diff --git a/src/ast/euf/euf_egraph.cpp b/src/ast/euf/euf_egraph.cpp
index 30dd1d720..8f04b1b00 100644
--- a/src/ast/euf/euf_egraph.cpp
+++ b/src/ast/euf/euf_egraph.cpp
@@ -571,6 +571,7 @@ namespace euf {
         m_updates.push_back(update_record(false, update_record::inconsistent()));
         m_n1 = n1;
         m_n2 = n2;
+        TRACE("euf", tout << "conflict " << bpp(n1) << " " << bpp(n2) << " " << j << "\n");
         m_justification = j;
     }
 
@@ -723,7 +724,7 @@ namespace euf {
         else if (j.is_congruence()) 
             push_congruence(a, b, j.is_commutative());
         if (cc && j.is_congruence()) 
-            cc->push_back(std::tuple(a, b, j.timestamp(), j.is_commutative()));
+            cc->push_back(std::tuple(a->get_app(), b->get_app(), j.timestamp(), j.is_commutative()));
     }
 
 
diff --git a/src/ast/euf/euf_egraph.h b/src/ast/euf/euf_egraph.h
index c0d7f03d8..53aaf481a 100644
--- a/src/ast/euf/euf_egraph.h
+++ b/src/ast/euf/euf_egraph.h
@@ -77,7 +77,7 @@ namespace euf {
     // It is the only information collected from justifications in order to
     // reconstruct EUF proofs. Transitivity, Symmetry of equality are not
     // tracked.
-    typedef std::tuple<enode*,enode*,uint64_t, bool> cc_justification_record;
+    typedef std::tuple<app*,app*,uint64_t, bool> cc_justification_record;
     typedef svector<cc_justification_record> cc_justification;
     
     class egraph {        
diff --git a/src/cmd_context/extra_cmds/proof_cmds.cpp b/src/cmd_context/extra_cmds/proof_cmds.cpp
index b90daf29a..c3269253f 100644
--- a/src/cmd_context/extra_cmds/proof_cmds.cpp
+++ b/src/cmd_context/extra_cmds/proof_cmds.cpp
@@ -52,153 +52,6 @@ Proof checker for clauses created during search.
 #include "params/solver_params.hpp"
 #include <iostream>
 
-class smt_checker {
-    ast_manager& m;
-    params_ref   m_params;
-
-    // for checking proof rules (hints)
-    euf::proof_checker m_checker;
-
-    // for fallback SMT checker
-    scoped_ptr<solver> m_solver;
-
-    // for RUP
-    symbol       m_rup;
-    sat::solver  m_sat_solver;
-    sat::drat    m_drat;
-    sat::literal_vector m_units;
-    sat::literal_vector m_clause;
-
-    void add_units() {
-        auto const& units = m_drat.units();
-        for (unsigned i = m_units.size(); i < units.size(); ++i)
-            m_units.push_back(units[i].first);
-    }
-
-public:
-    smt_checker(ast_manager& m):
-        m(m),
-        m_checker(m),
-        m_sat_solver(m_params, m.limit()), 
-        m_drat(m_sat_solver) 
-    {
-        m_params.set_bool("drat.check_unsat", true);
-        m_sat_solver.updt_params(m_params);
-        m_drat.updt_config();
-        m_solver = mk_smt_solver(m, m_params, symbol());
-        m_rup = symbol("rup");
-    }
-
-    bool is_rup(app* proof_hint) {
-        return
-            proof_hint &&
-            proof_hint->get_name() == m_rup;        
-    }
-
-    void mk_clause(expr_ref_vector const& clause) {
-        m_clause.reset();
-        for (expr* e : clause) {
-            bool sign = false;
-            while (m.is_not(e, e))
-                sign = !sign;
-            m_clause.push_back(sat::literal(e->get_id(), sign));
-        }
-    }
-
-    void mk_clause(expr* e) {
-        m_clause.reset();
-        bool sign = false;
-        while (m.is_not(e, e))
-            sign = !sign;
-        m_clause.push_back(sat::literal(e->get_id(), sign));
-    }
-    
-    bool check_rup(expr_ref_vector const& clause) {
-        add_units();
-        mk_clause(clause);
-        return m_drat.is_drup(m_clause.size(), m_clause.data(), m_units);
-    }
-
-    bool check_rup(expr* u) {
-        add_units();
-        mk_clause(u);
-        return m_drat.is_drup(m_clause.size(), m_clause.data(), m_units);
-    }
-
-    void add_clause(expr_ref_vector const& clause) {
-        mk_clause(clause);
-        m_drat.add(m_clause, sat::status::input());
-    }
-
-    void check(expr_ref_vector& clause, app* proof_hint) {
-        
-        if (is_rup(proof_hint) && check_rup(clause)) {
-            std::cout << "(verified-rup)\n";
-            return;
-        }
-
-        expr_ref_vector units(m);
-        if (m_checker.check(clause, proof_hint, units)) {
-            bool units_are_rup = true;
-            for (expr* u : units) {
-                if (!check_rup(u)) {
-                    std::cout << "unit " << mk_pp(u, m) << " is not rup\n";
-                    units_are_rup = false;
-                }
-            }
-            if (units_are_rup) {
-                std::cout << "(verified-" << proof_hint->get_name() << ")\n";
-                add_clause(clause);
-                return;
-            }
-        }
-
-        // extract a simplified verification condition in case proof validation does not work.
-        // quantifier instantiation can be validated as follows:
-        // If quantifier instantiation claims that (forall x . phi(x)) => psi using instantiation x -> t
-        // then check the simplified VC: phi(t) => psi.
-        // in case psi is the literal instantiation, then the clause is a propositional tautology.
-        // The VC function is a no-op if the proof hint does not have an associated vc generator.
-        expr_ref_vector vc(clause);
-        if (m_checker.vc(proof_hint, clause, vc)) {
-            std::cout << "(verified-" << proof_hint->get_name() << ")\n";
-            add_clause(clause);
-            return;
-        }
-        
-        m_solver->push();
-        for (expr* lit : vc)
-            m_solver->assert_expr(m.mk_not(lit));
-        lbool is_sat = m_solver->check_sat();
-        if (is_sat != l_false) {
-            std::cout << "did not verify: " << is_sat << " " << clause << "\n\n";
-            m_solver->display(std::cout);
-            if (is_sat == l_true) {
-                model_ref mdl;
-                m_solver->get_model(mdl);
-                std::cout << *mdl << "\n";
-            }                
-            exit(0);
-        }
-        m_solver->pop(1);
-        std::cout << "(verified-smt"; 
-        if (proof_hint) std::cout << "\n" << mk_bounded_pp(proof_hint, m, 4);
-        for (expr* arg : clause)
-            std::cout << "\n " << mk_bounded_pp(arg, m);
-        std::cout << ")\n";
-        add_clause(clause);
-    }
-
-    void assume(expr_ref_vector const& clause) {
-        add_clause(clause);
-        m_solver->assert_expr(mk_or(clause));
-    }
-
-    void del(expr_ref_vector const& clause) {
-
-    }
-
-};
 
 /**
  * Replay proof entierly, then walk backwards extracting reduced proof.
@@ -207,7 +60,7 @@ class proof_trim {
     cmd_context& ctx;
     ast_manager& m;
     sat::proof_trim trim;
-    euf::proof_checker m_checker;
+    euf::theory_checker m_checker;
     vector<expr_ref_vector> m_clauses;
     bool_vector             m_is_infer;
     symbol                  m_rup;
@@ -371,11 +224,11 @@ class proof_cmds_imp : public proof_cmds {
     bool            m_check  = true;
     bool            m_save   = false;
     bool            m_trim   = false;
-    scoped_ptr<smt_checker>     m_checker;
+    scoped_ptr<euf::smt_proof_checker>     m_checker;
     scoped_ptr<proof_saver>     m_saver;
     scoped_ptr<proof_trim>      m_trimmer;
     
-    smt_checker& checker() { if (!m_checker) m_checker = alloc(smt_checker, m); return *m_checker; }
+    euf::smt_proof_checker& checker() { params_ref p; if (!m_checker) m_checker = alloc(euf::smt_proof_checker, m, p); return *m_checker; }
     proof_saver& saver() { if (!m_saver) m_saver = alloc(proof_saver, ctx); return *m_saver; }
     proof_trim& trim() { if (!m_trimmer) m_trimmer = alloc(proof_trim, ctx); return *m_trimmer; }
     
@@ -404,7 +257,7 @@ public:
 
     void end_infer() override {
         if (m_check)
-            checker().check(m_lits, m_proof_hint);
+            checker().infer(m_lits, m_proof_hint);
         if (m_save)
             saver().infer(m_lits, m_proof_hint);
         if (m_trim)
diff --git a/src/model/model.cpp b/src/model/model.cpp
index dfa76db68..c89ff59a2 100644
--- a/src/model/model.cpp
+++ b/src/model/model.cpp
@@ -225,6 +225,20 @@ struct model::top_sort : public ::top_sort<func_decl> {
     }
 };
 
+void model::evaluate_constants() {
+    for (auto& [k, p] : m_interp) {
+        auto & [i, e] = p;
+        if (m.is_value(e))
+            continue;
+        expr_ref val(m);
+        val = (*this)(e);
+        m.dec_ref(e);
+        m.inc_ref(val);
+        p.second = val;
+    }
+}
+
+
 void model::compress(bool force_inline) {
     if (m_cleaned) return;
 
diff --git a/src/model/model.h b/src/model/model.h
index 07049a522..a93fc1b4f 100644
--- a/src/model/model.h
+++ b/src/model/model.h
@@ -94,6 +94,8 @@ public:
 
     void compress(bool force_inline = false);
 
