chore: release v0.8.1

Backend
- snapshot: GET /api/v1/snapshot aggregates targets, devices, sources,
  presets and system into one payload for the HA coordinator, collapsing
  the prior ~2N+M request fan-out; per-section ?include= gating.
- graph: GET /api/v1/graph{,/schema,/dependents} backed by a pure,
  unit-tested graph_schema engine — one authoritative connectable-field
  registry so the editor no longer hard-codes topology in two places.
- devices: thread mqtt_source_id through DeviceCreate/Update/Response and
  the routes for multi-broker MQTT; shared validate_mqtt_source_exists
  (_mqtt_validation.py) reused by device + output-target routes; stop
  update_device masking intentional 4xx as 500.
- shutdown: bound uvicorn graceful-shutdown via GRACEFUL_SHUTDOWN_TIMEOUT
  (shared by __main__, android_entry, demo) so a lingering events WebSocket
  can't strand LED targets or block process exit.
- access log: structured _access_log middleware attributing each request to
  its authenticated token label (never the secret); uvicorn access_log off.

Frontend
- graph editor: generic schema-driven port/edge rendering, layout and
  connection handling; service-worker refresh.
- device modals: MQTT broker EntitySelect for device_type=mqtt in add-device
  and settings, wired into load/save/validate/dirty-check/clone.
- i18n: en/ru/zh keys.

Tests: graph routes + schema, snapshot routes, access log, mqtt_source_id
device regressions, bounded-shutdown entrypoint. 1614 passed.

RELEASE_NOTES.md

@@ -1,72 +1,54 @@
-## v0.8.0 (2026-05-28)
+## v0.8.1 (2026-05-28)
 
 ### User-facing changes
 
 #### Features
 
-##### Android TV — production-readiness pass
+##### Multi-broker MQTT devices
 
-- **Security:** per-install random API key (persisted, threaded into the embedded server via env, embedded in the pairing QR as a URL-fragment so it never reaches HTTP logs); root-shell injection eliminated via POSIX-quoted `runAsRoot(argv)` overload; broadcast receivers locked to the app package; release builds refuse to silently sign with the debug keystore; crash log retention capped at 10 entries
-- **Performance:** single reusable RGBA buffer in `ScreenCapture` / `RootScreenrecord` (eliminates ~15 MB/s GC churn at 30 fps); frame pacer switched to `elapsedRealtimeNanos` with catch-up accumulator (fixes ~30.3 fps drift); capture dimensions derived from source aspect ratio so non-16:9 displays aren't squashed; QR bitmap cached by URL
-- **Compatibility:** compileSdk/targetSdk → 35 (Play Store requirement); armeabi-v7a build path; foreground service type declared as `mediaProjection|specialUse` with proper `ServiceCompat.startForeground` promotion; Ethernet > Wi-Fi > VPN > cellular selection in `NetworkUtils`; Android 15 predictive-back via `enableOnBackInvokedCallback`; splash screen API hides Chaquopy cold-start delay
-- **UI/UX:** all hardcoded English strings localised across en/ru/zh; monochrome notification icon; 320×180 TV banner; ViewStub-based running panel; pulse animator on Running dot; "Starting…" button while probing root; autostart checkbox hidden on unrooted devices
-- **Lifecycle hardening:** `processLock` serialises EOF respawn vs `stop()` to prevent orphaned screenrecord; publish-before-start under `@Synchronized` in `CaptureService.restartRootPipeline` closes the orphan window during watchdog restarts; watchdog give-up bound corrected ([ef1f9ea](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/ef1f9ea))
+- The device editor now shows an MQTT **broker picker** for `device_type=mqtt` (in both the add-device and device-settings modals), wired into load / save / validate / dirty-check / clone. An empty selection means "first available broker"
+- `mqtt_source_id` is now threaded end-to-end through `DeviceCreate` / `DeviceUpdate` / `DeviceResponse` and the device routes; the referenced broker is validated on create **and** update ([a5effba](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/a5effba))
 
-##### Backup format — bundled DB + assets ZIP
+##### Schema-driven wiring-graph editor
 
-- Auto-backups now produce a `.zip` containing `ledgrab.db` plus every file from the assets directory under `assets/` — matching the manual `GET /api/v1/system/backup` download. Restore accepts both `.zip` and legacy `.db` interchangeably
-- Partial-write hardening: writes stage to `<name>.partial` then `os.replace` into place — a crash mid-write never leaves a corrupt backup masquerading as valid. Stale `.partial` files from prior crashes are swept on the next run
-- Symlinks inside the assets directory are skipped (security guard against link targets outside the dir)
-- Backups over 500 MB log a warning so operators notice unbounded asset growth before disk fills up
-- `restart.py` redirects spawned restart script stdout/stderr to `restart.log` and bails out early if the script is missing — silent failures used to vanish into a detached child ([85da2e5](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/85da2e5))
+- The visual graph editor now renders ports and edges generically from a backend-served schema (`GET /api/v1/graph/schema`) instead of hard-coding the connectable-field topology in two places — so client and server can no longer drift
+- New `GET /api/v1/graph` returns the full nodes + edges + validation topology, and `GET /api/v1/graph/dependents/{kind}/{id}` reports what references an entity ([a5effba](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/a5effba))
 
-##### Spectrum-aperture icon set
+##### Aggregated snapshot endpoint
 
-- Regenerated icon family from a single Pillow script: rounded-square aperture traced by a continuous RGB color-wheel stroke over a vignette canvas with chromatic bloom. 4× supersampled then downsampled per output for crispness
-- New 256 px transparent-background **tray variant** — taskbar icon reads cleanly against light themes instead of showing a dark tile
-- `icon.ico` now embeds 16/24/32/48/64/128/256 frames sourced from the transparent master (fixes the dark-square halo on light Windows themes)
-- Maskable 512 variant safe-area padded for PWA round-crops ([3645216](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/3645216))
+- New `GET /api/v1/snapshot` returns all output targets (with processing state + metrics), devices (with brightness), the source / preset / clock lists, and the system block in a **single response** — collapsing the Home Assistant integration's previous ~2N+M request fan-out into one round trip
+- `?include=` fetches only a subset of sections, and an excluded section also skips its server-side work (e.g. cold-cache hardware brightness probes or the blocking NVML performance query) ([a5effba](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/a5effba))
 
 #### Bug Fixes
 
-- **Notification sound dropdowns:** both the per-app override list and the main row now always render the EntitySelect (was silently inert before any sound assets were registered) and offer "no sound" as a first-class option via `allowNone` ([1f95993](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/1f95993))
-- **CSS editor:** `notification_sound` and `notification_volume` are now persisted on save — they were silently dropped from the payload before ([66b85b0](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/66b85b0))
-- **Python 3.13 ctypes:** Win32 message-pump prototypes (`GetMessageW` / `TranslateMessage` / `DispatchMessageW`) now share a single `LPMSG = POINTER(wintypes.MSG)` class across `WindowsShutdownGuard` and `PlatformDetector` — fixes the `expected LP_MSG instance instead of pointer to _MSG` error and the resulting shutdown-guard / display-power-monitor failure on 3.13 ([e4d24a0](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/e4d24a0), [0d840ad](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/0d840ad))
+- **Graceful shutdown no longer hangs:** uvicorn's graceful-shutdown wait is now bounded (`GRACEFUL_SHUTDOWN_TIMEOUT`, shared by the desktop, Android, and demo launchers). A lingering events WebSocket (which the browser auto-reconnects) used to keep connections from draining, so the lifespan shutdown never ran — leaving LED targets lit and blocking process exit. Ctrl+C / OS shutdown with the UI open now reliably stops targets and checkpoints the DB ([a5effba](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/a5effba))
+- **Device update error codes:** `update_device` no longer masks an intentional 4xx (e.g. an unknown `mqtt_source_id` or failed group validation) as a generic 500 ([a5effba](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/a5effba))
 
 ---
 
 ### Development / Internal
 
-#### CI/Build
+#### Backend
 
-- `release.yml` now creates the Gitea release as a **draft** and only flips `draft=false` once every build job (Windows, Linux, Docker) has uploaded its artifacts and sha256 sidecars — users never see a release page that's missing assets, which would have broken the in-app updater ([bc42604](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/bc42604))
+- **Wiring-graph schema engine** (`api/graph_schema.py`): a pure, unit-tested module that is the single source of truth for which reference fields connect which entity kinds; builds the topology and performs dependency lookup plus cycle / dangling-reference detection without booting the app or any store. The route layer only gathers serialized entities and delegates ([a5effba](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/a5effba))
+- **Structured access log:** a new middleware emits one structured line per request, attributing it to the authenticated token's friendly label (the key name, **never** the secret) so traffic can be traced to a client (e.g. `homeassistant` vs `android`). uvicorn's own access log is disabled to avoid duplicate lines ([a5effba](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/a5effba))
+- Shared `validate_mqtt_source_exists` (`_mqtt_validation.py`) deduplicates the MQTT-source existence check between the device and output-target routes ([a5effba](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/a5effba))
 
-#### Refactoring
+#### Frontend
 
-- **Shared API client + automations registry (audit M7, H8):** new `core/api-client.ts` wraps `fetchWithAuth` with typed `apiGet` / `apiPost` / `apiPut` / `apiPatch` / `apiDelete`; 35 feature/core files migrated. FastAPI validation-array detail unwrap hardened. Automations editor's two hand-rolled `RuleType` dispatch ladders converted to `Record<RuleType, ...>` registries with an import-time exhaustiveness check ([bb3a316](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/bb3a316))
-- **types.ts split (audit H6):** 1140 LOC `types.ts` split into 18 per-entity files under `types/`, original file kept as a pure re-export barrel — 102 type exports preserved with no import sites changed ([49c35a2](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/49c35a2))
+- Service-worker refresh for the new bundle ([a5effba](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/a5effba))
 
-#### Documentation
+#### Tests
 
-- `REVIEW_RECONCILE_NOTES.md` — design doc for the dashboard innerHTML reconciliation work: bug-class analysis, latent-site inventory, decision ladder (helper / hand-rolled cells / Lit), and recommendation to migrate polling-heavy modules to Lit with `entity-events.ts` tab reconciliation sequenced first ([10eb24b](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/10eb24b))
+- New suites: graph routes + schema engine, snapshot routes, access-log middleware, `mqtt_source_id` device regressions, and the bounded-shutdown entrypoint. Full suite: **1614 passing** ([a5effba](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/a5effba))
 
 ---
 
 <details>
-<summary>All Commits (11)</summary>
+<summary>All Commits (1)</summary>
 
 | Hash | Message | Author |
 | ---- | ------- | ------ |
-| [0d840ad](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/0d840ad) | fix(ctypes): share wintypes.MSG with platform_detector to avoid argtype races | alexei.dolgolyov |
-| [1f95993](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/1f95993) | fix(notification): allow clearing the sound on per-app overrides and main row | alexei.dolgolyov |
-| [10eb24b](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/10eb24b) | docs: dashboard innerHTML reconciliation review notes | alexei.dolgolyov |
-| [66b85b0](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/66b85b0) | fix(css-editor): persist notification_sound + notification_volume | alexei.dolgolyov |
-| [bc42604](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/bc42604) | ci(release): publish release only after every build job uploads assets | alexei.dolgolyov |
-| [3645216](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/3645216) | feat(icons): spectrum aperture icon set + dedicated tray variant | alexei.dolgolyov |
-| [85da2e5](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/85da2e5) | feat(backup): bundle assets in ZIP + partial-write hardening + restart log | alexei.dolgolyov |
-| [e4d24a0](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/e4d24a0) | fix(ctypes): pin LPMSG across MSG-pump prototypes for Python 3.13 | alexei.dolgolyov |
-| [bb3a316](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/bb3a316) | refactor(frontend): shared API client + automations registry (audit M7, H8) | alexei.dolgolyov |
-| [49c35a2](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/49c35a2) | refactor(frontend): split types.ts into 18 per-entity files (audit H6) | alexei.dolgolyov |
-| [ef1f9ea](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/ef1f9ea) | feat(android): production-readiness pass — security, perf, compat, UI/UX | alexei.dolgolyov |
+| [a5effba](https://git.dolgolyov-family.by/alexei.dolgolyov/ledgrab/commit/a5effba) | feat: aggregated snapshot + wiring-graph APIs, MQTT device brokers | alexei.dolgolyov |
 
 </details>

TODO.md

@@ -201,9 +201,19 @@ caller off the legacy path, then delete it.
 - [x] Field on `device_config.MQTTConfig`
 - [x] `MQTTLEDClient` acquires runtime in `connect()`, releases in `close()`
 - [x] Provider threads `mqtt_manager` via `ProviderDeps`
-- [ ] Device editor: MQTT source picker shown for `device_type=mqtt` *(UI still
-      pending — backend accepts the field, but the device-create form doesn't
-      expose it yet)*
+- [x] Device editor: MQTT source picker shown for `device_type=mqtt`. Turned
+      out the API layer was *also* missing it (the TODO's "backend accepts the
+      field" was wrong — `mqtt_source_id` lived in `device_store` +
+      `device_config.MQTTConfig` but was dropped by `DeviceCreate/Update/Response`
+      and the routes). Added: schema fields + route threading + referenced-source
+      validation (`_validate_mqtt_source_exists`, mirrors output_targets) +
+      `except HTTPException: raise` guard in `update_device` (it was masking its
+      own 4xx as 500). Frontend: broker `EntitySelect` (reusing `mqttSourcesCache`)
+      in both the add-device (`device-discovery.ts`) and settings
+      (`devices.ts`) modals — shown for `device_type=mqtt`, wired into
+      load/save/validate/dirty-check/clone. Empty = "first available broker".
+      4 regression tests in `test_devices_routes.py::TestMqttSourceId`; full
+      suite 1567 passing; en/ru/zh keys added.
 
 ### Phase 5 — `AutomationEngine`
 
@@ -213,8 +223,11 @@ caller off the legacy path, then delete it.
 ### Phase 6 — `api/routes/system.py`
 
 - [x] Replace integration status with `mqtt_manager.get_all_sources_status()`
-- [ ] Update frontend dashboard payload (MQTT widget now expects a list of
-      sources instead of a single `enabled`/`connected` pair — surface in UI)
+- [x] Update frontend dashboard payload (MQTT widget now expects a list of
+      sources instead of a single `enabled`/`connected` pair — surface in UI).
+      Done: `dashboard.ts` `_renderMQTTIntegrationCard` renders one card per
+      `mqttStatus.connections` entry; `_updateIntegrationsInPlace` iterates the
+      list.
 
 ### Phase 7 — Startup migration
 

android/app/build.gradle.kts

@@ -41,7 +41,7 @@ android {
         // in CI).  See ledgrabVersionCode above.  Was stuck at 1 before —
         // sideload updates silently refused to install.
         versionCode = ledgrabVersionCode
-        versionName = "0.8.0"
+        versionName = "0.8.1"
 
         // ABI selection. Detect armeabi-v7a wheel presence and opt the
         // ABI in only when the matching pydantic-core wheel is on disk —

server/pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "ledgrab"
-version = "0.8.0"
+version = "0.8.1"
 description = "Ambient lighting system that captures screen content and drives LED strips in real time"
 authors = [
     {name = "Alexei Dolgolyov", email = "dolgolyov.alexei@gmail.com"}

server/src/ledgrab/__init__.py

@@ -9,7 +9,7 @@ from pathlib import Path
 # In dev (running from source without `pip install -e .`) and on Android
 # (Chaquopy embeds the source directly with no dist-info), we additionally
 # read pyproject.toml so the version is always correct without manual sync.
-_FALLBACK_VERSION = "0.8.0"
+_FALLBACK_VERSION = "0.8.1"
 
 
 def _read_pyproject_version() -> str | None:

server/src/ledgrab/__main__.py

@@ -39,8 +39,9 @@ _fix_embedded_tcl_paths()
 
 import uvicorn  # noqa: E402
 
-from ledgrab.config import get_config  # noqa: E402
+from ledgrab.config import Config, get_config  # noqa: E402
 from ledgrab.server_ref import set_server, set_tray  # noqa: E402
+from ledgrab.shutdown_state import GRACEFUL_SHUTDOWN_TIMEOUT  # noqa: E402
 from ledgrab.tray import PYSTRAY_AVAILABLE, TrayManager  # noqa: E402
 from ledgrab.utils import setup_logging, get_logger  # noqa: E402
 from ledgrab.utils.platform import is_windows  # noqa: E402
@@ -108,17 +109,28 @@ def _check_port(host: str, port: int) -> None:
             sys.exit(1)
 
 
-def main() -> None:
-    config = get_config()
-    _check_port(config.server.host, config.server.port)
+def _build_server(config: Config) -> uvicorn.Server:
+    """Construct the uvicorn Server with a bounded graceful-shutdown timeout.
 
+    Extracted so the graceful-shutdown bound is unit-testable — leaving it
+    unset (the uvicorn default of ``None``) is the regression that strands
+    LED targets and prevents the process from exiting.
+    """
     uv_config = uvicorn.Config(
         "ledgrab.main:app",
         host=config.server.host,
         port=config.server.port,
         log_level=config.server.log_level.lower(),
+        timeout_graceful_shutdown=GRACEFUL_SHUTDOWN_TIMEOUT,
     )
-    server = uvicorn.Server(uv_config)
+    return uvicorn.Server(uv_config)
+
+
+def main() -> None:
+    config = get_config()
+    _check_port(config.server.host, config.server.port)
+
+    server = _build_server(config)
     set_server(server)
 
     # Wire the OS-shutdown safety net. The lifespan in ``ledgrab.main`` signals
@@ -165,9 +177,11 @@ def main() -> None:
         tray.run()
 
         # Tray exited — wait for server to finish its graceful shutdown.
-        # Use a longer join than the lifespan's own ~18 s budget so we don't
-        # cut the DB checkpoint short on a slow disk.
-        server_thread.join(timeout=20)
+        # Budget: the graceful-shutdown wait (GRACEFUL_SHUTDOWN_TIMEOUT) runs
+        # first, then the lifespan's own ~16 s shutdown (target restore + DB
+        # checkpoint). Join longer than their sum so a slow disk doesn't get
+        # the DB checkpoint cut short.
+        server_thread.join(timeout=25)
         if guard is not None:
             guard.stop()
     else:

server/src/ledgrab/android_entry.py

@@ -84,6 +84,8 @@ def start_server(data_dir: str, port: int = 8080, api_key: str | None = None) ->
             "LEDGRAB_AUTH__API_KEYS."
         )
 
+    from ledgrab.shutdown_state import GRACEFUL_SHUTDOWN_TIMEOUT
+
     uv_config = uvicorn.Config(
         "ledgrab.main:app",
         host=config.server.host,
@@ -91,6 +93,9 @@ def start_server(data_dir: str, port: int = 8080, api_key: str | None = None) ->
         log_level=config.server.log_level.lower(),
         # No uvloop/httptools on Android — use pure-Python asyncio
         loop="asyncio",
+        # Bound the graceful-shutdown wait so stop_server() can't hang forever
+        # on a lingering WebView events WebSocket — see shutdown_state for why.
+        timeout_graceful_shutdown=GRACEFUL_SHUTDOWN_TIMEOUT,
     )
 
     global _server, _loop

server/src/ledgrab/api/__init__.py

@@ -33,6 +33,8 @@ from .routes.audio_processing_templates import router as audio_processing_templa
 from .routes.audio_filters import router as audio_filters_router
 from .routes.pattern_templates import router as pattern_templates_router
 from .routes.preferences import router as preferences_router
+from .routes.snapshot import router as snapshot_router
+from .routes.graph import router as graph_router
 
 router = APIRouter()
 router.include_router(system_router)
@@ -66,5 +68,7 @@ router.include_router(audio_processing_templates_router)
 router.include_router(audio_filters_router)
 router.include_router(pattern_templates_router)
 router.include_router(preferences_router)
+router.include_router(snapshot_router)
+router.include_router(graph_router)
 
 __all__ = ["router"]

server/src/ledgrab/api/auth.py

@@ -80,6 +80,7 @@ def verify_api_key(
     if not config.auth.api_keys:
         # No keys configured — allow loopback only.
         if _is_loopback(client_host):
+            request.state.auth_label = "anonymous"
             return "anonymous"
         # Allow caller to authenticate explicitly even without configured keys?
         # No — there are no keys to compare against. Reject.
@@ -123,6 +124,9 @@ def verify_api_key(
     # Log successful authentication
     logger.debug(f"Authenticated as: {authenticated_as}")
 
+    # Stash the friendly label so the access-log middleware can attribute the
+    # request to a client without re-running the token comparison.
+    request.state.auth_label = authenticated_as
     return authenticated_as
 
 

