diff --git a/src/cmd_context/cmd_context.cpp b/src/cmd_context/cmd_context.cpp
index 079597fdc..993b8d68f 100644
--- a/src/cmd_context/cmd_context.cpp
+++ b/src/cmd_context/cmd_context.cpp
@@ -353,6 +353,17 @@ void cmd_context::set_cancel(bool f) {
         m().set_cancel(f);
 }
 
+opt_wrapper* cmd_context::get_opt() {
+    return m_opt.get();
+}
+
+void cmd_context::set_opt(opt_wrapper* opt) {
+    m_opt = opt;
+    for (unsigned i = 0; i < m_scopes.size(); ++i) {
+        m_opt->push();
+    }
+}
+
 void cmd_context::global_params_updated() {
     m_params.updt_params();
     if (m_params.m_smtlib2_compliant)
@@ -1161,6 +1172,7 @@ void cmd_context::reset(bool finalize) {
     restore_assertions(0);
     if (m_solver)
         m_solver = 0;
+    m_opt = 0;
     m_pp_env = 0;
     m_dt_eh  = 0;
     if (m_manager) {
@@ -1226,6 +1238,8 @@ void cmd_context::push() {
     s.m_assertions_lim         = m_assertions.size();
     if (m_solver) 
         m_solver->push();
+    if (m_opt) 
+        m_opt->push();
 }
 
 void cmd_context::push(unsigned n) {
@@ -1321,6 +1335,8 @@ void cmd_context::pop(unsigned n) {
     if (m_solver) {
         m_solver->pop(n);
     }
+    if (m_opt) 
+        m_opt->pop(n);
     unsigned new_lvl = lvl - n;
     scope & s        = m_scopes[new_lvl];
     restore_func_decls(s.m_func_decls_stack_lim);
@@ -1338,15 +1354,35 @@ void cmd_context::check_sat(unsigned num_assumptions, expr * const * assumptions
     TRACE("before_check_sat", dump_assertions(tout););
     if (!has_manager())
         init_manager();
-    if (m_solver) {
+    unsigned timeout = m_params.m_timeout;
+    scoped_watch sw(*this);
+    lbool r;
+
+    if (m_opt && !m_opt->empty()) {
+        m_check_sat_result = get_opt();
+        cancel_eh<opt_wrapper> eh(*get_opt());
+        scoped_ctrl_c ctrlc(eh);
+        scoped_timer timer(timeout, &eh);
+        ptr_vector<expr> cnstr(m_assertions);
+        cnstr.append(num_assumptions, assumptions);
+        get_opt()->set_hard_constraints(cnstr);
+        try {
+            r = get_opt()->optimize();
+        }
+        catch (z3_error & ex) {
+            throw ex;
+        }
+        catch (z3_exception & ex) {
+            throw cmd_exception(ex.msg());
+        }
+        get_opt()->set_status(r);
+    }
+    else if (m_solver) {
         m_check_sat_result = m_solver.get(); // solver itself stores the result.
         m_solver->set_progress_callback(this);
-        unsigned timeout     = m_params.m_timeout;
-        scoped_watch sw(*this);
         cancel_eh<solver> eh(*m_solver);
         scoped_ctrl_c ctrlc(eh);
         scoped_timer timer(timeout, &eh);
-        lbool r;
         try {
             r = m_solver->check_sat(num_assumptions, assumptions);
         }
@@ -1357,15 +1393,17 @@ void cmd_context::check_sat(unsigned num_assumptions, expr * const * assumptions
             throw cmd_exception(ex.msg());
         }
         m_solver->set_status(r);
-        display_sat_result(r);
-        validate_check_sat_result(r);
-        if (r == l_true)
-            validate_model();
     }
     else {
         // There is no solver installed in the command context.
         regular_stream() << "unknown" << std::endl;
+        return;
     }
+    display_sat_result(r);
+    validate_check_sat_result(r);
+    if (r == l_true)
+        validate_model();
+
 }
 
 void cmd_context::display_sat_result(lbool r) {
diff --git a/src/cmd_context/cmd_context.h b/src/cmd_context/cmd_context.h
index 5f24ff808..dc0bf9833 100644
--- a/src/cmd_context/cmd_context.h
+++ b/src/cmd_context/cmd_context.h
@@ -111,6 +111,18 @@ struct builtin_decl {
     builtin_decl(family_id fid, decl_kind k, builtin_decl * n = 0):m_fid(fid), m_decl(k), m_next(n) {}
 };
 
