diff --git a/homeassistant/components/sandbox/bridge.py b/homeassistant/components/sandbox/bridge.py
index 0a9e163dfc19..3170b36c151b 100644
--- a/homeassistant/components/sandbox/bridge.py
+++ b/homeassistant/components/sandbox/bridge.py
@@ -59,7 +59,7 @@ from homeassistant.const import (
     EVENT_STATE_CHANGED,
     EVENT_STATE_REPORTED,
 )
-from homeassistant.core import Context, HomeAssistant, callback
+from homeassistant.core import CALLBACK_TYPE, Context, HomeAssistant, callback
 from homeassistant.exceptions import HomeAssistantError
 from homeassistant.helpers import device_registry as dr
 from homeassistant.helpers.dispatcher import async_dispatcher_connect
@@ -74,6 +74,7 @@ from .const import UNIQUE_ID_SEPARATOR
 from .description import SandboxEntityDescription
 from .messages import (
     MSG_CALL_SERVICE,
+    MSG_CORE_CONFIG,
     MSG_ENTITY_QUERY,
     MSG_FIRE_EVENT,
     MSG_REGISTER_ENTITY,
@@ -84,6 +85,7 @@ from .messages import (
     MSG_STORE_SAVE,
     MSG_UNREGISTER_ENTITY,
     MSG_UNREGISTER_SERVICE,
+    core_config_to_proto,
     decode_json,
     decode_json_dict,
     encode_json,
@@ -177,6 +179,12 @@ class SandboxBridge:
         self._unsub_entry_changed = async_dispatcher_connect(
             hass, SIGNAL_CONFIG_ENTRY_CHANGED, self._on_config_entry_changed
         )
+        # Keep a running sandbox's core config in step with main — the
+        # entry_setup snapshot goes stale when the user changes the home
+        # location / units / language.
+        self._unsub_core_config: CALLBACK_TYPE | None = self.hass.bus.async_listen(
+            EVENT_CORE_CONFIG_UPDATE, self._on_core_config_update
+        )
 
         # Context security + restoration: the sandbox only ever sends a
         # context_id (a string) — it can never set parent_id / user_id on the
@@ -417,7 +425,14 @@ class SandboxBridge:
         # The proxy entity subclasses the domain's *EntityBase* (LightEntity,
         # SwitchEntity, …); for the framework to host it the domain
         # component itself has to be set up so its EntityComponent exists.
-        await self._ensure_domain_loaded(description.domain)
+        await self._ensure_domain_loaded(
+            description.domain,
+            # Only the entry's own integration domain may fall back to a
+            # bare EntityComponent — anything else must be a real,
+            # loadable platform domain, or a compromised sandbox could
+            # mint entities in arbitrary made-up domains.
+            allow_bare=description.domain == entry.domain,
+        )
         # Pre-create the device entry so its id is known before the proxy
         # registers; the framework's own async_get_or_create call inside
         # EntityPlatform.async_add_entities is idempotent on (identifiers,
@@ -499,7 +514,7 @@ class SandboxBridge:
                 f"entry outside group {self.group!r}; refusing to merge"
             )
 
-    async def _ensure_domain_loaded(self, domain: str) -> None:
+    async def _ensure_domain_loaded(self, domain: str, *, allow_bare: bool) -> None:
         """Make sure the domain's :class:`EntityComponent` is loaded on main."""
         components = self.hass.data.get(DATA_INSTANCES, {})
         if domain in components:
@@ -507,6 +522,14 @@ class SandboxBridge:
         # Empty config — we never own the domain ourselves; we just want
         # the EntityComponent so we can attach a proxy platform to it.
         await async_setup_component(self.hass, domain, {})
+        if domain in self.hass.data.get(DATA_INSTANCES, {}) or not allow_bare:
+            return
+        # An integration's *own* domain (sun.sun, …): its EntityComponent is
+        # only built inside its own async_setup_entry, which runs sandboxed —
+        # a bare component gives the proxies a home without running any
+        # integration code on main. EntityComponent self-registers into
+        # DATA_INSTANCES.
+        EntityComponent(_LOGGER, domain, self.hass)
 
     async def _handle_unregister_entity(
         self, msg: pb.UnregisterEntity
@@ -636,6 +659,20 @@ class SandboxBridge:
         await self._store_server.async_remove(validate_key(msg.key))
         return pb.StoreRemoveResult(ok=True)
 
+    async def _on_core_config_update(self, _event: Any) -> None:
+        """Push main's updated core config down to the sandbox."""
+        try:
+            await self.channel.push(
+                MSG_CORE_CONFIG, core_config_to_proto(self.hass.config)
+            )
+        except Exception:  # noqa: BLE001
+            # A dead channel just means the respawned sandbox will get the
+            # fresh snapshot on its next entry_setup.
+            _LOGGER.debug(
+                "SandboxBridge[%s]: core-config push failed (channel down?)",
+                self.group,
+            )
+
     @callback
     def _owned_domains(self) -> set[str]:
         """Return the set of domains this sandbox group legitimately owns.
@@ -804,6 +841,9 @@ class SandboxBridge:
         # bridge's (now dead) channel, and a respawned sandbox's
         # re-registration is skipped by the has_service() guard, so a stale
         # forwarder would fail every call until HA restarts.
+        if self._unsub_core_config is not None:
+            self._unsub_core_config()
+            self._unsub_core_config = None
         for domain, service in self._mirrored_services:
             if self.hass.services.has_service(domain, service):
                 self.hass.services.async_remove(domain, service)
diff --git a/homeassistant/components/sandbox/entity/__init__.py b/homeassistant/components/sandbox/entity/__init__.py
index 99936106b1c3..3e681a33a8a4 100644
--- a/homeassistant/components/sandbox/entity/__init__.py
+++ b/homeassistant/components/sandbox/entity/__init__.py
@@ -20,6 +20,7 @@ from homeassistant.const import EntityCategory
 from homeassistant.core import Context
 from homeassistant.helpers.device_registry import DeviceInfo
 from homeassistant.helpers.entity import Entity
+from homeassistant.helpers.typing import StateType
 
 from ..messages import decode_json_dict
 
@@ -79,12 +80,13 @@ class SandboxProxyEntity(Entity):
     @property
     @override
     def extra_state_attributes(self) -> dict[str, Any] | None:
-        """Sandbox proxies expose attributes through typed properties.
+        """Typed domain proxies expose attributes through typed properties.
 
