diff --git a/custom_components/houseplan/auth.py b/custom_components/houseplan/auth.py
index 6d7ad45a..d78c96e6 100644
--- a/custom_components/houseplan/auth.py
+++ b/custom_components/houseplan/auth.py
@@ -7,6 +7,7 @@ one behaviour.
 """
 from __future__ import annotations
 
+from homeassistant.auth.const import GROUP_ID_READ_ONLY
 from homeassistant.core import HomeAssistant
 
 from .const import CONF_ADMIN_ONLY
@@ -28,4 +29,21 @@ def may_write(hass: HomeAssistant, user) -> bool:
     # UI has always been admin-gated, and an unset option must not open every
     # write WS/HTTP path to every authenticated household user.
     admin_only = bool(entry.options.get(CONF_ADMIN_ONLY, True))
-    return is_admin if admin_only else True
+    if admin_only:
+        return is_admin
+
+    # Turning off ``admin_only`` grants editing to ordinary household users,
+    # not to HA's explicitly read-only role (#626).  ``groups`` is part of the
+    # supported HA User model; if a non-admin connection cannot provide a
+    # complete group list, the safe interpretation is that write permission
+    # has not been established.
+    groups = getattr(user, "groups", None)
+    if not isinstance(groups, list) or not groups:
+        return False
+    group_ids: list[str] = []
+    for group in groups:
+        group_id = getattr(group, "id", None)
+        if not isinstance(group_id, str):
+            return False
+        group_ids.append(group_id)
+    return GROUP_ID_READ_ONLY not in group_ids
diff --git a/custom_components/houseplan/websocket_api.py b/custom_components/houseplan/websocket_api.py
index 24fed588..ef011301 100755
--- a/custom_components/houseplan/websocket_api.py
+++ b/custom_components/houseplan/websocket_api.py
@@ -1056,6 +1056,9 @@ async def ws_plans_list(hass: HomeAssistant, connection, msg: dict[str, Any]) ->
     works as a policy if the user can see them: detaching a plan keeps the
     image, and this is how it gets picked up again — or deleted on purpose.
     """
+    if not _check_write(hass, connection):
+        connection.send_error(msg["id"], "unauthorized", "Only writers may list plans")
+        return
     rt = _runtime(hass, connection, msg["id"])
     if rt is None:
         return
@@ -2386,12 +2389,27 @@ async def _purge_trail_recorder(hass: HomeAssistant, config: dict[str, Any]) ->
     return await rec.async_purge_orphans(config) if rec else 0
 
 
+def _public_trails(value: Any) -> Any:
+    """Copy the trail book for View without exposing source entity ids (#626)."""
+    if isinstance(value, dict):
+        return {
+            key: _public_trails(item)
+            for key, item in value.items()
+            if key != "source"
+        }
+    if isinstance(value, list):
+        return [_public_trails(item) for item in value]
+    return value
+
+
 @websocket_api.websocket_command({vol.Required("type"): "houseplan/trail/get"})
 @websocket_api.async_response
 async def ws_trail_get(hass: HomeAssistant, connection: websocket_api.ActiveConnection, msg: dict) -> None:
-    """Current + previous cleanup runs per marker, raw robot coordinates."""
+    """Current + previous runs and raw coordinates, without source entity ids."""
     rec = hass.data.get(DOMAIN, {}).get("trail_recorder")
-    connection.send_result(msg["id"], {"trails": rec.book.data if rec else {}})
+    connection.send_result(
+        msg["id"], {"trails": _public_trails(rec.book.data) if rec else {}}
+    )
 
 
 @websocket_api.websocket_command(
diff --git a/docs/ARCHITECTURE.md b/docs/ARCHITECTURE.md
index d023c4d9..a9a932ad 100644
--- a/docs/ARCHITECTURE.md
+++ b/docs/ARCHITECTURE.md
@@ -1220,6 +1220,17 @@ transmit light is the separate `zero_wall_style` policy.
 
