None:
+    identity: Final = "advisor-wire-" + uuid.uuid4().hex
+
+    def respond(request: Request) -> Reply:
+        body: Final = json.loads(request.body)
+        if request.target == "/v1/chat/completions":
+            assert request.headers["authorization"] == "Bearer integration-provider-key"
+            return _executor_reply(body, identity)
+        assert request.target == "/v1/messages"
+        assert request.headers["x-api-key"] == _ADVISOR_KEY
+        assert body["model"] == "claude-opus-4-1-20250805"
+        assert body["messages"] == [
+            {"role": "user", "content": "please plan the migration"},
+            {"role": "user", "content": _QUESTION},
+        ]
+        assert "tools" not in body
+        return Reply(
+            body=json.dumps(
+                {
+                    "id": f"msg-{identity}",
+                    "type": "message",
+                    "role": "assistant",
+                    "model": "claude-opus-4-1-20250805",
+                    "content": [{"type": "text", "text": _ADVICE}],
+                    "stop_reason": "end_turn",
+                    "stop_sequence": None,
+                    "usage": {"input_tokens": 12, "output_tokens": 6},
+                }
+            ).encode()
+        )
+
+    with wire_server(respond) as wire, gateway.scenario() as scenario:
+        executor: Final = scenario.model(model="hosted_vllm/llama-3.3-70b", api_base=wire.url + "/v1")
+        advisor: Final = scenario.model(
+            model="anthropic/claude-opus-4-1-20250805", api_base=wire.url, api_key=_ADVISOR_KEY
+        )
+        response: Final = gateway.request(
+            "POST",
+            "/v1/messages",
+            {
+                "model": executor,
+                "max_tokens": 64,
+                "messages": [{"role": "user", "content": "please plan the migration"}],
+                "tools": [{"type": "advisor_20260301", "name": "advisor", "model": advisor}],
+            },
+        )
+        assert response.status_code == 200, response.text
+        body: Final = response.json()
+        assert body["content"] == [{"type": "text", "text": _FINAL_ANSWER}], response.text
+        assert body["stop_reason"] == "end_turn", response.text
+        assert [request.target for request in wire.drain()] == [
+            "/v1/chat/completions",
+            "/v1/messages",
+            "/v1/chat/completions",
+        ]