17 files changed, 371 insertions, 34 deletions

diff --git a/service/src/main/java/market/guess/service/catalog/LocalCatalogContext.java b/service/src/main/java/market/guess/service/catalog/LocalCatalogContext.java
index 7a32e62..270aadd 100644
--- a/service/src/main/java/market/guess/service/catalog/LocalCatalogContext.java
+++ b/service/src/main/java/market/guess/service/catalog/LocalCatalogContext.java
@@ -48,7 +48,7 @@ public final class LocalCatalogContext implements CatalogContext {
   @Override
   public Result<Void> saveState(Path path) {
     try {
-      context.save();
+      context.save(path);
     } catch (Exception e) {
       return Result.error("Failed to save.", e.getMessage());
     }
@@ -58,7 +58,7 @@ public final class LocalCatalogContext implements CatalogContext {
   @Override
   public Result<LoadResult> restoreState(Path path) {
     try {
-      context.load();
+      context.load(path);
     } catch (Exception e) {
       return Result.error("Failed to load.", e.getMessage());
     }
diff --git a/service/src/main/java/market/guess/service/catalog/infrastructure/MarketContext.java b/service/src/main/java/market/guess/service/catalog/infrastructure/MarketContext.java
index 24521ef..cb2b467 100644
--- a/service/src/main/java/market/guess/service/catalog/infrastructure/MarketContext.java
+++ b/service/src/main/java/market/guess/service/catalog/infrastructure/MarketContext.java
@@ -7,15 +7,24 @@ import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
-import java.nio.file.Paths;
 import java.time.Instant;
 import java.util.List;
 import market.guess.exception.GuessMarketException;
+import market.guess.service.catalog.infrastructure.adapter.EventDeserializer;
 import market.guess.service.catalog.infrastructure.adapter.InstantTypeAdapter;
+import market.guess.service.catalog.infrastructure.adapter.LedgerDeserializer;
+import market.guess.service.catalog.infrastructure.adapter.LmsrTradingMechanismAdapter;
+import market.guess.service.catalog.infrastructure.adapter.MarketDeserializer;
+import market.guess.service.catalog.infrastructure.adapter.TradingMechanismAdapter;
+import market.guess.service.catalog.infrastructure.adapter.UserDeserializer;
 import market.guess.service.catalog.infrastructure.repository.EventRepository;
 import market.guess.service.catalog.infrastructure.repository.UserRepository;
 import market.guess.service.domain.Event;
+import market.guess.service.domain.Market;
 import market.guess.service.domain.User;
+import market.guess.service.ledger.Ledger;
+import market.guess.service.mechanism.LmsrTradingMechanism;
+import market.guess.service.mechanism.TradingMechanism;
 
 public final class MarketContext {
   record Wrapper(List<Event> events, List<User> users) {}
@@ -26,6 +35,12 @@ public final class MarketContext {
   private static final Gson GSON =
       new GsonBuilder()
           .registerTypeAdapter(Instant.class, new InstantTypeAdapter())
+          .registerTypeAdapter(Event.class, new EventDeserializer())
+          .registerTypeAdapter(Market.class, new MarketDeserializer())
+          .registerTypeAdapter(Ledger.class, new LedgerDeserializer())
+          .registerTypeAdapter(TradingMechanism.class, new TradingMechanismAdapter())
+          .registerTypeAdapter(LmsrTradingMechanism.class, new LmsrTradingMechanismAdapter())
+          .registerTypeAdapter(User.class, new UserDeserializer())
           .setPrettyPrinting()
           .create();
 
@@ -42,23 +57,25 @@ public final class MarketContext {
     return users;
   }
 
-  public void save() throws GuessMarketException {
-    var path = Paths.get("test-file.json");
+  public void save(Path path) throws GuessMarketException {
+    var target = withJsonExtension(path);
 
     try {
-      if (path.getParent() != null) Files.createDirectories(path.getParent());
+      if (target.getParent() != null) Files.createDirectories(target.getParent());
       Files.writeString(
-          path, GSON.toJson(new Wrapper(events.getAll(), users.getAll())), StandardCharsets.UTF_8);
-    } catch (IOException e) {
+          target,
+          GSON.toJson(new Wrapper(events.getAll(), users.getAll())),
+          StandardCharsets.UTF_8);
+    } catch (Exception e) {
       throw new GuessMarketException("Failed to sove the file.");
     }
   }
 
