diff --git a/web/app/cad/craft/craftPlugin.js b/web/app/cad/craft/craftPlugin.js
index d51727e5..674595fa 100644
--- a/web/app/cad/craft/craftPlugin.js
+++ b/web/app/cad/craft/craftPlugin.js
@@ -50,6 +50,12 @@ export function activate({streams, services}) {
       pointer: modifications.length - 1
     });
   }
+
+  function rebuild() {
+    const mods = streams.craft.modifications.value;
+    reset([]);
+    streams.craft.modifications.next(mods);
+  }
   
   function runRequest(request) {
     let op = services.operation.get(request.type);
@@ -79,7 +85,7 @@ export function activate({streams, services}) {
   }
   
   services.craft = {
-    modify, modifyInHistoryAndStep, reset, runRequest, 
+    modify, modifyInHistoryAndStep, reset, runRequest, rebuild,
     historyTravel: historyTravel(streams.craft.modifications)
   };
 
diff --git a/web/app/cad/craft/ui/HistoryTimeline.jsx b/web/app/cad/craft/ui/HistoryTimeline.jsx
index 6293fc44..99b24384 100644
--- a/web/app/cad/craft/ui/HistoryTimeline.jsx
+++ b/web/app/cad/craft/ui/HistoryTimeline.jsx
@@ -19,19 +19,20 @@ import {aboveElement} from '../../../../../modules/ui/positionUtils';
     inProgressOperation: insertOperationReq.type,
     getOperation: type => operationRegistry[type]||EMPTY_OBJECT
   })))
-@mapContext(({streams}) => ({
+@mapContext(({streams, services}) => ({
   remove: atIndex => streams.craft.modifications.update(modifications => removeAndDropDependants(modifications, atIndex)),
   cancel: () => streams.craft.modifications.update(modifications => finishHistoryEditing(modifications)),
-  setHistoryPointer: pointer => streams.craft.modifications.update(({history}) => ({history, pointer}))
+  setHistoryPointer: pointer => streams.craft.modifications.update(({history}) => ({history, pointer})),
+  rebuild: () => services.craft.rebuild()
 }))
 export default class HistoryTimeline extends React.Component {
 
   render() {
-    let {history, pointer, setHistoryPointer, remove, getOperation, inProgressOperation} = this.props;
+    let {history, pointer, setHistoryPointer, rebuild, getOperation, inProgressOperation} = this.props;
     let scrolly;
     let eof = history.length-1;
     return <div className={ls.root} ref={this.keepRef}>
-      <Controls pointer={pointer} eoh={eof} setHistoryPointer={this.setHistoryPointerAndRequestScroll}/>
+      <Controls rebuild={rebuild} history={history} pointer={pointer} eoh={eof} setHistoryPointer={this.setHistoryPointerAndRequestScroll}/>
       <div className={ls.scroller} onClick={e => scrolly.scrollLeft -= 60}><Fa icon='caret-left'/></div>
       <div className={ls.history} ref={el => scrolly = el}>
         {history.map((m, i) => <React.Fragment key={i}>
@@ -102,10 +103,13 @@ function Handle() {
   </svg>;
 }
 
-function Controls({pointer, eoh, setHistoryPointer}) {
+function Controls({rebuild, history, pointer, eoh, setHistoryPointer, }) {
   const noB = pointer===-1;
   const noF = pointer===eoh;
   return <React.Fragment>
+    <button disabled={!history.length} className={cx(ls.controlBtn)} onClick={rebuild}>
+      <Fa icon='repeat' fw/>
+    </button>
     <div className={cx(ls.controlBtn, noB&&ls.disabled)} onClick={noB?undefined :() => setHistoryPointer(pointer-1)}>
       <Fa icon='step-backward' fw/>
     </div>
diff --git a/web/app/cad/expressions/expressionsPlugin.js b/web/app/cad/expressions/expressionsPlugin.js
index dcfdeb40..81802e2a 100644
--- a/web/app/cad/expressions/expressionsPlugin.js
+++ b/web/app/cad/expressions/expressionsPlugin.js
@@ -1,6 +1,6 @@
-import {state, stream, merge} from 'lstream';
-import {indexArray} from '../../../../modules/gems/iterables';
-import {NOOP} from '../../../../modules/gems/func';
+import {merge, state} from 'lstream';
+import {indexArray} from 'gems/iterables';
+import {NOOP} from 'gems/func';
 
