test(integration): config deployment dropped by a stale boot cost map is restored after reload (Pylon #7564)

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

tests/integration/contracts.json

@@ -171,6 +171,9 @@
     "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/routing/test_stale_cost_map_boot.py::test_config_deployment_dropped_by_stale_boot_cost_map_is_restored_after_reload": [
+      "other.routing.cost_map.config_deployment_dropped_by_stale_boot_map_is_restored_after_reload"
+    ],
     "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"

tests/integration/routing/test_stale_cost_map_boot.py

@@ -0,0 +1,84 @@
+import itertools
+import json
+import uuid
+from pathlib import Path
+from typing import Final
+
+import httpx
+import pytest
+from integration._support.client import Gateway, eventually
+from integration._support.process import owned_proxy
+from integration._support.wire import Reply, Request, wire_server
+
+
+def _proxy_config(directory: Path, model: str, upstream_url: str) -> Path:
+    config: Final = directory / "stale_cost_map_config.yaml"
+    config.write_text(
+        json.dumps(
+            {
+                "model_list": [
+                    {
+                        "model_name": model,
+                        "litellm_params": {"model": model, "api_base": upstream_url + "/v1", "api_key": "sk-upstream"},
+                    }
+                ],
+                "general_settings": {
+                    "master_key": "os.environ/LITELLM_MASTER_KEY",
+                    "database_url": "os.environ/DATABASE_URL",
+                    "store_model_in_db": True,
+                },
+                "router_settings": {"disable_cooldowns": True},
+            }
+        )
+    )
+    return config
+
+
+@pytest.mark.covers("other.routing.cost_map.config_deployment_dropped_by_stale_boot_map_is_restored_after_reload")
+def test_config_deployment_dropped_by_stale_boot_cost_map_is_restored_after_reload(
+    gateway: Gateway, tmp_path: Path
+) -> None:
+    model: Final = "integration-fresh-" + uuid.uuid4().hex
+    remote_map: Final = json.dumps(
+        {model: {"litellm_provider": "openai", "mode": "chat", "input_cost_per_token": 0, "output_cost_per_token": 0}}
+    ).encode()
+    fetches: Final = itertools.count(1)
+
+    def respond(request: Request) -> Reply:
+        assert request.target == "/model_prices.json", request
+        return Reply(status=503, body=b"{}") if next(fetches) == 1 else Reply(body=remote_map)
+
+    overrides: Final = {"MODEL_COST_MAP_MIN_MODEL_COUNT": "1", "MODEL_COST_MAP_MAX_SHRINK_RATIO": "0"}
+    with (
+        wire_server(respond) as peer,
+        httpx.Client(base_url=gateway.upstream_url, timeout=5, trust_env=False) as upstream,
+    ):
+        config: Final = _proxy_config(tmp_path, model, gateway.upstream_url)
+        with owned_proxy(
+            gateway,
+            tmp_path,
+            {**overrides, "LITELLM_MODEL_COST_MAP_URL": peer.url + "/model_prices.json"},
+            config=config,
+            remove_environment=("LITELLM_LOCAL_MODEL_COST_MAP",),
+        ) as candidate:
+            reload: Final = candidate.request("POST", "/reload/model_cost_map")
+            assert reload.status_code == 200, reload.text
+            eventually(
+                lambda: tuple(str(entry["id"]) for entry in candidate.get("/v1/models")["data"]),
+                lambda served: model in served,
+                seconds=30,
+            )
+            upstream.get("/__observations").raise_for_status()
+            response: Final = candidate.request(
+                "POST",
+                "/v1/chat/completions",
+                {"model": model, "messages": [{"role": "user", "content": "stale cost map control"}]},
+            )
+            assert response.status_code == 200, response.text
+            assert upstream.get("/__observations").json()["requests"] == [
+                {
+                    "path": "/v1/chat/completions",
+                    "authorization": "Bearer sk-upstream",
+                    "body": {"model": model, "messages": [{"role": "user", "content": "stale cost map control"}]},
+                }
+            ]