diff --git a/CLAUDE.md b/CLAUDE.md
index 9d3f159..4f9b4e9 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -90,6 +90,22 @@ None of these were discoverable locally — there's no npm here (see "Local-only
 - **`createAppConfig` prefixes every entry name with the app id**, so the entry `personal-settings` is emitted as `js/workflow_deck_automation-personal-settings.mjs` and `css/workflow_deck_automation-personal-settings.css`. `Util::addScript()`/`addStyle()` take that *full on-disk basename* (minus extension), not the bare entry name — `lib/Settings/Personal.php` therefore passes `Application::APP_ID . '-personal-settings'`. Getting this wrong produces a **silently blank settings page**: the template's empty mount `<div>` renders fine, and the only symptom is `Could not find resource workflow_deck_automation/js/….js to load` (`jsresourceloader`) plus a matching `Could not find resource file "/apps/workflow_deck_automation/css/….css"` in `nextcloud.log`. If you rename the entry in `vite.config.js`, rename it in `Personal.php` too.
 - **The bulk of the CSS lives in a hashed `*.chunk.css`**, loaded at runtime by the `.mjs` bundle (`cssCodeSplit: true`). The `css/workflow_deck_automation-personal-settings.css` that `addStyle()` points at is the ~100-byte stub produced by `createEmptyCSSEntryPoints: true`. A near-empty entry CSS file is expected — don't "fix" it by turning off code splitting.
 
+## `@nextcloud/vue` 9 component API (Vue 3) — the v8 idioms silently do nothing
+
+This app is on `@nextcloud/vue` ^9 / Vue 3. The v8 (Vue 2) prop spellings that most Nextcloud app code online still uses either fail silently or, worse, land as stray DOM attributes instead of erroring:
+
+- **No `.sync`.** Vue 3 removed it. `NcTextField` and `NcCheckboxRadioSwitch` both bind through `modelValue`/`update:modelValue`, so it's `v-model="x"` — `:value.sync="x"` / `:checked.sync="x"` leave the bound state permanently at its initial value. That's how `form.title` stayed `''` and every save died on "Bitte einen Titel angeben."
+- **`NcSelect`'s `label` prop is the *option display key*, not a caption** (it's vue-select's). Passing `label="Board"` makes it read `option.Board` on every option and render `undefined` for all of them. The visible caption prop is `input-label`.
+- **`NcButton`: `variant` is the style, `type` is the native button type**, and `native-type` no longer exists (v8's `type="primary"` + `native-type="submit"` → v9's `variant="primary"` + `type="submit"`). A leftover `type="primary"` renders `<button type="primary">`, which HTML treats as the invalid-value default `submit` — so a *cancel* button silently submits the form.
+- `NcSelect`'s `reduce` is not declared on `NcSelect` itself; it reaches vue-select through attribute fallthrough (NcSelect's root element *is* the `VueSelect` component and it doesn't set `inheritAttrs: false`). It works, but it's fallthrough, not a documented prop.
+- `NcNoteCard`'s prop is still `type` (`success|info|warning|error`) — not everything was renamed to `variant`.
+
+## Deck entities are "relational": getters don't return the uid string
+
+Deck's `RelationalEntity` swaps resolved relations for an `OCA\Deck\Db\RelationalObject` once an entity is enriched. So on an enriched board/card, `$acl->getParticipant()`, `$board->getOwner()` and a card assignment's participant return a `RelationalObject` (wrapping `OCA\Deck\Db\User`/`Group`/`Circle`), **not** a uid — the uid is its `getPrimaryKey()`. Probing for `getUID()` on the returned object finds nothing and yields `null`, which is how the settings UI's user dropdown came up empty *and* why the runner's assigned-user filter could never match. `DeckIntegrationService::unwrapUid()` handles both shapes (bare string and `RelationalObject`); route any new participant/owner field through it.
+
+Two more Deck facts that bit us in the same pass: a board's ACL does **not** contain its owner (a private board has an empty ACL, so participants must be seeded with `$board->getOwner()`), and ACL entries can be groups (`type === 1`) whose members have to be expanded via `IGroupManager`. `BoardService::getUserBoards()` merges own/group/circle boards and can return the same board twice, and it includes archived and trashed boards — `listBoardsForCurrentUser()` dedupes by id and drops those.
+
 ## Local-only notes
 
