diff --git a/app/ovirt/common.py b/app/ovirt/common.py
new file mode 100644
index 0000000..2e327ba
--- /dev/null
+++ b/app/ovirt/common.py
@@ -0,0 +1,43 @@
+"""Shared oVirt Engine helpers (existence checks, native NotFound faults)."""
+
+from __future__ import annotations
+
+from typing import Any
+
+from asyncpg import Connection
+
+from app.ovirt.errors import OVirtError
+
+
+def no_such(kind: str, entity_id: str) -> OVirtError:
+    """Engine-shaped 404 with the bad id in the detail (never an HTML page)."""
+
+    return OVirtError(
+        "NotFound",
+        f"No such {kind} ('{entity_id}')",
+        status_code=404,
+    )
+
+
+async def require_host(conn: Connection, host_id: str) -> Any:
+    row = await conn.fetchrow("SELECT * FROM ov_hosts WHERE id=$1::uuid", host_id)
+    if row is None:
+        raise no_such("host", host_id)
+    return row
+
+
+async def require_datacenter(conn: Connection, datacenter_id: str) -> Any:
+    row = await conn.fetchrow(
+        "SELECT * FROM ov_datacenters WHERE id=$1::uuid",
+        datacenter_id,
+    )
+    if row is None:
+        raise no_such("datacenter", datacenter_id)
+    return row
+
+
+async def require_cluster(conn: Connection, cluster_id: str) -> Any:
+    row = await conn.fetchrow("SELECT * FROM ov_clusters WHERE id=$1::uuid", cluster_id)
+    if row is None:
+        raise no_such("cluster", cluster_id)
+    return row
diff --git a/app/ovirt/repr.py b/app/ovirt/repr.py
index 874e6e2..eae0d74 100644
--- a/app/ovirt/repr.py
+++ b/app/ovirt/repr.py
@@ -244,11 +244,17 @@ def user_entity(row: Any) -> dict[str, Any]:
     }
 
 
-def generic_entity(collection: str, element: str, row: Any) -> dict[str, Any]:
+def generic_entity(
+    collection: str,
+    element: str,
+    row: Any,
+    *,
+    entity_id: str | None = None,
+) -> dict[str, Any]:
     if row is None:
-        from app.ovirt.errors import OVirtError
+        from app.ovirt.common import no_such
 
-        raise OVirtError("NotFound", f"{element} not found", status_code=404)
+        raise no_such(element, entity_id or "unknown")
     oid = str(row["id"])
     data = _data(row)
     entity = {
diff --git a/app/ovirt/routes/engine.py b/app/ovirt/routes/engine.py
index 8ad3769..b812e6a 100644
--- a/app/ovirt/routes/engine.py
+++ b/app/ovirt/routes/engine.py
@@ -11,6 +11,7 @@ from uuid import uuid4
 from asyncpg import Connection
 from fastapi import APIRouter, Request, Response
 