 ## Integration WS API
 
+`may_write` is the single writer policy for WebSocket and HTTP: administrators
+always write; with `admin_only=true` nobody else writes; with
+`admin_only=false` ordinary non-admin groups write while
+`system-read-only` remains denied. Missing or incomplete user/group data fails
+closed. Read ACL is intentionally different: authenticated View receives the
+complete config and layout without per-entity projection. The maintenance
+catalogs `plans/list` and `assets/list` are writer-only; `trail/get` keeps the
+coordinates needed by View but projects every `source` entity ID out of the
+response without mutating the recorder store. `virtual_light/toggle` remains an
+authenticated View action, not a writer operation.
+
 | Command | Parameters | Response |
 |---|---|---|
 | `houseplan/layout/get` | — | `{layout: {device_id: {x,y}}, rev}` |
@@ -1227,13 +1238,13 @@ transmit light is the separate `zero_wall_style` policy.
 | `houseplan/layout/update` | `device_id`, `pos` | `{ok, rev}`; event `houseplan_layout_updated` |
 | `houseplan/config/get` | — | `{config, rev, virtual_lights:{rev,config_rev,off[]}, decor_assets_api?}` (runtime capabilities are optional for rolling compatibility) |
 | `houseplan/virtual_light/toggle` | `marker_id` | `{marker_id,on,rev}` / err `not_toggleable`; event `houseplan_virtual_light_updated` |
-| `houseplan/trail/get` | — | `{trails: {marker: {current, previous}}}` — vacuum runs, raw robot coords |
+| `houseplan/trail/get` | — | `{trails: {marker: {current, previous}}}` — vacuum runs and raw robot coords, with internal `source` entity IDs removed |
 | `houseplan/trail/delete` | `marker_id` | `{ok, removed}` — erase current/previous runs after marker deletion |
 | `houseplan/config/set` | `config`, `expected_rev` | `{ok, rev}` / err `conflict`; event `houseplan_config_updated` |
 | `houseplan/plan/optimize` | `config`, `layout`, both expected revisions | crash-resumable two-store commit + one-deep backup |
 | `houseplan/plan/optimize_undo` | both expected revisions | restores backup only before any later edit |
 | `houseplan/plan/set` | `space_id`, `ext` (svg/png/jpg/webp), `data` (b64, ≤8 MB) | `{ok, url}` — writes `<space>.<token>.<ext>`, deletes nothing |
-| `houseplan/plans/list` | — | `{plans: [{name, url, size, modified, used_by}], total}` (newest 60) |
+| `houseplan/plans/list` | — | writer-only `{plans: [{name, url, size, modified, used_by}], total}` (newest 60) |
 | `houseplan/plans/delete` | `name` | `{ok, removed}` / err `in_use` |
 | `houseplan/layout/delete` | `device_id` | `{ok, rev}`; event `houseplan_layout_updated` |
 | `houseplan/geometry/repair` | `space_id`, `aspect`, `dry_run?`, `undo?` | preview / `{ok, rev, moved}` / `{restored}`; errs `nothing_to_repair`, `no_backup` |
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 7f5f04f1..104242b2 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -2,6 +2,12 @@
 
 ## Unreleased
 
+- Home Assistant's `system-read-only` users now remain read-only even when
+  House Plan editing is opened to ordinary household members. They keep the
+  complete View experience, including vacuum paths, but cannot edit, upload or
+  delete data; the maintenance list of stored plan files is writer-only and
+  vacuum responses no longer expose the internal map-source entity ID
+  ([#626](https://github.com/Matysh/houseplan-card/issues/626)).
 - The main toolbar no longer shows the device count (“37 dev.”), and it stops
   jumping sideways when you open, close or switch editors: the editor’s close
   **×** now has its own fixed place right after the mode buttons, kept empty
diff --git a/docs/CHANGELOG.ru.md b/docs/CHANGELOG.ru.md
index 9ecf2aa2..c9b4060a 100755
--- a/docs/CHANGELOG.ru.md
+++ b/docs/CHANGELOG.ru.md
@@ -8,6 +8,13 @@
 