 `CLAUDE.local.md` (gitignored) carries session-specific environment notes (e.g. "no PHP/npm available locally"). Check it at the start of work in this repo — it's not duplicated here since it can change independently of the committed guidance.
diff --git a/lib/Service/DeckIntegrationService.php b/lib/Service/DeckIntegrationService.php
index 2b82cde..9391814 100644
--- a/lib/Service/DeckIntegrationService.php
+++ b/lib/Service/DeckIntegrationService.php
@@ -10,7 +10,9 @@ use OCA\Deck\Service\BoardService;
 use OCA\Deck\Service\CardService;
 use OCA\Deck\Service\StackService;
 use OCP\App\IAppManager;
+use OCP\IGroupManager;
 use OCP\IUser;
+use OCP\IUserManager;
 use OCP\Server;
 use Psr\Log\LoggerInterface;
 use Throwable;
@@ -28,8 +30,18 @@ use Throwable;
 class DeckIntegrationService {
 	private const DECK_APP_ID = 'deck';
 
+	/**
+	 * Deck's Acl::PERMISSION_TYPE_* values, inlined so this class keeps
+	 * working (degrading to "treat it as a user") if Deck ever moves or
+	 * renames the constants.
+	 */
+	private const ACL_TYPE_USER = 0;
+	private const ACL_TYPE_GROUP = 1;
+
 	public function __construct(
 		private IAppManager $appManager,
+		private IUserManager $userManager,
+		private IGroupManager $groupManager,
 		private LoggerInterface $logger,
 	) {
 	}
@@ -51,10 +63,30 @@ class DeckIntegrationService {
 			return $this->resolve(BoardService::class)->getUserBoards();
 		}, []);
 
-		return array_map(
-			static fn ($board) => ['id' => $board->getId(), 'title' => $board->getTitle()],
-			$boards,
-		);
+		// Deck merges own/group/circle boards, so the same board can come
+		// back more than once; and boards in the trash or archived ones are
+		// no useful automation target. Keyed by id => deduplicated.
+		$result = [];
+		foreach ($boards as $board) {
+			$id = (int)$board->getId();
+			if (isset($result[$id]) || $this->isBoardHidden($board)) {
+				continue;
+			}
+			$title = $board->getTitle();
+			$result[$id] = [
+				'id' => $id,
+				'title' => (is_string($title) && $title !== '') ? $title : ('#' . $id),
+			];
+		}
+
+		return array_values($result);
+	}
+
+	private function isBoardHidden(mixed $board): bool {
+		if (method_exists($board, 'getDeletedAt') && (int)$board->getDeletedAt() > 0) {
+			return true;
+		}
+		return method_exists($board, 'getArchived') && $board->getArchived() === true;
 	}
 
 	/**
@@ -87,25 +119,65 @@ class DeckIntegrationService {
 	}
 
 	/**
+	 * Everyone who can hold a card on this board: the board owner (who is
+	 * *not* part of the ACL — a private board has an empty ACL) plus every
+	 * ACL entry, with group shares expanded to their members.
+	 *
 	 * @return array<int, array{uid: string, displayName: string}>
 	 */
 	public function listParticipants(int $boardId): array {
-		$acl = $this->call(function () use ($boardId) {
+		$uids = $this->call(function () use ($boardId) {
 			$board = $this->resolve(BoardService::class)->find($boardId, true);
-			return $board->getAcl() ?? [];
+
+			$uids = [];
+			$owner = $this->unwrapUid($board->getOwner());
+			if ($owner !== null) {
+				$uids[] = $owner;
+			}
+
+			foreach ($board->getAcl() ?? [] as $entry) {
+				$principal = $this->extractParticipantUid($entry);
+				if ($principal === null) {
+					continue;
+				}
+				$type = method_exists($entry, 'getType') ? (int)$entry->getType() : self::ACL_TYPE_USER;
+				if ($type === self::ACL_TYPE_GROUP) {
+					array_push($uids, ...$this->groupMemberUids($principal));
+				} elseif ($type === self::ACL_TYPE_USER) {
+					$uids[] = $principal;
+				}
+				// Circles and federated shares are skipped: their members
+				// cannot be resolved to plain uids here.
+			}
+
+			return $uids;
 		}, []);
 