-  public void load() throws GuessMarketException {
+  public void load(Path path) throws GuessMarketException {
     try {
       var wrapper =
           GSON.fromJson(
-              Files.readString(Path.of("test-file.json"), StandardCharsets.UTF_8), Wrapper.class);
+              Files.readString(withJsonExtension(path), StandardCharsets.UTF_8), Wrapper.class);
       events.clear();
       users.clear();
 
@@ -76,4 +93,9 @@ public final class MarketContext {
       throw new GuessMarketException("Unable the file.");
     }
   }
+
+  private static Path withJsonExtension(Path path) {
+    var name = path.getFileName().toString();
+    return name.endsWith(".json") ? path : path.resolveSibling(name + ".json");
+  }
 }
diff --git a/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/EventDeserializer.java b/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/EventDeserializer.java
new file mode 100644
index 0000000..69a8447
--- /dev/null
+++ b/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/EventDeserializer.java
@@ -0,0 +1,51 @@
+package market.guess.service.catalog.infrastructure.adapter;
+
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParseException;
+import com.google.gson.reflect.TypeToken;
+import java.lang.reflect.Type;
+import java.util.List;
+import market.guess.api.CommissionTiming;
+import market.guess.model.event.EventStatus;
+import market.guess.service.domain.Event;
+import market.guess.service.domain.Market;
+import market.guess.service.domain.Trade;
+import market.guess.service.ledger.Ledger;
+import market.guess.service.mechanism.TradingMechanism;
+
+/**
+ * Rebuilds an Event through its constructor instead of Gson's default reflective field-setting,
+ * since Event's fields are final and reflective mutation of final fields is being phased out.
+ */
+public final class EventDeserializer implements JsonDeserializer<Event> {
+  @Override
+  public Event deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
+      throws JsonParseException {
+    var obj = json.getAsJsonObject();
+    Ledger ledger = context.deserialize(obj.get("ledger"), Ledger.class);
+    List<Market> markets =
+        context.deserialize(obj.get("markets"), new TypeToken<List<Market>>() {}.getType());
+    List<Trade> trades =
+        context.deserialize(obj.get("trades"), new TypeToken<List<Trade>>() {}.getType());
+    var winningOptionKey = obj.get("winningOptionKey");
+
+    return new Event(
+        obj.get("eventKey").getAsString(),
+        obj.get("displayId").getAsInt(),
+        obj.get("name").getAsString(),
+        obj.get("description").getAsString(),
+        obj.get("commissionPercent").getAsInt(),
+        context.deserialize(obj.get("commissionTiming"), CommissionTiming.class),
+        context.deserialize(obj.get("mechanism"), TradingMechanism.class),
+        markets,
+        obj.get("marketMaker").getAsString(),
+        ledger,
+        obj.get("runningId").getAsInt(),
+        trades,
+        context.deserialize(obj.get("state"), EventStatus.class),
+        winningOptionKey == null || winningOptionKey.isJsonNull() ? null : winningOptionKey.getAsString(),
+        obj.get("settlementCommission").getAsBigDecimal());
+  }
+}
diff --git a/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/LedgerDeserializer.java b/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/LedgerDeserializer.java
new file mode 100644
index 0000000..4b3a892
--- /dev/null
+++ b/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/LedgerDeserializer.java
@@ -0,0 +1,28 @@
+package market.guess.service.catalog.infrastructure.adapter;
+
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParseException;
+import com.google.gson.reflect.TypeToken;
+import java.lang.reflect.Type;
+import java.util.List;
+import market.guess.service.helpers.BigDecimalOptions;
+import market.guess.service.ledger.Ledger;
+import market.guess.service.ledger.LedgerEntry;
+
+/** Rebuilds a Ledger through its constructor and public record() method, avoiding reflection on its final fields. */
+public final class LedgerDeserializer implements JsonDeserializer<Ledger> {
+  @Override
+  public Ledger deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
+      throws JsonParseException {
+    var obj = json.getAsJsonObject();
+    var ledger = new Ledger(obj.get("owner").getAsString(), BigDecimalOptions.ZERO_MONEY);
+
+    List<LedgerEntry> entries =
+        context.deserialize(obj.get("entries"), new TypeToken<List<LedgerEntry>>() {}.getType());
+    entries.forEach(ledger::record);
+
+    return ledger;
+  }
+}
diff --git a/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/LmsrTradingMechanismAdapter.java b/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/LmsrTradingMechanismAdapter.java
new file mode 100644
index 0000000..c090cec
--- /dev/null
+++ b/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/LmsrTradingMechanismAdapter.java
@@ -0,0 +1,42 @@
+package market.guess.service.catalog.infrastructure.adapter;
+
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParseException;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
+import java.lang.reflect.Type;
+import java.time.Clock;
+import market.guess.service.mechanism.LmsrTradingMechanism;
+
+/**
+ * Rebuilds an LmsrTradingMechanism through its constructor, avoiding reflection on its final
+ * fields. The clock is a placeholder here; MarketContext reattaches the live one after load.
+ *
+ * <p>Also writes the type discriminator {@link TradingMechanismAdapter} reads, since Gson prefers
+ * a type adapter registered for an object's runtime type over one registered for its declared
+ * (interface) type, so the interface-level adapter never gets a chance to add it here.
+ */
+public final class LmsrTradingMechanismAdapter
