diff --git a/.github/workflows/codeql-analysis.yml b/.github/workflows/codeql-analysis.yml
index 397145536..279bd2b99 100644
--- a/.github/workflows/codeql-analysis.yml
+++ b/.github/workflows/codeql-analysis.yml
@@ -20,18 +20,18 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v4
+      uses: actions/checkout@v5
 
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@v3
+      uses: github/codeql-action/init@v4
       with:
         languages: ${{ matrix.language }}
 
     - name: Autobuild
-      uses: github/codeql-action/autobuild@v3
+      uses: github/codeql-action/autobuild@v4
 
     - name: Run CodeQL Query
-      uses: github/codeql-action/analyze@v3
+      uses: github/codeql-action/analyze@v4
       with:
         category: 'custom'
         queries: ./codeql/custom-queries
\ No newline at end of file
diff --git a/.github/workflows/wasm-release.yml b/.github/workflows/wasm-release.yml
index 5bb45bbb8..b2bba5126 100644
--- a/.github/workflows/wasm-release.yml
+++ b/.github/workflows/wasm-release.yml
@@ -24,7 +24,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Setup node
-        uses: actions/setup-node@v5
+        uses: actions/setup-node@v6
         with:
           node-version: "lts/*"
           registry-url: "https://registry.npmjs.org"
diff --git a/.github/workflows/wasm.yml b/.github/workflows/wasm.yml
index d32862f08..b95e86289 100644
--- a/.github/workflows/wasm.yml
+++ b/.github/workflows/wasm.yml
@@ -24,7 +24,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Setup node
-        uses: actions/setup-node@v5
+        uses: actions/setup-node@v6
         with:
           node-version: "lts/*"
 
diff --git a/a-tst.gcno b/a-tst.gcno
deleted file mode 100644
index 3b9127650..000000000
Binary files a/a-tst.gcno and /dev/null differ
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 6368afdb4..0bf2aef61 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -66,6 +66,7 @@ jobs:
   pool:
     vmImage: "ubuntu-latest"
   container: "quay.io/pypa/manylinux2014_x86_64:latest"
+  condition: eq(0,1) 
   steps:
   - script: curl -L -o /tmp/arm-toolchain.tar.xz 'https://developer.arm.com/-/media/Files/downloads/gnu/11.2-2022.02/binrel/gcc-arm-11.2-2022.02-x86_64-aarch64-none-linux-gnu.tar.xz?rev=33c6e30e5ac64e6dba8f0431f2c35f1b&hash=9918A05BF47621B632C7A5C8D2BB438FB80A4480'
   - script: mkdir -p /tmp/arm-toolchain/
diff --git a/examples/c++/example.cpp b/examples/c++/example.cpp
index 06f3ffe3e..c3902dfff 100644
--- a/examples/c++/example.cpp
+++ b/examples/c++/example.cpp
@@ -1006,6 +1006,95 @@ void datatype_example() {
 
 }
 
+void polymorphic_datatype_example() {
+    std::cout << "polymorphic datatype example\n";
+    context ctx;
+
+    // Create type variables alpha and beta for polymorphic datatype using C API
+    Z3_symbol alpha_sym = Z3_mk_string_symbol(ctx, "alpha");
+    Z3_symbol beta_sym = Z3_mk_string_symbol(ctx, "beta");
+    sort alpha(ctx, Z3_mk_type_variable(ctx, alpha_sym));
+    sort beta(ctx, Z3_mk_type_variable(ctx, beta_sym));
+    
+    std::cout << "Type variables: " << alpha << ", " << beta << "\n";
+
+    // Define parametric Pair datatype with constructor mk-pair(first: alpha, second: beta)
+    symbol pair_name = ctx.str_symbol("Pair");
+    symbol mk_pair_name = ctx.str_symbol("mk-pair");
+    symbol is_pair_name = ctx.str_symbol("is-pair");
+    symbol first_name = ctx.str_symbol("first");
+    symbol second_name = ctx.str_symbol("second");
+    
+    symbol field_names[2] = {first_name, second_name};
+    sort field_sorts[2] = {alpha, beta};  // Use type variables
+    
+    constructors cs(ctx);
+    cs.add(mk_pair_name, is_pair_name, 2, field_names, field_sorts);
+    sort pair = ctx.datatype(pair_name, cs);
+    
+    std::cout << "Created parametric datatype: " << pair << "\n";
+    
+    // Instantiate Pair with concrete types: (Pair Int Real)
+    sort_vector params_int_real(ctx);
+    params_int_real.push_back(ctx.int_sort());
+    params_int_real.push_back(ctx.real_sort());
+    sort pair_int_real = ctx.datatype_sort(pair_name, params_int_real);
+    
+    std::cout << "Instantiated with Int and Real: " << pair_int_real << "\n";
+    
+    // Instantiate Pair with concrete types: (Pair Real Int)
+    sort_vector params_real_int(ctx);
+    params_real_int.push_back(ctx.real_sort());
+    params_real_int.push_back(ctx.int_sort());
+    sort pair_real_int = ctx.datatype_sort(pair_name, params_real_int);
+    
+    std::cout << "Instantiated with Real and Int: " << pair_real_int << "\n";
+    
+    // Get constructors and accessors for (Pair Int Real) using C API
+    func_decl mk_pair_ir(ctx, Z3_get_datatype_sort_constructor(ctx, pair_int_real, 0));
+    func_decl first_ir(ctx, Z3_get_datatype_sort_constructor_accessor(ctx, pair_int_real, 0, 0));
+    func_decl second_ir(ctx, Z3_get_datatype_sort_constructor_accessor(ctx, pair_int_real, 0, 1));
+    
+    std::cout << "Constructors and accessors for (Pair Int Real):\n";
+    std::cout << "  Constructor: " << mk_pair_ir << "\n";
+    std::cout << "  first accessor: " << first_ir << "\n";
+    std::cout << "  second accessor: " << second_ir << "\n";
+    
+    // Get constructors and accessors for (Pair Real Int) using C API
+    func_decl mk_pair_ri(ctx, Z3_get_datatype_sort_constructor(ctx, pair_real_int, 0));
+    func_decl first_ri(ctx, Z3_get_datatype_sort_constructor_accessor(ctx, pair_real_int, 0, 0));
+    func_decl second_ri(ctx, Z3_get_datatype_sort_constructor_accessor(ctx, pair_real_int, 0, 1));
+    
+    std::cout << "Constructors and accessors for (Pair Real Int):\n";
+    std::cout << "  Constructor: " << mk_pair_ri << "\n";
+    std::cout << "  first accessor: " << first_ri << "\n";
+    std::cout << "  second accessor: " << second_ri << "\n";
+    
+    // Create constants of these types
+    expr p1 = ctx.constant("p1", pair_int_real);
+    expr p2 = ctx.constant("p2", pair_real_int);
+    
+    std::cout << "Created constants: " << p1 << " : " << p1.get_sort() << "\n";
+    std::cout << "                   " << p2 << " : " << p2.get_sort() << "\n";
+    
+    // Create expressions using accessors
+    expr first_p1 = first_ir(p1);   // first(p1) has type Int
+    expr second_p2 = second_ri(p2); // second(p2) has type Int
+    
+    std::cout << "first(p1) = " << first_p1 << " : " << first_p1.get_sort() << "\n";
+    std::cout << "second(p2) = " << second_p2 << " : " << second_p2.get_sort() << "\n";
+    
+    // Create equality term: (= (first p1) (second p2))
+    expr eq = first_p1 == second_p2;
+    std::cout << "Equality term: " << eq << "\n";
+    
+    // Verify both sides have the same type (Int)
+    assert(first_p1.get_sort().id() == ctx.int_sort().id());
+    assert(second_p2.get_sort().id() == ctx.int_sort().id());
+    
+    std::cout << "Successfully created and verified polymorphic datatypes!\n";
+}
+
 void expr_vector_example() {
     std::cout << "expr_vector example\n";
     context c;
@@ -1394,6 +1483,7 @@ int main() {
         enum_sort_example(); std::cout << "\n";
         tuple_example(); std::cout << "\n";
         datatype_example(); std::cout << "\n";
+        polymorphic_datatype_example(); std::cout << "\n";
         expr_vector_example(); std::cout << "\n";
         exists_expr_vector_example(); std::cout << "\n";
         substitute_example(); std::cout << "\n";
diff --git a/param-tuning-experiment.py b/param-tuning-experiment.py
new file mode 100644
index 000000000..bdaf10ae6
--- /dev/null
+++ b/param-tuning-experiment.py
@@ -0,0 +1,254 @@
+from multiprocessing import Process
+import math, random
+
+import sys, os
+sys.path.insert(0, os.path.abspath("build/python"))
+os.environ["Z3_LIBRARY_PATH"] = os.path.abspath("build")
+
+# import z3
+# print("Using z3 from:", z3.__file__)
+
+from z3 import *
+
+MAX_CONFLICTS = 100
+MAX_EXAMPLES = 5
+bench_dir = "../z3-poly-testing/inputs/QF_NIA_small"
+
+BASE_PARAM_CANDIDATES = [
+    ("smt.arith.eager_eq_axioms", False),
+    ("smt.restart_factor", 1.2),
+    ("smt.relevancy", 0),
+    ("smt.phase_caching_off", 200),
+    ("smt.phase_caching_on", 600),
+]
+
+# --------------------------
+# One class: BatchManager
+# --------------------------
+class BatchManager:
+    def __init__(self):
+        self.best_param_state = None
+        self.best_score = (math.inf, math.inf, math.inf)
+        self.search_complete = False
+
+    def mark_complete(self):
+        self.search_complete = True
+
+    def maybe_update_best(self, param_state, triple):
+        if self._better(triple, self.best_score):
+            self.best_param_state = list(param_state)
+            self.best_score = triple
+
+    @staticmethod
+    def _better(a, b):
+        return a < b  # lexicographic compare
+
+
+# -------------------
+# Helpers
+# -------------------
+
+def solver_from_file(filepath):
+    s = Solver()
+    s.set("smt.auto_config", False)
+    s.from_file(filepath)
+    return s
+
+
+def apply_param_state(s, param_state):
+    print(f"Applying param state: {param_state}")
+    for name, value in param_state:
+        s.set(name, value)
+
+
+def stats_tuple(st):
+    def get(key):
+        return int(st.get_key_value(key)) if key in st.keys() else 0
+    return (get("conflicts"), get("decisions"), get("rlimit count"))
+
+
+# --------------------------
+# Protocol steps
+# --------------------------
+
+def run_prefix_step(S, K, clause_limit):
+    clauses = []
+
+    def on_clause(premises, deps, clause, status):
+        print(f"  [OnClause] collected clause status: {status}, clause: {clause}")
+        if len(clauses) < clause_limit:
+            clauses.append(clause)
+
+    OnClause(S, on_clause)
+    S.set("max_conflicts", K)
+    r = S.check()
+    return r, clauses
+
+# Replay proof prefix on an existing PPS_solver (no solver recreation)
+# Solver continues from its current state.
+def replay_prefix_on_pps(PPS_solver, clauses, param_state, budget):
+    print(f"[Replaying] on PPS with params={param_state} and budget={budget}")
+    apply_param_state(PPS_solver, param_state)
+
+    total_conflicts = total_decisions = total_rlimit = 0
+
+    # For each learned clause Cj = [l1, l2, ...], check ¬(l1 ∨ l2 ∨ ...)
+    for idx, Cj in enumerate(clauses):
+        lits = [l.translate(PPS_solver.ctx) for l in Cj]
+
+        negated_lits = []
+        for l in lits:
+            negated_lits.append(Not(l))
+
+        PPS_solver.set("max_conflicts", budget)
+        r = PPS_solver.check(negated_lits)
+        st = PPS_solver.statistics()
+
+        c, d, rl = stats_tuple(st)
+        total_conflicts += c
+        total_decisions += d
+        total_rlimit += rl
+
+        print(f"  [C{idx}] result={r}, conflicts={c}, decisions={d}, rlimit={rl}")
+
+    return (total_conflicts, total_decisions, total_rlimit)
+
+
+# For each PPS_i, replay the proof prefix of S
+def replay_proof_prefixes(clauses, param_states, PPS_solvers, K, eps=200):
+    budget = K + eps
+    base_param_state, candidate_param_states = param_states[0], param_states[1:]
+
+    # PPS_0 (baseline)
+    score0 = replay_prefix_on_pps(PPS_solvers[0], clauses, base_param_state, budget)
+    best_param_state, best_score = base_param_state, score0
+    
+    # PPS_i, i > 0
+    for i, p_state in enumerate(candidate_param_states, start=1):
+        score = replay_prefix_on_pps(PPS_solvers[i], clauses, p_state, budget)
+        if score < best_score:
+            best_param_state, best_score = p_state, score
+
+    return best_param_state, best_score
+
+# return a variant of the given param state
+def perturbate(param_state):
+    new_state = []
+    for name, val in param_state:
+        if isinstance(val, (int, float)) and "restart_factor" in name:
+            # perturb multiplicatively +/-10%
+            factor = random.choice([0.9, 1.1])
+            new_state.append((name, round(val * factor, 3)))
+        elif isinstance(val, int) and "phase_caching" in name:
+            # pick half or double
+            new_val = random.choice([max(1, val // 2), val * 2])
+            new_state.append((name, new_val))
+        elif name == "smt.relevancy":
+            # pick random alternative from {0,1,2}
+            new_val = random.choice([0, 1, 2])
+            new_state.append((name, new_val))
+        else:
+            # unchanged
+            new_state.append((name, val))
+    return new_state
+
+# --------------------------
+# Protocol iteration
+# --------------------------
+
+def protocol_iteration(filepath, manager, S, PPS_solvers, PPS_states, K, eps=200):
+    # --- Proof Prefix Solver (S) ---
+    P = manager.best_param_state or BASE_PARAM_CANDIDATES
+    apply_param_state(S, P)
+
+    # Run S with max conflicts K
+    # Simultaneously, collect subset of conflict clauses from the bounded run of S. 
+    # Right now clause collection is pretty naive as we just take the first clause_limit clauses from OnClause
+    print(f"[S] Running proof prefix solver with params={P} and max_conflicts={K}")
+    r, C_list = run_prefix_step(S, K, clause_limit=MAX_EXAMPLES)
+
+    # If S returns SAT or UNSAT we have a verdict
+    # Tell the central dispatch that search is complete and exit
+    if r == sat or r == unsat:
+        print(f"[S] {os.path.basename(filepath)} → {r} (within max_conflicts={K}). Search complete.")
+        manager.mark_complete()
+        return
+
+    # For each PPS_i, replay the proof prefix of S
+    print(f"[Replaying] Replaying proof prefix on PPS solvers with budget={K + eps}")
+    best_state, best_score = replay_proof_prefixes(C_list, PPS_states, PPS_solvers, K, eps)
+
+    if best_state != P:
+        print(f"[Dispatch] updating best param state")
+        manager.maybe_update_best(best_state, best_score)
+        P = best_state
+
+    # Update PPS_0 to use P (if it changed), and update all PPS_i > 0 with new perturbations of P
+    PPS_states[0] = P 
+    for i in range(1, len(PPS_states)):
+        PPS_states[i] = perturbate(P)
+        
+    return PPS_states
+
+
+# --------------------------
+# Prefix probing thread
+# --------------------------
+
+def prefix_probe_thread(filepath, manager):
+    # Proof prefix solver S
+    S = solver_from_file(filepath)
+    apply_param_state(S, BASE_PARAM_CANDIDATES)
+
+    PPS_solvers = []
+    PPS_states = []
+
+    # set up the 4 variant parameter probe solvers PPS_1 ... PPS_4 as new contexts on the proof prefix solver S
+    for i in range(4):
+        st = BASE_PARAM_CANDIDATES if i == 0 else perturbate(BASE_PARAM_CANDIDATES) # PPS_0 uses base params
+        ctx = Context()
+        PPS_solver = S.translate(ctx)  # clone S (proof prefix) into new context
+        apply_param_state(PPS_solver, st)
+        PPS_solvers.append(PPS_solver)
+        PPS_states.append(st)
+        print(f"[Init] PPS_{i} inherited prefix in new context with params={st}")
+
+    # Reuse the same solvers each iteration
+    iteration = 0
+    while not manager.search_complete:
+        print(f"\n[PrefixThread] Iteration {iteration}")
+        PPS_states = protocol_iteration(filepath, manager, S, PPS_solvers, PPS_states, K=MAX_CONFLICTS, eps=200)
+        iteration += 1
+
+
+# --------------------------
+# Main
+# --------------------------
+
+def run_main_solver(filepath):
+    set_param("parallel.enable", True)
+    main_solver = solver_from_file(filepath)
+    apply_param_state(main_solver, BASE_PARAM_CANDIDATES)
+    print(f"[Main] Started main solver on {os.path.basename(filepath)} with parallel.enable=True")
+    r = main_solver.check()
+    print(f"[Main] {os.path.basename(filepath)} → {r}")
+
+def main():
+    manager = BatchManager()
+    for benchmark in os.listdir(bench_dir):
+        if benchmark != "From_T2__hqr.t2_fixed__term_unfeasibility_1_0.smt2":
+            continue
+
+        filepath = os.path.join(bench_dir, benchmark)
+        prefix_proc = Process(target=prefix_probe_thread, args=(filepath, manager))
+        main_proc = Process(target=run_main_solver, args=(filepath,))
+        prefix_proc.start()
+        main_proc.start()
+        prefix_proc.join()
+        main_proc.join()
+
+    if manager.best_param_state:
+        print(f"\n[GLOBAL] Best parameter state: {manager.best_param_state} with score {manager.best_score}")
+
+if __name__ == "__main__":
+    main()
diff --git a/scripts/update_api.py b/scripts/update_api.py
index 5c28bcd3e..08eeaaf68 100755
--- a/scripts/update_api.py
+++ b/scripts/update_api.py
@@ -1941,7 +1941,7 @@ _error_handler_type  = ctypes.CFUNCTYPE(None, ctypes.c_void_p, ctypes.c_uint)
 _lib.Z3_set_error_handler.restype  = None
 _lib.Z3_set_error_handler.argtypes = [ContextObj, _error_handler_type]
 
-Z3_on_clause_eh = ctypes.CFUNCTYPE(None, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_uint, ctypes.POINTER(ctypes.c_uint), ctypes.c_void_p)
+Z3_on_clause_eh = ctypes.CFUNCTYPE(None, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_uint, ctypes.POINTER(ctypes.c_uint), ctypes.c_void_p, ctypes.c_uint)
 Z3_push_eh  = ctypes.CFUNCTYPE(None, ctypes.c_void_p, ctypes.c_void_p)
 Z3_pop_eh   = ctypes.CFUNCTYPE(None, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_uint)
 Z3_fresh_eh = ctypes.CFUNCTYPE(ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p)
diff --git a/src/api/api_datatype.cpp b/src/api/api_datatype.cpp
index 2509434f8..886165455 100644
--- a/src/api/api_datatype.cpp
+++ b/src/api/api_datatype.cpp
@@ -306,12 +306,24 @@ extern "C" {
         Z3_CATCH;
     }
 
-    static datatype_decl* mk_datatype_decl(Z3_context c,
-                                           Z3_symbol name,
-                                           unsigned num_constructors,
-                                           Z3_constructor constructors[]) {
+    static datatype_decl* api_datatype_decl(Z3_context c,
+                                            Z3_symbol name,
+                                            unsigned num_parameters,
+                                            Z3_sort const parameters[],
+                                            unsigned num_constructors,
+                                            Z3_constructor constructors[]) {
         datatype_util& dt_util = mk_c(c)->dtutil();
         ast_manager& m = mk_c(c)->m();
+        
+        sort_ref_vector params(m);
+        
+        // A correct use of the API is to always provide parameters explicitly.
+        // implicit parameters through polymorphic type variables does not work
+        // because the order of polymorphic variables in the parameters is ambiguous.
+        if (num_parameters > 0 && parameters) 
+            for (unsigned i = 0; i < num_parameters; ++i) 
+                params.push_back(to_sort(parameters[i]));
+        
         ptr_vector<constructor_decl> constrs;
         for (unsigned i = 0; i < num_constructors; ++i) {
             constructor* cn = reinterpret_cast<constructor*>(constructors[i]);
@@ -326,7 +338,7 @@ extern "C" {
             }
             constrs.push_back(mk_constructor_decl(cn->m_name, cn->m_tester, acc.size(), acc.data()));
         }
-        return mk_datatype_decl(dt_util, to_symbol(name), 0, nullptr, num_constructors, constrs.data());
+        return mk_datatype_decl(dt_util, to_symbol(name), params.size(), params.data(), num_constructors, constrs.data());
     }
 
     Z3_sort Z3_API Z3_mk_datatype(Z3_context c,
@@ -341,7 +353,7 @@ extern "C" {
 
         sort_ref_vector sorts(m);
         {
-            datatype_decl * data = mk_datatype_decl(c, name, num_constructors, constructors);
+            datatype_decl * data = api_datatype_decl(c, name, 0, nullptr, num_constructors, constructors);
             bool is_ok = mk_c(c)->get_dt_plugin()->mk_datatypes(1, &data, 0, nullptr, sorts);
             del_datatype_decl(data);
 
@@ -363,6 +375,42 @@ extern "C" {
         Z3_CATCH_RETURN(nullptr);
     }
 
+    Z3_sort Z3_API Z3_mk_polymorphic_datatype(Z3_context c,
+                                              Z3_symbol name,
+                                              unsigned num_parameters,
+                                              Z3_sort parameters[],
+                                              unsigned num_constructors,
+                                              Z3_constructor constructors[]) {
+        Z3_TRY;
+        LOG_Z3_mk_polymorphic_datatype(c, name, num_parameters, parameters, num_constructors, constructors);
+        RESET_ERROR_CODE();
+        ast_manager& m = mk_c(c)->m();
+        datatype_util data_util(m);
+
+        sort_ref_vector sorts(m);
+        {
+            datatype_decl * data = api_datatype_decl(c, name, num_parameters, parameters, num_constructors, constructors);
+            bool is_ok = mk_c(c)->get_dt_plugin()->mk_datatypes(1, &data, 0, nullptr, sorts);
+            del_datatype_decl(data);
+
+            if (!is_ok) {
+                SET_ERROR_CODE(Z3_INVALID_ARG, nullptr);
+                RETURN_Z3(nullptr);
+            }
+        }
+        sort * s = sorts.get(0);
+
+        mk_c(c)->save_ast_trail(s);
+        ptr_vector<func_decl> const& cnstrs = *data_util.get_datatype_constructors(s);
+
+        for (unsigned i = 0; i < num_constructors; ++i) {
+            constructor* cn = reinterpret_cast<constructor*>(constructors[i]);
+            cn->m_constructor = cnstrs[i];
+        }
+        RETURN_Z3_mk_polymorphic_datatype(of_sort(s));
+        Z3_CATCH_RETURN(nullptr);
+    }
+
     typedef ptr_vector<constructor> constructor_list;
 
     Z3_constructor_list Z3_API Z3_mk_constructor_list(Z3_context c,
@@ -387,14 +435,18 @@ extern "C" {
         Z3_CATCH;
     }
 
-    Z3_sort Z3_API Z3_mk_datatype_sort(Z3_context c, Z3_symbol name) {
+    Z3_sort Z3_API Z3_mk_datatype_sort(Z3_context c, Z3_symbol name, unsigned num_params, Z3_sort const params[]) {
         Z3_TRY;
-        LOG_Z3_mk_datatype_sort(c, name);
+        LOG_Z3_mk_datatype_sort(c, name, num_params, params);
         RESET_ERROR_CODE();
         ast_manager& m = mk_c(c)->m();
         datatype_util adt_util(m);
-        parameter p(to_symbol(name));
-        sort * s = m.mk_sort(adt_util.get_family_id(), DATATYPE_SORT, 1, &p);
+        vector<parameter> ps;
+        ps.push_back(parameter(to_symbol(name)));
+        for (unsigned i = 0; i < num_params; ++i) {
+            ps.push_back(parameter(to_sort(params[i])));
+        }
+        sort * s = m.mk_sort(adt_util.get_family_id(), DATATYPE_SORT, ps.size(), ps.data());
         mk_c(c)->save_ast_trail(s);
         RETURN_Z3(of_sort(s));
         Z3_CATCH_RETURN(nullptr);
@@ -416,7 +468,7 @@ extern "C" {
         ptr_vector<datatype_decl> datas;
         for (unsigned i = 0; i < num_sorts; ++i) {
             constructor_list* cl = reinterpret_cast<constructor_list*>(constructor_lists[i]);
-            datas.push_back(mk_datatype_decl(c, sort_names[i], cl->size(), reinterpret_cast<Z3_constructor*>(cl->data())));
+            datas.push_back(api_datatype_decl(c, sort_names[i], 0, nullptr, cl->size(), reinterpret_cast<Z3_constructor*>(cl->data())));
         }
         sort_ref_vector _sorts(m);
         bool ok = mk_c(c)->get_dt_plugin()->mk_datatypes(datas.size(), datas.data(), 0, nullptr, _sorts);
diff --git a/src/api/api_solver.cpp b/src/api/api_solver.cpp
index 05b93d38b..75b6b0588 100644
--- a/src/api/api_solver.cpp
+++ b/src/api/api_solver.cpp
@@ -1031,14 +1031,14 @@ extern "C" {
         Z3_TRY;
         RESET_ERROR_CODE();
         init_solver(c, s);     
-        user_propagator::on_clause_eh_t _on_clause = [=](void* user_ctx, expr* proof, unsigned nd, unsigned const* deps, unsigned n, expr* const* _literals) {
+        user_propagator::on_clause_eh_t _on_clause = [=](void* user_ctx, expr* proof, unsigned nd, unsigned const* deps, unsigned n, expr* const* _literals, unsigned const status) {
             Z3_ast_vector_ref * literals = alloc(Z3_ast_vector_ref, *mk_c(c), mk_c(c)->m());
             mk_c(c)->save_object(literals);
             expr_ref pr(proof, mk_c(c)->m());
             scoped_ast_vector _sc(literals);
             for (unsigned i = 0; i < n; ++i)
                 literals->m_ast_vector.push_back(_literals[i]);
-            on_clause_eh(user_ctx, of_expr(pr.get()), nd, deps, of_ast_vector(literals));
+            on_clause_eh(user_ctx, of_expr(pr.get()), nd, deps, of_ast_vector(literals), status);
         };
         to_solver_ref(s)->register_on_clause(user_context, _on_clause);
         auto& solver = *to_solver(s);
diff --git a/src/api/c++/z3++.h b/src/api/c++/z3++.h
index 9fb84236d..9332d9074 100644
--- a/src/api/c++/z3++.h
+++ b/src/api/c++/z3++.h
@@ -343,6 +343,14 @@ namespace z3 {
         */
         sort datatype_sort(symbol const& name);
 
+        /**
+           \brief a reference to a recursively defined parametric datatype.
+           Expect that it gets defined as a \ref datatype.
+           \param name name of the datatype
+           \param params sort parameters
+        */
+        sort datatype_sort(symbol const& name, sort_vector const& params);
+
             
         /**
            \brief create an uninterpreted sort with the name given by the string or symbol.
@@ -3625,7 +3633,14 @@ namespace z3 {
 
 
     inline sort context::datatype_sort(symbol const& name) {
-        Z3_sort s = Z3_mk_datatype_sort(*this, name);
+        Z3_sort s = Z3_mk_datatype_sort(*this, name, 0, nullptr);
+        check_error();
+        return sort(*this, s);            
+    }
+
+    inline sort context::datatype_sort(symbol const& name, sort_vector const& params) {
+        array<Z3_sort> _params(params);
+        Z3_sort s = Z3_mk_datatype_sort(*this, name, _params.size(), _params.ptr());
         check_error();
         return sort(*this, s);            
     }
@@ -4273,20 +4288,20 @@ namespace z3 {
         return expr(ctx(), r);
     }
 
-    typedef std::function<void(expr const& proof, std::vector<unsigned> const& deps, expr_vector const& clause)> on_clause_eh_t;
+    typedef std::function<void(expr const& proof, std::vector<unsigned> const& deps, expr_vector const& clause, unsigned const status)> on_clause_eh_t;
 
     class on_clause {
         context& c;
         on_clause_eh_t m_on_clause;
 
-        static void _on_clause_eh(void* _ctx, Z3_ast _proof, unsigned n, unsigned const* dep, Z3_ast_vector _literals) {
+        static void _on_clause_eh(void* _ctx, Z3_ast _proof, unsigned n, unsigned const* dep, Z3_ast_vector _literals, unsigned const status) {
             on_clause* ctx = static_cast<on_clause*>(_ctx);
             expr_vector lits(ctx->c, _literals);
             expr proof(ctx->c, _proof);
             std::vector<unsigned> deps;
             for (unsigned i = 0; i < n; ++i)
                 deps.push_back(dep[i]);
-            ctx->m_on_clause(proof, deps, lits);
+            ctx->m_on_clause(proof, deps, lits, status);
         }
     public:
         on_clause(solver& s, on_clause_eh_t& on_clause_eh): c(s.ctx()) {
diff --git a/src/api/dotnet/Context.cs b/src/api/dotnet/Context.cs
index 9293b1a31..49f183428 100644
--- a/src/api/dotnet/Context.cs
+++ b/src/api/dotnet/Context.cs
@@ -474,6 +474,36 @@ namespace Microsoft.Z3
             return new DatatypeSort(this, symbol, constructors);
         }
 
+        /// <summary>
+        /// Create a forward reference to a datatype sort.
+        /// This is useful for creating recursive datatypes or parametric datatypes.
+        /// </summary>
+        /// <param name="name">name of the datatype sort</param>
+        /// <param name="parameters">optional array of sort parameters for parametric datatypes</param>
+        public DatatypeSort MkDatatypeSortRef(Symbol name, Sort[] parameters = null)
+        {
+            Debug.Assert(name != null);
+            CheckContextMatch(name);
+            if (parameters != null)
+                CheckContextMatch<Sort>(parameters);
+            
+            var numParams = (parameters == null) ? 0 : (uint)parameters.Length;
+            var paramsNative = (parameters == null) ? null : AST.ArrayToNative(parameters);
+            return new DatatypeSort(this, Native.Z3_mk_datatype_sort(nCtx, name.NativeObject, numParams, paramsNative));
+        }
+
+        /// <summary>
+        /// Create a forward reference to a datatype sort.
+        /// This is useful for creating recursive datatypes or parametric datatypes.
+        /// </summary>
+        /// <param name="name">name of the datatype sort</param>
+        /// <param name="parameters">optional array of sort parameters for parametric datatypes</param>
+        public DatatypeSort MkDatatypeSortRef(string name, Sort[] parameters = null)
+        {
+            using var symbol = MkSymbol(name);
+            return MkDatatypeSortRef(symbol, parameters);
+        }
+
         /// <summary>
         /// Create mutually recursive datatypes.
         /// </summary>
diff --git a/src/api/java/Context.java b/src/api/java/Context.java
index 2350b52ae..691ecd737 100644
--- a/src/api/java/Context.java
+++ b/src/api/java/Context.java
@@ -388,6 +388,54 @@ public class Context implements AutoCloseable {
         return new DatatypeSort<>(this, mkSymbol(name), constructors);
     }
 
+    /**
+     * Create a forward reference to a datatype sort.
+     * This is useful for creating recursive datatypes or parametric datatypes.
+     * @param name name of the datatype sort
+     * @param params optional array of sort parameters for parametric datatypes
+     **/
+    public <R> DatatypeSort<R> mkDatatypeSortRef(Symbol name, Sort[] params)
+    {
+        checkContextMatch(name);
+        if (params != null)
+            checkContextMatch(params);
+        
+        int numParams = (params == null) ? 0 : params.length;
+        long[] paramsNative = (params == null) ? new long[0] : AST.arrayToNative(params);
+        return new DatatypeSort<>(this, Native.mkDatatypeSort(nCtx(), name.getNativeObject(), numParams, paramsNative));
+    }
+
+    /**
+     * Create a forward reference to a datatype sort (non-parametric).
+     * This is useful for creating recursive datatypes.
+     * @param name name of the datatype sort
+     **/
+    public <R> DatatypeSort<R> mkDatatypeSortRef(Symbol name)
+    {
+        return mkDatatypeSortRef(name, null);
+    }
+
+    /**
+     * Create a forward reference to a datatype sort.
+     * This is useful for creating recursive datatypes or parametric datatypes.
+     * @param name name of the datatype sort
+     * @param params optional array of sort parameters for parametric datatypes
+     **/
+    public <R> DatatypeSort<R> mkDatatypeSortRef(String name, Sort[] params)
+    {
+        return mkDatatypeSortRef(mkSymbol(name), params);
+    }
+
+    /**
+     * Create a forward reference to a datatype sort (non-parametric).
+     * This is useful for creating recursive datatypes.
+     * @param name name of the datatype sort
+     **/
+    public <R> DatatypeSort<R> mkDatatypeSortRef(String name)
+    {
+        return mkDatatypeSortRef(name, null);
+    }
+
     /**
      * Create mutually recursive datatypes. 
      * @param names names of datatype sorts 
diff --git a/src/api/ml/z3.ml b/src/api/ml/z3.ml
index 4d5238957..cc7294aba 100644
--- a/src/api/ml/z3.ml
+++ b/src/api/ml/z3.ml
@@ -909,11 +909,17 @@ struct
     mk_sort ctx (Symbol.mk_string ctx name) constructors
 
   let mk_sort_ref (ctx: context) (name:Symbol.symbol) =
-    Z3native.mk_datatype_sort ctx name
+    Z3native.mk_datatype_sort ctx name 0 []
 
   let mk_sort_ref_s (ctx: context) (name: string) =
     mk_sort_ref ctx (Symbol.mk_string ctx name)
 
+  let mk_sort_ref_p (ctx: context) (name:Symbol.symbol) (params:Sort.sort list) =
+    Z3native.mk_datatype_sort ctx name (List.length params) params
+
+  let mk_sort_ref_ps (ctx: context) (name: string) (params:Sort.sort list) =
+    mk_sort_ref_p ctx (Symbol.mk_string ctx name) params
+
   let mk_sorts (ctx:context) (names:Symbol.symbol list) (c:Constructor.constructor list list) =
     let n = List.length names in
     let f e = ConstructorList.create ctx e in
diff --git a/src/api/ml/z3.mli b/src/api/ml/z3.mli
index 7afc01918..6764b0e2d 100644
--- a/src/api/ml/z3.mli
+++ b/src/api/ml/z3.mli
@@ -1087,6 +1087,12 @@ sig
   (* [mk_sort_ref_s ctx s] is [mk_sort_ref ctx (Symbol.mk_string ctx s)] *)
   val mk_sort_ref_s : context -> string -> Sort.sort
 
+  (** Create a forward reference to a parametric datatype sort. *)
+  val mk_sort_ref_p : context -> Symbol.symbol -> Sort.sort list -> Sort.sort
+
+  (** Create a forward reference to a parametric datatype sort. *)
+  val mk_sort_ref_ps : context -> string -> Sort.sort list -> Sort.sort
+
   (** Create a new datatype sort. *)
   val mk_sort : context -> Symbol.symbol -> Constructor.constructor list -> Sort.sort
 
diff --git a/src/api/python/z3/z3.py b/src/api/python/z3/z3.py
index 051265a78..5a6ce8ab9 100644
--- a/src/api/python/z3/z3.py
+++ b/src/api/python/z3/z3.py
@@ -1245,6 +1245,18 @@ def _coerce_expr_merge(s, a):
     else:
         return s
 
+def _check_same_sort(a, b, ctx=None):
+    if not isinstance(a, ExprRef):
+        return False
+    if not isinstance(b, ExprRef):
+        return False
+    if ctx is None:
+        ctx = a.ctx
+
+    a_sort = Z3_get_sort(ctx.ctx, a.ast)
+    b_sort = Z3_get_sort(ctx.ctx, b.ast)
+    return Z3_is_eq_sort(ctx.ctx, a_sort, b_sort)
+
 
 def _coerce_exprs(a, b, ctx=None):
     if not is_expr(a) and not is_expr(b):
@@ -1259,6 +1271,9 @@ def _coerce_exprs(a, b, ctx=None):
     if isinstance(b, float) and isinstance(a, ArithRef):
         b = RealVal(b, a.ctx)
 
+    if _check_same_sort(a, b, ctx):
+        return (a, b)
+
     s = None
     s = _coerce_expr_merge(s, a)
     s = _coerce_expr_merge(s, b)
@@ -5474,10 +5489,30 @@ class DatatypeRef(ExprRef):
         """Return the datatype sort of the datatype expression `self`."""
         return DatatypeSortRef(Z3_get_sort(self.ctx_ref(), self.as_ast()), self.ctx)
 
-def DatatypeSort(name, ctx = None):
-    """Create a reference to a sort that was declared, or will be declared, as a recursive datatype"""
+def DatatypeSort(name, params=None, ctx=None):
+    """Create a reference to a sort that was declared, or will be declared, as a recursive datatype.
+    
+    Args:
+        name: name of the datatype sort
+        params: optional list/tuple of sort parameters for parametric datatypes
+        ctx: Z3 context (optional)
+    
+    Example:
+        >>> # Non-parametric datatype
+        >>> TreeRef = DatatypeSort('Tree')
+        >>> # Parametric datatype with one parameter
+        >>> ListIntRef = DatatypeSort('List', [IntSort()])
+        >>> # Parametric datatype with multiple parameters
+        >>> PairRef = DatatypeSort('Pair', [IntSort(), BoolSort()])
+    """
     ctx = _get_ctx(ctx)
-    return DatatypeSortRef(Z3_mk_datatype_sort(ctx.ref(), to_symbol(name, ctx)), ctx)
+    if params is None or len(params) == 0:
+        return DatatypeSortRef(Z3_mk_datatype_sort(ctx.ref(), to_symbol(name, ctx), 0, (Sort * 0)()), ctx)
+    else:
+        _params = (Sort * len(params))()
+        for i in range(len(params)):
+            _params[i] = params[i].ast
+        return DatatypeSortRef(Z3_mk_datatype_sort(ctx.ref(), to_symbol(name, ctx), len(params), _params), ctx)
 
 def TupleSort(name, sorts, ctx=None):
     """Create a named tuple sort base on a set of underlying sorts
@@ -11677,12 +11712,12 @@ def to_AstVectorObj(ptr,):
 # for UserPropagator we use a global dictionary, which isn't great code.
 
 _my_hacky_class = None
-def on_clause_eh(ctx, p, n, dep, clause):
+def on_clause_eh(ctx, p, n, dep, clause, status):
     onc = _my_hacky_class
     p = _to_expr_ref(to_Ast(p), onc.ctx)
     clause = AstVector(to_AstVectorObj(clause), onc.ctx)
     deps = [dep[i] for i in range(n)]
-    onc.on_clause(p, deps, clause)
+    onc.on_clause(p, deps, clause, status)
     
 _on_clause_eh = Z3_on_clause_eh(on_clause_eh)
 
diff --git a/src/api/z3_api.h b/src/api/z3_api.h
index 9de58e057..3264226f3 100644
--- a/src/api/z3_api.h
+++ b/src/api/z3_api.h
@@ -1441,7 +1441,7 @@ Z3_DECLARE_CLOSURE(Z3_final_eh,   void, (void* ctx, Z3_solver_callback cb));
 Z3_DECLARE_CLOSURE(Z3_created_eh, void, (void* ctx, Z3_solver_callback cb, Z3_ast t));
 Z3_DECLARE_CLOSURE(Z3_decide_eh,  void, (void* ctx, Z3_solver_callback cb, Z3_ast t, unsigned idx, bool phase));
 Z3_DECLARE_CLOSURE(Z3_on_binding_eh, bool, (void* ctx, Z3_solver_callback cb, Z3_ast q, Z3_ast inst));
-Z3_DECLARE_CLOSURE(Z3_on_clause_eh, void, (void* ctx, Z3_ast proof_hint, unsigned n, unsigned const* deps, Z3_ast_vector literals));
+Z3_DECLARE_CLOSURE(Z3_on_clause_eh, void, (void* ctx, Z3_ast proof_hint, unsigned n, unsigned const* deps, Z3_ast_vector literals, unsigned const status));
 
 
 /**
@@ -2127,6 +2127,33 @@ extern "C" {
                                   unsigned num_constructors,
                                   Z3_constructor constructors[]);
 
+    /**
+       \brief Create a parametric datatype with explicit type parameters.
+       
+       This function is similar to #Z3_mk_datatype, except it takes an explicit set of type parameters.
+       The parameters can be type variables created with #Z3_mk_type_variable, allowing the definition
+       of polymorphic datatypes that can be instantiated with different concrete types.
+
+       \param c logical context
+       \param name name of the datatype
+       \param num_parameters number of type parameters (can be 0)
+       \param parameters array of type parameters (type variables or concrete sorts)
+       \param num_constructors number of constructors
+       \param constructors array of constructor specifications
+
+       \sa Z3_mk_datatype
+       \sa Z3_mk_type_variable
+       \sa Z3_mk_datatype_sort
+
+       def_API('Z3_mk_polymorphic_datatype', SORT, (_in(CONTEXT), _in(SYMBOL), _in(UINT), _in_array(2, SORT), _in(UINT), _inout_array(4, CONSTRUCTOR)))
+     */
+    Z3_sort Z3_API Z3_mk_polymorphic_datatype(Z3_context c,
+                                              Z3_symbol name,
+                                              unsigned num_parameters,
+                                              Z3_sort parameters[],
+                                              unsigned num_constructors,
+                                              Z3_constructor constructors[]);
+
     /**
        \brief create a forward reference to a recursive datatype being declared.
        The forward reference can be used in a nested occurrence: the range of an array
@@ -2136,9 +2163,14 @@ extern "C" {
        Forward references can replace the use sort references, that are unsigned integers
        in the \c Z3_mk_constructor call
 
-       def_API('Z3_mk_datatype_sort', SORT, (_in(CONTEXT), _in(SYMBOL)))
+       \param c logical context
+       \param name name of the datatype
+       \param num_params number of sort parameters  
+       \param params array of sort parameters
+
+       def_API('Z3_mk_datatype_sort', SORT, (_in(CONTEXT), _in(SYMBOL), _in(UINT), _in_array(2, SORT)))
      */
-    Z3_sort Z3_API Z3_mk_datatype_sort(Z3_context c, Z3_symbol name);
+    Z3_sort Z3_API Z3_mk_datatype_sort(Z3_context c, Z3_symbol name, unsigned num_params, Z3_sort const params[]);
 
     /**
        \brief Create list of constructors.
diff --git a/src/ast/datatype_decl_plugin.cpp b/src/ast/datatype_decl_plugin.cpp
index f91afc9ac..5bb918c5f 100644
--- a/src/ast/datatype_decl_plugin.cpp
+++ b/src/ast/datatype_decl_plugin.cpp
@@ -300,6 +300,12 @@ namespace datatype {
                         TRACE(datatype, tout << "expected sort parameter at position " << i << " got: " << s << "\n";);
                         throw invalid_datatype();
                     }
+                    // Allow type variables as parameters for polymorphic datatypes
+                    sort* param_sort = to_sort(s.get_ast());
+                    if (!m_manager->is_type_var(param_sort) && param_sort->get_family_id() == null_family_id) {
+                        // Type variables and concrete sorts are allowed, but not other uninterpreted sorts
+                        // Actually, all sorts should be allowed including uninterpreted ones
+                    }
                 }
                                 
                 sort* s = m_manager->mk_sort(name.get_symbol(),
diff --git a/src/ast/normal_forms/nnf.cpp b/src/ast/normal_forms/nnf.cpp
index 4de3d7ba7..746d48fa2 100644
--- a/src/ast/normal_forms/nnf.cpp
+++ b/src/ast/normal_forms/nnf.cpp
@@ -566,7 +566,8 @@ struct nnf::imp {
         expr * _then      = rs[2];
         expr * _else      = rs[3];
 
-        app * r = m.mk_and(m.mk_or(_not_cond, _then), m.mk_or(_cond, _else));
+        expr* a = m.mk_or(_not_cond, _then);
+        app * r = m.mk_and(a, m.mk_or(_cond, _else));
         m_result_stack.shrink(fr.m_spos);
         m_result_stack.push_back(r);
         if (proofs_enabled()) {
@@ -612,11 +613,13 @@ struct nnf::imp {
 