 		$participants = [];
-		foreach ($acl as $entry) {
-			$uid = $this->extractParticipantUid($entry);
-			if ($uid !== null && !isset($participants[$uid])) {
-				$participants[$uid] = ['uid' => $uid, 'displayName' => $uid];
+		foreach ($uids as $uid) {
+			if (isset($participants[$uid])) {
+				continue;
 			}
+			$participants[$uid] = [
+				'uid' => $uid,
+				'displayName' => $this->userManager->get($uid)?->getDisplayName() ?? $uid,
+			];
 		}
 
 		return array_values($participants);
 	}
 
+	/**
+	 * @return string[]
+	 */
+	private function groupMemberUids(string $groupId): array {
+		$group = $this->groupManager->get($groupId);
+		if ($group === null) {
+			return [];
+		}
+		return array_map(static fn (IUser $user) => $user->getUID(), $group->getUsers());
+	}
+
 	/**
 	 * Cards in the given stack that are neither archived nor marked done,
 	 * enriched so getAssignedUsers()/getLabels() are populated.
@@ -208,20 +280,57 @@ class DeckIntegrationService {
 	 * on one fixed method signature.
 	 */
 	private function extractParticipantUid(mixed $entry): ?string {
-		if (is_string($entry)) {
-			return $entry;
+		$uid = $this->unwrapUid($entry);
+		if ($uid !== null) {
+			return $uid;
 		}
 		if (!is_object($entry)) {
 			return null;
 		}
 		foreach (['getParticipant', 'getUid', 'getParticipantUid', 'getUserId'] as $method) {
 			if (method_exists($entry, $method)) {
-				$value = $entry->$method();
-				if (is_string($value) && $value !== '') {
-					return $value;
+				$uid = $this->unwrapUid($entry->$method());
+				if ($uid !== null) {
+					return $uid;
 				}
-				if (is_object($value) && method_exists($value, 'getUID')) {
-					return $value->getUID();
+			}
+		}
+		return null;
+	}
+
+	/**
+	 * Turns whatever Deck hands out for a "participant"/"owner" field into
+	 * a plain uid.
+	 *
+	 * Enriched Deck entities do *not* return the raw uid string: their
+	 * RelationalEntity base swaps resolved relations for a
+	 * OCA\Deck\Db\RelationalObject wrapping a User/Group object, and its
+	 * primary key is the uid we want. Unenriched entities still return the
+	 * bare string, so both shapes are handled.
+	 */
+	private function unwrapUid(mixed $value): ?string {
+		if (is_string($value)) {
+			return $value !== '' ? $value : null;
+		}
+		if (!is_object($value)) {
+			return null;
+		}
+		foreach (['getPrimaryKey', 'getUID', 'getUid', 'getId'] as $method) {
+			if (method_exists($value, $method)) {
+				$inner = $value->$method();
+				if (is_string($inner) && $inner !== '') {
+					return $inner;
+				}
+			}
+		}
+		if (method_exists($value, 'getObject')) {
+			$inner = $value->getObject();
+			foreach (['getUID', 'getUid', 'getId'] as $method) {
+				if (is_object($inner) && method_exists($inner, $method)) {
+					$uid = $inner->$method();
+					if (is_string($uid) && $uid !== '') {
+						return $uid;
+					}
 				}
 			}
 		}
diff --git a/src/PersonalSettings.vue b/src/PersonalSettings.vue
index ca0f413..e9a7c94 100644
--- a/src/PersonalSettings.vue
+++ b/src/PersonalSettings.vue
@@ -39,10 +39,10 @@
 						<td>{{ workflow.notifyEmail ? 'Ja' : 'Nein' }}</td>
 						<td>{{ workflow.enabled ? 'Ja' : 'Nein' }}</td>
 						<td class="wfda-actions">
-							<NcButton type="tertiary" @click="editWorkflow(workflow)">
+							<NcButton variant="tertiary" @click="editWorkflow(workflow)">
 								Bearbeiten
 							</NcButton>
-							<NcButton type="tertiary" @click="removeWorkflow(workflow)">
+							<NcButton variant="tertiary" @click="removeWorkflow(workflow)">
 								Löschen
 							</NcButton>
 						</td>
@@ -53,19 +53,19 @@
 				Noch keine Workflows angelegt.
 			</p>
 