 ## Не выпущено
 
+- Пользователи группы Home Assistant `system-read-only` теперь остаются только
+  зрителями, даже если редактирование House Plan разрешено обычным домочадцам.
+  Полноценный просмотр, включая маршруты пылесоса, сохраняется, но редактировать,
+  загружать и удалять данные нельзя; служебный список файлов планов доступен
+  только редакторам, а ответ с маршрутом больше не раскрывает внутренний entity
+  ID источника карты
+  ([#626](https://github.com/Matysh/houseplan-card/issues/626)).
 - Основная панель больше не показывает счётчик устройств («37 устр.») и не
   дёргается по горизонтали при входе в редактор, выходе из него и
   переключении редакторов: крестик **×** закрытия редактора теперь стоит на
diff --git a/docs/SCOPE.md b/docs/SCOPE.md
index a8334aa5..48a648c7 100755
--- a/docs/SCOPE.md
+++ b/docs/SCOPE.md
@@ -30,8 +30,13 @@ obvious" is somebody else's job.
 | **Guests / kiosk** | View-only glance at the home | Wall tablet |
 
 Design consequence: **View mode is the product** for two of the three personas.
-Editors are admin-only tools and must never leak interactions into View
-(established by UX-MODES; lock guard, inert openings, no drag in View).
+Editors are writer-only tools and must never leak interactions into View
+(established by UX-MODES; lock guard, inert openings, no drag in View). By
+default only administrators are writers; an installation may explicitly let
+ordinary household users edit, but Home Assistant's `system-read-only` group
+never becomes a writer. Authenticated View deliberately shares the complete
+spatial plan and represented-device configuration with household members rather
+than pretending to be an entity-by-entity privacy boundary.
 The desktop browser with mouse/keyboard is the reference and recommended
 editing environment. Editor parity on touch is outside the product guarantee;
 deliberate degradation is allowed under `TOUCH-SUPPORT.md`.
diff --git a/docs/USER-GUIDE.md b/docs/USER-GUIDE.md
index ce914dc5..972db6c5 100644
--- a/docs/USER-GUIDE.md
+++ b/docs/USER-GUIDE.md
@@ -154,8 +154,10 @@ update: it shows a panel asking to reload the page.
 
 Every signed-in user can view the plan. Home Assistant permissions still govern
 device service calls. With the default integration option, only administrators
-can edit configuration or upload files. Plan optimization and its undo always
-require an administrator.
+can edit configuration or upload files. If that option is disabled, ordinary
+household users may edit, but members of Home Assistant's `system-read-only`
+group never become writers. Plan optimization and its undo always require an
+administrator.
 
 The **House Plan** sidebar item is visible to every signed-in user. A user who
 cannot edit gets the complete View experience without editor controls. On an
@@ -1289,6 +1291,24 @@ the recovery record remains for another attempt or a Home Assistant restart.
 
 ## 20. Storage, multiple cards and backups
 
+### Who can see and change shared data
+
+| Home Assistant role | Visible in House Plan | May change House Plan |
+|---|---|---|
+| Administrator | The complete plan, represented devices and the maintenance catalog of plan files | Yes |
+| Ordinary user | The complete plan and every device represented on it | Only when “administrators only” editing is disabled for the integration |
+| `system-read-only` user | The complete plan and every device represented on it | Never |
+
+House Plan is a shared spatial map of the home, not a separate per-entity
+privacy boundary. The plan configuration is therefore not filtered through the
+viewer's entity permissions: a household member who can open View sees its rooms
+and represented devices. Normal Home Assistant permissions still govern actions
+against real devices.
+
+The maintenance catalog of stored plan files (names, sizes and usage) is
+writer-only. Vacuum coordinates remain available because View renders the path,
+but the map source's internal entity ID is removed from the response.
+
 ### Portable JSON backup
 
 **Global settings → Backup and transfer** exports either the complete House
diff --git a/docs/USER-GUIDE.ru.md b/docs/USER-GUIDE.ru.md
index f5a41424..8f5e8ae7 100644
--- a/docs/USER-GUIDE.ru.md
+++ b/docs/USER-GUIDE.ru.md
@@ -159,7 +159,7 @@ storage-панель в устаревший YAML только ради House Pl
 | Настройка интеграции | Просмотр | Управление устройствами | Редактирование планов и загрузка файлов |
 |---|---:|---:|---:|
 | Только администраторы — включено (по умолчанию) | Все вошедшие пользователи | По обычным правам HA | Только администраторы |
-| Только администраторы — выключено | Все вошедшие пользователи | По обычным правам HA | Все вошедшие пользователи |
+| Только администраторы — выключено | Все вошедшие пользователи | По обычным правам HA | Все, кроме пользователей группы HA `system-read-only` |
 
 Оптимизация планов и отмена оптимизации всегда требуют администратора, независимо от этой опции.
 
@@ -2103,6 +2103,25 @@ House Plan не позволит следующей правке перезап
 
 ## 20. Хранение, совместная работа и резервные копии
 
+### Кто видит и изменяет общие данные
+
+| Роль Home Assistant | Что видно в House Plan | Можно изменять House Plan |
+|---|---|---|
+| Администратор | Весь план, устройства и служебный каталог файлов планов | Да |
+| Обычный пользователь | Весь план и все представленные на нём устройства | Только если в интеграции выключено «редактировать план только администраторам» |
+| Пользователь группы `system-read-only` | Весь план и все представленные на нём устройства | Нет при любом значении настройки |
+
+House Plan — общая пространственная карта дома, а не отдельная граница
+приватности для каждой сущности. Поэтому конфигурация плана не фильтруется по
+entity-разрешениям конкретного пользователя: домочадец, которому доступен View,
+видит комнаты и представленные на плане устройства. Обычные права Home
+Assistant по-прежнему применяются к действиям с реальными устройствами.
+
+Служебный список файлов планов (имена, размеры и использование) доступен только
+тем, кто может редактировать. Маршруты пылесоса нужны режиму View, поэтому их
+координаты доступны зрителю, но внутренний entity ID источника карты в ответ не
+передаётся.
+
 ### Переносимая JSON-копия House Plan
 
 Откройте **Общие настройки → Резервная копия и перенос**. Экспорт предлагает
diff --git a/scripts/mutation-registry.mjs b/scripts/mutation-registry.mjs
index 1305ad4b..c4dbe6cc 100644
--- a/scripts/mutation-registry.mjs
+++ b/scripts/mutation-registry.mjs
@@ -72,6 +72,48 @@ function relocateEditorPatch(patch, cardSource, editorSource) {
 // `find` обязан встречаться в файле ровно один раз: патч, который ложится «куда
 // попало», проверяет не то, что объявлен проверять. Это контролирует --check.
 const MUTANT_DEFINITIONS = [
+  {
+    id: 'acl-readonly-group-becomes-writer',
+    guard: 'node scripts/backend-test-guard.mjs '
+      + 'may_write_honours_explicit_admin_only_false '
+      + 'tests_backend/test_ha_websocket.py',
+    because: '#626 AC1/AC5: disabling admin_only admits household editors, but HA system-read-only '
+      + 'must remain unable to mutate config or upload content.',
+    patches: [{
+      file: 'custom_components/houseplan/auth.py',
+      find: '    return GROUP_ID_READ_ONLY not in group_ids\n',
+      replace: '    return True  # mutant: read-only group inherits household writer access\n',
+    }],
+  },
+  {
+    id: 'acl-plan-catalog-open-to-viewers',
+    guard: 'node scripts/backend-test-guard.mjs '
+      + 'issue_626_plans_list_refuses_viewer_before_scanning '
+      + 'tests_backend/test_ha_websocket.py',
+    because: '#626 AC2/AC3: the stored plan filename and usage catalog is maintenance data for '
+      + 'writers, not part of authenticated View.',
+    patches: [{
+      file: 'custom_components/houseplan/websocket_api.py',
+      find: '    if not _check_write(hass, connection):\n'
+        + '        connection.send_error(msg["id"], "unauthorized", "Only writers may list plans")\n'
+        + '        return\n'
+        + '    rt = _runtime(hass, connection, msg["id"])\n',
+      replace: '    rt = _runtime(hass, connection, msg["id"])  # mutant: viewers list plan files\n',
+    }],
+  },
+  {
+    id: 'acl-trail-view-exposes-source-entity',
+    guard: 'node scripts/backend-test-guard.mjs '
+      + 'issue_626_authenticated_read_acl_matrix_and_trail_projection '
+      + 'tests_backend/test_ha_websocket.py',
+    because: '#626 AC4: View needs robot coordinates, not private source entity ids embedded at '
+      + 'arbitrary levels of current and previous route records.',
+    patches: [{
+      file: 'custom_components/houseplan/websocket_api.py',
+      find: '            if key != "source"\n',
+      replace: '            if True  # mutant: expose source entity ids\n',
+    }],
+  },
   {
     id: 'view-conflict-requires-editor-runtime',
     guard: 'node --test test/config-write-conflict.test.mjs',
diff --git a/tests_backend/test_ha_upload.py b/tests_backend/test_ha_upload.py
index 98930647..03f0150d 100644
--- a/tests_backend/test_ha_upload.py
+++ b/tests_backend/test_ha_upload.py
@@ -8,20 +8,31 @@ def _enable_custom_integrations(enable_custom_integrations):
     yield
 