 export function defineStreams(ctx) {
   const script = state('');
@@ -39,8 +39,10 @@ export function activate(ctx) {
     return value;
   }
   ctx.services.expressions = {
-    reevaluateExpressions, load, evaluateExpression
+    reevaluateExpressions, load, evaluateExpression,
+    signature: ''
   };
+  ctx.streams.expressions.list.attach(list => ctx.services.expressions.signature = Date.now() + '');
   ctx.services.action.registerAction({
     id: 'expressionsUpdateTable',
     appearance: {
diff --git a/web/app/cad/sketch/inPlaceSketcher.js b/web/app/cad/sketch/inPlaceSketcher.js
index 1152b5e9..efd1d23d 100644
--- a/web/app/cad/sketch/inPlaceSketcher.js
+++ b/web/app/cad/sketch/inPlaceSketcher.js
@@ -19,7 +19,7 @@ export class InPlaceSketcher {
     return !!this.face    
   }
   
-  enter(face) {
+  enter(face, headless) {
     let viewer3d = this.ctx.services.viewer;
     this.face = face;
     this.face.ext.view.sketchGroup.visible = false;
@@ -34,6 +34,7 @@ export class InPlaceSketcher {
 
     container.appendChild(canvas);
     this.viewer = new Viewer(canvas, IO);
+    this.viewer.parametricManager.externalConstantResolver = this.ctx.services.expressions.evaluateExpression;
     this.ctx.streams.sketcherApp = this.viewer.streams;
 
     this.syncWithCamera();
@@ -45,7 +46,7 @@ export class InPlaceSketcher {
     this.viewer.io.loadSketch(sketchData);
     this.ctx.streams.sketcher.sketchingFace.value = face;
   }
-  
+
   get sketchStorageKey() {
     return this.ctx.services.project.sketchStorageKey(this.face.id);
   }
@@ -106,7 +107,9 @@ export class InPlaceSketcher {
   };
   
   save() {
-    this.ctx.services.storage.set(this.sketchStorageKey, this.viewer.io.serializeSketch());
+    this.ctx.services.storage.set(this.sketchStorageKey, this.viewer.io.serializeSketch({
+      expressionsSignature: this.ctx.services.expressions.signature
+    }));
   }
 }
 
diff --git a/web/app/cad/sketch/sketcherPlugin.js b/web/app/cad/sketch/sketcherPlugin.js
index bfda96ad..e78b24af 100644
--- a/web/app/cad/sketch/sketcherPlugin.js
+++ b/web/app/cad/sketch/sketcherPlugin.js
@@ -5,6 +5,9 @@ import {InPlaceSketcher} from './inPlaceSketcher';
 import sketcherUIContrib from './sketcherUIContrib';
 import initReassignSketchMode from './reassignSketchMode';
 import sketcherStreams from '../../sketcher/sketcherStreams';
+import {Viewer} from "../../sketcher/viewer2d";
+import {IO} from "../../sketcher/io";
+import {DelegatingPanTool} from "../../sketcher/tools/pan";
 
 export function defineStreams(ctx) {
   ctx.streams.sketcher = {
@@ -55,11 +58,34 @@ export function activate(ctx) {
     return services.storage.remove(sketchStorageKey);
   }
 
+  const headlessCanvas = document.createElement('canvas');
+  document.createElement('div').appendChild(headlessCanvas);
+
   function readSketch(sketchId) {
     let savedSketch = getSketchData(sketchId);
     if (savedSketch === null) {
       return null;
     }
+
+    let signature = services.expressions.signature;
+    if (savedSketch && (!savedSketch.metadata || savedSketch.expressionsSignature !== signature)) {
+      try {
+        const viewer = new Viewer(headlessCanvas, IO);
+        viewer.parametricManager.externalConstantResolver = services.expressions.evaluateExpression;
+        viewer.historyManager.init(savedSketch);
+        viewer.io.loadSketch(savedSketch);
+        viewer.parametricManager.refresh();
+        services.storage.set(services.project.sketchStorageKey(sketchId), viewer.io.serializeSketch({
+          expressionsSignature: signature
+        }), true);
+        savedSketch = getSketchData(sketchId);
+      } catch (e) {
+        console.error(e);
+        return null;
+      }
+    }
+
+
     try {
       return ReadSketch(JSON.parse(savedSketch), sketchId, true);  
     } catch (e) {
@@ -132,7 +158,14 @@ export function activate(ctx) {
       }
     }
   });
-  
+  streams.expressions.table.attach(() => {
+    if (inPlaceEditor.viewer !== null) {
+      inPlaceEditor.viewer.parametricManager.refresh();
+    }
+    updateAllSketches();
+  });
+
+
   services.sketcher = {
     sketchFace, sketchFace2D, updateAllSketches, getAllSketches, readSketch, hasSketch, inPlaceEditor, reassignSketch,
     reassignSketchMode: initReassignSketchMode(ctx)
diff --git a/web/app/cad/storagePlugin.js b/web/app/cad/storagePlugin.js
index 5c9907a1..fd13820d 100644
--- a/web/app/cad/storagePlugin.js
+++ b/web/app/cad/storagePlugin.js
@@ -8,9 +8,11 @@ export function defineStreams(ctx) {
 
