diff --git a/server/src/ledgrab/api/routes/devices.py b/server/src/ledgrab/api/routes/devices.py
index 936266d..f704479 100644
--- a/server/src/ledgrab/api/routes/devices.py
+++ b/server/src/ledgrab/api/routes/devices.py
@@ -42,6 +42,30 @@ logger = get_logger(__name__)
 router = APIRouter()
 
 
+def _sanitize_url_for_log(url: str) -> str:
+    """Strip userinfo + fragment from a URL so secrets don't reach logs.
+
+    The pair endpoint receives a user-supplied URL on every call; if a
+    future driver ever accepts ``scheme://user:pass@host`` form the
+    credentials would land in logs without this guard.
+    """
+    if not url:
+        return ""
+    try:
+        from urllib.parse import urlparse, urlunparse
+
+        parsed = urlparse(url)
+        # urlparse stores userinfo in `netloc`; rebuild without it.
+        if parsed.hostname:
+            netloc = parsed.hostname
+            if parsed.port:
+                netloc = f"{netloc}:{parsed.port}"
+            return urlunparse((parsed.scheme, netloc, parsed.path, parsed.params, parsed.query, ""))
+    except ValueError:
+        pass
+    return url
+
+
 def _device_to_response(device) -> DeviceResponse:
     """Convert a Device to DeviceResponse."""
     return DeviceResponse(
@@ -66,15 +90,14 @@ def _device_to_response(device) -> DeviceResponse:
         ddp_color_order=device.ddp_color_order,
         espnow_peer_mac=device.espnow_peer_mac,
         espnow_channel=device.espnow_channel,
-        hue_username=device.hue_username,
-        hue_client_key=device.hue_client_key,
+        hue_paired=bool(device.hue_username and device.hue_client_key),
         hue_entertainment_group_id=device.hue_entertainment_group_id,
         yeelight_min_interval_ms=device.yeelight_min_interval_ms,
         wiz_min_interval_ms=device.wiz_min_interval_ms,
         lifx_min_interval_ms=device.lifx_min_interval_ms,
         govee_min_interval_ms=device.govee_min_interval_ms,
         opc_channel=device.opc_channel,
-        nanoleaf_token=device.nanoleaf_token,
+        nanoleaf_paired=bool(device.nanoleaf_token),
         nanoleaf_min_interval_ms=device.nanoleaf_min_interval_ms,
         spi_speed_hz=device.spi_speed_hz,
         spi_led_type=device.spi_led_type,
@@ -333,16 +356,23 @@ async def pair_device(
     except ValueError as exc:
         raise HTTPException(status_code=422, detail=str(exc))
     except Exception as exc:
+        # Strip userinfo before logging so a `scheme://user:pass@host` URL
+        # never lands in the logs (no shipped driver uses userinfo today,
+        # but the pattern is a foot-gun for the next driver author --
+        # caught by review MEDIUM #9). Also keep exc_info=False so a
+        # provider stack trace that may include response bytes from a
+        # hostile receiver doesn't end up in the file either.
+        safe_url = _sanitize_url_for_log(body.url)
         logger.warning(
-            "Pairing failed for %s at %s: %s",
+            "Pairing failed for %s at %s: %s: %s",
             body.device_type,
-            body.url,
+            safe_url,
+            type(exc).__name__,
             exc,
-            exc_info=True,
         )
         raise HTTPException(
             status_code=502,
-            detail=f"Pairing failed for {body.device_type} at {body.url}.",
+            detail=f"Pairing failed for {body.device_type} at {safe_url}.",
         )
 
     if not isinstance(fields, dict):
@@ -520,16 +550,21 @@ async def update_device(
         existing = store.get_device(device_id)
         is_group = existing.device_type == "group"
 
-        # Normalize a WLED URL the same way we do on create: infer http/https
-        # when the user typed a bare host. Done via a local rather than
-        # mutating the request DTO so the input is preserved for any future
-        # caller that inspects it.
+        # Normalize URL the same way we do on create:
+        #   * always rstrip trailing slashes (so PUT-with-trailing-/ matches
+        #     POST-with-trailing-/ in the stored value -- caught by review HIGH #6)
+        #   * only WLED gets http/https scheme inference; other schemes
+        #     (yeelight://, lifx://, opc://, ddp://, …) pass through.
+        # Done via a local rather than mutating the request DTO so the
+        # input is preserved for any future caller that inspects it.
         normalized_url = update_data.url
-        if existing.device_type == "wled" and update_data.url:
-            raw_url = update_data.url.rstrip("/")
-            normalized_url = infer_http_scheme(raw_url)
-            if normalized_url != raw_url:
-                logger.debug("Inferred WLED URL scheme: %r -> %r", raw_url, normalized_url)
+        if update_data.url:
+            normalized_url = update_data.url.rstrip("/")
+            if existing.device_type == "wled":
+                inferred = infer_http_scheme(normalized_url)
+                if inferred != normalized_url:
+                    logger.debug("Inferred WLED URL scheme: %r -> %r", normalized_url, inferred)
+                normalized_url = inferred
 
