diff --git a/src/math/polysat/conflict.cpp b/src/math/polysat/conflict.cpp
index 7691fc383..267bfb0c6 100644
--- a/src/math/polysat/conflict.cpp
+++ b/src/math/polysat/conflict.cpp
@@ -81,7 +81,7 @@ namespace polysat {
         }
         else {
             SASSERT(c.is_currently_false(s));
-    // TBD: fails with test_subst       SASSERT(c.bvalue(s) == l_true);
+            // TBD: fails with test_subst       SASSERT(c.bvalue(s) == l_true);
             c->set_var_dependent();
             insert(c);
         }
@@ -100,10 +100,12 @@ namespace polysat {
         LOG("Conflict: v" << v);
         SASSERT(empty());
         m_conflict_var = v;
+#if !NEW_VIABLE
         for (auto c : s.m_cjust[v]) {
             c->set_var_dependent(); // ??
             insert(c);
         }
+#endif
         SASSERT(!empty());
     }
 
@@ -286,7 +288,7 @@ namespace polysat {
     }
 
 
-    bool conflict::resolve_value(pvar v, vector<signed_constraint> const& cjust_v) {
+    bool conflict::resolve_value(pvar v) {
         // NOTE:
         // In the "standard" case where "v = val" is on the stack:
         //      - cjust_v contains true constraints
@@ -298,13 +300,23 @@ namespace polysat {
             return false;
         }
 
+#if NEW_VIABLE
+        if (conflict_var() == v && s.m_viable.resolve(v, *this))
+            return true;
+#else
         if (conflict_var() == v && s.m_forbidden_intervals.perform(v, cjust_v, *this))
             return true;        
+#endif
         
         m_vars.remove(v);
 
+#if NEW_VIABLE
+        for (auto const& c : s.m_viable.get_constraints(v))
+            insert(c);
+#else
         for (auto c : cjust_v)
             insert(c);
+#endif
 
         for (auto* engine : ex_engines)
             if (engine->try_explain(v, *this))
diff --git a/src/math/polysat/conflict.h b/src/math/polysat/conflict.h
index 7018e8c51..25c58dff8 100644
--- a/src/math/polysat/conflict.h
+++ b/src/math/polysat/conflict.h
@@ -103,7 +103,7 @@ namespace polysat {
         /** Perform value resolution by applying various inference rules.
          *  Returns true if it was possible to eliminate the variable 'v'.
          */
-        bool resolve_value(pvar v, vector<signed_constraint> const& cjust_v);
+        bool resolve_value(pvar v);
 
         /** Convert the core into a lemma to be learned. */
         clause_builder build_lemma();
diff --git a/src/math/polysat/saturation.cpp b/src/math/polysat/saturation.cpp
index 3120ebbdb..f0d11719f 100644
--- a/src/math/polysat/saturation.cpp
+++ b/src/math/polysat/saturation.cpp
@@ -180,10 +180,17 @@ namespace polysat {
         if (x_max * y_max  > pddm.max_value())            
             push_omega_bisect(x, x_max, y, y_max);
         else {
+#if NEW_VIABLE
+            for (auto const& c : s.m_viable.get_constraints(y.var()))
+                m_new_constraints.insert(c);
+            for (auto const& c : s.m_viable.get_constraints(x.var()))
+                m_new_constraints.insert(c);            
+#else
             for (auto c : s.m_cjust[y.var()])
                 m_new_constraints.insert(c);
             for (auto c : s.m_cjust[x.var()])
                 m_new_constraints.insert(c);
+#endif
         }
     }
 