+    void evaluate_constants();
+
     void set_model_completion(bool f) { m_mev.set_model_completion(f); }
     void updt_params(params_ref const & p);
 
diff --git a/src/sat/sat_config.cpp b/src/sat/sat_config.cpp
index d21ec5b93..2330fe401 100644
--- a/src/sat/sat_config.cpp
+++ b/src/sat/sat_config.cpp
@@ -198,7 +198,16 @@ namespace sat {
         m_drat_check_sat  = p.drat_check_sat();
         m_drat_file       = p.drat_file();
         m_smt_proof       = p.smt_proof();
-        m_drat            = !p.drat_disable() && (sp.lemmas2console() || m_drat_check_unsat || m_drat_file.is_non_empty_string() || m_smt_proof.is_non_empty_string() || m_drat_check_sat) && p.threads() == 1;
+        m_smt_proof_check = p.smt_proof_check();
+        m_smt_proof_check_rup = p.smt_proof_check_rup();
+        m_drat            =
+            !p.drat_disable()  && p.threads() == 1 &&
+            (sp.lemmas2console() ||
+             m_drat_check_unsat ||
+             m_drat_file.is_non_empty_string() ||
+             m_smt_proof.is_non_empty_string() ||
+             m_smt_proof_check ||
+             m_drat_check_sat);
         m_drat_binary     = p.drat_binary();
         m_drat_activity   = p.drat_activity();
         m_dyn_sub_res     = p.dyn_sub_res();
diff --git a/src/sat/sat_config.h b/src/sat/sat_config.h
index 7d98b092c..2d609b1bc 100644
--- a/src/sat/sat_config.h
+++ b/src/sat/sat_config.h
@@ -178,6 +178,8 @@ namespace sat {
         bool               m_drat_binary;
         symbol             m_drat_file;
         symbol             m_smt_proof;
+        bool               m_smt_proof_check;
+        bool               m_smt_proof_check_rup;
         bool               m_drat_check_unsat;
         bool               m_drat_check_sat;
         bool               m_drat_activity;
diff --git a/src/sat/sat_extension.h b/src/sat/sat_extension.h
index d6a956a32..8f15f5f68 100644
--- a/src/sat/sat_extension.h
+++ b/src/sat/sat_extension.h
@@ -89,7 +89,7 @@ namespace sat {
         virtual bool unit_propagate() = 0;        
         virtual bool is_external(bool_var v) { return false; }
         virtual double get_reward(literal l, ext_constraint_idx idx, literal_occs_fun& occs) const { return 0; }
-        virtual void get_antecedents(literal l, ext_justification_idx idx, literal_vector & r, bool probing) = 0;
+        virtual void get_antecedents(literal l, ext_justification_idx idx, literal_vector & r, bool probing, proof_hint*& ph) = 0;
         virtual bool is_extended_binary(ext_justification_idx idx, literal_vector & r) { return false; }
         virtual bool decide(bool_var& var, lbool& phase) { return false; }
         virtual bool get_case_split(bool_var& var, lbool& phase) { return false; }
diff --git a/src/sat/sat_params.pyg b/src/sat/sat_params.pyg
index 41bfa7afa..c35e97b92 100644
--- a/src/sat/sat_params.pyg
+++ b/src/sat/sat_params.pyg
@@ -48,6 +48,8 @@ def_module_params('sat',
                           ('dimacs.core', BOOL, False, 'extract core from DIMACS benchmarks'),
                           ('drat.disable', BOOL, False, 'override anything that enables DRAT'),
                           ('smt.proof', SYMBOL, '', 'add SMT proof to file'),
+                          ('smt.proof.check', BOOL, False, 'check SMT proof while it is created'),
+                          ('smt.proof.check_rup', BOOL, True, 'apply forward RUP proof checking'),
                           ('drat.file', SYMBOL, '', 'file to dump DRAT proofs'),
                           ('drat.binary', BOOL, False, 'use Binary DRAT output format'),
                           ('drat.check_unsat', BOOL, False, 'build up internal proof and check'),
diff --git a/src/sat/sat_solver.cpp b/src/sat/sat_solver.cpp
index d10e1124d..7f7b34ea8 100644
--- a/src/sat/sat_solver.cpp
+++ b/src/sat/sat_solver.cpp
@@ -402,8 +402,8 @@ namespace sat {
         extension::scoped_drating _sd(*m_ext.get());
         if (j.get_kind() == justification::EXT_JUSTIFICATION) 
             fill_ext_antecedents(lit, j, false);
-        TRACE("sat", tout << "drat-unit\n");
-        m_drat.add(lit, m_searching);
+        else 
+            m_drat.add(lit, m_searching);       
     }
 
     void solver::drat_log_clause(unsigned num_lits, literal const* lits, sat::status st) {
@@ -2890,7 +2890,8 @@ namespace sat {
         SASSERT(m_ext);
         auto idx = js.get_ext_justification_idx();
         m_ext_antecedents.reset();
-        m_ext->get_antecedents(consequent, idx, m_ext_antecedents, probing);
+        proof_hint* ph = nullptr;
+        m_ext->get_antecedents(consequent, idx, m_ext_antecedents, probing, ph);
     }
 
     bool solver::is_two_phase() const {
diff --git a/src/sat/smt/CMakeLists.txt b/src/sat/smt/CMakeLists.txt
index 6d75c0f1f..0b1e68e96 100644
--- a/src/sat/smt/CMakeLists.txt
+++ b/src/sat/smt/CMakeLists.txt
@@ -36,7 +36,7 @@ z3_add_component(sat_smt
     q_mam.cpp
     q_mbi.cpp
     q_model_fixer.cpp
-    q_proof_checker.cpp
+    q_theory_checker.cpp
     q_queue.cpp
     q_solver.cpp
     recfun_solver.cpp
diff --git a/src/sat/smt/arith_solver.cpp b/src/sat/smt/arith_solver.cpp
index f7e3f6293..5db5688b3 100644
--- a/src/sat/smt/arith_solver.cpp
+++ b/src/sat/smt/arith_solver.cpp
@@ -1476,7 +1476,7 @@ namespace arith {
         return r;
     }
 
-    void solver::get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing) {
+    void solver::get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing, sat::proof_hint*& ph) {
         auto& jst = euf::th_explain::from_index(idx);
         ctx.get_antecedents(l, jst, r, probing);
     }
diff --git a/src/sat/smt/arith_solver.h b/src/sat/smt/arith_solver.h
index 3d3f1ddd7..672477df2 100644
--- a/src/sat/smt/arith_solver.h
+++ b/src/sat/smt/arith_solver.h
@@ -485,7 +485,7 @@ namespace arith {
         solver(euf::solver& ctx, theory_id id);
         ~solver() override;
         bool is_external(bool_var v) override { return false; }
-        void get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing) override;
+        void get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing, sat::proof_hint*& ph) override;
         void asserted(literal l) override;
         sat::check_result check() override;
         void simplify() override {}
diff --git a/src/sat/smt/arith_proof_checker.h b/src/sat/smt/arith_theory_checker.h
similarity index 98%
rename from src/sat/smt/arith_proof_checker.h
rename to src/sat/smt/arith_theory_checker.h
index 0e5c891d5..f11e7ae29 100644
--- a/src/sat/smt/arith_proof_checker.h
+++ b/src/sat/smt/arith_theory_checker.h
@@ -34,7 +34,7 @@ The module assumes a limited repertoire of arithmetic proof rules.
 
 namespace arith {
 
-    class proof_checker : public euf::proof_checker_plugin {
+    class theory_checker : public euf::theory_checker_plugin {
         struct row {
             obj_map<expr, rational> m_coeffs;
             rational m_coeff;
@@ -304,7 +304,7 @@ namespace arith {
         }
         
     public:
-        proof_checker(ast_manager& m): 
+        theory_checker(ast_manager& m): 
             m(m), 
             a(m), 
             m_farkas("farkas"), 
@@ -468,7 +468,7 @@ namespace arith {
             return check();
         }
 
-        void register_plugins(euf::proof_checker& pc) override {
+        void register_plugins(euf::theory_checker& pc) override {
             pc.register_plugin(m_farkas, this);
             pc.register_plugin(m_bound, this);
             pc.register_plugin(m_implied_eq, this);
diff --git a/src/sat/smt/array_solver.h b/src/sat/smt/array_solver.h
index 5c2708842..f161af01a 100644
--- a/src/sat/smt/array_solver.h
+++ b/src/sat/smt/array_solver.h
@@ -278,7 +278,7 @@ namespace array {
         solver(euf::solver& ctx, theory_id id);
         ~solver() override;
         bool is_external(bool_var v) override { return false; }
-        void get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing) override {}
+        void get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing, sat::proof_hint*& ph) override {}
         void asserted(literal l) override {}
         sat::check_result check() override;
 
diff --git a/src/sat/smt/bv_solver.cpp b/src/sat/smt/bv_solver.cpp
index 8ef2c5cd5..631f954b1 100644
--- a/src/sat/smt/bv_solver.cpp
+++ b/src/sat/smt/bv_solver.cpp
@@ -306,7 +306,7 @@ namespace bv {
     bool solver::is_extended_binary(sat::ext_justification_idx idx, literal_vector& r) { return false; }
     bool solver::is_external(bool_var v) { return true; }
 
-    void solver::get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing) {
+    void solver::get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing, sat::proof_hint*& ph) {
         auto& c = bv_justification::from_index(idx);
         TRACE("bv", display_constraint(tout, idx) << "\n";);
         switch (c.m_kind) {
@@ -395,6 +395,7 @@ namespace bv {
         sat::literal leq1(s().num_vars() + 1, false);
         sat::literal leq2(s().num_vars() + 2, false);
         expr_ref eq1(m), eq2(m);
+        sat::proof_hint* ph = nullptr;
         if (c.m_kind == bv_justification::kind_t::bv2int) {
             eq1 = m.mk_eq(c.a->get_expr(), c.b->get_expr());
             eq2 = m.mk_eq(c.a->get_expr(), c.c->get_expr());
@@ -416,24 +417,24 @@ namespace bv {
             lits.push_back(c.m_consequent);
             break;
         case bv_justification::kind_t::ne2bit:
-            get_antecedents(c.m_consequent, c.to_index(), lits, true);
+            get_antecedents(c.m_consequent, c.to_index(), lits, true, ph);
             lits.push_back(c.m_consequent);
             break;
         case bv_justification::kind_t::bit2eq:      
-            get_antecedents(leq1, c.to_index(), lits, true);
+            get_antecedents(leq1, c.to_index(), lits, true, ph);
             for (auto& lit : lits)
                 lit.neg();
             lits.push_back(leq1);
             break;
         case bv_justification::kind_t::bit2ne: 
-            get_antecedents(c.m_consequent, c.to_index(), lits, true);
+            get_antecedents(c.m_consequent, c.to_index(), lits, true, ph);
             for (auto& lit : lits)
                 lit.neg();
             lits.push_back(c.m_consequent);            
             break;
         case bv_justification::kind_t::bv2int:
-            get_antecedents(leq1, c.to_index(), lits, true);
-            get_antecedents(leq2, c.to_index(), lits, true);
+            get_antecedents(leq1, c.to_index(), lits, true, ph);
+            get_antecedents(leq2, c.to_index(), lits, true, ph);
             for (auto& lit : lits)
                 lit.neg();
             lits.push_back(leq1);
diff --git a/src/sat/smt/bv_solver.h b/src/sat/smt/bv_solver.h
index 2c8fb4ae9..313679443 100644
--- a/src/sat/smt/bv_solver.h
+++ b/src/sat/smt/bv_solver.h
@@ -335,7 +335,7 @@ namespace bv {
         double get_reward(literal l, sat::ext_constraint_idx idx, sat::literal_occs_fun& occs) const override;
         bool is_extended_binary(sat::ext_justification_idx idx, literal_vector& r) override;
         bool is_external(bool_var v) override;
-        void get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector & r, bool probing) override;
+        void get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector & r, bool probing, sat::proof_hint*& ph) override;
         void asserted(literal l) override;
         sat::check_result check() override;
         void push_core() override;
diff --git a/src/sat/smt/dt_solver.cpp b/src/sat/smt/dt_solver.cpp
index a87f8770b..80846ec58 100644
--- a/src/sat/smt/dt_solver.cpp
+++ b/src/sat/smt/dt_solver.cpp
@@ -755,7 +755,7 @@ namespace dt {
         SASSERT(m_find.get_num_vars() == get_num_vars());
     }
 
-    void solver::get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing) {
+    void solver::get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing, sat::proof_hint*& ph) {
         auto& jst = euf::th_explain::from_index(idx);
         ctx.get_antecedents(l, jst, r, probing);
     }
diff --git a/src/sat/smt/dt_solver.h b/src/sat/smt/dt_solver.h
index 4e2524f6b..136e40eac 100644
--- a/src/sat/smt/dt_solver.h
+++ b/src/sat/smt/dt_solver.h
@@ -140,7 +140,7 @@ namespace dt {
         ~solver() override;
 
         bool is_external(bool_var v) override { return false; }
-        void get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing) override;
+        void get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing, sat::proof_hint*& ph) override;
         void asserted(literal l) override;
         sat::check_result check() override;
 
diff --git a/src/sat/smt/euf_ackerman.cpp b/src/sat/smt/euf_ackerman.cpp
index c8639e302..2026120e4 100644
--- a/src/sat/smt/euf_ackerman.cpp
+++ b/src/sat/smt/euf_ackerman.cpp
@@ -20,7 +20,7 @@ Author:
 
 namespace euf {
 
-    ackerman::ackerman(solver& s, ast_manager& m): s(s), m(m) {
+    ackerman::ackerman(solver& ctx, ast_manager& m): ctx(ctx), m(m) {
         new_tmp();
     }
 
@@ -100,31 +100,31 @@ namespace euf {
     }
 
     bool ackerman::enable_cc(app* a, app* b) {
-        if (!s.enable_ackerman_axioms(a))
+        if (!ctx.enable_ackerman_axioms(a))
             return false;
-        if (!s.enable_ackerman_axioms(b))
+        if (!ctx.enable_ackerman_axioms(b))
             return false;
         for (expr* arg : *a)
-            if (!s.enable_ackerman_axioms(arg))
+            if (!ctx.enable_ackerman_axioms(arg))
                 return false;
         for (expr* arg : *b)
-            if (!s.enable_ackerman_axioms(arg))
+            if (!ctx.enable_ackerman_axioms(arg))
                 return false;
         return true;
     }
 
     bool ackerman::enable_eq(expr* a, expr* b, expr* c) {
-        return s.enable_ackerman_axioms(a) && 
-            s.enable_ackerman_axioms(b) && 
-            s.enable_ackerman_axioms(c);           
+        return ctx.enable_ackerman_axioms(a) && 
+            ctx.enable_ackerman_axioms(b) && 
+            ctx.enable_ackerman_axioms(c);           
     }
 
     void ackerman::cg_conflict_eh(expr * n1, expr * n2) {
         if (!is_app(n1) || !is_app(n2))
             return;
-        if (!s.enable_ackerman_axioms(n1))
+        if (!ctx.enable_ackerman_axioms(n1))
             return;
-        SASSERT(!s.m_drating);
+        SASSERT(!ctx.m_drating);
         app* a = to_app(n1);
         app* b = to_app(n2);
         if (a->get_decl() != b->get_decl() || a->get_num_args() != b->get_num_args())
@@ -139,7 +139,7 @@ namespace euf {
     void ackerman::used_eq_eh(expr* a, expr* b, expr* c) {
         if (a == b || a == c || b == c)
             return;
-        if (s.m_drating)
+        if (ctx.m_drating)
             return;
         if (!enable_eq(a, b, c))
             return;
@@ -149,7 +149,7 @@ namespace euf {
     }
         
     void ackerman::used_cc_eh(app* a, app* b) {
-        if (s.m_drating)
+        if (ctx.m_drating)
             return;
         TRACE("ack", tout << "used cc: " << mk_pp(a, m) << " == " << mk_pp(b, m) << "\n";);
         SASSERT(a->get_decl() == b->get_decl());
@@ -162,7 +162,7 @@ namespace euf {
 
     void ackerman::gc() {
         m_num_propagations_since_last_gc++;
-        if (m_num_propagations_since_last_gc <= s.m_config.m_dack_gc) 
+        if (m_num_propagations_since_last_gc <= ctx.m_config.m_dack_gc) 
             return;
         m_num_propagations_since_last_gc = 0;
         
@@ -175,14 +175,14 @@ namespace euf {
     }
 
     void ackerman::propagate() {
-        SASSERT(s.s().at_base_lvl());
+        SASSERT(ctx.s().at_base_lvl());
         auto* n = m_queue;
         inference* k = nullptr;
-        unsigned num_prop = static_cast<unsigned>(s.s().get_stats().m_conflict * s.m_config.m_dack_factor);
+        unsigned num_prop = static_cast<unsigned>(ctx.s().get_stats().m_conflict * ctx.m_config.m_dack_factor);
         num_prop = std::min(num_prop, m_table.size());
         for (unsigned i = 0; i < num_prop; ++i, n = k) {
             k = n->next();
-            if (n->m_count < s.m_config.m_dack_threshold) 
+            if (n->m_count < ctx.m_config.m_dack_threshold) 
                 continue;
             if (n->m_count >= m_high_watermark && num_prop < m_table.size())
                 ++num_prop;
@@ -190,13 +190,13 @@ namespace euf {
                 add_cc(n->a, n->b);
             else 
                 add_eq(n->a, n->b, n->c);       
-            ++s.m_stats.m_ackerman;
+            ++ctx.m_stats.m_ackerman;
             remove(n);
         }
     }
 
     void ackerman::add_cc(expr* _a, expr* _b) {     
-        flet<bool> _is_redundant(s.m_is_redundant, true);
+        flet<bool> _is_redundant(ctx.m_is_redundant, true);
         app* a = to_app(_a);
         app* b = to_app(_b);
         TRACE("ack", tout << mk_pp(a, m) << " " << mk_pp(b, m) << "\n";);
@@ -204,24 +204,33 @@ namespace euf {
         unsigned sz = a->get_num_args();        
         
         for (unsigned i = 0; i < sz; ++i) {
-            expr_ref eq = s.mk_eq(a->get_arg(i), b->get_arg(i));
-            lits.push_back(~s.mk_literal(eq));
+            expr* ai = a->get_arg(i);
+            expr* bi = b->get_arg(i);
+            if (ai != bi) {
+                expr_ref eq = ctx.mk_eq(ai, bi);
+                lits.push_back(~ctx.mk_literal(eq));
+            }
         }
-        expr_ref eq = s.mk_eq(a, b);
-        lits.push_back(s.mk_literal(eq));
-        s.s().mk_clause(lits, sat::status::th(true, m.get_basic_family_id()));
+        expr_ref eq = ctx.mk_eq(a, b);
+        lits.push_back(ctx.mk_literal(eq));
+        th_proof_hint* ph = ctx.mk_cc_proof_hint(lits, a, b);
+        ctx.s().mk_clause(lits, sat::status::th(true, m.get_basic_family_id(), ph));                        
     }
 
     void ackerman::add_eq(expr* a, expr* b, expr* c) {
-        flet<bool> _is_redundant(s.m_is_redundant, true);
+        if (a == c || b == c)
+            return;
+        flet<bool> _is_redundant(ctx.m_is_redundant, true);
         sat::literal lits[3];
-        expr_ref eq1(s.mk_eq(a, c), m);
-        expr_ref eq2(s.mk_eq(b, c), m);
-        expr_ref eq3(s.mk_eq(a, b), m);
+        expr_ref eq1(ctx.mk_eq(a, c), m);
+        expr_ref eq2(ctx.mk_eq(b, c), m);
+        expr_ref eq3(ctx.mk_eq(a, b), m);
         TRACE("ack", tout << mk_pp(a, m) << " " << mk_pp(b, m) << " " << mk_pp(c, m) << "\n";);
-        lits[0] = ~s.mk_literal(eq1);
-        lits[1] = ~s.mk_literal(eq2);
-        lits[2] = s.mk_literal(eq3);
-        s.s().mk_clause(3, lits, sat::status::th(true, m.get_basic_family_id()));
+        lits[0] = ~ctx.mk_literal(eq1);
+        lits[1] = ~ctx.mk_literal(eq2);
+        lits[2] = ctx.mk_literal(eq3);
+        th_proof_hint* ph = ctx.mk_tc_proof_hint(lits);
+        ctx.s().mk_clause(3, lits, sat::status::th(true, m.get_basic_family_id(), ph));        
     }
+
 }
diff --git a/src/sat/smt/euf_ackerman.h b/src/sat/smt/euf_ackerman.h
index 17c7404f2..b5af2f689 100644
--- a/src/sat/smt/euf_ackerman.h
+++ b/src/sat/smt/euf_ackerman.h
@@ -52,14 +52,14 @@ namespace euf {
 
         typedef hashtable<inference*, inference_hash, inference_eq> table_t;
 
-        solver&       s;
+        solver&       ctx;
         ast_manager&  m;
         table_t       m_table;
-        inference*    m_queue { nullptr };
-        inference*    m_tmp_inference { nullptr };
-        unsigned      m_gc_threshold { 100 };
-        unsigned      m_high_watermark { 1000 };
-        unsigned      m_num_propagations_since_last_gc { 0 };
+        inference*    m_queue = nullptr;
+        inference*    m_tmp_inference = nullptr;
+        unsigned      m_gc_threshold = 100;
+        unsigned      m_high_watermark = 1000 ;
+        unsigned      m_num_propagations_since_last_gc = 0;
  
         void reset();
         void new_tmp();
@@ -75,7 +75,7 @@ namespace euf {
 
 
     public:
-        ackerman(solver& s, ast_manager& m);
+        ackerman(solver& ctx, ast_manager& m);
         ~ackerman();
 
         void cg_conflict_eh(expr * n1, expr * n2);
diff --git a/src/sat/smt/euf_proof.cpp b/src/sat/smt/euf_proof.cpp
index 8ee1a1d28..dbabb1a7b 100644
--- a/src/sat/smt/euf_proof.cpp
+++ b/src/sat/smt/euf_proof.cpp
@@ -27,13 +27,12 @@ namespace euf {
             get_drat().add_theory(m.get_basic_family_id(), symbol("bool"));
         }
         if (!m_proof_out && s().get_config().m_drat && 
-            (get_config().m_lemmas2console || s().get_config().m_smt_proof.is_non_empty_string())) {
+            (get_config().m_lemmas2console ||
+             s().get_config().m_smt_proof_check ||
+             s().get_config().m_smt_proof.is_non_empty_string())) {
             TRACE("euf", tout << "init-proof " << s().get_config().m_smt_proof << "\n");
             m_proof_out = alloc(std::ofstream, s().get_config().m_smt_proof.str(), std::ios_base::out);
-            if (get_config().m_lemmas2console) 
-                get_drat().set_clause_eh(*this);
-            if (s().get_config().m_smt_proof.is_non_empty_string()) 
-                get_drat().set_clause_eh(*this);
+            get_drat().set_clause_eh(*this);
         }
         m_proof_initialized = true;
     }
@@ -90,6 +89,46 @@ namespace euf {
         return new (get_region()) eq_proof_hint(m_lit_head, m_lit_tail, m_cc_head, m_cc_tail);
     }
 
+    th_proof_hint* solver::mk_cc_proof_hint(sat::literal_vector const& ante, app* a, app* b) {
+        if (!use_drat())
+            return nullptr;
+        SASSERT(a->get_decl() == b->get_decl());
+        push(value_trail(m_lit_tail));
+        push(value_trail(m_cc_tail));
+        push(restore_size_trail(m_proof_literals));
+        push(restore_size_trail(m_explain_cc, m_explain_cc.size()));
+
+        for (auto lit : ante)
+            m_proof_literals.push_back(~lit);
+
+        m_explain_cc.push_back({a, b, 0, false});
+        
+        m_lit_head = m_lit_tail;
+        m_cc_head  = m_cc_tail;
+        m_lit_tail = m_proof_literals.size();
+        m_cc_tail  = m_explain_cc.size();
+        return new (get_region()) eq_proof_hint(m_lit_head, m_lit_tail, m_cc_head, m_cc_tail);        
+    }
+
+    th_proof_hint* solver::mk_tc_proof_hint(sat::literal const* clause) {
+        if (!use_drat())
+            return nullptr;
+        push(value_trail(m_lit_tail));
+        push(value_trail(m_cc_tail));
+        push(restore_size_trail(m_proof_literals));
+
+        for (unsigned i = 0; i < 3; ++i)
+            m_proof_literals.push_back(~clause[i]);
+
+        
+        m_lit_head = m_lit_tail;
+        m_cc_head  = m_cc_tail;
+        m_lit_tail = m_proof_literals.size();
+        m_cc_tail  = m_explain_cc.size();
+        return new (get_region()) eq_proof_hint(m_lit_head, m_lit_tail, m_cc_head, m_cc_tail);        
+    }
+
+
     expr* eq_proof_hint::get_hint(euf::solver& s) const {
         ast_manager& m = s.get_manager();
         func_decl_ref cc(m), cc_comm(m);
@@ -118,7 +157,7 @@ namespace euf {
         std::sort(s.m_explain_cc.data() + m_cc_head, s.m_explain_cc.data() + m_cc_tail, compare_ts);
         for (unsigned i = m_cc_head; i < m_cc_tail; ++i) {
             auto const& [a, b, ts, comm] = s.m_explain_cc[i];
-            args.push_back(cc_proof(comm, m.mk_eq(a->get_expr(), b->get_expr())));
+            args.push_back(cc_proof(comm, m.mk_eq(a, b)));
         }
         for (auto * arg : args)
             sorts.push_back(arg->get_sort());
@@ -126,6 +165,8 @@ namespace euf {
         func_decl* f = m.mk_func_decl(symbol("euf"), sorts.size(), sorts.data(), proof);
         return m.mk_app(f, args);
     }
+
+
     
     smt_proof_hint* solver::mk_smt_hint(symbol const& n, unsigned nl, literal const* lits, unsigned ne, expr_pair const* eqs, unsigned nd, expr_pair const* deqs) {
         if (!use_drat())
@@ -134,8 +175,14 @@ namespace euf {
         push(restore_size_trail(m_proof_literals));
         
         for (unsigned i = 0; i < nl; ++i)
-            if (sat::null_literal != lits[i])
+            if (sat::null_literal != lits[i]) {
+                if (!literal2expr(lits[i])) 
+                    IF_VERBOSE(0, verbose_stream() << lits[i] << "\n"; display(verbose_stream()));
+                
+
+                SASSERT(literal2expr(lits[i]));
                 m_proof_literals.push_back(lits[i]);
+            }
 
         push(value_trail(m_eq_tail));
         push(restore_size_trail(m_proof_eqs));
@@ -231,6 +278,7 @@ namespace euf {
         TRACE("euf", tout << "on-clause " << n << "\n");
         on_lemma(n, lits, st);
         on_proof(n, lits, st);
+        on_check(n, lits, st);
     }
 
     void solver::on_proof(unsigned n, literal const* lits, sat::status st) {
@@ -252,6 +300,21 @@ namespace euf {
             UNREACHABLE();
         out.flush();
     }
+
+    void solver::on_check(unsigned n, literal const* lits, sat::status st) {
+        if (!s().get_config().m_smt_proof_check)
+            return;
+        expr_ref_vector clause(m);
+        for (unsigned i = 0; i < n; ++i) 
+            clause.push_back(literal2expr(lits[i]));
+        auto hint = status2proof_hint(st);
+        if (st.is_asserted() || st.is_redundant())
+            m_smt_proof_checker.infer(clause, hint);
+        else if (st.is_deleted())
+            m_smt_proof_checker.del(clause);
+        else if (st.is_input())
+            m_smt_proof_checker.assume(clause);
+    }
         
     void solver::on_lemma(unsigned n, literal const* lits, sat::status st) {
         if (!get_config().m_lemmas2console) 
@@ -320,21 +383,21 @@ namespace euf {
         if (proof_hint)
             return display_expr(out << " ", proof_hint);
         else
-            return out;
+          return out;
     }
 
-    expr_ref solver::status2proof_hint(sat::status st) {
+    app_ref solver::status2proof_hint(sat::status st) {
         if (st.is_sat()) 
-            return expr_ref(m.mk_const("rup", m.mk_proof_sort()), m); // provable by reverse unit propagation
+            return app_ref(m.mk_const("rup", m.mk_proof_sort()), m); // provable by reverse unit propagation
         auto* h = reinterpret_cast<euf::th_proof_hint const*>(st.get_hint());
         if (!h)
-            return expr_ref(m);
+            return app_ref(m);
 
         expr* e = h->get_hint(*this);
         if (e)
-            return expr_ref(e, m);
+            return app_ref(to_app(e), m);
 
-        return expr_ref(m);        
+        return app_ref(m);        
     }
 
     std::ostream& solver::display_literals(std::ostream& out, unsigned n, literal const* lits) {
@@ -345,6 +408,7 @@ namespace euf {
                 k = m.mk_const(symbol(lits[i].var()), m.mk_bool_sort());
                 e = k;
             }
+            SASSERT(e);
             if (lits[i].sign())
                 display_expr(out << " (not ", e) << ")";
             else
diff --git a/src/sat/smt/euf_proof_checker.cpp b/src/sat/smt/euf_proof_checker.cpp
index e7a77df5c..98032a86b 100644
--- a/src/sat/smt/euf_proof_checker.cpp
+++ b/src/sat/smt/euf_proof_checker.cpp
@@ -20,11 +20,14 @@ Author:
 #include "ast/ast_util.h"
 #include "ast/ast_ll_pp.h"
 #include "ast/arith_decl_plugin.h"
+#include "smt/smt_solver.h"
+#include "sat/sat_params.hpp"
 #include "sat/smt/euf_proof_checker.h"
-#include "sat/smt/arith_proof_checker.h"
-#include "sat/smt/q_proof_checker.h"
+#include "sat/smt/arith_theory_checker.h"
+#include "sat/smt/q_theory_checker.h"
 #include "sat/smt/tseitin_proof_checker.h"
 
+
 namespace euf {
 
     /**
@@ -57,7 +60,7 @@ namespace euf {
      * union-find checker.
      */
 
-    class eq_proof_checker : public proof_checker_plugin {
+    class eq_theory_checker : public theory_checker_plugin {
         ast_manager&     m;
         arith_util       m_arith;
         expr_ref_vector  m_trail;
@@ -133,7 +136,7 @@ namespace euf {
         }                
 
     public:
-        eq_proof_checker(ast_manager& m): m(m), m_arith(m), m_trail(m) {}
+        eq_theory_checker(ast_manager& m): m(m), m_arith(m), m_trail(m) {}
 
         expr_ref_vector clause(app* jst) override {
             expr_ref_vector result(m);
@@ -208,7 +211,7 @@ namespace euf {
             return false;
         }
 
-        void register_plugins(proof_checker& pc) override {
+        void register_plugins(theory_checker& pc) override {
             pc.register_plugin(symbol("euf"), this);
         }
     };
@@ -219,12 +222,12 @@ namespace euf {
        The pivot occurs with opposite signs in proof1 and proof2
      */
 
-    class res_proof_checker : public proof_checker_plugin {
+    class res_checker : public theory_checker_plugin {
         ast_manager&   m;
-        proof_checker& pc;
+        theory_checker& pc;
 
     public:
-        res_proof_checker(ast_manager& m, proof_checker& pc): m(m), pc(pc) {}
+        res_checker(ast_manager& m, theory_checker& pc): m(m), pc(pc) {}
 
         bool check(app* jst) override {
             if (jst->get_num_args() != 3)
@@ -273,46 +276,46 @@ namespace euf {
             return result;
         }
 
-        void register_plugins(proof_checker& pc) override {
+        void register_plugins(theory_checker& pc) override {
             pc.register_plugin(symbol("res"), this);
         }
     };
 
-    proof_checker::proof_checker(ast_manager& m):
+    theory_checker::theory_checker(ast_manager& m):
         m(m) {
-        add_plugin(alloc(arith::proof_checker, m));
-        add_plugin(alloc(eq_proof_checker, m));
-        add_plugin(alloc(res_proof_checker, m, *this));
-        add_plugin(alloc(q::proof_checker, m));
-        add_plugin(alloc(smt_proof_checker_plugin, m, symbol("datatype"))); // no-op datatype proof checker
-        add_plugin(alloc(tseitin::proof_checker, m));
+        add_plugin(alloc(arith::theory_checker, m));
+        add_plugin(alloc(eq_theory_checker, m));
+        add_plugin(alloc(res_checker, m, *this));
+        add_plugin(alloc(q::theory_checker, m));
+        add_plugin(alloc(smt_theory_checker_plugin, m, symbol("datatype"))); // no-op datatype proof checker
+        add_plugin(alloc(tseitin::theory_checker, m));
     }
 
-    proof_checker::~proof_checker() {
+    theory_checker::~theory_checker() {
         for (auto& [k, v] : m_checked_clauses)
             dealloc(v);
     }
 
-    void proof_checker::add_plugin(proof_checker_plugin* p) {
+    void theory_checker::add_plugin(theory_checker_plugin* p) {
         m_plugins.push_back(p);
         p->register_plugins(*this);
     }
 
-    void proof_checker::register_plugin(symbol const& rule, proof_checker_plugin* p) {
+    void theory_checker::register_plugin(symbol const& rule, theory_checker_plugin* p) {
         m_map.insert(rule, p);
     }
 
-    bool proof_checker::check(expr* e) {
+    bool theory_checker::check(expr* e) {
         if (!e || !is_app(e))
             return false;
         if (m_checked_clauses.contains(e))
             return true;        
         app* a = to_app(e);
-        proof_checker_plugin* p = nullptr;
+        theory_checker_plugin* p = nullptr;
         return m_map.find(a->get_decl()->get_name(), p) && p->check(a);
     }
 
-    expr_ref_vector proof_checker::clause(expr* e) {
+    expr_ref_vector theory_checker::clause(expr* e) {
         expr_ref_vector* rr;
         if (m_checked_clauses.find(e, rr))
             return *rr;
@@ -322,17 +325,17 @@ namespace euf {
         return r;
     }
 
-    bool proof_checker::vc(expr* e, expr_ref_vector const& clause, expr_ref_vector& v) {
+    bool theory_checker::vc(expr* e, expr_ref_vector const& clause, expr_ref_vector& v) {
         SASSERT(is_app(e));
         app* a = to_app(e);
-        proof_checker_plugin* p = nullptr;
+        theory_checker_plugin* p = nullptr;
         if (m_map.find(a->get_name(), p))
             return p->vc(a, clause, v);
         IF_VERBOSE(10, verbose_stream() << "there is no proof plugin for " << mk_pp(e, m) << "\n");
         return false;
     }
    
-    bool proof_checker::check(expr_ref_vector const& clause1, expr* e, expr_ref_vector & units) {
+    bool theory_checker::check(expr_ref_vector const& clause1, expr* e, expr_ref_vector & units) {
         if (!check(e))
             return false;
         units.reset();
@@ -358,13 +361,166 @@ namespace euf {
         return true;
     }
 
-    expr_ref_vector smt_proof_checker_plugin::clause(app* jst) {
+    expr_ref_vector smt_theory_checker_plugin::clause(app* jst) {
         expr_ref_vector result(m);
         SASSERT(jst->get_name() == m_rule);
         for (expr* arg : *jst) 
             result.push_back(mk_not(m, arg));
         return result;
     }
+
+
+    smt_proof_checker::smt_proof_checker(ast_manager& m, params_ref const& p):
+        m(m),
+        m_params(p),
+        m_checker(m),
+        m_sat_solver(m_params, m.limit()), 
+        m_drat(m_sat_solver) 
+    {
+        m_params.set_bool("drat.check_unsat", true);
+        m_params.set_bool("euf", false);
+        m_sat_solver.updt_params(m_params);
+        m_drat.updt_config();        
+        m_rup = symbol("rup");
+        sat_params sp(m_params);
+        m_check_rup = sp.smt_proof_check_rup();
+    }
+
+    void smt_proof_checker::ensure_solver() {
+        if (!m_solver)
+            m_solver = mk_smt_solver(m, m_params, symbol());
+    }
+
+
+    void smt_proof_checker::log_verified(app* proof_hint) {
+        symbol n = proof_hint->get_name();
+        if (n == m_last_rule) {
+            ++m_num_last_rules;
+            return;
+        }
+        if (m_num_last_rules > 0) 
+            std::cout << "(verified-" << m_last_rule << "+" << m_num_last_rules << ")\n";
+        
+        std::cout << "(verified-" << n << ")\n";
+        m_last_rule = n;
+        m_num_last_rules = 0;
+
+    }
+
+    bool smt_proof_checker::check_rup(expr_ref_vector const& clause) {
+        if (!m_check_rup)
+            return true;
+        add_units();                          
+        mk_clause(clause);
+        return m_drat.is_drup(m_clause.size(), m_clause.data(), m_units);
+    }
+
+    bool smt_proof_checker::check_rup(expr* u) {
+        if (!m_check_rup)
+            return true;
+        add_units();
+        mk_clause(u);
+        return m_drat.is_drup(m_clause.size(), m_clause.data(), m_units);
+    }
+
+    void smt_proof_checker::infer(expr_ref_vector& clause, app* proof_hint) {
+            
+        if (is_rup(proof_hint) && check_rup(clause)) {
+            if (m_check_rup) {
+                log_verified(proof_hint);
+                add_clause(clause);
+            }
+            return;
+        }
+        
+        expr_ref_vector units(m);
+        if (m_checker.check(clause, proof_hint, units)) {
+            bool units_are_rup = true;
+            for (expr* u : units) {
+                if (!check_rup(u)) {
+                    std::cout << "unit " << mk_bounded_pp(u, m) << " is not rup\n";
+                    units_are_rup = false;
+                }
+            }
+            if (units_are_rup) {
+                log_verified(proof_hint);
+                add_clause(clause);
+                return;
+            }
+        }
+        
+        // extract a simplified verification condition in case proof validation does not work.
+        // quantifier instantiation can be validated as follows:
+        // If quantifier instantiation claims that (forall x . phi(x)) => psi using instantiation x -> t
+        // then check the simplified VC: phi(t) => psi.
+        // in case psi is the literal instantiation, then the clause is a propositional tautology.
+        // The VC function is a no-op if the proof hint does not have an associated vc generator.
+        expr_ref_vector vc(clause);
+        if (m_checker.vc(proof_hint, clause, vc)) {
+            log_verified(proof_hint);
+            add_clause(clause);
+            return;
+        }
+        
+        ensure_solver();
+        m_solver->push();
+        for (expr* lit : vc)
+            m_solver->assert_expr(m.mk_not(lit));
+        lbool is_sat = m_solver->check_sat();
+        if (is_sat != l_false) {
+            std::cout << "did not verify: " << is_sat << " " << clause << "\n";
+            if (proof_hint) 
+                std::cout << "hint: " << mk_bounded_pp(proof_hint, m, 4) << "\n";
+            m_solver->display(std::cout);
+            if (is_sat == l_true) {
+                model_ref mdl;
+                m_solver->get_model(mdl);
+                mdl->evaluate_constants();
+                std::cout << *mdl << "\n";
+            }                
+            exit(0);
+        }
+        m_solver->pop(1);
+        std::cout << "(verified-smt"; 
+        if (proof_hint) std::cout << "\n" << mk_bounded_pp(proof_hint, m, 4);
+        for (expr* arg : clause)
+            std::cout << "\n " << mk_bounded_pp(arg, m);
+        std::cout << ")\n";
+        if (is_rup(proof_hint)) 
+            diagnose_rup_failure(clause);
+            
+        add_clause(clause);
+    }
+
+    void smt_proof_checker::diagnose_rup_failure(expr_ref_vector const& clause) {
+        expr_ref_vector fmls(m), assumptions(m), core(m);
+        m_solver->get_assertions(fmls);
+        for (unsigned i = 0; i < fmls.size(); ++i) {
+            assumptions.push_back(m.mk_fresh_const("a", m.mk_bool_sort()));
+            fmls[i] = m.mk_implies(assumptions.back(), fmls.get(i));
+        }
+            
+        ref<::solver> core_solver = mk_smt_solver(m, m_params, symbol());
+        // core_solver->assert_expr(fmls);
+        core_solver->assert_expr(m.mk_not(mk_or(clause)));
+        lbool ch = core_solver->check_sat(assumptions);
+        std::cout << "failed to verify\n" << clause << "\n";
+        if (ch == l_false) {
+            core_solver->get_unsat_core(core);
+            std::cout << "core\n";
+            for (expr* f : core)
+                std::cout << mk_pp(f, m) << "\n";
+        }
+        SASSERT(false);
+        
+        exit(0);
+    }
+
+    void smt_proof_checker::collect_statistics(statistics& st) const {
+        if (m_solver)
+            m_solver->collect_statistics(st);
+
+    }
     
 }
 
diff --git a/src/sat/smt/euf_proof_checker.h b/src/sat/smt/euf_proof_checker.h
index 8b1b5d671..6d5cb3290 100644
--- a/src/sat/smt/euf_proof_checker.h
+++ b/src/sat/smt/euf_proof_checker.h
@@ -19,30 +19,35 @@ Author:
 #include "util/map.h"
 #include "util/scoped_ptr_vector.h"
 #include "ast/ast.h"
+#include "ast/ast_util.h"
+#include "solver/solver.h"
+#include "sat/sat_solver.h"
+#include "sat/sat_drat.h"
+
 
 namespace euf {
 
-    class proof_checker;
+    class theory_checker;
 
-    class proof_checker_plugin {
+    class theory_checker_plugin {
     public:
-        virtual ~proof_checker_plugin() {}
+        virtual ~theory_checker_plugin() {}
         virtual bool check(app* jst) = 0;
         virtual expr_ref_vector clause(app* jst) = 0;
-        virtual void register_plugins(proof_checker& pc) = 0;
-        virtual bool vc(app* jst, expr_ref_vector const& clause, expr_ref_vector& v) { return false; }
+        virtual void register_plugins(theory_checker& pc) = 0;
+        virtual bool vc(app* jst, expr_ref_vector const& clause, expr_ref_vector& v) { v.reset(); v.append(this->clause(jst)); return false; }
     };
 
-    class proof_checker {
+    class theory_checker {
         ast_manager& m;
-        scoped_ptr_vector<proof_checker_plugin> m_plugins;                          // plugins of proof checkers
-        map<symbol, proof_checker_plugin*, symbol_hash_proc, symbol_eq_proc> m_map; // symbol table of proof checkers
+        scoped_ptr_vector<theory_checker_plugin> m_plugins;                          // plugins of proof checkers
+        map<symbol, theory_checker_plugin*, symbol_hash_proc, symbol_eq_proc> m_map; // symbol table of proof checkers
         obj_map<expr, expr_ref_vector*> m_checked_clauses;                          // cache of previously checked proofs and their clauses.
-        void add_plugin(proof_checker_plugin* p);
+        void add_plugin(theory_checker_plugin* p);
     public:
-        proof_checker(ast_manager& m);
-        ~proof_checker();
-        void register_plugin(symbol const& rule, proof_checker_plugin*);
+        theory_checker(ast_manager& m);
+        ~theory_checker();
+        void register_plugin(symbol const& rule, theory_checker_plugin*);
         bool check(expr* jst);
         expr_ref_vector clause(expr* jst);
         bool vc(expr* jst, expr_ref_vector const& clause, expr_ref_vector& v);
@@ -55,15 +60,107 @@ namespace euf {
        It provides shared implementations for clause and register_plugin.
        It overrides check to always fail.
      */
-    class smt_proof_checker_plugin : public proof_checker_plugin {
+    class smt_theory_checker_plugin : public theory_checker_plugin {
         ast_manager& m;
         symbol m_rule;
     public:
-        smt_proof_checker_plugin(ast_manager& m, symbol const& n): m(m), m_rule(n) {}
+        smt_theory_checker_plugin(ast_manager& m, symbol const& n): m(m), m_rule(n) {}
         bool check(app* jst) override { return false; }
         expr_ref_vector clause(app* jst) override;        
-        void register_plugins(proof_checker& pc) override { pc.register_plugin(m_rule, this); }
+        void register_plugins(theory_checker& pc) override { pc.register_plugin(m_rule, this); }
     };
 
+
+    class smt_proof_checker {
+        ast_manager& m;
+        params_ref   m_params;
+        
+        // for checking proof rules (hints)
+        euf::theory_checker m_checker;
+        
+        // for fallback SMT checker
+        scoped_ptr<::solver> m_solver;
+        
+        // for RUP
+        symbol       m_rup;
+        sat::solver  m_sat_solver;
+        sat::drat    m_drat;
+        sat::literal_vector m_units;
+        sat::literal_vector m_clause;
+        bool         m_check_rup = false;
+
+        // for logging
+        symbol       m_last_rule;
+        unsigned     m_num_last_rules = 0;
+        
+        void add_units() {
+            auto const& units = m_drat.units();
+            for (unsigned i = m_units.size(); i < units.size(); ++i)
+                m_units.push_back(units[i].first);
+        }
+
+        void log_verified(app* proof_hint);
+
+        void diagnose_rup_failure(expr_ref_vector const& clause);
+
+        void ensure_solver();
+        
+    public:
+        smt_proof_checker(ast_manager& m, params_ref const& p);
+        
+        bool is_rup(app* proof_hint) {
+            return
+                proof_hint &&
+                proof_hint->get_name() == m_rup;        
+        }
+        
+        void mk_clause(expr_ref_vector const& clause) {
+            m_clause.reset();
+            for (expr* e : clause) {
+                bool sign = false;
+                while (m.is_not(e, e))
+                    sign = !sign;
+                m_clause.push_back(sat::literal(e->get_id(), sign));
+            }
+        }
+        
+        void mk_clause(expr* e) {
+            m_clause.reset();
+            bool sign = false;
+            while (m.is_not(e, e))
+                sign = !sign;
+            m_clause.push_back(sat::literal(e->get_id(), sign));
+        }
+        
+        bool check_rup(expr_ref_vector const& clause);
+        
+        bool check_rup(expr* u);
+        
+        void add_clause(expr_ref_vector const& clause) {
+            if (!m_check_rup)
+                return;
+            mk_clause(clause);
+            m_drat.add(m_clause, sat::status::input());
+        }
+
+        void assume(expr_ref_vector const& clause) {
+            add_clause(clause);
+            if (!m_check_rup)
+                return;
+            ensure_solver();
+            m_solver->assert_expr(mk_or(clause));
+        }
+        
+        void del(expr_ref_vector const& clause) {            
+        }
+
+        
+        void infer(expr_ref_vector& clause, app* proof_hint);
+
+        void collect_statistics(statistics& st) const;
+        
+    };
+
+
 }
 
diff --git a/src/sat/smt/euf_solver.cpp b/src/sat/smt/euf_solver.cpp
index c29652803..cde3ef2e0 100644
--- a/src/sat/smt/euf_solver.cpp
+++ b/src/sat/smt/euf_solver.cpp
@@ -50,7 +50,8 @@ namespace euf {
         m_to_m(&m),
         m_to_si(&si),
         m_values(m),
-        m_clause_visitor(m)
+        m_clause_visitor(m),
+        m_smt_proof_checker(m, p)
     {
         updt_params(p);
         m_relevancy.set_enabled(get_config().m_relevancy_lvl > 2);
@@ -72,7 +73,7 @@ namespace euf {
 
     void solver::updt_params(params_ref const& p) {
         m_config.updt_params(p);
-            use_drat();
+        use_drat();
     }
 
     /**
@@ -215,19 +216,25 @@ namespace euf {
             x - 3 = 0 => x = 3 by arithmetic
             x = 3 => f(x) = f(3) by EUF
             resolve to produce clause x - 3 = 0 => f(x) = f(3)
+
+    The last argument to get_assumptions is a place-holder to retrieve a justification of a propagation.
+    Theory solver would have to populate this hint and the combined hint would have to be composed from the
+    sub-hints.
     */
 
-    void solver::get_antecedents(literal l, ext_justification_idx idx, literal_vector& r, bool probing) {
+    void solver::get_antecedents(literal l, ext_justification_idx idx, literal_vector& r, bool probing, sat::proof_hint*& ph) {
         m_egraph.begin_explain();
         m_explain.reset();
         if (use_drat() && !probing) 
             push(restore_size_trail(m_explain_cc, m_explain_cc.size()));
         auto* ext = sat::constraint_base::to_extension(idx);
+        th_proof_hint* hint = nullptr;
+        sat::proof_hint* shint = nullptr;
         bool has_theory = false;
         if (ext == this)
             get_antecedents(l, constraint::from_idx(idx), r, probing);
         else {
-            ext->get_antecedents(l, idx, r, probing);
+            ext->get_antecedents(l, idx, r, probing, shint);
             has_theory = true;
         }
         for (unsigned qhead = 0; qhead < m_explain.size(); ++qhead) {
@@ -239,20 +246,19 @@ namespace euf {
                 auto* ext = sat::constraint_base::to_extension(idx);
                 SASSERT(ext != this);
                 sat::literal lit = sat::null_literal;
-                ext->get_antecedents(lit, idx, r, probing);
+                ext->get_antecedents(lit, idx, r, probing, shint);
                 has_theory = true;
             }
         }
         m_egraph.end_explain();  
-        th_proof_hint* hint = nullptr;
-        if (use_drat() && !probing) {
-            if (has_theory) {                
-                r.push_back(~l);
-                hint = mk_smt_hint(symbol("smt"), r);
-                r.pop_back();
-            }
-            else
+        if (use_drat() && !probing)  {
+            if (!has_theory)
                 hint = mk_hint(l, r);
+            else {
+                if (l != sat::null_literal) r.push_back(~l);
+                hint = mk_smt_hint(symbol("smt"), r);
+                if (l != sat::null_literal) r.pop_back();
+            }
         }
         unsigned j = 0;
         for (sat::literal lit : r) 
@@ -957,6 +963,7 @@ namespace euf {
         m_egraph.collect_statistics(st);
         for (auto* e : m_solvers)
             e->collect_statistics(st);
+        m_smt_proof_checker.collect_statistics(st);
         st.update("euf ackerman", m_stats.m_ackerman);
         st.update("euf final check", m_stats.m_final_checks);
     }
diff --git a/src/sat/smt/euf_solver.h b/src/sat/smt/euf_solver.h
index bf18ca4bc..cedfcf2da 100644
--- a/src/sat/smt/euf_solver.h
+++ b/src/sat/smt/euf_solver.h
@@ -28,6 +28,7 @@ Author:
 #include "sat/smt/euf_ackerman.h"
 #include "sat/smt/user_solver.h"
 #include "sat/smt/euf_relevancy.h"
+#include "sat/smt/euf_proof_checker.h"
 #include "smt/params/smt_params.h"
 
 
@@ -203,19 +204,22 @@ namespace euf {
         unsigned m_eq_head = 0, m_eq_tail = 0, m_deq_head = 0, m_deq_tail = 0;
         eq_proof_hint* mk_hint(literal lit, literal_vector const& r);
 
+
         bool m_proof_initialized = false;
         void init_proof();
         ast_pp_util m_clause_visitor;
         bool m_display_all_decls = false;
+        smt_proof_checker m_smt_proof_checker;
         void on_clause(unsigned n, literal const* lits, sat::status st) override;
         void on_lemma(unsigned n, literal const* lits, sat::status st);
         void on_proof(unsigned n, literal const* lits, sat::status st);
+        void on_check(unsigned n, literal const* lits, sat::status st);
         std::ostream& display_literals(std::ostream& out, unsigned n, sat::literal const* lits);
         void display_assume(std::ostream& out, unsigned n, literal const* lits);
         void display_inferred(std::ostream& out, unsigned n, literal const* lits, expr* proof_hint);        
         void display_deleted(std::ostream& out, unsigned n, literal const* lits);
         std::ostream& display_hint(std::ostream& out, expr* proof_hint);
-        expr_ref status2proof_hint(sat::status st);
+        app_ref status2proof_hint(sat::status st);
 
         // relevancy
         bool is_propagated(sat::literal lit);
@@ -334,7 +338,7 @@ namespace euf {
         bool set_root(literal l, literal r) override;
         void flush_roots() override;
 
-        void get_antecedents(literal l, ext_justification_idx idx, literal_vector& r, bool probing) override;
+        void get_antecedents(literal l, ext_justification_idx idx, literal_vector& r, bool probing, sat::proof_hint*& ph) override;
         void get_antecedents(literal l, th_explain& jst, literal_vector& r, bool probing);
         void add_antecedent(bool probing, enode* a, enode* b);
         void add_diseq_antecedent(ptr_vector<size_t>& ex, cc_justification* cc, enode* a, enode* b);
@@ -400,6 +404,8 @@ namespace euf {
         smt_proof_hint* mk_smt_prop_hint(symbol const& n, literal lit, expr* a, expr* b) { expr_pair e(a, b); return mk_smt_hint(n, 1, &lit, 0, nullptr, 1, &e); }        
         smt_proof_hint* mk_smt_prop_hint(symbol const& n, literal lit, enode* a, enode* b) { return mk_smt_prop_hint(n, lit, a->get_expr(), b->get_expr()); }
         smt_proof_hint* mk_smt_hint(symbol const& n, enode* a, enode* b) { expr_pair e(a->get_expr(), b->get_expr()); return mk_smt_hint(n, 0, nullptr, 1, &e); }
+        th_proof_hint* mk_cc_proof_hint(sat::literal_vector const& ante, app* a, app* b);
+        th_proof_hint* mk_tc_proof_hint(sat::literal const* ternary_clause);
         sat::status mk_tseitin_status(sat::literal a, sat::literal b);
         sat::status mk_tseitin_status(unsigned n, sat::literal const* lits);
 
diff --git a/src/sat/smt/fpa_solver.h b/src/sat/smt/fpa_solver.h
index 38abb399d..537ae0895 100644
--- a/src/sat/smt/fpa_solver.h
+++ b/src/sat/smt/fpa_solver.h
@@ -71,7 +71,7 @@ namespace fpa {
         void finalize_model(model& mdl) override;
 
         bool unit_propagate() override;
-        void get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector& r, bool probing) override { UNREACHABLE(); }
+        void get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector& r, bool probing, sat::proof_hint*& ph) override { UNREACHABLE(); }
       sat::check_result check() override;
 
         euf::th_solver* clone(euf::solver& ctx) override { return alloc(solver, ctx); }
diff --git a/src/sat/smt/pb_solver.cpp b/src/sat/smt/pb_solver.cpp
index 1c762cb3f..2a29f07d5 100644
--- a/src/sat/smt/pb_solver.cpp
+++ b/src/sat/smt/pb_solver.cpp
@@ -722,7 +722,8 @@ namespace pb {
                 auto* ext = sat::constraint_base::to_extension(cindex);
                 if (ext != this) {
                     m_lemma.reset();
-                    ext->get_antecedents(consequent, idx, m_lemma, false);
+                    sat::proof_hint* ph = nullptr;
+                    ext->get_antecedents(consequent, idx, m_lemma, false, ph);
                     for (literal l : m_lemma) process_antecedent(~l, offset);
                     break;
                 }
@@ -1052,7 +1053,8 @@ namespace pb {
                 auto* ext = sat::constraint_base::to_extension(index);
                 if (ext != this) {
                     m_lemma.reset();
-                    ext->get_antecedents(consequent, index, m_lemma, false);
+                    sat::proof_hint* ph = nullptr;
+                    ext->get_antecedents(consequent, index, m_lemma, false, ph);
                     for (literal l : m_lemma) 
                         process_antecedent(~l, 1);
                     break;
@@ -1688,7 +1690,7 @@ namespace pb {
     // ----------------------------
     // constraint generic methods
 
-    void solver::get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector & r, bool probing) {
+    void solver::get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector & r, bool probing, sat::proof_hint*& ph) {
         get_antecedents(l, index2constraint(idx), r, probing);
     }
 
diff --git a/src/sat/smt/pb_solver.h b/src/sat/smt/pb_solver.h
index 09c0e47e0..9f9e6835c 100644
--- a/src/sat/smt/pb_solver.h
+++ b/src/sat/smt/pb_solver.h
@@ -377,7 +377,7 @@ namespace pb {
         bool propagated(literal l, sat::ext_constraint_idx idx) override;
         bool unit_propagate() override { return false; }
         lbool resolve_conflict() override;
-        void get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector & r, bool probing) override;
+        void get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector & r, bool probing, sat::proof_hint*& ph) override;
         void asserted(literal l) override;
         sat::check_result check() override;
         void push() override;
diff --git a/src/sat/smt/q_solver.cpp b/src/sat/smt/q_solver.cpp
index 7fd7be97e..7bddcbd9f 100644
--- a/src/sat/smt/q_solver.cpp
+++ b/src/sat/smt/q_solver.cpp
@@ -353,7 +353,7 @@ namespace q {
         return !m.is_and(arg) && !m.is_or(arg) && !m.is_iff(arg) && !m.is_implies(arg);
     }
 
-    void solver::get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector& r, bool probing) {
+    void solver::get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector& r, bool probing, sat::proof_hint*& ph) {
         m_ematch.get_antecedents(l, idx, r, probing);
     }
 
diff --git a/src/sat/smt/q_solver.h b/src/sat/smt/q_solver.h
index 3a95a00be..f199db610 100644
--- a/src/sat/smt/q_solver.h
+++ b/src/sat/smt/q_solver.h
@@ -83,7 +83,7 @@ namespace q {
 
         solver(euf::solver& ctx, family_id fid);
         bool is_external(sat::bool_var v) override { return false; }
-        void get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector& r, bool probing) override;
+        void get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector& r, bool probing, sat::proof_hint*& ph) override;
         void asserted(sat::literal l) override;
         sat::check_result check() override;
 
diff --git a/src/sat/smt/q_proof_checker.cpp b/src/sat/smt/q_theory_checker.cpp
similarity index 79%
rename from src/sat/smt/q_proof_checker.cpp
rename to src/sat/smt/q_theory_checker.cpp
index 8ddd3d75a..be246dd3c 100644
--- a/src/sat/smt/q_proof_checker.cpp
+++ b/src/sat/smt/q_theory_checker.cpp
@@ -3,7 +3,7 @@ Copyright (c) 2022 Microsoft Corporation
 
 Module Name:
 
-    q_proof_checker.cpp
+    q_theory_checker.cpp
 
 Abstract:
 
@@ -16,12 +16,12 @@ Author:
 --*/
 
 #include "ast/rewriter/var_subst.h"
-#include "sat/smt/q_proof_checker.h"
+#include "sat/smt/q_theory_checker.h"
 #include "sat/smt/q_solver.h"
 
 namespace q {
         
-    expr_ref_vector proof_checker::clause(app* jst) {
+    expr_ref_vector theory_checker::clause(app* jst) {
         expr_ref_vector result(m);
         for (expr* arg : *jst) 
             if (!is_bind(arg))
@@ -29,7 +29,7 @@ namespace q {
         return result;
     }
 
-    expr_ref_vector proof_checker::binding(app* jst) {
+    expr_ref_vector theory_checker::binding(app* jst) {
         expr_ref_vector result(m);
         for (expr* arg : *jst) 
             if (is_bind(arg)) {
@@ -39,7 +39,7 @@ namespace q {
         return result;        
     }
     
-    bool proof_checker::vc(app* jst, expr_ref_vector const& clause0, expr_ref_vector& v) {
+    bool theory_checker::vc(app* jst, expr_ref_vector const& clause0, expr_ref_vector& v) {
         expr* q = nullptr;
         if (!is_inst(jst))
             return false;
@@ -54,11 +54,11 @@ namespace q {
         return qi == clause1.get(1);
     }
 
-    bool proof_checker::is_inst(expr* jst) {
+    bool theory_checker::is_inst(expr* jst) {
         return is_app(jst) && to_app(jst)->get_name() == m_inst && m.mk_proof_sort() == jst->get_sort();
     }
 
-    bool proof_checker::is_bind(expr* e) {
+    bool theory_checker::is_bind(expr* e) {
         return is_app(e) && to_app(e)->get_name() == m_bind  && m.mk_proof_sort() == e->get_sort();
     }
 
diff --git a/src/sat/smt/q_proof_checker.h b/src/sat/smt/q_theory_checker.h
similarity index 83%
rename from src/sat/smt/q_proof_checker.h
rename to src/sat/smt/q_theory_checker.h
index 4072739c7..70c9938fe 100644
--- a/src/sat/smt/q_proof_checker.h
+++ b/src/sat/smt/q_theory_checker.h
@@ -3,7 +3,7 @@ Copyright (c) 2022 Microsoft Corporation
 
 Module Name:
 
-    q_proof_checker.h
+    q_theory_checker.h
 
 Abstract:
 
@@ -25,7 +25,7 @@ Author:
 
 namespace q {
 
-    class proof_checker : public euf::proof_checker_plugin {
+    class theory_checker : public euf::theory_checker_plugin {
         ast_manager& m;
         symbol       m_inst;
         symbol       m_bind;
@@ -37,7 +37,7 @@ namespace q {
         bool is_bind(expr* e);
         
     public:
-        proof_checker(ast_manager& m): 
+        theory_checker(ast_manager& m): 
             m(m),
             m_inst("inst"),
             m_bind("bind") {
@@ -47,7 +47,7 @@ namespace q {
 
         bool check(app* jst) override { return false; }
 
-        void register_plugins(euf::proof_checker& pc) override {
+        void register_plugins(euf::theory_checker& pc) override {
             pc.register_plugin(symbol("inst"), this);
         }
 
diff --git a/src/sat/smt/recfun_solver.cpp b/src/sat/smt/recfun_solver.cpp
index c88138d3f..ebb1ec7c1 100644
--- a/src/sat/smt/recfun_solver.cpp
+++ b/src/sat/smt/recfun_solver.cpp
@@ -180,7 +180,7 @@ namespace recfun {
         add_clause(clause);
     }
 
-    void solver::get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector& r, bool probing) {
+    void solver::get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector& r, bool probing, sat::proof_hint*& ph) {
         UNREACHABLE();
     }
 
diff --git a/src/sat/smt/recfun_solver.h b/src/sat/smt/recfun_solver.h
index 4e41a35a9..463aee6d6 100644
--- a/src/sat/smt/recfun_solver.h
+++ b/src/sat/smt/recfun_solver.h
@@ -92,7 +92,7 @@ namespace recfun {
         solver(euf::solver& ctx);
         ~solver() override;
         bool is_external(sat::bool_var v) override { return false; }
-        void get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector& r, bool probing) override;
+        void get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector& r, bool probing, sat::proof_hint*& ph) override;
         void asserted(sat::literal l) override;
         sat::check_result check() override;
         std::ostream& display(std::ostream& out) const override;
diff --git a/src/sat/smt/tseitin_proof_checker.cpp b/src/sat/smt/tseitin_proof_checker.cpp
index df0d60435..19f6e8660 100644
--- a/src/sat/smt/tseitin_proof_checker.cpp
+++ b/src/sat/smt/tseitin_proof_checker.cpp
@@ -32,13 +32,13 @@ TODOs:
 namespace tseitin {
 
         
-    expr_ref_vector proof_checker::clause(app* jst) {
+    expr_ref_vector theory_checker::clause(app* jst) {
         expr_ref_vector result(m);
         result.append(jst->get_num_args(), jst->get_args());
         return result;
     }
         
-    bool proof_checker::check(app* jst) {
+    bool theory_checker::check(app* jst) {
         expr* main_expr = nullptr;
         unsigned max_depth = 0;
         for (expr* arg : *jst) {
@@ -231,7 +231,7 @@ namespace tseitin {
         return false;
     }
 
-    bool proof_checker::equiv(expr* a, expr* b) {
+    bool theory_checker::equiv(expr* a, expr* b) {
         if (a == b)
             return true;
         if (!is_app(a) || !is_app(b))
diff --git a/src/sat/smt/tseitin_proof_checker.h b/src/sat/smt/tseitin_proof_checker.h
index 86a109ed8..8bbacd53b 100644
--- a/src/sat/smt/tseitin_proof_checker.h
+++ b/src/sat/smt/tseitin_proof_checker.h
@@ -25,7 +25,7 @@ Author:
 
 namespace tseitin {
 
-    class proof_checker : public euf::proof_checker_plugin {
+    class theory_checker : public euf::theory_checker_plugin {
         ast_manager& m;
 
         expr_fast_mark1 m_mark;
@@ -52,12 +52,12 @@ namespace tseitin {
         }
 
         struct scoped_mark {
-            proof_checker& pc;
-            scoped_mark(proof_checker& pc): pc(pc) {}
+            theory_checker& pc;
+            scoped_mark(theory_checker& pc): pc(pc) {}
             ~scoped_mark() { pc.m_mark.reset(); pc.m_nmark.reset(); }
         };
     public:
-        proof_checker(ast_manager& m): 
+        theory_checker(ast_manager& m): 
             m(m) {
         }
 
@@ -65,7 +65,7 @@ namespace tseitin {
         
         bool check(app* jst) override;
 
-        void register_plugins(euf::proof_checker& pc) override {
+        void register_plugins(euf::theory_checker& pc) override {
             pc.register_plugin(symbol("tseitin"), this);
         }
         
diff --git a/src/sat/smt/user_solver.cpp b/src/sat/smt/user_solver.cpp
index 5c98a6fac..34fd26c77 100644
--- a/src/sat/smt/user_solver.cpp
+++ b/src/sat/smt/user_solver.cpp
@@ -201,7 +201,7 @@ namespace user_solver {
         return sat::justification::mk_ext_justification(s().scope_lvl(), constraint->to_index());
     }
 
-    void solver::get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector & r, bool probing) {
+    void solver::get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector & r, bool probing, sat::proof_hint*& ph) {
         auto& j = justification::from_index(idx);
         auto const& prop = m_prop[j.m_propagation_index];
         for (unsigned id : prop.m_ids)
diff --git a/src/sat/smt/user_solver.h b/src/sat/smt/user_solver.h
index 28528b9a1..c996d1878 100644
--- a/src/sat/smt/user_solver.h
+++ b/src/sat/smt/user_solver.h
@@ -152,7 +152,7 @@ namespace user_solver {
         void push_core() override;
         void pop_core(unsigned n) override;
         bool unit_propagate() override;
-        void get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector & r, bool probing) override;
+        void get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector & r, bool probing, sat::proof_hint*& ph) override;
         void collect_statistics(statistics& st) const override;
         sat::literal internalize(expr* e, bool sign, bool root, bool learned) override;
         void internalize(expr* e, bool redundant) override;
diff --git a/src/shell/drat_frontend.cpp b/src/shell/drat_frontend.cpp
index 091d8cd4d..b0b711ef0 100644
--- a/src/shell/drat_frontend.cpp
+++ b/src/shell/drat_frontend.cpp
@@ -5,20 +5,14 @@ Copyright (c) 2020 Microsoft Corporation
 
 #include<iostream>
 #include<fstream>
-#include "ast/bv_decl_plugin.h"
 #include "util/memory_manager.h"
 #include "util/statistics.h"
+#include "ast/proofs/proof_checker.h"
+#include "ast/reg_decl_plugins.h"
 #include "sat/dimacs.h"
 #include "sat/sat_solver.h"
 #include "sat/sat_drat.h"
-#include "smt/smt_solver.h"
 #include "shell/drat_frontend.h"
-#include "parsers/smt2/smt2parser.h"
-#include "cmd_context/cmd_context.h"
-#include "ast/proofs/proof_checker.h"
-#include "ast/rewriter/th_rewriter.h"
-#include "ast/reg_decl_plugins.h"
-#include "sat/smt/arith_proof_checker.h"
 
 
 class drup_checker {
@@ -104,103 +98,3 @@ unsigned read_drat(char const* drat_file) {
     }
     return 0;
 }
-
-
-#if 0
-
-    bool validate_hint(expr_ref_vector const& exprs, sat::literal_vector const& lits, sat::proof_hint const& hint) {
-        arith_util autil(m);
-        arith::proof_checker achecker(m);
-        proof_checker pc(m);
-        switch (hint.m_ty) {
-        case sat::hint_type::null_h:
-            break;
-        case sat::hint_type::bound_h:
-        case sat::hint_type::farkas_h: 
-        case sat::hint_type::implied_eq_h: {
-            achecker.reset();
-            for (auto const& [a, b]: hint.m_eqs) {
-                expr* x = exprs[a];
-                expr* y = exprs[b];
-                achecker.add_eq(x, y);
-            }
-            for (auto const& [a, b]: hint.m_diseqs) {
-                expr* x = exprs[a];
-                expr* y = exprs[b];
-                achecker.add_diseq(x, y);
-            }
-            
-            unsigned sz = hint.m_literals.size();
-            for (unsigned i = 0; i < sz; ++i) {
-                auto const& [coeff, lit] = hint.m_literals[i];
-                app_ref e(to_app(m_b2e[lit.var()]), m);
-                if (i + 1 == sz && sat::hint_type::bound_h == hint.m_ty) {
-                    if (!achecker.add_conseq(coeff, e, lit.sign())) {
-                        std::cout << "p failed checking hint " << e << "\n";
-                        return false;
-                    }
-                    
-                }
-                else if (!achecker.add_ineq(coeff, e, lit.sign())) {
-                    std::cout << "p failed checking hint " << e << "\n";
-                    return false;
-                }
-            }
-
-            // achecker.display(std::cout << "checking\n");
-            bool ok = achecker.check();
-
-            if (!ok) {
-                rational lc(1);
-                for (auto const& [coeff, lit] : hint.m_literals) 
-                    lc = lcm(lc, denominator(coeff));
-                bool is_strict = false;
-                expr_ref sum(m);
-                for (auto const& [coeff, lit] : hint.m_literals) {
-                    app_ref e(to_app(m_b2e[lit.var()]), m);
-                    VERIFY(pc.check_arith_literal(!lit.sign(), e, coeff*lc, sum, is_strict));
-                    std::cout << "sum: " << sum << "\n";
-                }
-                sort* s = sum->get_sort();
-                if (is_strict) 
-                    sum = autil.mk_lt(sum, autil.mk_numeral(rational(0), s));
-                else 
-                    sum = autil.mk_le(sum, autil.mk_numeral(rational(0), s));
-                th_rewriter rw(m);
-                rw(sum);
-                std::cout << "sum: " << sum << "\n";
-                
-                for (auto const& [a, b]: hint.m_eqs) {
-                    expr* x = exprs[a];
-                    expr* y = exprs[b];
-                    app_ref e(m.mk_eq(x, y), m);
-                    std::cout << e << "\n";
-                }
-                for (auto const& [a, b]: hint.m_diseqs) {
-                    expr* x = exprs[a];
-                    expr* y = exprs[b];
-                    app_ref e(m.mk_not(m.mk_eq(x, y)), m);
-                    std::cout << e << "\n";
-                }
-                for (auto const& [coeff, lit] : hint.m_literals) {
-                    app_ref e(to_app(m_b2e[lit.var()]), m);
-                    if (lit.sign()) e = m.mk_not(e);
-                    std::cout << e << "\n";
-                }
-                achecker.display(std::cout);
-                std::cout << "p hint not verified\n";
-                return false;
-            }
-           
-            std::cout << "p hint verified\n";
-            return true;
-            break;
-        }
-        default:
-            UNREACHABLE();
-            break;
-        }
-        return false;
-    }
-
-#endif