 export function activate({services, streams}) {
 
-  function set(key, value) {
+  function set(key, value, quiet) {
     localStorage.setItem(key, value);
-    notify(key);
+    if (!quiet) {
+      notify(key);
+    }
   }
 
   function get(key) {
diff --git a/web/app/cad/tpi/tpiPlugin.js b/web/app/cad/tpi/tpiPlugin.js
index 9664183f..e55271a7 100644
--- a/web/app/cad/tpi/tpiPlugin.js
+++ b/web/app/cad/tpi/tpiPlugin.js
@@ -12,7 +12,7 @@ export function activate({streams, services}) {
     return sceneSolid;
   }
   function addOnScene(sceneSolid, skin) {
-    services.cadRegistry.update(null, [sceneSolid]);
+    streams.craft.models.next([sceneSolid]);
     services.viewer.render();
   }
   services.tpi = Object.assign({
diff --git a/web/app/math/vec.js b/web/app/math/vec.js
index bb2520f0..65fccc89 100644
--- a/web/app/math/vec.js
+++ b/web/app/math/vec.js
@@ -1,6 +1,6 @@
 export {dotVM} from 'numeric';
 
-function scalarOperand(v, out, func) {
+export function scalarOperand(v, out, func) {
   for (let i = 0; i < v.length; i++) {
     out[i] = func(v[i]);
   }
diff --git a/web/app/sketcher/io.js b/web/app/sketcher/io.js
index 142c4d52..47502c69 100644
--- a/web/app/sketcher/io.js
+++ b/web/app/sketcher/io.js
@@ -43,8 +43,8 @@ IO.prototype.loadSketch = function(sketchData) {
   return this._loadSketch(JSON.parse(sketchData));
 };
 
-IO.prototype.serializeSketch = function() {
-  return JSON.stringify(this._serializeSketch());
+IO.prototype.serializeSketch = function(metadata) {
+  return JSON.stringify(this._serializeSketch(metadata));
 };
 
 IO.prototype._loadSketch = function(sketch) {
@@ -333,7 +333,7 @@ IO.prototype.cleanUpData = function() {
   }
 };
 
-IO.prototype._serializeSketch = function() {
+IO.prototype._serializeSketch = function(metadata) {
   var sketch = {};
   //sketch.boundary = boundary;
   sketch['layers'] = [];
@@ -408,6 +408,7 @@ IO.prototype._serializeSketch = function() {
   if (constantDefinition !== undefined && constantDefinition != null && !/^\s*$/.test(constantDefinition)) {
     sketch['constants'] = constantDefinition;
   }
+  sketch.metadata = metadata;
   return sketch;
 };
 
diff --git a/web/app/sketcher/parametric.js b/web/app/sketcher/parametric.js
index 494cdaea..a2886cfb 100644
--- a/web/app/sketcher/parametric.js
+++ b/web/app/sketcher/parametric.js
@@ -19,6 +19,7 @@ class ParametricManager {
     this.viewer.params.define('constantDefinition', null);
     this.viewer.params.subscribe('constantDefinition', 'parametricManager', this.onConstantsExternalChange, this)();
     this.constantResolver = this.createConstantResolver();
+    this.externalConstantResolver = null;
     this.messageSink = msg => alert(msg);
   }
   
@@ -28,9 +29,11 @@ class ParametricManager {
 }
 
 ParametricManager.prototype.createConstantResolver = function() {
-  var pm = this;
-  return function(value) {
-    var _value = pm.constantTable[value];
+  return value => {
+    var _value = this.constantTable[value];
+    if (_value === undefined && this.externalConstantResolver) {
+      _value = this.externalConstantResolver(value);
+    }
     if (_value !== undefined) {
       value = _value;
     } else if (typeof(value) != 'number') {