         # Group-only field overrides (led_count auto-recompute) are accumulated
         # here too so the update_data Pydantic model is not mutated in place.
diff --git a/server/src/ledgrab/api/schemas/devices.py b/server/src/ledgrab/api/schemas/devices.py
index 3e8bd9f..b0e9e9a 100644
--- a/server/src/ledgrab/api/schemas/devices.py
+++ b/server/src/ledgrab/api/schemas/devices.py
@@ -409,8 +409,14 @@ class DeviceResponse(BaseModel):
     ddp_color_order: int = Field(default=1, description="DDP color order code (1 = RGB)")
     espnow_peer_mac: str = Field(default="", description="ESP-NOW peer MAC address")
     espnow_channel: int = Field(default=1, description="ESP-NOW WiFi channel")
-    hue_username: str = Field(default="", description="Hue bridge username")
-    hue_client_key: str = Field(default="", description="Hue entertainment client key")
+    hue_paired: bool = Field(
+        default=False,
+        description=(
+            "Whether the Hue bridge has been paired (i.e. a username/client_key "
+            "is on file). The actual credentials are intentionally not exposed "
+            "in the response -- to re-pair, delete and re-add the device."
+        ),
+    )
     hue_entertainment_group_id: str = Field(default="", description="Hue entertainment group ID")
     yeelight_min_interval_ms: int = Field(
         default=500, description="Yeelight client-side rate limit in ms"
@@ -419,7 +425,14 @@ class DeviceResponse(BaseModel):
     lifx_min_interval_ms: int = Field(default=50, description="LIFX client-side rate limit in ms")
     govee_min_interval_ms: int = Field(default=50, description="Govee client-side rate limit in ms")
     opc_channel: int = Field(default=0, description="OPC channel (0 = broadcast to all)")
-    nanoleaf_token: str = Field(default="", description="Nanoleaf auth token")
+    nanoleaf_paired: bool = Field(
+        default=False,
+        description=(
+            "Whether the Nanoleaf auth token has been issued by the pairing "
+            "handshake. The token itself is intentionally not exposed in the "
+            "response -- to re-pair, delete and re-add the device."
+        ),
+    )
     nanoleaf_min_interval_ms: int = Field(
         default=100, description="Nanoleaf client-side rate limit in ms"
     )
diff --git a/server/src/ledgrab/core/devices/ddp_provider.py b/server/src/ledgrab/core/devices/ddp_provider.py
index e6d8ddc..045a732 100644
--- a/server/src/ledgrab/core/devices/ddp_provider.py
+++ b/server/src/ledgrab/core/devices/ddp_provider.py
@@ -5,6 +5,7 @@ from __future__ import annotations
 from typing import TYPE_CHECKING, List
 
 from ledgrab.core.devices.ddp_led_client import DDPLEDClient, parse_ddp_url
+from ledgrab.utils.net_classify import validate_lan_host
 from ledgrab.core.devices.led_client import (
     DeviceHealth,
     DiscoveredDevice,
@@ -58,6 +59,7 @@ class DDPDeviceProvider(LEDDeviceProvider):
             host, port = parse_ddp_url(url)
         except ValueError as exc:
             raise ValueError(f"Invalid DDP URL: {exc}") from exc
+        validate_lan_host(host)
         logger.info("DDP device URL validated: host=%s port=%d", host, port)
         return {}
 
diff --git a/server/src/ledgrab/core/devices/govee_client.py b/server/src/ledgrab/core/devices/govee_client.py
index b892b7f..95ee14b 100644
--- a/server/src/ledgrab/core/devices/govee_client.py
+++ b/server/src/ledgrab/core/devices/govee_client.py
@@ -43,6 +43,25 @@ _DISCOVERY_REQUEST = json.dumps(
 ).encode("utf-8")
 