         Anything domain-specific (``brightness``, ``hvac_mode``, …) is
         surfaced by the domain proxy's own ``@property`` declarations
-        reading from ``_state_cache``. Returning extras here would
-        duplicate those values in the state-machine attributes dict.
+        reading from ``_state_cache``. The generic fallback
+        (:class:`GenericSandboxEntity`) overrides this to pass the pushed
+        attributes through instead.
         """
         return None
 
@@ -216,6 +218,31 @@ class SandboxProxyEntity(Entity):
         )
 
 
+class GenericSandboxEntity(SandboxProxyEntity):
+    """Fallback proxy for domains without a typed module.
+
+    Hosts an integration's own-domain entities (``sun.sun``, …): no typed
+    contract exists, so the pushed state string and attribute dict pass
+    through verbatim.
+    """
+
+    @property
+    @override
+    def state(self) -> StateType:
+        """Return the pushed state verbatim."""
+        state: StateType = self._state_cache.get("state")
+        return state
+
+    @property
+    @override
+    def extra_state_attributes(self) -> dict[str, Any] | None:
+        """Return the pushed attributes verbatim."""
+        attrs = {
+            key: value for key, value in self._state_cache.items() if key != "state"
+        }
+        return attrs or None
+
+
 def build_proxy(
     bridge: SandboxBridge, description: SandboxEntityDescription
 ) -> SandboxProxyEntity:
@@ -243,7 +270,7 @@ def proxy_class_for(domain: str) -> type[SandboxProxyEntity]:
     try:
         module = importlib.import_module(f".{domain}", __package__)
     except ImportError:
-        cls = SandboxProxyEntity
+        cls = GenericSandboxEntity
     else:
         # Each proxy module defines exactly one SandboxProxyEntity subclass.
         cls = next(
@@ -254,7 +281,7 @@ def proxy_class_for(domain: str) -> type[SandboxProxyEntity]:
                 and issubclass(obj, SandboxProxyEntity)
                 and obj.__module__ == module.__name__
             ),
-            SandboxProxyEntity,
+            GenericSandboxEntity,
         )
     return _DOMAIN_PROXIES.setdefault(domain, cls)
 
diff --git a/homeassistant/components/sandbox/entity/sensor.py b/homeassistant/components/sandbox/entity/sensor.py
index f966e7122a55..7b25395115e8 100644
--- a/homeassistant/components/sandbox/entity/sensor.py
+++ b/homeassistant/components/sandbox/entity/sensor.py
@@ -1,9 +1,11 @@
 """Sandbox proxy for ``sensor`` entities."""
 
+from datetime import date, datetime
 from typing import override
 
-from homeassistant.components.sensor import SensorEntity
+from homeassistant.components.sensor import SensorDeviceClass, SensorEntity
 from homeassistant.const import ATTR_UNIT_OF_MEASUREMENT
+from homeassistant.util import dt as dt_util
 
 from . import SandboxProxyEntity
 
@@ -14,9 +16,23 @@ class SandboxSensorEntity(SandboxProxyEntity, SensorEntity):
 
     @property
     @override
-    def native_value(self) -> str | int | float | None:
-        """Return the cached state as the sensor's native value."""
-        return self._state_cache.get("state")
+    def native_value(self) -> datetime | date | str | int | float | None:
+        """Return the cached state as the sensor's native value.
+
+        The sandbox pushes the already-formatted state string; timestamp /
+        date sensors must hand ``SensorEntity`` a real ``datetime`` /
+        ``date`` back or its ``state`` property dies on ``value.tzinfo``.
+        An unparsable string (``unknown`` and friends) degrades to None.
+        """
+        value = self._state_cache.get("state")
+        if not isinstance(value, str):
+            return value
+        device_class = self.device_class
+        if device_class == SensorDeviceClass.TIMESTAMP:
+            return dt_util.parse_datetime(value)
+        if device_class == SensorDeviceClass.DATE:
+            return dt_util.parse_date(value)
+        return value
 
     @property
     @override
diff --git a/homeassistant/components/sandbox/messages.py b/homeassistant/components/sandbox/messages.py
index 066ab650604a..c90766002188 100644
--- a/homeassistant/components/sandbox/messages.py
+++ b/homeassistant/components/sandbox/messages.py
@@ -143,6 +143,10 @@ MSG_STATE_CHANGED: Final = "sandbox/state_changed"
 MSG_REGISTER_SERVICE: Final = "sandbox/register_service"
 MSG_UNREGISTER_SERVICE: Final = "sandbox/unregister_service"
 MSG_FIRE_EVENT: Final = "sandbox/fire_event"
+# main -> sandbox one-way push: live core-config update (entry_setup carries
+# the initial snapshot; this keeps a running sandbox in step when the user
+# changes the home location / units / language on main).
+MSG_CORE_CONFIG = "sandbox/core_config"
 MSG_STORE_LOAD: Final = "sandbox/store_load"
 MSG_STORE_SAVE: Final = "sandbox/store_save"
 MSG_STORE_REMOVE: Final = "sandbox/store_remove"
@@ -174,6 +178,7 @@ REGISTRY: dict[str, tuple[type[Message], type[Message] | None]] = {
         pb.UnregisterServiceResult,
     ),
     MSG_FIRE_EVENT: (pb.FireEvent, None),
+    MSG_CORE_CONFIG: (pb.CoreConfig, None),
     MSG_STORE_LOAD: (pb.StoreLoad, pb.StoreLoadResult),
     MSG_STORE_SAVE: (pb.StoreSave, pb.StoreSaveResult),
     MSG_STORE_REMOVE: (pb.StoreRemove, pb.StoreRemoveResult),
@@ -323,6 +328,29 @@ def make_entity_description(
     return msg
 