-			<NcButton v-if="!showForm" type="primary" class="wfda-add-button" @click="startCreate">
+			<NcButton v-if="!showForm" variant="primary" class="wfda-add-button" @click="startCreate">
 				Workflow hinzufügen
 			</NcButton>
 
 			<form v-if="showForm" class="wfda-form" @submit.prevent="save">
 				<NcTextField
-					:value.sync="form.title"
+					v-model="form.title"
 					label="Titel"
 					required />
 
 				<NcSelect
 					v-model="form.boardId"
-					label="Board"
+					input-label="Board"
 					:options="boardOptions"
 					:reduce="option => option.value"
 					placeholder="Board wählen"
@@ -73,7 +73,7 @@
 
 				<NcSelect
 					v-model="form.sourceStackId"
-					label="Quell-Stapel"
+					input-label="Quell-Stapel"
 					:options="stackOptions"
 					:reduce="option => option.value"
 					:disabled="!form.boardId"
@@ -81,7 +81,7 @@
 
 				<NcSelect
 					v-model="form.targetStackId"
-					label="Ziel-Stapel"
+					input-label="Ziel-Stapel"
 					:options="stackOptions"
 					:reduce="option => option.value"
 					:disabled="!form.boardId"
@@ -89,7 +89,7 @@
 
 				<NcSelect
 					v-model="form.filterUserIds"
-					label="Nur für zugewiesene Benutzer (optional)"
+					input-label="Nur für zugewiesene Benutzer (optional)"
 					:options="participantOptions"
 					:reduce="option => option.value"
 					:disabled="!form.boardId"
@@ -98,18 +98,18 @@
 
 				<NcSelect
 					v-model="form.filterLabelIds"
-					label="Nur mit Label (optional)"
+					input-label="Nur mit Label (optional)"
 					:options="labelOptions"
 					:reduce="option => option.value"
 					:disabled="!form.boardId"
 					multiple
 					placeholder="Alle Labels" />
 
-				<NcCheckboxRadioSwitch :checked.sync="form.notifyEmail">
+				<NcCheckboxRadioSwitch v-model="form.notifyEmail">
 					Benachrichtigungs-E-Mail an mich senden
 				</NcCheckboxRadioSwitch>
 
-				<NcCheckboxRadioSwitch :checked.sync="form.enabled">
+				<NcCheckboxRadioSwitch v-model="form.enabled">
 					Workflow aktiv
 				</NcCheckboxRadioSwitch>
 
@@ -118,10 +118,10 @@
 				</NcNoteCard>
 
 				<div class="wfda-form-actions">
-					<NcButton type="primary" native-type="submit" :disabled="saving">
+					<NcButton variant="primary" type="submit" :disabled="saving">
 						Speichern
 					</NcButton>
-					<NcButton type="tertiary" :disabled="saving" @click="cancelForm">
+					<NcButton variant="tertiary" type="button" :disabled="saving" @click="cancelForm">
 						Abbrechen
 					</NcButton>
 				</div>
@@ -230,10 +230,11 @@ async function onBoardChange(boardId) {
 		return
 	}
 
+	// One failing endpoint must not take the other two dropdowns down with it.
 	const [stacks, labels, participants] = await Promise.all([
-		fetchStacks(boardId),
-		fetchLabels(boardId),
-		fetchParticipants(boardId),
+		fetchStacks(boardId).catch(() => []),
+		fetchLabels(boardId).catch(() => []),
+		fetchParticipants(boardId).catch(() => []),
 	])
 
 	stacksByBoard[boardId] = stacks