+class opt_wrapper : public check_sat_result {
+public:
+    virtual bool empty() = 0;
+    virtual void push() = 0;
+    virtual void pop(unsigned n) = 0;
+    virtual void set_cancel(bool f) = 0;
+    virtual void reset_cancel() = 0;
+    virtual void cancel() = 0;
+    virtual lbool optimize() = 0;
+    virtual void set_hard_constraints(ptr_vector<expr> & hard) = 0;
+};
+
 class cmd_context : public progress_callback, public tactic_manager, public ast_printer_context {
 public:
     enum status {
@@ -187,8 +199,9 @@ protected:
     svector<scope>               m_scopes;
     scoped_ptr<solver_factory>   m_solver_factory;
     scoped_ptr<solver_factory>   m_interpolating_solver_factory;
-    ref<solver>                  m_solver;
+    ref<solver>                  m_solver;    
     ref<check_sat_result>        m_check_sat_result;
+    ref<opt_wrapper>             m_opt;
 
     stopwatch                    m_watch;
 
@@ -255,6 +268,8 @@ public:
     context_params  & params() { return m_params; }
     solver_factory &get_solver_factory() { return *m_solver_factory; }
     solver_factory &get_interpolating_solver_factory() { return *m_interpolating_solver_factory; }
+    opt_wrapper*  get_opt();
+    void          set_opt(opt_wrapper* o);
     void global_params_updated(); // this method should be invoked when global (and module) params are updated.
     bool set_logic(symbol const & s);
     bool has_logic() const { return m_logic != symbol::null; }
diff --git a/src/opt/opt_cmds.cpp b/src/opt/opt_cmds.cpp
index 7a87ac6ca..857a3c585 100644
--- a/src/opt/opt_cmds.cpp
+++ b/src/opt/opt_cmds.cpp
@@ -32,33 +32,22 @@ Notes:
 #include "opt_params.hpp"
 #include "model_smt2_pp.h"
 
-class opt_context {
-    cmd_context& ctx;
-    scoped_ptr<opt::context> m_opt;
-    hashtable<symbol, symbol_hash_proc, symbol_eq_proc> m_ids;    
-
-public:
-    opt_context(cmd_context& ctx): ctx(ctx) {}
-    opt::context& operator()() { 
-        if (!m_opt) {
-            m_opt = alloc(opt::context, ctx.m());
-        }
-        return *m_opt;
-    }    
-};
-
+static opt::context& get_opt(cmd_context& cmd) {
+    if (!cmd.get_opt()) {
+        cmd.set_opt(alloc(opt::context, cmd.m()));
+    }
+    return dynamic_cast<opt::context&>(*cmd.get_opt());
+}
 
 class assert_weighted_cmd : public cmd {
-    opt_context& m_opt_ctx;
     unsigned     m_idx;
     expr*        m_formula;
     rational     m_weight;
     symbol       m_id;
 
 public:
-    assert_weighted_cmd(cmd_context& ctx, opt_context& opt_ctx):
+    assert_weighted_cmd():
         cmd("assert-weighted"),
-        m_opt_ctx(opt_ctx),
         m_idx(0),
         m_formula(0),
         m_weight(0)
@@ -115,7 +104,7 @@ public:
     }
 
     virtual void execute(cmd_context & ctx) {
-        m_opt_ctx().add_soft_constraint(m_formula, m_weight, m_id);
+        get_opt(ctx).add_soft_constraint(m_formula, m_weight, m_id);
         reset(ctx);
     }
 
