diff --git a/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.samplechecker.handler.test/models/jetbrains/mps/lang/typesystem2/samplechecker/handle/test/util.mps b/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.samplechecker.handler.test/models/jetbrains/mps/lang/typesystem2/samplechecker/handle/test/util.mps
index 182a5e64..561d91d2 100644
--- a/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.samplechecker.handler.test/models/jetbrains/mps/lang/typesystem2/samplechecker/handle/test/util.mps
+++ b/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.samplechecker.handler.test/models/jetbrains/mps/lang/typesystem2/samplechecker/handle/test/util.mps
@@ -38,6 +38,7 @@
       <concept id="1070533707846" name="jetbrains.mps.baseLanguage.structure.StaticFieldReference" flags="nn" index="10M0yZ">
         <reference id="1144433057691" name="classifier" index="1PxDUh" />
       </concept>
+      <concept id="1070534058343" name="jetbrains.mps.baseLanguage.structure.NullLiteral" flags="nn" index="10Nm6u" />
       <concept id="1070534644030" name="jetbrains.mps.baseLanguage.structure.BooleanType" flags="in" index="10P_77" />
       <concept id="1068431474542" name="jetbrains.mps.baseLanguage.structure.VariableDeclaration" flags="ng" index="33uBYm">
         <child id="1068431790190" name="initializer" index="33vP2m" />
@@ -347,13 +348,13 @@
                   <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
                 </node>
                 <node concept="liA8E" id="5jPBdK_voQ" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdK_vsV" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdK_vv8" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdK_vy4" role="37wK5m">
@@ -596,14 +597,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdK_vXl" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdK_vXm" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdK_vXn" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="37vLTw" id="5jPBdK_vXo" role="37wK5m">
                   <ref role="3cqZAo" node="7t5VLKGALUW" resolve="expect" />
@@ -831,13 +832,13 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdK_wcc" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdK_wcd" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdK_wce" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdK_wcf" role="37wK5m">
@@ -1094,14 +1095,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdK_w_i" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdK_w_j" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdK_w_k" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="37vLTw" id="5jPBdK_w_l" role="37wK5m">
                   <ref role="3cqZAo" node="7t5VLKGALXG" resolve="expect" />
@@ -1512,13 +1513,13 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdK_wPu" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdK_wPv" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdK_wPw" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdK_wPx" role="37wK5m">
@@ -1989,13 +1990,13 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdK_x7D" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdK_x7E" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdK_x7F" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdK_x7G" role="37wK5m">
@@ -2523,14 +2524,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdK_xqT" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdK_xqU" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdK_xqV" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="37vLTw" id="5jPBdK_xqW" role="37wK5m">
                   <ref role="3cqZAo" node="3KV3FXk2oKs" resolve="expect" />
@@ -2978,14 +2979,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdK_xIm" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdK_xIn" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdK_xIo" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="37vLTw" id="5jPBdK_xIp" role="37wK5m">
                   <ref role="3cqZAo" node="3hfdu5cN_MP" resolve="expect" />
@@ -3457,13 +3458,13 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdK_y10" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdK_y11" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdK_y12" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdK_y13" role="37wK5m">
@@ -3798,14 +3799,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdK_yj7" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdK_yj8" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdK_yj9" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="37vLTw" id="5jPBdK_yja" role="37wK5m">
                   <ref role="3cqZAo" node="3KV3FXk18Pu" resolve="expect" />
@@ -3834,16 +3835,17 @@
               <node concept="2YIFZM" id="5jPBdK_uTI" role="2Oq$k0">
                 <ref role="37wK5l" to="rchb:7ISVfSIwfH" resolve="newSession" />
                 <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
+                <node concept="10Nm6u" id="6X5F0NgIltC" role="37wK5m" />
               </node>
               <node concept="liA8E" id="5jPBdK_uVI" role="2OqNvi">
                 <ref role="37wK5l" to="rchb:5uFPQ7Bwu9Q" resolve="withPredicates" />
                 <node concept="10M0yZ" id="5jPBdK_uXa" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
-                  <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
                 </node>
                 <node concept="10M0yZ" id="5jPBdK_uXd" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
               </node>
             </node>
@@ -4202,13 +4204,13 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdK_R$V" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdK_R$W" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdK_R$X" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdK_R$Y" role="37wK5m">
@@ -4238,16 +4240,17 @@
               <node concept="2YIFZM" id="5jPBdK_QKo" role="2Oq$k0">
                 <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
                 <ref role="37wK5l" to="rchb:7ISVfSIwfH" resolve="newSession" />
+                <node concept="10Nm6u" id="6X5F0NgIlBS" role="37wK5m" />
               </node>
               <node concept="liA8E" id="5jPBdK_QKp" role="2OqNvi">
                 <ref role="37wK5l" to="rchb:5uFPQ7Bwu9Q" resolve="withPredicates" />
                 <node concept="10M0yZ" id="5jPBdK_QKq" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
                 </node>
                 <node concept="10M0yZ" id="5jPBdK_QKr" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
               </node>
             </node>
diff --git a/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.samplechecker.runner/models/jetbrains/mps/lang/typesystem2/samplechecker/runner.mps b/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.samplechecker.runner/models/jetbrains/mps/lang/typesystem2/samplechecker/runner.mps
index 7ed3486c..aeaa6793 100644
--- a/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.samplechecker.runner/models/jetbrains/mps/lang/typesystem2/samplechecker/runner.mps
+++ b/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.samplechecker.runner/models/jetbrains/mps/lang/typesystem2/samplechecker/runner.mps
@@ -260,24 +260,24 @@
       <node concept="2ShNRf" id="5mr7UHcbowK" role="33vP2m">
         <node concept="3g6Rrh" id="5mr7UHcboy8" role="2ShVmc">
           <node concept="10M0yZ" id="5mr7UHcboyR" role="3g7hyw">
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
             <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
           </node>
           <node concept="10M0yZ" id="5mr7UHcboyX" role="3g7hyw">
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
             <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
           </node>
           <node concept="10M0yZ" id="5mr7UHcboz3" role="3g7hyw">
             <ref role="3cqZAo" to="oy3s:5uFPQ7BZnLB" resolve="ASSERT_SYM" />
-            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertPredicate" />
           </node>
           <node concept="10M0yZ" id="5mr7UHcboz9" role="3g7hyw">
             <ref role="3cqZAo" to="xq5w:5uFPQ7C26$b" resolve="BOUND_SYM" />
-            <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalBuiltinConstraint" />
+            <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalPredicate" />
           </node>
           <node concept="10M0yZ" id="5mr7UHcbozf" role="3g7hyw">
             <ref role="3cqZAo" to="xq5w:5uFPQ7C279$" resolve="FREE_SYM" />
-            <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalBuiltinConstraint" />
+            <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalPredicate" />
           </node>
           <node concept="3uibUv" id="5mr7UHcbqo2" role="3g7fb8">
             <ref role="3uigEE" to="qrld:5uFPQ7B$$3f" resolve="PredicateSymbol" />
@@ -452,6 +452,7 @@
                   <node concept="2YIFZM" id="5mr7UHcbsDX" role="2Oq$k0">
                     <ref role="37wK5l" to="rchb:7ISVfSIwfH" resolve="newSession" />
                     <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
+                    <node concept="10Nm6u" id="6X5F0NgIn0C" role="37wK5m" />
                   </node>
                   <node concept="liA8E" id="5mr7UHcbsDY" role="2OqNvi">
                     <ref role="37wK5l" to="rchb:5mr7UHcbbR2" resolve="withParam" />
diff --git a/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.sampleplugin/models/jetbrains/mps/lang/typesystem2/sampleplugin/plugin.mps b/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.sampleplugin/models/jetbrains/mps/lang/typesystem2/sampleplugin/plugin.mps
index 7ad417c9..015c0355 100644
--- a/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.sampleplugin/models/jetbrains/mps/lang/typesystem2/sampleplugin/plugin.mps
+++ b/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.sampleplugin/models/jetbrains/mps/lang/typesystem2/sampleplugin/plugin.mps
@@ -1973,34 +1973,21 @@
               <node concept="2OqwBi" id="5mr7UHcbsDU" role="2Oq$k0">
                 <node concept="2OqwBi" id="5mr7UHcbsDV" role="2Oq$k0">
                   <node concept="2OqwBi" id="5jPBdKSAEU" role="2Oq$k0">
-                    <node concept="2OqwBi" id="1ggxSI7ySc8" role="2Oq$k0">
-                      <node concept="2OqwBi" id="5mr7UHcbsDW" role="2Oq$k0">
-                        <node concept="2YIFZM" id="5mr7UHcbsDX" role="2Oq$k0">
-                          <ref role="37wK5l" to="rchb:7ISVfSIwfH" resolve="newSession" />
-                          <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
-                        </node>
-                        <node concept="liA8E" id="5mr7UHcbsDY" role="2OqNvi">
-                          <ref role="37wK5l" to="rchb:5mr7UHcbbR2" resolve="withParam" />
-                          <node concept="Xl_RD" id="5mr7UHcbsDZ" role="37wK5m">
-                            <property role="Xl_RC" value="jchr.handler.class" />
-                          </node>
-                          <node concept="37vLTw" id="5mr7UHcbsE0" role="37wK5m">
-                            <ref role="3cqZAo" node="41ox5Vnki5N" resolve="handlerCls" />
-                          </node>
+                    <node concept="2OqwBi" id="5mr7UHcbsDW" role="2Oq$k0">
+                      <node concept="2YIFZM" id="5mr7UHcbsDX" role="2Oq$k0">
+                        <ref role="37wK5l" to="rchb:7ISVfSIwfH" resolve="newSession" />
+                        <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
+                        <node concept="37vLTw" id="6X5F0NgIpqc" role="37wK5m">
+                          <ref role="3cqZAo" node="6X5F0Ngiil4" resolve="program" />
                         </node>
                       </node>
-                      <node concept="liA8E" id="1ggxSI7yShU" role="2OqNvi">
+                      <node concept="liA8E" id="5mr7UHcbsDY" role="2OqNvi">
                         <ref role="37wK5l" to="rchb:5mr7UHcbbR2" resolve="withParam" />
-                        <node concept="Xl_RD" id="1ggxSI7yShV" role="37wK5m">
-                          <property role="Xl_RC" value="session.solver" />
+                        <node concept="Xl_RD" id="5mr7UHcbsDZ" role="37wK5m">
+                          <property role="Xl_RC" value="jchr.handler.class" />
                         </node>
-                        <node concept="2OqwBi" id="6X5F0NginmB" role="37wK5m">
-                          <node concept="37vLTw" id="6X5F0Ngin1_" role="2Oq$k0">
-                            <ref role="3cqZAo" node="6X5F0Ngiil4" resolve="program" />
-                          </node>
-                          <node concept="liA8E" id="6X5F0Ngi$$S" role="2OqNvi">
-                            <ref role="37wK5l" to="rchb:6X5F0Ngip_N" resolve="sessionSolver" />
-                          </node>
+                        <node concept="37vLTw" id="5mr7UHcbsE0" role="37wK5m">
+                          <ref role="3cqZAo" node="41ox5Vnki5N" resolve="handlerCls" />
                         </node>
                       </node>
                     </node>
diff --git a/languages/jetbrains.mps.logic/jchr/models/jetbrains/mps/logic/jchr/program.mps b/languages/jetbrains.mps.logic/jchr/models/jetbrains/mps/logic/jchr/program.mps
index 7c418496..fac49099 100644
--- a/languages/jetbrains.mps.logic/jchr/models/jetbrains/mps/logic/jchr/program.mps
+++ b/languages/jetbrains.mps.logic/jchr/models/jetbrains/mps/logic/jchr/program.mps
@@ -299,18 +299,34 @@
       </node>
       <node concept="3Tm6S6" id="7ISVfSIeUM" role="1B3o_S" />
       <node concept="3clFbS" id="7ISVfSIeJ0" role="3clF47">
+        <node concept="3cpWs8" id="6X5F0NgMnm$" role="3cqZAp">
+          <node concept="3cpWsn" id="6X5F0NgMnm_" role="3cpWs9">
+            <property role="TrG5h" value="program" />
+            <node concept="3uibUv" id="6X5F0NgMnmz" role="1tU5fm">
+              <ref role="3uigEE" to="rchb:5uFPQ7BvNzE" resolve="PlanningSession" />
+            </node>
+            <node concept="2OqwBi" id="6X5F0NgMnmA" role="33vP2m">
+              <node concept="37vLTw" id="6X5F0NgMnmB" role="2Oq$k0">
+                <ref role="3cqZAo" node="7ISVfSIeK_" resolve="config" />
+              </node>
+              <node concept="2OwXpG" id="6X5F0NgMnmC" role="2OqNvi">
+                <ref role="2Oxat5" node="6X5F0NgIrGR" resolve="program" />
+              </node>
+            </node>
+          </node>
+        </node>
         <node concept="3cpWs8" id="2tcGHBEeeWq" role="3cqZAp">
           <node concept="3cpWsn" id="2tcGHBEeeWr" role="3cpWs9">
             <property role="TrG5h" value="solver" />
             <node concept="3uibUv" id="6X5F0Ngi_lx" role="1tU5fm">
               <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
             </node>
-            <node concept="2OqwBi" id="1ggxSI7xkCx" role="33vP2m">
-              <node concept="37vLTw" id="1ggxSI7xk$q" role="2Oq$k0">
-                <ref role="3cqZAo" node="7ISVfSIeK_" resolve="config" />
+            <node concept="2OqwBi" id="6X5F0NgMoyF" role="33vP2m">
+              <node concept="37vLTw" id="6X5F0NgMnmD" role="2Oq$k0">
+                <ref role="3cqZAo" node="6X5F0NgMnm_" resolve="program" />
               </node>
-              <node concept="liA8E" id="1ggxSI7xkGT" role="2OqNvi">
-                <ref role="37wK5l" node="1ggxSI7xeK4" resolve="getSessionSolver" />
+              <node concept="liA8E" id="6X5F0NgMoAY" role="2OqNvi">
+                <ref role="37wK5l" to="rchb:6X5F0Ngip_N" resolve="sessionSolver" />
               </node>
             </node>
           </node>
@@ -739,6 +755,32 @@
       <property role="2bfB8j" value="false" />
       <property role="TrG5h" value="Config" />
       <node concept="2tJIrI" id="5mr7UHcbw3u" role="jymVt" />
+      <node concept="3clFbW" id="6X5F0NgIrce" role="jymVt">
+        <node concept="3cqZAl" id="6X5F0NgIrcg" role="3clF45" />
+        <node concept="3Tm1VV" id="6X5F0NgIrch" role="1B3o_S" />
+        <node concept="3clFbS" id="6X5F0NgIrci" role="3clF47">
+          <node concept="3clFbF" id="6X5F0NgIrGV" role="3cqZAp">
+            <node concept="37vLTI" id="6X5F0NgIrGX" role="3clFbG">
+              <node concept="2OqwBi" id="6X5F0NgIrH1" role="37vLTJ">
+                <node concept="Xjq3P" id="6X5F0NgIrH4" role="2Oq$k0" />
+                <node concept="2OwXpG" id="6X5F0NgIrH0" role="2OqNvi">
+                  <ref role="2Oxat5" node="6X5F0NgIrGR" resolve="program" />
+                </node>
+              </node>
+              <node concept="37vLTw" id="6X5F0NgIrH5" role="37vLTx">
+                <ref role="3cqZAo" node="6X5F0NgIrCd" resolve="program" />
+              </node>
+            </node>
+          </node>
+        </node>
+        <node concept="37vLTG" id="6X5F0NgIrCd" role="3clF46">
+          <property role="TrG5h" value="program" />
+          <node concept="3uibUv" id="6X5F0NgIrCc" role="1tU5fm">
+            <ref role="3uigEE" to="rchb:5uFPQ7BvNzE" resolve="PlanningSession" />
+          </node>
+        </node>
+      </node>
+      <node concept="2tJIrI" id="6X5F0NgIqOL" role="jymVt" />
       <node concept="3clFb_" id="7ISVfSIuSh" role="jymVt">
         <property role="TrG5h" value="start" />
         <node concept="3uibUv" id="7ISVfSIv24" role="3clF45">
@@ -1000,46 +1042,7 @@
           </node>
         </node>
       </node>
-      <node concept="2tJIrI" id="1ggxSI7xfam" role="jymVt" />
-      <node concept="3clFb_" id="1ggxSI7xeK4" role="jymVt">
-        <property role="TrG5h" value="getSessionSolver" />
-        <node concept="3uibUv" id="6X5F0NgieZc" role="3clF45">
-          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
-        </node>
-        <node concept="3Tmbuc" id="1ggxSI7xeK7" role="1B3o_S" />
-        <node concept="3clFbS" id="1ggxSI7xeK8" role="3clF47">
-          <node concept="3cpWs8" id="1ggxSI7xeK9" role="3cqZAp">
-            <node concept="3cpWsn" id="1ggxSI7xeKa" role="3cpWs9">
-              <property role="TrG5h" value="solver" />
-              <node concept="3uibUv" id="1ggxSI7xeKb" role="1tU5fm">
-                <ref role="3uigEE" to="wyt6:~Object" resolve="Object" />
-              </node>
-              <node concept="2OqwBi" id="1ggxSI7xeKc" role="33vP2m">
-                <node concept="37vLTw" id="1ggxSI7xeKd" role="2Oq$k0">
-                  <ref role="3cqZAo" node="5mr7UHcbcAv" resolve="parameters" />
-                </node>
-                <node concept="liA8E" id="1ggxSI7xeKe" role="2OqNvi">
-                  <ref role="37wK5l" to="33ny:~Map.get(java.lang.Object):java.lang.Object" resolve="get" />
-                  <node concept="Xl_RD" id="1ggxSI7xeKf" role="37wK5m">
-                    <property role="Xl_RC" value="session.solver" />
-                  </node>
-                </node>
-              </node>
-            </node>
-          </node>
-          <node concept="3clFbF" id="1ggxSI7xeKg" role="3cqZAp">
-            <node concept="10QFUN" id="1ggxSI7xeKh" role="3clFbG">
-              <node concept="37vLTw" id="1ggxSI7xeKi" role="10QFUP">
-                <ref role="3cqZAo" node="1ggxSI7xeKa" resolve="solver" />
-              </node>
-              <node concept="3uibUv" id="6X5F0NgieUR" role="10QFUM">
-                <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
-              </node>
-            </node>
-          </node>
-        </node>
-      </node>
-      <node concept="2tJIrI" id="5jPBdKSLoW" role="jymVt" />
+      <node concept="2tJIrI" id="6X5F0NgMmO9" role="jymVt" />
       <node concept="3clFb_" id="5jPBdKSL09" role="jymVt">
         <property role="TrG5h" value="getTracer" />
         <node concept="3uibUv" id="5jPBdKSOdR" role="3clF45">
@@ -1122,6 +1125,13 @@
       <node concept="3uibUv" id="5mr7UHcbvZ3" role="1zkMxy">
         <ref role="3uigEE" to="rchb:5uFPQ7Bwt8Z" resolve="EvaluationSession.Config" />
       </node>
+      <node concept="312cEg" id="6X5F0NgIrGR" role="jymVt">
+        <property role="TrG5h" value="program" />
+        <node concept="3Tmbuc" id="6X5F0NgMn8h" role="1B3o_S" />
+        <node concept="3uibUv" id="6X5F0NgIrGU" role="1tU5fm">
+          <ref role="3uigEE" to="rchb:5uFPQ7BvNzE" resolve="PlanningSession" />
+        </node>
+      </node>
     </node>
     <node concept="2tJIrI" id="5mr7UHcbvhQ" role="jymVt" />
     <node concept="312cEu" id="7ISVfSIeeZ" role="jymVt">
@@ -1206,6 +1216,12 @@
       <node concept="3clFb_" id="5mr7UHcbuUQ" role="jymVt">
         <property role="1EzhhJ" value="false" />
         <property role="TrG5h" value="createConfig" />
+        <node concept="37vLTG" id="6X5F0NgIqD5" role="3clF46">
+          <property role="TrG5h" value="program" />
+          <node concept="3uibUv" id="6X5F0NgIqJ5" role="1tU5fm">
+            <ref role="3uigEE" to="rchb:5uFPQ7BvNzE" resolve="PlanningSession" />
+          </node>
+        </node>
         <node concept="3uibUv" id="5mr7UHcbuUR" role="3clF45">
           <ref role="3uigEE" to="rchb:5uFPQ7Bwt8Z" resolve="EvaluationSession.Config" />
         </node>
@@ -1213,8 +1229,11 @@
         <node concept="3clFbS" id="5mr7UHcbuUU" role="3clF47">
           <node concept="3clFbF" id="5mr7UHcbzBW" role="3cqZAp">
             <node concept="2ShNRf" id="5mr7UHcbzBU" role="3clFbG">
-              <node concept="HV5vD" id="5mr7UHcbzLn" role="2ShVmc">
-                <ref role="HV5vE" node="5mr7UHcbv_1" resolve="JchrEvaluationSession.Config" />
+              <node concept="1pGfFk" id="6X5F0NgIrzl" role="2ShVmc">
+                <ref role="37wK5l" node="6X5F0NgIrce" resolve="JchrEvaluationSession.Config" />
+                <node concept="37vLTw" id="6X5F0NgIs6o" role="37wK5m">
+                  <ref role="3cqZAo" node="6X5F0NgIqD5" resolve="program" />
+                </node>
               </node>
             </node>
           </node>
diff --git a/languages/jetbrains.mps.logic/reactor/models/jetbrains/mps/logic/reactor/program.mps b/languages/jetbrains.mps.logic/reactor/models/jetbrains/mps/logic/reactor/program.mps
index cda0d7c9..dc7ee58b 100644
--- a/languages/jetbrains.mps.logic/reactor/models/jetbrains/mps/logic/reactor/program.mps
+++ b/languages/jetbrains.mps.logic/reactor/models/jetbrains/mps/logic/reactor/program.mps
@@ -499,6 +499,12 @@
     <node concept="2tJIrI" id="5uFPQ7Bwt4d" role="jymVt" />
     <node concept="2YIFZL" id="7ISVfSIwfH" role="jymVt">
       <property role="TrG5h" value="newSession" />
+      <node concept="37vLTG" id="6X5F0NgIkLY" role="3clF46">
+        <property role="TrG5h" value="program" />
+        <node concept="3uibUv" id="6X5F0NgIkO$" role="1tU5fm">
+          <ref role="3uigEE" node="5uFPQ7BvNzE" resolve="PlanningSession" />
+        </node>
+      </node>
       <node concept="3uibUv" id="7ISVfSIw_G" role="3clF45">
         <ref role="3uigEE" node="5uFPQ7Bwt8Z" resolve="EvaluationSession.Config" />
       </node>
@@ -531,6 +537,9 @@
             </node>
             <node concept="liA8E" id="5mr7UHcbuzj" role="2OqNvi">
               <ref role="37wK5l" node="5mr7UHcbuF5" resolve="createConfig" />
+              <node concept="37vLTw" id="6X5F0NgIuxk" role="37wK5m">
+                <ref role="3cqZAo" node="6X5F0NgIkLY" resolve="program" />
+              </node>
             </node>
           </node>
         </node>
@@ -770,6 +779,12 @@
       <node concept="3clFb_" id="5mr7UHcbuF5" role="jymVt">
         <property role="1EzhhJ" value="true" />
         <property role="TrG5h" value="createConfig" />
+        <node concept="37vLTG" id="6X5F0NgIqn1" role="3clF46">
+          <property role="TrG5h" value="program" />
+          <node concept="3uibUv" id="6X5F0NgIqpx" role="1tU5fm">
+            <ref role="3uigEE" node="5uFPQ7BvNzE" resolve="PlanningSession" />
+          </node>
+        </node>
         <node concept="3uibUv" id="5mr7UHcbuIP" role="3clF45">
           <ref role="3uigEE" node="5uFPQ7Bwt8Z" resolve="EvaluationSession.Config" />
         </node>
diff --git a/languages/jetbrains.mps.logic/test/models/jetbrains/mps/logic/test/unification.mps b/languages/jetbrains.mps.logic/test/models/jetbrains/mps/logic/test/unification.mps
index 57c6a523..644f23e2 100644
--- a/languages/jetbrains.mps.logic/test/models/jetbrains/mps/logic/test/unification.mps
+++ b/languages/jetbrains.mps.logic/test/models/jetbrains/mps/logic/test/unification.mps
@@ -3897,6 +3897,7 @@
               <node concept="2YIFZM" id="5jPBdK_uTI" role="2Oq$k0">
                 <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
                 <ref role="37wK5l" to="rchb:7ISVfSIwfH" resolve="newSession" />
+                <node concept="10Nm6u" id="6X5F0NgIqiP" role="37wK5m" />
               </node>
               <node concept="liA8E" id="5jPBdK_uVI" role="2OqNvi">
                 <ref role="37wK5l" to="rchb:5uFPQ7Bwu9Q" resolve="withPredicates" />
@@ -4958,6 +4959,31 @@
       <node concept="3uibUv" id="5jPBdK_n1a" role="1zkMxy">
         <ref role="3uigEE" to="rchb:5uFPQ7Bwt8Z" resolve="EvaluationSession.Config" />
       </node>
+      <node concept="3clFbW" id="6X5F0NgIsD1" role="jymVt">
+        <node concept="37vLTG" id="6X5F0NgIsWe" role="3clF46">
+          <property role="TrG5h" value="program" />
+          <node concept="3uibUv" id="6X5F0NgIt0n" role="1tU5fm">
+            <ref role="3uigEE" to="rchb:5uFPQ7BvNzE" resolve="PlanningSession" />
+          </node>
+        </node>
+        <node concept="3cqZAl" id="6X5F0NgIsD3" role="3clF45" />
+        <node concept="3Tm1VV" id="6X5F0NgIsD4" role="1B3o_S" />
+        <node concept="3clFbS" id="6X5F0NgIsD5" role="3clF47">
+          <node concept="3clFbF" id="6X5F0NgIt2U" role="3cqZAp">
+            <node concept="37vLTI" id="6X5F0NgIt2W" role="3clFbG">
+              <node concept="2OqwBi" id="6X5F0NgIt30" role="37vLTJ">
+                <node concept="Xjq3P" id="6X5F0NgIt33" role="2Oq$k0" />
+                <node concept="2OwXpG" id="6X5F0NgIt2Z" role="2OqNvi">
+                  <ref role="2Oxat5" node="6X5F0NgIt2Q" resolve="program" />
+                </node>
+              </node>
+              <node concept="37vLTw" id="6X5F0NgIt34" role="37vLTx">
+                <ref role="3cqZAo" node="6X5F0NgIsWe" resolve="program" />
+              </node>
+            </node>
+          </node>
+        </node>
+      </node>
       <node concept="3clFb_" id="5jPBdK_npi" role="jymVt">
         <property role="TrG5h" value="withPredicates" />
         <property role="1EzhhJ" value="false" />
@@ -5097,6 +5123,13 @@
           </node>
         </node>
       </node>
+      <node concept="312cEg" id="6X5F0NgIt2Q" role="jymVt">
+        <property role="TrG5h" value="program" />
+        <node concept="3Tm6S6" id="6X5F0NgIt2R" role="1B3o_S" />
+        <node concept="3uibUv" id="6X5F0NgIt2T" role="1tU5fm">
+          <ref role="3uigEE" to="rchb:5uFPQ7BvNzE" resolve="PlanningSession" />
+        </node>
+      </node>
     </node>
     <node concept="2tJIrI" id="5jPBdK_mO3" role="jymVt" />
     <node concept="312cEu" id="5jPBdK_dKd" role="jymVt">
@@ -5126,6 +5159,12 @@
       <node concept="3clFb_" id="5jPBdK_dSh" role="jymVt">
         <property role="1EzhhJ" value="false" />
         <property role="TrG5h" value="createConfig" />
+        <node concept="37vLTG" id="6X5F0NgIslG" role="3clF46">
+          <property role="TrG5h" value="program" />
+          <node concept="3uibUv" id="6X5F0NgIsrs" role="1tU5fm">
+            <ref role="3uigEE" to="rchb:5uFPQ7BvNzE" resolve="PlanningSession" />
+          </node>
+        </node>
         <node concept="3uibUv" id="5jPBdK_dSi" role="3clF45">
           <ref role="3uigEE" to="rchb:5uFPQ7Bwt8Z" resolve="EvaluationSession.Config" />
         </node>
@@ -5133,8 +5172,11 @@
         <node concept="3clFbS" id="5jPBdK_dSl" role="3clF47">
           <node concept="3clFbF" id="5jPBdK_nWq" role="3cqZAp">
             <node concept="2ShNRf" id="5jPBdK_nWo" role="3clFbG">
-              <node concept="HV5vD" id="5jPBdK_p0f" role="2ShVmc">
-                <ref role="HV5vE" node="5jPBdK_mRo" resolve="TestingEvaluationSession.Config" />
+              <node concept="1pGfFk" id="6X5F0NgIsKG" role="2ShVmc">
+                <ref role="37wK5l" node="6X5F0NgIsD1" resolve="TestingEvaluationSession.Config" />
+                <node concept="37vLTw" id="6X5F0NgItsZ" role="37wK5m">
+                  <ref role="3cqZAo" node="6X5F0NgIslG" resolve="program" />
+                </node>
               </node>
             </node>
           </node>