diff --git a/packages/entity/list.js b/packages/entity/list.js
index a646166..230ee2b 100644
--- a/packages/entity/list.js
+++ b/packages/entity/list.js
@@ -4,6 +4,7 @@ import mapValues from 'lodash.mapvalues';
 import {arrayUnique, compose} from '@avocado/core';
 import {QuadTree, Rectangle, Vector} from '@avocado/math';
 import {EventEmitter} from '@avocado/mixins';
+import {StateSynchronizer} from '@avocado/state';
 
 import {create} from './index';
 
@@ -56,26 +57,60 @@ export class EntityList extends decorate(class {}) {
   }
 
   patchState(patch) {
-    for (const uuid in patch) {
-      const localUuid = this.uuidMap_PRIVATE[uuid];
-      const entity = this.entities_PRIVATE[localUuid];
-      if (entity) {
-        if (false === patch[uuid]) {
-          // Entity removed.
-          this.removeEntity(entity);
-        }
-        else {
-          entity.patchState(patch[uuid]);
-          this.state_PRIVATE = this.state_PRIVATE.set(localUuid, entity.state);
+    for (const step of patch) {
+      const {op, path, value} = step;
+      if ('/' === path) {
+        for (const uuid in value) {
+          const localUuid = this.uuidMap_PRIVATE[uuid];
+          const entity = this.entities_PRIVATE[localUuid];
+          if (entity) {
+            if (false === value[uuid]) {
+              // Entity removed.
+              this.removeEntity(entity);
+            }
+            else {
+              entity.patchState([
+                {
+                  op: 'replace',
+                  path: '/',
+                  value: value[uuid],
+                }
+              ]);
+              this.state_PRIVATE = this.state_PRIVATE.set(localUuid, entity.state);
+            }
+          }
+          else {
+            // New entity. Create with patch as traits.
+            const newEntity = create().fromJSON({
+              traits: value[uuid],
+            });
+            this.uuidMap_PRIVATE[uuid] = newEntity.instanceUuid;
+            this.addEntity(newEntity);
+          }
         }
       }
       else {
-        // New entity. Create with patch as traits.
-        const newEntity = create().fromJSON({
-          traits: patch[uuid],
-        });
-        this.uuidMap_PRIVATE[uuid] = newEntity.instanceUuid;
-        this.addEntity(newEntity);
+        const [uuid, substep] = StateSynchronizer.forwardStep(step);
+        const localUuid = this.uuidMap_PRIVATE[uuid];
+        const entity = this.entities_PRIVATE[localUuid];
+        if (entity) {
+          if (false === substep.value[uuid]) {
+            // Entity removed.
+            this.removeEntity(entity);
+          }
+          else {
+            entity.patchState([substep]);
+            this.state_PRIVATE = this.state_PRIVATE.set(localUuid, entity.state);
+          }
+        }
+        else {
+          // New entity. Create with patch as traits.
+          const newEntity = create().fromJSON({
+            traits: substep.value[uuid],
+          });
+          this.uuidMap_PRIVATE[uuid] = newEntity.instanceUuid;
+          this.addEntity(newEntity);
+        }
       }
     }
   }
diff --git a/packages/entity/trait.js b/packages/entity/trait.js
index 4e38697..41c66e8 100644
--- a/packages/entity/trait.js
+++ b/packages/entity/trait.js
@@ -3,6 +3,7 @@ import * as I from 'immutable';
 import {Vector} from '@avocado/math';
 import {Property} from '@avocado/mixins';
 import {Resource} from '@avocado/resource';
+import {StateSynchronizer} from '@avocado/state';
 
 export class Trait {
 
@@ -38,20 +39,39 @@ export class Trait {
   }
 
   patchState(patch) {
-    if (!patch.state) {
-      return;
-    }
-    const undefinedProperties = {};
-    for (const key in patch.state) {
-      const value = patch.state[key];
-      if (key in this.entity) {
-        this.entity[key] = value;
+    for (const step of patch) {
+      const {op, path, value} = step;
+      if ('/' === path) {
+        if (!value.state) {
+          continue;
+        }
+        const undefinedProperties = {};
+        for (const key in value.state) {
+          const value = value.state[key];
+          if (key in this.entity) {
+            this.entity[key] = value;
+          }
+          else {
+            undefinedProperties[key] = value;
+          }
+        }
+        this.state = this.state.merge(undefinedProperties);
       }
       else {
-        undefinedProperties[key] = value;
+        const [stepKey, substep] = StateSynchronizer.forwardStep(step);
+        if ('state' === stepKey) {
+          const key = substep.path.substr(1);
+          const undefinedProperties = {};
+          if (key in this.entity) {
+            this.entity[key] = substep.value;
+          }
+          else {
+            undefinedProperties[key] = substep.value;
+          }
+          this.state = this.state.merge(undefinedProperties);
+        }
       }
     }
-    this.state = this.state.merge(undefinedProperties);
   }
 
   toJSON() {
diff --git a/packages/entity/traits.js b/packages/entity/traits.js
index 6b9b702..7a0259a 100644
--- a/packages/entity/traits.js
+++ b/packages/entity/traits.js
@@ -3,6 +3,7 @@ import without from 'lodash.without';
 import * as I from 'immutable';
 
 import {Resource} from '@avocado/resource';
+import {StateSynchronizer} from '@avocado/state';
 
 import {hasTrait, lookupTrait, registerTrait} from './trait-registry';
 
@@ -184,22 +185,51 @@ export class Traits {
   }
 
   patchState(patch) {
-    for (const type in patch) {
-      let instance = this.traits_PRIVATE[type];
-      // New trait requested?
-      if (!this.traits_PRIVATE[type]) {
-        // Doesn't exist?
-        if (!hasTrait(type)) {
-          continue;
+    for (const step of patch) {
+      const {op, path, value} = step;
+      if ('/' === path) {
+        for (const type in value) {
+          let instance = this.traits_PRIVATE[type];
+          // New trait requested?
+          if (!this.traits_PRIVATE[type]) {
+            // Doesn't exist?
+            if (!hasTrait(type)) {
+              continue;
+            }
+            this.addTrait(type, value[type]);
+            instance = this.traits_PRIVATE[type];
+          }
+          else {
+            // Accept state.
+            instance.patchState([
+              {
+                op: 'replace',
+                path: '/',
+                value: patch[type],
+              }
+            ]);
+          }
+          this._setInstanceState(type, instance);
         }
-        this.addTrait(type, patch[type]);
-        instance = this.traits_PRIVATE[type];
       }
       else {
-        // Accept state.
-        instance.patchState(patch[type]);
+        const [type, substep] = StateSynchronizer.forwardStep(step);
+        let instance = this.traits_PRIVATE[type];
+        // New trait requested?
+        if (!this.traits_PRIVATE[type]) {
+          // Doesn't exist?
+          if (!hasTrait(type)) {
+            continue;
+          }
+          this.addTrait(type, substep.value[type]);
+          instance = this.traits_PRIVATE[type];
+        }
+        else {
+          // Accept state.
+          instance.patchState([substep]);
+        }
+        this._setInstanceState(type, instance);
       }
-      this._setInstanceState(type, instance);
     }
   }
 
diff --git a/packages/state/synchronizer.js b/packages/state/synchronizer.js
index 6b64cc6..a8a8e9b 100644
--- a/packages/state/synchronizer.js
+++ b/packages/state/synchronizer.js
@@ -12,33 +12,19 @@ export class StateSynchronizer {
   diff(previousState) {
     // Take a pure JS diff.
     const steps = immutablediff(previousState, this._state).toJS();
-    const updateSteps = steps.filter(StateSynchronizer.isStepUpdate);
-    return StateSynchronizer.hydratePathValues(updateSteps);
+    return steps;
   }
 
-  static hydratePathValues(pathValues) {
-    let accumulated = {};
-    for (const {path, value} of pathValues) {
-      if ('/' === path) {
-        accumulated = value;
-      }
-      else {
-        const parts = path.split('/');
-        parts.shift();
-        let walk = accumulated;
-        for (let i = 0; i < parts.length; ++i) {
-          const part = parts[i];
-          walk[part] = walk[part] || {};
-          if (i === parts.length - 1) {
-            walk[part] = value;
-          }
-          else {
-            walk = walk[part];
-          }
-        }
-      }
-    }
-    return accumulated;
+  static forwardStep(step) {
+    const {path, op, value} = step;
+    const parts = path.split('/');
+    const [key] = parts.splice(1, 1);
+    const subpath = parts.join('/');
+    return [key, {
+      op,
+      path: subpath ? subpath : '/',
+      value,
+    }];
   }
 
   static isStepUpdate(step) {
@@ -46,12 +32,26 @@ export class StateSynchronizer {
   }
 
   patchState(patch) {
-    for (const key in patch) {
+    const stepMap = {};
+    for (const {op, path, value} of patch) {
+      const parts = path.split('/');
+      const [key] = parts.splice(1, 1);
+      if (!stepMap[key]) {
+        stepMap[key] = [];
+      }
+      const subpath = parts.join('/');
+      stepMap[key].push({
+        op,
+        path: subpath ? subpath : '/',
+        value,
+      });
+    }
+    for (const key in stepMap) {
       const stateful = this._statefuls[key];
       if (!stateful) {
         continue;
       }
-      stateful.patchState(patch[key]);
+      stateful.patchState(stepMap[key]);
     }
   }
 
diff --git a/packages/topdown/layer.js b/packages/topdown/layer.js
index 22c6ae9..17fcf46 100644
--- a/packages/topdown/layer.js
+++ b/packages/topdown/layer.js
@@ -3,6 +3,7 @@ import * as I from 'immutable';
 import {compose} from '@avocado/core';
 import {create as createEntity, EntityList} from '@avocado/entity';
 import {EventEmitter, Property} from '@avocado/mixins';
+import {StateSynchronizer} from '@avocado/state';
 
 import {Tiles} from './tiles';
 
@@ -81,14 +82,40 @@ export class Layer extends decorate(class {}) {
   }
 
   patchState(patch) {
-    if (patch.entityList) {
-      this.entityList.patchState(patch.entityList);
-    }
-    if (patch.tilesetUri) {
-      this.tilesetUri = patch.tilesetUri;
-    }
-    if (patch.tiles) {
-      this.tiles.patchState(patch.tiles);
+    for (const step of patch) {
+      const {op, path, value} = step;
+      if ('/' === path) {
+        if (value.entityList) {
+          this.entityList.patchState([
+            {
+              op: 'replace',
+              path: '/',
+              value: value.entityList
+            }
+          ]);
+        }
+        if (value.tilesetUri) {
+          this.tilesetUri = value.tilesetUri;
+        }
+        if (value.tiles) {
+          this.tiles.patchState([
+            {
+              op: 'replace',
+              path: '/',
+              value: value.tiles
+            }
+          ]);
+        }
+      }
+      else {
+        const [key, substep] = StateSynchronizer.forwardStep(step);
+        if ('entityList' === key) {
+          this.entityList.patchState([substep]);
+        }
+        if ('tiles' === key) {
+          this.tiles.patchState([substep]);
+        }
+      }
     }
   }
 
diff --git a/packages/topdown/layers.js b/packages/topdown/layers.js
index b8081ef..3b1669b 100644
--- a/packages/topdown/layers.js
+++ b/packages/topdown/layers.js
@@ -2,6 +2,7 @@ import * as I from 'immutable';
 
 import {compose} from '@avocado/core';
 import {EventEmitter} from '@avocado/mixins';
+import {StateSynchronizer} from '@avocado/state';
 
 import {Layer} from './layer';
 
@@ -84,12 +85,31 @@ export class Layers extends decorate(class {}) {
   }
 
   patchState(patch) {
-    for (const index in patch) {
-      const layer = this.layers[index] ? this.layers[index] : new Layer();
-      if (!this.layers[index]) {
-        this.addLayer(index, layer);
+    for (const step of patch) {
+      const {op, path, value} = step;
+      if ('/' === path) {
+        for (const index in value) {
+          const layer = this.layers[index] ? this.layers[index] : new Layer();
+          if (!this.layers[index]) {
+            this.addLayer(index, layer);
+          }
+          layer.patchState([
+            {
+              op: 'replace',
+              path: '/',
+              value: value[index],
+            }
+          ]);
+        }
+      }
+      else {
+        const [index, substep] = StateSynchronizer.forwardStep(step);
+        const layer = this.layers[index] ? this.layers[index] : new Layer();
+        if (!this.layers[index]) {
+          this.addLayer(index, layer);
+        }
+        layer.patchState([substep]);
       }
-      layer.patchState(patch[index]);
     }
   }
 
diff --git a/packages/topdown/room.js b/packages/topdown/room.js
index 78ca065..178ca2b 100644
--- a/packages/topdown/room.js
+++ b/packages/topdown/room.js
@@ -4,6 +4,7 @@ import {compose} from '@avocado/core';
 import {Vector} from '@avocado/math';
 import {EventEmitter, Property} from '@avocado/mixins';
 import {RectangleShape} from '@avocado/physics';
+import {StateSynchronizer} from '@avocado/state';
 
 import {Layers} from './layers';
 
@@ -96,14 +97,31 @@ export class Room extends decorate(class {}) {
   }
 
   patchState(patch) {
-    if (patch.width) {
-      this.width = patch.width;
-    }
-    if (patch.height) {
-      this.height = patch.height;
-    }
-    if (patch.layers) {
-      this.layers.patchState(patch.layers);
+    for (const step of patch) {
+      const {op, path, value} = step;
+      if ('/' === path) {
+        if (value.width) {
+          this.width = value.width;
+        }
+        if (value.height) {
+          this.height = value.height;
+        }
+        if (value.layers) {
+          this.layers.patchState([
+            {
+              op: 'replace',
+              path: '/',
+              value: value.layers,
+            }
+          ])
+        }
+      }
+      else {
+        const [key, substep] = StateSynchronizer.forwardStep(step);
+        if ('layers' === key) {
+          this.layers.patchState([substep]);
+        }
+      }
     }
   }
 
diff --git a/packages/topdown/tiles.js b/packages/topdown/tiles.js
index 50c3dc5..3b23da2 100644
--- a/packages/topdown/tiles.js
+++ b/packages/topdown/tiles.js
@@ -20,20 +20,24 @@ export class Tiles extends decorate(class {}) {
   }
 
   patchState(patch) {
-    if (patch.width) {
-      this.width = patch.width;
-    }
-    if (patch.height) {
-      this.height = patch.height;
-    }
-    if (patch.data) {
-      const oldData = this.data;
-      for (const i in patch.data) {
-        const index = parseInt(i);
-        this.data = this.data.set(index, patch.data[i]);
-      }
-      if (oldData !== this.data) {
-        this.emit('dataChanged');
+    for (const {op, path, value} of patch) {
+      if ('/' === path) {
+        if (value.width) {
+          this.width = value.width;
+        }
+        if (value.height) {
+          this.height = value.height;
+        }
+        if (value.data) {
+          const oldData = this.data;
+          for (const i in value.data) {
+            const index = parseInt(i);
+            this.data = this.data.set(index, value.data[i]);
+          }
+          if (oldData !== this.data) {
+            this.emit('dataChanged');
+          }
+        }
       }
     }
   }