 
+# Govee mandates listening on port 4002 for scan replies; the OS only lets
+# one process / socket own it at a time. Serialize concurrent discover
+# calls (e.g. two browser tabs hitting /discover at once) so the second
+# caller waits its turn instead of getting an empty result.
+_DISCOVERY_LOCK: asyncio.Lock | None = None
+
+
+def _discovery_lock() -> asyncio.Lock:
+    """Return a module-level asyncio.Lock, created lazily.
+
+    Can't construct at import-time because asyncio.Lock binds to the
+    running event loop and module import may precede loop creation.
+    """
+    global _DISCOVERY_LOCK
+    if _DISCOVERY_LOCK is None:
+        _DISCOVERY_LOCK = asyncio.Lock()
+    return _DISCOVERY_LOCK
+
+
 def parse_govee_url(url: str) -> str:
     """Pull the host out of ``govee://host`` or bare ``host``."""
     if not url:
@@ -309,11 +328,20 @@ async def discover_govee_devices(timeout: float = 2.0) -> List[dict]:
     Returns a list of ``{"ip": ..., "device": ..., "sku": ..., "version": ...}``
     dicts. Multicast / receive failures (no network, firewall, no LAN-enabled
     bulbs) yield an empty list rather than raising.
+
+    Concurrent invocations are serialized via a module-level
+    ``asyncio.Lock`` so two callers don't race on the protocol-mandated
+    response port 4002.
     """
+    async with _discovery_lock():
+        return await _discover_govee_devices_locked(timeout)
+
+
+async def _discover_govee_devices_locked(timeout: float) -> List[dict]:
     loop = asyncio.get_running_loop()
-    # We bind a separate socket to the response port (4002). If something
-    # else on the host already owns 4002 (rare; another Govee tool), the
-    # bind fails and we degrade gracefully to an empty result.
+    # We bind a separate socket to the response port (4002). The
+    # _DISCOVERY_LOCK serializes our own scans; the bind can still fail
+    # if a non-LedGrab Govee tool on the same host owns 4002.
     recv_sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
     recv_sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
     recv_sock.setblocking(False)
@@ -324,7 +352,12 @@ async def discover_govee_devices(timeout: float = 2.0) -> List[dict]:
         try:
             recv_sock.bind(("", GOVEE_RESPONSE_PORT))
         except OSError as exc:
-            logger.warning("Govee discovery: cannot bind %d (%s)", GOVEE_RESPONSE_PORT, exc)
+            logger.warning(
+                "Govee discovery: cannot bind port %d (%s). Another Govee "
+                "tool on this host may own the port; close it and retry.",
+                GOVEE_RESPONSE_PORT,
+                exc,
+            )
             return []
         send_sock.bind(("", 0))
         await loop.sock_sendto(
diff --git a/server/src/ledgrab/core/devices/govee_provider.py b/server/src/ledgrab/core/devices/govee_provider.py
index e11f3e2..692f421 100644
--- a/server/src/ledgrab/core/devices/govee_provider.py
+++ b/server/src/ledgrab/core/devices/govee_provider.py
@@ -9,6 +9,7 @@ from ledgrab.core.devices.govee_client import (
     discover_govee_devices,
     parse_govee_url,
 )
+from ledgrab.utils.net_classify import validate_lan_host
 from ledgrab.core.devices.led_client import (
     DeviceHealth,
     DiscoveredDevice,
@@ -62,6 +63,7 @@ class GoveeDeviceProvider(LEDDeviceProvider):
             host = parse_govee_url(url)
         except ValueError as exc:
             raise ValueError(f"Invalid Govee URL: {exc}") from exc
+        validate_lan_host(host)
         logger.info("Govee device URL validated: host=%s", host)
         return {}
 
diff --git a/server/src/ledgrab/core/devices/lifx_provider.py b/server/src/ledgrab/core/devices/lifx_provider.py
index bd935db..d0019e5 100644
--- a/server/src/ledgrab/core/devices/lifx_provider.py
+++ b/server/src/ledgrab/core/devices/lifx_provider.py
@@ -16,6 +16,7 @@ from ledgrab.core.devices.lifx_client import (
     discover_lifx_bulbs,
     parse_lifx_url,
 )
+from ledgrab.utils.net_classify import validate_lan_host
 from ledgrab.utils import get_logger
 
 if TYPE_CHECKING:
@@ -60,6 +61,7 @@ class LIFXDeviceProvider(LEDDeviceProvider):
             host, port = parse_lifx_url(url)
         except ValueError as exc:
             raise ValueError(f"Invalid LIFX URL: {exc}") from exc
+        validate_lan_host(host)
         logger.info("LIFX device URL validated: host=%s port=%d", host, port)
         return {}
 
diff --git a/server/src/ledgrab/core/devices/nanoleaf_client.py b/server/src/ledgrab/core/devices/nanoleaf_client.py
index 04a68a6..c7fe395 100644
--- a/server/src/ledgrab/core/devices/nanoleaf_client.py
+++ b/server/src/ledgrab/core/devices/nanoleaf_client.py
@@ -145,6 +145,12 @@ class NanoleafClient(LEDClient):
     def host(self) -> str:
         return self._host
 
+    @property
+    def port(self) -> int:
+        """Fixed at the protocol-mandated 16021. Exposed for cross-driver
+        symmetry with the UDP/TCP clients that also surface ``.port``."""
+        return NANOLEAF_PORT
+
     @property
     def is_connected(self) -> bool:
         return self._connected and self._http is not None
diff --git a/server/src/ledgrab/core/devices/nanoleaf_provider.py b/server/src/ledgrab/core/devices/nanoleaf_provider.py
index 2ab40d9..a42546d 100644
--- a/server/src/ledgrab/core/devices/nanoleaf_provider.py
+++ b/server/src/ledgrab/core/devices/nanoleaf_provider.py
@@ -17,6 +17,7 @@ from ledgrab.core.devices.nanoleaf_client import (
     pair_nanoleaf,
     parse_nanoleaf_url,
 )
+from ledgrab.utils.net_classify import validate_lan_host
 from ledgrab.utils import get_logger
 
 if TYPE_CHECKING:
@@ -68,6 +69,7 @@ class NanoleafDeviceProvider(LEDDeviceProvider):
             host = parse_nanoleaf_url(url)
         except ValueError as exc:
             raise ValueError(f"Invalid Nanoleaf URL: {exc}") from exc
+        validate_lan_host(host)
         token = await pair_nanoleaf(host)
         return {"nanoleaf_token": token}
 
@@ -83,6 +85,7 @@ class NanoleafDeviceProvider(LEDDeviceProvider):
             host = parse_nanoleaf_url(url)
         except ValueError as exc:
             raise ValueError(f"Invalid Nanoleaf URL: {exc}") from exc
+        validate_lan_host(host)
         logger.info("Nanoleaf URL validated: host=%s", host)
         return {}
 
@@ -116,6 +119,7 @@ class NanoleafDeviceProvider(LEDDeviceProvider):
             logger.warning("Nanoleaf discovery: zeroconf init failed (%s)", exc)
             return []
 
+        browsers: list = []
         try:
             browsers = [
                 AsyncServiceBrowser(aiozc.zeroconf, st, handlers=[_on_state_change])
@@ -124,9 +128,14 @@ class NanoleafDeviceProvider(LEDDeviceProvider):
             await asyncio.sleep(timeout)
             for info in discovered.values():
                 await info.async_request(aiozc.zeroconf, timeout=2000)
-            for browser in browsers:
-                await browser.async_cancel()
         finally:
+            # Cancel browsers in finally so a CancelledError during sleep or
+            # async_request still tears them down — caught by review MEDIUM #8.
+            for browser in browsers:
+                try:
+                    await browser.async_cancel()
+                except (OSError, RuntimeError):
+                    pass
             try:
                 await aiozc.async_close()
             except (OSError, RuntimeError):
diff --git a/server/src/ledgrab/core/devices/opc_provider.py b/server/src/ledgrab/core/devices/opc_provider.py
index 55b8305..4e63e36 100644
--- a/server/src/ledgrab/core/devices/opc_provider.py
+++ b/server/src/ledgrab/core/devices/opc_provider.py
@@ -12,6 +12,7 @@ from ledgrab.core.devices.led_client import (
     ProviderDeps,
 )
 from ledgrab.core.devices.opc_client import OPCClient, parse_opc_url
+from ledgrab.utils.net_classify import validate_lan_host
 from ledgrab.utils import get_logger
 
 if TYPE_CHECKING:
@@ -53,6 +54,7 @@ class OPCDeviceProvider(LEDDeviceProvider):
             host, port = parse_opc_url(url)
         except ValueError as exc:
             raise ValueError(f"Invalid OPC URL: {exc}") from exc
+        validate_lan_host(host)
         logger.info("OPC device URL validated: host=%s port=%d", host, port)
         return {}
 
diff --git a/server/src/ledgrab/core/devices/wiz_provider.py b/server/src/ledgrab/core/devices/wiz_provider.py
index d03f81d..28058ae 100644
--- a/server/src/ledgrab/core/devices/wiz_provider.py
+++ b/server/src/ledgrab/core/devices/wiz_provider.py
@@ -16,6 +16,7 @@ from ledgrab.core.devices.wiz_client import (
     discover_wiz_bulbs,
     parse_wiz_url,
 )
+from ledgrab.utils.net_classify import validate_lan_host
 from ledgrab.utils import get_logger
 
 if TYPE_CHECKING:
@@ -60,6 +61,7 @@ class WiZDeviceProvider(LEDDeviceProvider):
             host, port = parse_wiz_url(url)
         except ValueError as exc:
             raise ValueError(f"Invalid WiZ URL: {exc}") from exc
+        validate_lan_host(host)
         logger.info("WiZ device URL validated: host=%s port=%d", host, port)
         return {}
 
diff --git a/server/src/ledgrab/core/devices/yeelight_provider.py b/server/src/ledgrab/core/devices/yeelight_provider.py
index fe2132f..f17fae7 100644
--- a/server/src/ledgrab/core/devices/yeelight_provider.py
+++ b/server/src/ledgrab/core/devices/yeelight_provider.py
@@ -17,6 +17,7 @@ from ledgrab.core.devices.yeelight_client import (
     discover_yeelight_bulbs,
     parse_yeelight_url,
 )
+from ledgrab.utils.net_classify import validate_lan_host
 from ledgrab.utils import get_logger
 