diff --git a/src/math/polysat/solver.cpp b/src/math/polysat/solver.cpp
index 9557344a1..3c6a5e1d4 100644
--- a/src/math/polysat/solver.cpp
+++ b/src/math/polysat/solver.cpp
@@ -98,7 +98,9 @@ namespace polysat {
         m_value.push_back(rational::zero());
         m_justification.push_back(justification::unassigned());
         m_viable.push(sz);
+#if !NEW_VIABLE
         m_cjust.push_back({});
+#endif
         m_pwatch.push_back({});
         m_activity.push_back(0);
         m_vars.push_back(sz2pdd(sz).mk_var(v));
@@ -116,7 +118,9 @@ namespace polysat {
         // TODO also remove v from all learned constraints.
         pvar v = m_value.size() - 1;
         m_viable.pop();
+#if !NEW_VIABLE
         m_cjust.pop_back();
+#endif
         m_value.pop_back();
         m_justification.pop_back();
         m_pwatch.pop_back();
@@ -342,10 +346,12 @@ namespace polysat {
                 break;
             }
             case trail_instr_t::just_i: {
+#if !NEW_VIABLE
                 auto v = m_cjust_trail.back();
                 LOG_V("Undo just_i");
                 m_cjust[v].pop_back();
                 m_cjust_trail.pop_back();
+#endif
                 break;
             }
             default:
@@ -474,8 +480,12 @@ namespace polysat {
         LOG_H2("Resolve conflict");
         LOG("\n" << *this);
         LOG("search state: " << m_search);
+#if NEW_VIABLE
+        m_viable.log();
+#else
         for (pvar v = 0; v < m_cjust.size(); ++v)
             LOG("cjust[v" << v << "]: " << m_cjust[v]);
+#endif
         ++m_stats.m_num_conflicts;
 
         SASSERT(is_conflict());
@@ -527,7 +537,7 @@ namespace polysat {
 
     /** Conflict resolution case where propagation 'v := ...' is on top of the stack */
     bool solver::resolve_value(pvar v) {
-        return m_conflict.resolve_value(v, m_cjust[v]);
+        return m_conflict.resolve_value(v);
     }
 
     /** Conflict resolution case where boolean literal 'lit' is on top of the stack 
@@ -762,6 +772,7 @@ namespace polysat {
     void solver::narrow(pvar v) {
         if (is_conflict())
             return;
+        // TODO
     }
 
     // Add lemma to storage
@@ -793,7 +804,7 @@ namespace polysat {
         unsigned base_level = m_base_levels[m_base_levels.size() - num_scopes];
         LOG("Pop " << num_scopes << " user scopes; lowest popped level = " << base_level << "; current level = " << m_level);
         pop_levels(m_level - base_level + 1);
-        m_conflict.reset();   // TODO: maybe keep conflict if level of all constraints is lower than base_level?
+        m_conflict.reset();   
     }
 
     bool solver::at_base_level() const {
@@ -817,9 +828,11 @@ namespace polysat {
             if (item.is_assignment()) {
                 pvar v = item.var();
                 auto const& j = m_justification[v];
-                out << "\t" << assignment_pp(*this, v, get_value(v)) << " @" << j.level();               
+                out << "\t" << assignment_pp(*this, v, get_value(v)) << " @" << j.level();   
+#if !NEW_VIABLE
                 if (j.is_propagation())
                     out << " " << m_cjust[v];
+#endif
                 out << "\n";
             }
             else {
diff --git a/src/math/polysat/solver.h b/src/math/polysat/solver.h
index 0dd223533..02520e699 100644
--- a/src/math/polysat/solver.h
+++ b/src/math/polysat/solver.h
@@ -32,8 +32,12 @@ Author:
 #include "math/polysat/forbidden_intervals.h"
 #include "math/polysat/trail.h"
 #include "math/polysat/viable.h"
+#include "math/polysat/viable2.h"
 #include "math/polysat/log.h"
 
+
+#define NEW_VIABLE 0
+
 namespace polysat {
 
     class solver {
@@ -71,7 +75,11 @@ namespace polysat {
 
         reslimit&                m_lim;
         params_ref               m_params;
+#if NEW_VIABLE
+        viable2                  m_viable;
+#else
         viable                   m_viable;   // viable sets per variable
+#endif
         scoped_ptr_vector<dd::pdd_manager> m_pdd;
         linear_solver            m_linear_solver;
         conflict                 m_conflict;        
@@ -92,7 +100,9 @@ namespace polysat {
         // Per variable information
         vector<rational>         m_value;         // assigned value
         vector<justification>    m_justification; // justification for variable assignment
+#if !NEW_VIABLE
         vector<signed_constraints> m_cjust;       // constraints justifying variable range.
+#endif
         vector<signed_constraints> m_pwatch;      // watch list datastructure into constraints.
 
         unsigned_vector          m_activity; 
@@ -121,6 +131,7 @@ namespace polysat {
             m_qhead_trail.pop_back();
         }
 
+#if !NEW_VIABLE
         void push_cjust(pvar v, signed_constraint c) {
             if (m_cjust[v].contains(c))  // TODO: better check (flag on constraint?)
                 return;
@@ -130,6 +141,7 @@ namespace polysat {
             m_trail.push_back(trail_instr_t::just_i);
             m_cjust_trail.push_back(v);
         }
+#endif
 
         unsigned size(pvar v) const { return m_size[v]; }
 
diff --git a/src/math/polysat/ule_constraint.cpp b/src/math/polysat/ule_constraint.cpp
index 725970177..3c72657bc 100644
--- a/src/math/polysat/ule_constraint.cpp
+++ b/src/math/polysat/ule_constraint.cpp
@@ -129,7 +129,7 @@ namespace polysat {
             return;
         }
 
-#if 0
+#if NEW_VIABLE
         // setup with viable2:
         // we no longer need cjust
         pvar v = null_var;
@@ -139,9 +139,9 @@ namespace polysat {
             v = q.var();
         if (v != null_var) {
             signed_constraint sc(this, is_positive);
-            s.m_viable2.intersect(v, sc);
+            s.m_viable.intersect(v, sc);
             rational val;
-            switch (s.m_viable2.find_viable(v, val)) {
+            switch (s.m_viable.find_viable(v, val)) {
             case dd::find_t::singleton:
                 s.propagate(v, val, sc);
                 break;
diff --git a/src/math/polysat/viable2.cpp b/src/math/polysat/viable2.cpp
index 0c602dc50..71913cd03 100644
--- a/src/math/polysat/viable2.cpp
+++ b/src/math/polysat/viable2.cpp
@@ -246,12 +246,13 @@ namespace polysat {
             return dd::find_t::multiple;
     }
 
-    void viable2::get_core(pvar v, conflict& core) {
-        core.reset();
+    bool viable2::resolve(pvar v, conflict& core) {
+        if (has_viable(v))
+            return false;
         auto* e = m_viable[v];
         entry* first = e;
         SASSERT(e);
-        SASSERT(!has_viable(v));
+        core.reset();
         do {
             // Build constraint: upper bound of each interval is not contained in the next interval,
             // using the equivalence:  t \in [l;h[  <=>  t-l < h-l
@@ -280,6 +281,7 @@ namespace polysat {
                 break;
             }
         }
+        return true;
     }
 
     void viable2::log(pvar v) {
diff --git a/src/math/polysat/viable2.h b/src/math/polysat/viable2.h
index 71086f827..4ddebdec3 100644
--- a/src/math/polysat/viable2.h
+++ b/src/math/polysat/viable2.h
@@ -97,7 +97,7 @@ namespace polysat {
         * Retrieve the unsat core for v.
         * \pre there are no viable values for v
         */
-        void get_core(pvar v, conflict& core);
+        bool resolve(pvar v, conflict& core);
 
         /** Log all viable values for the given variable.
          * (Inefficient, but useful for debugging small instances.)
@@ -108,6 +108,46 @@ namespace polysat {
         void log();
 
         std::ostream& display(std::ostream& out) const;
+
+        class iterator {
+            entry* curr = nullptr;
+            bool   visited = false;
+        public:
+            iterator(entry* curr, bool visited) : 
+                curr(curr), visited(visited || !curr) {}
+
+            iterator& operator++() {
+                visited = true;
+                curr = curr->next();
+                return *this;
+            }
+
+            signed_constraint& operator*() { 
+                return curr->src; 
+            }
+
+            bool operator==(iterator const& other) const {
+                return visited == other.visited && curr == other.curr;
+            }
+
+            bool operator!=(iterator const& other) const {
+                return !(*this == other);
+            }
+        };
+
+        class constraints {
+            viable2& viable;
+            pvar var;
+        public:
+            constraints(viable2& viable, pvar var) : viable(viable), var(var) {}
+            iterator begin() const { return iterator(viable.m_viable[var], false); }
+            iterator end() const { return iterator(viable.m_viable[var], true); }
+        };
+
+        constraints get_constraints(pvar v) { 
+            return constraints(*this, v); 
+        }
+       
     };
 
     inline std::ostream& operator<<(std::ostream& out, viable2 const& v) {