diff --git a/web/app/sketcher/components/ContextualControls.jsx b/web/app/sketcher/components/ContextualControls.jsx
index 132c0d3f..0a4bcdf0 100644
--- a/web/app/sketcher/components/ContextualControls.jsx
+++ b/web/app/sketcher/components/ContextualControls.jsx
@@ -20,7 +20,7 @@ export function ContextualControls() {
   return <div className={ls.root}>
 
     {
-      selection.map(s => <div className={ls.item}>{s.simpleClassName}: {s.id}</div>)
+      selection.map(s => <div onDoubleClick={debugEgg(s)} className={ls.item}>{s.simpleClassName}: {s.id}</div>)
     }
 
     <div className={ls.hr}>AVAILABLE ACTIONS:</div>
@@ -33,3 +33,9 @@ export function ContextualControls() {
   </div>;
 
 }
+
+function debugEgg(obj) {
+  return e => {
+    obj.visitParams(p => console.log(p.toString()));
+  }
+}
\ No newline at end of file
diff --git a/web/app/sketcher/constr/AlgNumSystem.js b/web/app/sketcher/constr/AlgNumSystem.js
index c96383ef..12d37db1 100644
--- a/web/app/sketcher/constr/AlgNumSystem.js
+++ b/web/app/sketcher/constr/AlgNumSystem.js
@@ -30,6 +30,8 @@ export class AlgNumSubSystem {
 
   snapshot = new Map();
 
+  inTransaction = false;
+
   constructor() {
 
     this.solveStatus = {
@@ -53,6 +55,12 @@ export class AlgNumSubSystem {
 
   addConstraint(constraint) {
 
+    if (this.inTransaction) {
+      constraint.objects.forEach(o => o.constraints.add(constraint));
+      this.allConstraints.push(constraint);
+      return;
+    }
+
     this.makeSnapshot();
 
     this.allConstraints.push(constraint);
@@ -78,17 +86,17 @@ export class AlgNumSubSystem {
     }
   }
 
-  addConstraints(constraints) {
-    constraints.forEach(constraint => {
-      if (constraint) {
-        constraint.objects.forEach(o => o.constraints.add(constraint));
-        this.allConstraints.push(constraint);
-      }
-    });
+  startTransaction() {
+    this.inTransaction = true;
+  }
+
+  finishTransaction() {
+    this.inTransaction = false;
     this.prepare();
     this.updateFullyConstrainedObjects();
   }
 
+
   invalidate() {
     this.prepare();
     this.solveFine();
@@ -409,20 +417,30 @@ export class AlgNumSubSystem {
     return this.eliminatedParams.has(p) || (iso && iso.fullyConstrained);
   }
 
-  isParamFullyConstrained(p) {
-    const stack = [p];
-    while (stack.length) {
-      const param = stack.pop();
-      if (!this.isParamShallowConstrained(param)) {
-        return false;
-      }
+  isParamFullyConstrained(sourceParam) {
 
-      const substitution = this.substitutedParams.get(p);
-      if (substitution) {
-        substitution.visitParams(p => stack.push(p));
+    const visited = new Set();
+
+    const dfs = param => {
+      if (visited.has(param)) {
+        return;
       }
-    }
-    return true;
+      visited.add(param);
+      if (this.isParamShallowConstrained(param)) {
+        return true;
+      }
+      const substitution = this.substitutedParams.get(param);
+      let res = false;
+      if (substitution) {
+        substitution.visitParams(p => {
+          if (dfs(p)) {
+            res = true;
+          }
+        });
+      }
+      return res;
+    };
+    return dfs(sourceParam);
   }
 
 }
diff --git a/web/app/sketcher/io.js b/web/app/sketcher/io.js
index 28240659..c96b26e1 100644
--- a/web/app/sketcher/io.js
+++ b/web/app/sketcher/io.js
@@ -52,6 +52,8 @@ IO.prototype._loadSketch = function(sketch) {
 
   this.cleanUpData();
 
+  this.viewer.parametricManager.algNumSystem.startTransaction();
+
   const index = {};
 
   function endPoint(p) {
@@ -210,14 +212,15 @@ IO.prototype._loadSketch = function(sketch) {
 
   let sketchConstraints = sketch['constraints'];
   if (version > 1) {
-    this.viewer.parametricManager.algNumSystem.addConstraints(sketchConstraints.map(constr => {
+    sketchConstraints.forEach(constr => {
       try {
-        return AlgNumConstraint.read(constr, index)
+        const constraint = AlgNumConstraint.read(constr, index);
+        this.viewer.parametricManager.algNumSystem.addConstraint(constraint);
       } catch (e) {
         console.error(e);
         console.error("skipping errant constraint: " + constr&&constr.typeId);
       }
-    }));
+    });
   } else {
     console.error("old format - need an upgrade");
   }
@@ -227,6 +230,7 @@ IO.prototype._loadSketch = function(sketch) {
     this.viewer.params.constantDefinition = constants;
   }
 
+  this.viewer.parametricManager.algNumSystem.finishTransaction();
   this.viewer.parametricManager.notify();
 };
 
diff --git a/web/app/sketcher/shapes/param.js b/web/app/sketcher/shapes/param.js
index befe913d..e6ebd2f2 100644
--- a/web/app/sketcher/shapes/param.js
+++ b/web/app/sketcher/shapes/param.js
@@ -18,4 +18,8 @@ export class Param {
     return this.value;
   }
 
+  toString() {
+    return this.debugSymbol + this.id;
+  }
+
 }
\ No newline at end of file