@@ -126,14 +115,12 @@ public:
 
 
 class assert_soft_cmd : public parametric_cmd {
-    opt_context& m_opt_ctx;
     unsigned     m_idx;
     expr*        m_formula;
 
 public:
-    assert_soft_cmd(cmd_context& ctx, opt_context& opt_ctx):
+    assert_soft_cmd():
         parametric_cmd("assert-soft"),
-        m_opt_ctx(opt_ctx),
         m_idx(0),
         m_formula(0)
     {}
@@ -188,7 +175,7 @@ public:
             weight = rational::one();
         }
         symbol id = ps().get_sym(symbol("id"), symbol::null);
-        m_opt_ctx().add_soft_constraint(m_formula, weight, id);
+        get_opt(ctx).add_soft_constraint(m_formula, weight, id);
         reset(ctx);
     }
 
@@ -199,13 +186,11 @@ public:
 
 class min_maximize_cmd : public cmd {
     bool         m_is_max;
-    opt_context& m_opt_ctx;
 
 public:
-    min_maximize_cmd(cmd_context& ctx, opt_context& opt_ctx, bool is_max):
+    min_maximize_cmd(bool is_max):
         cmd(is_max?"maximize":"minimize"),
-        m_is_max(is_max),
-        m_opt_ctx(opt_ctx)
+        m_is_max(is_max)
     {}
 
     virtual void reset(cmd_context & ctx) { }
@@ -221,7 +206,7 @@ public:
         if (!is_app(t)) {
             throw cmd_exception("malformed objective term: it cannot be a quantifier or bound variable");
         }
-        m_opt_ctx().add_objective(to_app(t), m_is_max);
+        get_opt(ctx).add_objective(to_app(t), m_is_max);
     }
 
     virtual void failure_cleanup(cmd_context & ctx) {
@@ -233,15 +218,12 @@ public:
 };
 
 class optimize_cmd : public parametric_cmd {
-    opt_context& m_opt_ctx;
 public:
-    optimize_cmd(opt_context& opt_ctx):
-        parametric_cmd("optimize"),
-        m_opt_ctx(opt_ctx)
+    optimize_cmd():
+        parametric_cmd("optimize")
     {}
 
     virtual ~optimize_cmd() {
-        dealloc(&m_opt_ctx);
     }
 
     virtual void init_pdescrs(cmd_context & ctx, param_descrs & p) {
@@ -267,7 +249,7 @@ public:
 
     virtual void execute(cmd_context & ctx) {
         params_ref p = ctx.params().merge_default_params(ps());
-        opt::context& opt = m_opt_ctx();
+        opt::context& opt = get_opt(ctx);
         opt.updt_params(p);
         unsigned timeout = p.get_uint("timeout", UINT_MAX);
 
@@ -313,7 +295,7 @@ public:
 
     void display_result(cmd_context & ctx) {
         params_ref p = ctx.params().merge_default_params(ps());
-        opt::context& opt = m_opt_ctx();
+        opt::context& opt = get_opt(ctx);
         opt.display_assignment(ctx.regular_stream());
         opt_params optp(p);
         if (optp.print_model()) {
@@ -336,7 +318,7 @@ private:
         stats.update("time", ctx.get_seconds());
         stats.update("memory", static_cast<double>(mem)/static_cast<double>(1024*1024));
         stats.update("max memory", static_cast<double>(max_mem)/static_cast<double>(1024*1024));
-        m_opt_ctx().collect_statistics(stats);
+        get_opt(ctx).collect_statistics(stats);
         stats.display_smt2(ctx.regular_stream());        
     }
 };
@@ -344,117 +326,10 @@ private:
 
 
 void install_opt_cmds(cmd_context & ctx) {
-    opt_context* opt_ctx = alloc(opt_context, ctx);
-    ctx.insert(alloc(assert_weighted_cmd, ctx, *opt_ctx));
-    ctx.insert(alloc(assert_soft_cmd, ctx, *opt_ctx));
-    ctx.insert(alloc(min_maximize_cmd, ctx, *opt_ctx, true));
-    ctx.insert(alloc(min_maximize_cmd, ctx, *opt_ctx, false));
-    ctx.insert(alloc(optimize_cmd, *opt_ctx));
+    ctx.insert(alloc(assert_weighted_cmd));
+    ctx.insert(alloc(assert_soft_cmd));
+    ctx.insert(alloc(min_maximize_cmd, true));
+    ctx.insert(alloc(min_maximize_cmd, false));
+    ctx.insert(alloc(optimize_cmd));
 }
 