server/src/ledgrab/api/graph_schema.py

@@ -0,0 +1,501 @@
+"""Authoritative wiring-graph schema and topology engine.
+
+This module is the single source of truth for **which reference fields connect
+which entity kinds**. The frontend graph editor historically hard-coded the same
+information in two places (``graph-connections.ts`` ``CONNECTION_MAP`` and
+``graph-layout.ts`` ``buildGraph``); the ``GET /api/v1/graph/schema`` endpoint
+now serves this registry so the client can render ports and edges generically
+and the two never drift.
+
+This registry is a *superset* of the current frontend ``buildGraph``: it also
+declares real references that ``buildGraph`` does not yet draw (e.g.
+``value_source.value_source_id`` chaining and ``value_source.color_strip_source_id``).
+The backend is authoritative; the client is expected to converge on it.
+
+Everything in this module is pure (operates on plain dicts), so the topology
+build, dependency lookup, cycle and dangling-reference detection are all unit
+testable without booting the app or any store.
+
+Field-path grammar (the ``field`` of a :class:`ConnectionField`):
+
+* ``"device_id"``                  — a top-level string id.
+* ``"brightness.source_id"``       — a nested object; ``brightness`` may be a
+  plain number (unbound :class:`BindableFloat`) or ``{"value", "source_id"}``.
+* ``"settings.pattern_template_id"`` — arbitrarily deep object access.
+* ``"layers[].source_id"``         — ``layers`` is a list; read ``source_id``
+  from every element.
+* ``"calibration.lines[].picture_source_id"`` — object → list → field.
+"""
+
+from __future__ import annotations
+
+import logging
+from dataclasses import asdict, dataclass, is_dataclass
+from typing import Any
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass(frozen=True)
+class ConnectionField:
+    """One connectable reference: ``target_kind.field`` points at ``source_kind``."""
+
+    target_kind: str
+    """Entity kind that *holds* the reference (the consumer / referrer)."""
+    field: str
+    """Dot-path to the reference value (see module docstring grammar)."""
+    source_kind: str
+    """Entity kind being referenced (the producer / source)."""
+    edge_type: str
+    """Edge category, used by the client for colour and port grouping."""
+    bindable: bool = False
+    """True when the slot is a :class:`BindableFloat`/``BindableColor`` value binding."""
+    nested: bool = False
+    """True when the field lives inside a nested object/list (dotted path)."""
+
+    @property
+    def is_list(self) -> bool:
+        """True when any path segment iterates a list (``foo[]``)."""
+        return "[]" in self.field
+
+
+# ── Entity kinds & their human "type" attribute ────────────────────────────
+# Mirrors the frontend buildGraph(): kind → the serialized field that carries
+# the entity's subtype (used only for the node label / icon).
+NODE_TYPE_FIELD: dict[str, str] = {
+    "device": "device_type",
+    "capture_template": "engine_type",
+    "pp_template": "",
+    "audio_template": "engine_type",
+    "pattern_template": "",
+    "picture_source": "stream_type",
+    "audio_source": "source_type",
+    "value_source": "source_type",
+    "color_strip_source": "source_type",
+    "sync_clock": "",
+    "output_target": "target_type",
+    "scene_preset": "",
+    "automation": "",
+    "cspt": "",
+}
+
+ENTITY_KINDS: tuple[str, ...] = tuple(NODE_TYPE_FIELD.keys())
+
+
+# ── The registry ───────────────────────────────────────────────────────────
+# NOTE: ``gradient`` and ``ha_source`` reference fields are intentionally
+# omitted — they are not first-class graph node kinds, so wiring them would
+# only ever produce dangling-reference noise.
+CONNECTION_SCHEMA: tuple[ConnectionField, ...] = (
+    # ── Picture sources ──
+    ConnectionField("picture_source", "capture_template_id", "capture_template", "template"),
+    ConnectionField("picture_source", "source_stream_id", "picture_source", "picture"),
+    ConnectionField("picture_source", "postprocessing_template_id", "pp_template", "template"),
+    # ── Audio sources ──
+    ConnectionField("audio_source", "audio_template_id", "audio_template", "audio"),
+    ConnectionField("audio_source", "audio_source_id", "audio_source", "audio"),
+    # ── Value sources ──
+    ConnectionField("value_source", "audio_source_id", "audio_source", "audio"),
+    ConnectionField("value_source", "picture_source_id", "picture_source", "picture"),
+    ConnectionField("value_source", "value_source_id", "value_source", "value"),
+    ConnectionField("value_source", "color_strip_source_id", "color_strip_source", "colorstrip"),
+    # ── Color strip sources (top-level) ──
+    ConnectionField("color_strip_source", "picture_source_id", "picture_source", "picture"),
+    ConnectionField("color_strip_source", "audio_source_id", "audio_source", "audio"),
+    ConnectionField("color_strip_source", "clock_id", "sync_clock", "clock"),
+    ConnectionField("color_strip_source", "input_source_id", "color_strip_source", "colorstrip"),
+    ConnectionField("color_strip_source", "processing_template_id", "cspt", "template"),
+    # ── Color strip sources (BindableFloat value bindings) ──
+    *(
+        ConnectionField(
+            "color_strip_source",
+            f"{prop}.source_id",
+            "value_source",
+            "value",
+            bindable=True,
+            nested=True,
+        )
+        for prop in (
+            "smoothing",
+            "sensitivity",
+            "intensity",
+            "scale",
+            "speed",
+            "wind_strength",
+            "temperature_influence",
+            "sound_volume",
+            "timeout",
+            "brightness",
+        )
+    ),
+    # ── Color strip sources (BindableColor value bindings) ──
+    *(
+        ConnectionField(
+            "color_strip_source",
+            f"{prop}.source_id",
+            "value_source",
+            "value",
+            bindable=True,
+            nested=True,
+        )
+        for prop in ("color", "color_peak", "fallback_color", "default_color")
+    ),
+    # ── Color strip sources (composite layers / mapped zones / calibration) ──
+    ConnectionField(
+        "color_strip_source", "layers[].source_id", "color_strip_source", "colorstrip", nested=True
+    ),
+    ConnectionField(
+        "color_strip_source",
+        "layers[].brightness_source_id",
+        "value_source",
+        "value",
+        bindable=True,
+        nested=True,
+    ),
+    ConnectionField(
+        "color_strip_source", "layers[].processing_template_id", "cspt", "template", nested=True
+    ),
+    ConnectionField(
+        "color_strip_source", "zones[].source_id", "color_strip_source", "colorstrip", nested=True
+    ),
+    ConnectionField(
+        "color_strip_source",
+        "calibration.lines[].picture_source_id",
+        "picture_source",
+        "picture",
+        nested=True,
+    ),
+    # ── Output targets ──
+    ConnectionField("output_target", "device_id", "device", "device"),
+    ConnectionField("output_target", "color_strip_source_id", "color_strip_source", "colorstrip"),
+    ConnectionField("output_target", "picture_source_id", "picture_source", "picture"),
+    ConnectionField(
+        "output_target", "brightness.source_id", "value_source", "value", bindable=True, nested=True
+    ),
+    ConnectionField(
+        "output_target", "transition.source_id", "value_source", "value", bindable=True, nested=True
+    ),
+    ConnectionField(
+        "output_target", "settings.pattern_template_id", "pattern_template", "template", nested=True
+    ),
+    ConnectionField(
+        "output_target",
+        "settings.brightness.source_id",
+        "value_source",
+        "value",
+        bindable=True,
+        nested=True,
+    ),
+    # ── Scene presets ──
+    ConnectionField("scene_preset", "targets[].target_id", "output_target", "scene", nested=True),
+    # ── Automations ──
+    ConnectionField("automation", "scene_preset_id", "scene_preset", "scene"),
+    ConnectionField("automation", "deactivation_scene_preset_id", "scene_preset", "scene"),
+    # ── Devices ──
+    ConnectionField("device", "default_css_processing_template_id", "cspt", "template"),
+)
+
+
+def schema_for_kind(kind: str) -> list[ConnectionField]:
+    """Every connectable field whose *referrer* is ``kind``."""
+    return [c for c in CONNECTION_SCHEMA if c.target_kind == kind]
+
+
+def schema_as_dicts() -> list[dict[str, Any]]:
+    """Serialize the registry for the ``/graph/schema`` endpoint."""
+    return [
+        {
+            "target_kind": c.target_kind,
+            "field": c.field,
+            "source_kind": c.source_kind,
+            "edge_type": c.edge_type,
+            "bindable": c.bindable,
+            "nested": c.nested,
+            "is_list": c.is_list,
+        }
+        for c in CONNECTION_SCHEMA
+    ]
+
+
+# ── Reference extraction ────────────────────────────────────────────────────
+
+
+def extract_refs(entity: dict[str, Any], field_path: str) -> list[str]:
+    """Resolve a (possibly nested/list) ``field_path`` to its referenced ids.
+
+    Returns only non-empty string ids. Tolerant of missing keys, ``None``
+    values and unbound bindables (a plain number where an object was expected).
+    """
+    current: list[Any] = [entity]
+    for segment in field_path.split("."):
+        is_list = segment.endswith("[]")
+        key = segment[:-2] if is_list else segment
+        nxt: list[Any] = []
+        for obj in current:
+            if not isinstance(obj, dict):
+                continue
+            val = obj.get(key)
+            if is_list:
+                if isinstance(val, list):
+                    nxt.extend(val)
+            elif val is not None:
+                nxt.append(val)
+        current = nxt
+    return [v for v in current if isinstance(v, str) and v]
+
+
+def serialize_entity(model: Any) -> dict[str, Any]:
+    """Best-effort serialize a storage model to a plain dict for graph use.
+
+    Prefers ``dataclasses.asdict`` (pure structural, recurses bindables/lists,
+    invokes no managers), falling back to ``to_dict()`` then ``{}``.
+    """
+    if is_dataclass(model) and not isinstance(model, type):
+        try:
+            return asdict(model)
+        except Exception as exc:  # noqa: BLE001 — defensive: never let one model break the graph
+            logger.debug("graph: asdict failed for %r: %s", type(model).__name__, exc)
+    to_dict = getattr(model, "to_dict", None)
+    if callable(to_dict):
+        try:
+            result = to_dict()
+            if isinstance(result, dict):
+                return result
+        except Exception as exc:  # noqa: BLE001
+            logger.debug("graph: to_dict failed for %r: %s", type(model).__name__, exc)
+    logger.warning(
+        "graph: could not serialize model %r; excluding from graph", type(model).__name__
+    )
+    return {}
+
+
+# ── Topology / validation ───────────────────────────────────────────────────
+
+
+def _node_from(kind: str, entity: dict[str, Any]) -> dict[str, Any] | None:
+    eid = entity.get("id")
+    if not isinstance(eid, str) or not eid:
+        return None
+    type_field = NODE_TYPE_FIELD.get(kind, "")
+    subtype = entity.get(type_field, "") if type_field else ""
+    return {
+        "id": eid,
+        "kind": kind,
+        "name": entity.get("name") or eid,
+        "type": subtype if isinstance(subtype, str) else "",
+    }
+
+
+def build_topology(entities_by_kind: dict[str, list[dict[str, Any]]]) -> dict[str, Any]:
+    """Build the full wiring graph + a validation report.
+
+    Args:
+        entities_by_kind: ``{kind: [serialized_entity_dict, ...]}``.
+
+    Returns a dict with ``nodes``, ``edges`` and ``issues`` (``orphans``,
+    ``broken_refs``, ``cycles``).
+    """
+    nodes: list[dict[str, Any]] = []
+    node_ids: set[str] = set()
+    for kind in ENTITY_KINDS:
+        for entity in entities_by_kind.get(kind, []):
+            node = _node_from(kind, entity)
+            if node and node["id"] not in node_ids:
+                node_ids.add(node["id"])
+                nodes.append(node)
+
+    edges: list[dict[str, Any]] = []
+    broken_refs: list[dict[str, str]] = []
+    for cf in CONNECTION_SCHEMA:
+        for entity in entities_by_kind.get(cf.target_kind, []):
+            referrer = entity.get("id")
+            if not isinstance(referrer, str) or not referrer:
+                continue
+            for ref in extract_refs(entity, cf.field):
+                if ref not in node_ids:
+                    broken_refs.append({"ref": ref, "by": referrer, "field": cf.field})
+                    continue
+                edges.append(
+                    {
+                        "from": ref,
+                        "to": referrer,
+                        "field": cf.field,
+                        "edge_type": cf.edge_type,
+                        "nested": cf.nested,
+                    }
+                )
+
+    connected: set[str] = set()
+    for e in edges:
+        connected.add(e["from"])
+        connected.add(e["to"])
+    orphans = sorted(nid for nid in node_ids if nid not in connected)
+    cycles = sorted(detect_cycles(edges))
+
+    return {
+        "nodes": nodes,
+        "edges": edges,
+        "issues": {
+            "orphans": orphans,
+            "broken_refs": broken_refs,
+            "cycles": cycles,
+        },
+    }
+
+
+def find_dependents(
+    entities_by_kind: dict[str, list[dict[str, Any]]], kind: str, entity_id: str
+) -> list[dict[str, str]]:
+    """Return every entity that references ``(kind, entity_id)``.
+
+    ``kind`` is the kind of the *referenced* entity; matching schema entries are
+    those whose ``source_kind == kind``.
+    """
+    name_by_id: dict[str, str] = {}
+    for k in ENTITY_KINDS:
+        for entity in entities_by_kind.get(k, []):
+            eid = entity.get("id")
+            if isinstance(eid, str):
+                name_by_id[eid] = entity.get("name") or eid
+
+    dependents: list[dict[str, str]] = []
+    seen: set[tuple[str, str]] = set()
+    for cf in CONNECTION_SCHEMA:
+        if cf.source_kind != kind:
+            continue
+        for entity in entities_by_kind.get(cf.target_kind, []):
+            referrer = entity.get("id")
+            if not isinstance(referrer, str):
+                continue
+            if entity_id in extract_refs(entity, cf.field):
+                key = (referrer, cf.field)
+                if key in seen:
+                    continue
+                seen.add(key)
+                dependents.append(
+                    {
+                        "id": referrer,
+                        "kind": cf.target_kind,
+                        "name": name_by_id.get(referrer, referrer),
+                        "field": cf.field,
+                    }
+                )
+    return dependents
+
+
+def detect_cycles(edges: list[dict[str, Any]]) -> set[str]:
+    """Return every node id that participates in a directed cycle (from→to)."""
+    adj: dict[str, list[str]] = {}
+    for e in edges:
+        adj.setdefault(e["from"], []).append(e["to"])
+
+    WHITE, GRAY, BLACK = 0, 1, 2
+    color: dict[str, int] = {}
+    in_cycle: set[str] = set()
+
+    for start in list(adj.keys()):
+        if color.get(start, WHITE) != WHITE:
+            continue
+        stack: list[tuple[str, int]] = [(start, 0)]
+        path: list[str] = [start]
+        color[start] = GRAY
+        while stack:
+            node, idx = stack[-1]
+            neighbors = adj.get(node, [])
+            if idx < len(neighbors):
+                stack[-1] = (node, idx + 1)
+                nxt = neighbors[idx]
+                c = color.get(nxt, WHITE)
+                if c == GRAY:
+                    if nxt in path:
+                        i = path.index(nxt)
+                        in_cycle.update(path[i:])
+                elif c == WHITE:
+                    color[nxt] = GRAY
+                    path.append(nxt)
+                    stack.append((nxt, 0))
+            else:
+                color[node] = BLACK
+                if path and path[-1] == node:
+                    path.pop()
+                stack.pop()
+    return in_cycle
+
+
+def _reachable(edges: list[dict[str, Any]], start: str, goal: str) -> bool:
+    """True if ``goal`` is reachable from ``start`` following from→to edges."""
+    if start == goal:
+        return True
+    adj: dict[str, list[str]] = {}
+    for e in edges:
+        adj.setdefault(e["from"], []).append(e["to"])
+    seen = {start}
+    queue = [start]
+    while queue:
+        cur = queue.pop()
+        for nxt in adj.get(cur, []):
+            if nxt == goal:
+                return True
+            if nxt not in seen:
+                seen.add(nxt)
+                queue.append(nxt)
+    return False
+
+
+def would_create_cycle(edges: list[dict[str, Any]], source_id: str, target_id: str) -> bool:
+    """Would wiring ``source_id`` into ``target_id`` (edge source→target) loop?
+
+    A cycle forms if ``source_id`` is already reachable from ``target_id`` via
+    the existing data-flow edges (so the new edge would close the loop), or the
+    two are the same node.
+    """
+    if source_id == target_id:
+        return True
+    return _reachable(edges, target_id, source_id)
+
+
+def _entity_exists(
+    entities_by_kind: dict[str, list[dict[str, Any]]], kind: str, entity_id: str
+) -> bool:
+    return any(e.get("id") == entity_id for e in entities_by_kind.get(kind, []))
+
+
+def validate_connection(
+    entities_by_kind: dict[str, list[dict[str, Any]]],
+    target_kind: str,
+    target_id: str,
+    field: str,
+    source_id: str,
+) -> tuple[bool, str | None]:
+    """Validate a proposed wiring edit before it is persisted.
+
+    Checks, in order: the field is a known connectable reference; the target
+    exists; (when not detaching) the source exists and is of the registry's
+    expected kind; and the edit would not create a dependency cycle. Returns
+    ``(ok, error_message)``. Detaching (empty ``source_id``) is always allowed.
+    """
+    cf = next(
+        (c for c in CONNECTION_SCHEMA if c.target_kind == target_kind and c.field == field),
+        None,
+    )
+    if cf is None:
+        return False, f"Unknown connection field: {target_kind}.{field}"
+    if cf.is_list:
+        # List slots (layers/zones/scene targets) hold many edges sharing the
+        # same (to, field); without an element index this endpoint can't model
+        # which one is being replaced for the cycle check. Edit those via the
+        # entity editor.
+        return False, f"List connection '{field}' must be edited via the entity editor"
+    if not _entity_exists(entities_by_kind, target_kind, target_id):
+        return False, f"Target entity not found: {target_id}"
+    if not source_id:
+        return True, None  # detaching a slot is always valid
+    if not _entity_exists(entities_by_kind, cf.source_kind, source_id):
+        return False, f"Source {cf.source_kind} not found: {source_id}"
+    # Cycle check: ignore the edge currently occupying this slot, since the
+    # write replaces it.
+    topo = build_topology(entities_by_kind)
+    edges = [e for e in topo["edges"] if not (e["to"] == target_id and e["field"] == field)]
+    if would_create_cycle(edges, source_id, target_id):
+        return False, "Connection would create a dependency cycle"
+    return True, None

server/src/ledgrab/api/routes/_mqtt_validation.py

@@ -0,0 +1,25 @@
+"""Shared MQTT-source validation for route handlers.
+
+Both the device routes and the output-target routes accept an
+``mqtt_source_id`` that must reference an existing ``MQTTSource``. This module
+is the single source of truth for that check so the two callers cannot drift.
+"""
+
+from fastapi import HTTPException
+
+from ledgrab.storage.base_store import EntityNotFoundError
+from ledgrab.storage.mqtt_source_store import MQTTSourceStore
+
+
+def validate_mqtt_source_exists(mqtt_store: MQTTSourceStore, mqtt_source_id: str | None) -> None:
+    """Ensure a referenced MQTT source exists.
+
+    Empty / ``None`` is allowed (unconfigured = "first available broker").
+    Raises ``HTTPException(422)`` if a non-empty id does not resolve.
+    """
+    if not mqtt_source_id:
+        return
+    try:
+        mqtt_store.get(mqtt_source_id)
+    except (ValueError, EntityNotFoundError):
+        raise HTTPException(status_code=422, detail=f"MQTT source {mqtt_source_id} not found")

server/src/ledgrab/api/routes/devices.py

@@ -13,6 +13,7 @@ from ledgrab.core.devices.led_client import (
 from ledgrab.api.dependencies import (
     fire_entity_event,
     get_device_store,
+    get_mqtt_store,
     get_output_target_store,
     get_processor_manager,
 )
@@ -33,10 +34,13 @@ from ledgrab.api.schemas.devices import (
 )
 from ledgrab.core.processing.processor_manager import ProcessorManager
 from ledgrab.storage import DeviceStore
+from ledgrab.storage.mqtt_source_store import MQTTSourceStore
 from ledgrab.storage.output_target_store import OutputTargetStore
 from ledgrab.utils import get_logger
 from ledgrab.utils.url_scheme import infer_http_scheme
 
+from ._mqtt_validation import validate_mqtt_source_exists
+
 logger = get_logger(__name__)
 
 router = APIRouter()
@@ -105,6 +109,7 @@ def _device_to_response(device) -> DeviceResponse:
         gamesense_device_type=device.gamesense_device_type,
         ble_family=device.ble_family,
         ble_govee_key=device.ble_govee_key,
+        mqtt_source_id=getattr(device, "mqtt_source_id", "") or "",
         default_css_processing_template_id=device.default_css_processing_template_id,
         group_device_ids=device.group_device_ids,
         group_mode=device.group_mode,
@@ -124,11 +129,13 @@ async def create_device(
     _auth: AuthRequired,
     store: DeviceStore = Depends(get_device_store),
     manager: ProcessorManager = Depends(get_processor_manager),
+    mqtt_store: MQTTSourceStore = Depends(get_mqtt_store),
 ):
     """Create and attach a new LED device."""
     try:
         device_type = device_data.device_type
         logger.info(f"Creating {device_type} device: {device_data.name}")
+        validate_mqtt_source_exists(mqtt_store, device_data.mqtt_source_id)
 
         # ── Group device: validate children + compute LED count ──
         if device_type == "group":
@@ -287,6 +294,7 @@ async def create_device(
             gamesense_device_type=device_data.gamesense_device_type or "keyboard",
             ble_family=device_data.ble_family or "",
             ble_govee_key=device_data.ble_govee_key or "",
+            mqtt_source_id=device_data.mqtt_source_id or "",
             group_device_ids=group_device_ids,
             group_mode=group_mode,
         )
@@ -543,12 +551,14 @@ async def update_device(
     _auth: AuthRequired,
     store: DeviceStore = Depends(get_device_store),
     manager: ProcessorManager = Depends(get_processor_manager),
+    mqtt_store: MQTTSourceStore = Depends(get_mqtt_store),
 ):
     """Update device information."""
     try:
         # Group-specific validation before applying update
         existing = store.get_device(device_id)
         is_group = existing.device_type == "group"
+        validate_mqtt_source_exists(mqtt_store, update_data.mqtt_source_id)
 
         # Normalize URL the same way we do on create:
         #   * always rstrip trailing slashes (so PUT-with-trailing-/ matches
@@ -634,6 +644,7 @@ async def update_device(
             gamesense_device_type=update_data.gamesense_device_type,
             ble_family=update_data.ble_family,
             ble_govee_key=update_data.ble_govee_key,
+            mqtt_source_id=update_data.mqtt_source_id,
             group_device_ids=update_data.group_device_ids,
             group_mode=update_data.group_mode,
             icon=update_data.icon,
@@ -669,6 +680,10 @@ async def update_device(
         fire_entity_event("device", "updated", device_id)
         return _device_to_response(device)
 
+    except HTTPException:
+        # Intentional 4xx (e.g. unknown mqtt_source_id, group validation)
+        # must propagate unchanged — not be masked as a 500.
+        raise
     except ValueError as e:
         raise HTTPException(status_code=404, detail=str(e))
     except Exception as e:
@@ -777,6 +792,32 @@ async def ping_device(
 # ===== WLED BRIGHTNESS ENDPOINTS =====
 
 
+async def resolve_device_brightness(device, manager: ProcessorManager) -> int | None:
+    """Resolve a device's current brightness for aggregate/batch reads.
+
+    Mirrors GET /brightness but degrades to ``None`` instead of raising, so one
+    unreachable device can't fail a whole snapshot. Reads the server-side cache
+    first and only touches hardware when the cache is cold, then populates it so
+    subsequent reads are I/O-free.
+    """
+    if "brightness_control" not in get_device_capabilities(device.device_type):
+        return None
+    ds = manager.find_device_state(device.id)
+    if ds and ds.hardware_brightness is not None:
+        return ds.hardware_brightness
+    try:
+        provider = get_provider(device.device_type)
+        bri = await provider.get_brightness(device.url)
+        if ds:
+            ds.hardware_brightness = bri
+        return bri
+    except NotImplementedError:
+        return device.software_brightness
+    except Exception as e:
+        logger.warning("Failed to resolve brightness for device %s: %s", device.id, e)
+        return None
+
+
 @router.get("/api/v1/devices/{device_id}/brightness", tags=["Settings"])
 async def get_device_brightness(
     device_id: str,

server/src/ledgrab/api/routes/graph.py

@@ -0,0 +1,124 @@
+"""Wiring-graph endpoints: schema registry, full topology, and dependents.
+
+These power the visual graph editor (and any other client) with a single
+authoritative view of how entities are wired together:
+
+* ``GET /api/v1/graph/schema``                  — the connectable-field registry.
+* ``GET /api/v1/graph``                          — nodes + edges + validation.
+* ``GET /api/v1/graph/dependents/{kind}/{id}``   — what references an entity.
+
+All heavy logic lives in :mod:`ledgrab.api.graph_schema` (pure, unit-tested);
+this layer only gathers serialized entities from the stores and delegates.
+"""
+
+from __future__ import annotations
+
+import logging
+from typing import Any, Callable
+
+from fastapi import APIRouter, HTTPException
+from fastapi.concurrency import run_in_threadpool
+from pydantic import BaseModel, Field
+
+from ledgrab.api import dependencies as deps
+from ledgrab.api.auth import AuthRequired
+from ledgrab.api.graph_schema import (
+    ENTITY_KINDS,
+    NODE_TYPE_FIELD,
+    build_topology,
+    find_dependents,
+    schema_as_dicts,
+    serialize_entity,
+    validate_connection,
+)
+
+logger = logging.getLogger(__name__)
+
+
+class ConnectionValidationRequest(BaseModel):
+    """A proposed wiring edit: set ``target_kind.field`` to ``source_id``."""
+
+    target_kind: str
+    target_id: str
+    field: str
+    source_id: str = Field(default="", description="Empty string detaches the slot.")
+
+
+router = APIRouter()
+
+# kind → dependency getter for the store that owns that entity kind.
+_KIND_STORES: dict[str, Callable[[], Any]] = {
+    "device": deps.get_device_store,
+    "capture_template": deps.get_template_store,
+    "pp_template": deps.get_pp_template_store,
+    "audio_template": deps.get_audio_template_store,
+    "pattern_template": deps.get_pattern_template_store,
+    "picture_source": deps.get_picture_source_store,
+    "audio_source": deps.get_audio_source_store,
+    "value_source": deps.get_value_source_store,
+    "color_strip_source": deps.get_color_strip_store,
+    "sync_clock": deps.get_sync_clock_store,
+    "output_target": deps.get_output_target_store,
+    "scene_preset": deps.get_scene_preset_store,
+    "automation": deps.get_automation_store,
+    "cspt": deps.get_cspt_store,
+}
+
+
+def _gather_entities() -> dict[str, list[dict[str, Any]]]:
+    """Serialize every entity, keyed by kind. Missing stores yield ``[]``."""
+    out: dict[str, list[dict[str, Any]]] = {}
+    for kind, getter in _KIND_STORES.items():
+        try:
+            store = getter()
+            models = store.get_all()
+        except (
+            Exception
+        ) as exc:  # noqa: BLE001 — an uninitialized/failing store must not 500 the graph
+            logger.warning("graph: store for kind %s unavailable: %s", kind, exc)
+            out[kind] = []
+            continue
+        out[kind] = [serialize_entity(m) for m in models]
+    return out
+
+
+@router.get("/api/v1/graph/schema", tags=["Graph"])
+async def get_graph_schema(_auth: AuthRequired) -> dict[str, Any]:
+    """Return the authoritative registry of connectable reference fields."""
+    return {
+        "kinds": list(ENTITY_KINDS),
+        "node_type_field": NODE_TYPE_FIELD,
+        "connections": schema_as_dicts(),
+    }
+
+
+@router.get("/api/v1/graph", tags=["Graph"])
+async def get_graph(_auth: AuthRequired) -> dict[str, Any]:
+    """Return the full wiring topology (nodes + edges) and a validation report."""
+    entities = await run_in_threadpool(_gather_entities)
+    return build_topology(entities)
+
+
+@router.get("/api/v1/graph/dependents/{kind}/{entity_id}", tags=["Graph"])
+async def get_graph_dependents(kind: str, entity_id: str, _auth: AuthRequired) -> dict[str, Any]:
+    """Return every entity that references ``(kind, entity_id)``."""
+    if kind not in ENTITY_KINDS:
+        raise HTTPException(status_code=404, detail=f"Unknown entity kind: {kind}")
+    entities = await run_in_threadpool(_gather_entities)
+    return {"dependents": find_dependents(entities, kind, entity_id)}
+
+
+@router.post("/api/v1/graph/validate-connection", tags=["Graph"])
+async def validate_graph_connection(
+    body: ConnectionValidationRequest, _auth: AuthRequired
+) -> dict[str, Any]:
+    """Validate a proposed wiring edit (existence + source kind + no cycle).
+
+    The graph editor calls this before persisting a drag-connect so it can
+    refuse edits that would dangle a reference or create a dependency loop.
+    """
+    entities = await run_in_threadpool(_gather_entities)
+    ok, error = validate_connection(
+        entities, body.target_kind, body.target_id, body.field, body.source_id
+    )
+    return {"ok": ok, "error": error}

server/src/ledgrab/api/routes/output_targets.py

@@ -49,6 +49,8 @@ from ledgrab.storage.value_source_store import ValueSourceStore
 from ledgrab.utils import get_logger
 from ledgrab.storage.base_store import EntityNotFoundError
 
+from ._mqtt_validation import validate_mqtt_source_exists
+
 logger = get_logger(__name__)
 
 router = APIRouter()
@@ -270,16 +272,6 @@ def _validate_device_exists(device_store: DeviceStore, device_id: str) -> None:
         raise HTTPException(status_code=422, detail=f"Device {device_id} not found")
 