+    implements JsonSerializer<LmsrTradingMechanism>, JsonDeserializer<LmsrTradingMechanism> {
+  @Override
+  public JsonElement serialize(
+      LmsrTradingMechanism src, Type typeOfSrc, JsonSerializationContext context) {
+    var json = new JsonObject();
+    json.addProperty(TradingMechanismAdapter.TYPE_FIELD, src.getType().name());
+    json.addProperty("liquidity", src.getLiquidity());
+    json.add("q", context.serialize(src.getQuantities()));
+    return json;
+  }
+
+  @Override
+  public LmsrTradingMechanism deserialize(
+      JsonElement json, Type typeOfT, JsonDeserializationContext context)
+      throws JsonParseException {
+    var obj = json.getAsJsonObject();
+    var q = context.<int[]>deserialize(obj.get("q"), int[].class);
+    return new LmsrTradingMechanism(obj.get("liquidity").getAsInt(), q, Clock.systemUTC());
+  }
+}
diff --git a/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/MarketDeserializer.java b/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/MarketDeserializer.java
new file mode 100644
index 0000000..6757292
--- /dev/null
+++ b/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/MarketDeserializer.java
@@ -0,0 +1,20 @@
+package market.guess.service.catalog.infrastructure.adapter;
+
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParseException;
+import java.lang.reflect.Type;
+import market.guess.service.domain.Market;
+
+/** Rebuilds a Market through its constructor and public mutator, avoiding reflection on its final fields. */
+public final class MarketDeserializer implements JsonDeserializer<Market> {
+  @Override
+  public Market deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
+      throws JsonParseException {
+    var obj = json.getAsJsonObject();
+    var market = new Market(obj.get("key").getAsString(), obj.get("name").getAsString());
+    market.addVolume(obj.get("volume").getAsLong());
+    return market;
+  }
+}
diff --git a/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/TradingMechanismAdapter.java b/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/TradingMechanismAdapter.java
new file mode 100644
index 0000000..ac3da8b
--- /dev/null
+++ b/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/TradingMechanismAdapter.java
@@ -0,0 +1,43 @@
+package market.guess.service.catalog.infrastructure.adapter;
+
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParseException;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
+import java.lang.reflect.Type;
+import market.guess.api.MechanismType;
+import market.guess.service.mechanism.LmsrTradingMechanism;
+import market.guess.service.mechanism.OrderBookTradingMechanism;
+import market.guess.service.mechanism.TradingMechanism;
+
+/**
+ * TradingMechanism is a sealed interface, so Gson can't tell which implementation to build from
+ * the JSON alone; this tags the JSON with a type discriminator and dispatches on it.
+ */
+public final class TradingMechanismAdapter
+    implements JsonSerializer<TradingMechanism>, JsonDeserializer<TradingMechanism> {
+  static final String TYPE_FIELD = "mechanismType";
+
+  @Override
+  public JsonElement serialize(
+      TradingMechanism src, Type typeOfSrc, JsonSerializationContext context) {
+    var json = context.serialize(src, src.getClass()).getAsJsonObject();
+    json.addProperty(TYPE_FIELD, src.getType().name());
+    return json;
+  }
+
+  @Override
+  public TradingMechanism deserialize(
+      JsonElement json, Type typeOfT, JsonDeserializationContext context)
+      throws JsonParseException {
+    var obj = json.getAsJsonObject();
+    var type = MechanismType.valueOf(obj.get(TYPE_FIELD).getAsString());
+
+    return switch (type) {
+      case LMSR -> context.deserialize(obj, LmsrTradingMechanism.class);
+      case ORDER_BOOK -> context.deserialize(obj, OrderBookTradingMechanism.class);
+    };
+  }
+}
diff --git a/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/UserDeserializer.java b/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/UserDeserializer.java
new file mode 100644
index 0000000..e91620b
--- /dev/null
+++ b/service/src/main/java/market/guess/service/catalog/infrastructure/adapter/UserDeserializer.java
@@ -0,0 +1,20 @@
+package market.guess.service.catalog.infrastructure.adapter;
+
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParseException;
+import java.lang.reflect.Type;
+import market.guess.service.domain.User;
+import market.guess.service.ledger.Ledger;
+
+/** Rebuilds a User through its constructor instead of Gson's default reflective field-setting, since its fields are final. */
+public final class UserDeserializer implements JsonDeserializer<User> {
+  @Override
+  public User deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
+      throws JsonParseException {
+    var obj = json.getAsJsonObject();
+    Ledger account = context.deserialize(obj.get("account"), Ledger.class);
+    return new User(obj.get("name").getAsString(), account);
+  }
+}
diff --git a/service/src/main/java/market/guess/service/catalog/infrastructure/mapper/v1/EventMapperV1.java b/service/src/main/java/market/guess/service/catalog/infrastructure/mapper/v1/EventMapperV1.java
index 78fd550..f45eb46 100644
--- a/service/src/main/java/market/guess/service/catalog/infrastructure/mapper/v1/EventMapperV1.java
+++ b/service/src/main/java/market/guess/service/catalog/infrastructure/mapper/v1/EventMapperV1.java
@@ -26,8 +26,7 @@ public final class EventMapperV1 implements Mapper<GMEvent, Event> {
         new LmsrTradingMechanism(source.getGMMethod().getGMLMSR().getB(), options.size()),
         EventStatus.ACTIVE,
         options,
-        "Tester"); // ponytail: only user in this console app; swap for a real market-maker
-    // concept if multi-user support lands
+        "Tester");
   }
 
   private static String getEventKey(GMEvent event) {
diff --git a/service/src/main/java/market/guess/service/catalog/infrastructure/provider/v1/XMLLoaderV1.java b/service/src/main/java/market/guess/service/catalog/infrastructure/provider/v1/XMLLoaderV1.java
index 67d0b67..b97114d 100644
--- a/service/src/main/java/market/guess/service/catalog/infrastructure/provider/v1/XMLLoaderV1.java
+++ b/service/src/main/java/market/guess/service/catalog/infrastructure/provider/v1/XMLLoaderV1.java
@@ -20,13 +20,18 @@ public final class XMLLoaderV1 implements Loader {
   private final EventRepository eventRepository;
   private final UserRepository userRepository;
   private final EventMapperV1 mapper;
+  private final XMLValidatorV1 validator;
 
   public XMLLoaderV1(
-      EventRepository eventRepository, UserRepository userRepository, EventMapperV1 mapper) {
+      EventRepository eventRepository,
+      UserRepository userRepository,
+      EventMapperV1 mapper,
+      XMLValidatorV1 validator) {
     super();
     this.eventRepository = eventRepository;
     this.userRepository = userRepository;
     this.mapper = mapper;
+    this.validator = validator;
     try {
       context = JAXBContext.newInstance(GuessMarket.class);
     } catch (JAXBException e) {
@@ -36,14 +41,25 @@ public final class XMLLoaderV1 implements Loader {
 