 from aiohttp import FormData
+from homeassistant.auth.const import GROUP_ID_USER
 from homeassistant.core import HomeAssistant
 from pytest_homeassistant_custom_component.common import MockConfigEntry
 from pytest_homeassistant_custom_component.typing import ClientSessionGenerator
 
-from custom_components.houseplan.const import DOMAIN
+from custom_components.houseplan.const import CONF_ADMIN_ONLY, DOMAIN
 
 
-async def _setup(hass: HomeAssistant) -> None:
-    entry = MockConfigEntry(domain=DOMAIN, title="House Plan", data={}, options={})
+async def _setup(hass: HomeAssistant, *, options: dict | None = None) -> None:
+    entry = MockConfigEntry(
+        domain=DOMAIN, title="House Plan", data={}, options=options or {}
+    )
     entry.add_to_hass(hass)
     assert await hass.config_entries.async_setup(entry.entry_id)
     await hass.async_block_till_done()
 
 
+async def _household_access_token(hass: HomeAssistant) -> str:
+    user = await hass.auth.async_create_user(
+        "House Plan household", group_ids=[GROUP_ID_USER]
+    )
+    refresh_token = await hass.auth.async_create_refresh_token(user)
+    return hass.auth.async_create_access_token(refresh_token)
+
+
 async def test_upload_ok(hass: HomeAssistant, hass_client: ClientSessionGenerator) -> None:
     await _setup(hass)
     client = await hass_client()
@@ -285,11 +296,11 @@ async def test_issue_617_plan_upload_limit_is_inclusive_and_refusal_leaves_nothi
     assert after == before, "a refused plan leaves neither a file nor a temporary behind"
 
 
-async def test_issue_617_plan_upload_refuses_non_admin(
+async def test_issue_626_plan_upload_refuses_read_only_but_allows_household(
     hass: HomeAssistant, hass_client: ClientSessionGenerator, hass_read_only_access_token: str,
 ) -> None:
-    """#617 AC4: the same write policy as ws_plan_set."""
-    await _setup(hass)
+    """#626 AC5: HTTP upload follows the same group-aware writer policy as WS."""
+    await _setup(hass, options={CONF_ADMIN_ONLY: False})
     client = await hass_client(hass_read_only_access_token)
     before = await hass.async_add_executor_job(_plans_listing, hass)
     resp = await client.post("/api/houseplan/plans/upload", data=_plan_form(b"PLAN"))
@@ -297,6 +308,12 @@ async def test_issue_617_plan_upload_refuses_non_admin(
     assert (await resp.json())["error"] == "unauthorized"
     assert await hass.async_add_executor_job(_plans_listing, hass) == before
 
+    household = await hass_client(await _household_access_token(hass))
+    allowed = await household.post(
+        "/api/houseplan/plans/upload", data=_plan_form(b"PLAN", "household")
+    )
+    assert allowed.status == 200, await allowed.text()
+
 
 async def test_issue_617_plan_upload_validates_fields_like_ws_plan_set(
     hass: HomeAssistant, hass_client: ClientSessionGenerator,
diff --git a/tests_backend/test_ha_websocket.py b/tests_backend/test_ha_websocket.py
index 464aa268..9a8c6ffa 100644
--- a/tests_backend/test_ha_websocket.py
+++ b/tests_backend/test_ha_websocket.py
@@ -6,6 +6,7 @@ import logging
 import threading
 import time
 from pathlib import Path
+from types import SimpleNamespace
 
 import pytest
 
@@ -15,6 +16,7 @@ def _enable_custom_integrations(enable_custom_integrations):
     """Allow loading custom_components in the test hass."""
     yield
 