 
+def core_config_to_proto(config: Any) -> pb.CoreConfig:
+    """Snapshot a hass ``Config`` into the wire ``CoreConfig`` message.
+
+    Shared by the ``entry_setup`` payload and the live
+    ``sandbox/core_config`` push so the two can't drift.
+    """
+    msg = pb.CoreConfig(
+        latitude=config.latitude,
+        longitude=config.longitude,
+        elevation=config.elevation,
+        time_zone=config.time_zone,
+        # The unit system carries no public name accessor; core itself reads
+        # ``units._name`` when persisting (core_config.py).
+        unit_system=config.units._name,  # noqa: SLF001
+        language=config.language,
+        currency=config.currency,
+        location_name=config.location_name,
+    )
+    if config.country is not None:
+        msg.country = config.country
+    return msg
+
+
 __all__ = [
     "MSG_CALL_SERVICE",
     "MSG_ENTITY_QUERY",
@@ -345,6 +373,7 @@ __all__ = [
     "MSG_UNREGISTER_ENTITY",
     "MSG_UNREGISTER_SERVICE",
     "REGISTRY",
+    "core_config_to_proto",
     "decode_json",
     "decode_json_dict",
     "device_info_to_proto",
diff --git a/homeassistant/components/sandbox/router.py b/homeassistant/components/sandbox/router.py
index 49eeb63fd9b8..38cd030e2b47 100644
--- a/homeassistant/components/sandbox/router.py
+++ b/homeassistant/components/sandbox/router.py
@@ -29,7 +29,12 @@ from ._proto import sandbox_pb2 as pb
 from .channel import ChannelClosedError, ChannelRemoteError
 from .classifier import SandboxAssignment, classify
 from .manager import SandboxManager
-from .messages import MSG_ENTRY_SETUP, MSG_ENTRY_UNLOAD, encode_json
+from .messages import (
+    MSG_ENTRY_SETUP,
+    MSG_ENTRY_UNLOAD,
+    core_config_to_proto,
+    encode_json,
+)
 from .proxy_flow import SandboxFlowProxy
 from .sources import SandboxSourceError, async_resolve_integration_source
 
@@ -259,20 +264,7 @@ async def _entry_setup_payload(
     msg.integration_source.CopyFrom(
         await async_resolve_integration_source(hass, entry.domain)
     )
-    config = hass.config
-    core_config = msg.core_config
-    core_config.latitude = config.latitude
-    core_config.longitude = config.longitude
-    core_config.elevation = config.elevation
-    core_config.time_zone = config.time_zone
-    # The unit system carries no public name accessor; core itself reads
-    # ``units._name`` when persisting (core_config.py).
-    core_config.unit_system = config.units._name  # noqa: SLF001
-    core_config.language = config.language
-    if config.country is not None:
-        core_config.country = config.country
-    core_config.currency = config.currency
-    core_config.location_name = config.location_name
+    msg.core_config.CopyFrom(core_config_to_proto(hass.config))
     return msg
 
 
diff --git a/sandbox/hass_client/hass_client/entity_bridge.py b/sandbox/hass_client/hass_client/entity_bridge.py
index d8a8ebca51aa..8e61478fdc9f 100644
--- a/sandbox/hass_client/hass_client/entity_bridge.py
+++ b/sandbox/hass_client/hass_client/entity_bridge.py
@@ -121,6 +121,22 @@ class EntityBridge:
             EVENT_DEVICE_REGISTRY_UPDATED, self._on_device_registry_updated
         )
 
+    async def async_drain(self, *, timeout: float = 2.0) -> None:
+        """Wait until every queued slot has been written to the channel.
+
+        Test-lane hook: vanilla integration tests assume local synchronous
+        setup semantics, so the compat plugins settle the bridge after
+        ``async_block_till_done``. Bounded: an entity storm (clock-jump
+        tests leave self-rescheduling updates behind) refills the queue
+        every loop tick, and an unbounded drain would spin until the test's
+        teardown finally kills the churn.
+        """
+        deadline = asyncio.get_running_loop().time() + timeout
+        while (
+            self._pending or self._writing is not None
+        ) and asyncio.get_running_loop().time() < deadline:
+            await asyncio.sleep(0)
+
     async def async_stop(self) -> None:
         """Detach the listeners and stop the writer task."""
         for attr in (
@@ -260,6 +276,13 @@ class EntityBridge:
             )
             return None
         entry_id = _entry_id_for(entity)
+        if entry_id is None:
+            # An integration's own-domain entity (sun.sun, …) is added via a
+            # bare EntityComponent with no config-entry linkage. When exactly
+            # one loaded entry owns the entity's domain, it is that entry's.
+            entries = self.hass.config_entries.async_entries(domain)
+            if len(entries) == 1:
+                entry_id = entries[0].entry_id
         if entry_id is None:
             _LOGGER.debug(
                 "EntityBridge: %s has no owning config entry; not bridging",
diff --git a/sandbox/hass_client/hass_client/entry_runner.py b/sandbox/hass_client/hass_client/entry_runner.py
index 7a8eeb3dc594..0ccf9e982633 100644
--- a/sandbox/hass_client/hass_client/entry_runner.py
+++ b/sandbox/hass_client/hass_client/entry_runner.py
@@ -73,7 +73,7 @@ class EntryRunner:
         # sun times / distances / unit conversions against main's location
         # and units, not the bare-hass defaults. Idempotent, cheap.
         if msg.HasField("core_config"):
-            await _apply_core_config(self.hass, msg.core_config)
+            await apply_core_config(self.hass, msg.core_config)
 
         # Fetch the integration code before setup so a stateless sandbox can
         # load custom (HACS) integrations whose code isn't bundled. Built-in
@@ -205,12 +205,15 @@ class EntryRunner:
         return result
 
 
-async def _apply_core_config(hass: HomeAssistant, cfg: pb.CoreConfig) -> None:
+async def apply_core_config(hass: HomeAssistant, cfg: pb.CoreConfig) -> None:
     """Apply main's core-config snapshot to the sandbox's private hass.
 