 if TYPE_CHECKING:
@@ -65,6 +66,7 @@ class YeelightDeviceProvider(LEDDeviceProvider):
             host = parse_yeelight_url(url)
         except ValueError as exc:
             raise ValueError(f"Invalid Yeelight URL: {exc}") from exc
+        validate_lan_host(host)
         logger.info("Yeelight device URL validated: host=%s", host)
         return {}
 
diff --git a/server/src/ledgrab/static/js/features/devices.ts b/server/src/ledgrab/static/js/features/devices.ts
index 7b1ff30..59b2138 100644
--- a/server/src/ledgrab/static/js/features/devices.ts
+++ b/server/src/ledgrab/static/js/features/devices.ts
@@ -738,7 +738,7 @@ export async function showSettings(deviceId: any) {
             const nmi = device.nanoleaf_min_interval_ms ?? 100;
             (document.getElementById('settings-nanoleaf-min-interval') as HTMLInputElement).value = String(nmi);
             if (nanoleafPairedGroup) {
-                (nanoleafPairedGroup as HTMLElement).style.display = device.nanoleaf_token ? '' : 'none';
+                (nanoleafPairedGroup as HTMLElement).style.display = device.nanoleaf_paired ? '' : 'none';
             }
             const urlLabel8 = urlGroup.querySelector('label[for="settings-device-url"]') as HTMLElement | null;
             const urlHint8 = urlGroup.querySelector('.input-hint') as HTMLElement | null;
diff --git a/server/src/ledgrab/static/js/types.ts b/server/src/ledgrab/static/js/types.ts
index 9fe76f7..1ed23b4 100644
--- a/server/src/ledgrab/static/js/types.ts
+++ b/server/src/ledgrab/static/js/types.ts
@@ -75,14 +75,13 @@ export interface Device {
     opc_channel: number;
     espnow_peer_mac: string;
     espnow_channel: number;
-    hue_username: string;
-    hue_client_key: string;
+    hue_paired: boolean;
     hue_entertainment_group_id: string;
     yeelight_min_interval_ms: number;
     wiz_min_interval_ms: number;
     lifx_min_interval_ms: number;
     govee_min_interval_ms: number;
-    nanoleaf_token: string;
+    nanoleaf_paired: boolean;
     nanoleaf_min_interval_ms: number;
     spi_speed_hz: number;
     spi_led_type: string;
diff --git a/server/src/ledgrab/storage/device_store.py b/server/src/ledgrab/storage/device_store.py
index 9243dc4..69211ea 100644
--- a/server/src/ledgrab/storage/device_store.py
+++ b/server/src/ledgrab/storage/device_store.py
@@ -20,8 +20,27 @@ def _enc(value: str) -> str:
 
 
 def _dec(value: str) -> str:
-    """Decrypt an envelope; legacy plaintext passes through unchanged."""
-    return secret_box.decrypt(value) if value else ""
+    """Decrypt an envelope; legacy plaintext passes through unchanged.
+
+    A corrupt envelope (key rotated, partial write, AEAD mismatch) returns
+    an empty string and logs an error rather than re-raising. Without this
+    fallback a single bad row would propagate up to ``BaseSqliteStore._load``
+    and silently drop the entire device from ``self._items`` -- so a
+    regenerated ``data/.secret_key`` would make every Hue / Nanoleaf /
+    BLE-Govee device disappear with only a log line for a trail. Caught
+    by pre-merge review HIGH #5.
+    """
+    if not value:
+        return ""
+    try:
+        return secret_box.decrypt(value)
+    except Exception as exc:
+        logger.error(
+            "Could not decrypt stored secret (%s); clearing the field. "
+            "Re-pair the affected device to recover.",
+            type(exc).__name__,
+        )
+        return ""
 
 
 class Device:
@@ -656,12 +675,18 @@ class DeviceStore(BaseSqliteStore[Device]):
             if new_name is not None and new_name != device.name:
                 self._check_name_unique(new_name, exclude_id=device_id)
 