-#if 0
-    ctx.insert(alloc(execute_cmd, *opt_ctx));
-
-class execute_cmd : public parametric_cmd {
-protected:
-    expr * m_objective;
-    unsigned m_idx;
-    opt_context& m_opt_ctx;
-public:
-    execute_cmd(opt_context& opt_ctx):
-        parametric_cmd("optimize"),
-        m_objective(0),
-        m_idx(0),
-        m_opt_ctx(opt_ctx)
-    {}
-
-    virtual void init_pdescrs(cmd_context & ctx, param_descrs & p) {
-        insert_timeout(p);
-        insert_max_memory(p);
-        p.insert("print_statistics", CPK_BOOL, "(default: false) print statistics.");
-        opt::context::collect_param_descrs(p);
-    }
-
-    virtual char const * get_main_descr() const { return "check sat modulo objective function";}
-    virtual char const * get_usage() const { return "<objective> (<keyword> <value>)*"; }
-    virtual void prepare(cmd_context & ctx) {
-        parametric_cmd::prepare(ctx);
-        reset(ctx);
-        m_opt_ctx(); // ensure symbol table is updated.
-    }
-    virtual void failure_cleanup(cmd_context & ctx) {
-        reset(ctx);
-    }
-    virtual void reset(cmd_context& ctx) {
-        m_objective = 0;
-        m_idx = 0;
-    }
-
-    virtual cmd_arg_kind next_arg_kind(cmd_context & ctx) const {
-        if (m_idx == 0) return CPK_EXPR;
-        return parametric_cmd::next_arg_kind(ctx);
-    }
-
-    virtual void set_next_arg(cmd_context & ctx, expr * arg) {
-        m_objective = arg;
-        ++m_idx;
-    }
-
-    virtual void execute(cmd_context & ctx) {
-        params_ref p = ctx.params().merge_default_params(ps());
-        opt::context& opt = m_opt_ctx();
-        opt.updt_params(p);
-        unsigned timeout = p.get_uint("timeout", UINT_MAX);
-
-        ptr_vector<expr>::const_iterator it  = ctx.begin_assertions();
-        ptr_vector<expr>::const_iterator end = ctx.end_assertions();
-        for (; it != end; ++it) {
-            opt.add_hard_constraint(*it);
-        }
-        lbool r = l_undef;
-        cancel_eh<opt::context> eh(opt);        
-        {
-            scoped_ctrl_c ctrlc(eh);
-            scoped_timer timer(timeout, &eh);
-            cmd_context::scoped_watch sw(ctx);
-            try {
-                r = opt.optimize(m_objective);
-            }
-            catch (z3_error& ex) {
-                ctx.regular_stream() << "(error: " << ex.msg() << "\")" << std::endl;
-            }
-            catch (z3_exception& ex) {
-                ctx.regular_stream() << "(error: " << ex.msg() << "\")" << std::endl;
-            }
-        }
-        switch(r) {
-        case l_true:
-            ctx.regular_stream() << "sat\n";
-            opt.display_assignment(ctx.regular_stream());
-            break;
-        case l_false:
-            ctx.regular_stream() << "unsat\n";
-            break;
-        case l_undef:
-            ctx.regular_stream() << "unknown\n";
-            opt.display_range_assignment(ctx.regular_stream());
-            break;
-        }
-        if (p.get_bool("print_statistics", false)) {
-            display_statistics(ctx);
-        }
-    }
-private:
-
-    void display_statistics(cmd_context& ctx) {
-        statistics stats;
-        unsigned long long max_mem = memory::get_max_used_memory();
-        unsigned long long mem = memory::get_allocation_size();
-        stats.update("time", ctx.get_seconds());
-        stats.update("memory", static_cast<double>(mem)/static_cast<double>(1024*1024));
-        stats.update("max memory", static_cast<double>(max_mem)/static_cast<double>(1024*1024));
-        m_opt_ctx().collect_statistics(stats);
-        stats.display_smt2(ctx.regular_stream());        
-    }
-};
-#endif
diff --git a/src/opt/opt_context.cpp b/src/opt/opt_context.cpp
index 441c0f8a0..849b88e65 100644
--- a/src/opt/opt_context.cpp
+++ b/src/opt/opt_context.cpp
@@ -38,7 +38,8 @@ namespace opt {
 