     Direct attribute writes, deliberately not ``Config.async_update``: the
-    private hass has no Store backing and must not persist the values or fire
-    ``EVENT_CORE_CONFIG_UPDATE`` on its bus. The time zone goes through the
+    private hass has no Store backing and must not persist the values. This
+    function fires no event either — the live-update handler
+    (``SandboxRuntime._handle_core_config``) fires
+    ``EVENT_CORE_CONFIG_UPDATE`` itself, while the entry_setup snapshot is
+    applied silently before setup. The time zone goes through the
     async setter so ``dt_util``'s default timezone follows. Every value comes
     from main's own (validated) config, so a bad unit-system/time-zone name is
     a contract violation and surfaces as a failed entry_setup rather than
diff --git a/sandbox/hass_client/hass_client/messages.py b/sandbox/hass_client/hass_client/messages.py
index 066ab650604a..c90766002188 100644
--- a/sandbox/hass_client/hass_client/messages.py
+++ b/sandbox/hass_client/hass_client/messages.py
@@ -143,6 +143,10 @@ MSG_STATE_CHANGED: Final = "sandbox/state_changed"
 MSG_REGISTER_SERVICE: Final = "sandbox/register_service"
 MSG_UNREGISTER_SERVICE: Final = "sandbox/unregister_service"
 MSG_FIRE_EVENT: Final = "sandbox/fire_event"
+# main -> sandbox one-way push: live core-config update (entry_setup carries
+# the initial snapshot; this keeps a running sandbox in step when the user
+# changes the home location / units / language on main).
+MSG_CORE_CONFIG = "sandbox/core_config"
 MSG_STORE_LOAD: Final = "sandbox/store_load"
 MSG_STORE_SAVE: Final = "sandbox/store_save"
 MSG_STORE_REMOVE: Final = "sandbox/store_remove"
@@ -174,6 +178,7 @@ REGISTRY: dict[str, tuple[type[Message], type[Message] | None]] = {
         pb.UnregisterServiceResult,
     ),
     MSG_FIRE_EVENT: (pb.FireEvent, None),
+    MSG_CORE_CONFIG: (pb.CoreConfig, None),
     MSG_STORE_LOAD: (pb.StoreLoad, pb.StoreLoadResult),
     MSG_STORE_SAVE: (pb.StoreSave, pb.StoreSaveResult),
     MSG_STORE_REMOVE: (pb.StoreRemove, pb.StoreRemoveResult),
@@ -323,6 +328,29 @@ def make_entity_description(
     return msg
 
 
+def core_config_to_proto(config: Any) -> pb.CoreConfig:
+    """Snapshot a hass ``Config`` into the wire ``CoreConfig`` message.
+
+    Shared by the ``entry_setup`` payload and the live
+    ``sandbox/core_config`` push so the two can't drift.
+    """
+    msg = pb.CoreConfig(
+        latitude=config.latitude,
+        longitude=config.longitude,
+        elevation=config.elevation,
+        time_zone=config.time_zone,
+        # The unit system carries no public name accessor; core itself reads
+        # ``units._name`` when persisting (core_config.py).
+        unit_system=config.units._name,  # noqa: SLF001
+        language=config.language,
+        currency=config.currency,
+        location_name=config.location_name,
+    )
+    if config.country is not None:
+        msg.country = config.country
+    return msg
+
+
 __all__ = [
     "MSG_CALL_SERVICE",
     "MSG_ENTITY_QUERY",
@@ -345,6 +373,7 @@ __all__ = [
     "MSG_UNREGISTER_ENTITY",
     "MSG_UNREGISTER_SERVICE",
     "REGISTRY",
+    "core_config_to_proto",
     "decode_json",
     "decode_json_dict",
     "device_info_to_proto",
diff --git a/sandbox/hass_client/hass_client/sandbox/__init__.py b/sandbox/hass_client/hass_client/sandbox/__init__.py
index 85a071687251..d7a0abe01b50 100644
--- a/sandbox/hass_client/hass_client/sandbox/__init__.py
+++ b/sandbox/hass_client/hass_client/sandbox/__init__.py
@@ -35,10 +35,11 @@ from hass_client.approved_domains import ApprovedDomains
 from hass_client.channel import Channel
 from hass_client.codec_protobuf import ProtobufCodec
 from hass_client.entity_bridge import EntityBridge
-from hass_client.entry_runner import EntryRunner
+from hass_client.entry_runner import EntryRunner, apply_core_config
 from hass_client.event_mirror import EventMirror
 from hass_client.flow_runner import FlowRunner
 from hass_client.messages import (
+    MSG_CORE_CONFIG,
     MSG_GET_TRANSLATIONS,
     MSG_PING,
     MSG_READY,
@@ -47,7 +48,10 @@ from hass_client.messages import (
 )
 from hass_client.sandbox_bridge import ChannelSandboxBridge
 from hass_client.service_mirror import ServiceMirror
-from homeassistant.const import EVENT_HOMEASSISTANT_FINAL_WRITE
+from homeassistant.const import (
+    EVENT_CORE_CONFIG_UPDATE,
+    EVENT_HOMEASSISTANT_FINAL_WRITE,
+)
 from homeassistant.core import CoreState, HomeAssistant
 from homeassistant.helpers import json as json_helper, restore_state
 from homeassistant.helpers.sandbox_context import current_sandbox
@@ -121,6 +125,16 @@ class SandboxRuntime:
         """The runtime's control channel, once ``run()`` has started it."""
         return self._channel
 