+from app.ovirt.common import no_such, require_cluster, require_datacenter, require_host
 from app.ovirt.deps import get_db, require_auth
 from app.ovirt.errors import OVirtError
 from app.ovirt.jobs import create_job, respond_action
@@ -170,7 +171,7 @@ async def handle_engine_request(request: Request) -> Response:
         raise
     except (TypeError, AttributeError) as exc:
         # Missing rows often crash in *_entity builders (row is None).
-        raise OVirtError("NotFound", "resource not found", status_code=404) from exc
+        raise no_such("resource", rel or "/") from exc
     except Exception as exc:
         # Integrity / UUID parse failures from coverage mutations → client error.
         name = type(exc).__name__
@@ -1045,13 +1046,12 @@ async def _handle_hosts(
         row = await conn.fetchrow("SELECT * FROM ov_hosts WHERE id=$1", hid)
         return respond(request, element="host", data=host_entity(row), status_code=201)
     host_id = parts[1]
-    row = await conn.fetchrow("SELECT * FROM ov_hosts WHERE id=$1::uuid", host_id)
     if len(parts) == 2:
         if method == "GET":
-            if row is None:
-                raise OVirtError("NotFound", "host not found", status_code=404)
+            row = await require_host(conn, host_id)
             return respond(request, element="host", data=host_entity(row))
         if method == "PUT":
+            await require_host(conn, host_id)
             body = unwrap_entity(payload, "host")
             await conn.execute(
                 "UPDATE ov_hosts SET name=COALESCE($2,name), address=COALESCE($3,address), updated_at=now() WHERE id=$1::uuid",
@@ -1059,11 +1059,15 @@ async def _handle_hosts(
                 body.get("name"),
                 body.get("address"),
             )
-            row = await conn.fetchrow("SELECT * FROM ov_hosts WHERE id=$1::uuid", host_id)
+            row = await require_host(conn, host_id)
             return respond(request, element="host", data=host_entity(row))
         if method == "DELETE":
+            await require_host(conn, host_id)
             await conn.execute("DELETE FROM ov_hosts WHERE id=$1::uuid", host_id)
             return Response(status_code=200)
+    row = await conn.fetchrow("SELECT * FROM ov_hosts WHERE id=$1::uuid", host_id)
+    if row is None:
+        raise no_such("host", host_id)
     if len(parts) == 3 and method == "POST":
         action = parts[2].lower()
         status_map = await option_json(conn, OPT_HOST_ACTION_STATUS_MAP)
@@ -1129,11 +1133,10 @@ async def _handle_datacenters(
         return respond(request, element="data_center", data=datacenter_entity(row), status_code=201)
     dc_id = parts[1]
     if len(parts) == 2 and method == "GET":
-        row = await conn.fetchrow("SELECT * FROM ov_datacenters WHERE id=$1::uuid", dc_id)
-        if row is None:
-            raise OVirtError("NotFound", "datacenter not found", status_code=404)
+        row = await require_datacenter(conn, dc_id)
         return respond(request, element="data_center", data=datacenter_entity(row))
     if len(parts) == 2 and method == "PUT":
+        await require_datacenter(conn, dc_id)
         body = unwrap_entity(payload, "data_center")
         await conn.execute(
             "UPDATE ov_datacenters SET name=COALESCE($2,name), description=COALESCE($3,description), updated_at=now() WHERE id=$1::uuid",
@@ -1141,9 +1144,10 @@ async def _handle_datacenters(
             body.get("name"),
             body.get("description"),
         )
-        row = await conn.fetchrow("SELECT * FROM ov_datacenters WHERE id=$1::uuid", dc_id)
+        row = await require_datacenter(conn, dc_id)
         return respond(request, element="data_center", data=datacenter_entity(row))
     if len(parts) == 2 and method == "DELETE":
+        await require_datacenter(conn, dc_id)
         await conn.execute("DELETE FROM ov_datacenters WHERE id=$1::uuid", dc_id)
         return Response(status_code=200)
     if len(parts) == 3 and method == "POST" and parts[2] == "cleanfinishedtasks":
@@ -1225,9 +1229,7 @@ async def _dc_clusters(
     request: Request, conn: Connection, method: str, parts: list[str], payload: dict[str, Any]
 ) -> Response:
     dc_id = parts[1]
-    dc = await conn.fetchrow("SELECT id FROM ov_datacenters WHERE id=$1::uuid", dc_id)
-    if dc is None:
-        raise OVirtError("NotFound", "datacenter not found", status_code=404)
+    await require_datacenter(conn, dc_id)
     if len(parts) == 3 and method == "GET":
         rows = await conn.fetch(
             "SELECT * FROM ov_clusters WHERE datacenter_id=$1::uuid ORDER BY name", dc_id
@@ -1263,7 +1265,7 @@ async def _dc_clusters(
             dc_id,
         )
         if row is None:
-            raise OVirtError("NotFound", "cluster not found", status_code=404)
+            raise no_such("cluster", parts[3])
         return respond(request, element="cluster", data=cluster_entity(row))
     if len(parts) == 4 and method == "DELETE":
         await conn.execute(
@@ -1279,9 +1281,7 @@ async def _dc_networks(
     request: Request, conn: Connection, method: str, parts: list[str], payload: dict[str, Any]
 ) -> Response:
     dc_id = parts[1]
-    dc = await conn.fetchrow("SELECT id FROM ov_datacenters WHERE id=$1::uuid", dc_id)
-    if dc is None:
-        raise OVirtError("NotFound", "datacenter not found", status_code=404)
+    await require_datacenter(conn, dc_id)
     if len(parts) == 3 and method == "GET":
         rows = await conn.fetch(
             "SELECT * FROM ov_networks WHERE datacenter_id=$1::uuid ORDER BY name", dc_id
@@ -1427,11 +1427,10 @@ async def _handle_clusters(
         return respond(request, element="cluster", data=cluster_entity(row), status_code=201)
     cluster_id = parts[1]
     if len(parts) == 2 and method == "GET":
-        row = await conn.fetchrow("SELECT * FROM ov_clusters WHERE id=$1::uuid", cluster_id)
-        if row is None:
-            raise OVirtError("NotFound", "cluster not found", status_code=404)
+        row = await require_cluster(conn, cluster_id)
         return respond(request, element="cluster", data=cluster_entity(row))
     if len(parts) == 2 and method == "PUT":
+        await require_cluster(conn, cluster_id)
         body = unwrap_entity(payload, "cluster")
         await conn.execute(
             "UPDATE ov_clusters SET name=COALESCE($2,name), description=COALESCE($3,description) WHERE id=$1::uuid",
@@ -1439,9 +1438,10 @@ async def _handle_clusters(
             body.get("name"),
             body.get("description"),
         )
-        row = await conn.fetchrow("SELECT * FROM ov_clusters WHERE id=$1::uuid", cluster_id)
+        row = await require_cluster(conn, cluster_id)
         return respond(request, element="cluster", data=cluster_entity(row))
     if len(parts) == 2 and method == "DELETE":
+        await require_cluster(conn, cluster_id)
         await conn.execute("DELETE FROM ov_clusters WHERE id=$1::uuid", cluster_id)
         return Response(status_code=200)
     if len(parts) >= 3 and parts[2] == "affinitygroups":
@@ -1542,9 +1542,7 @@ async def _cluster_networks(
 
