feat(quests): add expiration and held item claims

README.md

@@ -6,7 +6,7 @@ The approved behavior is specified in the [OKF knowledge bundle](knowledge/index
 
 ## Status
 
-Administrators can register persistent shared quest boards by targeting a block within five blocks and running `/questadmin createboard`. Right-clicking any registered board opens a native dialog where a player can request a block and quantity while escrowing the exact reward stack held in their main hand. Every board and `/quests list` show the same active quests with requested blocks, rewards, issuers, and time remaining. Delivery and claims remain under development.
+Administrators can register persistent shared quest boards by targeting a block within five blocks and running `/questadmin createboard`. Right-clicking any registered board opens a native dialog where a player can request a block and quantity while escrowing the exact reward stack held in their main hand. Every board and `/quests list` show the same active quests with requested blocks, rewards, issuers, and time remaining. Players can complete quests at any board or with `/quests complete <quest>` by delivering the required blocks. Exact escrowed rewards are granted immediately, and delivered blocks are held for the issuer. Issuers can cancel their own active quests at any board or with `/quests cancel <quest>`. Completed deliveries and rewards from cancelled or seven-day-expired quests are held durably and can be collected at any board or with `/quests claim`; inventory overflow drops at the claimant's feet.
 
 ## Requirements
 

knowledge/log.md

@@ -47,3 +47,25 @@ description: Chronological record of material decisions affecting Spigot Quest B
 - Listings include requested blocks, exact reward summaries, issuer names, and boundary-safe remaining durations.
 - Added persisted lifecycle status with backward-compatible active defaults and filtered stale quest IDs from contextual completion and cancellation suggestions.
 - Verified 37 tests and the plugin JAR with `./gradlew clean check jar`.
+
+## 2026-09-05 — Block delivery and quest completion
+
+- Added board actions and `/quests complete <quest>` for exact requested-material delivery from player inventories.
+- Completion serializes state transitions, holds delivered blocks in durable issuer claims, and grants exact escrowed rewards with owner-protected overflow drops.
+- Added durable online and next-login issuer notifications and rollback before persistence succeeds.
+- Verified 49 tests and the plugin JAR with `./gradlew clean check jar`.
+
+## 2026-09-05 — Issuer quest cancellation
+
+- Added issuer-only board actions and `/quests cancel <quest>` with ownership-filtered autocomplete.
+- Cancellation atomically moves exact reward escrow into an issuer claim without directly changing inventory.
+- Serialized cancellation against completion and retained active state when persistence fails.
+- Verified 58 tests and the plugin JAR with `./gradlew clean check jar`.
+
+## 2026-09-05 — Quest expiration and held-item claims
+
+- Added boundary-safe scheduled expiration that moves exact rewards into durable issuer claims.
+- Added claim collection at every board and through `/quests claim`, distinguishing delivered blocks from cancelled or expired reward returns.
+- Inventory overflow drops at the claimant's feet with ownership protection, and failed claim acknowledgement rolls inventory and drops back before retry.
+- Added persisted online and next-login expiry notifications.
+- Verified 73 tests and the plugin JAR with `./gradlew clean check jar`.

knowledge/user-stories/us-005-deliver-blocks-and-complete-a-quest.md

@@ -2,7 +2,7 @@
 type: User Story
 title: "US-005: Deliver blocks and complete a quest"
 description: Let a player deliver requested blocks at a quest board and receive the escrowed reward.
-status: backlog
+status: done
 ---
 
 # US-005: Deliver blocks and complete a quest
@@ -11,17 +11,17 @@ As a **player**, I want to deliver requested blocks to a quest board so that I r
 
 ## Acceptance criteria
 
-- [ ] An active quest offers a Complete Quest action through every registered board.
+- [x] An active quest offers a Complete Quest action through every registered board.
-- [ ] Completion requires the delivering player to possess the full requested quantity of the exact block material.
+- [x] Completion requires the delivering player to possess the full requested quantity of the exact block material.
-- [ ] Successful completion removes the requested blocks from the delivering player's inventory and stores them as a claim for the issuer.
+- [x] Successful completion removes the requested blocks from the delivering player's inventory and stores them as a claim for the issuer.
-- [ ] Successful completion gives the exact escrowed reward items to the delivering player.
+- [x] Successful completion gives the exact escrowed reward items to the delivering player.
-- [ ] Reward items that do not fit are dropped safely at the delivering player's feet with a clear message.
+- [x] Reward items that do not fit are dropped safely at the delivering player's feet with a clear message.
-- [ ] The issuer is notified immediately when online or on their next login when offline that delivered blocks can be claimed at a quest board.
+- [x] The issuer is notified immediately when online or on their next login when offline that delivered blocks can be claimed at a quest board.
-- [ ] When player commands are enabled, `/quests complete <quest>` provides equivalent behavior with contextual autocomplete.
+- [x] When player commands are enabled, `/quests complete <quest>` provides equivalent behavior with contextual autocomplete.
-- [ ] Completion is atomic and exactly one player can complete a quest, including simultaneous attempts.
+- [x] Completion is atomic and exactly one player can complete a quest, including simultaneous attempts.
-- [ ] Validation or persistence failure does not consume delivered blocks, release rewards, or change quest state.
+- [x] Validation or persistence failure does not consume delivered blocks, release rewards, or change quest state.
-- [ ] Completed quests are no longer shown as active or completable.
+- [x] Completed quests are no longer shown as active or completable.
-- [ ] Automated tests verify inventory validation, settlement, overflow, notifications, rollback, and concurrent completion protection.
+- [x] Automated tests verify inventory validation, settlement, overflow, notifications, rollback, and concurrent completion protection.
 
 ## Related
 

knowledge/user-stories/us-006-cancel-an-owned-quest.md

@@ -2,7 +2,7 @@
 type: User Story
 title: "US-006: Cancel an owned quest"
 description: Let an issuer cancel an active quest and reclaim its escrowed reward safely.
-status: backlog
+status: done
 ---
 
 # US-006: Cancel an owned quest
@@ -11,15 +11,15 @@ As a **quest issuer**, I want to cancel my active quest so that I can reclaim th
 
 ## Acceptance criteria
 
-- [ ] An issuer can cancel their own active quest through any registered board.
+- [x] An issuer can cancel their own active quest through any registered board.
-- [ ] A player cannot cancel a quest issued by another player.
+- [x] A player cannot cancel a quest issued by another player.
-- [ ] Completed, cancelled, and expired quests cannot be cancelled.
+- [x] Completed, cancelled, and expired quests cannot be cancelled.
-- [ ] Cancellation removes the quest from active listings and converts its exact escrowed reward into a claim for the issuer.
+- [x] Cancellation removes the quest from active listings and converts its exact escrowed reward into a claim for the issuer.
-- [ ] The reward is not inserted directly into the issuer's inventory during cancellation.
+- [x] The reward is not inserted directly into the issuer's inventory during cancellation.
-- [ ] When player commands are enabled, `/quests cancel <quest>` provides equivalent behavior and only autocompletes the player's cancellable quest identifiers.
+- [x] When player commands are enabled, `/quests cancel <quest>` provides equivalent behavior and only autocompletes the player's cancellable quest identifiers.
-- [ ] Cancellation and simultaneous completion are serialized so items cannot be duplicated or lost.
+- [x] Cancellation and simultaneous completion are serialized so items cannot be duplicated or lost.
-- [ ] Persistence failure leaves the quest active and its reward escrowed.
+- [x] Persistence failure leaves the quest active and its reward escrowed.
-- [ ] Automated tests verify ownership, state validation, claim creation, autocomplete, rollback, and completion races.
+- [x] Automated tests verify ownership, state validation, claim creation, autocomplete, rollback, and completion races.
 
 ## Related
 

knowledge/user-stories/us-007-expire-quests-and-claim-held-items.md

@@ -2,7 +2,7 @@
 type: User Story
 title: "US-007: Expire quests and claim held items"
 description: Hold delivered blocks and returned rewards until their owner safely claims them.
-status: backlog
+status: done
 ---
 
 # US-007: Expire quests and claim held items
@@ -11,18 +11,18 @@ As a **quest issuer**, I want delivered blocks and returned rewards held at the
 
 ## Acceptance criteria
 
-- [ ] An uncompleted quest expires seven days after its creation time.
+- [x] An uncompleted quest expires seven days after its creation time.
-- [ ] Expiration removes the quest from active listings and converts its exact escrowed reward into a claim for the issuer.
+- [x] Expiration removes the quest from active listings and converts its exact escrowed reward into a claim for the issuer.
-- [ ] Completed-quest claims contain the exact block items delivered by the completing player.
+- [x] Completed-quest claims contain the exact block items delivered by the completing player.
-- [ ] Claims from completion, cancellation, and expiration can be collected through any registered board.
+- [x] Claims from completion, cancellation, and expiration can be collected through any registered board.
-- [ ] The board clearly distinguishes delivered blocks from returned rewards.
+- [x] The board clearly distinguishes delivered blocks from returned rewards.
-- [ ] Online issuers receive a real-time message when items become claimable.
+- [x] Online issuers receive a real-time message when items become claimable.
-- [ ] Offline issuers receive a message on their next login.
+- [x] Offline issuers receive a message on their next login.
-- [ ] When player commands are enabled, `/quests claim` collects the same pending claims.
+- [x] When player commands are enabled, `/quests claim` collects the same pending claims.
-- [ ] Items are inserted into the claimant's inventory where space permits; overflow is dropped safely at their feet with a clear message.
+- [x] Items are inserted into the claimant's inventory where space permits; overflow is dropped safely at their feet with a clear message.
-- [ ] A claim is removed only after all of its items have been inserted or dropped successfully.
+- [x] A claim is removed only after all of its items have been inserted or dropped successfully.
-- [ ] Pending claims and notification state survive logout and server restart without duplication or loss.
+- [x] Pending claims and notification state survive logout and server restart without duplication or loss.
-- [ ] Automated tests verify expiry boundaries, each claim source, notifications, overflow, failure recovery, and persistence.
+- [x] Automated tests verify expiry boundaries, each claim source, notifications, overflow, failure recovery, and persistence.
 
 ## Related
 

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

@@ -0,0 +1,54 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.util.Objects;
+import java.util.UUID;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import org.bukkit.Server;
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.player.PlayerJoinEvent;
+
+final class BukkitIssuerNotifier implements IssuerNotifier, Listener {
+    private final QuestService quests;
+    private final Server server;
+    private final Logger logger;
+
+    BukkitIssuerNotifier(QuestService quests, Server server, Logger logger) {
+        this.quests = Objects.requireNonNull(quests, "quests");
+        this.server = Objects.requireNonNull(server, "server");
+        this.logger = Objects.requireNonNull(logger, "logger");
+    }
+
+    @Override
+    public void notifyIfOnline(UUID issuerId) {
+        Player player = server.getPlayer(issuerId);
+        if (player != null && player.isOnline()) {
+            deliver(player);
+        }
+    }
+
+    @EventHandler
+    public void onPlayerJoin(PlayerJoinEvent event) {
+        deliver(event.getPlayer());
+    }
+
+    void deliver(Player player) {
+        for (IssuerNotification notification
+            : quests.pendingNotifications(player.getUniqueId())) {
+            player.sendMessage(notification.message());
+            try {
+                quests.markNotificationDelivered(notification.id());
+            } catch (IOException exception) {
+                logger.log(
+                    Level.WARNING,
+                    "Could not persist delivery of issuer notification " + notification.id()
+                        + "; it will be retried",
+                    exception
+                );
+            }
+        }
+    }
+}

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

@@ -0,0 +1,66 @@
+package games.dmg.spigotquestboard;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import org.bukkit.entity.Item;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.PlayerInventory;
+
+final class BukkitQuestClaimInventory implements QuestClaimInventory {
+    @Override
+    public PreparedClaim prepare(List<EscrowItem> items) {
+        List<ItemStack> stacks = items.stream().map(EscrowItem::toItemStack).toList();
+        return player -> deliver(player, stacks);
+    }
+
+    static Delivery deliver(Player player, List<ItemStack> stacks) {
+        PlayerInventory inventory = player.getInventory();
+        ItemStack[] snapshot = cloneContents(inventory.getStorageContents());
+        List<Item> drops = new ArrayList<>();
+        int overflow = 0;
+        try {
+            for (ItemStack stack : stacks) {
+                Map<Integer, ItemStack> leftovers = inventory.addItem(stack.clone());
+                for (ItemStack leftover : leftovers.values()) {
+                    Item drop = player.getWorld().dropItem(player.getLocation(), leftover.clone());
+                    drops.add(drop);
+                    drop.setOwner(player.getUniqueId());
+                    overflow += leftover.getAmount();
+                }
+            }
+        } catch (RuntimeException exception) {
+            inventory.setStorageContents(cloneContents(snapshot));
+            drops.forEach(Item::remove);
+            throw exception;
+        }
+        int deliveredOverflow = overflow;
+        return new Delivery() {
+            private boolean rolledBack;
+
+            @Override
+            public int overflowAmount() {
+                return deliveredOverflow;
+            }
+
+            @Override
+            public void rollback() {
+                if (rolledBack) {
+                    return;
+                }
+                inventory.setStorageContents(cloneContents(snapshot));
+                drops.forEach(Item::remove);
+                rolledBack = true;
+            }
+        };
+    }
+
+    private static ItemStack[] cloneContents(ItemStack[] contents) {
+        ItemStack[] copy = new ItemStack[contents.length];
+        for (int index = 0; index < contents.length; index++) {
+            copy[index] = contents[index] == null ? null : contents[index].clone();
+        }
+        return copy;
+    }
+}

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

@@ -0,0 +1,92 @@
+package games.dmg.spigotquestboard;
+
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import org.bukkit.Material;
+import org.bukkit.entity.Item;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.PlayerInventory;
+
+final class BukkitQuestCompletionInventory implements QuestCompletionInventory {
+    @Override
+    public RemovedDelivery remove(Player player, String materialName, int amount) {
+        Objects.requireNonNull(player, "player");
+        Material material = Objects.requireNonNull(Material.matchMaterial(materialName), "material");
+        PlayerInventory inventory = player.getInventory();
+        ItemStack[] contents = inventory.getStorageContents();
+        int available = 0;
+        for (ItemStack stack : contents) {
+            if (stack != null && stack.getType() == material) {
+                available += stack.getAmount();
+            }
+        }
+        if (available < amount) {
+            throw new IllegalArgumentException(
+                "You need exactly " + amount + " " + material.name()
+                    + " to complete this quest (you have " + available + ")."
+            );
+        }
+
+        Map<Integer, ItemStack> snapshots = new LinkedHashMap<>();
+        List<EscrowItem> removedItems = new ArrayList<>();
+        int remaining = amount;
+        for (int slot = 0; slot < contents.length && remaining > 0; slot++) {
+            ItemStack stack = contents[slot];
+            if (stack == null || stack.getType() != material) {
+                continue;
+            }
+            snapshots.put(slot, stack.clone());
+            int removedAmount = Math.min(stack.getAmount(), remaining);
+            ItemStack removed = stack.clone();
+            removed.setAmount(removedAmount);
+            removedItems.add(EscrowItem.fromItemStack(removed));
+            if (removedAmount == stack.getAmount()) {
+                inventory.clear(slot);
+            } else {
+                ItemStack reduced = stack.clone();
+                reduced.setAmount(stack.getAmount() - removedAmount);
+                inventory.setItem(slot, reduced);
+            }
+            remaining -= removedAmount;
+        }
+
+        return new RemovedDelivery() {
+            private boolean rolledBack;
+
+            @Override
+            public List<EscrowItem> items() {
+                return List.copyOf(removedItems);
+            }
+
+            @Override
+            public void rollback() {
+                if (rolledBack) {
+                    return;
+                }
+                snapshots.forEach(inventory::setItem);
+                rolledBack = true;
+            }
+        };
+    }
+
+    @Override
+    public PreparedReward prepare(List<EscrowItem> reward) {
+        List<ItemStack> stacks = reward.stream().map(EscrowItem::toItemStack).toList();
+        return player -> {
+            int overflow = 0;
+            for (ItemStack stack : stacks) {
+                Map<Integer, ItemStack> leftovers = player.getInventory().addItem(stack.clone());
+                for (ItemStack leftover : leftovers.values()) {
+                    Item dropped = player.getWorld().dropItem(player.getLocation(), leftover);
+                    dropped.setOwner(player.getUniqueId());
+                    overflow += leftover.getAmount();
+                }
+            }
+            return overflow;
+        };
+    }
+}

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

@@ -0,0 +1,4 @@
+package games.dmg.spigotquestboard;
+
+record ClaimCollectionResult(int claimsCollected, int overflowItems) {
+}

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

@@ -0,0 +1,23 @@
+package games.dmg.spigotquestboard;
+
+import java.time.Instant;
+import java.util.Objects;
+import java.util.UUID;
+
+record IssuerNotification(
+    UUID id,
+    UUID questId,
+    UUID recipientId,
+    String message,
+    Instant createdAt
+) {
+    IssuerNotification {
+        Objects.requireNonNull(id, "id");
+        Objects.requireNonNull(questId, "questId");
+        Objects.requireNonNull(recipientId, "recipientId");
+        if (Objects.requireNonNull(message, "message").isBlank()) {
+            throw new IllegalArgumentException("Notification message must not be blank");
+        }
+        Objects.requireNonNull(createdAt, "createdAt");
+    }
+}

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

@@ -0,0 +1,7 @@
+package games.dmg.spigotquestboard;
+
+import java.util.UUID;
+
+interface IssuerNotifier {
+    void notifyIfOnline(UUID issuerId);
+}

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

@@ -10,6 +10,7 @@ import io.papermc.paper.registry.data.dialog.type.DialogType;
 import java.io.IOException;
 import java.time.Clock;
 import java.time.Duration;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
 import net.kyori.adventure.text.Component;
@@ -19,11 +20,47 @@ import org.bukkit.entity.Player;
 final class QuestBoardDialogUi implements QuestBoardUi {
     private final QuestCreationGateway creator;
     private final QuestBrowser browser;
+    private final QuestCompletionGateway completer;
+    private final QuestCancellationGateway canceller;
+    private final QuestClaimGateway claimant;
     private final Clock clock;
 
     QuestBoardDialogUi(QuestCreationGateway creator, QuestBrowser browser, Clock clock) {
+        this(creator, browser, null, null, null, clock);
+    }
+
+    QuestBoardDialogUi(
+        QuestCreationGateway creator,
+        QuestBrowser browser,
+        QuestCompletionGateway completer,
+        Clock clock
+    ) {
+        this(creator, browser, completer, null, null, clock);
+    }
+
+    QuestBoardDialogUi(
+        QuestCreationGateway creator,
+        QuestBrowser browser,
+        QuestCompletionGateway completer,
+        QuestCancellationGateway canceller,
+        Clock clock
+    ) {
+        this(creator, browser, completer, canceller, null, clock);
+    }
+
+    QuestBoardDialogUi(
+        QuestCreationGateway creator,
+        QuestBrowser browser,
+        QuestCompletionGateway completer,
+        QuestCancellationGateway canceller,
+        QuestClaimGateway claimant,
+        Clock clock
+    ) {
         this.creator = Objects.requireNonNull(creator, "creator");
         this.browser = Objects.requireNonNull(browser, "browser");
+        this.completer = completer;
+        this.canceller = canceller;
+        this.claimant = claimant;
         this.clock = Objects.requireNonNull(clock, "clock");
     }
 
@@ -45,11 +82,39 @@ final class QuestBoardDialogUi implements QuestBoardUi {
                 .lifetime(Duration.ofMinutes(10))
                 .build()))
             .build();
-        String listing = listingText();
+        java.time.Instant now = clock.instant();
+        List<Quest> activeQuests = browser.activeQuests(now);
+        String listing = QuestListingFormatter.formatAll(activeQuests, now);
+        String claimListing = claimListingText(player);
+        List<ActionButton> actions = new ArrayList<>();
+        actions.add(create);
+        if (claimant != null) {
+            actions.add(ActionButton.builder(Component.text("Collect pending claims"))
+                .tooltip(Component.text("Collect delivered blocks and returned rewards"))
+                .width(250)
+                .action(DialogAction.customClick((response, audience) -> {
+                    if (audience instanceof Player respondingPlayer) {
+                        submitClaim(respondingPlayer);
+                    }
+                }, ClickCallback.Options.builder()
+                    .uses(1)
+                    .lifetime(Duration.ofMinutes(10))
+                    .build()))
+                .build());
+        }
+        for (Quest quest : activeQuests) {
+            if (completer != null) {
+                actions.add(completionButton(quest));
+            }
+            if (canceller != null && quest.issuerId().equals(player.getUniqueId())) {
+                actions.add(cancellationButton(quest));
+            }
+        }
         DialogBase base = DialogBase.builder(Component.text("Quest Board"))
             .externalTitle(Component.text("Quest Board — Active quests and create"))
             .body(List.of(DialogBody.plainMessage(Component.text(
-                "ACTIVE QUESTS\n" + listing + "\n\nCREATE A QUEST\n"
+                "ACTIVE QUESTS\n" + listing + "\n\nYOUR PENDING CLAIMS\n" + claimListing
+                    + "\n\nCREATE A QUEST\n"
                     + "Hold the reward in your main hand. The entire exact stack, including all item metadata, "
                     + "will be removed and held in escrow only if this quest saves successfully."
             ), 800)))
@@ -69,7 +134,7 @@ final class QuestBoardDialogUi implements QuestBoardUi {
             .build();
         player.showDialog(Dialog.create(factory -> factory.empty()
             .base(base)
-            .type(DialogType.notice(create))));
+            .type(DialogType.multiAction(actions).columns(1).build())));
     }
 
     String listingText() {
@@ -77,6 +142,111 @@ final class QuestBoardDialogUi implements QuestBoardUi {
         return QuestListingFormatter.formatAll(browser.activeQuests(now), now);
     }
 
+    String claimListingText(Player player) {
+        if (claimant == null) {
+            return "Claim collection is unavailable.";
+        }
+        List<QuestClaim> claims = claimant.pendingClaims(player);
+        if (claims.isEmpty()) {
+            return "No pending claims.";
+        }
+        return claims.stream().map(claim -> {
+            String kind = claim.type() == QuestClaimType.DELIVERED_BLOCKS
+                ? "DELIVERED BLOCKS" : "RETURNED REWARD (" + claim.source().name() + ")";
+            String items = claim.items().stream()
+                .map(item -> item.amount() + " " + item.material())
+                .reduce((left, right) -> left + ", " + right)
+                .orElseThrow();
+            return kind + " — " + items + " — quest " + claim.questId();
+        }).reduce((left, right) -> left + "\n" + right).orElseThrow();
+    }
+
+    private ActionButton completionButton(Quest quest) {
+        String id = quest.id().toString();
+        return ActionButton.builder(Component.text(
+                "Complete " + quest.requestedAmount() + " " + quest.requestedMaterial()
+            ))
+            .tooltip(Component.text("Deliver blocks for quest " + id))
+            .width(250)
+            .action(DialogAction.customClick((response, audience) -> {
+                if (audience instanceof Player respondingPlayer) {
+                    submitCompletion(respondingPlayer, id);
+                }
+            }, ClickCallback.Options.builder()
+                .uses(1)
+                .lifetime(Duration.ofMinutes(10))
+                .build()))
+            .build();
+    }
+
+    private ActionButton cancellationButton(Quest quest) {
+        String id = quest.id().toString();
+        return ActionButton.builder(Component.text(
+                "Cancel " + quest.requestedAmount() + " " + quest.requestedMaterial()
+            ))
+            .tooltip(Component.text("Return the escrowed reward to claims for quest " + id))
+            .width(250)
+            .action(DialogAction.customClick((response, audience) -> {
+                if (audience instanceof Player respondingPlayer) {
+                    submitCancellation(respondingPlayer, id);
+                }
+            }, ClickCallback.Options.builder()
+                .uses(1)
+                .lifetime(Duration.ofMinutes(10))
+                .build()))
+            .build();
+    }
+
+    List<String> cancellableQuestIds(Player player) {
+        return browser.cancellableQuestIds(player.getUniqueId(), clock.instant());
+    }
+
+    void submitCancellation(Player player, String questId) {
+        if (canceller == null) {
+            player.sendMessage("Quest cancellation is unavailable.");
+            return;
+        }
+        try {
+            canceller.cancel(player, questId, clock.instant());
+        } catch (IllegalArgumentException | IllegalStateException exception) {
+            player.sendMessage(exception.getMessage());
+        } catch (IOException exception) {
+            player.sendMessage(
+                "The quest could not be saved. It remains active and its reward remains escrowed."
+            );
+        }
+    }
+
+    void submitClaim(Player player) {
+        if (claimant == null) {
+            player.sendMessage("Quest claims are unavailable.");
+            return;
+        }
+        try {
+            claimant.collect(player);
+        } catch (IOException | RuntimeException exception) {
+            player.sendMessage(
+                "Your claim could not be collected safely. It remains pending; please try again."
+            );
+        }
+    }
+
+    void submitCompletion(Player player, String questId) {
+        if (completer == null) {
+            player.sendMessage("Quest completion is unavailable.");
+            return;
+        }
+        try {
+            completer.complete(player, questId, clock.instant());
+        } catch (IllegalArgumentException | IllegalStateException exception) {
+            player.sendMessage(exception.getMessage());
+        } catch (IOException exception) {
+            player.sendMessage(
+                "The quest could not be saved. Your delivered blocks were restored."
+            );
+        }
+    }
+
     void submit(Player player, String material, String quantityText) {
         final int quantity;
         try {

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

@@ -0,0 +1,31 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.Objects;
+import java.util.UUID;
+import org.bukkit.entity.Player;
+
+final class QuestCancellationController implements QuestCancellationGateway {
+    private final QuestService quests;
+
+    QuestCancellationController(QuestService quests) {
+        this.quests = Objects.requireNonNull(quests, "quests");
+    }
+
+    @Override
+    public QuestClaim cancel(Player player, String questId, Instant cancelledAt) throws IOException {
+        Objects.requireNonNull(player, "player");
+        final UUID id;
+        try {
+            id = UUID.fromString(Objects.requireNonNull(questId, "questId"));
+        } catch (IllegalArgumentException exception) {
+            throw new IllegalArgumentException("Quest identifier must be a valid UUID.", exception);
+        }
+        QuestClaim claim = quests.cancel(id, player.getUniqueId(), cancelledAt);
+        player.sendMessage(
+            "Quest " + id + " cancelled. Your exact escrowed reward is ready to claim at a quest board."
+        );
+        return claim;
+    }
+}

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

@@ -0,0 +1,9 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.time.Instant;
+import org.bukkit.entity.Player;
+
+interface QuestCancellationGateway {
+    QuestClaim cancel(Player player, String questId, Instant cancelledAt) throws IOException;
+}

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

@@ -0,0 +1,38 @@
+package games.dmg.spigotquestboard;
+
+import java.time.Instant;
+import java.util.List;
+import java.util.Objects;
+import java.util.UUID;
+
+record QuestClaim(
+    UUID id,
+    UUID questId,
+    UUID ownerId,
+    List<EscrowItem> items,
+    Instant createdAt,
+    QuestClaimSource source
+) {
+    QuestClaim {
+        Objects.requireNonNull(id, "id");
+        Objects.requireNonNull(questId, "questId");
+        Objects.requireNonNull(ownerId, "ownerId");
+        items = List.copyOf(Objects.requireNonNull(items, "items"));
+        if (items.isEmpty()) {
+            throw new IllegalArgumentException("Claim items must not be empty");
+        }
+        Objects.requireNonNull(createdAt, "createdAt");
+        Objects.requireNonNull(source, "source");
+    }
+
+    QuestClaim(
+        UUID id, UUID questId, UUID ownerId, List<EscrowItem> items, Instant createdAt
+    ) {
+        this(id, questId, ownerId, items, createdAt, QuestClaimSource.COMPLETION);
+    }
+
+    QuestClaimType type() {
+        return source == QuestClaimSource.COMPLETION
+            ? QuestClaimType.DELIVERED_BLOCKS : QuestClaimType.RETURNED_REWARD;
+    }
+}

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

@@ -0,0 +1,64 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.Objects;
+import org.bukkit.entity.Player;
+
+final class QuestClaimController implements QuestClaimGateway {
+    private final QuestService quests;
+    private final QuestClaimInventory inventory;
+
+    QuestClaimController(QuestService quests, QuestClaimInventory inventory) {
+        this.quests = Objects.requireNonNull(quests, "quests");
+        this.inventory = Objects.requireNonNull(inventory, "inventory");
+    }
+
+    @Override
+    public List<QuestClaim> pendingClaims(Player player) {
+        Objects.requireNonNull(player, "player");
+        return quests.claimsFor(player.getUniqueId());
+    }
+
+    @Override
+    public synchronized ClaimCollectionResult collect(Player player) throws IOException {
+        Objects.requireNonNull(player, "player");
+        List<QuestClaim> claims = quests.claimsFor(player.getUniqueId());
+        if (claims.isEmpty()) {
+            player.sendMessage("You have no pending quest claims.");
+            return new ClaimCollectionResult(0, 0);
+        }
+
+        int collected = 0;
+        int overflow = 0;
+        for (QuestClaim claim : claims) {
+            QuestClaimInventory.PreparedClaim prepared = inventory.prepare(claim.items());
+            QuestClaimInventory.Delivery delivery = prepared.deliver(player);
+            try {
+                quests.acknowledgeClaim(player.getUniqueId(), claim.id());
+            } catch (IOException | RuntimeException exception) {
+                delivery.rollback();
+                throw exception;
+            }
+            collected++;
+            overflow += delivery.overflowAmount();
+            player.sendMessage(description(claim));
+        }
+        player.sendMessage("Collected " + collected + " quest claim(s).");
+        if (overflow > 0) {
+            player.sendMessage(
+                overflow + " item(s) did not fit and were dropped at your feet, protected for you."
+            );
+        }
+        return new ClaimCollectionResult(collected, overflow);
+    }
+
+    private static String description(QuestClaim claim) {
+        if (claim.type() == QuestClaimType.DELIVERED_BLOCKS) {
+            return "Collected delivered blocks from completed quest " + claim.questId() + ".";
+        }
+        String reason = claim.source() == QuestClaimSource.EXPIRATION
+            ? "expired" : "cancelled";
+        return "Collected returned reward from " + reason + " quest " + claim.questId() + ".";
+    }
+}

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

@@ -0,0 +1,13 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.util.List;
+import org.bukkit.entity.Player;
+
+interface QuestClaimGateway {
+    ClaimCollectionResult collect(Player player) throws IOException;
+
+    default List<QuestClaim> pendingClaims(Player player) {
+        return List.of();
+    }
+}

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

@@ -0,0 +1,17 @@
+package games.dmg.spigotquestboard;
+
+import java.util.List;
+import org.bukkit.entity.Player;
+
+interface QuestClaimInventory {
+    PreparedClaim prepare(List<EscrowItem> items);
+
+    interface PreparedClaim {
+        Delivery deliver(Player player);
+    }
+
+    interface Delivery {
+        int overflowAmount();
+        void rollback();
+    }
+}

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

@@ -0,0 +1,7 @@
+package games.dmg.spigotquestboard;
+
+enum QuestClaimSource {
+    COMPLETION,
+    CANCELLATION,
+    EXPIRATION
+}

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

@@ -0,0 +1,6 @@
+package games.dmg.spigotquestboard;
+
+enum QuestClaimType {
+    DELIVERED_BLOCKS,
+    RETURNED_REWARD
+}

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

@@ -16,11 +16,47 @@ final class QuestCommand implements CommandExecutor, TabCompleter {
     private static final List<String> QUANTITIES = List.of("1", "16", "32", "64");
     private final QuestCreationGateway creator;
     private final QuestBrowser browser;
+    private final QuestCompletionGateway completer;
+    private final QuestCancellationGateway canceller;
+    private final QuestClaimGateway claimant;
     private final Clock clock;
 
     QuestCommand(QuestCreationGateway creator, QuestBrowser browser, Clock clock) {
+        this(creator, browser, null, null, null, clock);
+    }
+
+    QuestCommand(
+        QuestCreationGateway creator,
+        QuestBrowser browser,
+        QuestCompletionGateway completer,
+        Clock clock
+    ) {
+        this(creator, browser, completer, null, null, clock);
+    }
+
+    QuestCommand(
+        QuestCreationGateway creator,
+        QuestBrowser browser,
+        QuestCompletionGateway completer,
+        QuestCancellationGateway canceller,
+        Clock clock
+    ) {
+        this(creator, browser, completer, canceller, null, clock);
+    }
+
+    QuestCommand(
+        QuestCreationGateway creator,
+        QuestBrowser browser,
+        QuestCompletionGateway completer,
+        QuestCancellationGateway canceller,
+        QuestClaimGateway claimant,
+        Clock clock
+    ) {
         this.creator = Objects.requireNonNull(creator, "creator");
         this.browser = Objects.requireNonNull(browser, "browser");
+        this.completer = completer;
+        this.canceller = canceller;
+        this.claimant = claimant;
         this.clock = Objects.requireNonNull(clock, "clock");
     }
 
@@ -34,6 +70,64 @@ final class QuestCommand implements CommandExecutor, TabCompleter {
             sender.sendMessage(QuestListingFormatter.formatAll(browser.activeQuests(now), now));
             return true;
         }
+        if (arguments.length == 1 && "claim".equalsIgnoreCase(arguments[0])) {
+            if (!(sender instanceof Player player)) {
+                sender.sendMessage("Only players can collect quest claims.");
+                return true;
+            }
+            if (claimant == null) {
+                sender.sendMessage("Quest claims are unavailable.");
+                return true;
+            }
+            try {
+                claimant.collect(player);
+            } catch (IOException | RuntimeException exception) {
+                sender.sendMessage(
+                    "Your claim could not be collected safely. It remains pending; please try again."
+                );
+            }
+            return true;
+        }
+        if (arguments.length == 2 && "complete".equalsIgnoreCase(arguments[0])) {
+            if (!(sender instanceof Player player)) {
+                sender.sendMessage("Only players can complete quests with inventory items.");
+                return true;
+            }
+            if (completer == null) {
+                sender.sendMessage("Quest completion is unavailable.");
+                return true;
+            }
+            try {
+                completer.complete(player, arguments[1], clock.instant());
+            } catch (IllegalArgumentException | IllegalStateException exception) {
+                sender.sendMessage(exception.getMessage());
+            } catch (IOException exception) {
+                sender.sendMessage(
+                    "The quest could not be saved. Your delivered blocks were restored."
+                );
+            }
+            return true;
+        }
+        if (arguments.length == 2 && "cancel".equalsIgnoreCase(arguments[0])) {
+            if (!(sender instanceof Player player)) {
+                sender.sendMessage("Only players can cancel quests.");
+                return true;
+            }
+            if (canceller == null) {
+                sender.sendMessage("Quest cancellation is unavailable.");
+                return true;
+            }
+            try {
+                canceller.cancel(player, arguments[1], clock.instant());
+            } catch (IllegalArgumentException | IllegalStateException exception) {
+                sender.sendMessage(exception.getMessage());
+            } catch (IOException exception) {
+                sender.sendMessage(
+                    "The quest could not be saved. It remains active and its reward remains escrowed."
+                );
+            }
+            return true;
+        }
         if (arguments.length != 3 || !"create".equalsIgnoreCase(arguments[0])) {
             usage(sender);
             return true;
@@ -68,7 +162,9 @@ final class QuestCommand implements CommandExecutor, TabCompleter {
             return List.of();
         }
         if (arguments.length == 1) {
-            return startsWith(List.of("create", "list"), arguments[0]);
+            return startsWith(
+                List.of("create", "list", "complete", "cancel", "claim"), arguments[0]
+            );
         }
         if (arguments.length == 2 && "create".equalsIgnoreCase(arguments[0])) {
             return creator.suggestBlockMaterials(arguments[1]);
@@ -96,7 +192,10 @@ final class QuestCommand implements CommandExecutor, TabCompleter {
     }
 
     private static void usage(CommandSender sender) {
-        sender.sendMessage("Usage: /quests [list] | /quests create <block> <quantity>");
+        sender.sendMessage(
+            "Usage: /quests [list] | /quests create <block> <quantity> | "
+                + "/quests complete <quest> | /quests cancel <quest> | /quests claim"
+        );
         sender.sendMessage("Hold the entire reward stack in your main hand; its exact metadata will be escrowed.");
     }
 }

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

@@ -0,0 +1,9 @@
+package games.dmg.spigotquestboard;
+
+import java.util.List;
+
+record QuestCompletion(Quest quest, QuestClaim claim, List<EscrowItem> reward) {
+    QuestCompletion {
+        reward = List.copyOf(reward);
+    }
+}

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

@@ -0,0 +1,57 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.Objects;
+import java.util.UUID;
+import org.bukkit.entity.Player;
+
+final class QuestCompletionController implements QuestCompletionGateway {
+    private final QuestService quests;
+    private final QuestCompletionInventory inventory;
+    private final IssuerNotifier notifier;
+
+    QuestCompletionController(
+        QuestService quests, QuestCompletionInventory inventory, IssuerNotifier notifier
+    ) {
+        this.quests = Objects.requireNonNull(quests, "quests");
+        this.inventory = Objects.requireNonNull(inventory, "inventory");
+        this.notifier = Objects.requireNonNull(notifier, "notifier");
+    }
+
+    @Override
+    public QuestCompletion complete(Player player, String questId, Instant completedAt)
+        throws IOException {
+        Objects.requireNonNull(player, "player");
+        final UUID id;
+        try {
+            id = UUID.fromString(Objects.requireNonNull(questId, "questId"));
+        } catch (IllegalArgumentException exception) {
+            throw new IllegalArgumentException("Quest identifier must be a valid UUID.", exception);
+        }
+        Quest quest = quests.completionCandidate(id, completedAt);
+        QuestCompletionInventory.PreparedReward reward = inventory.prepare(quest.reward());
+        QuestCompletionInventory.RemovedDelivery delivery = inventory.remove(
+            player, quest.requestedMaterial(), quest.requestedAmount()
+        );
+        final QuestCompletion completion;
+        try {
+            completion = quests.complete(id, delivery.items(), completedAt);
+        } catch (IOException | RuntimeException exception) {
+            delivery.rollback();
+            throw exception;
+        }
+
+        int overflow = reward.grantAndDropOverflow(player);
+        player.sendMessage(
+            "Quest " + id + " completed. You received the exact escrowed reward."
+        );
+        if (overflow > 0) {
+            player.sendMessage(
+                overflow + " reward item(s) did not fit and were dropped safely at your feet."
+            );
+        }
+        notifier.notifyIfOnline(completion.quest().issuerId());
+        return completion;
+    }
+}

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

@@ -0,0 +1,9 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.time.Instant;
+import org.bukkit.entity.Player;
+
+interface QuestCompletionGateway {
+    QuestCompletion complete(Player player, String questId, Instant completedAt) throws IOException;
+}

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

@@ -0,0 +1,19 @@
+package games.dmg.spigotquestboard;
+
+import java.util.List;
+import org.bukkit.entity.Player;
+
+interface QuestCompletionInventory {
+    RemovedDelivery remove(Player player, String material, int amount);
+
+    PreparedReward prepare(List<EscrowItem> reward);
+
+    interface RemovedDelivery {
+        List<EscrowItem> items();
+        void rollback();
+    }
+
+    interface PreparedReward {
+        int grantAndDropOverflow(Player player);
+    }
+}

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

@@ -0,0 +1,39 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+final class QuestExpiryTask implements Runnable {
+    private final QuestService quests;
+    private final IssuerNotifier notifier;
+    private final Clock clock;
+    private final Logger logger;
+
+    QuestExpiryTask(
+        QuestService quests, IssuerNotifier notifier, Clock clock, Logger logger
+    ) {
+        this.quests = quests;
+        this.notifier = notifier;
+        this.clock = clock;
+        this.logger = logger;
+    }
+
+    @Override
+    public void run() {
+        final List<QuestClaim> claims;
+        try {
+            claims = quests.expire(clock.instant());
+        } catch (IOException exception) {
+            logger.log(Level.WARNING, "Could not persist expired quests; expiration will be retried", exception);
+            return;
+        }
+        Set<java.util.UUID> owners = new LinkedHashSet<>();
+        claims.forEach(claim -> owners.add(claim.ownerId()));
+        owners.forEach(notifier::notifyIfOnline);
+    }
+}

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

@@ -3,20 +3,21 @@ package games.dmg.spigotquestboard;
 import java.io.IOException;
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
+import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.List;
-import java.util.Map;
 import java.util.Locale;
+import java.util.Map;
 import java.util.Objects;
 import java.util.UUID;
 
 final class QuestService implements QuestBrowser {
     private final QuestRepository repository;
-    private Map<UUID, Quest> quests;
+    private QuestState state;
 
     QuestService(QuestRepository repository) throws IOException {
         this.repository = Objects.requireNonNull(repository, "repository");
-        quests = new LinkedHashMap<>(repository.load().quests());
+        state = repository.load();
     }
 
     synchronized Quest create(
@@ -38,23 +39,211 @@ final class QuestService implements QuestBrowser {
             UUID.randomUUID(), issuerId, issuerName, material, requestedAmount,
             reward, createdAt, createdAt.plus(7, ChronoUnit.DAYS)
         );
-        Map<UUID, Quest> candidate = new LinkedHashMap<>(quests);
+        Map<UUID, Quest> quests = new LinkedHashMap<>(state.quests());
-        candidate.put(quest.id(), quest);
+        quests.put(quest.id(), quest);
-        repository.save(new QuestState(candidate));
+        save(new QuestState(quests, state.claims(), state.notifications()));
-        quests = Map.copyOf(candidate);
         return quest;
     }
 
+    synchronized Quest completionCandidate(UUID questId, Instant now) {
+        Objects.requireNonNull(questId, "questId");
+        Objects.requireNonNull(now, "now");
+        Quest quest = state.quests().get(questId);
+        if (quest == null) {
+            throw new IllegalArgumentException("Quest not found: " + questId);
+        }
+        if (quest.status() != QuestStatus.ACTIVE || !now.isBefore(quest.expiresAt())) {
+            throw new IllegalStateException("That quest is no longer active or has expired.");
+        }
+        return quest;
+    }
+
+    synchronized QuestCompletion complete(
+        UUID questId, EscrowItem delivered, Instant completedAt
+    ) throws IOException {
+        return complete(questId, List.of(delivered), completedAt);
+    }
+
+    synchronized QuestCompletion complete(
+        UUID questId, List<EscrowItem> delivered, Instant completedAt
+    ) throws IOException {
+        Quest active = completionCandidate(questId, completedAt);
+        List<EscrowItem> delivery = List.copyOf(Objects.requireNonNull(delivered, "delivered"));
+        if (delivery.isEmpty()
+            || delivery.stream().anyMatch(item -> !item.material().equals(active.requestedMaterial()))
+            || delivery.stream().mapToInt(EscrowItem::amount).sum() != active.requestedAmount()) {
+            throw new IllegalArgumentException(
+                "Delivery must contain exactly " + active.requestedAmount() + " "
+                    + active.requestedMaterial() + "."
+            );
+        }
+
+        Quest completed = new Quest(
+            active.id(), active.issuerId(), active.issuerName(), active.requestedMaterial(),
+            active.requestedAmount(), active.reward(), active.createdAt(), active.expiresAt(),
+            QuestStatus.COMPLETED
+        );
+        QuestClaim claim = new QuestClaim(
+            UUID.randomUUID(), active.id(), active.issuerId(), delivery, completedAt,
+            QuestClaimSource.COMPLETION
+        );
+        IssuerNotification notification = new IssuerNotification(
+            UUID.randomUUID(), active.id(), active.issuerId(),
+            "Quest " + active.id() + " was completed. Your delivered "
+                + active.requestedMaterial() + " blocks can be claimed at a quest board.",
+            completedAt
+        );
+
+        Map<UUID, Quest> quests = new LinkedHashMap<>(state.quests());
+        quests.put(active.id(), completed);
+        Map<UUID, List<QuestClaim>> claims = new LinkedHashMap<>(state.claims());
+        List<QuestClaim> ownerClaims = new ArrayList<>(
+            claims.getOrDefault(active.issuerId(), List.of())
+        );
+        ownerClaims.add(claim);
+        claims.put(active.issuerId(), ownerClaims);
+        Map<UUID, IssuerNotification> notifications = new LinkedHashMap<>(state.notifications());
+        notifications.put(notification.id(), notification);
+        save(new QuestState(quests, claims, notifications));
+        return new QuestCompletion(completed, claim, completed.reward());
+    }
+
+    synchronized QuestClaim cancel(UUID questId, UUID issuerId, Instant cancelledAt)
+        throws IOException {
+        Objects.requireNonNull(questId, "questId");
+        Objects.requireNonNull(issuerId, "issuerId");
+        Objects.requireNonNull(cancelledAt, "cancelledAt");
+        Quest active = state.quests().get(questId);
+        if (active == null) {
+            throw new IllegalArgumentException("Quest not found: " + questId);
+        }
+        if (!active.issuerId().equals(issuerId)) {
+            throw new IllegalArgumentException("Only the quest issuer can cancel this quest.");
+        }
+        if (active.status() != QuestStatus.ACTIVE || !cancelledAt.isBefore(active.expiresAt())) {
+            throw new IllegalStateException("That quest is no longer active or has expired.");
+        }
+
+        Quest cancelled = new Quest(
+            active.id(), active.issuerId(), active.issuerName(), active.requestedMaterial(),
+            active.requestedAmount(), active.reward(), active.createdAt(), active.expiresAt(),
+            QuestStatus.CANCELLED
+        );
+        QuestClaim claim = new QuestClaim(
+            UUID.randomUUID(), active.id(), active.issuerId(), active.reward(), cancelledAt,
+            QuestClaimSource.CANCELLATION
+        );
+        Map<UUID, Quest> quests = new LinkedHashMap<>(state.quests());
+        quests.put(active.id(), cancelled);
+        Map<UUID, List<QuestClaim>> claims = new LinkedHashMap<>(state.claims());
+        List<QuestClaim> ownerClaims = new ArrayList<>(
+            claims.getOrDefault(active.issuerId(), List.of())
+        );
+        ownerClaims.add(claim);
+        claims.put(active.issuerId(), ownerClaims);
+        save(new QuestState(quests, claims, state.notifications()));
+        return claim;
+    }
+
+    synchronized List<QuestClaim> expire(Instant now) throws IOException {
+        Objects.requireNonNull(now, "now");
+        Map<UUID, Quest> quests = new LinkedHashMap<>(state.quests());
+        Map<UUID, List<QuestClaim>> claims = mutableClaims(state.claims());
+        Map<UUID, IssuerNotification> notifications = new LinkedHashMap<>(state.notifications());
+        List<QuestClaim> expiredClaims = new ArrayList<>();
+
+        for (Quest active : state.quests().values()) {
+            if (active.status() != QuestStatus.ACTIVE || active.expiresAt().isAfter(now)) {
+                continue;
+            }
+            Quest expired = new Quest(
+                active.id(), active.issuerId(), active.issuerName(), active.requestedMaterial(),
+                active.requestedAmount(), active.reward(), active.createdAt(), active.expiresAt(),
+                QuestStatus.EXPIRED
+            );
+            QuestClaim claim = new QuestClaim(
+                UUID.randomUUID(), active.id(), active.issuerId(), active.reward(), active.expiresAt(),
+                QuestClaimSource.EXPIRATION
+            );
+            IssuerNotification notification = new IssuerNotification(
+                UUID.randomUUID(), active.id(), active.issuerId(),
+                "Quest " + active.id() + " expired. Your returned reward can be claimed "
+                    + "at any quest board or with /quests claim.",
+                active.expiresAt()
+            );
+            quests.put(active.id(), expired);
+            claims.computeIfAbsent(active.issuerId(), ignored -> new ArrayList<>()).add(claim);
+            notifications.put(notification.id(), notification);
+            expiredClaims.add(claim);
+        }
+        if (!expiredClaims.isEmpty()) {
+            save(new QuestState(quests, claims, notifications));
+        }
+        return List.copyOf(expiredClaims);
+    }
+
+    synchronized List<QuestClaim> claimsFor(UUID ownerId) {
+        Objects.requireNonNull(ownerId, "ownerId");
+        return state.claims().getOrDefault(ownerId, List.of());
+    }
+
+    synchronized void acknowledgeClaim(UUID ownerId, UUID claimId) throws IOException {
+        Objects.requireNonNull(ownerId, "ownerId");
+        Objects.requireNonNull(claimId, "claimId");
+        List<QuestClaim> existing = state.claims().getOrDefault(ownerId, List.of());
+        if (existing.stream().noneMatch(claim -> claim.id().equals(claimId))) {
+            return;
+        }
+        Map<UUID, List<QuestClaim>> claims = mutableClaims(state.claims());
+        List<QuestClaim> remaining = new ArrayList<>(claims.get(ownerId));
+        remaining.removeIf(claim -> claim.id().equals(claimId));
+        if (remaining.isEmpty()) {
+            claims.remove(ownerId);
+        } else {
+            claims.put(ownerId, remaining);
+        }
+        save(new QuestState(state.quests(), claims, state.notifications()));
+    }
+
+    synchronized List<IssuerNotification> pendingNotifications(UUID recipientId) {
+        Objects.requireNonNull(recipientId, "recipientId");
+        return state.notifications().values().stream()
+            .filter(notification -> notification.recipientId().equals(recipientId))
+            .toList();
+    }
+
+    synchronized void markNotificationDelivered(UUID notificationId) throws IOException {
+        if (!state.notifications().containsKey(notificationId)) {
+            return;
+        }
+        Map<UUID, IssuerNotification> notifications = new LinkedHashMap<>(state.notifications());
+        notifications.remove(notificationId);
+        save(new QuestState(state.quests(), state.claims(), notifications));
+    }
+
     @Override
     public synchronized List<Quest> activeQuests(Instant now) {
         Objects.requireNonNull(now, "now");
-        return quests.values().stream()
+        return state.quests().values().stream()
             .filter(quest -> quest.status() == QuestStatus.ACTIVE)
             .filter(quest -> now.isBefore(quest.expiresAt()))
             .toList();
     }
 
     synchronized QuestState state() {
-        return new QuestState(quests);
+        return state;
+    }
+
+    private static Map<UUID, List<QuestClaim>> mutableClaims(
+        Map<UUID, List<QuestClaim>> source
+    ) {
+        Map<UUID, List<QuestClaim>> copy = new LinkedHashMap<>();
+        source.forEach((owner, claims) -> copy.put(owner, new ArrayList<>(claims)));
+        return copy;
+    }
+
+    private void save(QuestState candidate) throws IOException {
+        repository.save(candidate);
+        state = candidate;
     }
 }

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

@@ -1,10 +1,16 @@
 package games.dmg.spigotquestboard;
 
+import java.util.LinkedHashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.UUID;
 
-record QuestState(Map<UUID, Quest> quests) {
+record QuestState(
+    Map<UUID, Quest> quests,
+    Map<UUID, List<QuestClaim>> claims,
+    Map<UUID, IssuerNotification> notifications
+) {
     QuestState {
         quests = Map.copyOf(Objects.requireNonNull(quests, "quests"));
         for (Map.Entry<UUID, Quest> entry : quests.entrySet()) {
@@ -12,9 +18,29 @@ record QuestState(Map<UUID, Quest> quests) {
                 throw new IllegalArgumentException("Quest map key does not match quest id");
             }
         }
+        Map<UUID, List<QuestClaim>> immutableClaims = new LinkedHashMap<>();
+        for (Map.Entry<UUID, List<QuestClaim>> entry
+            : Objects.requireNonNull(claims, "claims").entrySet()) {
+            List<QuestClaim> ownerClaims = List.copyOf(entry.getValue());
+            if (ownerClaims.stream().anyMatch(claim -> !claim.ownerId().equals(entry.getKey()))) {
+                throw new IllegalArgumentException("Claim map key does not match owner id");
+            }
+            immutableClaims.put(entry.getKey(), ownerClaims);
+        }
+        claims = Map.copyOf(immutableClaims);
+        notifications = Map.copyOf(Objects.requireNonNull(notifications, "notifications"));
+        for (Map.Entry<UUID, IssuerNotification> entry : notifications.entrySet()) {
+            if (!entry.getKey().equals(entry.getValue().id())) {
+                throw new IllegalArgumentException("Notification map key does not match id");
+            }
+        }
+    }
+
+    QuestState(Map<UUID, Quest> quests) {
+        this(quests, Map.of(), Map.of());
     }
 
     static QuestState empty() {
-        return new QuestState(Map.of());
+        return new QuestState(Map.of(), Map.of(), Map.of());
     }
 }

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

@@ -31,15 +31,37 @@ public final class SpigotQuestBoardPlugin extends JavaPlugin {
         QuestCreationGateway creator = new QuestCreationController(
             quests, new BukkitBlockMaterialCatalog(), new BukkitHeldRewardInventory()
         );
-        QuestCommand questCommand = new QuestCommand(creator, quests, Clock.systemUTC());
+        Clock clock = Clock.systemUTC();
+        BukkitIssuerNotifier notifier = new BukkitIssuerNotifier(
+            quests, getServer(), getLogger()
+        );
+        QuestCompletionGateway completer = new QuestCompletionController(
+            quests, new BukkitQuestCompletionInventory(), notifier
+        );
+        QuestCancellationGateway canceller = new QuestCancellationController(quests);
+        QuestClaimGateway claimant = new QuestClaimController(
+            quests, new BukkitQuestClaimInventory()
+        );
+        QuestCommand questCommand = new QuestCommand(
+            creator, quests, completer, canceller, claimant, clock
+        );
         command("quests").setExecutor(questCommand);
         command("quests").setTabCompleter(questCommand);
+        getServer().getPluginManager().registerEvents(notifier, this);
         getServer().getPluginManager().registerEvents(
             new QuestBoardInteractionListener(
-                boards, new QuestBoardDialogUi(creator, quests, Clock.systemUTC())
+                boards, new QuestBoardDialogUi(
+                    creator, quests, completer, canceller, claimant, clock
+                )
             ),
             this
         );
+        getServer().getScheduler().runTaskTimer(
+            this,
+            new QuestExpiryTask(quests, notifier, clock, getLogger()),
+            0L,
+            20L
+        );
         getLogger().info(
             "Spigot Quest Board enabled with " + boards.size() + " boards and "
                 + quests.state().quests().size() + " quests."

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

@@ -34,6 +34,8 @@ final class YamlQuestRepository implements QuestRepository {
             throw new IOException("Invalid quest state", exception);
         }
         Map<UUID, Quest> quests = new LinkedHashMap<>();
+        Map<UUID, List<QuestClaim>> claims = new LinkedHashMap<>();
+        Map<UUID, IssuerNotification> notifications = new LinkedHashMap<>();
         try {
             for (Map<?, ?> entry : yaml.getMapList("quests")) {
                 UUID id = UUID.fromString(requiredString(entry, "id"));
@@ -43,7 +45,7 @@ final class YamlQuestRepository implements QuestRepository {
                     requiredString(entry, "issuer-name"),
                     requiredString(entry, "requested-material"),
                     requiredInteger(entry, "requested-amount"),
-                    readRewards(entry.get("reward")),
+                    readItems(entry.get("reward"), "reward"),
                     Instant.parse(requiredString(entry, "created-at")),
                     Instant.parse(requiredString(entry, "expires-at")),
                     readStatus(entry.get("status"))
@@ -52,10 +54,37 @@ final class YamlQuestRepository implements QuestRepository {
                     throw new IllegalArgumentException("Duplicate quest id: " + id);
                 }
             }
+            for (Map<?, ?> entry : yaml.getMapList("claims")) {
+                QuestClaim claim = new QuestClaim(
+                    UUID.fromString(requiredString(entry, "id")),
+                    UUID.fromString(requiredString(entry, "quest-id")),
+                    UUID.fromString(requiredString(entry, "owner-id")),
+                    readItems(entry.get("items"), "claim items"),
+                    Instant.parse(requiredString(entry, "created-at")),
+                    readClaimSource(entry.get("source"), quests.get(
+                        UUID.fromString(requiredString(entry, "quest-id"))
+                    ))
+                );
+                claims.computeIfAbsent(claim.ownerId(), ignored -> new ArrayList<>()).add(claim);
+            }
+            for (Map<?, ?> entry : yaml.getMapList("notifications")) {
+                IssuerNotification notification = new IssuerNotification(
+                    UUID.fromString(requiredString(entry, "id")),
+                    UUID.fromString(requiredString(entry, "quest-id")),
+                    UUID.fromString(requiredString(entry, "recipient-id")),
+                    requiredString(entry, "message"),
+                    Instant.parse(requiredString(entry, "created-at"))
+                );
+                if (notifications.put(notification.id(), notification) != null) {
+                    throw new IllegalArgumentException(
+                        "Duplicate notification id: " + notification.id()
+                    );
+                }
+            }
         } catch (IllegalArgumentException | DateTimeParseException exception) {
             throw new IOException("Invalid quest record", exception);
         }
-        return new QuestState(quests);
+        return new QuestState(quests, claims, notifications);
     }
 
     @Override
@@ -72,20 +101,37 @@ final class YamlQuestRepository implements QuestRepository {
             serialized.put("created-at", quest.createdAt().toString());
             serialized.put("expires-at", quest.expiresAt().toString());
             serialized.put("status", quest.status().name());
-            List<Map<String, Object>> rewards = new ArrayList<>();
+            serialized.put("reward", writeItems(quest.reward()));
-            for (EscrowItem reward : quest.reward()) {
-                Map<String, Object> serializedReward = new LinkedHashMap<>();
-                serializedReward.put("material", reward.material());
-                serializedReward.put("amount", reward.amount());
-                if (reward.serializedItem() != null) {
-                    serializedReward.put("item-data", reward.serializedItem());
-                }
-                rewards.add(serializedReward);
-            }
-            serialized.put("reward", rewards);
             serializedQuests.add(serialized);
         }
         yaml.set("quests", serializedQuests);
+
+        List<Map<String, Object>> serializedClaims = new ArrayList<>();
+        for (List<QuestClaim> ownerClaims : state.claims().values()) {
+            for (QuestClaim claim : ownerClaims) {
+                Map<String, Object> serialized = new LinkedHashMap<>();
+                serialized.put("id", claim.id().toString());
+                serialized.put("quest-id", claim.questId().toString());
+                serialized.put("owner-id", claim.ownerId().toString());
+                serialized.put("created-at", claim.createdAt().toString());
+                serialized.put("source", claim.source().name());
+                serialized.put("items", writeItems(claim.items()));
+                serializedClaims.add(serialized);
+            }
+        }
+        yaml.set("claims", serializedClaims);
+
+        List<Map<String, Object>> serializedNotifications = new ArrayList<>();
+        for (IssuerNotification notification : state.notifications().values()) {
+            Map<String, Object> serialized = new LinkedHashMap<>();
+            serialized.put("id", notification.id().toString());
+            serialized.put("quest-id", notification.questId().toString());
+            serialized.put("recipient-id", notification.recipientId().toString());
+            serialized.put("message", notification.message());
+            serialized.put("created-at", notification.createdAt().toString());
+            serializedNotifications.add(serialized);
+        }
+        yaml.set("notifications", serializedNotifications);
         writeAtomically(yaml);
     }
 
@@ -106,24 +152,52 @@ final class YamlQuestRepository implements QuestRepository {
         }
     }
 
-    private static List<EscrowItem> readRewards(Object value) {
+    private static List<EscrowItem> readItems(Object value, String description) {
         if (!(value instanceof List<?> entries) || entries.isEmpty()) {
-            throw new IllegalArgumentException("Missing reward");
+            throw new IllegalArgumentException("Missing " + description);
         }
-        List<EscrowItem> rewards = new ArrayList<>();
+        List<EscrowItem> items = new ArrayList<>();
         for (Object rawEntry : entries) {
             if (!(rawEntry instanceof Map<?, ?> entry)) {
-                throw new IllegalArgumentException("Invalid reward");
+                throw new IllegalArgumentException("Invalid " + description);
             }
             Object data = entry.get("item-data");
             if (data != null && !(data instanceof String)) {
                 throw new IllegalArgumentException("Invalid item-data");
             }
-            rewards.add(new EscrowItem(
+            items.add(new EscrowItem(
                 requiredString(entry, "material"), requiredInteger(entry, "amount"), (String) data
             ));
         }
-        return rewards;
+        return items;
+    }
+
+    private static List<Map<String, Object>> writeItems(List<EscrowItem> items) {
+        List<Map<String, Object>> serializedItems = new ArrayList<>();
+        for (EscrowItem item : items) {
+            Map<String, Object> serialized = new LinkedHashMap<>();
+            serialized.put("material", item.material());
+            serialized.put("amount", item.amount());
+            if (item.serializedItem() != null) {
+                serialized.put("item-data", item.serializedItem());
+            }
+            serializedItems.add(serialized);
+        }
+        return serializedItems;
+    }
+
+    private static QuestClaimSource readClaimSource(Object value, Quest quest) {
+        if (value instanceof String source) {
+            return QuestClaimSource.valueOf(source);
+        }
+        if (value != null) {
+            throw new IllegalArgumentException("Invalid claim source");
+        }
+        if (quest == null || quest.status() == QuestStatus.COMPLETED) {
+            return QuestClaimSource.COMPLETION;
+        }
+        return quest.status() == QuestStatus.EXPIRED
+            ? QuestClaimSource.EXPIRATION : QuestClaimSource.CANCELLATION;
     }
 
     private static QuestStatus readStatus(Object value) {

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

@@ -0,0 +1,109 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.ArgumentMatchers.contains;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.time.Instant;
+import java.util.List;
+import java.util.UUID;
+import java.util.logging.Logger;
+import org.bukkit.Server;
+import org.bukkit.entity.Player;
+import org.junit.jupiter.api.Test;
+
+final class BukkitIssuerNotifierTest {
+    @Test
+    void onlineIssuerIsNotifiedImmediatelyAndDurablePendingStateIsCleared() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = completedService(repository);
+        UUID issuer = service.state().notifications().values().iterator().next().recipientId();
+        Server server = mock(Server.class);
+        Player player = mock(Player.class);
+        when(server.getPlayer(issuer)).thenReturn(player);
+        when(player.isOnline()).thenReturn(true);
+        when(player.getUniqueId()).thenReturn(issuer);
+        BukkitIssuerNotifier notifier = new BukkitIssuerNotifier(
+            service, server, Logger.getAnonymousLogger()
+        );
+
+        notifier.notifyIfOnline(issuer);
+
+        verify(player).sendMessage(contains("can be claimed at a quest board"));
+        assertTrue(service.state().notifications().isEmpty());
+        assertTrue(repository.state.notifications().isEmpty());
+    }
+
+    @Test
+    void failedNotificationAcknowledgementRemainsPendingForRetry() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = completedService(repository);
+        IssuerNotification notification = service.state().notifications().values().iterator().next();
+        Server server = mock(Server.class);
+        Player player = mock(Player.class);
+        when(server.getPlayer(notification.recipientId())).thenReturn(player);
+        when(player.isOnline()).thenReturn(true);
+        when(player.getUniqueId()).thenReturn(notification.recipientId());
+        BukkitIssuerNotifier notifier = new BukkitIssuerNotifier(
+            service, server, Logger.getAnonymousLogger()
+        );
+        repository.fail = true;
+
+        notifier.notifyIfOnline(notification.recipientId());
+        assertEquals(1, service.pendingNotifications(notification.recipientId()).size());
+
+        repository.fail = false;
+        notifier.notifyIfOnline(notification.recipientId());
+        assertTrue(service.pendingNotifications(notification.recipientId()).isEmpty());
+    }
+
+    @Test
+    void offlineNotificationRemainsDurableUntilNextLogin() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = completedService(repository);
+        IssuerNotification notification = service.state().notifications().values().iterator().next();
+        Server server = mock(Server.class);
+        when(server.getPlayer(notification.recipientId())).thenReturn(null);
+        BukkitIssuerNotifier notifier = new BukkitIssuerNotifier(
+            service, server, Logger.getAnonymousLogger()
+        );
+
+        notifier.notifyIfOnline(notification.recipientId());
+        assertEquals(1, service.state().notifications().size());
+
+        Player player = mock(Player.class);
+        when(player.getUniqueId()).thenReturn(notification.recipientId());
+        notifier.deliver(player);
+
+        verify(player).sendMessage(notification.message());
+        assertTrue(service.state().notifications().isEmpty());
+    }
+
+    private static QuestService completedService(Repository repository) throws Exception {
+        QuestService service = new QuestService(repository);
+        Quest quest = service.create(
+            UUID.randomUUID(), "Issuer", "STONE", 1,
+            List.of(new EscrowItem("DIAMOND", 1, null)), Instant.EPOCH
+        );
+        service.complete(
+            quest.id(), new EscrowItem("STONE", 1, null), Instant.EPOCH.plusSeconds(1)
+        );
+        return service;
+    }
+
+    private static final class Repository implements QuestRepository {
+        private QuestState state = QuestState.empty();
+        private boolean fail;
+        @Override public QuestState load() { return state; }
+        @Override
+        public void save(QuestState candidate) throws java.io.IOException {
+            if (fail) {
+                throw new java.io.IOException("disk full");
+            }
+            state = candidate;
+        }
+    }
+}

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

@@ -0,0 +1,94 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.UUID;
+import org.bukkit.Location;
+import org.bukkit.World;
+import org.bukkit.entity.Item;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.PlayerInventory;
+import org.junit.jupiter.api.Test;
+
+final class BukkitQuestClaimInventoryTest {
+    @Test
+    void inventoryOverflowIsDroppedAtFeetWithOwnerProtection() {
+        UUID owner = UUID.randomUUID();
+        Player player = mock(Player.class);
+        PlayerInventory inventory = mock(PlayerInventory.class);
+        World world = mock(World.class);
+        Location feet = mock(Location.class);
+        Item dropped = mock(Item.class);
+        ItemStack requested = mock(ItemStack.class);
+        ItemStack requestedCopy = mock(ItemStack.class);
+        ItemStack leftover = mock(ItemStack.class);
+        ItemStack leftoverCopy = mock(ItemStack.class);
+        when(requested.clone()).thenReturn(requestedCopy);
+        when(leftover.clone()).thenReturn(leftoverCopy);
+        when(leftover.getAmount()).thenReturn(2);
+        when(player.getUniqueId()).thenReturn(owner);
+        when(player.getInventory()).thenReturn(inventory);
+        when(player.getWorld()).thenReturn(world);
+        when(player.getLocation()).thenReturn(feet);
+        when(inventory.getStorageContents()).thenReturn(new ItemStack[36]);
+        HashMap<Integer, ItemStack> leftovers = new HashMap<>();
+        leftovers.put(0, leftover);
+        when(inventory.addItem(any(ItemStack.class))).thenReturn(leftovers);
+        when(world.dropItem(any(Location.class), any(ItemStack.class))).thenReturn(dropped);
+
+        QuestClaimInventory.Delivery delivery = BukkitQuestClaimInventory.deliver(
+            player, List.of(requested)
+        );
+
+        assertEquals(2, delivery.overflowAmount());
+        verify(world).dropItem(feet, leftoverCopy);
+        verify(dropped).setOwner(owner);
+    }
+
+    @Test
+    void ownerProtectionFailureRestoresInventoryAndRemovesPartialDrop() {
+        Player player = mock(Player.class);
+        PlayerInventory inventory = mock(PlayerInventory.class);
+        World world = mock(World.class);
+        Location feet = mock(Location.class);
+        Item dropped = mock(Item.class);
+        ItemStack requested = mock(ItemStack.class);
+        ItemStack requestedCopy = mock(ItemStack.class);
+        ItemStack leftover = mock(ItemStack.class);
+        ItemStack leftoverCopy = mock(ItemStack.class);
+        ItemStack existing = mock(ItemStack.class);
+        ItemStack existingCopy = mock(ItemStack.class);
+        when(requested.clone()).thenReturn(requestedCopy);
+        when(leftover.clone()).thenReturn(leftoverCopy);
+        when(existing.clone()).thenReturn(existingCopy);
+        when(existingCopy.clone()).thenReturn(existingCopy);
+        ItemStack[] original = new ItemStack[] {existing};
+        when(player.getInventory()).thenReturn(inventory);
+        when(player.getWorld()).thenReturn(world);
+        when(player.getLocation()).thenReturn(feet);
+        when(player.getUniqueId()).thenReturn(UUID.randomUUID());
+        when(inventory.getStorageContents()).thenReturn(original);
+        HashMap<Integer, ItemStack> leftovers = new HashMap<>();
+        leftovers.put(0, leftover);
+        when(inventory.addItem(requestedCopy)).thenReturn(leftovers);
+        when(world.dropItem(any(Location.class), any(ItemStack.class))).thenReturn(dropped);
+        doThrow(new IllegalStateException("owner rejected")).when(dropped).setOwner(any());
+
+        assertThrows(
+            IllegalStateException.class,
+            () -> BukkitQuestClaimInventory.deliver(player, List.of(requested))
+        );
+
+        verify(inventory).setStorageContents(any(ItemStack[].class));
+        verify(dropped).remove();
+    }
+}

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

@@ -35,6 +35,119 @@ final class QuestBoardDialogUiTest {
         );
     }
 
+    @Test
+    void completionActionUsesEquivalentCompletionFlow() {
+        RecordingCreator creator = new RecordingCreator(false);
+        RecordingCompleter completer = new RecordingCompleter();
+        QuestBoardDialogUi ui = new QuestBoardDialogUi(
+            creator, now -> List.of(), completer, Clock.fixed(NOW, ZoneOffset.UTC)
+        );
+        Player player = mock(Player.class);
+        String id = UUID.randomUUID().toString();
+
+        ui.submitCompletion(player, id);
+
+        assertEquals(player, completer.player);
+        assertEquals(id, completer.questId);
+        assertEquals(NOW, completer.completedAt);
+    }
+
+    @Test
+    void claimActionUsesEquivalentCollectionFlowAtABoard() {
+        RecordingCreator creator = new RecordingCreator(false);
+        java.util.concurrent.atomic.AtomicReference<Player> claimantPlayer =
+            new java.util.concurrent.atomic.AtomicReference<>();
+        QuestClaimGateway claimant = player -> {
+            claimantPlayer.set(player);
+            return new ClaimCollectionResult(1, 0);
+        };
+        QuestBoardDialogUi ui = new QuestBoardDialogUi(
+            creator, now -> List.of(), null, null, claimant,
+            Clock.fixed(NOW, ZoneOffset.UTC)
+        );
+        Player player = mock(Player.class);
+
+        ui.submitClaim(player);
+
+        assertEquals(player, claimantPlayer.get());
+    }
+
+    @Test
+    void cancellationActionUsesEquivalentCancellationFlow() {
+        RecordingCreator creator = new RecordingCreator(false);
+        RecordingCanceller canceller = new RecordingCanceller();
+        QuestBoardDialogUi ui = new QuestBoardDialogUi(
+            creator, now -> List.of(), null, canceller, Clock.fixed(NOW, ZoneOffset.UTC)
+        );
+        Player player = mock(Player.class);
+        String id = UUID.randomUUID().toString();
+
+        ui.submitCancellation(player, id);
+
+        assertEquals(player, canceller.player);
+        assertEquals(id, canceller.questId);
+        assertEquals(NOW, canceller.cancelledAt);
+    }
+
+    @Test
+    void boardListingDistinguishesDeliveredBlocksFromReturnedRewards() {
+        RecordingCreator creator = new RecordingCreator(false);
+        Player player = mock(Player.class);
+        UUID owner = UUID.randomUUID();
+        org.mockito.Mockito.when(player.getUniqueId()).thenReturn(owner);
+        QuestClaimGateway claimant = new QuestClaimGateway() {
+            @Override
+            public ClaimCollectionResult collect(Player ignored) {
+                return new ClaimCollectionResult(0, 0);
+            }
+
+            @Override
+            public List<QuestClaim> pendingClaims(Player ignored) {
+                return List.of(
+                    new QuestClaim(
+                        UUID.randomUUID(), UUID.randomUUID(), owner,
+                        List.of(new EscrowItem("STONE", 2, null)), NOW,
+                        QuestClaimSource.COMPLETION
+                    ),
+                    new QuestClaim(
+                        UUID.randomUUID(), UUID.randomUUID(), owner,
+                        List.of(new EscrowItem("DIAMOND", 1, null)), NOW,
+                        QuestClaimSource.EXPIRATION
+                    )
+                );
+            }
+        };
+        QuestBoardDialogUi ui = new QuestBoardDialogUi(
+            creator, now -> List.of(), null, null, claimant,
+            Clock.fixed(NOW, ZoneOffset.UTC)
+        );
+
+        String listing = ui.claimListingText(player);
+
+        org.junit.jupiter.api.Assertions.assertTrue(listing.contains("DELIVERED BLOCKS — 2 STONE"));
+        org.junit.jupiter.api.Assertions.assertTrue(
+            listing.contains("RETURNED REWARD (EXPIRATION) — 1 DIAMOND")
+        );
+    }
+
+    @Test
+    void boardOnlyOffersCancellationActionsForPlayersOwnedActiveQuests() {
+        RecordingCreator creator = new RecordingCreator(false);
+        Quest owned = creator.quest(NOW);
+        Quest other = new Quest(
+            UUID.randomUUID(), UUID.randomUUID(), "Other", "DIRT", 1,
+            List.of(new EscrowItem("COAL", 1, null)), NOW, NOW.plusSeconds(604800)
+        );
+        QuestBoardDialogUi ui = new QuestBoardDialogUi(
+            creator, now -> List.of(owned, other), null, new RecordingCanceller(),
+            Clock.fixed(NOW, ZoneOffset.UTC)
+        );
+        Player issuer = mock(Player.class);
+        org.mockito.Mockito.when(issuer.getUniqueId()).thenReturn(owned.issuerId());
+
+        assertEquals(List.of(owned.id().toString()), ui.cancellableQuestIds(issuer));
+    }
+
     @Test
     void everyOpeningBuildsAListingFromTheCurrentActiveQuests() {
         RecordingCreator creator = new RecordingCreator(false);
@@ -60,6 +173,34 @@ final class QuestBoardDialogUiTest {
         );
     }
 
+    private static final class RecordingCanceller implements QuestCancellationGateway {
+        private Player player;
+        private String questId;
+        private Instant cancelledAt;
+
+        @Override
+        public QuestClaim cancel(Player cancellingPlayer, String id, Instant instant) {
+            player = cancellingPlayer;
+            questId = id;
+            cancelledAt = instant;
+            return null;
+        }
+    }
+
+    private static final class RecordingCompleter implements QuestCompletionGateway {
+        private Player player;
+        private String questId;
+        private Instant completedAt;
+
+        @Override
+        public QuestCompletion complete(Player completingPlayer, String id, Instant instant) {
+            player = completingPlayer;
+            questId = id;
+            completedAt = instant;
+            return null;
+        }
+    }
+
     private static final class RecordingCreator implements QuestCreationGateway {
         private final boolean fail;
         private String material;

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

@@ -0,0 +1,58 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.ArgumentMatchers.contains;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.List;
+import java.util.UUID;
+import org.bukkit.entity.Player;
+import org.junit.jupiter.api.Test;
+
+final class QuestCancellationControllerTest {
+    @Test
+    void cancelsAsPlayerIdentityAndCreatesClaimWithoutInventorySettlement() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        Quest quest = service.create(
+            issuer, "Issuer", "STONE", 1,
+            List.of(new EscrowItem("DIAMOND", 2, "exact-data")), Instant.EPOCH
+        );
+        Player player = mock(Player.class);
+        when(player.getUniqueId()).thenReturn(issuer);
+
+        QuestClaim claim = new QuestCancellationController(service).cancel(
+            player, quest.id().toString(), Instant.EPOCH.plusSeconds(1)
+        );
+
+        assertEquals(quest.reward(), claim.items());
+        assertEquals(List.of(claim), service.state().claims().get(issuer));
+        verify(player).sendMessage(contains("claim"));
+    }
+
+    @Test
+    void rejectsMalformedQuestIdentifier() throws Exception {
+        QuestCancellationController controller = new QuestCancellationController(
+            new QuestService(new Repository())
+        );
+
+        IllegalArgumentException exception = assertThrows(
+            IllegalArgumentException.class,
+            () -> controller.cancel(mock(Player.class), "not-a-uuid", Instant.EPOCH)
+        );
+
+        assertEquals("Quest identifier must be a valid UUID.", exception.getMessage());
+    }
+
+    private static final class Repository implements QuestRepository {
+        private QuestState state = QuestState.empty();
+        @Override public QuestState load() { return state; }
+        @Override public void save(QuestState candidate) throws IOException { state = candidate; }
+    }
+}

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

@@ -0,0 +1,159 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import org.junit.jupiter.api.Test;
+
+final class QuestCancellationServiceTest {
+    @Test
+    void onlyIssuerCanCancelAndExactRewardBecomesClaim() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        EscrowItem reward = new EscrowItem("DIAMOND", 3, "exact-item-data");
+        Quest quest = service.create(
+            issuer, "Issuer", "STONE", 64, List.of(reward), Instant.EPOCH
+        );
+
+        assertThrows(IllegalArgumentException.class, () -> service.cancel(
+            quest.id(), UUID.randomUUID(), Instant.EPOCH.plusSeconds(1)
+        ));
+        QuestClaim claim = service.cancel(
+            quest.id(), issuer, Instant.EPOCH.plusSeconds(1)
+        );
+
+        assertEquals(QuestStatus.CANCELLED, service.state().quests().get(quest.id()).status());
+        assertEquals(List.of(reward), claim.items());
+        assertEquals(List.of(claim), service.state().claims().get(issuer));
+        assertTrue(service.activeQuests(Instant.EPOCH.plusSeconds(1)).isEmpty());
+    }
+
+    @Test
+    void completedCancelledAndExpiredQuestsCannotBeCancelled() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        Quest completed = quest(service, issuer);
+        service.complete(
+            completed.id(), new EscrowItem("STONE", 1, null), Instant.EPOCH.plusSeconds(1)
+        );
+        Quest cancelled = quest(service, issuer);
+        service.cancel(cancelled.id(), issuer, Instant.EPOCH.plusSeconds(1));
+        Quest expired = quest(service, issuer);
+
+        assertThrows(IllegalStateException.class, () -> service.cancel(
+            completed.id(), issuer, Instant.EPOCH.plusSeconds(2)
+        ));
+        assertThrows(IllegalStateException.class, () -> service.cancel(
+            cancelled.id(), issuer, Instant.EPOCH.plusSeconds(2)
+        ));
+        assertThrows(IllegalStateException.class, () -> service.cancel(
+            expired.id(), issuer, expired.expiresAt()
+        ));
+    }
+
+    @Test
+    void persistenceFailureLeavesQuestActiveAndRewardEscrowed() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        Quest quest = quest(service, issuer);
+        QuestState before = service.state();
+        repository.fail = true;
+
+        assertThrows(IOException.class, () -> service.cancel(
+            quest.id(), issuer, Instant.EPOCH.plusSeconds(1)
+        ));
+
+        assertEquals(before, service.state());
+        assertEquals(before, repository.state);
+        assertEquals(QuestStatus.ACTIVE, service.state().quests().get(quest.id()).status());
+        assertTrue(service.state().claims().isEmpty());
+    }
+
+    @Test
+    void simultaneousCancellationAndCompletionSettleEscrowExactlyOnce() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        Quest quest = quest(service, issuer);
+        CountDownLatch start = new CountDownLatch(1);
+        try (ExecutorService executor = Executors.newFixedThreadPool(2)) {
+            List<Future<Boolean>> attempts = new ArrayList<>();
+            attempts.add(executor.submit(() -> {
+                start.await();
+                try {
+                    service.cancel(quest.id(), issuer, Instant.EPOCH.plusSeconds(1));
+                    return true;
+                } catch (IllegalStateException exception) {
+                    return false;
+                }
+            }));
+            attempts.add(executor.submit(() -> {
+                start.await();
+                try {
+                    service.complete(
+                        quest.id(), new EscrowItem("STONE", 1, null),
+                        Instant.EPOCH.plusSeconds(1)
+                    );
+                    return true;
+                } catch (IllegalStateException exception) {
+                    return false;
+                }
+            }));
+            start.countDown();
+            assertEquals(1, attempts.stream().filter(attempt -> {
+                try {
+                    return attempt.get();
+                } catch (Exception exception) {
+                    throw new AssertionError(exception);
+                }
+            }).count());
+        }
+
+        QuestStatus status = service.state().quests().get(quest.id()).status();
+        assertTrue(status == QuestStatus.CANCELLED || status == QuestStatus.COMPLETED);
+        assertEquals(1, service.state().claims().get(issuer).size());
+        QuestClaim settlement = service.state().claims().get(issuer).getFirst();
+        if (status == QuestStatus.CANCELLED) {
+            assertEquals(quest.reward(), settlement.items());
+            assertTrue(service.state().notifications().isEmpty());
+        } else {
+            assertEquals(List.of(new EscrowItem("STONE", 1, null)), settlement.items());
+            assertEquals(1, service.state().notifications().size());
+        }
+    }
+
+    private static Quest quest(QuestService service, UUID issuer) throws IOException {
+        return service.create(
+            issuer, "Issuer", "STONE", 1,
+            List.of(new EscrowItem("DIAMOND", 2, null)), Instant.EPOCH
+        );
+    }
+
+    private static final class Repository implements QuestRepository {
+        private QuestState state = QuestState.empty();
+        private boolean fail;
+
+        @Override public QuestState load() { return state; }
+
+        @Override
+        public void save(QuestState candidate) throws IOException {
+            if (fail) {
+                throw new IOException("disk full");
+            }
+            state = candidate;
+        }
+    }
+}

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

@@ -0,0 +1,133 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.ArgumentMatchers.contains;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.List;
+import java.util.UUID;
+import org.bukkit.entity.Player;
+import org.junit.jupiter.api.Test;
+
+final class QuestClaimControllerTest {
+    @Test
+    void collectsEveryClaimAndClearlyDistinguishesItemsAndOverflow() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = serviceWithAllClaimSources(repository);
+        UUID issuer = service.state().claims().keySet().iterator().next();
+        Player player = mock(Player.class);
+        when(player.getUniqueId()).thenReturn(issuer);
+        RecordingInventory inventory = new RecordingInventory(2);
+
+        ClaimCollectionResult result = new QuestClaimController(service, inventory).collect(player);
+
+        assertEquals(new ClaimCollectionResult(3, 6), result);
+        assertTrue(service.claimsFor(issuer).isEmpty());
+        verify(player).sendMessage(contains("delivered blocks from completed quest"));
+        verify(player).sendMessage(contains("returned reward from cancelled quest"));
+        verify(player).sendMessage(contains("returned reward from expired quest"));
+        verify(player).sendMessage(contains("dropped at your feet, protected for you"));
+    }
+
+    @Test
+    void deliveryFailureLeavesClaimPendingForRetry() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = expiredService(repository);
+        UUID issuer = service.state().claims().keySet().iterator().next();
+        Player player = mock(Player.class);
+        when(player.getUniqueId()).thenReturn(issuer);
+        QuestClaimInventory inventory = items -> ignored -> {
+            throw new IllegalStateException("world rejected drop");
+        };
+
+        assertThrows(
+            IllegalStateException.class,
+            () -> new QuestClaimController(service, inventory).collect(player)
+        );
+
+        assertEquals(1, service.claimsFor(issuer).size());
+    }
+
+    @Test
+    void acknowledgementFailureRollsBackDeliveryAndLeavesClaimPending() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = expiredService(repository);
+        UUID issuer = service.state().claims().keySet().iterator().next();
+        Player player = mock(Player.class);
+        when(player.getUniqueId()).thenReturn(issuer);
+        RecordingInventory inventory = new RecordingInventory(0);
+        repository.fail = true;
+
+        assertThrows(
+            IOException.class,
+            () -> new QuestClaimController(service, inventory).collect(player)
+        );
+
+        assertEquals(1, inventory.rollbacks);
+        assertEquals(1, service.claimsFor(issuer).size());
+    }
+
+    private static QuestService serviceWithAllClaimSources(Repository repository) throws Exception {
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        Quest completed = create(service, issuer, "STONE");
+        Quest cancelled = create(service, issuer, "DIRT");
+        Quest expired = create(service, issuer, "SAND");
+        service.complete(
+            completed.id(), new EscrowItem("STONE", 1, null), Instant.EPOCH.plusSeconds(1)
+        );
+        service.cancel(cancelled.id(), issuer, Instant.EPOCH.plusSeconds(1));
+        service.expire(expired.expiresAt());
+        return service;
+    }
+
+    private static QuestService expiredService(Repository repository) throws Exception {
+        QuestService service = new QuestService(repository);
+        Quest quest = create(service, UUID.randomUUID(), "STONE");
+        service.expire(quest.expiresAt());
+        return service;
+    }
+
+    private static Quest create(QuestService service, UUID issuer, String material)
+        throws IOException {
+        return service.create(
+            issuer, "Issuer", material, 1,
+            List.of(new EscrowItem("DIAMOND", 1, null)), Instant.EPOCH
+        );
+    }
+
+    private static final class RecordingInventory implements QuestClaimInventory {
+        private final int overflow;
+        private int rollbacks;
+
+        private RecordingInventory(int overflow) {
+            this.overflow = overflow;
+        }
+
+        @Override
+        public PreparedClaim prepare(List<EscrowItem> items) {
+            return player -> new Delivery() {
+                @Override public int overflowAmount() { return overflow; }
+                @Override public void rollback() { rollbacks++; }
+            };
+        }
+    }
+
+    private static final class Repository implements QuestRepository {
+        private QuestState state = QuestState.empty();
+        private boolean fail;
+        @Override public QuestState load() { return state; }
+        @Override public void save(QuestState candidate) throws IOException {
+            if (fail) {
+                throw new IOException("disk full");
+            }
+            state = candidate;
+        }
+    }
+}

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

@@ -86,6 +86,66 @@ final class QuestCommandTest {
         verify(player).sendMessage("Quest quantity must be a positive whole number.");
     }
 
+    @Test
+    void completeCommandRoutesPlayerAndCurrentTimeToEquivalentGateway() {
+        RecordingCreator creator = new RecordingCreator();
+        RecordingCompleter completer = new RecordingCompleter();
+        QuestCommand executor = new QuestCommand(
+            creator, now -> List.of(), completer, Clock.fixed(NOW, ZoneOffset.UTC)
+        );
+        Player player = mock(Player.class);
+        String id = UUID.randomUUID().toString();
+
+        assertTrue(executor.onCommand(
+            player, mock(Command.class), "quests", new String[] {"complete", id}
+        ));
+
+        assertEquals(player, completer.player);
+        assertEquals(id, completer.questId);
+        assertEquals(NOW, completer.completedAt);
+    }
+
+    @Test
+    void claimCommandUsesTheSameCollectionGateway() {
+        RecordingCreator creator = new RecordingCreator();
+        Player player = mock(Player.class);
+        java.util.concurrent.atomic.AtomicReference<Player> claimantPlayer =
+            new java.util.concurrent.atomic.AtomicReference<>();
+        QuestClaimGateway claimant = claimingPlayer -> {
+            claimantPlayer.set(claimingPlayer);
+            return new ClaimCollectionResult(1, 0);
+        };
+        QuestCommand executor = new QuestCommand(
+            creator, now -> List.of(), null, null, claimant,
+            Clock.fixed(NOW, ZoneOffset.UTC)
+        );
+
+        assertTrue(executor.onCommand(
+            player, mock(Command.class), "quests", new String[] {"claim"}
+        ));
+
+        assertEquals(player, claimantPlayer.get());
+    }
+
+    @Test
+    void cancelCommandRoutesPlayerAndCurrentTimeToEquivalentGateway() {
+        RecordingCreator creator = new RecordingCreator();
+        RecordingCanceller canceller = new RecordingCanceller();
+        QuestCommand executor = new QuestCommand(
+            creator, now -> List.of(), null, canceller, Clock.fixed(NOW, ZoneOffset.UTC)
+        );
+        Player player = mock(Player.class);
+        String id = UUID.randomUUID().toString();
+
+        assertTrue(executor.onCommand(
+            player, mock(Command.class), "quests", new String[] {"cancel", id}
+        ));
+
+        assertEquals(player, canceller.player);
+        assertEquals(id, canceller.questId);
+        assertEquals(NOW, canceller.cancelledAt);
+    }
+
     @Test
     void questIdentifierAutocompleteOnlyUsesActiveAndOwnedQuests() {
         RecordingCreator creator = new RecordingCreator();
@@ -120,6 +180,10 @@ final class QuestCommandTest {
             executor.onTabComplete(player, command, "quests", new String[] {"cr"}));
         assertEquals(List.of("list"),
             executor.onTabComplete(player, command, "quests", new String[] {"li"}));
+        assertEquals(List.of("cancel"),
+            executor.onTabComplete(player, command, "quests", new String[] {"ca"}));
+        assertEquals(List.of("claim"),
+            executor.onTabComplete(player, command, "quests", new String[] {"cl"}));
         assertEquals(List.of("STONE", "STONE_BRICKS"), executor.onTabComplete(
             player, command, "quests", new String[] {"create", "sto"}
         ));
@@ -140,6 +204,34 @@ final class QuestCommandTest {
         return new QuestCommand(creator, browser, Clock.fixed(NOW, ZoneOffset.UTC));
     }
 
+    private static final class RecordingCanceller implements QuestCancellationGateway {
+        private Player player;
+        private String questId;
+        private Instant cancelledAt;
+
+        @Override
+        public QuestClaim cancel(Player cancellingPlayer, String id, Instant instant) {
+            player = cancellingPlayer;
+            questId = id;
+            cancelledAt = instant;
+            return null;
+        }
+    }
+
+    private static final class RecordingCompleter implements QuestCompletionGateway {
+        private Player player;
+        private String questId;
+        private Instant completedAt;
+
+        @Override
+        public QuestCompletion complete(Player completingPlayer, String id, Instant instant) {
+            player = completingPlayer;
+            questId = id;
+            completedAt = instant;
+            return null;
+        }
+    }
+
     private static final class RecordingCreator implements QuestCreationGateway {
         private Player player;
         private String material;

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

@@ -0,0 +1,118 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import org.junit.jupiter.api.Test;
+
+final class QuestCompletionAtomicityTest {
+    @Test
+    void persistenceFailureChangesNoDurableOrInMemoryState() throws Exception {
+        FailingRepository repository = new FailingRepository();
+        QuestService service = new QuestService(repository);
+        Quest quest = service.create(
+            UUID.randomUUID(), "Issuer", "STONE", 2,
+            List.of(new EscrowItem("DIAMOND", 1, null)), Instant.EPOCH
+        );
+        QuestState before = service.state();
+        repository.fail = true;
+
+        assertThrows(IOException.class, () -> service.complete(
+            quest.id(), new EscrowItem("STONE", 2, null), Instant.EPOCH.plusSeconds(1)
+        ));
+
+        assertEquals(before, service.state());
+        assertEquals(before, repository.state);
+    }
+
+    @Test
+    void rejectsWrongMaterialQuantityExpiredAndAlreadyCompleted() throws Exception {
+        FailingRepository repository = new FailingRepository();
+        QuestService service = new QuestService(repository);
+        Quest quest = service.create(
+            UUID.randomUUID(), "Issuer", "STONE", 2,
+            List.of(new EscrowItem("DIAMOND", 1, null)), Instant.EPOCH
+        );
+
+        assertThrows(IllegalArgumentException.class, () -> service.complete(
+            quest.id(), new EscrowItem("DIRT", 2, null), Instant.EPOCH.plusSeconds(1)
+        ));
+        assertThrows(IllegalArgumentException.class, () -> service.complete(
+            quest.id(), new EscrowItem("STONE", 1, null), Instant.EPOCH.plusSeconds(1)
+        ));
+        assertThrows(IllegalStateException.class, () -> service.complete(
+            quest.id(), new EscrowItem("STONE", 2, null), quest.expiresAt()
+        ));
+        service.complete(
+            quest.id(), new EscrowItem("STONE", 2, null), Instant.EPOCH.plusSeconds(1)
+        );
+        assertThrows(IllegalStateException.class, () -> service.complete(
+            quest.id(), new EscrowItem("STONE", 2, null), Instant.EPOCH.plusSeconds(2)
+        ));
+        assertTrue(service.activeQuests(Instant.EPOCH.plusSeconds(2)).isEmpty());
+    }
+
+    @Test
+    void simultaneousAttemptsSettleExactlyOnce() throws Exception {
+        FailingRepository repository = new FailingRepository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        Quest quest = service.create(
+            issuer, "Issuer", "STONE", 1,
+            List.of(new EscrowItem("DIAMOND", 1, null)), Instant.EPOCH
+        );
+        CountDownLatch start = new CountDownLatch(1);
+        try (ExecutorService executor = Executors.newFixedThreadPool(2)) {
+            List<Future<Boolean>> attempts = new ArrayList<>();
+            for (int index = 0; index < 2; index++) {
+                attempts.add(executor.submit(() -> {
+                    start.await();
+                    try {
+                        service.complete(
+                            quest.id(), new EscrowItem("STONE", 1, null),
+                            Instant.EPOCH.plusSeconds(1)
+                        );
+                        return true;
+                    } catch (IllegalStateException exception) {
+                        return false;
+                    }
+                }));
+            }
+            start.countDown();
+            assertEquals(1, attempts.stream().filter(attempt -> {
+                try {
+                    return attempt.get();
+                } catch (Exception exception) {
+                    throw new AssertionError(exception);
+                }
+            }).count());
+        }
+        assertEquals(1, service.state().claims().get(issuer).size());
+        assertEquals(1, service.state().notifications().size());
+    }
+
+    private static final class FailingRepository implements QuestRepository {
+        private QuestState state = QuestState.empty();
+        private boolean fail;
+
+        @Override public QuestState load() { return state; }
+
+        @Override
+        public void save(QuestState candidate) throws IOException {
+            if (fail) {
+                throw new IOException("disk full");
+            }
+            state = candidate;
+        }
+    }
+}

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

@@ -0,0 +1,142 @@
+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 static org.mockito.ArgumentMatchers.contains;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.List;
+import java.util.UUID;
+import org.bukkit.entity.Player;
+import org.junit.jupiter.api.Test;
+
+final class QuestCompletionControllerTest {
+    @Test
+    void removesExactDeliverySettlesRewardReportsOverflowAndNotifies() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        Quest quest = quest(service, issuer);
+        Inventory inventory = new Inventory();
+        inventory.overflow = 2;
+        RecordingNotifier notifier = new RecordingNotifier();
+        QuestCompletionController controller = new QuestCompletionController(
+            service, inventory, notifier
+        );
+        Player player = mock(Player.class);
+
+        controller.complete(player, quest.id().toString(), Instant.EPOCH.plusSeconds(1));
+
+        assertEquals("STONE", inventory.material);
+        assertEquals(3, inventory.amount);
+        assertTrue(inventory.granted);
+        assertFalse(inventory.rolledBack);
+        assertEquals(issuer, notifier.issuer);
+        assertEquals(
+            List.of(new EscrowItem("STONE", 3, null)),
+            service.state().claims().get(issuer).getFirst().items()
+        );
+        verify(player).sendMessage(contains("exact escrowed reward"));
+        verify(player).sendMessage(contains("dropped safely at your feet"));
+    }
+
+    @Test
+    void inventoryValidationFailureConsumesAndReleasesNothing() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        Quest quest = quest(service, UUID.randomUUID());
+        Inventory inventory = new Inventory();
+        inventory.insufficient = true;
+        Player player = mock(Player.class);
+
+        assertThrows(IllegalArgumentException.class, () -> new QuestCompletionController(
+            service, inventory, ignored -> { }
+        ).complete(player, quest.id().toString(), Instant.EPOCH.plusSeconds(1)));
+
+        assertFalse(inventory.granted);
+        assertEquals(QuestStatus.ACTIVE, service.state().quests().get(quest.id()).status());
+        assertTrue(service.state().claims().isEmpty());
+        verify(player, never()).sendMessage(contains("completed"));
+    }
+
+    @Test
+    void persistenceFailureRollsBackDeliveryAndDoesNotGrantReward() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        Quest quest = quest(service, UUID.randomUUID());
+        Inventory inventory = new Inventory();
+        repository.fail = true;
+
+        assertThrows(IOException.class, () -> new QuestCompletionController(
+            service, inventory, ignored -> { }
+        ).complete(mock(Player.class), quest.id().toString(), Instant.EPOCH.plusSeconds(1)));
+
+        assertTrue(inventory.rolledBack);
+        assertFalse(inventory.granted);
+        assertEquals(QuestStatus.ACTIVE, service.state().quests().get(quest.id()).status());
+    }
+
+    private static Quest quest(QuestService service, UUID issuer) throws IOException {
+        return service.create(
+            issuer, "Issuer", "STONE", 3,
+            List.of(new EscrowItem("DIAMOND", 2, null)), Instant.EPOCH
+        );
+    }
+
+    private static final class Inventory implements QuestCompletionInventory {
+        private String material;
+        private int amount;
+        private boolean insufficient;
+        private boolean rolledBack;
+        private boolean granted;
+        private int overflow;
+
+        @Override
+        public RemovedDelivery remove(Player player, String requestedMaterial, int requestedAmount) {
+            material = requestedMaterial;
+            amount = requestedAmount;
+            if (insufficient) {
+                throw new IllegalArgumentException("not enough blocks");
+            }
+            return new RemovedDelivery() {
+                @Override
+                public List<EscrowItem> items() {
+                    return List.of(new EscrowItem(requestedMaterial, requestedAmount, null));
+                }
+
+                @Override public void rollback() { rolledBack = true; }
+            };
+        }
+
+        @Override
+        public PreparedReward prepare(List<EscrowItem> reward) {
+            return player -> {
+                granted = true;
+                return overflow;
+            };
+        }
+    }
+
+    private static final class RecordingNotifier implements IssuerNotifier {
+        private UUID issuer;
+        @Override public void notifyIfOnline(UUID issuerId) { issuer = issuerId; }
+    }
+
+    private static final class Repository implements QuestRepository {
+        private QuestState state = QuestState.empty();
+        private boolean fail;
+        @Override public QuestState load() { return state; }
+        @Override public void save(QuestState candidate) throws IOException {
+            if (fail) {
+                throw new IOException("disk full");
+            }
+            state = candidate;
+        }
+    }
+}

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

@@ -0,0 +1,37 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.time.Instant;
+import java.util.List;
+import java.util.UUID;
+import org.junit.jupiter.api.Test;
+
+final class QuestCompletionServiceTest {
+    @Test
+    void completesOnceAndHoldsDeliveredBlocksForIssuer() throws Exception {
+        MemoryQuestRepository repository = new MemoryQuestRepository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        Quest quest = service.create(
+            issuer, "Issuer", "STONE", 64,
+            List.of(new EscrowItem("DIAMOND", 3, null)), Instant.EPOCH
+        );
+
+        QuestCompletion completion = service.complete(
+            quest.id(), new EscrowItem("STONE", 64, null), Instant.EPOCH.plusSeconds(1)
+        );
+
+        assertEquals(QuestStatus.COMPLETED, service.state().quests().get(quest.id()).status());
+        assertEquals(quest.reward(), completion.reward());
+        assertTrue(service.state().claims().get(issuer).stream()
+            .anyMatch(claim -> claim.items().equals(List.of(new EscrowItem("STONE", 64, null)))));
+    }
+
+    private static final class MemoryQuestRepository implements QuestRepository {
+        private QuestState state = QuestState.empty();
+        @Override public QuestState load() { return state; }
+        @Override public void save(QuestState state) { this.state = state; }
+    }
+}

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

@@ -0,0 +1,127 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.List;
+import java.util.UUID;
+import org.junit.jupiter.api.Test;
+
+final class QuestExpiryAndClaimServiceTest {
+    @Test
+    void expiryReturnsExactRewardAsTypedClaimAndAcknowledgementRemovesIt() throws Exception {
+        MemoryQuestRepository repository = new MemoryQuestRepository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        EscrowItem reward = new EscrowItem("DIAMOND", 3, "exact-data");
+        Quest quest = service.create(
+            issuer, "Issuer", "STONE", 64, List.of(reward), Instant.EPOCH
+        );
+
+        service.expire(quest.expiresAt());
+        List<QuestClaim> claims = service.claimsFor(issuer);
+
+        assertEquals(QuestStatus.EXPIRED, service.state().quests().get(quest.id()).status());
+        assertEquals(List.of(reward), claims.getFirst().items());
+        assertEquals(QuestClaimSource.EXPIRATION, claims.getFirst().source());
+        assertEquals(QuestClaimType.RETURNED_REWARD, claims.getFirst().type());
+        service.acknowledgeClaim(issuer, claims.getFirst().id());
+        assertTrue(service.claimsFor(issuer).isEmpty());
+    }
+
+    @Test
+    void sevenDayBoundaryIsExclusiveBeforeAndDueExactlyAtExpiration() throws Exception {
+        QuestService service = new QuestService(new MemoryQuestRepository());
+        Quest quest = create(service, UUID.randomUUID());
+
+        assertTrue(service.expire(quest.expiresAt().minusNanos(1)).isEmpty());
+        assertEquals(QuestStatus.ACTIVE, service.state().quests().get(quest.id()).status());
+
+        assertEquals(1, service.expire(quest.expiresAt()).size());
+        assertEquals(QuestStatus.EXPIRED, service.state().quests().get(quest.id()).status());
+        assertTrue(service.expire(quest.expiresAt().plusSeconds(1)).isEmpty());
+        assertEquals(1, service.claimsFor(quest.issuerId()).size());
+    }
+
+    @Test
+    void completionCancellationAndExpirationClaimsKeepTheirDistinctSources() throws Exception {
+        QuestService service = new QuestService(new MemoryQuestRepository());
+        UUID issuer = UUID.randomUUID();
+        Quest completed = create(service, issuer);
+        Quest cancelled = service.create(
+            issuer, "Issuer", "DIRT", 1,
+            List.of(new EscrowItem("EMERALD", 2, null)), Instant.EPOCH
+        );
+        Quest expired = service.create(
+            issuer, "Issuer", "SAND", 1,
+            List.of(new EscrowItem("GOLD_INGOT", 4, null)), Instant.EPOCH
+        );
+
+        service.complete(
+            completed.id(), new EscrowItem("STONE", 1, null), Instant.EPOCH.plusSeconds(1)
+        );
+        service.cancel(cancelled.id(), issuer, Instant.EPOCH.plusSeconds(1));
+        service.expire(expired.expiresAt());
+
+        assertEquals(
+            List.of(
+                QuestClaimSource.COMPLETION,
+                QuestClaimSource.CANCELLATION,
+                QuestClaimSource.EXPIRATION
+            ),
+            service.claimsFor(issuer).stream().map(QuestClaim::source).toList()
+        );
+        assertEquals(
+            List.of(
+                QuestClaimType.DELIVERED_BLOCKS,
+                QuestClaimType.RETURNED_REWARD,
+                QuestClaimType.RETURNED_REWARD
+            ),
+            service.claimsFor(issuer).stream().map(QuestClaim::type).toList()
+        );
+    }
+
+    @Test
+    void failedExpirationPersistsNothingAndCanBeRetriedWithoutDuplication() throws Exception {
+        MemoryQuestRepository repository = new MemoryQuestRepository();
+        QuestService service = new QuestService(repository);
+        Quest quest = create(service, UUID.randomUUID());
+        repository.fail = true;
+
+        assertThrows(IOException.class, () -> service.expire(quest.expiresAt()));
+        assertEquals(QuestStatus.ACTIVE, service.state().quests().get(quest.id()).status());
+        assertTrue(service.claimsFor(quest.issuerId()).isEmpty());
+        assertTrue(service.pendingNotifications(quest.issuerId()).isEmpty());
+
+        repository.fail = false;
+        service.expire(quest.expiresAt());
+        service.expire(quest.expiresAt());
+        assertEquals(1, service.claimsFor(quest.issuerId()).size());
+        assertEquals(1, service.pendingNotifications(quest.issuerId()).size());
+    }
+
+    private static Quest create(QuestService service, UUID issuer) throws IOException {
+        return service.create(
+            issuer, "Issuer", "STONE", 1,
+            List.of(new EscrowItem("DIAMOND", 3, null)), Instant.EPOCH
+        );
+    }
+
+    private static final class MemoryQuestRepository implements QuestRepository {
+        private QuestState state = QuestState.empty();
+        private boolean fail;
+
+        @Override public QuestState load() { return state; }
+
+        @Override
+        public void save(QuestState candidate) throws IOException {
+            if (fail) {
+                throw new IOException("disk full");
+            }
+            state = candidate;
+        }
+    }
+}

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

@@ -0,0 +1,44 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.time.Clock;
+import java.time.Instant;
+import java.time.ZoneOffset;
+import java.util.List;
+import java.util.UUID;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.logging.Logger;
+import org.junit.jupiter.api.Test;
+
+final class QuestExpiryTaskTest {
+    @Test
+    void scheduledPassExpiresDueQuestAndRequestsImmediateOnlineNotification() throws Exception {
+        Instant boundary = Instant.parse("2026-09-12T03:00:00Z");
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        service.create(
+            issuer, "Issuer", "STONE", 1,
+            List.of(new EscrowItem("DIAMOND", 1, null)),
+            boundary.minusSeconds(604800)
+        );
+        AtomicReference<UUID> notified = new AtomicReference<>();
+        QuestExpiryTask task = new QuestExpiryTask(
+            service, notified::set, Clock.fixed(boundary, ZoneOffset.UTC),
+            Logger.getAnonymousLogger()
+        );
+
+        task.run();
+
+        assertEquals(issuer, notified.get());
+        assertEquals(1, service.pendingNotifications(issuer).size());
+        assertEquals(QuestStatus.EXPIRED, service.state().quests().values().iterator().next().status());
+    }
+
+    private static final class Repository implements QuestRepository {
+        private QuestState state = QuestState.empty();
+        @Override public QuestState load() { return state; }
+        @Override public void save(QuestState candidate) { state = candidate; }
+    }
+}

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

@@ -93,6 +93,74 @@ final class YamlQuestRepositoryTest {
         assertTrue(Files.readString(path).contains("status: COMPLETED"));
     }
 
+    @Test
+    void roundTripsClaimsAndPendingNotificationsWhileOldFilesDefaultThemEmpty() throws Exception {
+        Path path = temporaryDirectory.resolve("quests.yml");
+        YamlQuestRepository repository = new YamlQuestRepository(path);
+        UUID issuer = UUID.randomUUID();
+        UUID questId = UUID.randomUUID();
+        Quest quest = new Quest(
+            questId, issuer, "Issuer", "STONE", 2,
+            List.of(new EscrowItem("DIAMOND", 1, null)),
+            Instant.parse("2026-09-05T03:00:00Z"),
+            Instant.parse("2026-09-12T03:00:00Z"), QuestStatus.COMPLETED
+        );
+        QuestClaim claim = new QuestClaim(
+            UUID.randomUUID(), questId, issuer,
+            List.of(new EscrowItem("STONE", 2, null)),
+            Instant.parse("2026-09-05T03:01:00Z")
+        );
+        IssuerNotification notification = new IssuerNotification(
+            UUID.randomUUID(), questId, issuer, "Your delivery can be claimed.",
+            Instant.parse("2026-09-05T03:01:00Z")
+        );
+        QuestState expected = new QuestState(
+            Map.of(questId, quest), Map.of(issuer, List.of(claim)),
+            Map.of(notification.id(), notification)
+        );
+
+        repository.save(expected);
+
+        assertEquals(expected, repository.load());
+        String yaml = Files.readString(path);
+        assertTrue(yaml.contains("claims:"));
+        assertTrue(yaml.contains("source: COMPLETION"));
+        assertTrue(yaml.contains("notifications:"));
+    }
+
+    @Test
+    void sourceLessHistoricalClaimsInferTypeFromQuestLifecycle() throws Exception {
+        Path path = temporaryDirectory.resolve("quests.yml");
+        Files.writeString(path, """
+            quests:
+            - id: 00000000-0000-0000-0000-000000000010
+              issuer-id: 00000000-0000-0000-0000-000000000001
+              issuer-name: Issuer
+              requested-material: STONE
+              requested-amount: 1
+              created-at: '2026-09-05T03:00:00Z'
+              expires-at: '2026-09-12T03:00:00Z'
+              status: CANCELLED
+              reward:
+              - material: DIAMOND
+                amount: 1
+            claims:
+            - id: 00000000-0000-0000-0000-000000000020
+              quest-id: 00000000-0000-0000-0000-000000000010
+              owner-id: 00000000-0000-0000-0000-000000000001
+              created-at: '2026-09-05T04:00:00Z'
+              items:
+              - material: DIAMOND
+                amount: 1
+            """);
+
+        QuestClaim claim = new YamlQuestRepository(path).load().claims().values()
+            .iterator().next().getFirst();
+
+        assertEquals(QuestClaimSource.CANCELLATION, claim.source());
+        assertEquals(QuestClaimType.RETURNED_REWARD, claim.type());
+    }
+
     @Test
     void malformedStateIsRejectedRatherThanPartiallyLoaded() throws Exception {
         Path path = temporaryDirectory.resolve("quests.yml");