+    @property
+    def hass(self) -> HomeAssistant | None:
+        """The sandbox-private hass, once ``run()`` has created it."""
+        return self._flow_runner.hass if self._flow_runner is not None else None
+
+    @property
+    def entity_bridge(self) -> EntityBridge | None:
+        """The runtime's entity bridge, once ``run()`` has created it."""
+        return self._entity_bridge
+
     def request_shutdown(self) -> None:
         """Request a graceful shutdown of the runtime."""
         if self._shutdown is None:
@@ -202,6 +216,7 @@ class SandboxRuntime:
             self._channel.register(
                 MSG_GET_TRANSLATIONS, self._handle_get_translations
             )
+            self._channel.register(MSG_CORE_CONFIG, self._handle_core_config)
             self._flow_runner.register(self._channel)
             self._entry_runner.register(self._channel)
             self._entity_bridge.register(self._channel)
@@ -304,6 +319,22 @@ class SandboxRuntime:
             result.strings = encode_json(strings)
         return result
 
+    async def _handle_core_config(self, msg: pb.CoreConfig) -> None:
+        """Apply a live core-config update pushed from main.
+
+        ``entry_setup`` carries the initial snapshot; this keeps a running
+        sandbox in step when the user changes the home location / units /
+        language on main. Fires ``EVENT_CORE_CONFIG_UPDATE`` on the private
+        bus so integrations recompute exactly as they would locally (sun
+        re-derives its observer, coordinators re-localize).
+        """
+        flow_runner = self._flow_runner
+        if flow_runner is None:
+            return
+        hass = flow_runner.hass
+        await apply_core_config(hass, msg)
+        hass.bus.async_fire(EVENT_CORE_CONFIG_UPDATE)
+
     async def _run_graceful_shutdown(self) -> pb.ShutdownResult:
         """Unload every loaded entry and snapshot RestoreEntity state.
 
diff --git a/sandbox/hass_client/hass_client/testing/pytest_plugin.py b/sandbox/hass_client/hass_client/testing/pytest_plugin.py
index 3ca497a8b39f..ad24186bcb87 100644
--- a/sandbox/hass_client/hass_client/testing/pytest_plugin.py
+++ b/sandbox/hass_client/hass_client/testing/pytest_plugin.py
@@ -177,6 +177,51 @@ class _InProcessSandboxProcess:
         return True
 
 
+def _install_settling_block_till_done(
+    hass: HomeAssistant, runtime: SandboxRuntime, mgr_channel: Any
+) -> None:
+    """Make main's ``async_block_till_done`` settle the sandbox round-trip.
+
+    Vanilla integration tests assume local synchronous semantics: after
+    ``await hass.async_block_till_done()`` they expect entities and states
+    to be visible. With a sandbox in the middle, registrations and pushes
+    are still in flight on the (same-loop) channel and the entity bridge's
+    single-writer queue. Iterate until a pass sees the private hass idle,
+    the bridge queue drained, and no channel dispatch task in flight, then
+    settle main once more for anything late pushes scheduled.
+    """
+    original = hass.async_block_till_done
+
+    async def settled(wait_background_tasks: bool = False) -> None:
+        await original(wait_background_tasks=wait_background_tasks)
+        rt_channel = runtime.channel
+        # Wall-clock bound, not just an iteration cap: a pathological private
+        # hass (timer churn from clock-jump tests) must cost each
+        # block_till_done a couple of seconds at worst, not minutes.
+        deadline = asyncio.get_running_loop().time() + 2.0
+        for _ in range(200):
+            if asyncio.get_running_loop().time() > deadline:
+                break
+            sandbox_hass = runtime.hass
+            bridge = runtime.entity_bridge
+            if sandbox_hass is not None:
+                await sandbox_hass.async_block_till_done()
+            if bridge is not None:
+                await bridge.async_drain()
+            if not mgr_channel._inflight and (  # noqa: SLF001
+                rt_channel is None or not rt_channel._inflight  # noqa: SLF001
+            ):
+                await asyncio.sleep(0)
+                if not mgr_channel._inflight and (  # noqa: SLF001
+                    rt_channel is None or not rt_channel._inflight  # noqa: SLF001
+                ):
+                    break
+            await asyncio.sleep(0)
+        await original(wait_background_tasks=wait_background_tasks)
+
+    hass.async_block_till_done = settled  # type: ignore[method-assign]
+
+
 async def async_setup_inprocess_sandbox(
     hass: HomeAssistant,
     *,
@@ -240,6 +285,10 @@ async def async_setup_inprocess_sandbox(
     process = _InProcessSandboxProcess(group, mgr_channel)
     manager._sandboxes[group] = process  # noqa: SLF001
 
+    # Tests observe the bridge through main's block_till_done — teach it
+    # to settle the whole sandbox round-trip first.
+    _install_settling_block_till_done(hass, runtime, mgr_channel)
+
     # Mirror what the integration's ``_on_channel_ready`` does when the
     # real ``SandboxProcess`` opens its channel — register the bridge.
     data.bridges[group] = async_create_bridge(hass, group=group, channel=mgr_channel)
diff --git a/sandbox/hass_client/tests/test_entity_bridge.py b/sandbox/hass_client/tests/test_entity_bridge.py
index cd20f6712497..e77c98da9962 100644
--- a/sandbox/hass_client/tests/test_entity_bridge.py
+++ b/sandbox/hass_client/tests/test_entity_bridge.py
@@ -350,6 +350,66 @@ async def test_state_push_serialises_datetime_attributes(
     await bridge.async_stop()
 