-            # Build new Device from existing fields + updates (immutable pattern)
-            device_fields = device.to_dict()
-            # Map 'id' back to 'device_id' for the constructor
+            # Build new Device from existing fields + updates (immutable pattern).
+            # Source kwargs directly from instance attributes via vars(), NOT
+            # via to_dict() -- to_dict() encrypts hue_username/hue_client_key/
+            # ble_govee_key/nanoleaf_token via _enc(), and Device.__init__
+            # doesn't decrypt, so a round-trip through to_dict() would leave
+            # the new in-memory Device holding ciphertext where plaintext
+            # belongs. The cached _items entry would then return ciphertext
+            # to provider.create_client(), and the device's runtime auth
+            # would silently break until server restart (caught by review).
+            device_fields = vars(device).copy()
+            # Constructor takes device_id, but attribute is id.
             device_fields["device_id"] = device_fields.pop("id")
-            # Restore datetime objects (to_dict serializes them as ISO strings)
-            device_fields["created_at"] = device.created_at
             device_fields["updated_at"] = datetime.now(timezone.utc)
             # Apply updates
             device_fields.update(updates)
diff --git a/server/src/ledgrab/utils/net_classify.py b/server/src/ledgrab/utils/net_classify.py
index c54370a..ba1ac78 100644
--- a/server/src/ledgrab/utils/net_classify.py
+++ b/server/src/ledgrab/utils/net_classify.py
@@ -134,3 +134,45 @@ def is_loopback(host: str) -> bool:
     if h in {"localhost", "testclient"}:
         return True
     return classify_ip(h) is HostCategory.LOOPBACK
+
+
+_LAN_CATEGORIES: frozenset[HostCategory] = frozenset(
+    {
+        HostCategory.LOOPBACK,
+        HostCategory.PRIVATE,
+        HostCategory.LINK_LOCAL,
+        HostCategory.UNSPECIFIED,
+    }
+)
+
+
+def validate_lan_host(host: str) -> None:
+    """Raise ``ValueError`` when *host* is a literal public IP address.
+
+    Used by LED-device providers to reject ``wiz://1.1.1.1:38899`` style
+    URLs that an authenticated (or anonymous, given the default no-auth
+    config) caller could otherwise weaponise into a network-scan oracle.
+
+    Non-IP-literal hostnames (``bulb.local``, ``office-strip``) pass
+    through untouched -- they resolve via mDNS at connect time, where
+    failure to reach a real device produces the right "device unreachable"
+    error path anyway. The check is deliberately a syntax filter, not a
+    DNS-resolving SSRF guard: LedGrab is LAN-bound by design, and
+    aggressive DNS-time rebinding protection is the job of the platform's
+    network policy, not a per-driver validator.
+    """
+    if not host:
+        return
+    h = host.strip().lower()
+    if h.startswith("[") and h.endswith("]"):
+        h = h[1:-1]
+    h = h.split("%", 1)[0]  # strip IPv6 zone id
+    cat = classify_ip(h)
+    if cat is HostCategory.UNPARSEABLE:
+        return  # hostname / mDNS label -- accept
+    if cat not in _LAN_CATEGORIES:
+        raise ValueError(
+            f"Refusing to add device at {host!r}: literal {cat.value} IP "
+            "addresses are rejected. LedGrab is LAN-only; if your device is "
+            "genuinely on a public address, use a hostname or tunnel."
+        )
diff --git a/server/tests/api/routes/test_devices_routes.py b/server/tests/api/routes/test_devices_routes.py
index 1b59957..afcdf5f 100644
--- a/server/tests/api/routes/test_devices_routes.py
+++ b/server/tests/api/routes/test_devices_routes.py
@@ -340,3 +340,80 @@ class TestPairDevice:
     def test_missing_required_fields_returns_422(self, client):
         resp = client.post("/api/v1/devices/pair", json={"device_type": "nanoleaf"})
         assert resp.status_code == 422
+
+
+class TestPairThenCreateFlow:
+    """End-to-end coverage: pair, then persist; assert the token is
+    encrypted at rest and decrypted in to_config(), and that the API
+    response strips the secret.
+
+    Closes the LOW gap in the pre-merge review: pair-route tests stopped
+    at the 200 response, never carrying the returned fields through to
+    storage to verify the round-trip and the response-strip.
+    """
+
+    def test_pair_then_create_persists_encrypted_token(self, client, device_store):
+        from ledgrab.api.routes.devices import _device_to_response
+        from ledgrab.core.devices import led_client as _led_client
+        from ledgrab.core.devices.led_client import DeviceHealth
+
+        class _NanoleafLikeStub:
+            @property
+            def device_type(self):
+                return "nanoleaf_like_stub"
+
+            @property
+            def capabilities(self):
+                return {"manual_led_count", "requires_pairing"}
+
+            async def pair_device(self, url):
+                return {"nanoleaf_token": "secret-paired-token"}
+
+            async def validate_device(self, url):
+                return {"led_count": 9}
+
+            def create_client(self, config, *, deps):
+                raise AssertionError("not used")
+
+            async def check_health(self, url, http_client, prev_health=None):
+                return DeviceHealth(online=True)
+
+        _led_client.register_provider(_NanoleafLikeStub())
+        try:
+            # Step 1: pair via the route
