feat(board): add shared physical quest boards

README.md

@@ -6,7 +6,7 @@ The approved behavior is specified in the [OKF knowledge bundle](knowledge/index
 
 ## Status
 
-The project foundation and user stories are established. Quest-board behavior remains in the backlog until its stories are implemented and verified.
+Administrators can register persistent shared quest boards by targeting a block within five blocks and running `/questadmin createboard`. Right-clicking any registered board opens the native quest-board dialog. Quest creation, delivery, and claims remain under development.
 
 ## Requirements
 

build.gradle.kts

@@ -28,6 +28,7 @@ dependencies {
     testImplementation("org.purpurmc.purpur:purpur-api:26.2.build.2618-stable")
     testImplementation(platform("org.junit:junit-bom:5.13.4"))
     testImplementation("org.junit.jupiter:junit-jupiter")
+    testImplementation("org.mockito:mockito-core:5.18.0")
     testImplementation("org.yaml:snakeyaml:2.4")
     testRuntimeOnly("org.junit.platform:junit-platform-launcher")
 }

knowledge/log.md

@@ -26,3 +26,10 @@ description: Chronological record of material decisions affecting Spigot Quest B
 - Published the project to the public `dmg/spigot-quest-board` Gitea repository.
 - Added strict Java 25/Purpur 26.2 Gradle builds, plugin metadata, a metadata regression test, and CI/release workflows modeled on Spigot Base.
 - Verified the plugin foundation and JAR with `./gradlew clean check jar`.
+
+## 2026-09-05 — Shared physical quest boards
+
+- Added durable world-UUID and block-coordinate board registration through `/questadmin createboard`.
+- Registered main-hand interactions open one shared native Purpur dialog while unregistered blocks remain untouched.
+- Persistence publishes a board only after an atomic YAML save succeeds and rejects duplicate locations.
+- Verified 11 tests and the plugin JAR with `./gradlew clean check jar`.

knowledge/user-stories/us-002-create-and-use-shared-quest-boards.md

@@ -2,7 +2,7 @@
 type: User Story
 title: "US-002: Create and use shared quest boards"
 description: Let administrators establish persistent physical boards that expose one shared quest system.
-status: backlog
+status: done
 ---
 
 # US-002: Create and use shared quest boards
@@ -11,15 +11,15 @@ As an **administrator**, I want to turn a targeted block into a quest board so t
 
 ## Acceptance criteria
 
-- [ ] An authorized administrator can use `/questadmin createboard` to register the block they are targeting.
+- [x] An authorized administrator can use `/questadmin createboard` to register the block they are targeting.
-- [ ] Creation rejects a missing, invalid, or already registered target without changing state.
+- [x] Creation rejects a missing, invalid, or already registered target without changing state.
-- [ ] Registered boards persist across server restarts with their world and block coordinates.
+- [x] Registered boards persist across server restarts with their world and block coordinates.
-- [ ] Interacting with any registered board opens the quest-board interface.
+- [x] Interacting with any registered board opens the quest-board interface.
-- [ ] Every registered board exposes the same global quests and claimable items.
+- [x] Every registered board exposes the same global quests and claimable items.
-- [ ] The interface uses Purpur's supported native dialog API and follows the interaction style of Spigot Base.
+- [x] The interface uses Purpur's supported native dialog API and follows the interaction style of Spigot Base.
-- [ ] Ordinary block interaction is not intercepted at unregistered locations.
+- [x] Ordinary block interaction is not intercepted at unregistered locations.
-- [ ] Administrative actions require the `spigotquestboard.admin` permission, granted to server operators by default.
+- [x] Administrative actions require the `spigotquestboard.admin` permission, granted to server operators by default.
-- [ ] Automated tests verify board registration, persistence, shared visibility, authorization, and interaction routing.
+- [x] Automated tests verify board registration, persistence, shared visibility, authorization, and interaction routing.
 
 ## Related
 

src/main/java/games/dmg/spigotquestboard/BoardId.java

@@ -0,0 +1,17 @@
+package games.dmg.spigotquestboard;
+
+import java.util.Objects;
+import java.util.UUID;
+import org.bukkit.block.Block;
+
+record BoardId(UUID worldId, int x, int y, int z) {
+    BoardId {
+        Objects.requireNonNull(worldId, "worldId");
+    }
+
+    static BoardId from(Block block) {
+        return new BoardId(
+            block.getWorld().getUID(), block.getX(), block.getY(), block.getZ()
+        );
+    }
+}

src/main/java/games/dmg/spigotquestboard/BoardRegistrationResult.java

@@ -0,0 +1,6 @@
+package games.dmg.spigotquestboard;
+
+enum BoardRegistrationResult {
+    CREATED,
+    ALREADY_REGISTERED
+}

src/main/java/games/dmg/spigotquestboard/BoardRegistry.java

@@ -0,0 +1,47 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+
+final class BoardRegistry {
+    private final BoardRepository repository;
+    private Map<BoardId, RegisteredBoard> boards;
+
+    BoardRegistry(BoardRepository repository) throws IOException {
+        this.repository = Objects.requireNonNull(repository, "repository");
+        boards = index(repository.load());
+    }
+
+    synchronized BoardRegistrationResult register(RegisteredBoard board) throws IOException {
+        Objects.requireNonNull(board, "board");
+        if (boards.containsKey(board.id())) {
+            return BoardRegistrationResult.ALREADY_REGISTERED;
+        }
+        Map<BoardId, RegisteredBoard> candidate = new LinkedHashMap<>(boards);
+        candidate.put(board.id(), board);
+        repository.save(new BoardState(Set.copyOf(candidate.values())));
+        boards = Map.copyOf(candidate);
+        return BoardRegistrationResult.CREATED;
+    }
+
+    synchronized boolean contains(BoardId id) {
+        return boards.containsKey(id);
+    }
+
+    synchronized int size() {
+        return boards.size();
+    }
+
+    private static Map<BoardId, RegisteredBoard> index(BoardState state) throws IOException {
+        Map<BoardId, RegisteredBoard> indexed = new LinkedHashMap<>();
+        for (RegisteredBoard board : state.boards()) {
+            if (indexed.put(board.id(), board) != null) {
+                throw new IOException("Duplicate quest board location: " + board.id());
+            }
+        }
+        return Map.copyOf(indexed);
+    }
+}

src/main/java/games/dmg/spigotquestboard/BoardRepository.java

@@ -0,0 +1,8 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+
+interface BoardRepository {
+    BoardState load() throws IOException;
+    void save(BoardState state) throws IOException;
+}

src/main/java/games/dmg/spigotquestboard/BoardState.java

@@ -0,0 +1,14 @@
+package games.dmg.spigotquestboard;
+
+import java.util.Objects;
+import java.util.Set;
+
+record BoardState(Set<RegisteredBoard> boards) {
+    BoardState {
+        boards = Set.copyOf(Objects.requireNonNull(boards, "boards"));
+    }
+
+    static BoardState empty() {
+        return new BoardState(Set.of());
+    }
+}

src/main/java/games/dmg/spigotquestboard/QuestAdminCommand.java

@@ -0,0 +1,50 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.util.Objects;
+import org.bukkit.block.Block;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandExecutor;
+import org.bukkit.command.CommandSender;
+import org.bukkit.entity.Player;
+
+final class QuestAdminCommand implements CommandExecutor {
+    private static final String PERMISSION = "spigotquestboard.admin";
+    private final BoardRegistry registry;
+
+    QuestAdminCommand(BoardRegistry registry) {
+        this.registry = Objects.requireNonNull(registry, "registry");
+    }
+
+    @Override
+    public boolean onCommand(
+        CommandSender sender, Command command, String label, String[] arguments
+    ) {
+        if (!sender.hasPermission(PERMISSION)) {
+            sender.sendMessage("You do not have permission to administer quest boards.");
+            return true;
+        }
+        if (arguments.length != 1 || !"createboard".equalsIgnoreCase(arguments[0])) {
+            sender.sendMessage("Usage: /questadmin createboard");
+            return true;
+        }
+        if (!(sender instanceof Player player)) {
+            sender.sendMessage("A player must target the quest board block.");
+            return true;
+        }
+        Block target = player.getTargetBlockExact(5);
+        if (target == null) {
+            sender.sendMessage("Target a physical block within five blocks.");
+            return true;
+        }
+        try {
+            BoardRegistrationResult result = registry.register(RegisteredBoard.from(target));
+            sender.sendMessage(result == BoardRegistrationResult.CREATED
+                ? "Quest board created."
+                : "That block is already a quest board.");
+        } catch (IOException exception) {
+            sender.sendMessage("The quest board could not be saved. No board was created.");
+        }
+        return true;
+    }
+}

src/main/java/games/dmg/spigotquestboard/QuestBoardDialogUi.java

@@ -0,0 +1,28 @@
+package games.dmg.spigotquestboard;
+
+import io.papermc.paper.dialog.Dialog;
+import io.papermc.paper.registry.data.dialog.DialogBase;
+import io.papermc.paper.registry.data.dialog.body.DialogBody;
+import io.papermc.paper.registry.data.dialog.type.DialogType;
+import java.util.List;
+import net.kyori.adventure.text.Component;
+import org.bukkit.entity.Player;
+
+final class QuestBoardDialogUi implements QuestBoardUi {
+    @Override
+    public void open(Player player) {
+        DialogBase base = DialogBase.builder(Component.text("Quest Board"))
+            .externalTitle(Component.text("Quest Board"))
+            .body(List.of(DialogBody.plainMessage(
+                Component.text("No active quests or claimable items."), 420
+            )))
+            .canCloseWithEscape(true)
+            .pause(false)
+            .afterAction(DialogBase.DialogAfterAction.CLOSE)
+            .build();
+        Dialog dialog = Dialog.create(factory -> factory.empty()
+            .base(base)
+            .type(DialogType.notice()));
+        player.showDialog(dialog);
+    }
+}

src/main/java/games/dmg/spigotquestboard/QuestBoardInteractionListener.java

@@ -0,0 +1,31 @@
+package games.dmg.spigotquestboard;
+
+import java.util.Objects;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.Listener;
+import org.bukkit.event.block.Action;
+import org.bukkit.event.player.PlayerInteractEvent;
+import org.bukkit.inventory.EquipmentSlot;
+
+final class QuestBoardInteractionListener implements Listener {
+    private final BoardRegistry registry;
+    private final QuestBoardUi ui;
+
+    QuestBoardInteractionListener(BoardRegistry registry, QuestBoardUi ui) {
+        this.registry = Objects.requireNonNull(registry, "registry");
+        this.ui = Objects.requireNonNull(ui, "ui");
+    }
+
+    @EventHandler(priority = EventPriority.NORMAL, ignoreCancelled = true)
+    public void onPlayerInteract(PlayerInteractEvent event) {
+        if (event.getAction() != Action.RIGHT_CLICK_BLOCK
+            || event.getHand() != EquipmentSlot.HAND
+            || event.getClickedBlock() == null
+            || !registry.contains(BoardId.from(event.getClickedBlock()))) {
+            return;
+        }
+        event.setCancelled(true);
+        ui.open(event.getPlayer());
+    }
+}

src/main/java/games/dmg/spigotquestboard/QuestBoardUi.java

@@ -0,0 +1,7 @@
+package games.dmg.spigotquestboard;
+
+import org.bukkit.entity.Player;
+
+interface QuestBoardUi {
+    void open(Player player);
+}

src/main/java/games/dmg/spigotquestboard/RegisteredBoard.java

@@ -0,0 +1,15 @@
+package games.dmg.spigotquestboard;
+
+import java.util.Objects;
+import org.bukkit.block.Block;
+
+record RegisteredBoard(BoardId id, String worldName) {
+    RegisteredBoard {
+        Objects.requireNonNull(id, "id");
+        Objects.requireNonNull(worldName, "worldName");
+    }
+
+    static RegisteredBoard from(Block block) {
+        return new RegisteredBoard(BoardId.from(block), block.getWorld().getName());
+    }
+}

src/main/java/games/dmg/spigotquestboard/SpigotQuestBoardPlugin.java

@@ -1,10 +1,34 @@
 package games.dmg.spigotquestboard;
 
+import java.io.IOException;
+import java.util.Objects;
+import java.util.logging.Level;
+import org.bukkit.command.PluginCommand;
 import org.bukkit.plugin.java.JavaPlugin;
 
 public final class SpigotQuestBoardPlugin extends JavaPlugin {
     @Override
     public void onEnable() {
-        getLogger().info("Spigot Quest Board enabled.");
+        final BoardRegistry boards;
+        try {
+            boards = new BoardRegistry(new YamlBoardRepository(
+                getDataFolder().toPath().resolve("boards.yml")
+            ));
+        } catch (IOException exception) {
+            getLogger().log(Level.SEVERE, "Could not load quest boards", exception);
+            getServer().getPluginManager().disablePlugin(this);
+            return;
+        }
+
+        QuestAdminCommand admin = new QuestAdminCommand(boards);
+        command("questadmin").setExecutor(admin);
+        getServer().getPluginManager().registerEvents(
+            new QuestBoardInteractionListener(boards, new QuestBoardDialogUi()), this
+        );
+        getLogger().info("Spigot Quest Board enabled with " + boards.size() + " boards.");
+    }
+
+    private PluginCommand command(String name) {
+        return Objects.requireNonNull(getCommand(name), "Missing command metadata for " + name);
     }
 }

src/main/java/games/dmg/spigotquestboard/YamlBoardRepository.java

@@ -0,0 +1,104 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.util.ArrayList;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.UUID;
+import org.bukkit.configuration.InvalidConfigurationException;
+import org.bukkit.configuration.file.YamlConfiguration;
+
+final class YamlBoardRepository implements BoardRepository {
+    private final Path path;
+
+    YamlBoardRepository(Path path) {
+        this.path = path;
+    }
+
+    @Override
+    public BoardState load() throws IOException {
+        if (!Files.exists(path)) {
+            return BoardState.empty();
+        }
+        YamlConfiguration yaml = new YamlConfiguration();
+        try {
+            yaml.load(path.toFile());
+        } catch (InvalidConfigurationException exception) {
+            throw new IOException("Invalid quest board state", exception);
+        }
+        Set<RegisteredBoard> boards = new LinkedHashSet<>();
+        for (Map<?, ?> entry : yaml.getMapList("boards")) {
+            try {
+                UUID worldId = UUID.fromString(requiredString(entry, "world-id"));
+                String worldName = requiredString(entry, "world-name");
+                BoardId id = new BoardId(
+                    worldId,
+                    requiredInteger(entry, "x"),
+                    requiredInteger(entry, "y"),
+                    requiredInteger(entry, "z")
+                );
+                RegisteredBoard board = new RegisteredBoard(id, worldName);
+                boolean duplicate = boards.stream().anyMatch(existing -> existing.id().equals(id));
+                if (duplicate) {
+                    throw new IOException("Duplicate quest board location: " + id);
+                }
+                boards.add(board);
+            } catch (IllegalArgumentException exception) {
+                throw new IOException("Invalid quest board record", exception);
+            }
+        }
+        return new BoardState(boards);
+    }
+
+    @Override
+    public void save(BoardState state) throws IOException {
+        YamlConfiguration yaml = new YamlConfiguration();
+        List<Map<String, Object>> serialized = new ArrayList<>();
+        for (RegisteredBoard board : state.boards()) {
+            serialized.add(Map.of(
+                "world-id", board.id().worldId().toString(),
+                "world-name", board.worldName(),
+                "x", board.id().x(),
+                "y", board.id().y(),
+                "z", board.id().z()
+            ));
+        }
+        yaml.set("boards", serialized);
+        Path parent = path.toAbsolutePath().getParent();
+        Files.createDirectories(parent);
+        Path temporary = Files.createTempFile(parent, path.getFileName().toString(), ".tmp");
+        try {
+            yaml.save(temporary.toFile());
+            try {
+                Files.move(temporary, path, StandardCopyOption.REPLACE_EXISTING,
+                    StandardCopyOption.ATOMIC_MOVE);
+            } catch (AtomicMoveNotSupportedException exception) {
+                Files.move(temporary, path, StandardCopyOption.REPLACE_EXISTING);
+            }
+        } finally {
+            Files.deleteIfExists(temporary);
+        }
+    }
+
+    private static String requiredString(Map<?, ?> entry, String key) {
+        Object value = entry.get(key);
+        if (!(value instanceof String text) || text.isBlank()) {
+            throw new IllegalArgumentException("Missing " + key);
+        }
+        return text;
+    }
+
+    private static int requiredInteger(Map<?, ?> entry, String key) {
+        Object value = entry.get(key);
+        if (!(value instanceof Number number)) {
+            throw new IllegalArgumentException("Missing " + key);
+        }
+        return number.intValue();
+    }
+}

src/test/java/games/dmg/spigotquestboard/BoardRegistryTest.java

@@ -0,0 +1,67 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.IOException;
+import java.util.Set;
+import java.util.UUID;
+import org.junit.jupiter.api.Test;
+
+final class BoardRegistryTest {
+    private static final RegisteredBoard BOARD = new RegisteredBoard(
+        new BoardId(UUID.fromString("00000000-0000-0000-0000-000000000001"), 1, 64, 2),
+        "world"
+    );
+
+    @Test
+    void registersAndPersistsBeforePublishingBoard() throws IOException {
+        RecordingRepository repository = new RecordingRepository(BoardState.empty());
+        BoardRegistry registry = new BoardRegistry(repository);
+
+        assertEquals(BoardRegistrationResult.CREATED, registry.register(BOARD));
+        assertTrue(registry.contains(BOARD.id()));
+        assertEquals(Set.of(BOARD), repository.saved.boards());
+    }
+
+    @Test
+    void duplicateDoesNotWrite() throws IOException {
+        RecordingRepository repository = new RecordingRepository(new BoardState(Set.of(BOARD)));
+        BoardRegistry registry = new BoardRegistry(repository);
+
+        assertEquals(BoardRegistrationResult.ALREADY_REGISTERED, registry.register(BOARD));
+        assertEquals(0, repository.saveCount);
+    }
+
+    @Test
+    void failedPersistenceDoesNotPublishBoard() throws Exception {
+        BoardRepository repository = new BoardRepository() {
+            @Override public BoardState load() { return BoardState.empty(); }
+            @Override public void save(BoardState state) throws IOException {
+                throw new IOException("disk failed");
+            }
+        };
+        BoardRegistry registry = new BoardRegistry(repository);
+
+        assertThrows(IOException.class, () -> registry.register(BOARD));
+        assertFalse(registry.contains(BOARD.id()));
+    }
+
+    private static final class RecordingRepository implements BoardRepository {
+        private final BoardState initial;
+        private BoardState saved;
+        private int saveCount;
+
+        private RecordingRepository(BoardState initial) {
+            this.initial = initial;
+        }
+
+        @Override public BoardState load() { return initial; }
+        @Override public void save(BoardState state) {
+            saved = state;
+            saveCount++;
+        }
+    }
+}

src/test/java/games/dmg/spigotquestboard/QuestAdminCommandTest.java

@@ -0,0 +1,78 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.util.Set;
+import java.util.UUID;
+import org.bukkit.World;
+import org.bukkit.block.Block;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
+import org.bukkit.entity.Player;
+import org.junit.jupiter.api.Test;
+
+final class QuestAdminCommandTest {
+    @Test
+    void unauthorizedSenderCannotCreateBoard() throws Exception {
+        MemoryBoardRepository repository = new MemoryBoardRepository();
+        QuestAdminCommand executor = new QuestAdminCommand(new BoardRegistry(repository));
+        Player player = mock(Player.class);
+        when(player.hasPermission("spigotquestboard.admin")).thenReturn(false);
+
+        assertTrue(executor.onCommand(player, mock(Command.class), "questadmin", new String[] {"createboard"}));
+
+        verify(player, never()).getTargetBlockExact(5);
+        assertTrue(repository.state.boards().isEmpty());
+    }
+
+    @Test
+    void registersTargetedPhysicalBlock() throws Exception {
+        MemoryBoardRepository repository = new MemoryBoardRepository();
+        QuestAdminCommand executor = new QuestAdminCommand(new BoardRegistry(repository));
+        Player player = mock(Player.class);
+        Block block = mock(Block.class);
+        World world = mock(World.class);
+        UUID worldId = UUID.randomUUID();
+        when(player.hasPermission("spigotquestboard.admin")).thenReturn(true);
+        when(player.getTargetBlockExact(5)).thenReturn(block);
+        when(block.getWorld()).thenReturn(world);
+        when(world.getUID()).thenReturn(worldId);
+        when(world.getName()).thenReturn("world");
+        when(block.getX()).thenReturn(10);
+        when(block.getY()).thenReturn(65);
+        when(block.getZ()).thenReturn(-4);
+
+        assertTrue(executor.onCommand(player, mock(Command.class), "questadmin", new String[] {"createboard"}));
+
+        assertTrue(repository.state.boards().contains(new RegisteredBoard(
+            new BoardId(worldId, 10, 65, -4), "world"
+        )));
+    }
+
+    @Test
+    void consoleAndMissingTargetDoNotChangeState() throws Exception {
+        MemoryBoardRepository repository = new MemoryBoardRepository();
+        QuestAdminCommand executor = new QuestAdminCommand(new BoardRegistry(repository));
+        CommandSender console = mock(CommandSender.class);
+        when(console.hasPermission("spigotquestboard.admin")).thenReturn(true);
+        assertTrue(executor.onCommand(console, mock(Command.class), "questadmin", new String[] {"createboard"}));
+
+        Player player = mock(Player.class);
+        when(player.hasPermission("spigotquestboard.admin")).thenReturn(true);
+        when(player.getTargetBlockExact(5)).thenReturn(null);
+        assertTrue(executor.onCommand(player, mock(Command.class), "questadmin", new String[] {"createboard"}));
+
+        assertTrue(repository.state.boards().isEmpty());
+    }
+
+    private static final class MemoryBoardRepository implements BoardRepository {
+        private BoardState state = new BoardState(Set.of());
+        @Override public BoardState load() { return state; }
+        @Override public void save(BoardState state) { this.state = state; }
+    }
+}

src/test/java/games/dmg/spigotquestboard/QuestBoardInteractionListenerTest.java

@@ -0,0 +1,86 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.util.Set;
+import java.util.UUID;
+import org.bukkit.World;
+import org.bukkit.block.Block;
+import org.bukkit.entity.Player;
+import org.bukkit.event.block.Action;
+import org.bukkit.event.player.PlayerInteractEvent;
+import org.bukkit.inventory.EquipmentSlot;
+import org.junit.jupiter.api.Test;
+
+final class QuestBoardInteractionListenerTest {
+    @Test
+    void registeredBoardsOpenTheSameGlobalInterface() throws Exception {
+        UUID worldId = UUID.randomUUID();
+        RegisteredBoard first = new RegisteredBoard(new BoardId(worldId, 1, 64, 1), "world");
+        RegisteredBoard second = new RegisteredBoard(new BoardId(worldId, 2, 64, 2), "world");
+        BoardRepository repository = new FixedRepository(new BoardState(Set.of(first, second)));
+        BoardRegistry registry = new BoardRegistry(repository);
+        CountingUi ui = new CountingUi();
+        QuestBoardInteractionListener listener = new QuestBoardInteractionListener(registry, ui);
+        Player player = mock(Player.class);
+
+        PlayerInteractEvent firstEvent = eventFor(first, player);
+        PlayerInteractEvent secondEvent = eventFor(second, player);
+        listener.onPlayerInteract(firstEvent);
+        listener.onPlayerInteract(secondEvent);
+
+        verify(firstEvent).setCancelled(true);
+        verify(secondEvent).setCancelled(true);
+        assertEquals(2, ui.opens);
+    }
+
+    @Test
+    void unregisteredAndOffHandInteractionsPassThrough() throws Exception {
+        BoardRegistry registry = new BoardRegistry(new FixedRepository(BoardState.empty()));
+        CountingUi ui = new CountingUi();
+        QuestBoardInteractionListener listener = new QuestBoardInteractionListener(registry, ui);
+        PlayerInteractEvent event = eventFor(
+            new RegisteredBoard(new BoardId(UUID.randomUUID(), 1, 64, 1), "world"),
+            mock(Player.class)
+        );
+        listener.onPlayerInteract(event);
+        verify(event, never()).setCancelled(true);
+
+        when(event.getHand()).thenReturn(EquipmentSlot.OFF_HAND);
+        listener.onPlayerInteract(event);
+        assertEquals(0, ui.opens);
+    }
+
+    private static PlayerInteractEvent eventFor(RegisteredBoard board, Player player) {
+        PlayerInteractEvent event = mock(PlayerInteractEvent.class);
+        Block block = mock(Block.class);
+        World world = mock(World.class);
+        when(event.getAction()).thenReturn(Action.RIGHT_CLICK_BLOCK);
+        when(event.getHand()).thenReturn(EquipmentSlot.HAND);
+        when(event.getClickedBlock()).thenReturn(block);
+        when(event.getPlayer()).thenReturn(player);
+        when(block.getWorld()).thenReturn(world);
+        when(world.getUID()).thenReturn(board.id().worldId());
+        when(world.getName()).thenReturn(board.worldName());
+        when(block.getX()).thenReturn(board.id().x());
+        when(block.getY()).thenReturn(board.id().y());
+        when(block.getZ()).thenReturn(board.id().z());
+        return event;
+    }
+
+    private static final class FixedRepository implements BoardRepository {
+        private final BoardState state;
+        private FixedRepository(BoardState state) { this.state = state; }
+        @Override public BoardState load() { return state; }
+        @Override public void save(BoardState state) { throw new UnsupportedOperationException(); }
+    }
+
+    private static final class CountingUi implements QuestBoardUi {
+        private int opens;
+        @Override public void open(Player player) { opens++; }
+    }
+}

src/test/java/games/dmg/spigotquestboard/YamlBoardRepositoryTest.java

@@ -0,0 +1,43 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.nio.file.Path;
+import java.util.Set;
+import java.util.UUID;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+final class YamlBoardRepositoryTest {
+    @TempDir Path temporaryDirectory;
+
+    @Test
+    void missingFileLoadsEmptyState() throws Exception {
+        YamlBoardRepository repository = new YamlBoardRepository(
+            temporaryDirectory.resolve("boards.yml")
+        );
+
+        assertTrue(repository.load().boards().isEmpty());
+    }
+
+    @Test
+    void roundTripsWorldIdentityAndCoordinates() throws Exception {
+        Path path = temporaryDirectory.resolve("boards.yml");
+        YamlBoardRepository repository = new YamlBoardRepository(path);
+        BoardState expected = new BoardState(Set.of(
+            new RegisteredBoard(
+                new BoardId(UUID.fromString("00000000-0000-0000-0000-000000000001"), 4, 70, -8),
+                "survival"
+            ),
+            new RegisteredBoard(
+                new BoardId(UUID.fromString("00000000-0000-0000-0000-000000000002"), 4, 70, -8),
+                "resource"
+            )
+        ));
+
+        repository.save(expected);
+
+        assertEquals(expected, repository.load());
+    }
+}