 
+async def test_register_attributes_sole_domain_entry_without_linkage(
+    channels: tuple[Channel, Channel], hass_with_demo_component
+) -> None:
+    """An entity with no registry/platform linkage falls back to the domain's entry.
+
+    ``registry_entry`` is None and ``platform.config_entry`` is None (an
+    own-domain entity on a bare EntityComponent) — when exactly one loaded
+    config entry owns the entity's domain, the registration is attributed
+    to it instead of being skipped.
+    """
+    main, sandbox = channels
+    hass, component = hass_with_demo_component
+
+    register_calls: list[pb.EntityDescription] = []
+
+    async def _on_register(msg: pb.EntityDescription) -> pb.RegisterEntityResult:
+        register_calls.append(msg)
+        return pb.RegisterEntityResult(entity_id="demo.lamp_main")
+
+    main.register("sandbox/register_entity", _on_register)
+    main.start()
+    sandbox.start()
+
+    config_entry = ConfigEntry(
+        version=1,
+        minor_version=1,
+        domain="demo",
+        title="Demo",
+        data={},
+        options={},
+        source="user",
+        unique_id=None,
+        discovery_keys={},
+        subentries_data=(),
+    )
+    hass.config_entries._entries[config_entry.entry_id] = config_entry  # noqa: SLF001
+
+    class _UnlinkedEntity(_FakeEntity):
+        @property
+        def platform(self) -> Any:
+            # No config-entry linkage anywhere: registry_entry is None
+            # (inherited) and the platform carries no config_entry either.
+            mock = MagicMock()
+            mock.config_entry = None
+            mock.domain = "demo"
+            return mock
+
+    entity = _UnlinkedEntity()
+    component._entities[entity.entity_id] = entity  # noqa: SLF001
+
+    bridge = EntityBridge(hass)
+    bridge.register(sandbox)
+    await _register_initial(bridge, hass, entity)
+
+    assert len(register_calls) == 1
+    assert register_calls[0].entry_id == config_entry.entry_id
+
+    await bridge.async_stop()
+
+
 async def _register_initial(bridge: EntityBridge, hass: Any, entity: Entity) -> None:
     """Drive the first state-change so ``entity`` is tracked + registered."""
     now = datetime.now(tz=datetime.now().astimezone().tzinfo)
diff --git a/sandbox/hass_client/tests/test_sandbox_runtime.py b/sandbox/hass_client/tests/test_sandbox_runtime.py
index 2333be9db163..18c05bcae7ca 100644
--- a/sandbox/hass_client/tests/test_sandbox_runtime.py
+++ b/sandbox/hass_client/tests/test_sandbox_runtime.py
@@ -11,11 +11,15 @@ import asyncio
 from hass_client._proto import sandbox_pb2 as pb
 from hass_client.channel import Channel, ChannelRemoteError
 from hass_client.codec_protobuf import ProtobufCodec
-from hass_client.messages import MSG_READY
+from hass_client.messages import MSG_CORE_CONFIG, MSG_READY
 from hass_client.sandbox import SandboxRuntime
 from hass_client.sandbox.__main__ import _build_parser
 import pytest
 
+from homeassistant.const import EVENT_CORE_CONFIG_UPDATE
+from homeassistant.core import Event, callback
+from homeassistant.util import dt as dt_util
+
 
 async def _noop_channel_factory() -> Channel | None:
     """Channel factory that opens no channel — for in-process shutdown tests."""
@@ -125,6 +129,78 @@ async def test_handlers_registered_before_ready(
     capsys.readouterr()
 
 
+async def test_core_config_push_updates_private_hass(
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    """A live ``sandbox/core_config`` push lands on the private hass.
+
+    The config values must be applied AND ``EVENT_CORE_CONFIG_UPDATE`` must
+    fire on the private bus, so sandboxed integrations recompute exactly as
+    they would locally.
+    """
+    main_channel, sandbox_channel = _make_channel_pair()
+    ready_seen = asyncio.Event()
+
+    async def _on_ready(_payload: object) -> None:
+        ready_seen.set()
+
+    main_channel.register(MSG_READY, _on_ready)
+    main_channel.start()
+
+    async def _channel_factory() -> Channel:
+        return sandbox_channel
+
+    runtime = SandboxRuntime(
+        url="ws://x",
+        group="custom",
+        channel_factory=_channel_factory,
+    )
+
+    task = asyncio.create_task(runtime.run())
+    original_tz = dt_util.get_default_time_zone()
+    try:
+        await asyncio.wait_for(ready_seen.wait(), timeout=5.0)
+        flow_runner = runtime._flow_runner  # noqa: SLF001
+        assert flow_runner is not None
+        hass = flow_runner.hass
+
+        events: list[Event] = []
+
+        @callback
+        def _on_core_config_update(event: Event) -> None:
+            events.append(event)
+
+        # Subscribe BEFORE pushing so the fired event cannot be missed.
+        hass.bus.async_listen(EVENT_CORE_CONFIG_UPDATE, _on_core_config_update)
+
+        await main_channel.push(
+            MSG_CORE_CONFIG,
+            pb.CoreConfig(
+                latitude=52.3731,
+                longitude=4.8926,
+                time_zone="Europe/Amsterdam",
+            ),
+        )
+        for _ in range(100):
+            if events:
+                break
+            await asyncio.sleep(0.01)
+
+        assert hass.config.latitude == 52.3731
+        assert hass.config.longitude == 4.8926
+        assert hass.config.time_zone == "Europe/Amsterdam"
+        assert len(events) == 1
+    finally:
+        # The time-zone setter updates dt_util's process-global default —
+        # restore it so the rest of the suite is unaffected.
+        dt_util.set_default_time_zone(original_tz)
+        runtime.request_shutdown()
+        await asyncio.wait_for(task, timeout=5.0)
+        await main_channel.close()
+        await sandbox_channel.close()
+    capsys.readouterr()
+
+
 async def test_runtime_starts_in_locked_down_sharing_posture(
     capsys: pytest.CaptureFixture[str],
 ) -> None:
diff --git a/sandbox/plans/plan-review-overhead.md b/sandbox/plans/plan-review-overhead.md
index 3f21ee5ecf9c..6b50acda6cc6 100644
--- a/sandbox/plans/plan-review-overhead.md
+++ b/sandbox/plans/plan-review-overhead.md
@@ -352,17 +352,25 @@ pops it).
 
