diff --git a/src/ast/datatype_decl_plugin.h b/src/ast/datatype_decl_plugin.h
index aa139b4a96e..77c5d748bf0 100644
--- a/src/ast/datatype_decl_plugin.h
+++ b/src/ast/datatype_decl_plugin.h
@@ -14,10 +14,11 @@ Module Name:
     Nikolaj Bjorner (nbjorner) 2017-9-1 
 
 Revision History:
-
+   
     rewritten to support SMTLIB-2.6 parameters from
      Leonardo de Moura (leonardo) 2008-01-09.
 
+
 --*/
 #ifndef DATATYPE_DECL_PLUGIN_H_
 #define DATATYPE_DECL_PLUGIN_H_
diff --git a/src/ast/recfun_decl_plugin.cpp b/src/ast/recfun_decl_plugin.cpp
index 81ca04b33fc..651ecce1097 100644
--- a/src/ast/recfun_decl_plugin.cpp
+++ b/src/ast/recfun_decl_plugin.cpp
@@ -239,7 +239,6 @@ namespace recfun {
         st.push_branch(branch(st.mk_unfold_lst(rhs)));        
 
         while (! st.empty()) {
-            TRACEFN("main loop iter");
 
             branch b = st.pop_branch();
 
@@ -254,7 +253,6 @@ namespace recfun {
                 while (! stack.empty()) {
                     expr * e = stack.back();
                     stack.pop_back();
-                    TRACEFN("unfold: " << mk_pp(e, m));
 
                     if (m.is_ite(e)) {
                         // need to do a case split on `e`, forking the search space
@@ -305,7 +303,6 @@ namespace recfun {
                 
                 // substitute, to get rid of `ite` terms
                 expr_ref case_rhs = subst(rhs);
-                TRACEFN("case_rhs: " << case_rhs);
                 for (unsigned i = 0; i < conditions.size(); ++i) {
                     conditions[i] = subst(conditions.get(i));
                 }
diff --git a/src/smt/smt_context.cpp b/src/smt/smt_context.cpp
index fd74e88dd25..c9430038707 100644
--- a/src/smt/smt_context.cpp
+++ b/src/smt/smt_context.cpp
@@ -3035,9 +3035,7 @@ namespace smt {
             return true;
         if (!is_app(assumption))
             return false;
-        if (to_app(assumption)->get_num_args() == 0)
-            return true;
-        if (m.is_not(assumption, arg) && is_app(arg) && to_app(arg)->get_num_args() == 0)
+        if (m.is_true(assumption) || m.is_false(assumption))
             return true;
         return false;
     }
@@ -3203,18 +3201,13 @@ namespace smt {
                 literal l = get_literal(curr_assumption);
                 if (l == true_literal)
                     continue;
-                if (l == false_literal) {
-                    set_conflict(b_justification::mk_axiom());
+                if (inconsistent())
                     break;
-                }
+                SASSERT(get_assignment(l) == l_true);
                 m_literal2assumption.insert(l.index(), orig_assumption);
                 // internalize_assertion marked l as relevant.
                 SASSERT(is_relevant(l));
                 TRACE("assumptions", tout << l << ":" << curr_assumption << " " << mk_pp(orig_assumption, m) << "\n";);
-                if (m.proofs_enabled())
-                    assign(l, mk_justification(justification_proof_wrapper(*this, pr)));
-                else
-                    assign(l, b_justification::mk_axiom());
                 m_assumptions.push_back(l);
                 get_bdata(l.var()).m_assumption = true;                
             }
diff --git a/src/smt/smt_theory.cpp b/src/smt/smt_theory.cpp
index ee317818f90..902e5eacb10 100644
--- a/src/smt/smt_theory.cpp
+++ b/src/smt/smt_theory.cpp
@@ -139,6 +139,17 @@ namespace smt {
     }
 
 
+    void theory::log_axiom_instantiation(literal_vector const& ls) {
+        ast_manager& m = get_manager();
+        expr_ref_vector fmls(m);
+        expr_ref tmp(m);
+        for (literal l : ls) {
+            get_context().literal2expr(l, tmp);
+            fmls.push_back(tmp);
+        }
+        log_axiom_instantiation(mk_or(fmls));
+    }
+
     void theory::log_axiom_instantiation(app * r, unsigned axiom_id, unsigned num_bindings, app * const * bindings, unsigned pattern_id, const vector<std::tuple<enode *, enode *>> & used_enodes) {
         ast_manager & m = get_manager();
         app_ref _r(r, m);
diff --git a/src/smt/smt_theory.h b/src/smt/smt_theory.h
index 6213c438184..95d8bd3cf76 100644
--- a/src/smt/smt_theory.h
+++ b/src/smt/smt_theory.h
@@ -106,6 +106,20 @@ namespace smt {
                     th.log_axiom_instantiation(body);
                 }
             }
+
+            scoped_trace_stream(theory& th, std::function<literal_vector(void)>& fn): m(th.get_manager()) {
+                if (m.has_trace_stream()) {
+                    th.log_axiom_instantiation(fn());
+                }
+            }
+
+            scoped_trace_stream(theory& th, std::function<literal(void)>& fn): m(th.get_manager()) {
+                if (m.has_trace_stream()) {
+                    literal_vector ls;
+                    ls.push_back(fn());
+                    th.log_axiom_instantiation(ls);
+                }
+            }
             
             ~scoped_trace_stream() {
                 if (m.has_trace_stream()) {
@@ -419,6 +433,8 @@ namespace smt {
             log_axiom_instantiation(to_app(r), axiom_id, num_bindings, bindings, pattern_id, used_enodes); 
         }
 
+        void log_axiom_instantiation(literal_vector const& ls);
+
         void log_axiom_instantiation(app * r, unsigned num_blamed_enodes, enode ** blamed_enodes) {
             vector<std::tuple<enode *, enode *>> used_enodes;
             for (unsigned i = 0; i < num_blamed_enodes; ++i) {
diff --git a/src/smt/theory_recfun.cpp b/src/smt/theory_recfun.cpp
index 70e8ffa6e2c..dd90a212748 100644
--- a/src/smt/theory_recfun.cpp
+++ b/src/smt/theory_recfun.cpp
@@ -42,7 +42,7 @@ namespace smt {
         }
 
     theory_recfun::~theory_recfun() {
-        reset_queues();
+        reset_eh();
     }
 
     char const * theory_recfun::get_name() const { return "recfun"; }
@@ -107,7 +107,7 @@ namespace smt {
             dealloc(e);
         }
         m_q_body_expand.reset();
-        m_q_clauses.clear();
+        m_q_clauses.clear();        
     }
 
     void theory_recfun::reset_eh() {
@@ -116,6 +116,11 @@ namespace smt {
         theory::reset_eh();
         m_disabled_guards.reset();
         m_enabled_guards.reset();
+        m_q_guards.reset();
+        for (auto & kv : m_guard2pending) {
+            dealloc(kv.m_value);
+        }
+        m_guard2pending.reset();
     }
 
     /*
@@ -164,11 +169,19 @@ namespace smt {
         return 
             !m_q_case_expand.empty() ||
             !m_q_body_expand.empty() ||
-            !m_q_clauses.empty();
+            !m_q_clauses.empty() ||
+            !m_q_guards.empty();
     }
     
     void theory_recfun::propagate() {
 
+        for (expr* g : m_q_guards) {
+            expr* ng = nullptr;
+            VERIFY(m.is_not(g, ng));
+            activate_guard(ng, *m_guard2pending[g]);
+        }
+        m_q_guards.reset();
+
         for (literal_vector & c : m_q_clauses) {
             TRACEFN("add axiom " << pp_lits(ctx(), c));
             ctx().mk_th_axiom(get_id(), c);
@@ -205,15 +218,18 @@ namespace smt {
      * make clause `depth_limit => ~guard`
      * the guard appears at a depth below the current cutoff.
      */
-    void theory_recfun::disable_guard(expr* guard) {
+    void theory_recfun::disable_guard(expr* guard, expr_ref_vector const& guards) {
         expr_ref nguard(m.mk_not(guard), m);
         if (is_disabled_guard(nguard)) 
             return;
+        SASSERT(!is_enabled_guard(nguard));
         literal_vector c;
         app_ref dlimit = m_util.mk_num_rounds_pred(m_num_rounds);
         c.push_back(~mk_literal(dlimit));
         c.push_back(~mk_literal(guard)); 
         m_disabled_guards.push_back(nguard);
+        SASSERT(!m_guard2pending.contains(nguard));
+        m_guard2pending.insert(nguard, alloc(expr_ref_vector, guards));
         TRACEFN("add clause\n" << pp_lits(ctx(), c));
         m_q_clauses.push_back(std::move(c));
     }
@@ -260,7 +276,7 @@ namespace smt {
         if (is_true && u().is_case_pred(e)) {
             TRACEFN("assign_case_pred_true " << mk_pp(e, m));
             // body-expand
-            push_body_expand(alloc(body_expansion, u(), to_app(e)));          
+            push_body_expand(alloc(body_expansion, u(), to_app(e)));            
         }
     }
 
@@ -319,7 +335,7 @@ namespace smt {
         unsigned depth = get_depth(e.m_lhs);
         expr_ref rhs(apply_args(depth, vars, e.m_args, e.m_def->get_rhs()), m);
         literal lit = mk_eq_lit(lhs, rhs);
-        std::function<expr*(void)> fn = [&]() { return ctx().bool_var2expr(lit.var()); };
+        std::function<literal(void)> fn = [&]() { return lit; };
         scoped_trace_stream _tr(*this, fn);
         ctx().mk_th_axiom(get_id(), 1, &lit);
         TRACEFN("macro expansion yields " << pp_lit(ctx(), lit));
@@ -338,52 +354,56 @@ namespace smt {
         SASSERT(e.m_def->is_fun_defined());
         // add case-axioms for all case-paths
         // assert this was not defined before.
-        auto & vars = e.m_def->get_vars();
         literal_vector preds;
-        expr_ref_vector pred_exprs(m);
+        auto & vars = e.m_def->get_vars();
+            
         for (recfun::case_def const & c : e.m_def->get_cases()) {
             // applied predicate to `args`
             app_ref pred_applied = c.apply_case_predicate(e.m_args);
-
-            unsigned depth = get_depth(e.m_lhs);
-            set_depth(depth, pred_applied);
             SASSERT(u().owns_app(pred_applied));
             literal concl = mk_literal(pred_applied);
             preds.push_back(concl);
-            pred_exprs.push_back(pred_applied);
 
+            unsigned depth = get_depth(e.m_lhs);
+            set_depth(depth, pred_applied);
+            expr_ref_vector guards(m);
+            for (auto & g : c.get_guards()) {
+                guards.push_back(apply_args(depth, vars, e.m_args, g));
+            }
             if (c.is_immediate()) {
                 body_expansion be(pred_applied, c, e.m_args);
                 assert_body_axiom(be);            
             }
             else if (!is_enabled_guard(pred_applied)) {
-                disable_guard(pred_applied);
+                disable_guard(pred_applied, guards);
                 continue;
             }
-            literal_vector guards;
-            expr_ref_vector exprs(m);
-            guards.push_back(concl);
-            for (auto & g : c.get_guards()) {
-                expr_ref ga = apply_args(depth, vars, e.m_args, g);
-                literal guard = mk_literal(ga);
-                guards.push_back(~guard);
-                exprs.push_back(m.mk_not(ga));
-                literal c[2] = {~concl, guard};
-                std::function<expr*(void)> fn = [&]() { return m.mk_implies(pred_applied, ga); };
-                scoped_trace_stream _tr(*this, fn);
-                ctx().mk_th_axiom(get_id(), 2, c);
-            }
-            std::function<expr*(void)> fn1 = [&]() { return m.mk_implies(m.mk_not(pred_applied), m.mk_or(exprs)); };
-            scoped_trace_stream _tr1(*this, fn1);
-            ctx().mk_th_axiom(get_id(), guards);
+            activate_guard(pred_applied, guards);
         }
         // the disjunction of branches is asserted
         // to close the available cases. 
-        std::function<expr*(void)> fn2 = [&]() { return m.mk_or(pred_exprs); };
+        std::function<literal_vector(void)> fn2 = [&]() { return preds; };
         scoped_trace_stream _tr2(*this, fn2);
         ctx().mk_th_axiom(get_id(), preds);
     }
 
+    void theory_recfun::activate_guard(expr* pred_applied, expr_ref_vector const& guards) {
+        literal concl = mk_literal(pred_applied);
+        literal_vector lguards;
+        lguards.push_back(concl);
+        for (expr* ga : guards) {
+            literal guard = mk_literal(ga);
+            lguards.push_back(~guard);
+            literal c[2] = {~concl, guard};
+            std::function<literal_vector(void)> fn = [&]() { return literal_vector(2, c); };
+            scoped_trace_stream _tr(*this, fn);
+            ctx().mk_th_axiom(get_id(), 2, c);
+        }
+        std::function<literal_vector(void)> fn1 = [&]() { return lguards; };
+        scoped_trace_stream _tr1(*this, fn1);
+        ctx().mk_th_axiom(get_id(), lguards);        
+    }
+
     /**
      * For a guarded definition guards => f(vars) = rhs
      * and occurrence f(args)
@@ -401,11 +421,9 @@ namespace smt {
         expr_ref lhs(u().mk_fun_defined(d, args), m);
         expr_ref rhs = apply_args(depth, vars, args, e.m_cdef->get_rhs());
         literal_vector clause;
-        expr_ref_vector exprs(m);
         for (auto & g : e.m_cdef->get_guards()) {
             expr_ref guard = apply_args(depth, vars, args, g);
             clause.push_back(~mk_literal(guard));
-            exprs.push_back(guard);
             if (clause.back() == true_literal) {
                 TRACEFN("body " << pp_body_expansion(e,m) << "\n" << clause << "\n" << guard);
                 return;
@@ -415,7 +433,7 @@ namespace smt {
             }
         }        
         clause.push_back(mk_eq_lit(lhs, rhs));
-        std::function<expr*(void)> fn = [&]() { return m.mk_implies(m.mk_and(exprs), m.mk_eq(lhs, rhs)); };
+        std::function<literal_vector(void)> fn = [&]() { return clause; };
         scoped_trace_stream _tr(*this, fn);
         ctx().mk_th_axiom(get_id(), clause);
         TRACEFN("body " << pp_body_expansion(e,m));
@@ -434,7 +452,7 @@ namespace smt {
     void theory_recfun::add_theory_assumptions(expr_ref_vector & assumptions) {
         if (u().has_defs() || !m_disabled_guards.empty()) {
             app_ref dlimit = m_util.mk_num_rounds_pred(m_num_rounds);
-            TRACEFN("add_theory_assumption " << mk_pp(dlimit.get(), m));
+            TRACEFN("add_theory_assumption " << dlimit);
             assumptions.push_back(dlimit);
             assumptions.append(m_disabled_guards);
         }
@@ -468,6 +486,7 @@ namespace smt {
             if (to_delete) {
                 m_disabled_guards.erase(to_delete);
                 m_enabled_guards.push_back(to_delete);
+                m_q_guards.push_back(to_delete);
                 IF_VERBOSE(1, verbose_stream() << "(smt.recfun :enable-guard)\n");
             }
             else {
diff --git a/src/smt/theory_recfun.h b/src/smt/theory_recfun.h
index 170fbb31dd8..62aa489b7ed 100644
--- a/src/smt/theory_recfun.h
+++ b/src/smt/theory_recfun.h
@@ -97,6 +97,7 @@ namespace smt {
         // book-keeping for depth of predicates
         expr_ref_vector          m_disabled_guards;
         expr_ref_vector          m_enabled_guards;
+        obj_map<expr, expr_ref_vector*> m_guard2pending;
         obj_map<expr, unsigned>  m_pred_depth;
         expr_ref_vector          m_preds;
         unsigned_vector          m_preds_lim;
@@ -104,7 +105,8 @@ namespace smt {
 
         ptr_vector<case_expansion> m_q_case_expand;
         ptr_vector<body_expansion> m_q_body_expand;
-        vector<literal_vector> m_q_clauses;
+        vector<literal_vector>     m_q_clauses;
+        ptr_vector<expr>           m_q_guards;
 
         bool is_enabled_guard(expr* guard) { expr_ref ng(m.mk_not(guard), m); return m_enabled_guards.contains(ng); }
         bool is_disabled_guard(expr* guard) { return m_disabled_guards.contains(guard); }
@@ -116,6 +118,8 @@ namespace smt {
         bool is_defined(enode * e) const { return is_defined(e->get_owner()); }
         bool is_case_pred(enode * e) const { return is_case_pred(e->get_owner()); }
 
+        void activate_guard(expr* guard, expr_ref_vector const& guards);
+
         void reset_queues();
         expr_ref apply_args(unsigned depth, recfun::vars const & vars, ptr_vector<expr> const & args, expr * e); //!< substitute variables by args
         void assert_macro_axiom(case_expansion & e);
@@ -123,7 +127,7 @@ namespace smt {
         void assert_body_axiom(body_expansion & e);
         literal mk_literal(expr* e);
 
-        void disable_guard(expr* guard);
+        void disable_guard(expr* guard, expr_ref_vector const& guards);
         unsigned get_depth(expr* e);
         void set_depth(unsigned d, expr* e);
         void set_depth_rec(unsigned d, expr* e);