+            pair_resp = client.post(
+                "/api/v1/devices/pair",
+                json={"device_type": "nanoleaf_like_stub", "url": "stub://1.2.3.4"},
+            )
+            assert pair_resp.status_code == 200, pair_resp.text
+            fields = pair_resp.json()["fields"]
+            assert fields == {"nanoleaf_token": "secret-paired-token"}
+
+            # Step 2: persist via the store (skip the route's create path
+            # which would require a real validate_device handshake)
+            device = device_store.create_device(
+                name="E2E Paired",
+                url="stub://1.2.3.4",
+                led_count=9,
+                device_type="nanoleaf",
+                **fields,
+            )
+
+            # In-memory device holds plaintext
+            assert device.nanoleaf_token == "secret-paired-token"
+
+            # to_config surfaces plaintext to the provider
+            config = device.to_config()
+            assert config.nanoleaf_token == "secret-paired-token"
+
+            # Persisted row holds ciphertext (envelope prefix)
+            persisted = device.to_dict()
+            assert persisted["nanoleaf_token"].startswith("ENC:v1:")
+            assert persisted["nanoleaf_token"] != "secret-paired-token"
+
+            # API response strips the token; only a boolean flag remains
+            resp = _device_to_response(device).model_dump()
+            assert "nanoleaf_token" not in resp
+            assert resp.get("nanoleaf_paired") is True
+        finally:
+            _led_client._provider_registry.pop("nanoleaf_like_stub", None)
diff --git a/server/tests/test_device_store.py b/server/tests/test_device_store.py
index f4561fd..360a336 100644
--- a/server/tests/test_device_store.py
+++ b/server/tests/test_device_store.py
@@ -270,3 +270,81 @@ def test_update_device_ignores_unknown_fields(device_store):
     # Should not raise even with an unknown kwarg
     updated = device_store.update_device(device.id, nonexistent_field="foo")
     assert updated.name == "Test WLED"
+
+
+def test_update_device_preserves_plaintext_secrets(device_store):
+    """update_device must not corrupt encrypted-at-rest secrets in memory.
+
+    Regression test for the to_dict() round-trip bug: to_dict() encrypts
+    hue_username / hue_client_key / ble_govee_key / nanoleaf_token via
+    _enc(), but Device.__init__ does not decrypt -- so the old
+    update_device path would leave the cached Device holding ciphertext
+    where plaintext belongs, breaking runtime auth for paired devices
+    until server restart. See pre-merge review CRITICAL #2.
+    """
+    device = device_store.create_device(
+        name="Office panels",
+        url="nanoleaf://192.168.1.99",
+        led_count=9,
+        device_type="nanoleaf",
+        nanoleaf_token="plaintext-secret-token",
+    )
+    assert device.nanoleaf_token == "plaintext-secret-token"
+
+    # An innocuous rename must not touch the secret.
+    updated = device_store.update_device(device.id, name="Renamed panels")
+    assert (
+        updated.nanoleaf_token == "plaintext-secret-token"
+    ), "rename round-tripped the secret through to_dict() and corrupted it"
+
+    # The cached _items entry must also hold plaintext (it is what
+    # provider.create_client() reads).
+    cached = device_store.get_device(device.id)
+    assert cached.nanoleaf_token == "plaintext-secret-token"
+
+    # And to_config() must surface the plaintext token to the provider.
+    config = cached.to_config()
+    assert config.nanoleaf_token == "plaintext-secret-token"
+
+
+def test_update_device_preserves_hue_secrets(device_store):
+    """Same bug applies to hue_username / hue_client_key / ble_govee_key."""
+    device = device_store.create_device(
+        name="Hue bridge",
+        url="http://192.168.1.50",
+        led_count=10,
+        device_type="hue",
+        hue_username="plain-hue-user",
+        hue_client_key="plain-client-key",
+    )
+
+    updated = device_store.update_device(device.id, name="Renamed bridge")
+
+    assert updated.hue_username == "plain-hue-user"
+    assert updated.hue_client_key == "plain-client-key"
+
+
+def test_from_dict_clears_corrupt_secret_envelope(device_store):
+    """A corrupt nanoleaf_token must not delete the device row.
+
+    Regression test for HIGH #5: previously _dec() would raise on a bad
+    envelope, propagate up through BaseSqliteStore._load, and the entire
+    device row would silently disappear. The fix clears the offending
+    field and logs an error instead.
+    """
+    payload = {
+        "id": "device_abc12345",
+        "name": "Will survive",
+        "url": "nanoleaf://192.168.1.50",
+        "led_count": 9,
+        "device_type": "nanoleaf",
+        # Looks like an envelope (ENC:v1: prefix) but the base64 body is
+        # truncated / corrupt -- the AES-GCM auth tag will fail to verify.
+        "nanoleaf_token": "ENC:v1:not-real-base64-cipher-text",
+    }
+
+    restored = Device.from_dict(payload)
+
+    # The device hydrates; the broken secret is cleared, not crashed.
+    assert restored.id == "device_abc12345"
+    assert restored.nanoleaf_token == ""
diff --git a/server/tests/test_nanoleaf.py b/server/tests/test_nanoleaf.py
index 793419b..4be78bc 100644
--- a/server/tests/test_nanoleaf.py
+++ b/server/tests/test_nanoleaf.py
@@ -322,24 +322,34 @@ def test_provider_device_type_and_capabilities():
 
 @pytest.mark.asyncio
 async def test_provider_pair_device_returns_nanoleaf_token(respx_mock):
-    respx_mock.post(f"http://1.2.3.4:{NANOLEAF_PORT}/api/v1/new").mock(
+    # Use a LAN address; validate_lan_host now rejects public IPs at the
+    # provider boundary (review HIGH #4).
+    respx_mock.post(f"http://192.168.1.50:{NANOLEAF_PORT}/api/v1/new").mock(
         return_value=httpx.Response(200, json={"auth_token": "ttoken"}),
     )
     provider = NanoleafDeviceProvider()
 
-    fields = await provider.pair_device("nanoleaf://1.2.3.4")
+    fields = await provider.pair_device("nanoleaf://192.168.1.50")
 
     assert fields == {"nanoleaf_token": "ttoken"}
 
 
 @pytest.mark.asyncio
 async def test_provider_pair_device_propagates_pairing_not_ready(respx_mock):
-    respx_mock.post(f"http://1.2.3.4:{NANOLEAF_PORT}/api/v1/new").mock(
+    respx_mock.post(f"http://192.168.1.50:{NANOLEAF_PORT}/api/v1/new").mock(
         return_value=httpx.Response(403),
     )
     provider = NanoleafDeviceProvider()
     with pytest.raises(PairingNotReady):
-        await provider.pair_device("nanoleaf://1.2.3.4")
+        await provider.pair_device("nanoleaf://192.168.1.50")
+
+
+@pytest.mark.asyncio
+async def test_provider_pair_device_rejects_public_ip():
+    """validate_lan_host fires before pair_nanoleaf even runs."""
+    provider = NanoleafDeviceProvider()
+    with pytest.raises(ValueError, match="LedGrab is LAN-only"):
+        await provider.pair_device("nanoleaf://1.1.1.1")
 
 
 @pytest.mark.asyncio
diff --git a/server/tests/test_net_classify.py b/server/tests/test_net_classify.py
index cd26326..2609c4d 100644
--- a/server/tests/test_net_classify.py
+++ b/server/tests/test_net_classify.py
@@ -135,3 +135,55 @@ def test_is_loopback_recognises_loopback(host: str) -> None:
 )
 def test_is_loopback_rejects_other(host) -> None:
     assert is_loopback(host) is False
+
+
+# ─── validate_lan_host ────────────────────────────────────────────
+
+
+from ledgrab.utils.net_classify import validate_lan_host  # noqa: E402
+
+
+@pytest.mark.parametrize(
+    "host",
+    [
+        "127.0.0.1",
+        "10.0.0.5",
+        "192.168.1.50",
+        "172.16.0.10",
+        "fe80::1",
+        "fc00::1",
+        "0.0.0.0",
+        # IPv6 with brackets and zone id
+        "[fe80::1%eth0]",
+        # Plain hostnames pass through (mDNS / bare-label)
+        "bulb.local",
+        "office-strip",
+        "controller.lan",
+        "",  # empty also passes (caller handles validation upstream)
+    ],
+)
+def test_validate_lan_host_accepts_local(host) -> None:
+    """Loopback / private / link-local / hostnames must not raise."""
+    validate_lan_host(host)
+
+
+@pytest.mark.parametrize(
+    "host",
+    [
+        "1.1.1.1",  # Cloudflare DNS (routable public)
+        "8.8.8.8",  # Google DNS
+        "224.0.0.1",  # multicast — not a LAN device address
+        "2606:4700:4700::1111",  # Cloudflare DNS IPv6
+    ],
+)
+def test_validate_lan_host_rejects_public_or_multicast(host) -> None:
+    """Reject genuinely-public addresses and multicast targets.
+
+    Note: Python's :func:`ipaddress.ip_address(...).is_private` treats
+    RFC6890 ranges (documentation 192.0.2/24, former class E 240/4, etc.)
+    as private, so those are accepted as "local-ish" by our classifier --
+    which is the correct policy for LedGrab: those ranges aren't routable
+    public addresses, and refusing them would be unhelpful theatre.
+    """
+    with pytest.raises(ValueError, match="LedGrab is LAN-only"):
+        validate_lan_host(host)