 ## Discovered during execution (open, not in the original findings)
 
-- **Timestamp sensor proxies break on state fidelity**: a sandboxed sensor
-  with `device_class: timestamp` pushes its state as a string, but
-  `SensorEntity.state` requires a `datetime` (`AttributeError: 'str' object
-  has no attribute 'tzinfo'` kills the proxy's entity add). Blocks several
-  sun compat tests even after core-config mirroring (E3). Fix shape: the
-  sensor proxy should rebuild `native_value` typed from the pushed state
-  for timestamp/date device classes.
-- The compat lane (now real, E2) reports 8 failing sun tests — the honest
-  baseline replacing the no-op 99.97%. Failure notes: listener-count
-  assertions see the proxy architecture; unload/remove semantics; recorder
-  attribute exclusion; the timestamp issue above.
+- ~~**Timestamp sensor proxies break on state fidelity**~~ FIXED: the
+  sensor proxy rebuilds `native_value` as `datetime`/`date` for
+  timestamp/date device classes.
+- Fixed alongside it (same follow-up batch): own-domain entities
+  (`sun.sun`) bridge via a bare main-side `EntityComponent` (restricted to
+  the entry's own domain) + a `GenericSandboxEntity` passing state and
+  attributes through verbatim + single-entry domain attribution in
+  `_describe`; live core-config propagation (`sandbox/core_config` push —
+  main's location/unit changes reach a running sandbox and re-fire
+  `EVENT_CORE_CONFIG_UPDATE` there); the in-proc lane settles the full
+  bridge round-trip inside `async_block_till_done` (bounded, so clock-jump
+  entity storms cost ≤ ~2 s per call, not minutes).
+- Sun compat: 8 failed → **4 failed / 97 passed**. The residual four are
+  inherent white-box divergences, not bugs: two tests assert the raw
+  registry `unique_id` (proxies namespace as `<domain>:<unique_id>` for
+  collision safety), one pre-seeds a registry row and expects the
+  integration's setup-time cleanup to touch main's registry (it runs on the
+  private one), and recorder `exclude_attributes` needs the integration's
+  recorder module on main (real gap, tracked).
 
 ## Suggested execution order
 
diff --git a/sandbox/run_compat.py b/sandbox/run_compat.py
index 497d39da8088..b7587bee933f 100644
--- a/sandbox/run_compat.py
+++ b/sandbox/run_compat.py
@@ -24,6 +24,7 @@ Usage::
 # ruff: noqa: INP001, T201, S108, PERF401
 
 import argparse
+from concurrent.futures import ThreadPoolExecutor
 import csv
 from dataclasses import dataclass
 import os
@@ -236,6 +237,15 @@ def main(argv: list[str] | None = None) -> int:
         default="inprocess",
         help="Which sandbox plugin to drive (default: inprocess).",
     )
+    parser.add_argument(
+        "--jobs",
+        type=int,
+        default=1,
+        help=(
+            "Concurrent pytest subprocesses (default: 1). Each runs one"
+            " integration's suite; 4-8 is reasonable on a workstation."
+        ),
+    )
     parser.add_argument(
         "--timeout",
         type=float,
@@ -265,18 +275,26 @@ def main(argv: list[str] | None = None) -> int:
 
     start = time.monotonic()
     results: list[Result] = []
-    for idx, integration in enumerate(integrations, 1):
-        result = run_one(integration, plugin, timeout=args.timeout)
-        results.append(result)
-        elapsed = time.monotonic() - start
-        rate = idx / elapsed if elapsed > 0 else 0
-        eta_minutes = (total - idx) / rate / 60 if rate else 0
-        print(
-            f"[{idx}/{total}] {integration} -> {result.status}"
-            f" ({result.passed}p/{result.failed}f/{result.errors}e/{result.skipped}s)"
-            f" | ETA: {eta_minutes:.0f}m",
-            flush=True,
-        )
+    # Results in input order regardless of completion order; progress prints
+    # as each integration finishes.
+    with ThreadPoolExecutor(max_workers=max(1, args.jobs)) as pool:
+        futures = [
+            pool.submit(run_one, integration, plugin, timeout=args.timeout)
+            for integration in integrations
+        ]
+        by_future = dict(zip(futures, integrations, strict=True))
+        for done, future in enumerate(futures, 1):
+            result = future.result()
+            results.append(result)
+            elapsed = time.monotonic() - start
+            rate = done / elapsed if elapsed > 0 else 0
+            eta_minutes = (total - done) / rate / 60 if rate else 0
+            print(
+                f"[{done}/{total}] {by_future[future]} -> {result.status}"
+                f" ({result.passed}p/{result.failed}f/{result.errors}e/{result.skipped}s)"
+                f" | ETA: {eta_minutes:.0f}m",
+                flush=True,
+            )
 
     write_csv(results, args.csv)
     write_report(results, plugin, args.report)
diff --git a/tests/components/sandbox/test_bridge.py b/tests/components/sandbox/test_bridge.py
index 3793171a8d28..5e83867db3d5 100644
--- a/tests/components/sandbox/test_bridge.py
+++ b/tests/components/sandbox/test_bridge.py
@@ -17,7 +17,7 @@ from homeassistant.components.sandbox.messages import (
 )
 from homeassistant.components.sandbox.service_forwarder import translate_remote_error
 from homeassistant.config_entries import ConfigEntry
-from homeassistant.const import STATE_ON
+from homeassistant.const import EVENT_CORE_CONFIG_UPDATE, STATE_ON
 from homeassistant.core import Context, HomeAssistant, callback
 from homeassistant.exceptions import HomeAssistantError
 from homeassistant.helpers import device_registry as dr, entity_registry as er
@@ -541,6 +541,101 @@ async def test_register_entity_auto_loads_domain_component(
     assert "switch" in hass.config.components
 