+from homeassistant.auth.const import GROUP_ID_READ_ONLY, GROUP_ID_USER
 from homeassistant.core import HomeAssistant
 from pytest_homeassistant_custom_component.common import MockConfigEntry
 from pytest_homeassistant_custom_component.typing import WebSocketGenerator
@@ -31,14 +33,27 @@ from custom_components.houseplan.websocket_api import (
 )
 
 
-async def _setup(hass: HomeAssistant) -> MockConfigEntry:
-    entry = MockConfigEntry(domain=DOMAIN, title="House Plan", data={}, options={})
+async def _setup(
+    hass: HomeAssistant, *, options: dict | None = None
+) -> MockConfigEntry:
+    entry = MockConfigEntry(
+        domain=DOMAIN, title="House Plan", data={}, options=options or {}
+    )
     entry.add_to_hass(hass)
     assert await hass.config_entries.async_setup(entry.entry_id)
     await hass.async_block_till_done()
     return entry
 
 
+async def _access_token_for_group(hass: HomeAssistant, group_id: str) -> str:
+    """Create an authenticated non-owner client for one real HA system group."""
+    user = await hass.auth.async_create_user(
+        f"House Plan {group_id}", group_ids=[group_id]
+    )
+    refresh_token = await hass.auth.async_create_refresh_token(user)
+    return hass.auth.async_create_access_token(refresh_token)
+
+
 async def test_config_get_advertises_radar_only_while_coordinator_is_ready(
     hass: HomeAssistant, hass_ws_client: WebSocketGenerator,
 ) -> None:
@@ -1950,7 +1965,7 @@ async def test_may_write_defaults_admin_only_when_option_missing(hass):
 
 
 async def test_may_write_honours_explicit_admin_only_false(hass):
-    """Household users may write only when the option is explicitly off."""
+    """#626: admin_only off admits household users, never HA read-only users."""
     from custom_components.houseplan.auth import may_write
 
     entry = MockConfigEntry(
@@ -1960,10 +1975,125 @@ async def test_may_write_honours_explicit_admin_only_false(hass):
     assert await hass.config_entries.async_setup(entry.entry_id)
     await hass.async_block_till_done()
 
-    class _User:
-        is_admin = False
+    household = SimpleNamespace(
+        is_admin=False, groups=[SimpleNamespace(id=GROUP_ID_USER)]
+    )
+    read_only = SimpleNamespace(
+        is_admin=False, groups=[SimpleNamespace(id=GROUP_ID_READ_ONLY)]
+    )
+    mixed = SimpleNamespace(
+        is_admin=False,
+        groups=[
+            SimpleNamespace(id=GROUP_ID_USER),
+            SimpleNamespace(id=GROUP_ID_READ_ONLY),
+        ],
+    )
+    admin = SimpleNamespace(is_admin=True)
 
-    assert may_write(hass, _User()) is True
+    assert may_write(hass, admin) is True
+    assert may_write(hass, household) is True
+    assert may_write(hass, read_only) is False
+    assert may_write(hass, mixed) is False
+    assert may_write(hass, SimpleNamespace(is_admin=False, groups=[])) is False
+    assert may_write(hass, SimpleNamespace(is_admin=False)) is False
+    assert may_write(
+        hass, SimpleNamespace(is_admin=False, groups=[SimpleNamespace()])
+    ) is False
+
+
+async def test_issue_626_authenticated_read_acl_matrix_and_trail_projection(
+    hass: HomeAssistant,
+    hass_ws_client: WebSocketGenerator,
+    hass_read_only_access_token: str,
+) -> None:
+    """#626 AC2/AC4/AC5/AC7: one observable matrix pins every read role."""
+    await _setup(hass, options={CONF_ADMIN_ONLY: False})
+    admin = await hass_ws_client(hass)
+    household = await hass_ws_client(
+        hass, access_token=await _access_token_for_group(hass, GROUP_ID_USER)
+    )
+    read_only = await hass_ws_client(
+        hass, access_token=hass_read_only_access_token
+    )
+
+    recorder = hass.data[DOMAIN]["trail_recorder"]
+    stored_trails = {
+        "robot": {
+            "current": {
+                "source": "camera.private_map",
+                "route": {"source": "camera.private_route", "id": "ground"},
+                "points": [[10.0, 20.0]],
+            },
+            "previous": {
+                "source": "sensor.private_map",
+                "points": [[30.0, 40.0]],
+            },
+        }
+    }
+    recorder.book.data = copy.deepcopy(stored_trails)
+
+    for client, can_write in (
+        (admin, True),
+        (household, True),
+        (read_only, False),
+    ):
+        await client.send_json_auto_id({"type": "houseplan/config/get"})
+        config = await client.receive_json()
+        assert config["success"] and config["result"]["can_write"] is can_write
+
+        await client.send_json_auto_id({"type": "houseplan/layout/get"})
+        assert (await client.receive_json())["success"]
+
+        await client.send_json_auto_id({"type": "houseplan/trail/get"})
+        trails_response = await client.receive_json()
+        assert trails_response["success"]
+        public_trails = trails_response["result"]["trails"]
+        assert public_trails["robot"]["current"]["points"] == [[10.0, 20.0]]
+        assert "source" not in json.dumps(public_trails)
+
+        for command in ("houseplan/plans/list", "houseplan/assets/list"):
+            await client.send_json_auto_id({"type": command})
+            response = await client.receive_json()
+            if can_write:
+                assert response["success"], (command, response)
+            else:
+                assert not response["success"]
+                assert response["error"]["code"] == "unauthorized"
+
+    assert recorder.book.data == stored_trails, "View projection must not mutate storage"
+
+    candidate = {"spaces": [], "markers": [], "settings": {}}
+    await household.send_json_auto_id({
+        "type": "houseplan/config/set", "config": candidate, "expected_rev": 0,
+    })
+    assert (await household.receive_json())["success"]
+    await read_only.send_json_auto_id({
+        "type": "houseplan/config/set", "config": candidate, "expected_rev": 1,
+    })
+    refused = await read_only.receive_json()
+    assert not refused["success"] and refused["error"]["code"] == "unauthorized"
+
+
+async def test_issue_626_plans_list_refuses_viewer_before_scanning(
+    hass: HomeAssistant,
+    hass_ws_client: WebSocketGenerator,
+    hass_read_only_access_token: str,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """#626 AC3: refusal happens before filesystem work or catalog disclosure."""
+    await _setup(hass, options={CONF_ADMIN_ONLY: False})
+    read_only = await hass_ws_client(
+        hass, access_token=hass_read_only_access_token
+    )
+
+    def unexpected_executor_call(*_args, **_kwargs):
+        raise AssertionError("plans/list touched the filesystem for a viewer")
+
+    monkeypatch.setattr(hass, "async_add_executor_job", unexpected_executor_call)
+    await read_only.send_json_auto_id({"type": "houseplan/plans/list"})
+    response = await read_only.receive_json()
+    assert not response["success"]
+    assert response["error"]["code"] == "unauthorized"
 
 
 async def test_config_get_reports_can_write(hass: HomeAssistant, hass_ws_client: WebSocketGenerator) -> None:
@@ -2955,7 +3085,6 @@ async def test_decor_asset_resolve_readonly_is_limited_to_referenced_ids(
 async def test_decor_asset_resolve_non_admin_is_writer_when_admin_only_is_off(
     hass: HomeAssistant,
     hass_ws_client: WebSocketGenerator,
-    hass_read_only_access_token: str,
 ) -> None:
     """#432 AC2: resolve follows may_write instead of hard-coding admin."""
     import hashlib
@@ -2979,7 +3108,9 @@ async def test_decor_asset_resolve_non_admin_is_writer_when_admin_only_is_off(
         "created_at": "2026-01-01T00:00:00Z",
     }), encoding="utf-8")
 
-    client = await hass_ws_client(hass, access_token=hass_read_only_access_token)
+    client = await hass_ws_client(
+        hass, access_token=await _access_token_for_group(hass, GROUP_ID_USER)
+    )
     await client.send_json_auto_id({
         "type": "houseplan/assets/resolve", "asset_ids": [aid],
     })