     context::context(ast_manager& m):
         m(m),
-        arith(m),
+        m_arith(m),
+        m_bv(m),
         m_hard_constraints(m),
         m_optsmt(m),
         m_objective_refs(m)
@@ -55,6 +56,43 @@ namespace opt {
         }
     }
 
+    void context::push() {
+        m_objectives_lim.push_back(m_objectives.size());
+        m_objectives_term_trail_lim.push_back(m_objectives_term_trail.size());
+        m_solver->push();
+    }
+
+    void context::pop(unsigned n) {
+        m_solver->pop(n);
+        while (n > 0) {
+            --n;
+            unsigned k = m_objectives_term_trail_lim.back();
+            while (m_objectives_term_trail.size() > k) {
+                unsigned idx = m_objectives_term_trail.back();
+                m_objectives[idx].m_terms.pop_back();
+                m_objectives[idx].m_weights.pop_back();
+                m_objectives_term_trail.pop_back();
+            }
+            m_objectives_term_trail_lim.pop_back();
+            k = m_objectives_lim.back();
+            while (m_objectives.size() > k) {
+                objective& obj = m_objectives.back();
+                if (obj.m_type == O_MAXSMT) {
+                    dealloc(m_maxsmts[obj.m_id]);
+                    m_maxsmts.erase(obj.m_id);
+                    m_indices.erase(obj.m_id);
+                }
+                m_objectives.pop_back();
+            }
+            m_objectives_lim.pop_back();            
+        }
+    }
+
+    void context::set_hard_constraints(ptr_vector<expr>& fmls) {
+        m_hard_constraints.reset();
+        m_hard_constraints.append(fmls.size(), fmls.c_ptr());
+    }
+
     unsigned context::add_soft_constraint(expr* f, rational const& w, symbol const& id) { 
         maxsmt* ms;
         if (w.is_neg()) {
@@ -77,13 +115,14 @@ namespace opt {
         unsigned idx = m_indices[id];
         m_objectives[idx].m_terms.push_back(f);
         m_objectives[idx].m_weights.push_back(w);
+        m_objectives_term_trail.push_back(idx);
         return idx;
     }
 
     unsigned context::add_objective(app* t, bool is_max) {
         app_ref tr(t, m);
-        if (!arith.is_arith_expr(t)) {
-            throw default_exception("Objective must be integer or real");   
+        if (!m_bv.is_bv(t) && !m_arith.is_int_real(t)) {
+            throw default_exception("Objective must be bit-vector, integer or real");   
         }
         unsigned index = m_objectives.size();
         m_objectives.push_back(objective(is_max, tr, index));
@@ -92,6 +131,7 @@ namespace opt {
 
     lbool context::optimize() {
         opt_solver& s = get_solver();        
+        m_optsmt.reset();
         normalize();
         internalize();
         solver::scoped_push _sp(s);
@@ -225,7 +265,7 @@ namespace opt {
                 objective const& obj = m_objectives[j];
                 bounds[i][j].second = bounds[j][j].second;                
             }
-            display_bounds(verbose_stream() << "new bound\n", bounds[i]);
+            IF_VERBOSE(0, display_bounds(verbose_stream() << "new bound\n", bounds[i]););
         }
 