 
-def _validate_mqtt_source_exists(mqtt_store: MQTTSourceStore, mqtt_source_id: str) -> None:
-    """Ensure the referenced MQTT source exists. Empty id is allowed (unconfigured)."""
-    if not mqtt_source_id:
-        return
-    try:
-        mqtt_store.get(mqtt_source_id)
-    except (ValueError, EntityNotFoundError):
-        raise HTTPException(status_code=422, detail=f"MQTT source {mqtt_source_id} not found")
-
-
 @router.post(
     "/api/v1/output-targets", response_model=OutputTargetResponse, tags=["Targets"], status_code=201
 )
@@ -333,7 +325,7 @@ async def create_target(
             case Z2MLightOutputTargetCreate():
                 if data.source_kind == "color_vs":
                     _validate_color_value_source(value_source_store, data.color_value_source_id)
-                _validate_mqtt_source_exists(mqtt_store, data.mqtt_source_id)
+                validate_mqtt_source_exists(mqtt_store, data.mqtt_source_id)
                 target = target_store.create_z2m_light_target(
                     name=data.name,
                     description=data.description,
@@ -540,7 +532,7 @@ async def update_target(
                     )
                     _validate_color_value_source(value_source_store, effective_id)
                 if data.mqtt_source_id:
-                    _validate_mqtt_source_exists(mqtt_store, data.mqtt_source_id)
+                    validate_mqtt_source_exists(mqtt_store, data.mqtt_source_id)
                 target = target_store.update_z2m_light_target(
                     target_id,
                     name=data.name,

server/src/ledgrab/api/routes/snapshot.py

@@ -0,0 +1,201 @@
+"""Aggregated snapshot endpoint for low-overhead polling clients.
+
+Returns, in a single response, everything the Home Assistant integration's
+coordinator needs per poll: all output targets with processing state + metrics,
+all devices with brightness, the color-strip / value-source / scene-preset /
+sync-clock lists, and the system block (performance, health, update).
+
+This collapses the integration's previous ~2N+M request fan-out (per-target
+``/state`` + ``/metrics`` and per-device ``/brightness``) into one round trip.
+
+The handler delegates to the existing list/batch route handlers so the response
+sub-shapes stay byte-identical to the individual endpoints — no shaping logic is
+duplicated here.
+
+Callers that don't need the whole payload can pass ``?include=`` with a
+comma-separated subset of section names (the response keys). Omitting it returns
+every section. Gating is per section, so an excluded section also skips its
+server-side work — dropping ``device_brightness`` avoids cold-cache hardware
+probes, and dropping ``system`` skips the (blocking) NVML performance query.
+"""
+
+import asyncio
+from typing import Any
+
+from fastapi import APIRouter, Depends, HTTPException, Query, Request
+from fastapi.concurrency import run_in_threadpool
+
+from ledgrab.api.auth import AuthRequired
+from ledgrab.api.dependencies import (
+    get_color_strip_store,
+    get_device_store,
+    get_output_target_store,
+    get_processor_manager,
+    get_scene_preset_store,
+    get_sync_clock_manager,
+    get_sync_clock_store,
+    get_update_service,
+    get_value_source_store,
+)
+from ledgrab.api.schemas.update import UpdateStatusResponse
+from ledgrab.utils import get_logger
+
+from .color_strip_sources.crud import list_color_strip_sources
+from .devices import list_devices, resolve_device_brightness
+from .output_targets import batch_target_metrics, batch_target_states, list_targets
+from .scene_presets import list_scene_presets
+from .sync_clocks import list_sync_clocks
+from .system import get_system_performance, health_check
+from .update import get_update_status
+from .value_sources import list_value_sources
+
+logger = get_logger(__name__)
+
+router = APIRouter()
+
+# Selectable snapshot sections — these are exactly the response top-level keys.
+SNAPSHOT_SECTIONS = (
+    "targets",
+    "target_states",
+    "target_metrics",
+    "devices",
+    "device_brightness",
+    "css_sources",
+    "value_sources",
+    "scene_presets",
+    "sync_clocks",
+    "system",
+)
+_SECTION_SET = frozenset(SNAPSHOT_SECTIONS)
+
+
+def _resolve_sections(include: str | None) -> frozenset[str]:
+    """Validate the ``include`` query param into the set of sections to emit.
+
+    ``None``/empty → every section. Unknown names are rejected with 422 so a
+    typo fails loudly instead of silently returning a smaller payload.
+    """
+    if not include:
+        return _SECTION_SET
+    requested = {part.strip() for part in include.split(",") if part.strip()}
+    unknown = requested - _SECTION_SET
+    if unknown:
+        raise HTTPException(
+            status_code=422,
+            detail=(
+                f"Unknown snapshot section(s): {', '.join(sorted(unknown))}. "
+                f"Valid sections: {', '.join(SNAPSHOT_SECTIONS)}."
+            ),
+        )
+    return frozenset(requested)
+
+
+async def _safe_section(awaitable, label: str):
+    """Await a section, degrading to ``None`` on failure instead of 500-ing.
+
+    The snapshot is a resilience-oriented poll surface: one failing section
+    (e.g. NVML performance probing) must not fail the whole response. This
+    preserves the per-section fault isolation the HA coordinator relied on
+    before these calls were merged into one request — the coordinator already
+    tolerates a ``None`` section.
+    """
+    try:
+        return await awaitable
+    except Exception:
+        logger.warning("snapshot: section %r failed, returning null", label, exc_info=True)
+        return None
+
+
+async def _update_status_model(_auth, update_service) -> UpdateStatusResponse:
+    """Fetch update status and coerce it through the response model.
+
+    The standalone ``/system/update/status`` endpoint declares
+    ``response_model=UpdateStatusResponse``; coercing here keeps the snapshot's
+    ``system.update`` field identical to that endpoint rather than emitting the
+    service's raw dict unfiltered.
+    """
+    raw = await get_update_status(_auth, update_service)
+    return UpdateStatusResponse.model_validate(raw)
+
+
+@router.get("/api/v1/snapshot", tags=["Snapshot"])
+async def get_snapshot(
+    request: Request,
+    _auth: AuthRequired,
+    include: str | None = Query(
+        None,
+        description=(
+            "Comma-separated subset of sections to include. Omit for all. "
+            "Valid: " + ", ".join(SNAPSHOT_SECTIONS)
+        ),
+    ),
+    manager=Depends(get_processor_manager),
+    target_store=Depends(get_output_target_store),
+    device_store=Depends(get_device_store),
+    css_store=Depends(get_color_strip_store),
+    value_store=Depends(get_value_source_store),
+    preset_store=Depends(get_scene_preset_store),
+    clock_store=Depends(get_sync_clock_store),
+    clock_manager=Depends(get_sync_clock_manager),
+    update_service=Depends(get_update_service),
+) -> dict[str, Any]:
+    """Return the full poll payload (or a requested subset) in one response.
+
+    Shape (a key is present only when its section is requested)::
+
+        {
+          "targets": [<OutputTargetResponse>, ...],
+          "target_states": {target_id: <state>, ...},
+          "target_metrics": {target_id: <metrics>, ...},
+          "devices": [<DeviceResponse>, ...],
+          "device_brightness": {device_id: int | null, ...},
+          "css_sources": [...],
+          "value_sources": [...],
+          "scene_presets": [...],
+          "sync_clocks": [...],
+          "system": {"performance": {...}, "health": {...}, "update": {...}}
+        }
+    """
+    sections = _resolve_sections(include)
+    result: dict[str, Any] = {}
+
+    if "targets" in sections:
+        result["targets"] = (await list_targets(_auth, target_store)).targets
+    if "target_states" in sections:
+        result["target_states"] = (await batch_target_states(_auth, manager))["states"]
+    if "target_metrics" in sections:
+        result["target_metrics"] = (await batch_target_metrics(_auth, manager))["metrics"]
+    if "devices" in sections:
+        result["devices"] = (await list_devices(_auth, device_store)).devices
+    if "device_brightness" in sections:
+        device_models = device_store.get_all_devices()
+        brightness_values = await asyncio.gather(
+            *(resolve_device_brightness(d, manager) for d in device_models),
+            return_exceptions=True,
+        )
+        result["device_brightness"] = {
+            model.id: (None if isinstance(value, BaseException) else value)
+            for model, value in zip(device_models, brightness_values)
+        }
+    if "css_sources" in sections:
+        css = await list_color_strip_sources(_auth, css_store, manager)
+        result["css_sources"] = css.sources
+    if "value_sources" in sections:
+        result["value_sources"] = (await list_value_sources(_auth, None, value_store)).sources
+    if "scene_presets" in sections:
+        result["scene_presets"] = (await list_scene_presets(_auth, preset_store)).presets
+    if "sync_clocks" in sections:
+        clocks = await list_sync_clocks(_auth, clock_store, clock_manager)
+        result["sync_clocks"] = clocks.clocks
+    if "system" in sections:
+        result["system"] = {
+            "performance": await _safe_section(
+                run_in_threadpool(get_system_performance, _auth), "system.performance"
+            ),
+            "health": await _safe_section(health_check(request), "system.health"),
+            "update": await _safe_section(
+                _update_status_model(_auth, update_service), "system.update"
+            ),
+        }
+
+    return result

server/src/ledgrab/api/schemas/devices.py

@@ -131,6 +131,11 @@ class DeviceCreate(BaseModel):
         None,
         description="Govee AES key (hex) — required for encrypted Govee firmware",
     )
+    # MQTT (multi-broker) field
+    mqtt_source_id: str | None = Field(
+        None,
+        description="MQTT source (broker) ID for device_type=mqtt. Empty = first available broker.",
+    )
     default_css_processing_template_id: str | None = Field(
         None, description="Default color strip processing template ID"
     )
@@ -217,6 +222,9 @@ class DeviceUpdate(BaseModel):
     ble_govee_key: str | None = Field(
         None, description="Govee AES key (hex) — required for encrypted Govee firmware"
     )
+    mqtt_source_id: str | None = Field(
+        None, description="MQTT source (broker) ID for device_type=mqtt"
+    )
     default_css_processing_template_id: str | None = Field(
         None, description="Default color strip processing template ID"
     )
@@ -436,6 +444,9 @@ class DeviceResponse(BaseModel):
     ble_govee_key: str = Field(
         default="", description="Govee AES key (hex) — required for encrypted Govee firmware"
     )
+    mqtt_source_id: str = Field(
+        default="", description="MQTT source (broker) ID for device_type=mqtt"
+    )
     default_css_processing_template_id: str = Field(
         default="", description="Default color strip processing template ID"
     )

server/src/ledgrab/demo.py

@@ -15,6 +15,7 @@ def main():
 
     import uvicorn
     from ledgrab.config import get_config
+    from ledgrab.shutdown_state import GRACEFUL_SHUTDOWN_TIMEOUT
 
     config = get_config()
     uvicorn.run(
@@ -22,7 +23,14 @@ def main():
         host=config.server.host,
         port=config.server.port,
         log_level=config.server.log_level.lower(),
+        # Access logging is handled by the _access_log middleware (with token
+        # attribution); disable uvicorn's to avoid duplicate lines.
+        access_log=False,
         reload=False,
+        # Bound the graceful-shutdown wait so Ctrl+C with the UI open still
+        # runs the lifespan shutdown instead of hanging on a lingering events
+        # WebSocket — see shutdown_state.
+        timeout_graceful_shutdown=GRACEFUL_SHUTDOWN_TIMEOUT,
     )
 
 

server/src/ledgrab/main.py

@@ -2,6 +2,7 @@
 
 import asyncio
 import sys
+import time
 from contextlib import asynccontextmanager
 from pathlib import Path
 from typing import Awaitable
@@ -74,7 +75,7 @@ config = get_config()
 
 # The shutdown-complete signal is owned by a leaf module so ``__main__``
 # can import it without dragging in this module's heavy global state.
-from ledgrab.shutdown_state import shutdown_complete  # noqa: E402
+from ledgrab.shutdown_state import GRACEFUL_SHUTDOWN_TIMEOUT, shutdown_complete  # noqa: E402
 
 
 def _migrate_legacy_data_location() -> None:
@@ -577,6 +578,33 @@ async def _security_headers(request: Request, call_next):
     return response
 
 
+# Middleware: structured access log enriched with the authenticated token's
+# friendly label (the key name from auth.api_keys), so requests can be
+# attributed to a specific client (e.g. "homeassistant" vs "android"). The
+# label is set onto request.state by verify_api_key; endpoints without auth
+# (or failed auth) log "unauthenticated". Only the label is logged — never the
+# token secret. Registered last so it runs outermost: it measures total
+# handling time and always records the final status, even on error.
+@app.middleware("http")
+async def _access_log(request: Request, call_next):
+    start = time.perf_counter()
+    status_code = 500
+    try:
+        response = await call_next(request)
+        status_code = response.status_code
+        return response
+    finally:
+        logger.info(
+            "http_request",
+            method=request.method,
+            path=request.url.path,
+            status=status_code,
+            token=getattr(request.state, "auth_label", None) or "unauthenticated",
+            client=request.client.host if request.client else None,
+            duration_ms=round((time.perf_counter() - start) * 1000, 1),
+        )
+
+
 # ── Auth-gated OpenAPI surface ────────────────────────────────────────────
 # Re-add the docs endpoints we disabled above, now protected by the same
 # Bearer auth as the rest of the API. When auth is unconfigured, loopback
@@ -645,5 +673,13 @@ if __name__ == "__main__":
         host=config.server.host,
         port=config.server.port,
         log_level=config.server.log_level.lower(),
+        # Our _access_log middleware emits a richer structured line (incl. the
+        # authenticated token label), so suppress uvicorn's default access log
+        # to avoid two lines per request.
+        access_log=False,
         reload=False,  # Disabled due to watchfiles infinite reload loop
+        # Bound the graceful-shutdown wait so Ctrl+C with the UI open still
+        # runs the lifespan shutdown (stop targets + DB checkpoint) instead of
+        # hanging on a lingering events WebSocket — see shutdown_state.
+        timeout_graceful_shutdown=GRACEFUL_SHUTDOWN_TIMEOUT,
     )

server/src/ledgrab/shutdown_state.py

@@ -16,3 +16,15 @@ they release Windows / unblock only once cleanup is genuinely done.
 import threading
 
 shutdown_complete: threading.Event = threading.Event()
+
+# Bound uvicorn's graceful-shutdown wait (``uvicorn.Config(timeout_graceful_shutdown=...)``).
+# uvicorn defaults this to ``None`` — ``Server.shutdown()`` then waits *forever*
+# for open connections (and their tasks) to drain before it runs the lifespan
+# shutdown. The events WebSocket handler blocks on ``queue.get()`` and the
+# browser auto-reconnects, so connections never drain on their own. Without a
+# bound, the lifespan shutdown — which stops LED targets and checkpoints the
+# DB — never runs: targets stay lit and the process can't exit (leftover
+# processor threads). Shared by both the desktop (__main__) and Android
+# (android_entry) launchers. Keep it small so OS-shutdown cleanup still fits
+# Windows' ~20 s budget; it is spent BEFORE the lifespan's own ~16 s budget.
+GRACEFUL_SHUTDOWN_TIMEOUT: int = 3

server/src/ledgrab/static/css/graph-editor.css

@@ -495,6 +495,18 @@ html:has(#tab-graph.active) {
     opacity: 0.95;
 }
 
+/* Custom per-entity icon: the embedded SVG strokes with currentColor, so it is
+   tinted via `color` (default muted; the node's icon_color overrides inline). */
+.graph-node-custom-icon {
+    color: var(--lux-ink-mute, var(--text-muted));
+    opacity: 0.9;
+}
+
+.graph-node.running .graph-node-custom-icon {
+    color: var(--ch-signal, var(--primary-color));
+    opacity: 1;
+}
+
 /* ── Running indicator (animated gradient border + signal-flow glow) ── */
 
 .graph-node.running .graph-node-body {
@@ -588,6 +600,21 @@ html:has(#tab-graph.active) {
     filter: drop-shadow(0 0 6px var(--ch-signal, var(--primary-color)));
 }
 
+/* Whole-node drop targets: a source can be dropped on any compatible node to
+   wire one of its slots — including empty slots that have no input port yet. */
+.graph-svg.connecting .graph-node-compatible .graph-node-body {
+    stroke: var(--ch-signal, var(--primary-color));
+    stroke-dasharray: 4 3;
+    stroke-width: 1.5;
+}
+
+.graph-node-drop-target .graph-node-body {
+    stroke: var(--ch-signal, var(--primary-color)) !important;
+    stroke-width: 2.5 !important;
+    stroke-dasharray: none !important;
+    filter: drop-shadow(0 0 8px color-mix(in srgb, var(--ch-signal, var(--primary-color)) 55%, transparent));
+}
+
 /* ── Edges ── */
 
 .graph-edge {
@@ -630,6 +657,25 @@ html:has(#tab-graph.active) {
     opacity: 0.4;
 }
 
+/* Edge field labels — hidden until zoomed in enough to read them. */
+.graph-edge-label {
+    font-size: 9px;
+    font-weight: 600;
+    font-family: var(--font-mono, monospace);
+    fill: var(--text-secondary);
+    paint-order: stroke;
+    stroke: var(--lux-bg-1, var(--card-bg));
+    stroke-width: 3px;
+    stroke-linejoin: round;
+    pointer-events: none;
+    opacity: 0;
+    transition: opacity 0.15s ease;
+}
+
+.graph-edges.show-labels .graph-edge-label {
+    opacity: 0.85;
+}
+
 /* Edge type colors */
 .graph-edge-picture    { stroke: #42A5F5; color: #42A5F5; }
 .graph-edge-colorstrip { stroke: #66BB6A; color: #66BB6A; }
@@ -788,6 +834,17 @@ html:has(#tab-graph.active) {
     stroke-dasharray: 4 3;
 }
 
+/* ── Health overlay: configuration issues (broken refs / cycles) ── */
+.graph-node.has-issue .graph-node-body {
+    stroke: var(--danger-color);
+    stroke-width: 2;
+    stroke-dasharray: 5 3;
+}
+
+.graph-node-issue {
+    color: var(--danger-color);
+}
+
 /* ── Search highlight ── */
 
 .graph-node.search-match .graph-node-body {
@@ -1001,6 +1058,33 @@ html:has(#tab-graph.active) {
     display: inline-block;
 }
 
+/* Issues toolbar button + count badge */
+.graph-issues-btn {
+    position: relative;
+    color: var(--danger-color);
+}
+
+.graph-issues-count {
+    position: absolute;
+    top: 0;
+    right: 0;
+    transform: translate(35%, -35%);
+    background: var(--danger-color);
+    color: #fff;
+    border-radius: 8px;
+    font-size: 0.6rem;
+    font-weight: 700;
+    min-width: 14px;
+    height: 14px;
+    line-height: 14px;
+    text-align: center;
+    padding: 0 3px;
+}
+
+.graph-issues-count:empty {
+    display: none;
+}
+
 .graph-filter-types-popover {
     display: none;
     flex-direction: column;

server/src/ledgrab/static/js/app.ts

@@ -207,7 +207,7 @@ import {
 import {
     loadGraphEditor,
     toggleGraphLegend, toggleGraphMinimap, toggleGraphFilter, toggleGraphFilterTypes, toggleGraphHelp, graphUndo, graphRedo,
-    graphFitAll, graphZoomIn, graphZoomOut, graphRelayout,
+    graphFitAll, graphZoomIn, graphZoomOut, graphRelayout, graphShowIssues, graphExportTopology,
     graphToggleFullscreen, graphAddEntity, toggleToolbarOverflow, closeToolbarOverflow,
 } from './features/graph-editor.ts';
 
@@ -625,6 +625,8 @@ Object.assign(window, {
     graphZoomIn,
     graphZoomOut,
     graphRelayout,
+    graphShowIssues,
+    graphExportTopology,
     graphToggleFullscreen,
     graphAddEntity,
     toggleToolbarOverflow,

server/src/ledgrab/static/js/core/graph-connections.ts

@@ -3,12 +3,65 @@
  * Supports creating, changing, and detaching connections via the graph editor.
  */
 
-import { apiPut } from './api-client.ts';
+import { apiPut, apiPost, apiGet } from './api-client.ts';
 import {
     streamsCache, colorStripSourcesCache, valueSourcesCache,
     audioSourcesCache, outputTargetsCache, automationsCacheObj,
 } from './state.ts';
 
+/** Result of the backend pre-write connection validator. */
+export interface ConnectionValidation {
+    ok: boolean;
+    error?: string | null;
+}
+
+/**
+ * Ask the backend whether a proposed wiring edit is valid (target/source exist,
+ * source is the right kind, and it would not create a dependency cycle).
+ *
+ * Fails *open*: if the validation endpoint is unavailable we return ``ok`` so
+ * wiring still works against older servers — the per-entity PUT remains the
+ * source of truth, this is just an early, friendlier guard.
+ */
+export async function validateConnection(
+    targetKind: string, targetId: string, field: string, sourceId: string,
+): Promise<ConnectionValidation> {
+    try {
+        return await apiPost<ConnectionValidation>('/graph/validate-connection', {
+            target_kind: targetKind,
+            target_id: targetId,
+            field,
+            source_id: sourceId,
+        });
+    } catch {
+        return { ok: true };
+    }
+}
+
+/** An entity that references another entity (one row of the dependents query). */
+export interface GraphDependent {
+    id: string;
+    kind: string;
+    name: string;
+    field: string;
+}
+
+/**
+ * List every entity that references ``(kind, id)``. Used to warn before a
+ * delete would dangle other entities' references. Fails *safe* (empty list)
+ * if the endpoint is unavailable.
+ */
+export async function getDependents(kind: string, id: string): Promise<GraphDependent[]> {
+    try {
+        const res = await apiGet<{ dependents: GraphDependent[] }>(
+            `/graph/dependents/${encodeURIComponent(kind)}/${encodeURIComponent(id)}`,
+        );
+        return res.dependents || [];
+    } catch {
+        return [];
+    }
+}
+
 /* ── Types ────────────────────────────────────────────────────── */
 
 interface ConnectionEntry {
@@ -19,6 +72,13 @@ interface ConnectionEntry {
     endpoint?: string;
     cache?: { invalidate(): void };
     nested?: boolean;
+    /**
+     * A single-level value-source binding (e.g. `brightness.source_id`). These
+     * are structurally nested but ARE drag-editable: the write goes through the
+     * entity's `BindableFloat.apply_update`, which merges `{source_id}` while
+     * preserving the static value. (List/double-nested fields stay read-only.)
+     */
+    bindable?: boolean;
 }
 
 interface CompatibleInput {
@@ -61,26 +121,26 @@ const CONNECTION_MAP: ConnectionEntry[] = [
     // Output targets
     { targetKind: 'output_target', field: 'device_id', sourceKind: 'device', edgeType: 'device', endpoint: '/output-targets/{id}', cache: outputTargetsCache },
     { targetKind: 'output_target', field: 'color_strip_source_id', sourceKind: 'color_strip_source', edgeType: 'colorstrip', endpoint: '/output-targets/{id}', cache: outputTargetsCache },
-    { targetKind: 'output_target', field: 'brightness.source_id', sourceKind: 'value_source', edgeType: 'value', endpoint: '/output-targets/{id}', cache: outputTargetsCache, nested: true },
+    { targetKind: 'output_target', field: 'brightness.source_id', sourceKind: 'value_source', edgeType: 'value', endpoint: '/output-targets/{id}', cache: outputTargetsCache, nested: true, bindable: true },
     { targetKind: 'output_target', field: 'picture_source_id', sourceKind: 'picture_source', edgeType: 'picture', endpoint: '/output-targets/{id}', cache: outputTargetsCache },
 
     // Automations
     { targetKind: 'automation', field: 'scene_preset_id', sourceKind: 'scene_preset', edgeType: 'scene', endpoint: '/automations/{id}', cache: automationsCacheObj },
     { targetKind: 'automation', field: 'deactivation_scene_preset_id', sourceKind: 'scene_preset', edgeType: 'scene', endpoint: '/automations/{id}', cache: automationsCacheObj },
 
-    // ── BindableFloat value source edges (CSS properties) ──
-    { targetKind: 'color_strip_source', field: 'smoothing.source_id', sourceKind: 'value_source', edgeType: 'value', nested: true },
-    { targetKind: 'color_strip_source', field: 'sensitivity.source_id', sourceKind: 'value_source', edgeType: 'value', nested: true },
-    { targetKind: 'color_strip_source', field: 'intensity.source_id', sourceKind: 'value_source', edgeType: 'value', nested: true },
-    { targetKind: 'color_strip_source', field: 'scale.source_id', sourceKind: 'value_source', edgeType: 'value', nested: true },
-    { targetKind: 'color_strip_source', field: 'speed.source_id', sourceKind: 'value_source', edgeType: 'value', nested: true },
-    { targetKind: 'color_strip_source', field: 'wind_strength.source_id', sourceKind: 'value_source', edgeType: 'value', nested: true },
-    { targetKind: 'color_strip_source', field: 'temperature_influence.source_id', sourceKind: 'value_source', edgeType: 'value', nested: true },
-    { targetKind: 'color_strip_source', field: 'sound_volume.source_id', sourceKind: 'value_source', edgeType: 'value', nested: true },
-    { targetKind: 'color_strip_source', field: 'timeout.source_id', sourceKind: 'value_source', edgeType: 'value', nested: true },
-    { targetKind: 'color_strip_source', field: 'brightness.source_id', sourceKind: 'value_source', edgeType: 'value', nested: true },
+    // ── BindableFloat value source edges (CSS properties) — drag-editable ──
+    { targetKind: 'color_strip_source', field: 'smoothing.source_id', sourceKind: 'value_source', edgeType: 'value', endpoint: '/color-strip-sources/{id}', cache: colorStripSourcesCache, nested: true, bindable: true },
+    { targetKind: 'color_strip_source', field: 'sensitivity.source_id', sourceKind: 'value_source', edgeType: 'value', endpoint: '/color-strip-sources/{id}', cache: colorStripSourcesCache, nested: true, bindable: true },
+    { targetKind: 'color_strip_source', field: 'intensity.source_id', sourceKind: 'value_source', edgeType: 'value', endpoint: '/color-strip-sources/{id}', cache: colorStripSourcesCache, nested: true, bindable: true },
+    { targetKind: 'color_strip_source', field: 'scale.source_id', sourceKind: 'value_source', edgeType: 'value', endpoint: '/color-strip-sources/{id}', cache: colorStripSourcesCache, nested: true, bindable: true },
+    { targetKind: 'color_strip_source', field: 'speed.source_id', sourceKind: 'value_source', edgeType: 'value', endpoint: '/color-strip-sources/{id}', cache: colorStripSourcesCache, nested: true, bindable: true },
+    { targetKind: 'color_strip_source', field: 'wind_strength.source_id', sourceKind: 'value_source', edgeType: 'value', endpoint: '/color-strip-sources/{id}', cache: colorStripSourcesCache, nested: true, bindable: true },
+    { targetKind: 'color_strip_source', field: 'temperature_influence.source_id', sourceKind: 'value_source', edgeType: 'value', endpoint: '/color-strip-sources/{id}', cache: colorStripSourcesCache, nested: true, bindable: true },
+    { targetKind: 'color_strip_source', field: 'sound_volume.source_id', sourceKind: 'value_source', edgeType: 'value', endpoint: '/color-strip-sources/{id}', cache: colorStripSourcesCache, nested: true, bindable: true },
+    { targetKind: 'color_strip_source', field: 'timeout.source_id', sourceKind: 'value_source', edgeType: 'value', endpoint: '/color-strip-sources/{id}', cache: colorStripSourcesCache, nested: true, bindable: true },
+    { targetKind: 'color_strip_source', field: 'brightness.source_id', sourceKind: 'value_source', edgeType: 'value', endpoint: '/color-strip-sources/{id}', cache: colorStripSourcesCache, nested: true, bindable: true },
     // HA light target transition binding
-    { targetKind: 'output_target', field: 'transition.source_id', sourceKind: 'value_source', edgeType: 'value', nested: true },
+    { targetKind: 'output_target', field: 'transition.source_id', sourceKind: 'value_source', edgeType: 'value', endpoint: '/output-targets/{id}', cache: outputTargetsCache, nested: true, bindable: true },
     // ── BindableColor value source edges (CSS color properties) ──
     { targetKind: 'color_strip_source', field: 'color.source_id', sourceKind: 'value_source', edgeType: 'value', nested: true },
     { targetKind: 'color_strip_source', field: 'color_peak.source_id', sourceKind: 'value_source', edgeType: 'value', nested: true },
@@ -97,12 +157,23 @@ const CONNECTION_MAP: ConnectionEntry[] = [
     { targetKind: 'scene_preset', field: 'target_id', sourceKind: 'output_target', edgeType: 'scene', nested: true },
 ];
 
+/** Editable via the graph: top-level reference fields, plus single-level
+ *  bindable value-source slots (list/double-nested fields stay read-only). */
+function _isEditable(c: ConnectionEntry): boolean {
+    return !c.nested || !!c.bindable;
+}
+
+/** True when a field is a bindable slot (its parent is a `Bindable*`). */
+export function isBindableField(targetKind: string, field: string): boolean {
+    return !!CONNECTION_MAP.find(c => c.targetKind === targetKind && c.field === field)?.bindable;
+}
+
 /**
  * Check if an edge (by field name) is editable via drag-connect.
  */
 export function isEditableEdge(field: string): boolean {
     const entry = CONNECTION_MAP.find(c => c.field === field);
-    return entry ? !entry.nested : false;
+    return entry ? _isEditable(entry) : false;
 }
 
 /**
@@ -111,7 +182,7 @@ export function isEditableEdge(field: string): boolean {
  */
 export function findConnection(targetKind: string, sourceKind: string, edgeType?: string): ConnectionEntry[] {
     return CONNECTION_MAP.filter(c =>
-        !c.nested &&
+        _isEditable(c) &&
         c.targetKind === targetKind &&
         c.sourceKind === sourceKind &&
         (!edgeType || c.edgeType === edgeType)
@@ -124,7 +195,7 @@ export function findConnection(targetKind: string, sourceKind: string, edgeType?
  */
 export function getCompatibleInputs(sourceKind: string): CompatibleInput[] {
     return CONNECTION_MAP
-        .filter(c => !c.nested && c.sourceKind === sourceKind)
+        .filter(c => _isEditable(c) && c.sourceKind === sourceKind)
         .map(c => ({ targetKind: c.targetKind, field: c.field, edgeType: c.edgeType }));
 }
 
@@ -132,7 +203,7 @@ export function getCompatibleInputs(sourceKind: string): CompatibleInput[] {
  * Find the connection entry for a specific edge (by target kind and field).
  */
 export function getConnectionByField(targetKind: string, field: string): ConnectionEntry | undefined {
-    return CONNECTION_MAP.find(c => c.targetKind === targetKind && c.field === field && !c.nested);
+    return CONNECTION_MAP.find(c => c.targetKind === targetKind && c.field === field && _isEditable(c));
 }
 
 /**
@@ -144,11 +215,16 @@ export function getConnectionByField(targetKind: string, field: string): Connect
  * @returns {Promise<boolean>} success
  */
 export async function updateConnection(targetId: string, targetKind: string, field: string, newSourceId: string | null): Promise<boolean> {
-    const entry = CONNECTION_MAP.find(c => c.targetKind === targetKind && c.field === field && !c.nested);
-    if (!entry) return false;
+    const entry = CONNECTION_MAP.find(c => c.targetKind === targetKind && c.field === field && _isEditable(c));
+    if (!entry || !entry.endpoint) return false;
 
-    const url = entry.endpoint!.replace('{id}', targetId);
-    const body = { [field]: newSourceId };
+    const url = entry.endpoint.replace('{id}', targetId);
+    // For a bindable slot (`<parent>.source_id`) PUT `{ <parent>: { source_id } }`
+    // so the backend's `Bindable*.apply_update` merges and preserves the static
+    // value/colour. Top-level fields keep the flat `{ field: id }` shape.
+    const body: Record<string, unknown> = entry.bindable
+        ? { [field.split('.')[0]]: { source_id: newSourceId || '' } }
+        : { [field]: newSourceId };
 
     try {
         await apiPut(url, body);

server/src/ledgrab/static/js/core/graph-edges.ts

@@ -52,6 +52,43 @@ export function renderEdges(group: SVGGElement, edges: GraphEdge[]): void {
         const path = _renderEdge(edge);
         group.appendChild(path);
     }
+
+    // Field labels rendered last so they sit above the paths. Hidden by
+    // default — revealed when zoomed in (`.show-labels`) or on highlight.
+    for (const edge of edges) {
+        const label = _renderEdgeLabel(edge);
+        if (label) group.appendChild(label);
+    }
+}
+
+/** Human-readable label for a reference field, e.g. `capture_template_id` → `capture template`. */
+function _edgeFieldLabel(field: string): string {
+    return field.replace(/_id$/, '').replace(/\./g, ' ').replace(/_/g, ' ').trim();
+}
+
+/** Midpoint of the port-aware cubic bezier (its control points are horizontal
+ *  offsets only, so the t=0.5 point is exactly the endpoint midpoint). */
+function _edgeMidpoint(fromNode: GraphNodeRect, toNode: GraphNodeRect, fromPortY?: number, toPortY?: number): { x: number; y: number } {
+    const x1 = fromNode.x + fromNode.width;
+    const y1 = fromNode.y + (fromPortY ?? fromNode.height / 2);
+    const x2 = toNode.x;
+    const y2 = toNode.y + (toPortY ?? toNode.height / 2);
+    return { x: (x1 + x2) / 2, y: (y1 + y2) / 2 };
+}
+
+function _renderEdgeLabel(edge: GraphEdge): SVGElement | null {
+    if (!edge.field || !edge.fromNode || !edge.toNode) return null;
+    const mid = _edgeMidpoint(edge.fromNode, edge.toNode, edge.fromPortY, edge.toPortY);
+    const text = svgEl('text', {
+        class: `graph-edge-label graph-edge-label-${edge.type}`,
+        x: mid.x, y: mid.y - 4,
+        'text-anchor': 'middle',
+        'data-from': edge.from,
+        'data-to': edge.to,
+        'data-field': edge.field,
+    });
+    text.textContent = _edgeFieldLabel(edge.field);
+    return text;
 }
 
 function _createArrowMarker(type: string): SVGElement {
@@ -263,6 +300,14 @@ export function updateEdgesForNode(group: SVGGElement, nodeId: string, nodeMap:
                 pathEl.setAttribute('d', d);
             }
         });
+        // Keep the field label pinned to the edge midpoint while dragging.
+        const mid = _edgeMidpoint(fromNode, toNode, edge.fromPortY, edge.toPortY);
+        group.querySelectorAll(`.graph-edge-label[data-from="${edge.from}"][data-to="${edge.to}"]`).forEach(lbl => {
+            if ((lbl.getAttribute('data-field') || '') === (edge.field || '')) {
+                lbl.setAttribute('x', String(mid.x));
+                lbl.setAttribute('y', String(mid.y - 4));
+            }
+        });
     }
 }
 

server/src/ledgrab/static/js/core/graph-layout.ts

@@ -13,6 +13,8 @@ interface LayoutNode {
     name: string;
     subtype: string;
     tags: string[];
+    icon?: string;
+    iconColor?: string;
     running?: boolean;
     x?: number;
     y?: number;
@@ -33,6 +35,17 @@ interface LayoutResult {
     nodes: Map<string, LayoutNode>;
     edges: (LayoutEdge & { points: { x: number; y: number }[] | null; fromNode: LayoutNode; toNode: LayoutNode })[];
     bounds: { x: number; y: number; width: number; height: number };
+    brokenRefs: BrokenRef[];
+}
+
+/** A reference field that points at an entity which no longer exists. */
+export interface BrokenRef {
+    /** The missing (referenced) entity id. */
+    ref: string;
+    /** The id of the entity that still holds the dangling reference. */
+    by: string;
+    /** The reference field name on the referrer. */
+    field: string;
 }
 
 interface PortSet {
@@ -81,7 +94,7 @@ const ELK_OPTIONS = {
  */
 export async function computeLayout(entities: EntitiesInput): Promise<LayoutResult> {
     const elk = new ELK();
-    const { nodes: nodeList, edges: edgeList } = buildGraph(entities);
+    const { nodes: nodeList, edges: edgeList, brokenRefs } = buildGraph(entities);
 
     const elkGraph = {
         id: 'root',
@@ -151,7 +164,7 @@ export async function computeLayout(entities: EntitiesInput): Promise<LayoutResu
         ? { x: minX, y: minY, width: maxX - minX, height: maxY - minY }
         : { x: 0, y: 0, width: 400, height: 300 };
 
-    return { nodes: nodeMap, edges, bounds };
+    return { nodes: nodeMap, edges, bounds, brokenRefs };
 }
 
 /* ── Entity color mapping ── */
@@ -207,22 +220,36 @@ function edgeType(fromKind: string, toKind: string, field: string): string {
 
 /* ── Graph builder ── */
 
-function buildGraph(e: EntitiesInput): { nodes: LayoutNode[]; edges: LayoutEdge[] } {
+function buildGraph(e: EntitiesInput): { nodes: LayoutNode[]; edges: LayoutEdge[]; brokenRefs: BrokenRef[] } {
     const nodes: LayoutNode[] = [];
     const edges: LayoutEdge[] = [];
+    const brokenRefs: BrokenRef[] = [];
     const nodeIds = new Set<string>();
+    // Index nodes by id so edge-building is O(1) instead of O(N) per edge.
+    const nodeByIdLocal = new Map<string, LayoutNode>();
 
     function addNode(id: string, kind: string, name: string, subtype: string, extra: Record<string, any> = {}): void {
         if (!id || nodeIds.has(id)) return;
         nodeIds.add(id);
-        nodes.push({ id, kind, name: name || id, subtype: subtype || '', tags: extra.tags || [], ...extra });
+        const node = { id, kind, name: name || id, subtype: subtype || '', tags: extra.tags || [], ...extra };
+        nodes.push(node);
+        nodeByIdLocal.set(id, node);
     }
 
     function addEdge(from: string, to: string, field: string, label: string = ''): void {
-        if (!from || !to || !nodeIds.has(from) || !nodeIds.has(to)) return;
+        if (!from || !to) return;
+        // The referrer (`to`) is always a current entity in these loops; if the
+        // referenced entity (`from`) is missing, the reference is dangling —
+        // record it so the editor can surface a "broken reference" warning
+        // instead of silently dropping the edge (the old behaviour).
+        if (!nodeIds.has(from)) {
+            if (nodeIds.has(to)) brokenRefs.push({ ref: from, by: to, field });
+            return;
+        }
+        if (!nodeIds.has(to)) return;
         const type = edgeType(
-            nodes.find(n => n.id === from)?.kind ?? '',
-            nodes.find(n => n.id === to)?.kind ?? '',
+            nodeByIdLocal.get(from)?.kind ?? '',
+            nodeByIdLocal.get(to)?.kind ?? '',
             field
         );
         // Edges with dotted fields are nested (composite layers, zones, etc.) — not drag-editable
@@ -230,74 +257,76 @@ function buildGraph(e: EntitiesInput): { nodes: LayoutNode[]; edges: LayoutEdge[
         edges.push({ from, to, field, label, type, editable });
     }
 
+    // Every entity may carry a custom `icon` (+ `icon_color`); pass them through
+    // so node rendering can honour them (parity with custom node colours).
     // 1. Devices
     for (const d of e.devices || []) {
-        addNode(d.id, 'device', d.name, d.device_type, { tags: d.tags });
+        addNode(d.id, 'device', d.name, d.device_type, { tags: d.tags, icon: d.icon, iconColor: d.icon_color });
     }
 
     // 2. Capture templates
     for (const t of e.captureTemplates || []) {
-        addNode(t.id, 'capture_template', t.name, t.engine_type, { tags: t.tags });
+        addNode(t.id, 'capture_template', t.name, t.engine_type, { tags: t.tags, icon: t.icon, iconColor: t.icon_color });
     }
 
     // 3. PP templates
     for (const t of e.ppTemplates || []) {
-        addNode(t.id, 'pp_template', t.name, '', { tags: t.tags });
+        addNode(t.id, 'pp_template', t.name, '', { tags: t.tags, icon: t.icon, iconColor: t.icon_color });
     }
 
     // 4. Audio templates
     for (const t of e.audioTemplates || []) {
-        addNode(t.id, 'audio_template', t.name, t.engine_type, { tags: t.tags });
+        addNode(t.id, 'audio_template', t.name, t.engine_type, { tags: t.tags, icon: t.icon, iconColor: t.icon_color });
     }
 
     // 5. Pattern templates
     for (const t of e.patternTemplates || []) {
-        addNode(t.id, 'pattern_template', t.name, '', { tags: t.tags });
+        addNode(t.id, 'pattern_template', t.name, '', { tags: t.tags, icon: t.icon, iconColor: t.icon_color });
     }
 
     // 6. Sync clocks
     for (const c of e.syncClocks || []) {
-        addNode(c.id, 'sync_clock', c.name, '', { running: c.is_running !== false, tags: c.tags });
+        addNode(c.id, 'sync_clock', c.name, '', { running: c.is_running !== false, tags: c.tags, icon: c.icon, iconColor: c.icon_color });
     }
 
     // 7. Picture sources
     for (const s of e.pictureSources || []) {
-        addNode(s.id, 'picture_source', s.name, s.stream_type, { tags: s.tags });
+        addNode(s.id, 'picture_source', s.name, s.stream_type, { tags: s.tags, icon: s.icon, iconColor: s.icon_color });
     }
 
     // 8. Audio sources
     for (const s of e.audioSources || []) {
-        addNode(s.id, 'audio_source', s.name, s.source_type, { tags: s.tags });
+        addNode(s.id, 'audio_source', s.name, s.source_type, { tags: s.tags, icon: s.icon, iconColor: s.icon_color });
     }
 
     // 9. Value sources
     for (const s of e.valueSources || []) {
-        addNode(s.id, 'value_source', s.name, s.source_type, { tags: s.tags });
+        addNode(s.id, 'value_source', s.name, s.source_type, { tags: s.tags, icon: s.icon, iconColor: s.icon_color });
     }
 
     // 10. Color strip sources
     for (const s of e.colorStripSources || []) {
-        addNode(s.id, 'color_strip_source', s.name, s.source_type, { tags: s.tags });
+        addNode(s.id, 'color_strip_source', s.name, s.source_type, { tags: s.tags, icon: s.icon, iconColor: s.icon_color });
     }
 
     // 11. Output targets
     for (const t of e.outputTargets || []) {
-        addNode(t.id, 'output_target', t.name, t.target_type, { running: t.running || false, tags: t.tags });
+        addNode(t.id, 'output_target', t.name, t.target_type, { running: t.running || false, tags: t.tags, icon: t.icon, iconColor: t.icon_color });
     }
 
     // 12. Scene presets
     for (const s of e.scenePresets || []) {
-        addNode(s.id, 'scene_preset', s.name, '', { tags: s.tags });
+        addNode(s.id, 'scene_preset', s.name, '', { tags: s.tags, icon: s.icon, iconColor: s.icon_color });
     }
 
     // 13. Automations
     for (const a of e.automations || []) {
-        addNode(a.id, 'automation', a.name, '', { running: a.enabled || false, tags: a.tags });
+        addNode(a.id, 'automation', a.name, '', { running: a.enabled || false, tags: a.tags, icon: a.icon, iconColor: a.icon_color });
     }
 
     // 14. Color strip processing templates (CSPT)
     for (const t of e.csptTemplates || []) {
-        addNode(t.id, 'cspt', t.name, '', { tags: t.tags });
+        addNode(t.id, 'cspt', t.name, '', { tags: t.tags, icon: t.icon, iconColor: t.icon_color });
     }
 
     // ── Edges ──
@@ -414,7 +443,7 @@ function buildGraph(e: EntitiesInput): { nodes: LayoutNode[]; edges: LayoutEdge[
         if (d.default_css_processing_template_id) addEdge(d.default_css_processing_template_id, d.id, 'default_css_processing_template_id');
     }
 
-    return { nodes, edges };
+    return { nodes, edges, brokenRefs };
 }
 
 /* ── Port computation ── */

server/src/ledgrab/static/js/core/graph-nodes.ts

@@ -6,6 +6,7 @@ import { ENTITY_COLORS, NODE_WIDTH, NODE_HEIGHT, computePorts } from './graph-la
 import { EDGE_COLORS } from './graph-edges.ts';
 import { createColorPicker, registerColorPicker, closeAllColorPickers } from './color-picker.ts';
 import { getCardColor, setCardColor } from './card-colors.ts';
+import { renderDeviceIconSvg } from './device-icons.ts';
 import * as P from './icon-paths.ts';
 
 const SVG_NS = 'http://www.w3.org/2000/svg';
@@ -22,6 +23,8 @@ interface GraphNode {
     kind: string;
     name: string;
     subtype?: string;
+    icon?: string;
+    iconColor?: string;
     x: number;
     y: number;
     width: number;
@@ -360,15 +363,29 @@ function renderNode(node: GraphNode, callbacks: NodeCallbacks): SVGElement {
         }
     }
 
-    // Entity icon (right side)
-    const iconPaths = (SUBTYPE_ICONS[kind]?.[subtype]) || KIND_ICONS[kind];
-    if (iconPaths) {
+    // Entity icon (right side). A custom per-entity icon wins over the
+    // kind/subtype default (parity with custom node colours); unknown icon ids
+    // yield '' so we fall back gracefully.
+    const customIconSvg = node.icon ? renderDeviceIconSvg(node.icon, { size: 16 }) : '';
+    if (customIconSvg) {
         const iconG = svgEl('g', {
-            class: 'graph-node-icon',
-            transform: `translate(${width - 28}, ${height / 2 - 8}) scale(0.667)`,
+            class: 'graph-node-custom-icon',
+            transform: `translate(${width - 28}, ${height / 2 - 8})`,
         });
-        iconG.innerHTML = iconPaths;
+        iconG.innerHTML = customIconSvg;
+        // The rendered SVG strokes with currentColor — tint via `color`.
+        if (node.iconColor) (iconG as unknown as SVGGElement).style.color = node.iconColor;
         g.appendChild(iconG);
+    } else {
+        const iconPaths = (SUBTYPE_ICONS[kind]?.[subtype]) || KIND_ICONS[kind];
+        if (iconPaths) {
+            const iconG = svgEl('g', {
+                class: 'graph-node-icon',
+                transform: `translate(${width - 28}, ${height / 2 - 8}) scale(0.667)`,
+            });
+            iconG.innerHTML = iconPaths;
+            g.appendChild(iconG);
+        }
     }
 
     // Running dot
@@ -627,6 +644,39 @@ export function markOrphans(group: SVGGElement, nodeMap: Map<string, GraphNode>,
     }
 }
 
+/**
+ * Mark nodes that have configuration issues (e.g. broken references, cycles).
+ * Adds a warning badge anchored to the node's top-left corner with a tooltip
+ * describing every problem. Call after `renderNodes`.
+ */
+export function markIssues(group: SVGGElement, issues: Map<string, string[]>): void {
+    // Clear previous markers so repeated calls don't stack badges.
+    group.querySelectorAll('.graph-node-issue').forEach(e => e.remove());
+    group.querySelectorAll('.graph-node.has-issue').forEach(n => n.classList.remove('has-issue'));
+
+    for (const [id, msgs] of issues) {
+        if (!msgs.length) continue;
+        const el = group.querySelector(`.graph-node[data-id="${id}"]`);
+        if (!el) continue;
+        el.classList.add('has-issue');
+
+        const badge = svgEl('g', { class: 'graph-node-issue' });
+        const icon = svgEl('g', { transform: 'translate(2, -9) scale(0.6)' });
+        icon.innerHTML = P.triangleAlert;
+        icon.setAttribute('fill', 'none');
+        icon.setAttribute('stroke', 'currentColor');
+        icon.setAttribute('stroke-width', '2.5');
+        icon.setAttribute('stroke-linecap', 'round');
+        icon.setAttribute('stroke-linejoin', 'round');
+        badge.appendChild(icon);
+
+        const tip = svgEl('title');
+        tip.textContent = msgs.join('\n');
+        badge.appendChild(tip);
+        el.appendChild(badge);
+    }
+}
+
 /**
  * Update selection state on nodes.
  */

server/src/ledgrab/static/js/features/device-discovery.ts

@@ -5,7 +5,7 @@
 import {
     _discoveryScanRunning, set_discoveryScanRunning,
     _discoveryCache, set_discoveryCache,
-    csptCache,
+    csptCache, mqttSourcesCache,
 } from '../core/state.ts';
 import { API_BASE, isSerialDevice, isMockDevice, isMqttDevice, isWsDevice, isOpenrgbDevice, isDmxDevice, isDdpDevice, isOpcDevice, isEspnowDevice, isHueDevice, isYeelightDevice, isWizDevice, isLifxDevice, isGoveeDevice, isNanoleafDevice, isBleDevice, isUsbhidDevice, isSpiDevice, isChromaDevice, isGameSenseDevice, isGroupDevice, escapeHtml } from '../core/api.ts';
 import { apiGet, apiPost } from '../core/api-client.ts';
@@ -18,6 +18,7 @@ import { runPairingFlow, PairingCancelled } from './pairing-flow.ts';
 import { getDeviceTypeIcon, ICON_RADIO, ICON_GLOBE, ICON_CPU, ICON_KEYBOARD, ICON_MOUSE, ICON_HEADPHONES, ICON_PLUG, ICON_TARGET_ICON, ICON_ACTIVITY, ICON_TEMPLATE, ICON_CHEVRON_UP, ICON_CHEVRON_DOWN, ICON_PLUS, ICON_TRASH, ICON_GIT_MERGE, ICON_COPY, ICON_BLUETOOTH, ICON_LIGHTBULB, ICON_SPARKLES, ICON_PALETTE } from '../core/icons.ts';
 import { EntitySelect, EntityPalette } from '../core/entity-palette.ts';
 import { IconSelect, showTypePicker } from '../core/icon-select.ts';
+import type { MQTTSource } from '../types.ts';
 
 class AddDeviceModal extends Modal {
     constructor() { super('add-device-modal'); }
@@ -44,6 +45,7 @@ class AddDeviceModal extends Modal {
             opcChannel: (document.getElementById('device-opc-channel') as HTMLInputElement)?.value || '0',
             bleFamily: (document.getElementById('device-ble-family') as HTMLSelectElement)?.value || '',
             bleGoveeKey: (document.getElementById('device-ble-govee-key') as HTMLInputElement)?.value || '',
+            mqttSource: (document.getElementById('device-mqtt-source') as HTMLSelectElement)?.value || '',
             yeelightMinInterval: (document.getElementById('device-yeelight-min-interval') as HTMLInputElement)?.value || '500',
             wizMinInterval: (document.getElementById('device-wiz-min-interval') as HTMLInputElement)?.value || '50',
             lifxMinInterval: (document.getElementById('device-lifx-min-interval') as HTMLInputElement)?.value || '50',
@@ -72,6 +74,7 @@ function _buildDeviceTypeItems() {
 
 let _deviceTypeIconSelect: any = null;
 let _csptEntitySelect: any = null;
+let _mqttSourceEntitySelect: any = null;
 
 function _ensureDeviceTypeIconSelect() {
     const sel = document.getElementById('device-type');
@@ -104,6 +107,36 @@ function _ensureCsptEntitySelect() {
     }
 }
 
+// MQTT broker picker for device_type=mqtt. Empty value = first available broker.
+function _ensureMqttSourceSelect() {
+    const sel = document.getElementById('device-mqtt-source') as HTMLSelectElement | null;
+    if (!sel) return;
+    const sources: MQTTSource[] = mqttSourcesCache.data || [];
+    const current = sel.value;
+    sel.innerHTML = `<option value="">${t('device.mqtt_source.none')}</option>` +
+        sources.map((s: MQTTSource) => `<option value="${escapeHtml(s.id)}">${escapeHtml(s.name)}</option>`).join('');
+    sel.value = current;
+    if (_mqttSourceEntitySelect) _mqttSourceEntitySelect.destroy();
+    _mqttSourceEntitySelect = new EntitySelect({
+        target: sel,
+        getItems: () => (mqttSourcesCache.data || []).map((s: MQTTSource) => ({
+            value: s.id,
+            label: s.name,
+            icon: ICON_PALETTE,
+            desc: `${s.broker_host}:${s.broker_port}`,
+        })),
+        placeholder: t('palette.search'),
+        allowNone: true,
+        noneLabel: t('device.mqtt_source.none'),
+    } as any);
+}
+
+function _showMqttSourceField(show: boolean) {
+    const group = document.getElementById('device-mqtt-source-group') as HTMLElement | null;
+    if (group) group.style.display = show ? '' : 'none';
+    if (show) mqttSourcesCache.fetch().then(() => _ensureMqttSourceSelect());
+}
+
 /* ── Icon-grid DMX protocol selector ─────────────────────────── */
 
 function _buildDmxProtocolItems() {
@@ -297,6 +330,7 @@ export function onDeviceTypeChanged() {
     _showGameSenseFields(false);
     _showGroupFields(false);
     _showOpcFields(false);
+    _showMqttSourceField(false);
 
     if (isMqttDevice(deviceType)) {
         // MQTT: show URL (topic), LED count; hide serial/baud/led-type/latency/discovery
@@ -314,6 +348,7 @@ export function onDeviceTypeChanged() {
         if (urlLabel) urlLabel.textContent = t('device.mqtt_topic');
         if (urlHint) urlHint.textContent = t('device.mqtt_topic.hint');
         urlInput.placeholder = t('device.mqtt_topic.placeholder') || 'mqtt://ledgrab/device/living-room';
+        _showMqttSourceField(true);
     } else if (isMockDevice(deviceType)) {
         urlGroup.style.display = 'none';
         urlInput.removeAttribute('required');
@@ -920,6 +955,14 @@ export function showAddDevice(presetType: any = null, cloneData: any = null) {
             if (goveeKeyEl && cloneData.ble_govee_key) goveeKeyEl.value = cloneData.ble_govee_key;
             _updateBleGoveeKeyVisibility();
         }
+        // Prefill MQTT broker (after the source cache loads)
+        if (isMqttDevice(presetType) && cloneData.mqtt_source_id) {
+            mqttSourcesCache.fetch().then(() => {
+                const msEl = document.getElementById('device-mqtt-source') as HTMLSelectElement;
+                if (msEl) msEl.value = cloneData.mqtt_source_id;
+                _ensureMqttSourceSelect();
+            });
+        }
         // Prefill DMX fields
         if (isDmxDevice(presetType)) {
             const dmxProto = document.getElementById('device-dmx-protocol') as HTMLSelectElement;
@@ -1217,6 +1260,10 @@ export async function handleAddDevice(event: any) {
             const goveeKey = (document.getElementById('device-ble-govee-key') as HTMLInputElement)?.value?.trim();
             if (goveeKey) body.ble_govee_key = goveeKey;
         }
+        if (isMqttDevice(deviceType)) {
+            const mqttSource = (document.getElementById('device-mqtt-source') as HTMLSelectElement)?.value || '';
+            if (mqttSource) body.mqtt_source_id = mqttSource;
+        }
         if (isSpiDevice(deviceType)) {
             body.spi_speed_hz = parseInt((document.getElementById('device-spi-speed') as HTMLInputElement)?.value || '800000', 10);
             body.spi_led_type = (document.getElementById('device-spi-led-type') as HTMLSelectElement)?.value || 'WS2812B';

server/src/ledgrab/static/js/features/devices.ts

@@ -4,7 +4,7 @@
 
 import {
     _deviceBrightnessCache, updateDeviceBrightness,
-    csptCache,
+    csptCache, mqttSourcesCache,
 } from '../core/state.ts';
 import { API_BASE, getHeaders, escapeHtml, isSerialDevice, isMockDevice, isMqttDevice, isWsDevice, isOpenrgbDevice, isDmxDevice, isDdpDevice, isOpcDevice, isYeelightDevice, isWizDevice, isLifxDevice, isGoveeDevice, isNanoleafDevice, isBleDevice, isGroupDevice } from '../core/api.ts';
 import { apiGet, apiPost, apiPut, apiDelete } from '../core/api-client.ts';
@@ -13,18 +13,19 @@ import { _fetchOpenrgbZones, _getCheckedZones, _splitOpenrgbZone, _getZoneMode,
 import { t } from '../core/i18n.ts';
 import { showToast, showConfirm, desktopFocus } from '../core/ui.ts';
 import { Modal } from '../core/modal.ts';
-import { ICON_SETTINGS, ICON_STOP_PLAIN, ICON_LED, ICON_WEB, ICON_REFRESH, ICON_TEMPLATE } from '../core/icons.ts';
+import { ICON_SETTINGS, ICON_STOP_PLAIN, ICON_LED, ICON_WEB, ICON_REFRESH, ICON_TEMPLATE, ICON_PALETTE } from '../core/icons.ts';
 import { wrapCard } from '../core/card-colors.ts';
 import type { ModCardOpts, LedState, ModMetricOpts, ModChipOpts, ModBtnOpts, ModMenuItemOpts } from '../core/mod-card.ts';
 import { TagInput, renderTagChips } from '../core/tag-input.ts';
 import { EntitySelect } from '../core/entity-palette.ts';
 import { getBaseOrigin } from './settings.ts';
-import type { Device } from '../types.ts';
+import type { Device, MQTTSource } from '../types.ts';
 import { renderDeviceIconSvg } from '../core/device-icons.ts';
 import { ICON_EDIT } from '../core/icons.ts';
 
 let _deviceTagsInput: any = null;
 let _settingsCsptEntitySelect: any = null;
+let _settingsMqttEntitySelect: any = null;
 
 /* The General Settings modal groups its many conditional fields into
    four `.ds-section` panels (Identity / Connection / Hardware / Behavior).
@@ -73,6 +74,29 @@ function _ensureSettingsCsptSelect() {
     }
 }
 
+// MQTT broker picker for the settings modal (device_type=mqtt). Empty = first available.
+function _ensureSettingsMqttSelect(selectedId: string = '') {
+    const sel = document.getElementById('settings-mqtt-source') as HTMLSelectElement | null;
+    if (!sel) return;
+    const sources: MQTTSource[] = mqttSourcesCache.data || [];
+    sel.innerHTML = `<option value="">${t('device.mqtt_source.none')}</option>` +
+        sources.map((s: MQTTSource) => `<option value="${escapeHtml(s.id)}">${escapeHtml(s.name)}</option>`).join('');
+    sel.value = selectedId || '';
+    if (_settingsMqttEntitySelect) _settingsMqttEntitySelect.destroy();
+    _settingsMqttEntitySelect = new EntitySelect({
+        target: sel,
+        getItems: () => (mqttSourcesCache.data || []).map((s: MQTTSource) => ({
+            value: s.id,
+            label: s.name,
+            icon: ICON_PALETTE,
+            desc: `${s.broker_host}:${s.broker_port}`,
+        })),
+        placeholder: t('palette.search'),
+        allowNone: true,
+        noneLabel: t('device.mqtt_source.none'),
+    } as any);
+}
+
 class DeviceSettingsModal extends Modal {
     constructor() { super('device-settings-modal'); }
 
@@ -103,6 +127,7 @@ class DeviceSettingsModal extends Modal {
             goveeMinInterval: (document.getElementById('settings-govee-min-interval') as HTMLInputElement | null)?.value || '50',
             nanoleafMinInterval: (document.getElementById('settings-nanoleaf-min-interval') as HTMLInputElement | null)?.value || '100',
             csptId: (document.getElementById('settings-css-processing-template') as HTMLSelectElement | null)?.value || '',
+            mqttSource: (document.getElementById('settings-mqtt-source') as HTMLSelectElement | null)?.value || '',
         };
     }
 
@@ -439,6 +464,8 @@ export async function showSettings(deviceId: any) {
         const urlLabel = urlGroup.querySelector('label[for="settings-device-url"]') as HTMLElement | null;
         const urlHint = urlGroup.querySelector('.input-hint') as HTMLElement | null;
         const urlInput = document.getElementById('settings-device-url') as HTMLInputElement;
+        const mqttSourceGroup = document.getElementById('settings-mqtt-source-group') as HTMLElement | null;
+        if (mqttSourceGroup) mqttSourceGroup.style.display = 'none';
         if (isMock || isWs || isGroup) {
             urlGroup.style.display = 'none';
             urlInput.removeAttribute('required');
@@ -458,6 +485,7 @@ export async function showSettings(deviceId: any) {
                 if (urlLabel) urlLabel.textContent = t('device.mqtt_topic');
                 if (urlHint) urlHint.textContent = t('device.mqtt_topic.hint');
                 urlInput.placeholder = t('device.mqtt_topic.placeholder') || 'mqtt://ledgrab/device/living-room';
+                if (mqttSourceGroup) mqttSourceGroup.style.display = '';
             } else if (isOpenrgbDevice(device.device_type)) {
                 if (urlLabel) urlLabel.textContent = t('device.openrgb.url');
                 if (urlHint) urlHint.textContent = t('device.openrgb.url.hint');
@@ -805,6 +833,13 @@ export async function showSettings(deviceId: any) {
         const csptSel = document.getElementById('settings-css-processing-template') as HTMLSelectElement | null;
         if (csptSel) csptSel.value = device.default_css_processing_template_id || '';
 
+        // MQTT broker selector (mqtt devices only) — populated before snapshot
+        // so the dirty-check baseline matches the current broker.
+        if (isMqtt) {
+            await mqttSourcesCache.fetch();
+            _ensureSettingsMqttSelect(device.mqtt_source_id || '');
+        }
+
         _updateSettingsSectionVisibility();
         settingsModal.snapshot();
         settingsModal.open();
@@ -819,7 +854,7 @@ export async function showSettings(deviceId: any) {
 }
 
 export function isSettingsDirty() { return settingsModal.isDirty(); }
-export function forceCloseDeviceSettingsModal() { if (_deviceTagsInput) { _deviceTagsInput.destroy(); _deviceTagsInput = null; } if (_settingsCsptEntitySelect) { _settingsCsptEntitySelect.destroy(); _settingsCsptEntitySelect = null; } destroyBleFamilyIconSelect('settings-ble-family'); destroyDdpColorOrderIconSelect('settings-ddp-color-order'); destroyDmxProtocolIconSelect('settings-dmx-protocol'); settingsModal.forceClose(); }
+export function forceCloseDeviceSettingsModal() { if (_deviceTagsInput) { _deviceTagsInput.destroy(); _deviceTagsInput = null; } if (_settingsCsptEntitySelect) { _settingsCsptEntitySelect.destroy(); _settingsCsptEntitySelect = null; } if (_settingsMqttEntitySelect) { _settingsMqttEntitySelect.destroy(); _settingsMqttEntitySelect = null; } destroyBleFamilyIconSelect('settings-ble-family'); destroyDdpColorOrderIconSelect('settings-ddp-color-order'); destroyDmxProtocolIconSelect('settings-dmx-protocol'); settingsModal.forceClose(); }
 export function closeDeviceSettingsModal() { settingsModal.close(); }
 
 export async function saveDeviceSettings() {
@@ -908,6 +943,9 @@ export async function saveDeviceSettings() {
             const goveeKey = (document.getElementById('settings-ble-govee-key') as HTMLInputElement | null)?.value?.trim() || '';
             body.ble_govee_key = goveeKey;
         }
+        if (isMqttDevice(settingsModal.deviceType)) {
+            body.mqtt_source_id = (document.getElementById('settings-mqtt-source') as HTMLSelectElement | null)?.value || '';
+        }
         if (isGroup) {
             const childRows = document.querySelectorAll('#settings-group-children-list .group-child-row') as NodeListOf<HTMLElement>;
             body.group_device_ids = Array.from(childRows).map(r => r.dataset.deviceId || '').filter(v => v !== '');

server/src/ledgrab/static/js/features/graph-editor.ts

@@ -4,7 +4,8 @@
 
 import { GraphCanvas } from '../core/graph-canvas.ts';
 import { computeLayout, computePorts, ENTITY_COLORS, ENTITY_LABELS } from '../core/graph-layout.ts';
-import { renderNodes, patchNodeRunning, highlightNode, markOrphans, updateSelection, getNodeDisplayColor } from '../core/graph-nodes.ts';
+import type { BrokenRef } from '../core/graph-layout.ts';
+import { renderNodes, patchNodeRunning, highlightNode, markOrphans, markIssues, updateSelection, getNodeDisplayColor } from '../core/graph-nodes.ts';
 import { renderEdges, highlightChain, clearEdgeHighlights, updateEdgesForNode, renderFlowDots, updateFlowDotsForNode } from '../core/graph-edges.ts';
 import {
     devicesCache, captureTemplatesCache, ppTemplatesCache,
@@ -14,13 +15,14 @@ import {
     automationsCacheObj, csptCache,
 } from '../core/state.ts';
 import { fetchWithAuth, fetchMetricsHistory } from '../core/api.ts';
+import { apiGet } from '../core/api-client.ts';
 import { showToast, showConfirm, formatUptime, formatCompact } from '../core/ui.ts';
 import { createFpsSparkline } from '../core/chart-utils.ts';
 import { t } from '../core/i18n.ts';
-import { findConnection, getCompatibleInputs, getConnectionByField, updateConnection, detachConnection, isEditableEdge } from '../core/graph-connections.ts';
+import { findConnection, getCompatibleInputs, getConnectionByField, updateConnection, detachConnection, isEditableEdge, validateConnection, getDependents } from '../core/graph-connections.ts';
 import { showTypePicker } from '../core/icon-select.ts';
 import * as P from '../core/icon-paths.ts';
-import { readJson, isObject, isString, isNumber } from '../core/storage.ts';
+import { readJson, writeJson, isObject, isString, isNumber } from '../core/storage.ts';
 import { logError } from '../core/log.ts';
 
 // Local type guard for AnchoredRect — `JSON.parse` returns unknown and the
@@ -122,8 +124,33 @@ let _dragState: DragState | null = null;
 let _justDragged = false;
 let _dragListenersAdded = false;
 
-// Manual position overrides (persisted in memory; cleared on relayout)
-let _manualPositions: Map<string, { x: number; y: number }> = new Map();
+// Manual position overrides — persisted to localStorage so a hand-arranged
+// layout survives page reloads; cleared explicitly on relayout.
+const _POS_KEY = 'graph_node_positions';
+function _isPositionMap(v: unknown): v is Record<string, { x: number; y: number }> {
+    if (!isObject(v)) return false;
+    return Object.values(v).every(p => isObject(p) && isNumber((p as any).x) && isNumber((p as any).y));
+}
+function _loadManualPositions(): Map<string, { x: number; y: number }> {
+    const obj = readJson(_POS_KEY, _isPositionMap);
+    const map = new Map<string, { x: number; y: number }>();
+    if (obj) for (const [id, p] of Object.entries(obj)) map.set(id, { x: p.x, y: p.y });
+    return map;
+}
+function _saveManualPositions(): void {
+    const obj: Record<string, { x: number; y: number }> = {};
+    for (const [id, p] of _manualPositions) obj[id] = p;
+    writeJson(_POS_KEY, obj);
+}
+let _manualPositions: Map<string, { x: number; y: number }> = _loadManualPositions();
+
+// Node IDs that currently have a configuration issue (broken ref / cycle).
+let _issueIds: Set<string> = new Set();
+// Dangling references discovered during the last layout build.
+let _brokenRefs: BrokenRef[] = [];
+// Raw fetched entities by id — lets drop-resolution check which bindable slots
+// a target actually has (subtype-safe), without re-fetching.
+let _entitiesById: Map<string, any> = new Map();
 
 // Rubber-band selection state
 interface RubberBandState { startGraph: { x: number; y: number }; startClient: { x: number; y: number }; active: boolean; }
@@ -333,7 +360,12 @@ export async function loadGraphEditor(): Promise<void> {
 
     try {
         const entities = await _fetchAllEntities();
-        const { nodes, edges, bounds } = await computeLayout(entities);
+        // Index raw entities by id for subtype-safe bindable-slot resolution.
+        _entitiesById = new Map();
+        for (const arr of Object.values(entities)) {
+            if (Array.isArray(arr)) for (const ent of arr) if (ent && ent.id) _entitiesById.set(ent.id, ent);
+        }
+        const { nodes, edges, bounds, brokenRefs } = await computeLayout(entities);
 
         // Apply manual position overrides from previous drag operations
         _applyManualPositions(nodes, edges);
@@ -341,6 +373,7 @@ export async function loadGraphEditor(): Promise<void> {
         computePorts(nodes as any, edges);
         _nodeMap = nodes as any;
         _edges = edges;
+        _brokenRefs = brokenRefs;
         _bounds = _calcBounds(nodes);
         _renderGraph(container);
     } finally {
@@ -661,9 +694,147 @@ export async function graphRelayout(): Promise<void> {
         if (!ok) return;
     }
     _manualPositions.clear();
+    _saveManualPositions();
     await loadGraphEditor();
 }
 
+/* ── Health overlay (broken references + dependency cycles) ── */
+
+/** Humanize a reference field name for display (e.g. `capture_template_id` → `capture template`). */
+function _humanField(field: string): string {
+    return field.replace(/_id$/, '').replace(/\./g, ' ').replace(/_/g, ' ').trim();
+}
+
+/**
+ * Detect every node that participates in a directed dependency cycle.
+ * Iterative DFS with an explicit path stack (no deep recursion).
+ */
+function _detectCycles(nodeMap: Map<string, any>, edges: any[]): Set<string> {
+    const adj = new Map<string, string[]>();
+    for (const e of edges) {
+        if (!adj.has(e.from)) adj.set(e.from, []);
+        adj.get(e.from)!.push(e.to);
+    }
+    const WHITE = 0, GRAY = 1, BLACK = 2;
+    const color = new Map<string, number>();
+    const inCycle = new Set<string>();
+
+    for (const start of nodeMap.keys()) {
+        if (color.get(start)) continue; // already GRAY/BLACK
+        const stack: Array<{ id: string; i: number }> = [{ id: start, i: 0 }];
+        const path: string[] = [start];
+        color.set(start, GRAY);
+        while (stack.length) {
+            const frame = stack[stack.length - 1];
+            const neighbors = adj.get(frame.id) || [];
+            if (frame.i < neighbors.length) {
+                const v = neighbors[frame.i++];
+                const c = color.get(v) ?? WHITE;
+                if (c === GRAY) {
+                    // Back edge → mark the whole cycle from v to the current node.
+                    const idx = path.indexOf(v);
+                    if (idx >= 0) for (let k = idx; k < path.length; k++) inCycle.add(path[k]);
+                } else if (c === WHITE) {
+                    color.set(v, GRAY);
+                    path.push(v);
+                    stack.push({ id: v, i: 0 });
+                }
+            } else {
+                color.set(frame.id, BLACK);
+                path.pop();
+                stack.pop();
+            }
+        }
+    }
+    return inCycle;
+}
+
+/** Build the per-node issue map, render badges, and update the toolbar button. */
+function _computeAndMarkIssues(nodeGroup: SVGGElement): void {
+    const issues = new Map<string, string[]>();
+    const add = (id: string, msg: string): void => {
+        const list = issues.get(id);
+        if (list) list.push(msg); else issues.set(id, [msg]);
+    };
+
+    // Dangling references: the referrer still exists but its target is gone.
+    for (const br of _brokenRefs) {
+        add(br.by, t('graph.issue.broken_ref', { field: _humanField(br.field) }));
+    }
+
+    // Dependency cycles.
+    if (_nodeMap && _edges) {
+        for (const id of _detectCycles(_nodeMap, _edges)) add(id, t('graph.issue.cycle'));
+    }
+
+    _issueIds = new Set(issues.keys());
+    markIssues(nodeGroup, issues);
+    _updateIssuesButton();
+}
+
+function _updateIssuesButton(): void {
+    const btn = document.getElementById('graph-issues-btn');
+    if (!btn) return;
+    const count = _issueIds.size;
+    const countEl = btn.querySelector('.graph-issues-count');
+    if (countEl) countEl.textContent = count > 0 ? String(count) : '';
+    (btn as HTMLElement).style.display = count > 0 ? '' : 'none';
+}
+
+/**
+ * Export the full wiring topology (nodes + edges + validation report) as a
+ * downloadable JSON file. This is the read-only half of "wiring blueprints":
+ * a shareable, inspectable snapshot. Re-importing/instantiating a blueprint
+ * (with id remapping) is a separate, larger feature.
+ */
+export async function graphExportTopology(): Promise<void> {
+    try {
+        const topo = await apiGet<unknown>('/graph');
+        const blob = new Blob([JSON.stringify(topo, null, 2)], { type: 'application/json' });
+        const url = URL.createObjectURL(blob);
+        const a = document.createElement('a');
+        a.href = url;
+        a.download = `ledgrab-graph-${new Date().toISOString().slice(0, 10)}.json`;
+        document.body.appendChild(a);
+        a.click();
+        a.remove();
+        URL.revokeObjectURL(url);
+        showToast(t('graph.export_done'), 'success');
+    } catch (e) {
+        showToast(e instanceof Error ? e.message : t('graph.export_failed'), 'error');
+    }
+}
+
+/** Frame and highlight all nodes flagged with configuration issues. */
+export function graphShowIssues(): void {
+    if (_issueIds.size === 0 || !_nodeMap || !_canvas) {
+        showToast(t('graph.issues_none'), 'info');
+        return;
+    }
+    const ng = document.querySelector('.graph-nodes') as SVGGElement | null;
+    const eg = document.querySelector('.graph-edges') as SVGGElement | null;
+    _selectedIds = new Set(_issueIds);
+    if (ng) {
+        updateSelection(ng, _selectedIds);
+        ng.querySelectorAll('.graph-node').forEach((n: any) => {
+            n.style.opacity = _issueIds.has(n.getAttribute('data-id')) ? '1' : '0.2';
+        });
+    }
+    if (eg) clearEdgeHighlights(eg);
+
+    // Fit the viewport to the bounding box of the flagged nodes.
+    let minX = Infinity, minY = Infinity, maxX = -Infinity, maxY = -Infinity;
+    for (const id of _issueIds) {
+        const n = _nodeMap.get(id);
+        if (!n) continue;
+        minX = Math.min(minX, n.x); minY = Math.min(minY, n.y);
+        maxX = Math.max(maxX, n.x + n.width); maxY = Math.max(maxY, n.y + n.height);
+    }
+    if (minX !== Infinity) {
+        _canvas.fitAll({ x: minX, y: minY, width: maxX - minX, height: maxY - minY }, true);
+    }
+}
+
 // Entity kind → window function to open add/create modal + icon path
 const _ico = (d: string): string => `<svg class="icon" viewBox="0 0 24 24">${d}</svg>`;
 const _w = window as any;
@@ -693,6 +864,25 @@ const ALL_CACHES = [
     automationsCacheObj, csptCache,
 ];
 
+// entity kind → its DataCache, so a kind-scoped watcher (create-and-connect)
+// only reacts to new entities of the expected kind, never an unrelated one.
+const KIND_CACHE: Record<string, { data?: any[]; subscribe(fn: (d: any) => void): void; unsubscribe(fn: (d: any) => void): void }> = {
+    device: devicesCache,
+    capture_template: captureTemplatesCache,
+    pp_template: ppTemplatesCache,
+    audio_template: audioTemplatesCache,
+    pattern_template: patternTemplatesCache,
+    picture_source: streamsCache,
+    audio_source: audioSourcesCache,
+    value_source: valueSourcesCache,
+    color_strip_source: colorStripSourcesCache,
+    sync_clock: syncClocksCache,
+    output_target: outputTargetsCache,
+    scene_preset: scenePresetsCache,
+    automation: automationsCacheObj,
+    cspt: csptCache,
+};
+
 export function graphAddEntity(): void {
     const items = ADD_ENTITY_MAP.map(item => ({
         value: item.kind,
@@ -712,16 +902,62 @@ export function graphAddEntity(): void {
     });
 }
 
+/**
+ * Drag-from-port onto empty canvas → offer to create a compatible consumer
+ * entity and wire it to the source in one gesture (the classic node-editor
+ * "drag out a new node" flow).
+ */
+function _promptCreateAndConnect(sourceKind: string, sourceId: string): void {
+    // Kinds that can consume this source (non-nested) and have an add action.
+    const kinds = [...new Set(getCompatibleInputs(sourceKind).map(c => c.targetKind))]
+        .filter(k => ADD_ENTITY_MAP.some(e => e.kind === k));
+    if (kinds.length === 0) {
+        showToast(t('graph.no_compatible_connection'), 'info');
+        return;
+    }
+    const items = kinds.map(k => {
+        const entry = ADD_ENTITY_MAP.find(e => e.kind === k)!;
+        return { value: k, icon: entry.icon, label: ENTITY_LABELS[k] || k.replace(/_/g, ' ') };
+    });
+    showTypePicker({
+        title: t('graph.create_and_connect'),
+        items,
+        onPick: (kind) => _createAndConnect(kind, sourceKind, sourceId),
+    });
+}
+
+/** Open the add-entity modal for `targetKind`, then wire the new entity to `sourceId`. */
+function _createAndConnect(targetKind: string, sourceKind: string, sourceId: string): void {
+    const entry = ADD_ENTITY_MAP.find(e => e.kind === targetKind);
+    if (!entry) return;
+    _watchForNewEntity((newId) => {
+        const matches = findConnection(targetKind, sourceKind);
+        if (matches.length === 1) {
+            _doConnect(newId, targetKind, matches[0].field, sourceId);
+        } else if (matches.length > 1) {
+            _promptConnectionField(matches, newId, targetKind, sourceId);
+        } else {
+            // No resolvable field — just refresh so the new node appears.
+            loadGraphEditor();
+        }
+    }, targetKind);
+    entry.fn();
+}
+
 // Watch for new entity creation after add-entity menu action
 let _entityWatchCleanup: (() => void) | null = null;
 
-function _watchForNewEntity(): void {
+function _watchForNewEntity(onNew?: (newId: string) => void, expectKind?: string): void {
     // Cleanup any previous watcher
     if (_entityWatchCleanup) _entityWatchCleanup();
 
+    // Scope to the expected kind's cache when given (create-and-connect), so the
+    // callback never fires for an unrelated entity that happens to appear first.
+    const caches = (expectKind && KIND_CACHE[expectKind]) ? [KIND_CACHE[expectKind]] : ALL_CACHES;
+
     // Snapshot all current IDs
     const knownIds = new Set<string>();
-    for (const cache of ALL_CACHES) {
+    for (const cache of caches) {
         for (const item of (cache.data || [])) {
             if (item.id) knownIds.add(item.id);
         }
@@ -731,9 +967,12 @@ function _watchForNewEntity(): void {
         if (!Array.isArray(data)) return;
         for (const item of data) {
             if (item.id && !knownIds.has(item.id)) {
-                // Found a new entity — reload graph and zoom to it
+                // Found a new entity.
                 const newId = item.id;
                 cleanup();
+                // Custom handler (e.g. create-and-connect) takes over.
+                if (onNew) { onNew(newId); return; }
+                // Default: reload graph and zoom to the new node.
                 loadGraphEditor().then(() => {
                     const node = _nodeMap?.get(newId);
                     if (node && _canvas) {
@@ -751,14 +990,14 @@ function _watchForNewEntity(): void {
         }
     };
 
-    for (const cache of ALL_CACHES) cache.subscribe(handler);
+    for (const cache of caches) cache.subscribe(handler);
 
     // Auto-cleanup after 2 minutes (user might cancel the modal)
     const timeout = setTimeout(cleanup, 120_000);
 
     function cleanup() {
         clearTimeout(timeout);
-        for (const cache of ALL_CACHES) cache.unsubscribe(handler);
+        for (const cache of caches) cache.unsubscribe(handler);
         _entityWatchCleanup = null;
     }
 
@@ -829,6 +1068,9 @@ function _renderGraph(container: HTMLElement): void {
     });
     markOrphans(nodeGroup, _nodeMap!, _edges!);
 
+    // Health overlay: flag dangling references and dependency cycles.
+    _computeAndMarkIssues(nodeGroup);
+
     // Animated flow dots for running nodes
     const runningIds = new Set<string>();
     for (const node of _nodeMap!.values()) {
@@ -845,6 +1087,8 @@ function _renderGraph(container: HTMLElement): void {
     _canvas.onZoomChange = (z) => {
         const label = container.querySelector('.graph-zoom-label');
         if (label) label.textContent = `${Math.round(z * 100)}%`;
+        // Reveal edge field labels once zoomed in enough to read them.
+        edgeGroup.classList.toggle('show-labels', z >= 0.9);
     };
 
     _canvas.onViewChange = (vp) => {
@@ -993,6 +1237,9 @@ function _renderGraph(container: HTMLElement): void {
     container.focus();
     // Re-focus when clicking inside the graph
     svgEl.addEventListener('pointerdown', () => container.focus());
+    // The toolbar markup hardcodes `disabled` on undo/redo; re-sync with the
+    // live stacks since this render may follow an undoable action.
+    _updateUndoRedoButtons();
     _initialized = true;
 }
 
@@ -1048,6 +1295,10 @@ function _graphHTML(): string {
                 <button class="btn-icon" onclick="graphRelayout()" title="${t('graph.relayout')}" data-collapse>
                     <svg class="icon" viewBox="0 0 24 24"><path d="M3 12a9 9 0 0 1 9-9 9.75 9.75 0 0 1 6.74 2.74L21 8"/><path d="M21 3v5h-5"/><path d="M21 12a9 9 0 0 1-9 9 9.75 9.75 0 0 1-6.74-2.74L3 16"/><path d="M8 16H3v5"/></svg>
                 </button>
+                <button class="btn-icon graph-issues-btn" id="graph-issues-btn" onclick="graphShowIssues()" title="${t('graph.issues')}" style="display:none" data-collapse>
+                    <svg class="icon" viewBox="0 0 24 24"><path d="m21.73 18-8-14a2 2 0 0 0-3.48 0l-8 14A2 2 0 0 0 4 21h16a2 2 0 0 0 1.73-3"/><path d="M12 9v4"/><path d="M12 17h.01"/></svg>
+                    <span class="graph-issues-count"></span>
+                </button>
                 <button class="btn-icon" onclick="graphToggleFullscreen()" title="${t('graph.fullscreen')} (F11)" data-collapse>
                     <svg class="icon" viewBox="0 0 24 24"><path d="M8 3H5a2 2 0 0 0-2 2v3"/><path d="M21 8V5a2 2 0 0 0-2-2h-3"/><path d="M3 16v3a2 2 0 0 0 2 2h3"/><path d="M16 21h3a2 2 0 0 0 2-2v-3"/></svg>
                 </button>
@@ -1098,6 +1349,10 @@ function _graphHTML(): string {
                     <svg class="icon" viewBox="0 0 24 24"><path d="M8 3H5a2 2 0 0 0-2 2v3"/><path d="M21 8V5a2 2 0 0 0-2-2h-3"/><path d="M3 16v3a2 2 0 0 0 2 2h3"/><path d="M16 21h3a2 2 0 0 0 2-2v-3"/></svg>
                     <span>${t('graph.fullscreen')}</span>
                 </button>
+                <button onclick="graphExportTopology(); closeToolbarOverflow()">
+                    <svg class="icon" viewBox="0 0 24 24"><path d="M21 15v4a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2v-4"/><path d="M7 10l5 5 5-5"/><path d="M12 15V3"/></svg>
+                    <span>${t('graph.export')}</span>
+                </button>
                 <div class="graph-overflow-sep"></div>
                 <button id="graph-overflow-help" onclick="toggleGraphHelp(); closeToolbarOverflow()">
                     <svg class="icon" viewBox="0 0 24 24"><circle cx="12" cy="12" r="10"/><path d="M9.09 9a3 3 0 0 1 5.83 1c0 2-3 3-3 3"/><path d="M12 17h.01"/></svg>
@@ -1525,7 +1780,8 @@ function _onEditNode(node: any) {
     fnMap[node.kind]?.();
 }
 
-function _onDeleteNode(node: any) {
+/** Dispatch the per-entity delete (each shows its own confirm + handles API/cache). */
+function _deleteNodeRaw(node: any): void {
     const fnMap: any = {
         device: () => _w.removeDevice?.(node.id),
         capture_template: () => _w.deleteTemplate?.(node.id),
@@ -1545,6 +1801,30 @@ function _onDeleteNode(node: any) {
     fnMap[node.kind]?.();
 }
 
+// Guards the await gap (dependents fetch + confirm) against a double-fire from
+// rapid Delete presses or trash-button + Delete on the same node.
+const _deletingIds = new Set<string>();
+
+/**
+ * Single-node delete from the graph: first warn if other entities reference
+ * this one (their wiring would break), then hand off to the per-entity delete.
+ */
+async function _onDeleteNode(node: any): Promise<void> {
+    if (_deletingIds.has(node.id)) return;
+    _deletingIds.add(node.id);
+    try {
+        const deps = await getDependents(node.kind, node.id);
+        if (deps.length > 0) {
+            const names = deps.slice(0, 5).map(d => d.name).join(', ') + (deps.length > 5 ? ', …' : '');
+            const ok = await showConfirm(t('graph.delete_with_dependents_confirm', { count: deps.length, names }));
+            if (!ok) return;
+        }
+        _deleteNodeRaw(node);
+    } finally {
+        _deletingIds.delete(node.id);
+    }
+}
+
 async function _bulkDeleteSelected(): Promise<void> {
     const count = _selectedIds.size;
     if (count < 2) return;
@@ -1552,9 +1832,11 @@ async function _bulkDeleteSelected(): Promise<void> {
         (t('graph.bulk_delete_confirm') || 'Delete {count} selected entities?').replace('{count}', String(count))
     );
     if (!ok) return;
+    // Bulk uses the raw delegate — the single bulk confirm covers the batch, and
+    // per-node dependents prompts would be a dialog storm.
     for (const id of _selectedIds) {
         const node = _nodeMap?.get(id);
-        if (node) _onDeleteNode(node);
+        if (node) _deleteNodeRaw(node);
     }
     _selectedIds.clear();
 }
@@ -1991,17 +2273,37 @@ function _onDragPointerUp(): void {
         _justDragged = true;
         requestAnimationFrame(() => { _justDragged = false; });
 
+        const moved: Array<{ id: string; oldX: number; oldY: number; newX: number; newY: number }> = [];
+
         if (_dragState.multi) {
             _dragState.nodes.forEach(n => {
                 if (n.el) n.el.classList.remove('dragging');
                 const node = _nodeMap!.get(n.id);
-                if (node) _manualPositions.set(n.id, { x: node.x, y: node.y });
+                if (node) {
+                    _manualPositions.set(n.id, { x: node.x, y: node.y });
+                    moved.push({ id: n.id, oldX: n.startX, oldY: n.startY, newX: node.x, newY: node.y });
+                }
             });
         } else {
             const ds = _dragState as DragStateSingle;
             ds.el.classList.remove('dragging');
             const node = _nodeMap!.get(ds.nodeId);
-            if (node) _manualPositions.set(ds.nodeId, { x: node.x, y: node.y });
+            if (node) {
+                _manualPositions.set(ds.nodeId, { x: node.x, y: node.y });
+                moved.push({ id: ds.nodeId, oldX: ds.startNode.x, oldY: ds.startNode.y, newX: node.x, newY: node.y });
+            }
+        }
+
+        // Persist the hand-arranged layout so it survives page reloads.
+        _saveManualPositions();
+
+        // Record an undoable move (skip no-op drags below the dead zone).
+        if (moved.some(m => m.oldX !== m.newX || m.oldY !== m.newY)) {
+            pushUndoAction({
+                label: t('graph.action.move'),
+                undo: async () => { for (const m of moved) _manualPositions.set(m.id, { x: m.oldX, y: m.oldY }); _saveManualPositions(); },
+                redo: async () => { for (const m of moved) _manualPositions.set(m.id, { x: m.newX, y: m.newY }); _saveManualPositions(); },
+            });
         }
 
         _bounds = _calcBounds(_nodeMap);
@@ -2201,11 +2503,26 @@ function _initPortDrag(svgEl: SVGSVGElement, nodeGroup: SVGGElement, _edgeGroup:
                 p.classList.add('graph-port-incompatible');
             }
         });
+
+        // Also highlight whole compatible target NODES, so a slot with no
+        // existing edge (and therefore no input port yet) is still droppable —
+        // the user can drop anywhere on the node body to wire an empty slot.
+        const compatibleKinds = new Set(compatible.map(c => c.targetKind));
+        nodeGroup.querySelectorAll('.graph-node').forEach(n => {
+            const nKind = n.getAttribute('data-kind');
+            const nId = n.getAttribute('data-id');
+            if (nId !== sourceNodeId && nKind && compatibleKinds.has(nKind)) {
+                n.classList.add('graph-node-compatible');
+            }
+        });
     }, true); // capture phase to beat node drag
 
     if (!_connectListenersAdded) {
         window.addEventListener('pointermove', _onConnectPointerMove);
         window.addEventListener('pointerup', _onConnectPointerUp);
+        // pointercancel (touch interruption, capture loss) must also tear down
+        // the drag — otherwise the temp edge, node highlights and blockPan stick.
+        window.addEventListener('pointercancel', _onConnectPointerUp);
         _connectListenersAdded = true;
     }
 }
@@ -2228,12 +2545,20 @@ function _onConnectPointerMove(e: PointerEvent): void {
 
     svgEl.querySelectorAll('.graph-port-drop-target').forEach(p => p.classList.remove('graph-port-drop-target'));
     if (port) port.classList.add('graph-port-drop-target');
+
+    // Highlight the compatible node under the cursor for drop-on-node wiring
+    // (only when not already hovering a specific port).
+    svgEl.querySelectorAll('.graph-node-drop-target').forEach(n => n.classList.remove('graph-node-drop-target'));
+    if (!port) {
+        const nodeUnder = elem?.closest?.('.graph-node-compatible');
+        if (nodeUnder) nodeUnder.classList.add('graph-node-drop-target');
+    }
 }
 
 function _onConnectPointerUp(e: PointerEvent): void {
     if (!_connectState) return;
 
-    const { sourceNodeId, sourceKind, portType, dragPath } = _connectState;
+    const { sourceNodeId, sourceKind, startX, startY, dragPath } = _connectState;
 
     // Clean up drag edge
     dragPath.remove();
@@ -2241,48 +2566,132 @@ function _onConnectPointerUp(e: PointerEvent): void {
     if (svgEl) svgEl.classList.remove('connecting');
     if (_canvas) _canvas.blockPan = false;
 
-    // Clean up port highlights
+    // Clean up port + node highlights
     const nodeGroup = document.querySelector('.graph-nodes') as SVGGElement | null;
     if (nodeGroup) {
         nodeGroup.querySelectorAll('.graph-port-compatible, .graph-port-incompatible, .graph-port-drop-target').forEach(p => {
             p.classList.remove('graph-port-compatible', 'graph-port-incompatible', 'graph-port-drop-target');
         });
+        nodeGroup.querySelectorAll('.graph-node-compatible, .graph-node-drop-target').forEach(n => {
+            n.classList.remove('graph-node-compatible', 'graph-node-drop-target');
+        });
     }
 
-    // Check if dropped on a compatible input port
     const elem = document.elementFromPoint(e.clientX, e.clientY);
     const targetPort = elem?.closest?.('.graph-port-in');
     if (targetPort) {
+        // Dropped on a specific input port — resolve by that port's edge type.
         const targetNodeId = targetPort.getAttribute('data-node-id') ?? '';
         const targetKind = targetPort.getAttribute('data-node-kind') ?? '';
         const targetPortType = targetPort.getAttribute('data-port-type') ?? '';
 
         if (targetNodeId !== sourceNodeId) {
-            // Find the matching connection
-            const matches = findConnection(targetKind, sourceKind, targetPortType);
+            const matches = _availableMatches(findConnection(targetKind, sourceKind, targetPortType), targetNodeId);
             if (matches.length === 1) {
                 _doConnect(targetNodeId, targetKind, matches[0].field, sourceNodeId);
             } else if (matches.length > 1) {
-                // Multiple possible fields (e.g., template → picture_source could be capture or pp template)
-                // Resolve by source kind
-                const exact = matches.find(m => m.sourceKind === sourceKind);
-                if (exact) {
-                    _doConnect(targetNodeId, targetKind, exact.field, sourceNodeId);
+                // Genuinely ambiguous: the same source kind feeds two distinct
+                // fields (e.g. an automation's activation vs. deactivation scene).
+                _promptConnectionField(matches, targetNodeId, targetKind, sourceNodeId);
+            }
+        }
+    } else {
+        // Dropped on the node body (or an empty slot that has no port yet):
+        // resolve every connectable field for this source→target pair. This is
+        // what makes unconnected slots wireable from the graph.
+        const targetNode = elem?.closest?.('.graph-node');
+        if (targetNode) {
+            const targetNodeId = targetNode.getAttribute('data-id') ?? '';
+            const targetKind = targetNode.getAttribute('data-kind') ?? '';
+            if (targetNodeId && targetNodeId !== sourceNodeId) {
+                const matches = _availableMatches(findConnection(targetKind, sourceKind), targetNodeId);
+                if (matches.length === 1) {
+                    _doConnect(targetNodeId, targetKind, matches[0].field, sourceNodeId);
+                } else if (matches.length > 1) {
+                    _promptConnectionField(matches, targetNodeId, targetKind, sourceNodeId);
+                } else {
+                    showToast(t('graph.no_compatible_connection'), 'info');
                 }
             }
+        } else if (_canvas) {
+            // Dropped on empty canvas — offer to create a compatible consumer
+            // and wire it (skip when the gesture was effectively a click).
+            const CREATE_CONNECT_MIN_DRAG = 40;  // graph units
+            const gp = _canvas.screenToGraph(e.clientX, e.clientY);
+            if (Math.hypot(gp.x - startX, gp.y - startY) > CREATE_CONNECT_MIN_DRAG) {
+                _promptCreateAndConnect(sourceKind, sourceNodeId);
+            }
         }
     }
 
     _connectState = null;
 }
 
+/**
+ * Keep only the bindable slots the target entity actually exposes (subtype-safe)
+ * — e.g. an "effect" strip offers `intensity`/`scale`, a "picture" strip offers
+ * `smoothing`. Non-bindable matches always pass through.
+ */
+function _availableMatches<T extends { field: string; bindable?: boolean }>(matches: T[], targetId: string): T[] {
+    const ent = _entitiesById.get(targetId);
+    return matches.filter(m => {
+        if (!m.bindable || !ent) return true;
+        return m.field.split('.')[0] in ent;
+    });
+}
+
+/** Ask the user which field to wire when a source maps to multiple target fields. */
+function _promptConnectionField(
+    matches: Array<{ field: string }>,
+    targetNodeId: string,
+    targetKind: string,
+    sourceNodeId: string,
+): void {
+    showTypePicker({
+        title: t('graph.choose_connection'),
+        items: matches.map(m => ({ value: m.field, icon: _ico(P.link), label: _humanField(m.field) })),
+        onPick: (field) => { _doConnect(targetNodeId, targetKind, field, sourceNodeId); },
+    });
+}
+
+/** The id currently wired into (targetId, field), or '' if the slot is empty. */
+function _currentSourceFor(targetId: string, field: string): string {
+    const edge = _edges?.find(e => e.to === targetId && e.field === field);
+    return edge ? edge.from : '';
+}
+
 async function _doConnect(targetId: string, targetKind: string, field: string, sourceId: string): Promise<void> {
+    const prevSourceId = _currentSourceFor(targetId, field);
+    if (prevSourceId === sourceId) return;  // dropped onto the existing connection — no-op
+
+    // Pre-flight validation (existence + source kind + no dependency cycle).
+    const v = await validateConnection(targetKind, targetId, field, sourceId);
+    if (!v.ok) {
+        showToast(v.error || t('graph.connection_failed'), 'error');
+        return;
+    }
+
+    // Confirm before overwriting an already-occupied slot.
+    if (prevSourceId) {
+        const confirmed = await showConfirm(t('graph.replace_connection_confirm'));
+        if (!confirmed) return;
+    }
+
     const ok = await updateConnection(targetId, targetKind, field, sourceId);
     if (ok) {
-        showToast(t('graph.connection_updated') || 'Connection updated', 'success');
+        // Record an undoable action that restores the previous slot occupant.
+        // The inverse ops throw on failure so `_undo`/`_redo` can keep the
+        // action on its stack instead of silently desyncing (updateConnection
+        // returns false rather than throwing on API error).
+        pushUndoAction({
+            label: t('graph.action.connect'),
+            undo: async () => { if (!(await updateConnection(targetId, targetKind, field, prevSourceId))) throw new Error(t('graph.connection_failed')); },
+            redo: async () => { if (!(await updateConnection(targetId, targetKind, field, sourceId))) throw new Error(t('graph.connection_failed')); },
+        });
+        showToast(t('graph.connection_updated'), 'success');
         await loadGraphEditor();
     } else {
-        showToast(t('graph.connection_failed') || 'Failed to update connection', 'error');
+        showToast(t('graph.connection_failed'), 'error');
     }
 }
 
@@ -2311,31 +2720,35 @@ export async function graphUndo(): Promise<void> { await _undo(); }
 export async function graphRedo(): Promise<void> { await _redo(); }
 
 async function _undo(): Promise<void> {
-    if (_undoStack.length === 0) { showToast(t('graph.nothing_to_undo') || 'Nothing to undo', 'info'); return; }
+    if (_undoStack.length === 0) { showToast(t('graph.nothing_to_undo'), 'info'); return; }
     const action = _undoStack.pop()!;
     try {
         await action.undo();
         _redoStack.push(action);
-        showToast(t('graph.undone') || `Undone: ${action.label}`, 'info');
+        showToast(t('graph.undone'), 'info');
         _updateUndoRedoButtons();
         await loadGraphEditor();
     } catch (e) {
-        showToast(e.message, 'error');
+        // The inverse op failed — keep the action on the undo stack so the
+        // user can retry, and surface the error instead of a false success.
+        _undoStack.push(action);
+        showToast(e instanceof Error ? e.message : String(e), 'error');
         _updateUndoRedoButtons();
     }
 }
 
 async function _redo(): Promise<void> {
-    if (_redoStack.length === 0) { showToast(t('graph.nothing_to_redo') || 'Nothing to redo', 'info'); return; }
+    if (_redoStack.length === 0) { showToast(t('graph.nothing_to_redo'), 'info'); return; }
     const action = _redoStack.pop()!;
     try {
         await action.redo();
         _undoStack.push(action);
-        showToast(t('graph.redone') || `Redone: ${action.label}`, 'info');
+        showToast(t('graph.redone'), 'info');
         _updateUndoRedoButtons();
         await loadGraphEditor();
     } catch (e) {
-        showToast(e.message, 'error');
+        _redoStack.push(action);
+        showToast(e instanceof Error ? e.message : String(e), 'error');
         _updateUndoRedoButtons();
     }
 }
@@ -2402,6 +2815,28 @@ export function toggleGraphHelp(): void {
 
 /* ── Edge context menu (right-click to detach) ── */
 
+/**
+ * Detach a connection and record an undoable action that restores it.
+ * @param prevSourceId the id previously wired into the slot (for undo)
+ */
+async function _doDetach(to: string, targetKind: string, field: string, prevSourceId: string): Promise<boolean> {
+    const ok = await detachConnection(to, targetKind, field);
+    if (ok) {
+        if (prevSourceId) {
+            pushUndoAction({
+                label: t('graph.action.disconnect'),
+                undo: async () => { if (!(await updateConnection(to, targetKind, field, prevSourceId))) throw new Error(t('graph.connection_failed')); },
+                redo: async () => { if (!(await detachConnection(to, targetKind, field))) throw new Error(t('graph.disconnect_failed')); },
+            });
+        }
+        showToast(t('graph.connection_removed'), 'success');
+        await loadGraphEditor();
+    } else {
+        showToast(t('graph.disconnect_failed'), 'error');
+    }
+    return ok;
+}
+
 function _onEdgeContextMenu(edgePath: Element, e: MouseEvent, container: HTMLElement): void {
     _dismissEdgeContextMenu();
 
@@ -2409,6 +2844,7 @@ function _onEdgeContextMenu(edgePath: Element, e: MouseEvent, container: HTMLEle
     if (!isEditableEdge(field)) return;  // nested fields can't be detached from graph
 
     const toId = edgePath.getAttribute('data-to') ?? '';
+    const fromId = edgePath.getAttribute('data-from') ?? '';
     const toNode = _nodeMap?.get(toId);
     if (!toNode) return;
 
@@ -2419,19 +2855,13 @@ function _onEdgeContextMenu(edgePath: Element, e: MouseEvent, container: HTMLEle
 
     const btn = document.createElement('button');
     btn.className = 'graph-edge-menu-item danger';
-    btn.textContent = t('graph.disconnect') || 'Disconnect';
+    btn.textContent = t('graph.disconnect');
     btn.addEventListener('click', async () => {
         try {
             _dismissEdgeContextMenu();
-            const ok = await detachConnection(toId, toNode.kind, field);
-            if (ok) {
-                showToast(t('graph.connection_removed') || 'Connection removed', 'success');
-                await loadGraphEditor();
-            } else {
-                showToast(t('graph.disconnect_failed') || 'Failed to disconnect', 'error');
-            }
+            await _doDetach(toId, toNode.kind, field, fromId);
         } catch (err) {
-            showToast(`${t('graph.disconnect_failed') || 'Failed to disconnect'}: ${err instanceof Error ? err.message : String(err)}`, 'error');
+            showToast(`${t('graph.disconnect_failed')}: ${err instanceof Error ? err.message : String(err)}`, 'error');
         }
     });
     menu.appendChild(btn);
@@ -2449,16 +2879,9 @@ function _dismissEdgeContextMenu(): void {
 
 async function _detachSelectedEdge(): Promise<void> {
     if (!_selectedEdge) return;
-    const { to, field, targetKind } = _selectedEdge;
+    const { from, to, field, targetKind } = _selectedEdge;
     _selectedEdge = null;
-
-    const ok = await detachConnection(to, targetKind, field);
-    if (ok) {
-        showToast(t('graph.connection_removed') || 'Connection removed', 'success');
-        await loadGraphEditor();
-    } else {
-        showToast(t('graph.disconnect_failed') || 'Failed to disconnect', 'error');
-    }
+    await _doDetach(to, targetKind, field, from);
 }
 
 /* ── Node hover FPS tooltip ── */

server/src/ledgrab/static/js/global.d.ts

@@ -377,6 +377,8 @@ startTargetOverlay: (...args: any[]) => any;
     graphZoomIn: (...args: any[]) => any;
     graphZoomOut: (...args: any[]) => any;
     graphRelayout: (...args: any[]) => any;
+    graphShowIssues: (...args: any[]) => any;
+    graphExportTopology: (...args: any[]) => any;
     graphToggleFullscreen: (...args: any[]) => any;
     graphAddEntity: (...args: any[]) => any;
 

server/src/ledgrab/static/locales/en.json

@@ -362,6 +362,9 @@
   "device.mqtt_topic": "MQTT Topic:",
   "device.mqtt_topic.hint": "MQTT topic path for publishing pixel data (e.g. mqtt://ledgrab/device/name)",
   "device.mqtt_topic.placeholder": "mqtt://ledgrab/device/living-room",
+  "device.mqtt_source": "MQTT Broker:",
+  "device.mqtt_source.hint": "Which MQTT broker this device publishes to. Manage brokers under Integrations → MQTT Sources. Leave unset to use the first available broker.",
+  "device.mqtt_source.none": "— First available broker",
   "device.ws_url": "Connection URL:",
   "device.ws_url.hint": "WebSocket URL for clients to connect and receive LED data",
   "device.openrgb.url": "OpenRGB URL:",
@@ -2582,6 +2585,23 @@
   "graph.tooltip.fps": "FPS",
   "graph.tooltip.errors": "Errors",
   "graph.tooltip.uptime": "Uptime",
+  "graph.undone": "Undone",
+  "graph.redone": "Redone",
+  "graph.action.connect": "Connect",
+  "graph.action.disconnect": "Disconnect",
+  "graph.action.move": "Move node",
+  "graph.choose_connection": "Choose connection",
+  "graph.issues": "Issues",
+  "graph.issues_none": "No issues found",
+  "graph.issue.broken_ref": "Broken reference: {field}",
+  "graph.issue.cycle": "Part of a dependency cycle",
+  "graph.replace_connection_confirm": "Replace the existing connection?",
+  "graph.no_compatible_connection": "No compatible connection between these entities",
+  "graph.create_and_connect": "Create & connect…",
+  "graph.export": "Export graph (JSON)",
+  "graph.export_done": "Graph exported",
+  "graph.export_failed": "Failed to export graph",
+  "graph.delete_with_dependents_confirm": "This entity is used by {count} other(s): {names}. Delete it and break those connections?",
   "automation.enabled": "Automation enabled",
   "automation.disabled": "Automation disabled",
   "scene_preset.activated": "Preset activated",

server/src/ledgrab/static/locales/ru.json

@@ -417,6 +417,9 @@
   "device.mqtt_topic": "MQTT Топик:",
   "device.mqtt_topic.hint": "MQTT топик для публикации пиксельных данных (напр. mqtt://ledgrab/device/name)",
   "device.mqtt_topic.placeholder": "mqtt://ledgrab/device/гостиная",
+  "device.mqtt_source": "MQTT Брокер:",
+  "device.mqtt_source.hint": "К какому MQTT-брокеру публикует это устройство. Брокеры настраиваются в разделе Интеграции → Источники MQTT. Оставьте пустым, чтобы использовать первый доступный брокер.",
+  "device.mqtt_source.none": "— Первый доступный брокер",
   "device.ws_url": "URL подключения:",
   "device.ws_url.hint": "WebSocket URL для подключения клиентов и получения LED данных",
   "device.openrgb.url": "OpenRGB URL:",
@@ -2264,6 +2267,23 @@
   "graph.tooltip.fps": "FPS",
   "graph.tooltip.errors": "Ошибки",
   "graph.tooltip.uptime": "Время работы",
+  "graph.undone": "Отменено",
+  "graph.redone": "Повторено",
+  "graph.action.connect": "Соединить",
+  "graph.action.disconnect": "Отсоединить",
+  "graph.action.move": "Переместить узел",
+  "graph.choose_connection": "Выберите соединение",
+  "graph.issues": "Проблемы",
+  "graph.issues_none": "Проблем не найдено",
+  "graph.issue.broken_ref": "Битая ссылка: {field}",
+  "graph.issue.cycle": "Входит в цикл зависимостей",
+  "graph.replace_connection_confirm": "Заменить существующее соединение?",
+  "graph.no_compatible_connection": "Нет совместимого соединения между этими объектами",
+  "graph.create_and_connect": "Создать и соединить…",
+  "graph.export": "Экспорт графа (JSON)",
+  "graph.export_done": "Граф экспортирован",
+  "graph.export_failed": "Не удалось экспортировать граф",
+  "graph.delete_with_dependents_confirm": "Этот объект используется {count} другими: {names}. Удалить и разорвать эти связи?",
   "automation.enabled": "Автоматизация включена",
   "automation.disabled": "Автоматизация выключена",
   "scene_preset.activated": "Пресет активирован",

server/src/ledgrab/static/locales/zh.json

@@ -415,6 +415,9 @@
   "device.mqtt_topic": "MQTT 主题：",
   "device.mqtt_topic.hint": "用于发布像素数据的 MQTT 主题路径（例如 mqtt://ledgrab/device/name）",
   "device.mqtt_topic.placeholder": "mqtt://ledgrab/device/客厅",
+  "device.mqtt_source": "MQTT 代理：",
+  "device.mqtt_source.hint": "此设备发布到哪个 MQTT 代理。在集成 → MQTT 源中管理代理。留空则使用第一个可用代理。",
+  "device.mqtt_source.none": "— 第一个可用代理",
   "device.ws_url": "连接 URL：",
   "device.ws_url.hint": "客户端连接并接收 LED 数据的 WebSocket URL",
   "device.openrgb.url": "OpenRGB URL：",
@@ -2260,6 +2263,23 @@
   "graph.tooltip.fps": "帧率",
   "graph.tooltip.errors": "错误",
   "graph.tooltip.uptime": "运行时间",
+  "graph.undone": "已撤销",
+  "graph.redone": "已重做",
+  "graph.action.connect": "连接",
+  "graph.action.disconnect": "断开连接",
+  "graph.action.move": "移动节点",
+  "graph.choose_connection": "选择连接",
+  "graph.issues": "问题",
+  "graph.issues_none": "未发现问题",
+  "graph.issue.broken_ref": "无效引用：{field}",
+  "graph.issue.cycle": "属于依赖循环",
+  "graph.replace_connection_confirm": "替换现有连接？",
+  "graph.no_compatible_connection": "这些实体之间没有兼容的连接",
+  "graph.create_and_connect": "创建并连接…",
+  "graph.export": "导出图谱 (JSON)",
+  "graph.export_done": "图谱已导出",
+  "graph.export_failed": "导出图谱失败",
+  "graph.delete_with_dependents_confirm": "此实体被 {count} 个其他实体引用：{names}。删除并断开这些连接？",
   "automation.enabled": "自动化已启用",
   "automation.disabled": "自动化已禁用",
   "scene_preset.activated": "预设已激活",

server/src/ledgrab/static/sw.js

@@ -4,20 +4,233 @@
  * Strategy:
  *   - Static assets (/static/): stale-while-revalidate
  *   - API / config requests: network-only (device control must be live)
- *   - Navigation: network-first with offline fallback
+ *   - Navigation: network-first with branded offline fallback
  */
 
-const CACHE_NAME = 'ledgrab-v34';
+const CACHE_NAME = 'ledgrab-v35';
 
 // Only pre-cache static assets (no auth required).
 // Do NOT pre-cache '/' — it requires API key auth and would cache an error page.
+// The Orbitron brand font is precached so the offline page renders on-brand
+// even on a device that hasn't warmed the font cache yet.
 const PRECACHE_URLS = [
     '/static/dist/app.bundle.css',
     '/static/dist/app.bundle.js',
     '/static/icons/icon-192.png',
     '/static/icons/icon-512.png',
+    '/static/fonts/orbitron-700-latin.woff2',
 ];
 
+// Branded offline fallback shown when a navigation can't reach the server.
+// Self-contained (no CDN, no app CSS) so it renders with zero live network.
+// Mirrors the "Lumenworks" console aesthetic: pure-black panel, Orbitron brand
+// mark, channel-coral for the offline/alarm state, signal-green for restore.
+// A background probe self-heals the page — it reloads the instant the server
+// answers again, so a restarting server no longer leaves a dead-end screen.
+const OFFLINE_HTML = `<!DOCTYPE html>
+<html lang="en">
+<head>
+<meta charset="utf-8">
+<meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover">
+<meta name="color-scheme" content="dark light">
+<title>LED Grab — Signal Lost</title>
+<style>
+  *{margin:0;padding:0;box-sizing:border-box}
+  :root{
+    --bg:#000;--line:#1c2027;
+    --ink:#eef2f7;--dim:#aeb7c4;--mute:#6b7480;
+    --coral:#ff5e5e;
+    --signal:#4caf50;--signal-hi:#6fd173;
+    --glow-coral:0 0 18px rgba(255,94,94,.55);
+    --glow-signal:0 0 10px rgba(76,175,80,.8);
+  }
+  @media (prefers-color-scheme: light){
+    :root{
+      --bg:#f6f8fb;--line:#dee3ea;
+      --ink:#0f1419;--dim:#41505f;--mute:#7b8694;
+      --coral:#d8392e;
+      --signal:#2e7d32;--signal-hi:#3d8b40;
+      --glow-coral:0 0 16px rgba(216,57,46,.30);
+      --glow-signal:0 0 10px rgba(46,125,50,.5);
+    }
+  }
+  @font-face{
+    font-family:'Orbitron';font-style:normal;font-weight:700;font-display:swap;
+    src:url('/static/fonts/orbitron-700-latin.woff2') format('woff2');
+  }
+  html,body{height:100%}
+  body{
+    background:var(--bg);color:var(--ink);
+    font-family:'Manrope','Segoe UI',system-ui,-apple-system,BlinkMacSystemFont,sans-serif;
+    -webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility;
+    display:grid;place-items:center;min-height:100dvh;position:relative;overflow:hidden;
+    padding:calc(28px + env(safe-area-inset-top)) 24px calc(28px + env(safe-area-inset-bottom));
+  }
+  /* atmosphere: coral alarm vignette + faint signal floor */
+  body::before{
+    content:'';position:fixed;inset:0;z-index:0;pointer-events:none;
+    background:
+      radial-gradient(125% 80% at 50% -12%, rgba(255,94,94,.11), transparent 60%),
+      radial-gradient(100% 55% at 50% 118%, rgba(0,216,255,.045), transparent 60%);
+  }
+  /* fine equipment-panel scanlines */
+  body::after{
+    content:'';position:fixed;inset:0;z-index:0;pointer-events:none;opacity:.5;
+    mix-blend-mode:screen;
+    background:repeating-linear-gradient(0deg, rgba(255,255,255,.018) 0 1px, transparent 1px 3px);
+  }
+  @media (prefers-color-scheme: light){
+    body::after{opacity:.4;mix-blend-mode:multiply;
+      background:repeating-linear-gradient(0deg, rgba(0,0,0,.02) 0 1px, transparent 1px 3px)}
+  }
+  .panel{position:relative;z-index:1;width:min(460px,100%);
+    display:flex;flex-direction:column;align-items:center;text-align:center}
+  .panel>*{opacity:0;transform:translateY(10px);animation:rise .6s cubic-bezier(.16,1,.3,1) forwards}
+  .brand{animation-delay:.05s}.strip-wrap{animation-delay:.14s}.chip{animation-delay:.22s}
+  .headline{animation-delay:.30s}.copy{animation-delay:.38s}.btn{animation-delay:.46s}
+  .telemetry{animation-delay:.54s}.foot{animation-delay:.62s}
+  @keyframes rise{to{opacity:1;transform:none}}
+
+  .brand{display:flex;align-items:center;gap:11px;margin-bottom:32px}
+  .brand-dot{width:9px;height:9px;border-radius:50%;background:var(--coral);
+    box-shadow:var(--glow-coral);animation:beat 1.6s ease-in-out infinite}
+  .brand-name{font-family:'Orbitron','Segoe UI',sans-serif;font-weight:700;
+    font-size:.95rem;letter-spacing:.34em;text-indent:.34em;color:var(--ink)}
+  @keyframes beat{0%,100%{opacity:1}50%{opacity:.28}}
+
+  .strip-wrap{width:100%;margin-bottom:28px}
+  .strip{position:relative;display:flex;gap:7px;padding:15px 12px;overflow:hidden;
+    border:1px solid var(--line);border-radius:13px;
+    background:linear-gradient(180deg, rgba(255,255,255,.025), transparent)}
+  .strip i{flex:1 1 0;height:11px;border-radius:3px;background:var(--coral);opacity:.16;
+    transition:opacity .45s ease, background .45s ease, box-shadow .45s ease}
+  .strip::before{content:'';position:absolute;top:0;bottom:0;width:30%;left:-40%;
+    mix-blend-mode:screen;filter:blur(7px);
+    background:linear-gradient(90deg, transparent, var(--coral), transparent);
+    animation:sweep 2.4s linear infinite}
+  @keyframes sweep{0%{left:-42%}100%{left:112%}}
+
+  .chip{display:inline-flex;align-items:center;gap:9px;margin-bottom:24px;
+    font-family:'JetBrains Mono',ui-monospace,'Cascadia Code',monospace;
+    font-size:.66rem;font-weight:600;letter-spacing:.22em;text-transform:uppercase;
+    color:var(--coral);padding:5px 14px;border-radius:100px;
+    border:1px solid color-mix(in srgb, var(--coral) 38%, transparent)}
+  .chip b{width:7px;height:7px;border-radius:1px;background:var(--coral);
+    box-shadow:var(--glow-coral);animation:beat 1.6s ease-in-out infinite}
+
+  .headline{font-family:'Orbitron','Segoe UI',sans-serif;font-weight:700;
+    font-size:clamp(2.5rem,11.5vw,3.6rem);line-height:.92;letter-spacing:.015em;
+    text-transform:uppercase;color:var(--coral);text-shadow:0 0 26px rgba(255,94,94,.34);
+    margin-bottom:20px;animation:rise .6s cubic-bezier(.16,1,.3,1) forwards, flicker 5.5s 1.4s ease-in-out infinite}
+  .headline span{display:block;color:var(--ink);text-shadow:none}
+  @keyframes flicker{0%,93%,100%{opacity:1}94%{opacity:.55}96%{opacity:.85}97%{opacity:.4}}
+
+  .copy{max-width:35ch;color:var(--dim);font-size:.99rem;line-height:1.62;margin-bottom:32px}
+
+  .btn{position:relative;overflow:hidden;cursor:pointer;border:none;border-radius:11px;
+    padding:14px 36px;color:#04140a;background:var(--signal);
+    font-family:'JetBrains Mono',ui-monospace,monospace;font-weight:700;
+    font-size:.8rem;letter-spacing:.18em;text-transform:uppercase;
+    box-shadow:0 0 0 1px color-mix(in srgb, var(--signal) 55%, transparent), 0 10px 30px rgba(76,175,80,.28);
+    transition:transform .15s ease, box-shadow .25s ease, background .25s ease}
+  .btn:hover{background:var(--signal-hi);box-shadow:0 0 0 1px var(--signal), 0 14px 40px rgba(76,175,80,.42)}
+  .btn:active{transform:translateY(1px) scale(.99)}
+  .btn:focus-visible{outline:none;box-shadow:0 0 0 3px var(--bg), 0 0 0 5px var(--signal)}
+  .btn[disabled]{cursor:default;opacity:.7}
+  .btn::after{content:'';position:absolute;inset:0;transform:translateX(-130%);
+    background:linear-gradient(90deg, transparent, rgba(255,255,255,.38), transparent)}
+  .btn:not([disabled]):hover::after{animation:sheen .85s ease}
+  @keyframes sheen{to{transform:translateX(130%)}}
+
+  .telemetry{margin-top:18px;min-height:1.1em;
+    font-family:'JetBrains Mono',ui-monospace,monospace;
+    font-size:.7rem;letter-spacing:.12em;color:var(--mute)}
+  .foot{margin-top:34px;font-family:'JetBrains Mono',ui-monospace,monospace;
+    font-size:.6rem;letter-spacing:.3em;text-transform:uppercase;color:var(--mute);opacity:.65}
+
+  /* ── link-restored state ── */
+  body.online .strip i{opacity:1;background:var(--signal);box-shadow:var(--glow-signal)}
+  body.online .strip::before{display:none}
+  body.online .brand-dot,body.online .chip b{background:var(--signal);box-shadow:var(--glow-signal);animation:none}
+  body.online .chip{color:var(--signal);border-color:color-mix(in srgb, var(--signal) 45%, transparent)}
+  body.online .headline{animation:none}
+
+  @media (prefers-reduced-motion: reduce){
+    .panel>*,.headline{animation:none;opacity:1;transform:none}
+    .strip::before{display:none}.strip i{opacity:.5}
+    .brand-dot,.chip b{animation:none}.btn:hover::after{animation:none}
+  }
+</style>
+</head>
+<body>
+  <main class="panel" role="alert" aria-live="assertive">
+    <div class="brand"><span class="brand-dot" aria-hidden="true"></span><span class="brand-name">LED&nbsp;GRAB</span></div>
+    <div class="strip-wrap"><div class="strip" aria-hidden="true"><i></i><i></i><i></i><i></i><i></i><i></i><i></i><i></i><i></i><i></i><i></i><i></i><i></i><i></i></div></div>
+    <p class="chip"><b aria-hidden="true"></b><span id="chip-text">No Signal</span></p>
+    <h1 class="headline"><span>Signal</span>Lost</h1>
+    <p class="copy">Can&rsquo;t reach the LED&nbsp;Grab server. Make sure it&rsquo;s running and your device is on the same network.</p>
+    <button id="retry" class="btn" type="button"><span id="btn-label">Reconnect</span></button>
+    <p class="telemetry" id="telemetry" aria-live="polite">Listening for the server&hellip;</p>
+    <p class="foot">LED&nbsp;Grab &middot; Local Console</p>
+  </main>
+  <script>
+  (function(){
+    var RETRY = 3; // seconds between automatic probes
+    var attempts = 0, checking = false, done = false, timer = null;
+    var tel = document.getElementById('telemetry');
+    var chipText = document.getElementById('chip-text');
+    var btn = document.getElementById('retry');
+    var btnLabel = document.getElementById('btn-label');
+
+    function pad(n){ return n < 10 ? '0' + n : '' + n; }
+    function say(m){ if (tel) tel.textContent = m; }
+
+    function probe(){
+      if (checking || done) return;
+      checking = true; attempts++;
+      if (btn) btn.disabled = true;
+      if (btnLabel) btnLabel.textContent = 'Checking';
+      say('Probing for signal · attempt ' + pad(attempts));
+      // Any settled response (even 401/403) means the server is reachable.
+      // Cache-bust + no-store so a stale SW cache can't fake a recovery.
+      fetch('/?_swping=' + Date.now(), { method: 'HEAD', cache: 'no-store' })
+        .then(restored)
+        .catch(function(){
+          checking = false;
+          if (btn) btn.disabled = false;
+          if (btnLabel) btnLabel.textContent = 'Reconnect';
+          countdown(RETRY);
+        });
+    }
+
+    function restored(){
+      done = true;
+      document.body.classList.add('online');
+      if (chipText) chipText.textContent = 'Link Restored';
+      if (btnLabel) btnLabel.textContent = 'Reconnecting';
+      say('Signal acquired — reloading');
+      setTimeout(function(){ location.reload(); }, 750);
+    }
+
+    function countdown(s){
+      if (done) return;
+      if (s <= 0){ probe(); return; }
+      say('Retrying in ' + pad(s) + 's · attempt ' + pad(attempts + 1));
+      timer = setTimeout(function(){ countdown(s - 1); }, 1000);
+    }
+
+    function probeNow(){ if (timer){ clearTimeout(timer); timer = null; } probe(); }
+
+    if (btn) btn.addEventListener('click', probeNow);
+    window.addEventListener('online', probeNow);
+    document.addEventListener('visibilitychange', function(){ if (!document.hidden) probeNow(); });
+
+    probe();
+  })();
+  </script>
+</body>
+</html>`;
+
 // Install: pre-cache core shell
 self.addEventListener('install', (event) => {
     event.waitUntil(
@@ -66,17 +279,17 @@ self.addEventListener('fetch', (event) => {
         return;
     }
 
-    // Navigation: network-only (page requires auth, no useful offline fallback)
+    // Navigation: network-first with branded, self-healing offline fallback
     if (event.request.mode === 'navigate') {
         event.respondWith(
             fetch(event.request).catch(() =>
-                new Response(
-                    '<html><body style="font-family:system-ui;text-align:center;padding:60px 20px;background:#1a1a1a;color:#ccc">' +
-                    '<h2>LED Grab</h2><p>Cannot reach the server. Check that it is running and you are on the same network.</p>' +
-                    '<button onclick="location.reload()" style="margin-top:20px;padding:10px 24px;border-radius:8px;border:none;background:#4CAF50;color:#fff;font-size:1rem;cursor:pointer">Retry</button>' +
-                    '</body></html>',
-                    { status: 503, headers: { 'Content-Type': 'text/html' } }
-                )
+                new Response(OFFLINE_HTML, {
+                    status: 503,
+                    headers: {
+                        'Content-Type': 'text/html; charset=utf-8',
+                        'Cache-Control': 'no-store',
+                    },
+                })
             )
         );
         return;

server/src/ledgrab/templates/modals/add-device.html

@@ -84,6 +84,14 @@
                     <small class="input-hint" style="display:none" id="device-url-hint" data-i18n="device.url.hint">IP address or hostname of the device (e.g. http://192.168.1.100)</small>
                     <input type="text" id="device-url" data-i18n-placeholder="device.url.placeholder" placeholder="http://192.168.1.100" required>
                 </div>
+                <div class="form-group" id="device-mqtt-source-group" style="display: none;">
+                    <div class="label-row">
+                        <label for="device-mqtt-source" data-i18n="device.mqtt_source">MQTT Broker:</label>
+                        <button type="button" class="hint-toggle" onclick="toggleHint(this)" title="?">?</button>
+                    </div>
+                    <small class="input-hint" style="display:none" data-i18n="device.mqtt_source.hint">Which MQTT broker this device publishes to. Manage brokers under Integrations → MQTT Sources. Leave unset to use the first available broker.</small>
+                    <select id="device-mqtt-source"></select>
+                </div>
                 <div class="form-group" id="device-serial-port-group" style="display: none;">
                     <div class="label-row">
                         <label for="device-serial-port" id="device-serial-port-label" data-i18n="device.serial_port">Serial Port:</label>

server/src/ledgrab/templates/modals/device-settings.html

@@ -53,6 +53,15 @@
                             <select id="settings-serial-port"></select>
                         </div>
 
+                        <div class="form-group" id="settings-mqtt-source-group" style="display: none;">
+                            <div class="label-row">
+                                <label for="settings-mqtt-source" data-i18n="device.mqtt_source">MQTT Broker:</label>
+                                <button type="button" class="hint-toggle" onclick="toggleHint(this)" title="?">?</button>
+                            </div>
+                            <small class="input-hint" style="display:none" data-i18n="device.mqtt_source.hint">Which MQTT broker this device publishes to. Manage brokers under Integrations → MQTT Sources. Leave unset to use the first available broker.</small>
+                            <select id="settings-mqtt-source"></select>
+                        </div>
+
                         <div class="form-group" id="settings-ble-family-group" style="display: none;">
                             <div class="label-row">
                                 <label for="settings-ble-family" data-i18n="device.ble.family">Protocol Family:</label>

server/tests/api/routes/test_devices_routes.py

@@ -47,6 +47,13 @@ def output_target_store(_route_db):
     return OutputTargetStore(_route_db)
 
 
+@pytest.fixture
+def mqtt_source_store(_route_db):
+    from ledgrab.storage.mqtt_source_store import MQTTSourceStore
+
+    return MQTTSourceStore(_route_db)
+
+
 @pytest.fixture
 def processor_manager():
     """A mock ProcessorManager — avoids real hardware."""
@@ -60,7 +67,7 @@ def processor_manager():
 
 
 @pytest.fixture
-def client(device_store, output_target_store, processor_manager):
+def client(device_store, output_target_store, processor_manager, mqtt_source_store):
     app = _make_app()
 
     # Override auth to always pass
@@ -72,6 +79,7 @@ def client(device_store, output_target_store, processor_manager):
     app.dependency_overrides[deps.get_device_store] = lambda: device_store
     app.dependency_overrides[deps.get_output_target_store] = lambda: output_target_store
     app.dependency_overrides[deps.get_processor_manager] = lambda: processor_manager
+    app.dependency_overrides[deps.get_mqtt_store] = lambda: mqtt_source_store
 
     return TestClient(app, raise_server_exceptions=False)
 
@@ -428,6 +436,100 @@ class TestWLEDSchemeInference:
         assert device_store.get_device(existing.id).url == "http://10.0.0.5"
 
 
+class TestMqttSourceId:
+    """Regression coverage for the device ``mqtt_source_id`` field.
+
+    The store + ``device_config.MQTTConfig`` already carried the field, but
+    the API schema/route layer dropped it (DeviceCreate/Update/Response never
+    declared it, and the route never threaded it). These pin the create +
+    update round-trip and the referenced-source validation so it can't
+    silently regress.
+    """
+
+    @pytest.fixture
+    def _stub_mqtt_validate(self, monkeypatch):
+        async def fake_validate(self, url):  # noqa: ARG001 — provider self
+            return {"led_count": 60}
+
+        from ledgrab.core.devices.mqtt_provider import MQTTDeviceProvider
+
+        monkeypatch.setattr(MQTTDeviceProvider, "validate_device", fake_validate)
+        return fake_validate
+
+    def test_create_mqtt_device_persists_source_id(
+        self, client, device_store, mqtt_source_store, _stub_mqtt_validate
+    ):
+        src = mqtt_source_store.create_source(name="Broker A", broker_host="192.168.1.10")
+        resp = client.post(
+            "/api/v1/devices",
+            json={
+                "name": "Living Room MQTT",
+                "device_type": "mqtt",
+                "url": "mqtt://ledgrab/device/living-room",
+                "led_count": 60,
+                "mqtt_source_id": src.id,
+            },
+        )
+        assert resp.status_code == 201, resp.text
+        body = resp.json()
+        assert body["mqtt_source_id"] == src.id
+        assert device_store.get_device(body["id"]).mqtt_source_id == src.id
+
+    def test_create_mqtt_device_rejects_unknown_source(self, client, _stub_mqtt_validate):
+        resp = client.post(
+            "/api/v1/devices",
+            json={
+                "name": "Bad Broker Ref",
+                "device_type": "mqtt",
+                "url": "mqtt://ledgrab/device/x",
+                "led_count": 60,
+                "mqtt_source_id": "mqs_doesnotexist",
+            },
+        )
+        assert resp.status_code == 422, resp.text
+        assert "not found" in resp.json()["detail"]
+
+    def test_update_device_sets_mqtt_source_id(self, client, device_store, mqtt_source_store):
+        src = mqtt_source_store.create_source(name="Broker B", broker_host="10.0.0.2")
+        dev = device_store.create_device(
+            name="MQTT dev",
+            url="mqtt://ledgrab/device/a",
+            led_count=10,
+            device_type="mqtt",
+        )
+        resp = client.put(f"/api/v1/devices/{dev.id}", json={"mqtt_source_id": src.id})
+        assert resp.status_code == 200, resp.text
+        assert resp.json()["mqtt_source_id"] == src.id
+        assert device_store.get_device(dev.id).mqtt_source_id == src.id
+
+    def test_update_device_can_clear_mqtt_source(self, client, device_store, mqtt_source_store):
+        """An empty string unsets the broker (back to 'first available'). The
+        store's None-means-skip rule means '' is a real value that persists."""
+        src = mqtt_source_store.create_source(name="Broker C", broker_host="10.0.0.3")
+        dev = device_store.create_device(
+            name="MQTT dev3",
+            url="mqtt://ledgrab/device/c",
+            led_count=10,
+            device_type="mqtt",
+            mqtt_source_id=src.id,
+        )
+        resp = client.put(f"/api/v1/devices/{dev.id}", json={"mqtt_source_id": ""})
+        assert resp.status_code == 200, resp.text
+        assert resp.json()["mqtt_source_id"] == ""
+        assert device_store.get_device(dev.id).mqtt_source_id == ""
+
+    def test_update_device_rejects_unknown_mqtt_source(self, client, device_store):
+        dev = device_store.create_device(
+            name="MQTT dev2",
+            url="mqtt://ledgrab/device/b",
+            led_count=10,
+            device_type="mqtt",
+        )
+        resp = client.put(f"/api/v1/devices/{dev.id}", json={"mqtt_source_id": "mqs_nope"})
+        assert resp.status_code == 422, resp.text
+        assert "not found" in resp.json()["detail"]
+
+
 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

server/tests/api/routes/test_graph_routes.py

@@ -0,0 +1,143 @@
+"""Endpoint tests for the wiring-graph router (/api/v1/graph*).
+
+The graph router resolves stores via the ``dependencies`` getters *directly*
+(not FastAPI ``Depends``), so these tests populate the ``deps._deps`` registry
+rather than using ``app.dependency_overrides``. Auth stays real (conftest pins a
+test API key) so the rejection path is covered too.
+"""
+
+import pytest
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+
+from ledgrab.api import dependencies as deps
+from ledgrab.api.routes.graph import router
+
+_AUTH = {"Authorization": "Bearer test-api-key-12345"}
+
+
+class _Ent:
+    """Minimal stand-in for a storage model exposing ``to_dict``."""
+
+    def __init__(self, data: dict):
+        self._data = data
+
+    def to_dict(self) -> dict:
+        return self._data
+
+
+def _store(*entities: dict):
+    class _S:
+        def get_all(self):
+            return [_Ent(e) for e in entities]
+
+    return _S()
+
+
+@pytest.fixture
+def client(test_config, monkeypatch):
+    import ledgrab.config as config_mod
+
+    monkeypatch.setattr(config_mod, "config", test_config)
+
+    # Populate only the kinds under test; the rest resolve to RuntimeError and
+    # are gracefully treated as empty by the route's _gather_entities.
+    monkeypatch.setattr(
+        deps,
+        "_deps",
+        {
+            "device_store": _store({"id": "dev_1", "name": "Strip", "device_type": "wled"}),
+            "picture_source_store": _store({"id": "ps_1", "name": "Cap", "stream_type": "raw"}),
+            "color_strip_store": _store(
+                {
+                    "id": "css_1",
+                    "name": "CSS",
+                    "source_type": "picture",
+                    "picture_source_id": "ps_1",
+                }
+            ),
+            "output_target_store": _store(
+                {
+                    "id": "ot_1",
+                    "name": "TV",
+                    "target_type": "led",
+                    "device_id": "dev_1",
+                    "color_strip_source_id": "css_1",
+                }
+            ),
+        },
+    )
+
+    app = FastAPI()
+    app.include_router(router)
+    return TestClient(app, raise_server_exceptions=False)
+
+
+def test_schema_endpoint_returns_registry(client):
+    resp = client.get("/api/v1/graph/schema", headers=_AUTH)
+    assert resp.status_code == 200
+    data = resp.json()
+    assert "device" in data["kinds"]
+    assert any(
+        c["target_kind"] == "output_target" and c["field"] == "device_id"
+        for c in data["connections"]
+    )
+    # Bindable + nested flags must be carried through.
+    assert any(c["bindable"] and c["nested"] for c in data["connections"])
+
+
+def test_schema_endpoint_requires_auth(client):
+    assert client.get("/api/v1/graph/schema").status_code in (401, 403)
+
+
+def test_graph_endpoint_builds_topology(client):
+    data = client.get("/api/v1/graph", headers=_AUTH).json()
+    assert {n["id"] for n in data["nodes"]} == {"dev_1", "ps_1", "css_1", "ot_1"}
+    edges = {(e["from"], e["to"]) for e in data["edges"]}
+    assert ("dev_1", "ot_1") in edges
+    assert ("css_1", "ot_1") in edges
+    assert ("ps_1", "css_1") in edges
+    assert data["issues"]["broken_refs"] == []
+
+
+def test_dependents_endpoint(client):
+    data = client.get("/api/v1/graph/dependents/color_strip_source/css_1", headers=_AUTH).json()
+    assert data["dependents"] == [
+        {"id": "ot_1", "kind": "output_target", "name": "TV", "field": "color_strip_source_id"}
+    ]
+
+
+def test_dependents_endpoint_rejects_unknown_kind(client):
+    resp = client.get("/api/v1/graph/dependents/bogus/x", headers=_AUTH)
+    assert resp.status_code == 404
+
+
+def test_validate_connection_endpoint_accepts_valid(client):
+    resp = client.post(
+        "/api/v1/graph/validate-connection",
+        json={
+            "target_kind": "output_target",
+            "target_id": "ot_1",
+            "field": "color_strip_source_id",
+            "source_id": "css_1",
+        },
+        headers=_AUTH,
+    )
+    assert resp.status_code == 200
+    assert resp.json() == {"ok": True, "error": None}
+
+
+def test_validate_connection_endpoint_rejects_missing_source(client):
+    resp = client.post(
+        "/api/v1/graph/validate-connection",
+        json={
+            "target_kind": "output_target",
+            "target_id": "ot_1",
+            "field": "color_strip_source_id",
+            "source_id": "ghost",
+        },
+        headers=_AUTH,
+    )
+    data = resp.json()
+    assert data["ok"] is False
+    assert "not found" in data["error"]

server/tests/api/routes/test_snapshot_routes.py

@@ -0,0 +1,225 @@
+"""Tests for the aggregated /api/v1/snapshot endpoint.
+
+The snapshot collapses the integration's per-target/per-device poll fan-out
+into one response. These tests build a minimal app with the snapshot router and
+override the store/manager getters, mirroring tests/api/routes/test_devices_routes.py.
+Auth is left real (the conftest patches a test API key) so the rejection path is
+also covered. System metrics + health run for real — they read module-level
+providers and the patched config, no lifespan needed.
+"""
+
+import types
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+from fastapi import FastAPI, HTTPException
+from fastapi.testclient import TestClient
+
+from ledgrab.api import dependencies as deps
+from ledgrab.api.routes import devices as devices_mod
+from ledgrab.api.routes.devices import resolve_device_brightness
+from ledgrab.api.routes.snapshot import SNAPSHOT_SECTIONS, _resolve_sections, router
+from ledgrab.core.processing.processor_manager import ProcessorManager
+from ledgrab.core.update.update_service import UpdateService
+
+_AUTH = {"Authorization": "Bearer test-api-key-12345"}
+
+_TOP_LEVEL_KEYS = (
+    "targets",
+    "target_states",
+    "target_metrics",
+    "devices",
+    "device_brightness",
+    "css_sources",
+    "value_sources",
+    "scene_presets",
+    "sync_clocks",
+    "system",
+)
+
+
+@pytest.fixture
+def client(test_config, monkeypatch):
+    # Pin the global config (with its test API key) so auth is deterministic
+    # regardless of test ordering — other suites mutate the config singleton.
+    import ledgrab.config as config_mod
+
+    monkeypatch.setattr(config_mod, "config", test_config)
+
+    target_store = MagicMock()
+    target_store.get_all_targets.return_value = []
+    device_store = MagicMock()
+    device_store.get_all_devices.return_value = []
+    css_store = MagicMock()
+    css_store.get_all_sources.return_value = []
+    value_store = MagicMock()
+    value_store.get_all_sources.return_value = []
+    preset_store = MagicMock()
+    preset_store.get_all_presets.return_value = []
+    clock_store = MagicMock()
+    clock_store.get_all_clocks.return_value = []
+    clock_manager = MagicMock()
+
+    manager = MagicMock(spec=ProcessorManager)
+    manager.get_all_target_states.return_value = {}
+    manager.get_all_target_metrics.return_value = {}
+
+    update_service = MagicMock(spec=UpdateService)
+    update_service.get_status.return_value = {"has_update": False, "current_version": "test"}
+
+    app = FastAPI()
+    app.include_router(router)
+    app.dependency_overrides[deps.get_output_target_store] = lambda: target_store
+    app.dependency_overrides[deps.get_device_store] = lambda: device_store
+    app.dependency_overrides[deps.get_color_strip_store] = lambda: css_store
+    app.dependency_overrides[deps.get_value_source_store] = lambda: value_store
+    app.dependency_overrides[deps.get_scene_preset_store] = lambda: preset_store
+    app.dependency_overrides[deps.get_sync_clock_store] = lambda: clock_store
+    app.dependency_overrides[deps.get_sync_clock_manager] = lambda: clock_manager
+    app.dependency_overrides[deps.get_processor_manager] = lambda: manager
+    app.dependency_overrides[deps.get_update_service] = lambda: update_service
+
+    return TestClient(app, raise_server_exceptions=False)
+
+
+def test_snapshot_returns_all_sections(client):
+    resp = client.get("/api/v1/snapshot", headers=_AUTH)
+
+    assert resp.status_code == 200
+    data = resp.json()
+
+    for key in _TOP_LEVEL_KEYS:
+        assert key in data, f"snapshot missing top-level key: {key}"
+
+    for list_key in (
+        "targets",
+        "devices",
+        "css_sources",
+        "value_sources",
+        "scene_presets",
+        "sync_clocks",
+    ):
+        assert data[list_key] == []
+    for dict_key in ("target_states", "target_metrics", "device_brightness"):
+        assert data[dict_key] == {}
+
+
+def test_snapshot_system_block_has_health_version(client):
+    data = client.get("/api/v1/snapshot", headers=_AUTH).json()
+
+    system = data["system"]
+    assert {"performance", "health", "update"}.issubset(system)
+    # health drives the coordinator's version + boot-time derivation
+    assert system["health"]["version"]
+    assert "uptime_seconds" in system["health"]
+
+
+def test_snapshot_requires_auth(client):
+    resp = client.get("/api/v1/snapshot")
+
+    assert resp.status_code in (401, 403)
+
+
+def test_snapshot_include_filters_to_requested_sections(client):
+    resp = client.get("/api/v1/snapshot", params={"include": "devices,system"}, headers=_AUTH)
+
+    assert resp.status_code == 200
+    # Only requested sections are present — excluded ones are omitted entirely.
+    assert set(resp.json().keys()) == {"devices", "system"}
+
+
+def test_snapshot_include_rejects_unknown_section(client):
+    resp = client.get("/api/v1/snapshot", params={"include": "devices,bogus"}, headers=_AUTH)
+
+    assert resp.status_code == 422
+    assert "bogus" in resp.json()["detail"]
+
+
+# ---------------------------------------------------------------------------
+# _resolve_sections — query-param parsing edge cases
+# ---------------------------------------------------------------------------
+
+
+def test_resolve_sections_defaults_to_all_when_empty():
+    assert _resolve_sections(None) == frozenset(SNAPSHOT_SECTIONS)
+    assert _resolve_sections("") == frozenset(SNAPSHOT_SECTIONS)
+
+
+def test_resolve_sections_strips_whitespace_and_dedupes():
+    assert _resolve_sections("devices, system ,devices") == frozenset({"devices", "system"})
+
+
+def test_resolve_sections_ignores_empty_segments():
+    assert _resolve_sections("devices,,system,") == frozenset({"devices", "system"})
+
+
+def test_resolve_sections_is_case_sensitive():
+    with pytest.raises(HTTPException) as exc:
+        _resolve_sections("Devices")
+    assert exc.value.status_code == 422
+
+
+# ---------------------------------------------------------------------------
+# resolve_device_brightness — cached / cold-fetch / graceful-degrade paths
+# ---------------------------------------------------------------------------
+
+
+def _fake_device(**kw):
+    return types.SimpleNamespace(
+        id=kw.get("id", "d1"),
+        device_type=kw.get("device_type", "wled"),
+        url=kw.get("url", "http://x"),
+        software_brightness=kw.get("software_brightness", 42),
+    )
+
+
+async def test_brightness_none_without_capability(monkeypatch):
+    monkeypatch.setattr(devices_mod, "get_device_capabilities", lambda _dt: set())
+    manager = MagicMock()
+
+    assert await resolve_device_brightness(_fake_device(), manager) is None
+    manager.find_device_state.assert_not_called()
+
+
+async def test_brightness_returns_cached(monkeypatch):
+    monkeypatch.setattr(devices_mod, "get_device_capabilities", lambda _dt: {"brightness_control"})
+    manager = MagicMock()
+    manager.find_device_state.return_value = types.SimpleNamespace(hardware_brightness=128)
+
+    assert await resolve_device_brightness(_fake_device(), manager) == 128
+
+
+async def test_brightness_active_fetch_and_caches_on_cold_cache(monkeypatch):
+    monkeypatch.setattr(devices_mod, "get_device_capabilities", lambda _dt: {"brightness_control"})
+    provider = MagicMock()
+    provider.get_brightness = AsyncMock(return_value=200)
+    monkeypatch.setattr(devices_mod, "get_provider", lambda _dt: provider)
+    ds = types.SimpleNamespace(hardware_brightness=None)
+    manager = MagicMock()
+    manager.find_device_state.return_value = ds
+
+    assert await resolve_device_brightness(_fake_device(), manager) == 200
+    assert ds.hardware_brightness == 200  # cached so the next poll is I/O-free
+
+
+async def test_brightness_degrades_to_none_on_provider_error(monkeypatch):
+    monkeypatch.setattr(devices_mod, "get_device_capabilities", lambda _dt: {"brightness_control"})
+    provider = MagicMock()
+    provider.get_brightness = AsyncMock(side_effect=OSError("unreachable"))
+    monkeypatch.setattr(devices_mod, "get_provider", lambda _dt: provider)
+    manager = MagicMock()
+    manager.find_device_state.return_value = types.SimpleNamespace(hardware_brightness=None)
+
+    # A single unreachable device must not raise — it degrades to None.
+    assert await resolve_device_brightness(_fake_device(), manager) is None
+
+
+async def test_brightness_falls_back_to_software_when_unsupported(monkeypatch):
+    monkeypatch.setattr(devices_mod, "get_device_capabilities", lambda _dt: {"brightness_control"})
+    provider = MagicMock()
+    provider.get_brightness = AsyncMock(side_effect=NotImplementedError)
+    monkeypatch.setattr(devices_mod, "get_provider", lambda _dt: provider)
+    manager = MagicMock()
+    manager.find_device_state.return_value = types.SimpleNamespace(hardware_brightness=None)
+
+    assert await resolve_device_brightness(_fake_device(software_brightness=42), manager) == 42

server/tests/api/test_graph_schema.py

@@ -0,0 +1,266 @@
+"""Unit tests for the pure wiring-graph engine (ledgrab.api.graph_schema).
+
+These exercise reference extraction, topology building, dependents, cycle and
+dangling-reference detection without booting the app or any store.
+"""
+
+from ledgrab.api.graph_schema import (
+    CONNECTION_SCHEMA,
+    ENTITY_KINDS,
+    build_topology,
+    detect_cycles,
+    extract_refs,
+    find_dependents,
+    schema_for_kind,
+    validate_connection,
+    would_create_cycle,
+)
+
+
+# ── extract_refs ────────────────────────────────────────────────────────────
+
+
+def test_extract_refs_top_level():
+    assert extract_refs({"device_id": "dev_1"}, "device_id") == ["dev_1"]
+
+
+def test_extract_refs_empty_and_missing_are_dropped():
+    assert extract_refs({"device_id": ""}, "device_id") == []
+    assert extract_refs({}, "device_id") == []
+    assert extract_refs({"device_id": None}, "device_id") == []
+
+
+def test_extract_refs_bindable_bound_vs_unbound():
+    # Bound bindable serializes as a dict.
+    assert extract_refs(
+        {"brightness": {"value": 1.0, "source_id": "vs_1"}}, "brightness.source_id"
+    ) == ["vs_1"]
+    # Unbound bindable serializes as a plain number → no reference.
+    assert extract_refs({"brightness": 0.5}, "brightness.source_id") == []
+    # Bound-but-empty source_id → no reference.
+    assert (
+        extract_refs({"brightness": {"value": 1.0, "source_id": ""}}, "brightness.source_id") == []
+    )
+
+
+def test_extract_refs_list_field():
+    entity = {"layers": [{"source_id": "a"}, {"source_id": ""}, {"other": "x"}]}
+    assert extract_refs(entity, "layers[].source_id") == ["a"]
+
+
+def test_extract_refs_deep_object_then_list():
+    entity = {"calibration": {"lines": [{"picture_source_id": "p1"}, {"picture_source_id": "p2"}]}}
+    assert extract_refs(entity, "calibration.lines[].picture_source_id") == ["p1", "p2"]
+
+
+def test_extract_refs_nested_object_none_is_safe():
+    assert extract_refs({"settings": None}, "settings.pattern_template_id") == []
+    assert extract_refs(
+        {"settings": {"pattern_template_id": "pt_1"}}, "settings.pattern_template_id"
+    ) == ["pt_1"]
+
+
+# ── registry consistency ─────────────────────────────────────────────────────
+
+
+def test_registry_kinds_are_known():
+    for cf in CONNECTION_SCHEMA:
+        assert cf.target_kind in ENTITY_KINDS, cf.target_kind
+        assert cf.source_kind in ENTITY_KINDS, cf.source_kind
+
+
+def test_registry_has_no_duplicate_target_field_pairs():
+    pairs = [(cf.target_kind, cf.field) for cf in CONNECTION_SCHEMA]
+    assert len(pairs) == len(set(pairs)), "duplicate (target_kind, field) in CONNECTION_SCHEMA"
+
+
+def test_schema_for_kind_filters_by_referrer():
+    fields = {cf.field for cf in schema_for_kind("automation")}
+    assert fields == {"scene_preset_id", "deactivation_scene_preset_id"}
+
+
+# ── build_topology ───────────────────────────────────────────────────────────
+
+
+def _sample_entities():
+    return {
+        "device": [{"id": "dev_1", "name": "Strip", "device_type": "wled"}],
+        "picture_source": [{"id": "ps_1", "name": "Cap", "stream_type": "raw"}],
+        "color_strip_source": [
+            {"id": "css_1", "name": "CSS", "source_type": "picture", "picture_source_id": "ps_1"}
+        ],
+        "output_target": [
+            {
+                "id": "ot_1",
+                "name": "TV",
+                "target_type": "led",
+                "device_id": "dev_1",
+                "color_strip_source_id": "css_1",
+            }
+        ],
+    }
+
+
+def test_build_topology_nodes_and_edges():
+    topo = build_topology(_sample_entities())
+
+    assert {n["id"] for n in topo["nodes"]} == {"dev_1", "ps_1", "css_1", "ot_1"}
+    edge_set = {(e["from"], e["to"], e["field"]) for e in topo["edges"]}
+    assert ("ps_1", "css_1", "picture_source_id") in edge_set
+    assert ("dev_1", "ot_1", "device_id") in edge_set
+    assert ("css_1", "ot_1", "color_strip_source_id") in edge_set
+    assert topo["issues"]["orphans"] == []
+    assert topo["issues"]["broken_refs"] == []
+    assert topo["issues"]["cycles"] == []
+
+
+def test_build_topology_flags_orphan_and_broken_ref():
+    entities = _sample_entities()
+    entities["sync_clock"] = [{"id": "clk_1", "name": "Lonely"}]  # no edges → orphan
+    entities["color_strip_source"][0]["audio_source_id"] = "ghost"  # dangling
+
+    topo = build_topology(entities)
+
+    assert "clk_1" in topo["issues"]["orphans"]
+    broken = topo["issues"]["broken_refs"]
+    assert {"ref": "ghost", "by": "css_1", "field": "audio_source_id"} in broken
+    # The dangling ref must NOT appear as a real edge.
+    assert all(e["from"] != "ghost" for e in topo["edges"])
+
+
+def test_build_topology_detects_cycle():
+    entities = {
+        "value_source": [
+            {"id": "vs_1", "name": "A", "source_type": "static", "value_source_id": "vs_2"},
+            {"id": "vs_2", "name": "B", "source_type": "static", "value_source_id": "vs_1"},
+        ]
+    }
+    topo = build_topology(entities)
+    assert set(topo["issues"]["cycles"]) == {"vs_1", "vs_2"}
+
+
+# ── detect_cycles ────────────────────────────────────────────────────────────
+
+
+def test_detect_cycles_no_false_positive_on_diamond():
+    # a→b, a→c, b→d, c→d  (DAG)
+    edges = [
+        {"from": "a", "to": "b"},
+        {"from": "a", "to": "c"},
+        {"from": "b", "to": "d"},
+        {"from": "c", "to": "d"},
+    ]
+    assert detect_cycles(edges) == set()
+
+
+def test_detect_cycles_marks_only_cycle_members():
+    # x→a→b→a  (a,b in cycle; x is not)
+    edges = [
+        {"from": "x", "to": "a"},
+        {"from": "a", "to": "b"},
+        {"from": "b", "to": "a"},
+    ]
+    assert detect_cycles(edges) == {"a", "b"}
+
+
+# ── would_create_cycle ───────────────────────────────────────────────────────
+
+
+def test_would_create_cycle_detects_back_edge_and_self():
+    edges = [{"from": "a", "to": "b"}]  # b depends on a (a→b)
+    # Wiring a to consume b (edge b→a) closes the a→b→a loop.
+    assert would_create_cycle(edges, source_id="b", target_id="a") is True
+    # Wiring an unrelated pair is fine.
+    assert would_create_cycle(edges, source_id="a", target_id="c") is False
+    # Self-reference is always a cycle.
+    assert would_create_cycle(edges, source_id="z", target_id="z") is True
+
+
+# ── find_dependents ──────────────────────────────────────────────────────────
+
+
+def test_find_dependents_returns_referrers():
+    deps = find_dependents(_sample_entities(), "color_strip_source", "css_1")
+    assert deps == [
+        {"id": "ot_1", "kind": "output_target", "name": "TV", "field": "color_strip_source_id"}
+    ]
+
+
+def test_find_dependents_empty_when_unreferenced():
+    assert find_dependents(_sample_entities(), "color_strip_source", "css_unused") == []
+
+
+# ── validate_connection ──────────────────────────────────────────────────────
+
+
+def test_validate_connection_accepts_valid_edit():
+    ok, err = validate_connection(_sample_entities(), "output_target", "ot_1", "device_id", "dev_1")
+    assert ok is True
+    assert err is None
+
+
+def test_validate_connection_detach_always_ok():
+    ok, err = validate_connection(_sample_entities(), "output_target", "ot_1", "device_id", "")
+    assert ok is True and err is None
+
+
+def test_validate_connection_rejects_unknown_field():
+    ok, err = validate_connection(_sample_entities(), "output_target", "ot_1", "nope_id", "dev_1")
+    assert ok is False
+    assert "Unknown connection field" in err
+
+
+def test_validate_connection_rejects_missing_source():
+    ok, err = validate_connection(_sample_entities(), "output_target", "ot_1", "device_id", "ghost")
+    assert ok is False
+    assert "not found" in err
+
+
+def test_validate_connection_accepts_bindable_single_field():
+    # Single-level bindable slots (e.g. brightness) ARE editable — only list
+    # fields are rejected.
+    entities = {
+        "color_strip_source": [
+            {"id": "css_1", "name": "X", "source_type": "effect", "brightness": 0.5}
+        ],
+        "value_source": [{"id": "vs_1", "name": "V", "source_type": "static"}],
+    }
+    ok, err = validate_connection(
+        entities, "color_strip_source", "css_1", "brightness.source_id", "vs_1"
+    )
+    assert ok is True
+    assert err is None
+
+
+def test_validate_connection_rejects_list_field():
+    # List slots can't be cycle-checked without an element index → rejected.
+    entities = {
+        "color_strip_source": [
+            {
+                "id": "css_1",
+                "name": "X",
+                "source_type": "composite",
+                "layers": [{"source_id": "css_2"}],
+            },
+            {"id": "css_2", "name": "Y", "source_type": "picture"},
+        ]
+    }
+    ok, err = validate_connection(
+        entities, "color_strip_source", "css_1", "layers[].source_id", "css_2"
+    )
+    assert ok is False
+    assert "List connection" in err
+
+
+def test_validate_connection_rejects_cycle():
+    entities = {
+        "value_source": [
+            {"id": "vs_1", "name": "A", "source_type": "static", "value_source_id": ""},
+            {"id": "vs_2", "name": "B", "source_type": "static", "value_source_id": "vs_1"},
+        ]
+    }
+    # vs_2 already depends on vs_1 (edge vs_1→vs_2). Wiring vs_1 to consume vs_2
+    # would close the loop.
+    ok, err = validate_connection(entities, "value_source", "vs_1", "value_source_id", "vs_2")
+    assert ok is False
+    assert "cycle" in err.lower()

server/tests/test_access_log.py

@@ -0,0 +1,78 @@
+"""Tests for the request access-log middleware (token-label attribution).
+
+The middleware emits one structured ``http_request`` line per request, tagged
+with the friendly label of the API token used (from ``auth.api_keys``) so
+traffic can be attributed to a specific client. These tests capture the
+``main.logger`` calls to assert the label is recorded and that no-auth
+endpoints fall back to ``"unauthenticated"``.
+"""
+
+import pytest
+
+
+@pytest.fixture
+def client_and_logs(authenticated_client, monkeypatch):
+    """authenticated_client plus a captured list of (event, kwargs) log calls."""
+    import ledgrab.main as main_mod
+
+    calls: list[tuple[str, dict]] = []
+
+    class _FakeLogger:
+        def info(self, event, **kw):
+            calls.append((event, kw))
+
+        # main.logger is shared; keep other levels as harmless no-ops.
+        def debug(self, *a, **k):
+            pass
+
+        def warning(self, *a, **k):
+            pass
+
+        def error(self, *a, **k):
+            pass
+
+    monkeypatch.setattr(main_mod, "logger", _FakeLogger())
+    return authenticated_client, calls
+
+
+def _http_request_logs(calls):
+    return [kw for event, kw in calls if event == "http_request"]
+
+
+def test_access_log_records_token_label_for_authed_request(client_and_logs):
+    client, calls = client_and_logs
+
+    # /openapi.json requires auth but needs no initialized store, so it returns
+    # 200 even without app lifespan — and exercises the auth → label path.
+    resp = client.get("/openapi.json")
+    assert resp.status_code == 200
+
+    logs = _http_request_logs(calls)
+    assert logs, "no http_request access log emitted"
+    entry = logs[-1]
+    assert entry["method"] == "GET"
+    assert entry["path"] == "/openapi.json"
+    assert entry["status"] == 200
+    assert entry["token"] == "test"  # label of the configured test API key
+    assert "duration_ms" in entry
+
+
+def test_access_log_marks_unauthenticated_for_no_auth_endpoint(client_and_logs):
+    client, calls = client_and_logs
+
+    # /health has no auth dependency, so no label is set on request.state.
+    resp = client.get("/health")
+    assert resp.status_code == 200
+
+    logs = _http_request_logs(calls)
+    assert logs
+    assert logs[-1]["token"] == "unauthenticated"
+
+
+def test_access_log_never_contains_the_token_secret(client_and_logs):
+    client, calls = client_and_logs
+
+    client.get("/openapi.json")
+
+    for _event, kw in calls:
+        assert "test-api-key-12345" not in repr(kw), "token secret leaked into logs"

server/tests/test_main_entrypoint.py

@@ -12,7 +12,12 @@ import signal
 import threading
 from types import SimpleNamespace
 
-from ledgrab.__main__ import _install_signal_handlers, _request_shutdown
+from ledgrab.__main__ import (
+    _build_server,
+    _install_signal_handlers,
+    _request_shutdown,
+)
+from ledgrab.shutdown_state import GRACEFUL_SHUTDOWN_TIMEOUT
 
 
 def test_request_shutdown_sets_should_exit() -> None:
@@ -21,6 +26,33 @@ def test_request_shutdown_sets_should_exit() -> None:
     assert server.should_exit is True
 
 
+def test_build_server_bounds_graceful_shutdown() -> None:
+    """uvicorn defaults ``timeout_graceful_shutdown`` to ``None`` (wait
+    forever). A lingering events WebSocket then blocks ``Server.shutdown()``
+    from ever reaching the lifespan shutdown, so LED targets are never
+    stopped and the process can't exit. The bound is what guarantees the
+    lifespan shutdown runs — assert we never regress to the unbounded default.
+    """
+    fake_config = SimpleNamespace(
+        server=SimpleNamespace(host="127.0.0.1", port=8080, log_level="INFO")
+    )
+
+    server = _build_server(fake_config)  # type: ignore[arg-type]
+
+    assert server.config.timeout_graceful_shutdown == GRACEFUL_SHUTDOWN_TIMEOUT
+    assert server.config.timeout_graceful_shutdown is not None
+    assert server.config.timeout_graceful_shutdown > 0
+
+
+def test_graceful_shutdown_timeout_fits_os_budget() -> None:
+    """The graceful wait runs BEFORE the lifespan's own ~16 s shutdown budget,
+    and OS shutdown gives the whole process only ~20 s before a force-kill.
+    Keep the bound small so target restore + DB checkpoint still fit.
+    """
+    assert isinstance(GRACEFUL_SHUTDOWN_TIMEOUT, int)
+    assert 0 < GRACEFUL_SHUTDOWN_TIMEOUT <= 5
+
+
 def test_install_signal_handlers_installs_for_known_signals() -> None:
     """Tray path runs uvicorn on a background thread, so our handlers must
     actually survive — verify each catchable signal is replaced.