diff --git a/src/main.py b/src/main.py
index 13f74da..9919996 100644
--- a/src/main.py
+++ b/src/main.py
@@ -22,6 +22,10 @@ FRONTEND_DIR = Path(__file__).resolve().parent.parent / "frontend"
 class ContextPayloadError(ValueError):
     """Raised when Gitea returns a structurally invalid context payload."""
 
+
+class ReadinessPayloadError(ValueError):
+    """Raised when Gitea returns a structurally invalid readiness payload."""
+
 app.add_middleware(
     CORSMiddleware,
     allow_origins=["*"],
@@ -56,13 +60,19 @@ async def readiness():
             current_user(), timeout=READINESS_TIMEOUT_SECONDS
         )
         if not isinstance(user, dict) or not user.get("login"):
-            raise ValueError("Gitea current-user response did not include a login")
+            raise ReadinessPayloadError(
+                "Gitea current-user response did not include a login"
+            )
     except Exception as exc:
         timed_out = isinstance(exc, TimeoutError)
         error_message = (
             f"Gitea readiness check timed out after {READINESS_TIMEOUT_SECONDS:g}s"
             if timed_out
-            else str(exc)
+            else (
+                str(exc)
+                if isinstance(exc, ReadinessPayloadError)
+                else "Gitea readiness check is temporarily unavailable"
+            )
         )
         return JSONResponse(
             {
diff --git a/tests/test_health.py b/tests/test_health.py
index db465d8..d8c5a97 100644
--- a/tests/test_health.py
+++ b/tests/test_health.py
@@ -29,17 +29,21 @@ async def test_readiness_endpoint_reports_connected_gitea_user(monkeypatch):
 
 
 @pytest.mark.anyio
-async def test_readiness_endpoint_returns_503_when_gitea_is_unavailable(monkeypatch):
+async def test_readiness_endpoint_hides_unexpected_upstream_error_details(monkeypatch):
     async def unavailable_user():
-        raise RuntimeError("connection refused")
+        raise RuntimeError("secret internal upstream detail")
 
     monkeypatch.setattr(main, "current_user", unavailable_user)
 
     response = await main.readiness()
 
     assert response.status_code == 503
-    assert b'"status":"not_ready"' in response.body
-    assert b'"error":"connection refused"' in response.body
+    assert json.loads(response.body) == {
+        "status": "not_ready",
+        "service": "stackchain-dashboard",
+        "error": "Gitea readiness check is temporarily unavailable",
+    }
+    assert b"secret internal upstream detail" not in response.body
 
 
 @pytest.mark.anyio