     del payload
     cluster_id = parts[1]
-    cluster = await conn.fetchrow("SELECT * FROM ov_clusters WHERE id=$1::uuid", cluster_id)
-    if cluster is None:
-        raise OVirtError("NotFound", "cluster not found", status_code=404)
+    cluster = await require_cluster(conn, cluster_id)
     dc_id = cluster["datacenter_id"]
     if len(parts) == 3 and method == "GET":
         rows = await conn.fetch(
diff --git a/app/ovirt/schema_engine.py b/app/ovirt/schema_engine.py
index 7079bf2..511b731 100644
--- a/app/ovirt/schema_engine.py
+++ b/app/ovirt/schema_engine.py
@@ -123,11 +123,19 @@ async def handle_generic(
         )
         if method == "GET":
             if row is None:
-                raise OVirtError("NotFound", f"{element} not found", status_code=404)
-            return respond(request, element=element, data=generic_entity(collection, element, row))
+                from app.ovirt.common import no_such
+
+                raise no_such(element, oid)
+            return respond(
+                request,
+                element=element,
+                data=generic_entity(collection, element, row, entity_id=oid),
+            )
         if method == "PUT":
             if row is None:
-                raise OVirtError("NotFound", f"{element} not found", status_code=404)
+                from app.ovirt.common import no_such
+
+                raise no_such(element, oid)
             body = unwrap_entity(payload, element)
             data = dict(json.loads(row["data"]) if isinstance(row["data"], str) else row["data"] or {})
             data.update(body)
@@ -330,8 +338,10 @@ async def handle_subcollection(
                 parent_id,
             )
             if row is None:
-                raise OVirtError("NotFound", f"{element} not found", status_code=404)
-            data = generic_entity(sub, element, row)
+                from app.ovirt.common import no_such
+
+                raise no_such(element, oid)
+            data = generic_entity(sub, element, row, entity_id=oid)
             data["href"] = f"/ovirt-engine/api/{parent_collection}/{parent_id}/{sub}/{oid}"
             return respond(request, element=element, data=data)
         if method == "DELETE":
diff --git a/app/web/index.html b/app/web/index.html
index 8bcf1f2..58e22bf 100644
--- a/app/web/index.html
+++ b/app/web/index.html
@@ -4740,12 +4740,7 @@
         if (!res.ok) throw new Error("session expired");
         persistAuth();
       } catch {
-        state.ticket = null;
-        state.csrf = null;
-        state.username = null;
-        state.project = null;
-        localStorage.removeItem(LS_AUTH);
-        setAuth(false);
+        clearSession({ closePanel: false });
       }
     }
 
@@ -5994,6 +5989,23 @@
       }
     }
 
+    function clearSession(options = {}) {
+      const { toastMessage = null, toastKind = "info", closePanel = true } = options;
+      state.ticket = null;
+      state.csrf = null;
+      state.username = null;
+      state.project = null;
+      document.cookie = "JSESSIONID=; Max-Age=0; path=/; SameSite=Strict";
+      document.cookie = "ovirt_token=; Max-Age=0; path=/; SameSite=Strict";
+      try { localStorage.removeItem(LS_AUTH); } catch {}
+      try { sessionStorage.removeItem(LS_AUTH); } catch {}
+      setAuth(false);
+      persistAuth();
+      if (closePanel) closeAuthPanel();
+      resetClusterStats("—");
+      if (toastMessage) toast(toastMessage, toastKind);
+    }
+
     function logout() {
       const token = state.ticket;
       if (token) {
@@ -6002,15 +6014,15 @@
           headers: { Authorization: `Bearer ${token}` },
         }).catch(() => {});
       }
-      state.ticket = null;
-      state.csrf = null;
-      state.username = null;
-      state.project = null;
-      setAuth(false);
-      persistAuth();
-      closeAuthPanel();
-      resetClusterStats("—");
-      toast("Signed out", "info");
+      clearSession({ toastMessage: "Signed out", toastKind: "info" });
+    }
+
+    function expireSession() {
+      clearSession({
+        toastMessage: "Session expired — sign in again",
+        toastKind: "warn",
+        closePanel: false,
+      });
     }
 
     function updateStatusBadge(status) {
@@ -6087,6 +6099,9 @@
       const text = await res.text();
       let parsed;
       try { parsed = JSON.parse(text); } catch { parsed = text; }
+      if (res.status === 401 && (state.ticket || state.username)) {
+        expireSession();
+      }
       return { status: res.status, body: parsed, durationMs: Math.round(performance.now() - started) };
     }
 
diff --git a/docs/configuration.md b/docs/configuration.md
index 7bb1b30..be3f165 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -73,8 +73,11 @@ See [Kubernetes / Helm](kubernetes.md) and
 | `secrets.ticketSigningKey` | Must be rotated for shared clusters |
 | `service.port` | ClusterIP port (default `8080`) |
 
-`gateway.*` / `ingress.*` in `values.yaml` are reserved; the chart currently
-exposes FastAPI directly (no Compose-style nginx gateway).
+`gateway.*` is unused (no Compose-style nginx gateway in the chart).
+`ingress.*` is optional — see
+[`values-ingress-example.yaml`](../helm/ovirt-api-simulator/values-ingress-example.yaml)
+and [Troubleshooting](troubleshooting.md) for annotations that preserve Engine
+fault bodies.
 
 ## Contract packs
 
diff --git a/docs/kubernetes.md b/docs/kubernetes.md
index 64a7ffd..778de55 100644
--- a/docs/kubernetes.md
+++ b/docs/kubernetes.md
@@ -19,9 +19,12 @@ Published image (when pushed):
 | **seed** Job (optional) | `minimal` or `demo` lab data |
 
 > The Compose stack publishes Engine HTTPS + UI via nginx `api-gateway`
-> ([ports.md](ports.md)). The Helm chart **does not yet** ship that gateway:
-> `gateway.*` / `ingress.*` keys in `values.yaml` are reserved and unused.
-> Access the simulator Service on `:8080` (port-forward or your own Ingress).
+> ([ports.md](ports.md)). The Helm chart serves the simulator Service on `:8080`.
+> Optional Ingress: enable with
+> [`values-ingress-example.yaml`](../helm/ovirt-api-simulator/values-ingress-example.yaml)
+> (`proxy-intercept-errors: "false"`, `custom-http-errors: "502,503"` so Engine
+> fault bodies are not rewritten to branded HTML). See
+> [Troubleshooting](troubleshooting.md).
 
 ## Prerequisites
 
diff --git a/docs/prompts/fix-api-errors-auth-ui-other-sims.md b/docs/prompts/fix-api-errors-auth-ui-other-sims.md
new file mode 100644
index 0000000..520b03e
--- /dev/null
+++ b/docs/prompts/fix-api-errors-auth-ui-other-sims.md
@@ -0,0 +1,92 @@
+# Prompt: fix API error bodies + Web UI session on 401 (other simulators)
+
+Copy everything below the line into a chat opened on **ovirt_api_simulator**,
+**vmware_api_simulator**, or **openstack_api_simulator**. Adapt product names
+(API path prefixes, cookie/CSRF names, Helm chart paths) to that repo.
+
+---
+
+## Task
+
+Fix the same class of production issues already fixed in
+`proxmox_api_simulator` (reference implementation). Do **not** claim the
+simulator is “incomplete” or “not supported”; keep durable, realistic API
+behavior.
+
+### Symptoms seen behind Ingress
+
+1. Client calls a path with a **wrong / missing resource id** (e.g. bad node /
+   host / datacenter name). Instead of the simulator’s JSON/XML error, the
+   browser or curl receives a **branded HTML 404** (“page not found”) from the
+   cluster Ingress / custom error pages.
+2. Client sends a mutation (**POST/PUT/DELETE**) that the Ingress rejects or
+   rewrites → **nginx HTML 405** instead of the simulator’s auth/validation
+   error.
+3. In the **Web UI**, after the API returns **401** (expired session), the
+   response panel says unauthorized but the **header still shows the signed-in
+   user** (does not switch to Guest / signed-out).
+
+Root cause for (1)/(2) is usually **ingress-nginx**
+`custom-http-errors` / `proxy-intercept-errors` replacing upstream bodies.
+Root cause for (3) is UI code that renders 401 text but does not clear
+ticket/token/cookie/localStorage and call the same path as logout.
+
+### What to implement in THIS repo
+
+#### 1. Clearer “resource not found” API errors
+
+- Find the shared helper that validates that a node/host/cluster/datacenter
+  exists (equivalent of Proxmox `require_node`).
+- On miss, return the **native API error shape** for this product with a
+  message that includes the bad id, e.g. Proxmox style:
+  `No such node ('pve01')` plus a field-level `errors` map when the product
+  uses one.
+- Update unit tests that matched the old message string.
+- Ensure the app always returns `Content-Type` appropriate for the API
+  (JSON/XML) and never an HTML error page from the app itself.
+
+#### 2. Web UI: treat HTTP 401 as session expiry
+
+- When any in-app API helper gets **401** and a session is currently stored:
+  - clear ticket/token/csrf/username (whatever this UI uses);
+  - clear auth cookies;
+  - clear persisted auth in localStorage/sessionStorage;
+  - update the header auth pill / badge to the signed-out / Guest state;
+  - show a short toast like “Session expired — sign in again”;
+  - still show the 401 explanation in the response panel.
+- Refactor logout to share one `clearSession(...)` helper so logout and
+  expiry stay in sync. Do not leave stale “signed in as …” UI after 401.
+
+#### 3. Helm / Ingress example + docs
+
+- In the chart’s ingress example values (and kubernetes troubleshooting docs):
+  - `nginx.ingress.kubernetes.io/proxy-intercept-errors: "false"`
+  - `nginx.ingress.kubernetes.io/custom-http-errors: "502,503"`
+    (do **not** list 404/405 so API bodies are preserved)
+- Document: if clients still see branded HTML 404/405, the cluster controller
+  is rewriting responses — fix Ingress annotations, not the simulator handlers.
+- Document a correct authenticated mutation curl for this product (cookie /
+  token + CSRF if required + the body encoding this API expects — often
+  form-urlencoded, not bare JSON).
+
+### Out of scope
+
+- Do not add “not implemented in the simulator” user-facing messages.
+- Do not change unrelated product semantics.
+- Do not force-push or commit unless the user asks.
+
+### Done when
+
+- Missing resource → product-shaped API error with the id in the message
+  (verified by unit test and/or curl against the app, not only via Ingress).
+- UI 401 → Guest / signed-out header + cleared storage/cookies.
+- Ingress example + troubleshooting docs warn about HTML error-page rewrite
+  and show the correct curl pattern.
+- Lint/tests for touched areas pass.
+
+### Reference (proxmox_api_simulator)
+
+- `app/handlers/common.py` — `require_node` / `node_metadata` message
+- `app/web/index.html` — `clearSession` / `expireSession` / `showResponse` 401
+- `helm/proxmox-api-simulator/values-ingress-example.yaml` — annotations
+- `docs/troubleshooting.md` — Ingress HTML 404/405 + curl notes
diff --git a/docs/ru/configuration.md b/docs/ru/configuration.md
index ea38332..71b46fd 100644
--- a/docs/ru/configuration.md
+++ b/docs/ru/configuration.md
@@ -73,8 +73,11 @@ Docker Compose подставляет многие из них для серви
 | `secrets.ticketSigningKey` | Нужно ротировать на общих кластерах |
 | `service.port` | Порт ClusterIP (по умолчанию `8080`) |
 
-`gateway.*` / `ingress.*` в `values.yaml` зарезервированы; чарт сейчас отдаёт
-FastAPI напрямую (без nginx gateway как в Compose).
+`gateway.*` не используется (нет nginx gateway как в Compose).
+`ingress.*` опционален — см.
+[`values-ingress-example.yaml`](../../helm/ovirt-api-simulator/values-ingress-example.yaml)
+и [Устранение неполадок](troubleshooting.md) для annotations, сохраняющих
+тела fault Engine.
 
 ## Контрактные packs
 
diff --git a/docs/ru/kubernetes.md b/docs/ru/kubernetes.md
index cd6b9f3..76e224a 100644
--- a/docs/ru/kubernetes.md
+++ b/docs/ru/kubernetes.md
@@ -19,10 +19,12 @@
 | **seed** Job (опционально) | Лабораторные данные `minimal` или `demo` |
 
 > Compose публикует Engine HTTPS + UI через nginx `api-gateway`
-> ([ports.md](ports.md)). Helm-чарт **пока не** включает этот gateway:
-> ключи `gateway.*` / `ingress.*` в `values.yaml` зарезервированы и не
-> используются. Доступ — к Service симулятора на `:8080` (port-forward или
-> свой Ingress).
+> ([ports.md](ports.md)). Helm-чарт отдаёт Service симулятора на `:8080`.
+> Опциональный Ingress:
+> [`values-ingress-example.yaml`](../../helm/ovirt-api-simulator/values-ingress-example.yaml)
+> (`proxy-intercept-errors: "false"`, `custom-http-errors: "502,503"`, чтобы
+> fault Engine не подменялся брендированным HTML). См.
+> [Устранение неполадок](troubleshooting.md).
 
 ## Требования
 
diff --git a/docs/ru/troubleshooting.md b/docs/ru/troubleshooting.md
index 38ed894..e2f402e 100644
--- a/docs/ru/troubleshooting.md
+++ b/docs/ru/troubleshooting.md
@@ -38,6 +38,49 @@ make seed-demo
 Проверьте, что `OVIRT_SERIES` соответствует ожидаемому pack
 ([api-versions.md](api-versions.md)).
 
+## HTTP 401 / Web UI всё ещё показывает пользователя
+
+Токен Engine SSO истёк или отозван (например после `demo/unload` / reseed).
+В Web UI HTTP **401** очищает локальную сессию и показывает **Guest** в
+шапке; войдите снова из Environment (`admin@internal` / `secret`).
+
+## Ingress отдаёт брендированный HTML 404 / nginx 405 вместо fault Engine
+
+Симулятор отвечает на ошибки API **fault** XML/JSON (`reason` / `detail`).
+Если видите HTML «page not found» или plain nginx **405**, **Ingress /
+reverse proxy** подменил тело ответа (часто через `custom-http-errors` у
+ingress-nginx).
+
+Исправление на Ingress для этого host (см.
+`helm/ovirt-api-simulator/values-ingress-example.yaml`):
+
+```yaml
+annotations:
+  nginx.ingress.kubernetes.io/proxy-intercept-errors: "false"
+  nginx.ingress.kubernetes.io/custom-http-errors: "502,503"
+```
+
+Проверьте с `Accept: application/json`. Отсутствующий host должен выглядеть так:
+
+```json
+{"fault": {"reason": "NotFound", "detail": "No such host ('…')"}}
+```
+
+### Корректная authenticated mutation (стиль Engine)
+
+Bearer (или Basic) и JSON-тело (не form-urlencoded):
+
+```bash
+# после POST /ovirt-engine/sso/oauth/token → access_token
+TOKEN=…
+curl -sk -X POST "https://HOST/ovirt-engine/api/vms" \
+  -H "Authorization: Bearer $TOKEN" \
+  -H "Accept: application/json" \
+  -H "Content-Type: application/json" \
+  -H "Version: 4" \
+  -d '{"vm":{"name":"lab-vm","cluster":{"name":"Default"}}}'
+```
+
 ## Падения клиентских suites
 
 Убедитесь, что стек поднят и засеян, затем сначала smoke:
diff --git a/docs/troubleshooting.md b/docs/troubleshooting.md
index 0824b0e..0630556 100644
--- a/docs/troubleshooting.md
+++ b/docs/troubleshooting.md
@@ -36,6 +36,49 @@ make seed-demo
 Set `Version: 4` (or `3`) or use `/ovirt-engine/api/v4/...`. Confirm
 `OVIRT_SERIES` matches the pack you expect ([api-versions.md](api-versions.md)).
 
+## HTTP 401 / Web UI still shows signed-in user
+
+Engine SSO token expired or was revoked (e.g. after `demo/unload` / reseed).
+In the Web UI, HTTP **401** clears the local session and shows **Guest** in the
+header; sign in again from Environment (`admin@internal` / `secret`).
+
+## Ingress returns branded HTML 404 / nginx 405 instead of Engine fault
+
+The simulator answers API errors as Engine **fault** XML/JSON
+(`reason` / `detail`). If you see a site HTML “page not found” or plain nginx
+**405** page, the **Ingress / reverse proxy** replaced the upstream body (often
+via `custom-http-errors` on the ingress-nginx controller).
+
+Fix on the Ingress for this host (see
+`helm/ovirt-api-simulator/values-ingress-example.yaml`):
+
+```yaml
+annotations:
+  nginx.ingress.kubernetes.io/proxy-intercept-errors: "false"
+  nginx.ingress.kubernetes.io/custom-http-errors: "502,503"
+```
+
+Then re-check with `Accept: application/json`. A missing host should look like:
+
+```json
+{"fault": {"reason": "NotFound", "detail": "No such host ('…')"}}
+```
+
+### Correct authenticated mutation (Engine-style)
+
+Use Bearer (or Basic) auth and JSON body (not form-urlencoded):
+
+```bash
+# after POST /ovirt-engine/sso/oauth/token → access_token
+TOKEN=…
+curl -sk -X POST "https://HOST/ovirt-engine/api/vms" \
+  -H "Authorization: Bearer $TOKEN" \
+  -H "Accept: application/json" \
+  -H "Content-Type: application/json" \
+  -H "Version: 4" \
+  -d '{"vm":{"name":"lab-vm","cluster":{"name":"Default"}}}'
+```
+
 ## Client suite failures
 
 Ensure the stack is up and seeded, then run smoke first:
diff --git a/helm/ovirt-api-simulator/README.md b/helm/ovirt-api-simulator/README.md
index 5e64fd5..b793bbf 100644
--- a/helm/ovirt-api-simulator/README.md
+++ b/helm/ovirt-api-simulator/README.md
@@ -15,8 +15,9 @@ helm upgrade --install ovirt-sim . \
   --set secrets.ticketSigningKey="$(openssl rand -hex 32)"
 ```
 
-Access via port-forward to Service `:8080` (Engine API, SSO, Web UI, `/docs`).
-The Compose nginx gateway is **not** part of this chart yet.
+Access via port-forward to Service `:8080` (Engine API, SSO, Web UI, `/docs`),
+or enable Ingress with
+[`values-ingress-example.yaml`](values-ingress-example.yaml).
 
 Full guide: [docs/kubernetes.md](../../docs/kubernetes.md).  
 Values: [`values.yaml`](values.yaml).
diff --git a/helm/ovirt-api-simulator/README.ru.md b/helm/ovirt-api-simulator/README.ru.md
index ede7d93..5776350 100644
--- a/helm/ovirt-api-simulator/README.ru.md
+++ b/helm/ovirt-api-simulator/README.ru.md
@@ -15,8 +15,9 @@ helm upgrade --install ovirt-sim . \
   --set secrets.ticketSigningKey="$(openssl rand -hex 32)"
 ```
 
-Доступ через port-forward к Service `:8080` (Engine API, SSO, Web UI, `/docs`).
-Nginx gateway из Compose в этот чарт **пока не** входит.
+Доступ через port-forward к Service `:8080` (Engine API, SSO, Web UI, `/docs`)
+или через Ingress с
+[`values-ingress-example.yaml`](values-ingress-example.yaml).
 
 Полное руководство: [docs/ru/kubernetes.md](../../docs/ru/kubernetes.md).  
 Values: [`values.yaml`](values.yaml).
diff --git a/helm/ovirt-api-simulator/templates/ingress.yaml b/helm/ovirt-api-simulator/templates/ingress.yaml
new file mode 100644
index 0000000..54310eb
--- /dev/null
+++ b/helm/ovirt-api-simulator/templates/ingress.yaml
@@ -0,0 +1,43 @@
+{{- if .Values.ingress.enabled -}}
+{{- $fullName := include "ovirt-api-simulator.fullname" . -}}
+{{- $svcPort := .Values.service.port -}}
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: {{ $fullName }}
+  labels:
+    app: {{ include "ovirt-api-simulator.name" . }}
+  annotations:
+    {{- with .Values.ingress.annotations }}
+    {{- toYaml . | nindent 4 }}
+    {{- end }}
+spec:
+  {{- with .Values.ingress.className }}
+  ingressClassName: {{ . }}
+  {{- end }}
+  {{- if .Values.ingress.tls }}
+  tls:
+    {{- range .Values.ingress.tls }}
+    - hosts:
+        {{- range .hosts }}
+        - {{ . | quote }}
+        {{- end }}
+      secretName: {{ .secretName }}
+    {{- end }}
+  {{- end }}
+  rules:
+    {{- range .Values.ingress.hosts }}
+    - host: {{ .host | quote }}
+      http:
+        paths:
+          {{- range .paths }}
+          - path: {{ .path }}
+            pathType: {{ .pathType }}
+            backend:
+              service:
+                name: {{ $fullName }}
+                port:
+                  number: {{ $svcPort }}
+          {{- end }}
+    {{- end }}
+{{- end }}
diff --git a/helm/ovirt-api-simulator/values-ingress-example.yaml b/helm/ovirt-api-simulator/values-ingress-example.yaml
new file mode 100644
index 0000000..09c1f50
--- /dev/null
+++ b/helm/ovirt-api-simulator/values-ingress-example.yaml
@@ -0,0 +1,49 @@
+# Example: public Ingress + Hub image.
+#
+# WARNING: Laboratory / demo template. Always override weak secrets:
+#   --set secrets.ticketSigningKey="$(openssl rand -hex 32)"
+#   --set postgresql.auth.password="$(openssl rand -hex 16)"
+# Do not expose a public Ingress with the placeholder values below.
+#
+#   helm upgrade --install ovirt-sim ./helm/ovirt-api-simulator \
+#     -n ovirt-sim --create-namespace \
+#     -f helm/ovirt-api-simulator/values-ingress-example.yaml \
+#     --set ingress.hosts[0].host=ovirt-sim.example.com \
+#     --set secrets.ticketSigningKey="$(openssl rand -hex 32)" \
+#     --set postgresql.auth.password="$(openssl rand -hex 16)"
+
+image:
+  repository: inecs/ovirt-api-simulator
+  tag: "0.1.0"
+  pullPolicy: IfNotPresent
+
+secrets:
+  ticketSigningKey: "replace-me"
+
+postgresql:
+  enabled: true
+  auth:
+    username: ovirt
+    password: "replace-me-db-password"
+    database: ovirt_simulator
+
+seed:
+  enabled: true
+  profile: minimal
+
+ingress:
+  enabled: true
+  className: nginx
+  # Keep Engine XML/JSON fault bodies (404/405/401). Cluster-wide
+  # custom-http-errors HTML pages must not rewrite simulator error responses.
+  annotations:
+    nginx.ingress.kubernetes.io/proxy-intercept-errors: "false"
+    # If the controller still injects branded HTML for 404/405, narrow or clear
+    # custom-http-errors on this Ingress (overrides controller defaults):
+    nginx.ingress.kubernetes.io/custom-http-errors: "502,503"
+  hosts:
+    - host: ovirt-sim.example.com
+      paths:
+        - path: /
+          pathType: Prefix
+  tls: []
diff --git a/helm/ovirt-api-simulator/values.yaml b/helm/ovirt-api-simulator/values.yaml
index f3e7395..924255c 100644
--- a/helm/ovirt-api-simulator/values.yaml
+++ b/helm/ovirt-api-simulator/values.yaml
@@ -20,11 +20,16 @@ gateway:
 ingress:
   enabled: false
   className: nginx
+  # Prefer values-ingress-example.yaml for public Ingress. Keep API fault bodies:
+  #   nginx.ingress.kubernetes.io/proxy-intercept-errors: "false"
+  #   nginx.ingress.kubernetes.io/custom-http-errors: "502,503"  # not 404/405
+  annotations: {}
   hosts:
     - host: ovirt-engine.local
       paths:
         - path: /
           pathType: Prefix
+  tls: []
 
 config:
   ovirtSeries: "4.5"
diff --git a/tests/unit/test_ovirt_common.py b/tests/unit/test_ovirt_common.py
new file mode 100644
index 0000000..1eff7c4
--- /dev/null
+++ b/tests/unit/test_ovirt_common.py
@@ -0,0 +1,35 @@
+"""Unit tests for native Engine NotFound helpers."""
+
+from __future__ import annotations
+
+import pytest
+
+from app.ovirt.common import no_such
+from app.ovirt.errors import OVirtError, fault_body
+from app.ovirt.repr import generic_entity
+
+
+def test_no_such_includes_id_in_detail() -> None:
+    err = no_such("host", "pve01-bad-id")
+    assert isinstance(err, OVirtError)
+    assert err.status_code == 404
+    assert err.reason == "NotFound"
+    assert err.detail == "No such host ('pve01-bad-id')"
+
+
+def test_no_such_fault_body_is_json_not_html() -> None:
+    err = no_such("datacenter", "missing-dc")
+    body = fault_body(err, as_xml=False)
+    assert body == {
+        "fault": {"reason": "NotFound", "detail": "No such datacenter ('missing-dc')"}
+    }
+    xml = fault_body(err, as_xml=True)
+    assert isinstance(xml, str)
+    assert "No such datacenter ('missing-dc')" in xml
+    assert "<html" not in xml.lower()
+
+
+def test_generic_entity_none_raises_no_such() -> None:
+    with pytest.raises(OVirtError, match=r"No such host \('abc'\)") as caught:
+        generic_entity("hosts", "host", None, entity_id="abc")
+    assert caught.value.status_code == 404