   @Override
   public Result<LoadResult> load(Path path) {
+    if (!Files.isRegularFile(path)) {
+      return Result.error("FILE_NOT_FOUND", "No such file.");
+    }
+
     if (path.getFileName() == null
         || !path.getFileName().toString().toLowerCase().endsWith(".xml")) {
       return Result.error("NOT_XML", "The file must be an XML.");
     }
 
     try (var stream = Files.newInputStream(path)) {
-      var doc = (GuessMarket) context.createUnmarshaller().unmarshal(stream);
-      for (var event : doc.getGMEvents().getGMEvent()) {
+      var seed = (GuessMarket) context.createUnmarshaller().unmarshal(stream);
+
+      var validation = validator.validate(seed);
+
+      if (!validation.isSuccess()) {
+        return Result.error(validation.getMessage(), validation.getDetails());
+      }
+
+      for (var event : seed.getGMEvents().getGMEvent()) {
         eventRepository.add(mapper.toDomain(event));
       }
 
diff --git a/service/src/main/java/market/guess/service/catalog/infrastructure/provider/v1/XMLValidatorV1.java b/service/src/main/java/market/guess/service/catalog/infrastructure/provider/v1/XMLValidatorV1.java
new file mode 100644
index 0000000..567558a
--- /dev/null
+++ b/service/src/main/java/market/guess/service/catalog/infrastructure/provider/v1/XMLValidatorV1.java
@@ -0,0 +1,35 @@
+package market.guess.service.catalog.infrastructure.provider.v1;
+
+import java.util.HashSet;
+import market.guess.api.Result;
+import market.guess.service.catalog.model.v1.GuessMarket;
+
+public final class XMLValidatorV1 {
+  private static final int MIN_COMMISSION = 0;
+  private static final int MAX_COMMISSION = 90;
+
+  public Result<Void> validate(GuessMarket seed) {
+
+    var seenIds = new HashSet<Integer>();
+    var duplicated = new HashSet<Integer>();
+
+    for (var e : seed.getGMEvents().getGMEvent()) {
+
+      if (!seenIds.add(e.getId()) && duplicated.add(e.getId())) {
+        return Result.error(
+            "DUPLICATE_ID",
+            "Event id " + e.getId() + " appears more than once, every event id must be unique.");
+      }
+
+      var pct = e.getComision().getValue();
+      if (pct < MIN_COMMISSION || pct > MAX_COMMISSION) {
+        return Result.error(
+            "COMMISSION_OUT_OF_RANGE",
+            "Commission is %d%%, it must be between %d%% and %d%%."
+                .formatted(pct, MIN_COMMISSION, MAX_COMMISSION));
+      }
+    }
+
+    return Result.ok();
+  }
+}
diff --git a/service/src/main/java/market/guess/service/domain/Event.java b/service/src/main/java/market/guess/service/domain/Event.java
index 6089aa3..4c78486 100644
--- a/service/src/main/java/market/guess/service/domain/Event.java
+++ b/service/src/main/java/market/guess/service/domain/Event.java
@@ -57,6 +57,40 @@ public final class Event {
     this.state = status;
   }
 
+  /** Reconstructs an event with its full accumulated state, e.g. from a saved snapshot. */
+  public Event(
+      String eventKey,
+      int displayId,
+      String name,
+      String description,
+      int commissionPercent,
+      CommissionTiming commissionTiming,
+      TradingMechanism mechanism,
+      List<Market> markets,
+      String marketMaker,
+      Ledger ledger,
+      int runningId,
+      List<Trade> trades,
+      EventStatus state,
+      String winningOptionKey,
+      BigDecimal settlementCommission) {
+    this.eventKey = eventKey;
+    this.displayId = displayId;
+    this.name = name;
+    this.description = description;
+    this.commissionPercent = commissionPercent;
+    this.commissionTiming = commissionTiming;
+    this.mechanism = mechanism;
+    this.markets = markets;
+    this.marketMaker = marketMaker;
+    this.ledger = ledger;
+    this.runningId = runningId;
+    this.trades.addAll(trades);
+    this.state = state;
+    this.winningOptionKey = winningOptionKey;
+    this.settlementCommission = settlementCommission;
+  }
+
   public TradingMechanism getMechanism() {
     return mechanism;
   }
diff --git a/service/src/main/java/market/guess/service/domain/User.java b/service/src/main/java/market/guess/service/domain/User.java
index a00b1a0..86ba5af 100644
--- a/service/src/main/java/market/guess/service/domain/User.java
+++ b/service/src/main/java/market/guess/service/domain/User.java
@@ -17,6 +17,12 @@ public final class User {
     this.account = new Ledger(name, initialBalance);
   }
 
+  /** Reconstructs a user with its full accumulated ledger, e.g. from a saved snapshot. */
+  public User(String name, Ledger account) {
+    this.name = name;
+    this.account = account;
+  }
+
   public String getName() {
     return name;
   }
diff --git a/service/src/main/java/market/guess/service/matching/LocalMatchingEngine.java b/service/src/main/java/market/guess/service/matching/LocalMatchingEngine.java
index 6a815c8..22e5332 100644
--- a/service/src/main/java/market/guess/service/matching/LocalMatchingEngine.java
+++ b/service/src/main/java/market/guess/service/matching/LocalMatchingEngine.java
@@ -1,15 +1,22 @@
 package market.guess.service.matching;
 
+import java.time.Clock;
 import java.util.List;
 import market.guess.service.domain.Order;
 import market.guess.service.domain.Trade;
 
 public final class LocalMatchingEngine implements MatchingEngine {
+  private final Clock clock;
+
+  public LocalMatchingEngine(Clock clock) {
+    super();
+    this.clock = clock;
+  }
 
   @Override
   public List<Trade> match(Order order) {
     var mechanism = order.event().getMechanism();
-    return mechanism.buy(order.event(), order.market(), order.quantity());
+    return mechanism.buy(order.event(), order.market(), clock.instant(), order.quantity());
   }
 
   @Override
diff --git a/service/src/main/java/market/guess/service/mechanism/LmsrTradingMechanism.java b/service/src/main/java/market/guess/service/mechanism/LmsrTradingMechanism.java
index 87c5661..062a095 100644
--- a/service/src/main/java/market/guess/service/mechanism/LmsrTradingMechanism.java
+++ b/service/src/main/java/market/guess/service/mechanism/LmsrTradingMechanism.java
@@ -2,6 +2,7 @@ package market.guess.service.mechanism;
 
 import java.math.BigDecimal;
 import java.time.Clock;
+import java.time.Instant;
 import java.util.Arrays;
 import java.util.List;
 import market.guess.api.MechanismType;
@@ -14,17 +15,23 @@ public final class LmsrTradingMechanism implements TradingMechanism {
   private final int liquidity;
   private final int[] q;
 
-  private final Clock clock;
-
   public LmsrTradingMechanism(int liquidity, int optionCount) {
-    this(liquidity, optionCount, Clock.systemUTC());
+    this.q = new int[optionCount];
+    this.liquidity = liquidity;
   }
 
-  public LmsrTradingMechanism(int liquidity, int optionCount, Clock clock) {
+  public LmsrTradingMechanism(int liquidity, int[] q, Clock clock) {
     super();
     this.liquidity = liquidity;
-    this.q = new int[optionCount];
-    this.clock = clock;
+    this.q = q;
+  }
+
+  public int getLiquidity() {
+    return liquidity;
+  }
+
+  public int[] getQuantities() {
+    return q;
   }
 
   @Override
@@ -33,7 +40,7 @@ public final class LmsrTradingMechanism implements TradingMechanism {
   }
 
   @Override
-  public List<Trade> buy(Event event, Market market, long quantity) {
+  public List<Trade> buy(Event event, Market market, Instant at, long quantity) {
     var optionIndex = event.getMarkets().indexOf(market);
     var before = cost(q);
 