 
+async def test_register_entity_own_domain_gets_bare_component_passthrough(
+    hass: HomeAssistant,
+) -> None:
+    """An own-domain entity works even when the domain can't load on main.
+
+    ``mysun.sun`` for an entry owning domain ``mysun``: no integration of
+    that name exists on main, so ``async_setup_component`` fails — the
+    bridge falls back to a bare EntityComponent and the generic proxy
+    surfaces the pushed state and attributes verbatim.
+    """
+    entry = MockConfigEntry(domain="mysun", title="My Sun", sandbox="built-in")
+    entry.add_to_hass(hass)
+    _bridge, main_channel, sandbox_channel = await _wire(hass)
+
+    try:
+        result = await sandbox_channel.call(
+            "sandbox/register_entity",
+            make_entity_description(
+                entry_id=entry.entry_id,
+                domain="mysun",
+                sandbox_entity_id="mysun.sun",
+                unique_id="sandbox-sun",
+                initial_state="above_horizon",
+                initial_attributes={"elevation": 12.5, "azimuth": 180.25},
+            ),
+        )
+    finally:
+        await main_channel.close()
+        await sandbox_channel.close()
+
+    assert result.entity_id.startswith("mysun.")
+    state = hass.states.get(result.entity_id)
+    assert state is not None
+    assert state.state == "above_horizon"
+    assert state.attributes["elevation"] == 12.5
+    assert state.attributes["azimuth"] == 180.25
+
+
+async def test_register_entity_bare_component_foreign_domain_rejected(
+    hass: HomeAssistant,
+) -> None:
+    """The bare-EntityComponent fallback is own-domain only.
+
+    A made-up entity domain that differs from the entry's domain must not
+    get a minted component — the registration errors and no proxy lands.
+    """
+    entry = MockConfigEntry(domain="generic", title="Generic", sandbox="built-in")
+    entry.add_to_hass(hass)
+    bridge, main_channel, sandbox_channel = await _wire(hass)
+
+    try:
+        with pytest.raises(ChannelRemoteError, match="no EntityComponent"):
+            await sandbox_channel.call(
+                "sandbox/register_entity",
+                make_entity_description(
+                    entry_id=entry.entry_id,
+                    domain="madeup",
+                    sandbox_entity_id="madeup.widget",
+                    unique_id="sandbox-widget",
+                    initial_state="on",
+                ),
+            )
+    finally:
+        await main_channel.close()
+        await sandbox_channel.close()
+
+    assert "madeup.widget" not in bridge._entities
+    assert hass.states.async_entity_ids("madeup") == []
+
+
+async def test_core_config_update_pushed_to_sandbox(hass: HomeAssistant) -> None:
+    """A main-side core-config change pushes ``sandbox/core_config`` live."""
+    _bridge, main_channel, sandbox_channel = await _wire(hass)
+    pushes: list[pb.CoreConfig] = []
+
+    async def _on_core_config(msg: pb.CoreConfig) -> None:
+        pushes.append(msg)
+
+    sandbox_channel.register("sandbox/core_config", _on_core_config)
+
+    try:
+        hass.config.latitude = 52.3731
+        hass.bus.async_fire(EVENT_CORE_CONFIG_UPDATE)
+        for _ in range(50):
+            if pushes:
+                break
+            await asyncio.sleep(0)
+    finally:
+        await main_channel.close()
+        await sandbox_channel.close()
+
+    assert len(pushes) == 1
+    assert pushes[0].latitude == 52.3731
+
+
 async def test_register_service_installs_forwarder(hass: HomeAssistant) -> None:
     """A sandbox-registered service appears on main and forwards calls back."""
     MockConfigEntry(
diff --git a/tests/components/sandbox/test_domain_proxies.py b/tests/components/sandbox/test_domain_proxies.py
index 51252fd55b40..3955bd5a1216 100644
--- a/tests/components/sandbox/test_domain_proxies.py
+++ b/tests/components/sandbox/test_domain_proxies.py
@@ -20,6 +20,8 @@ still ships a proxy for symmetry).
 from __future__ import annotations
 
 import asyncio
+from collections.abc import Callable
+from datetime import date, datetime
 from typing import Any
 
 import pytest
@@ -34,6 +36,7 @@ from homeassistant.components.sandbox.messages import (
 )
 from homeassistant.config_entries import ConfigEntry
 from homeassistant.core import HomeAssistant
+from homeassistant.util import dt as dt_util
 
 from ._helpers import make_channel_pair
 
@@ -423,6 +426,54 @@ async def test_phase13_proxy_smoke(
         assert decode_json_dict(calls[0].target) == {"entity_id": [sandbox_entity_id]}
 
 
+@pytest.mark.parametrize(
+    ("device_class", "pushed_state", "parse"),
+    [
+        pytest.param(
+            "timestamp",
+            "2026-05-23T10:30:00+00:00",
+            dt_util.parse_datetime,
+            id="timestamp",
+        ),
+        pytest.param("date", "2026-05-23", dt_util.parse_date, id="date"),
+    ],
+)
+async def test_sensor_timestamp_and_date_states_surface(
+    hass: HomeAssistant,
+    entry: ConfigEntry,
+    device_class: str,
+    pushed_state: str,
+    parse: Callable[[str], datetime | date | None],
+) -> None:
+    """A timestamp/date sensor's pushed ISO string surfaces a working state.
+
+    ``SensorEntity.state`` needs a real ``datetime`` / ``date`` back from
+    ``native_value`` — handing it the raw pushed string used to die on
+    ``'str' object has no attribute 'tzinfo'``.
+    """
+    _bridge, main_channel, sandbox_channel = await _wire(hass)
+
+    payload = make_entity_description(
+        entry_id=entry.entry_id,
+        domain="sensor",
+        sandbox_entity_id=f"sensor.synthetic_{device_class}",
+        unique_id=f"sandbox-sensor-{device_class}",
+        device_class=device_class,
+        initial_state=pushed_state,
+    )
+
+    try:
+        result = await sandbox_channel.call("sandbox/register_entity", payload)
+    finally:
+        await main_channel.close()
+        await sandbox_channel.close()
+
+    state = hass.states.get(result.entity_id)
+    assert state is not None
+    assert parse(state.state) is not None
+    assert parse(state.state) == parse(pushed_state)
+
+
 async def test_upsert_clears_dropped_device_class(
     hass: HomeAssistant, entry: ConfigEntry
 ) -> None: