diff --git a/TODO.md b/TODO.md
index 33d92c8..a3b84b0 100644
--- a/TODO.md
+++ b/TODO.md
@@ -38,3 +38,4 @@
 - ❌ Target trait updates beyond just visible; e.g. others don't need to know
   about inventory change
 - ❌ afterDestructionTickers shouldn't exist... destruction should be deferred
+- ❌ Remove position pack check from trait and add to Vector
diff --git a/packages/entity/entity.synchronized.js b/packages/entity/entity.synchronized.js
index 3d459b1..66d7b50 100644
--- a/packages/entity/entity.synchronized.js
+++ b/packages/entity/entity.synchronized.js
@@ -13,6 +13,7 @@ import {Resource} from '@avocado/resource';
 
 import {EntityCreatePacket} from './packets/entity-create.packet';
 import {hasTrait, lookupTrait} from './trait/registry';
+import {EntityUpdateTraitPacket} from './packets/entity-update-trait.packet';
 
 const debug = D('@avocado:entity:traits');
 
@@ -107,6 +108,7 @@ export class Entity extends decorate(Resource) {
     this.tick = this.tick.bind(this);
     // Fast props.
     this.numericUid = numericUid++;
+    this.instanceUuid = this.numericUid;
     this.position = [0, 0];
     this.room = null;
     this.visibleAabb = [0, 0, 0, 0];
@@ -117,6 +119,15 @@ export class Entity extends decorate(Resource) {
   }
 
   acceptPacket(packet) {
+    if (packet instanceof EntityUpdateTraitPacket) {
+      const {traits} = packet.data;
+      for (let i = 0; i < traits.length; i++) {
+        const {type, packets} = traits[i];
+        for (let j = 0; j < packets.length; j++) {
+          this._traits[type].acceptPacket(packets[j]);
+        }
+      }
+    }
   }
 
   addTrait(type, json = {}) {
@@ -194,6 +205,12 @@ export class Entity extends decorate(Resource) {
     return Object.keys(this._traits);
   }
 
+  cleanPackets() {
+    for (let i = 0; i < this._traitsFlat.length; i++) {
+      this._traitsFlat[i].cleanPackets();
+    }
+  }
+
   fromJSON(json) {
     super.fromJSON(json);
     if (json.instanceUuid) {
@@ -262,6 +279,25 @@ export class Entity extends decorate(Resource) {
 
   packets(informed) {
     const packets = [];
+    const updates = [];
+    for (const type in this._traits) {
+      const traitPackets = this._traits[type].packets(informed);
+      if (traitPackets.length > 0) {
+        updates.push({
+          type,
+          packets: traitPackets,
+        });
+      }
+    }
+    if (updates.length > 0) {
+      packets.push(new EntityUpdateTraitPacket({
+        synchronized: {
+          id: 0,
+          type: 0,
+        },
+        traits: updates,
+      }));
+    }
     return packets;
   }
 
@@ -335,6 +371,10 @@ export class Entity extends decorate(Resource) {
     types.forEach((type) => this.removeTrait(type));
   }
 
+  synchronizationId() {
+    return this.instanceUuid;
+  }
+
   tick(elapsed) {
     for (let i = 0; i < this._traitTickers.length; i++) {
       this._traitTickers[i](elapsed);
@@ -348,7 +388,7 @@ export class Entity extends decorate(Resource) {
     }
     return {
       ...super.toJSON(),
-      instanceUuid: this.numericUid,
+      instanceUuid: this.instanceUuid,
       traits: json,
     };
   }
diff --git a/packages/entity/index.js b/packages/entity/index.js
index fd9855e..e58c534 100644
--- a/packages/entity/index.js
+++ b/packages/entity/index.js
@@ -4,6 +4,10 @@ export {EntityCreatePacket} from './packets/entity-create.packet';
 export {EntityRemovePacket} from './packets/entity-remove.packet';
 export {EntityPacket} from './packets/entity.packet';
 
+export {
+  EntityListUpdateEntityPacket,
+} from './packets/entity-list-update-entity.packet';
+
 export {EntityList, EntityListView} from './list';
 
 export {
diff --git a/packages/entity/list/index.js b/packages/entity/list/index.js
index 7d284ab..000f163 100644
--- a/packages/entity/list/index.js
+++ b/packages/entity/list/index.js
@@ -1,8 +1,7 @@
 import {compose, EventEmitter} from '@avocado/core';
 import {QuadTree, Rectangle, Vector} from '@avocado/math';
 
-import {EntityCreatePacket} from '../packets/entity-create.packet';
-import {EntityRemovePacket} from '../packets/entity-remove.packet';
+import {EntityListUpdateEntityPacket} from '../packets/entity-list-update-entity.packet';
 import {Entity} from '../entity.synchronized';
 
 const decorate = compose(
@@ -30,6 +29,18 @@ export class EntityList extends decorate(class {}) {
   }
 
   acceptPacket(packet) {
+    if (packet instanceof EntityListUpdateEntityPacket) {
+      for (let i = 0; i < packet.data.length; i++) {
+        const {uuid, packets} = packet.data[i];
+        // WHY ?
+        if (!this._entities[uuid]) {
+          continue;
+        }
+        for (let j = 0; j < packets.length; j++) {
+          this._entities[uuid].acceptPacket(packets[j]);
+        }
+      }
+    }
   }
 
   addEntity(entity) {
@@ -58,6 +69,12 @@ export class EntityList extends decorate(class {}) {
     this.emit('entityAdded', entity);
   }
 
+  cleanPackets() {
+    for (let i = 0; i < this._flatEntities.length; i++) {
+      this._flatEntities[i].cleanPackets();
+    }
+  }
+
   destroy() {
     for (let i = 0; i < this._flatEntities.length; i++) {
       this._flatEntities[i].destroy();
@@ -86,6 +103,20 @@ export class EntityList extends decorate(class {}) {
 
   packets(informed) {
     const packets = [];
+    const updates = [];
+    for (const uuid in this._entities) {
+      const entity = this._entities[uuid];
+      const entityPackets = entity.packets(informed);
+      if (entityPackets.length > 0) {
+        updates.push({
+          uuid: entity.instanceUuid,
+          packets: entityPackets,
+        });
+      }
+    }
+    if (updates.length > 0) {
+      packets.push(new EntityListUpdateEntityPacket(updates));
+    }
     return packets;
   }
 
diff --git a/packages/entity/packets/entity-list-update-entity.packet.js b/packages/entity/packets/entity-list-update-entity.packet.js
new file mode 100644
index 0000000..3f5a271
--- /dev/null
+++ b/packages/entity/packets/entity-list-update-entity.packet.js
@@ -0,0 +1,35 @@
+import {BundlePacket, Packet} from '@avocado/net';
+
+export class EntityListUpdateEntityPacket extends Packet {
+
+  static pack(packet) {
+    const data = packet.data[1];
+    for (let i = 0; i < data.length; i++) {
+      data[i].packets = BundlePacket.packPacket(
+        new BundlePacket(data[i].packets)
+      );
+    }
+    return super.pack(packet);
+  }
+
+  static get schema() {
+    return {
+      ...super.schema,
+      data: [
+        {
+          uuid: 'uint32',
+          packets: 'buffer',
+        },
+      ],
+    };
+  }
+
+  static unpack(packet) {
+    const data = super.unpack(packet);
+    for (let i = 0; i < data.length; i++) {
+      data[i].packets = BundlePacket.unpack(data[i].packets);
+    }
+    return data;
+  }
+
+}
diff --git a/packages/entity/packets/entity-update-trait.packet.js b/packages/entity/packets/entity-update-trait.packet.js
new file mode 100644
index 0000000..d2a3dec
--- /dev/null
+++ b/packages/entity/packets/entity-update-trait.packet.js
@@ -0,0 +1,34 @@
+import {BundlePacket, SynchronizedUpdatePacket} from '@avocado/net';
+
+export class EntityUpdateTraitPacket extends SynchronizedUpdatePacket {
+
+  static pack(packet) {
+    const data = packet.data[1];
+    for (let i = 0; i < data.traits.length; i++) {
+      data.traits[i].packets = BundlePacket.packPacket(
+        new BundlePacket(data.traits[i].packets)
+      );
+    }
+    return super.pack(packet);
+  }
+
+  static get synchronizationSchema() {
+    return {
+      traits: [
+        {
+          type: 'string',
+          packets: 'buffer',
+        },
+      ],
+    };
+  }
+
+  static unpack(packet) {
+    const data = super.unpack(packet);
+    for (let i = 0; i < data.traits.length; i++) {
+      data.traits[i].packets = BundlePacket.unpack(data.traits[i].packets);
+    }
+    return data;
+  }
+
+}
diff --git a/packages/entity/packets/trait-positioned.packet.js b/packages/entity/packets/trait-positioned.packet.js
deleted file mode 100644
index cc06c7d..0000000
--- a/packages/entity/packets/trait-positioned.packet.js
+++ /dev/null
@@ -1,11 +0,0 @@
-import {EntityPacket} from './entity.packet';
-
-export class TraitPositionedPacket extends EntityPacket {
-
-  static get schema() {
-    const schema = super.schema;
-    schema.data.position = 'uint32';
-    return schema;
-  }
-
-}
diff --git a/packages/entity/packets/trait-update-positioned-position.packet.js b/packages/entity/packets/trait-update-positioned-position.packet.js
new file mode 100644
index 0000000..68d240f
--- /dev/null
+++ b/packages/entity/packets/trait-update-positioned-position.packet.js
@@ -0,0 +1,27 @@
+import {Vector} from '@avocado/math';
+import {Packet} from '@avocado/net';
+
+export class TraitUpdatePositionedPositionPacket extends Packet {
+
+  static pack(packet) {
+    const data = packet.data[1];
+    data.position = Vector.packToUint32(data.position);
+    return super.pack(packet);
+  }
+
+  static get schema() {
+    return {
+      ...super.schema,
+      data: {
+        position: 'uint32',
+      },
+    };
+  }
+
+  static unpack(packet) {
+    const data = super.unpack(packet);
+    data.position = Vector.unpackFromUint32(data.position);
+    return data;
+  }
+
+}
diff --git a/packages/entity/trait/index.js b/packages/entity/trait/index.js
index 441b5dd..76b1483 100644
--- a/packages/entity/trait/index.js
+++ b/packages/entity/trait/index.js
@@ -1,7 +1,9 @@
 import {compose, merge, mergeDiff, Property} from '@avocado/core';
 import {Vector} from '@avocado/math';
+import {SynchronizedMixin} from '@avocado/net';
 
 const decorate = compose(
+  SynchronizedMixin,
 );
 
 export class Trait extends decorate(class {}) {
@@ -25,6 +27,9 @@ export class Trait extends decorate(class {}) {
   acceptPacket(packet) {
   }
 
+  cleanPackets() {
+  }
+
   static contextType() {
     return {};
   }
@@ -106,6 +111,10 @@ export class Trait extends decorate(class {}) {
     return packets;
   }
 
+  packetsAreIdempotent() {
+    return false;
+  }
+
   toJSON() {
     return {
       params: this.params,
diff --git a/packages/entity/traits/positioned.trait.js b/packages/entity/traits/positioned.trait.js
index 4befea1..f65cb58 100644
--- a/packages/entity/traits/positioned.trait.js
+++ b/packages/entity/traits/positioned.trait.js
@@ -2,7 +2,7 @@ import {compose, EventEmitter} from '@avocado/core';
 import {Vector} from '@avocado/math';
 
 import {Trait} from '../trait';
-import {TraitPositionedPacket} from '../packets/trait-positioned.packet';
+import {TraitUpdatePositionedPositionPacket} from '../packets/trait-update-positioned-position.packet';
 
 const decorate = compose(
   EventEmitter,
@@ -31,9 +31,10 @@ export class Positioned extends decorate(Trait) {
   constructor(entity, params, state) {
     super(entity, params, state);
     this.on('_positionChanged', this.on_positionChanged, this);
-    const x = this.state.x >> 2;
-    const y = this.state.y >> 2;
+    const x = this.state.x;
+    const y = this.state.y;
     this._position = [x, y];
+    this._positionChanged = false;
     this.entity.position[0] = x;
     this.entity.position[1] = y;
     if (AVOCADO_CLIENT) {
@@ -44,6 +45,10 @@ export class Positioned extends decorate(Trait) {
     }
   }
 
+  cleanPackets() {
+    this._positionChanged = false;
+  }
+
   destroy() {
     this.off('_positionChanged', this.on_positionChanged);
     if (AVOCADO_CLIENT) {
@@ -52,9 +57,8 @@ export class Positioned extends decorate(Trait) {
   }
 
   acceptPacket(packet) {
-    if (packet instanceof TraitPositionedPacket) {
-      this.serverX = (packet.data.position & 0xFFFF) >> 2;
-      this.serverY = (packet.data.position >> 16) >> 2;
+    if (packet instanceof TraitUpdatePositionedPositionPacket) {
+      [this.serverX, this.serverY] = packet.data.position;
     }
   }
 
@@ -62,8 +66,9 @@ export class Positioned extends decorate(Trait) {
     this.entity.position[0] = newPosition[0];
     this.entity.position[1] = newPosition[1];
     if (AVOCADO_SERVER) {
-      this.state.x = newPosition[0] << 2;
-      this.state.y = newPosition[1] << 2;
+      this.state.x = newPosition[0];
+      this.state.y = newPosition[1];
+      this._positionChanged = true;
     }
     this.entity.emit('positionChanged', oldPosition, newPosition);
   }
@@ -72,19 +77,17 @@ export class Positioned extends decorate(Trait) {
     this.serverPositionDirty = true;
   }
 
-  packetsForUpdate() {
+  packets(informed) {
     const packets = [];
-    if (this.isDirty) {
+    if (this._positionChanged) {
       // Physics slop can end us up with negatives. Don't allow them in the
       // packed representation, even though it means a slight loss in accuracy.
       // The world bounds will (should!) keep things *eventually* correct.
       const x = Math.max(0, this.state.x);
       const y = Math.max(0, this.state.y);
-      const packed = (y << 16) | (x << 0);
-      packets.push(new TraitPositionedPacket({
-        position: packed,
+      packets.push(new TraitUpdatePositionedPositionPacket({
+        position: [x, y],
       }, this.entity));
-      this.makeClean();
     }
     return packets;
   }
diff --git a/packages/entity/traits/spawner.trait.js b/packages/entity/traits/spawner.trait.js
index 256e95e..f5bdbb0 100644
--- a/packages/entity/traits/spawner.trait.js
+++ b/packages/entity/traits/spawner.trait.js
@@ -115,8 +115,8 @@ export class Spawner extends decorate(Trait) {
         if (!json.traits.positioned.state) {
           json.traits.positioned.state = {};
         }
-        json.traits.positioned.state.x = position[0] << 2;
-        json.traits.positioned.state.y = position[1] << 2;
+        json.traits.positioned.state.x = position[0];
+        json.traits.positioned.state.y = position[1];
         return this.entity.spawn(key, json);
       },
 
diff --git a/packages/net/packet/bundle.packet.js b/packages/net/packet/bundle.packet.js
index a471c8c..6bab772 100644
--- a/packages/net/packet/bundle.packet.js
+++ b/packages/net/packet/bundle.packet.js
@@ -32,10 +32,8 @@ export class BundlePacket extends Packet {
       packedPacket.copy(buffer, caret, 0);
       caret += packedPacket.length;
     }
-    return this.builder.encode({
-      _id: packet.data[0],
-      data: buffer,
-    });
+    packet.data[1] = buffer;
+    return super.pack(packet);
   }
 
   static get schema() {
@@ -46,16 +44,19 @@ export class BundlePacket extends Packet {
   }
 
   static unpack(packet) {
-    const {data} = this.builder.decode(packet);
+    const data = super.unpack(packet)
     const packets = [];
     let caret = 0;
     while (caret < data.length) {
       // Read packed length.
       const length = data.readUInt32LE(caret);
       caret += 4;
-      // Read packed data.
-      const packedPacket = Buffer.from(data.buffer, caret, length);
-      caret += length;
+      // Read packed data. TODO: manual blitting sucks...
+      const packedPacket = Buffer.allocUnsafe(length);
+      let i = 0;
+      while (i < length) {
+        packedPacket.writeUInt8(data.readUInt8(caret++), i++);
+      }
       // Lookup packet.
       const packetId = packedPacket.readUInt8(0);
       const Packet = packetFromId(packetId);
diff --git a/packages/net/s13n/synchronized.js b/packages/net/s13n/synchronized.js
index 1e3e258..804ca8a 100644
--- a/packages/net/s13n/synchronized.js
+++ b/packages/net/s13n/synchronized.js
@@ -17,7 +17,9 @@ export function SynchronizedMixin(Superclass) {
       this.fromJSON(json);
     }
 
-    packets(informed) {}
+    packets(informed) {
+      return [];
+    }
 
     packetsAreIdempotent() {
       return true;
diff --git a/packages/topdown/layer.js b/packages/topdown/layer.js
index 03400ea..edd392d 100644
--- a/packages/topdown/layer.js
+++ b/packages/topdown/layer.js
@@ -1,5 +1,10 @@
 import {compose, EventEmitter, Property} from '@avocado/core';
-import {Entity, EntityCreatePacket, EntityList} from '@avocado/entity';
+import {
+  Entity,
+  EntityCreatePacket,
+  EntityList,
+  EntityListUpdateEntityPacket,
+} from '@avocado/entity';
 import {Vector} from '@avocado/math';
 import {ShapeList} from '@avocado/physics';
 
@@ -50,6 +55,9 @@ export class Layer extends decorate(class {}) {
     if (packet instanceof LayerUpdateTilesetUriPacket) {
       this.tilesetUri = packet.data;
     }
+    if (packet instanceof EntityListUpdateEntityPacket) {
+      this.entityList.acceptPacket(packet);
+    }
   }
 
   addEntity(entity) {
@@ -100,6 +108,7 @@ export class Layer extends decorate(class {}) {
 
   cleanPackets() {
     this._tilesetUriChanged = false;
+    this.entityList.cleanPackets();
   }
 
   destroy() {
@@ -202,6 +211,10 @@ export class Layer extends decorate(class {}) {
     if (this._tilesetUriChanged) {
       packets.push(new LayerUpdateTilesetUriPacket(this.tilesetUri));
     }
+    const entityListPackets = this.entityList.packets(informed);
+    for (let i = 0; i < entityListPackets.length; i++) {
+      packets.push(entityListPackets[i]);
+    }
     return packets;
   }
 
diff --git a/packages/topdown/packets/layers-update-layer.packet.js b/packages/topdown/packets/layers-update-layer.packet.js
index 23b2ecf..29cba04 100644
--- a/packages/topdown/packets/layers-update-layer.packet.js
+++ b/packages/topdown/packets/layers-update-layer.packet.js
@@ -14,6 +14,7 @@ export class LayersUpdateLayerPacket extends Packet {
 
   static get schema() {
     return {
+      ...super.schema,
       data: [
         {
           layerIndex: 'uint8',