@@ -46,7 +53,7 @@ public final class LmsrTradingMechanism implements TradingMechanism {
     return List.of(
         new Trade(
             0,
-            clock.instant(),
+            at,
             null,
             market.getKey(),
             market.getName(),
diff --git a/service/src/main/java/market/guess/service/mechanism/OrderBookTradingMechanism.java b/service/src/main/java/market/guess/service/mechanism/OrderBookTradingMechanism.java
index 4e0dd0a..fd03750 100644
--- a/service/src/main/java/market/guess/service/mechanism/OrderBookTradingMechanism.java
+++ b/service/src/main/java/market/guess/service/mechanism/OrderBookTradingMechanism.java
@@ -2,6 +2,7 @@ package market.guess.service.mechanism;
 
 import java.math.BigDecimal;
 import java.math.RoundingMode;
+import java.time.Instant;
 import java.util.ArrayList;
 import java.util.List;
 import market.guess.api.MechanismType;
@@ -18,15 +19,15 @@ public final class OrderBookTradingMechanism implements TradingMechanism {
 
   private static final class RestingOrder {
     private final BigDecimal price;
-    private int quantity;
+    private long quantity;
 
-    private RestingOrder(BigDecimal price, int quantity) {
+    private RestingOrder(BigDecimal price, long quantity) {
       this.price = price;
       this.quantity = quantity;
     }
   }
 
-  private final boolean allowMint; // ponytail: mint deferred — cross-option matching, its own pass
+  private final boolean allowMint;
   private final int initial;
   private final int d;
   private final List<List<RestingOrder>>
@@ -56,17 +57,17 @@ public final class OrderBookTradingMechanism implements TradingMechanism {
   }
 
   @Override
-  public List<Trade> buy(Event event, Market market, long quantity) {
+  public List<Trade> buy(Event event, Market market, Instant at, long quantity) {
     var optionIndex = event.getMarkets().indexOf(market);
-    return List.of(match(optionIndex, Side.BUY, (int) quantity, null, false));
+    return List.of(match(optionIndex, Side.BUY, at, quantity, null, false));
   }
 
   /** Priced limit order — not on the shared interface, no engine call site yet. */
-  public Trade placeOrder(int optionIndex, Side side, int quantity, BigDecimal price) {
+  public Trade placeOrder(int optionIndex, Side side, Instant at, long quantity, BigDecimal price) {
     if (price.signum() < 0 || price.compareTo(BigDecimal.valueOf(d)) > 0) {
       throw new IllegalArgumentException("Price must be between 0 and " + d);
     }
-    return match(optionIndex, side, quantity, price, true);
+    return match(optionIndex, side, at, quantity, price, true);
   }
 
   @Override
@@ -97,7 +98,12 @@ public final class OrderBookTradingMechanism implements TradingMechanism {
   }
 
   private Trade match(
-      int optionIndex, Side side, int quantity, BigDecimal limitPrice, boolean restRemainder) {
+      int optionIndex,
+      Side side,
+      Instant at,
+      long quantity,
+      BigDecimal limitPrice,
+      boolean restRemainder) {
     var opposing = side == Side.BUY ? asks.get(optionIndex) : bids.get(optionIndex);
 
     var filled = 0;
@@ -127,7 +133,7 @@ public final class OrderBookTradingMechanism implements TradingMechanism {
     }
 
     return new Trade(
-        filled, null, null, null, null, filled, BigDecimalOptions.toMoney(proceeds), proceeds);
+        filled, at, null, null, null, filled, BigDecimalOptions.toMoney(proceeds), proceeds);
   }
 
   private static boolean crosses(Side side, BigDecimal restingPrice, BigDecimal limitPrice) {
diff --git a/service/src/main/java/market/guess/service/mechanism/TradingMechanism.java b/service/src/main/java/market/guess/service/mechanism/TradingMechanism.java
index 16a5c6f..6fc5a9a 100644
--- a/service/src/main/java/market/guess/service/mechanism/TradingMechanism.java
+++ b/service/src/main/java/market/guess/service/mechanism/TradingMechanism.java
@@ -1,6 +1,7 @@
 package market.guess.service.mechanism;
 
 import java.math.BigDecimal;
+import java.time.Instant;
 import java.util.List;
 import market.guess.api.MechanismType;
 import market.guess.service.domain.Event;
@@ -11,7 +12,7 @@ public sealed interface TradingMechanism permits LmsrTradingMechanism, OrderBook
 
   MechanismType getType();
 
-  List<Trade> buy(Event event, Market market, long quantity);
+  List<Trade> buy(Event event, Market market, Instant at, long quantity);
 
   BigDecimal[] prices();
 }