         for (unsigned i = 0; i < bounds.size(); ++i) {
@@ -247,13 +287,13 @@ namespace opt {
                 bool at_bound = true; 
                 for (unsigned j = 0; j < b.size(); ++j) {
                     objective const& obj = m_objectives[j];
-                    if (m_model->eval(obj.m_term, val) && arith.is_numeral(val, r)) {
+                    if (m_model->eval(obj.m_term, val) && is_numeral(val, r)) {
                         mids[j] = inf_eps(r);
                     }
                     at_bound = at_bound && mids[j] == b[j].second;
                     b[j].second = mids[j];
                 }
-                display_bounds(verbose_stream() << "new bound\n", b);
+                IF_VERBOSE(0, display_bounds(verbose_stream() << "new bound\n", b););
                 if (!at_bound) {
                     bounds.push_back(b);
                 }
@@ -266,7 +306,7 @@ namespace opt {
                     if (j > 0) {
                         b2[j-1].second = b[j-1].second;
                     }
-                    display_bounds(verbose_stream() << "refined bound\n", b2);
+                    IF_VERBOSE(0, display_bounds(verbose_stream() << "refined bound\n", b2););
                     bounds.push_back(b2);
                 }
                 break;
@@ -294,6 +334,11 @@ namespace opt {
         return *m_solver.get(); 
     }
 
+    bool context::is_numeral(expr* e, rational & n) const {
+        unsigned sz;
+        return m_arith.is_numeral(e, n) || m_bv.is_numeral(e, n, sz);
+    }
+
     void context::normalize() {
         expr_ref_vector fmls(m);
         to_fmls(fmls);
@@ -373,8 +418,9 @@ namespace opt {
         app_ref term(m);
         expr* orig_term;
         offset = rational::zero();
-        if (is_minimize(fml, term, orig_term, index) &&
-            get_pb_sum(term, terms, weights, offset)) {
+        bool is_max = is_maximize(fml, term, orig_term, index);
+        bool is_min = !is_max && is_minimize(fml, term, orig_term, index);
+        if (is_min && get_pb_sum(term, terms, weights, offset)) {
             TRACE("opt", tout << "try to convert minimization" << mk_pp(term, m) << "\n";);
             // minimize 2*x + 3*y 
             // <=>
@@ -403,8 +449,7 @@ namespace opt {
             id = symbol(out.str().c_str());
             return true;
         }
-        if (is_maximize(fml, term, orig_term, index) &&
-            get_pb_sum(term, terms, weights, offset)) {
+        if (is_max && get_pb_sum(term, terms, weights, offset)) {
             TRACE("opt", tout << "try to convert maximization" << mk_pp(term, m) << "\n";);
             // maximize 2*x + 3*y - z 
             // <=>
@@ -427,6 +472,25 @@ namespace opt {
             id = symbol(out.str().c_str());
             return true;
         }
+        if ((is_max || is_min) && m_bv.is_bv(term)) {
+            offset.reset();
+            unsigned bv_size = m_bv.get_bv_size(term);
+            expr_ref val(m);
+            val = m_bv.mk_numeral(is_max, 1);
+            for (unsigned i = 0; i < bv_size; ++i) {
+                rational w = power(rational(2),i);
+                weights.push_back(w);
+                terms.push_back(m.mk_eq(val, m_bv.mk_extract(i, i, term)));
+                if (is_max) {
+                    offset += w;
+                }
+            }
+            neg = is_max;
+            std::ostringstream out;
+            out << mk_pp(orig_term, m);
+            id = symbol(out.str().c_str());
+            return true;            
+        }
         return false;
     }
 
@@ -535,7 +599,7 @@ namespace opt {
             switch(obj.m_type) {
             case O_MINIMIZE: {
                 app_ref tmp(m);
-                tmp = arith.mk_uminus(obj.m_term);
+                tmp = m_arith.mk_uminus(obj.m_term);
                 obj.m_index = m_optsmt.add(tmp);
                 break;
             }
@@ -560,12 +624,12 @@ namespace opt {
             objective const& obj = m_objectives[i];
             switch(obj.m_type) {
             case O_MINIMIZE:
-                if (m_model->eval(obj.m_term, val) && arith.is_numeral(val, r)) {
+                if (m_model->eval(obj.m_term, val) && is_numeral(val, r)) {
                     m_optsmt.update_lower(obj.m_index, -r);
                 }
                 break;
             case O_MAXIMIZE:
-                if (m_model->eval(obj.m_term, val) && arith.is_numeral(val, r)) {
+                if (m_model->eval(obj.m_term, val) && is_numeral(val, r)) {
                     m_optsmt.update_lower(obj.m_index, r);
                 }
                 break;
@@ -642,7 +706,6 @@ namespace opt {
         }        
     }
 
-
     inf_eps context::get_upper_as_num(unsigned idx) {
         if (idx > m_objectives.size()) {
             throw default_exception("index out of bounds"); 
@@ -679,30 +742,30 @@ namespace opt {
         rational eps = n.get_infinitesimal();
         expr_ref_vector args(m);
         if (!inf.is_zero()) {
-            expr* oo = m.mk_const(symbol("oo"), arith.mk_int());
+            expr* oo = m.mk_const(symbol("oo"), m_arith.mk_int());
             if (inf.is_one()) {
                 args.push_back(oo);
             }
             else {
-                args.push_back(arith.mk_mul(arith.mk_numeral(inf, inf.is_int()), oo));
+                args.push_back(m_arith.mk_mul(m_arith.mk_numeral(inf, inf.is_int()), oo));
             }
         }
         if (!r.is_zero()) {
-            args.push_back(arith.mk_numeral(r, r.is_int()));
+            args.push_back(m_arith.mk_numeral(r, r.is_int()));
         }
         if (!eps.is_zero()) {
-            expr* ep = m.mk_const(symbol("epsilon"), arith.mk_int());
+            expr* ep = m.mk_const(symbol("epsilon"), m_arith.mk_int());
             if (eps.is_one()) {
                 args.push_back(ep);
             }
             else {
-                args.push_back(arith.mk_mul(arith.mk_numeral(eps, eps.is_int()), ep));
+                args.push_back(m_arith.mk_mul(m_arith.mk_numeral(eps, eps.is_int()), ep));
             }
         }
         switch(args.size()) {
-        case 0: return expr_ref(arith.mk_numeral(rational(0), true), m);
+        case 0: return expr_ref(m_arith.mk_numeral(rational(0), true), m);
         case 1: return expr_ref(args[0].get(), m);
-        default: return expr_ref(arith.mk_add(args.size(), args.c_ptr()), m);
+        default: return expr_ref(m_arith.mk_add(args.size(), args.c_ptr()), m);
         }
     }
         
@@ -870,7 +933,7 @@ namespace opt {
                 if (n.get_infinity().is_zero() &&
                     n.get_infinitesimal().is_zero() &&
                     m_model->eval(obj.m_term, val) &&
-                    arith.is_numeral(val, r1)) {
+                    is_numeral(val, r1)) {
                     rational r2 = n.get_rational();
                     CTRACE("opt", r1 != r2, tout << obj.m_term << " evaluates to " << r1 << " but has objective " << r2 << "\n";);
                     CTRACE("opt", r1 != r2, model_smt2_pp(tout, m, *m_model, 0););
diff --git a/src/opt/opt_context.h b/src/opt/opt_context.h
index 12c9a5c5b..798a67a1c 100644
--- a/src/opt/opt_context.h
+++ b/src/opt/opt_context.h
@@ -32,13 +32,15 @@ Notes:
 #include "model_converter.h"
 #include "tactic.h"
 #include "arith_decl_plugin.h"
+#include "bv_decl_plugin.h"
+#include "cmd_context.h"
 
 
 namespace opt {
 
     class opt_solver;
 
-    class context {
+    class context : public opt_wrapper {
         struct free_func_visitor;
         typedef map<symbol, maxsmt*, symbol_hash_proc, symbol_eq_proc> map_t;
         typedef map<symbol, unsigned, symbol_hash_proc, symbol_eq_proc> map_id;
@@ -80,7 +82,8 @@ namespace opt {
             {}
         };
         ast_manager&        m;
-        arith_util          arith;
+        arith_util          m_arith;
+        bv_util             m_bv;
         expr_ref_vector     m_hard_constraints;
         ref<opt_solver>     m_solver;
         params_ref          m_params;
@@ -88,6 +91,9 @@ namespace opt {
         map_t               m_maxsmts;
         map_id              m_indices;
         vector<objective>   m_objectives;
+        unsigned_vector     m_objectives_lim;
+        unsigned_vector     m_objectives_term_trail;
+        unsigned_vector     m_objectives_term_trail_lim;
         model_ref           m_model;
         model_converter_ref m_model_converter;
         obj_map<func_decl, unsigned> m_objective_fns;
@@ -96,19 +102,26 @@ namespace opt {
         tactic_ref          m_simplify;
     public:
         context(ast_manager& m);
-        ~context();
+        virtual ~context();
         unsigned add_soft_constraint(expr* f, rational const& w, symbol const& id);
         unsigned add_objective(app* t, bool is_max);
         void add_hard_constraint(expr* f) { m_hard_constraints.push_back(f);  }
 
-        lbool optimize();
+        virtual void push();
+        virtual void pop(unsigned n);
+        virtual bool empty() { return m_objectives.empty(); }
+        virtual void set_cancel(bool f);
+        virtual void reset_cancel() { set_cancel(false); }
+        virtual void cancel() { set_cancel(true); }
+        virtual void set_hard_constraints(ptr_vector<expr> & hard);
+        virtual lbool optimize();
+        virtual void get_model(model_ref& m);
+        virtual void collect_statistics(statistics& stats) const;
+        virtual proof* get_proof() { return 0; }
+        virtual void get_labels(svector<symbol> & r) {}
+        virtual void get_unsat_core(ptr_vector<expr> & r) {}
+        virtual std::string reason_unknown() const { return std::string("unknown"); }
 
-        void get_model(model_ref& m);
-
-        void set_cancel(bool f);
-        void reset_cancel() { set_cancel(false); }
-        void cancel() { set_cancel(true); }
-        void collect_statistics(statistics& stats) const;
         void display_assignment(std::ostream& out);
         void display_range_assignment(std::ostream& out);
         static void collect_param_descrs(param_descrs & r);
@@ -153,6 +166,8 @@ namespace opt {
 
         opt_solver& get_solver();
 
+        bool is_numeral(expr* e, rational& n) const;
+
         void display_objective(std::ostream& out, objective const& obj) const;
         void display_bounds(std::ostream& out, bounds_t const& b) const;
 
diff --git a/src/opt/optsmt.cpp b/src/opt/optsmt.cpp
index 26f8116a0..7177c7679 100644
--- a/src/opt/optsmt.cpp
+++ b/src/opt/optsmt.cpp
@@ -51,7 +51,7 @@ namespace opt {
 
 
     void optsmt::set_cancel(bool f) {
-        m_cancel = true;
+        m_cancel = f;
     }
 
     void optsmt::set_max(vector<inf_eps>& dst, vector<inf_eps> const& src) {
@@ -379,5 +379,13 @@ namespace opt {
         m_engine = _p.engine();        
     }
 
+    void optsmt::reset() {
+        m_lower.reset();
+        m_upper.reset();
+        m_objs.reset();
+        m_vars.reset();
+        m_model.reset();
+        m_s = 0;
+    }
 }
 
diff --git a/src/opt/optsmt.h b/src/opt/optsmt.h
index ccb7de1b5..060ae9aaa 100644
--- a/src/opt/optsmt.h
+++ b/src/opt/optsmt.h
@@ -61,6 +61,8 @@ namespace opt {
         void    get_model(model_ref& mdl);
 
         void update_lower(unsigned idx, rational const& r);
+
+        void reset();
         
     private: