fix: follow the redirect the detector's ingress answers with

app/adapters/detector_readiness.py

@@ -32,7 +32,12 @@ def http_probe(client: HttpClientLike, url: str) -> Callable[[], Awaitable[bool]
     """
 
     async def probe() -> bool:
-        return (await client.get(url)).status_code == 200
+        status = (await client.get(url)).status_code
+        if status != 200:
+            # A redirect, a rejection and a service still starting are all "not
+            # ready" but call for different responses, so the status is kept.
+            logger.info("detector_probe_status", extra={"context": {"status": status}})
+        return status == 200
 
     return probe
 

app/worker.py

@@ -136,7 +136,11 @@ async def main() -> None:
 
     # The first request also activates the detector, since it scales to zero,
     # so probing both starts it and establishes when it is usable.
-    http = httpx.AsyncClient(timeout=DETECTOR_PROBE_TIMEOUT_S)
+    # follow_redirects, because the detector's ingress refuses plain HTTP and
+    # answers with a redirect to HTTPS. A client that does not follow it sees a
+    # non-200 forever, and the redirect alone does not start an app scaled to
+    # zero, so the endpoint would never become reachable.
+    http = httpx.AsyncClient(timeout=DETECTOR_PROBE_TIMEOUT_S, follow_redirects=True)
     probe = http_probe(http, f"{settings.llm_guardrail_base_url.rstrip('/')}/models")
 
     async def detector_ready() -> bool:

tests/unit/test_detector_readiness.py

@@ -158,3 +158,39 @@ async def probe() -> bool:
 
     assert "detector_not_ready_yet" in events
     assert "detector_ready" in events
+
+
+@pytest.mark.asyncio
+async def test_a_probe_reports_the_status_it_received():
+    """ "Not ready" covers a redirect, a rejection and a service still starting,
+    which need different responses. The status is recorded so the logs say
+    which one it was."""
+    import logging
+
+    from app.adapters.detector_readiness import http_probe
+
+    events: list[dict] = []
+
+    class _Collect(logging.Handler):
+        def emit(self, record: logging.LogRecord) -> None:
+            events.append(getattr(record, "context", {}))
+
+    class _Response:
+        status_code = 307
+
+    class _Client:
+        async def get(self, url: str):
+            return _Response()
+
+    logger = logging.getLogger("screen")
+    handler = _Collect()
+    logger.addHandler(handler)
+    previous = logger.level
+    logger.setLevel(logging.INFO)
+    try:
+        assert not await http_probe(_Client(), "http://detector/v1/models")()
+    finally:
+        logger.removeHandler(handler)
+        logger.setLevel(previous)
+
+    assert any(c.get("status") == 307 for c in events)