         app * r;
         if (is_eq(t) == fr.m_pol) {
-            auto a = m.mk_or(not_lhs, rhs);
+            expr* a = m.mk_or(not_lhs, rhs);
             r = m.mk_and(a, m.mk_or(lhs, not_rhs));
         }
-        else
-            r = m.mk_and(m.mk_or(lhs, rhs), m.mk_or(not_lhs, not_rhs));
+        else {
+            expr* a = m.mk_or(lhs, rhs);
+            r = m.mk_and(a, m.mk_or(not_lhs, not_rhs));
+        }
         m_result_stack.shrink(fr.m_spos);
         m_result_stack.push_back(r);
         if (proofs_enabled()) {
@@ -688,8 +691,8 @@ struct nnf::imp {
             if (proofs_enabled()) {
                 expr_ref aux(m);
                 aux = m.mk_label(true, names.size(), names.data(), arg);
-                pr = m.mk_transitivity(mk_proof(fr.m_pol, 1, &arg_pr, t, to_app(aux)),
-                                         m.mk_iff_oeq(m.mk_rewrite(aux, r)));
+                auto a = mk_proof(fr.m_pol, 1, &arg_pr, t, to_app(aux));
+                pr = m.mk_transitivity(a, m.mk_iff_oeq(m.mk_rewrite(aux, r)));
             }
         }
         else {
diff --git a/src/ast/rewriter/arith_rewriter.cpp b/src/ast/rewriter/arith_rewriter.cpp
index 8851bc7fd..d5ad70a1f 100644
--- a/src/ast/rewriter/arith_rewriter.cpp
+++ b/src/ast/rewriter/arith_rewriter.cpp
@@ -720,24 +720,36 @@ br_status arith_rewriter::mk_le_ge_eq_core(expr * arg1, expr * arg2, op_kind kin
     }
     expr* c = nullptr, *t = nullptr, *e = nullptr;
     if (m.is_ite(arg1, c, t, e) && is_numeral(t, a1) && is_numeral(arg2, a2)) {
+        expr_ref a(m.mk_not(c), m);
         switch (kind) {
-        case LE: result = a1 <= a2 ? m.mk_or(c, m_util.mk_le(e, arg2)) : m.mk_and(m.mk_not(c), m_util.mk_le(e, arg2)); return BR_REWRITE2;
-        case GE: result = a1 >= a2 ? m.mk_or(c, m_util.mk_ge(e, arg2)) : m.mk_and(m.mk_not(c), m_util.mk_ge(e, arg2)); return BR_REWRITE2;
-        case EQ: result = a1 == a2 ? m.mk_or(c, m.mk_eq(e, arg2))    : m.mk_and(m.mk_not(c), m_util.mk_eq(e, arg2)); return BR_REWRITE2;
+        case LE: result = a1 <= a2 ? m.mk_or(c, m_util.mk_le(e, arg2)) : m.mk_and(a, m_util.mk_le(e, arg2)); return BR_REWRITE2;
+        case GE: result = a1 >= a2 ? m.mk_or(c, m_util.mk_ge(e, arg2)) : m.mk_and(a, m_util.mk_ge(e, arg2)); return BR_REWRITE2;
+        case EQ: result = a1 == a2 ? m.mk_or(c, m.mk_eq(e, arg2))    : m.mk_and(a, m_util.mk_eq(e, arg2)); return BR_REWRITE2;
         }
     }
     if (m.is_ite(arg1, c, t, e) && is_numeral(e, a1) && is_numeral(arg2, a2)) {
+        expr_ref a(m.mk_not(c), m);
         switch (kind) {
-        case LE: result = a1 <= a2 ? m.mk_or(m.mk_not(c), m_util.mk_le(t, arg2)) : m.mk_and(c, m_util.mk_le(t, arg2)); return BR_REWRITE2;
-        case GE: result = a1 >= a2 ? m.mk_or(m.mk_not(c), m_util.mk_ge(t, arg2)) : m.mk_and(c, m_util.mk_ge(t, arg2)); return BR_REWRITE2;
-        case EQ: result = a1 == a2 ? m.mk_or(m.mk_not(c), m.mk_eq(t, arg2))    : m.mk_and(c, m_util.mk_eq(t, arg2)); return BR_REWRITE2;
+        case LE: result = a1 <= a2 ? m.mk_or(a, m_util.mk_le(t, arg2)) : m.mk_and(c, m_util.mk_le(t, arg2)); return BR_REWRITE2;
+        case GE: result = a1 >= a2 ? m.mk_or(a, m_util.mk_ge(t, arg2)) : m.mk_and(c, m_util.mk_ge(t, arg2)); return BR_REWRITE2;
+        case EQ: result = a1 == a2 ? m.mk_or(a, m.mk_eq(t, arg2))    : m.mk_and(c, m_util.mk_eq(t, arg2)); return BR_REWRITE2;
         }
     }
     if (m.is_ite(arg1, c, t, e) && arg1->get_ref_count() == 1) {
         switch (kind) {
-        case LE: result = m.mk_ite(c, m_util.mk_le(t, arg2), m_util.mk_le(e, arg2)); return BR_REWRITE2;
-        case GE: result = m.mk_ite(c, m_util.mk_ge(t, arg2), m_util.mk_ge(e, arg2)); return BR_REWRITE2;
-        case EQ: result = m.mk_ite(c, m.mk_eq(t, arg2), m.mk_eq(e, arg2)); return BR_REWRITE2;
+        case LE:
+        {
+            auto a = m_util.mk_le(t, arg2);
+            result = m.mk_ite(c, a, m_util.mk_le(e, arg2)); return BR_REWRITE2;
+        }
+        case GE: {
+            auto a = m_util.mk_ge(t, arg2);
+            result = m.mk_ite(c, a, m_util.mk_ge(e, arg2)); return BR_REWRITE2;
+        }
+        case EQ:{
+            auto a = m.mk_eq(t, arg2);
+            result = m.mk_ite(c, a, m.mk_eq(e, arg2)); return BR_REWRITE2;
+        }
         }
     }
     if (m_util.is_to_int(arg2) && is_numeral(arg1)) {        
diff --git a/src/ast/rewriter/seq_rewriter.cpp b/src/ast/rewriter/seq_rewriter.cpp
index c5ef8d9ed..d708af9e0 100644
--- a/src/ast/rewriter/seq_rewriter.cpp
+++ b/src/ast/rewriter/seq_rewriter.cpp
@@ -55,7 +55,8 @@ expr_ref sym_expr::accept(expr* e) {
             result = m.mk_bool_val((r1 <= r2) && (r2 <= r3));            
         }
         else {
-            result = m.mk_and(u.mk_le(m_t, e), u.mk_le(e, m_s));
+            auto a = u.mk_le(m_t, e);
+            result = m.mk_and(a, u.mk_le(e, m_s));
         }
         break;
     }
@@ -190,7 +191,9 @@ br_status seq_rewriter::mk_eq_helper(expr* a, expr* b, expr_ref& result) {
     // sa in (ra n rb) u (C(ra) n C(rb))
     if (is_not)
         rb = re().mk_complement(rb);
-    expr* r = re().mk_union(re().mk_inter(ra, rb), re().mk_inter(re().mk_complement(ra), re().mk_complement(rb)));
+    auto a_ = re().mk_inter(ra, rb);
+    auto b_ = re().mk_complement(ra);
+    expr* r = re().mk_union(a_, re().mk_inter(b_, re().mk_complement(rb)));
     result = re().mk_in_re(sa, r);
     return BR_REWRITE_FULL;
 }
@@ -620,10 +623,14 @@ expr_ref seq_rewriter::mk_seq_rest(expr* t) {
     expr_ref result(m());
     expr* s, * j, * k;
     rational jv;
-    if (str().is_extract(t, s, j, k) &&  m_autil.is_numeral(j, jv) && jv >= 0) 
-        result = str().mk_substr(s, m_autil.mk_int(jv + 1), mk_sub(k, 1));
-    else 
-        result = str().mk_substr(t, one(), mk_sub(str().mk_length(t), 1));
+    if (str().is_extract(t, s, j, k) &&  m_autil.is_numeral(j, jv) && jv >= 0) {
+        auto a = m_autil.mk_int(jv + 1);
+        result = str().mk_substr(s, a, mk_sub(k, 1));
+    }
+    else {
+        auto a = one();
+        result = str().mk_substr(t, a, mk_sub(str().mk_length(t), 1));
+    }
     return result;
 }
 
@@ -654,7 +661,10 @@ expr_ref seq_rewriter::mk_seq_last(expr* t) {
 *  No: if k > |s| then substring(s,0,k) = substring(s,0,k-1)
 */
 expr_ref seq_rewriter::mk_seq_butlast(expr* t) {
-    return expr_ref(str().mk_substr(t, zero(), m_autil.mk_sub(str().mk_length(t), one())), m());
+    auto b = zero();
+    auto c = str().mk_length(t);
+    auto a = str().mk_substr(t, b, m_autil.mk_sub(c, one()));
+    return expr_ref(a, m());
 }
 
 /*
@@ -1374,9 +1384,16 @@ br_status seq_rewriter::mk_seq_nth(expr* a, expr* b, expr_ref& result) {
     }    
 
     expr* la = str().mk_length(a);
-    result = m().mk_ite(m().mk_and(m_autil.mk_ge(b, zero()), m().mk_not(m_autil.mk_le(la, b))), 
-                        str().mk_nth_i(a, b),
-                        str().mk_nth_u(a, b));
+    {
+        // deterministic evaluation order for guard components
+        auto ge0 = m_autil.mk_ge(b, zero());
+        auto le_la = m_autil.mk_le(la, b);
+        auto not_le = m().mk_not(le_la);
+        auto guard = m().mk_and(ge0, not_le);
+        auto t1 = str().mk_nth_i(a, b);
+        auto e1 = str().mk_nth_u(a, b);
+        result = m().mk_ite(guard, t1, e1);
+    }
     return BR_REWRITE_FULL;
 }
 
@@ -1547,17 +1564,20 @@ br_status seq_rewriter::mk_seq_index(expr* a, expr* b, expr* c, expr_ref& result
     }
 
     if (str().is_empty(b)) {
-        result = m().mk_ite(m().mk_and(m_autil.mk_le(zero(), c),
-                                       m_autil.mk_le(c, str().mk_length(a))),
-                            c,
-                            minus_one());
+        // enforce deterministic evaluation order for bounds checks
+        auto a1 = m_autil.mk_le(zero(), c);
+        auto b1 = m_autil.mk_le(c, str().mk_length(a));
+        auto cond = m().mk_and(a1, b1);
+        result = m().mk_ite(cond, c, minus_one());
         return BR_REWRITE2;
     }
 
     
     if (str().is_empty(a)) {
         expr* emp = str().mk_is_empty(b);
-        result = m().mk_ite(m().mk_and(m().mk_eq(c, zero()), emp), zero(), minus_one());
+        auto a1 = m().mk_eq(c, zero());
+        auto cond = m().mk_and(a1, emp);
+        result = m().mk_ite(cond, zero(), minus_one());
         return BR_REWRITE2;
     }
 
@@ -1870,7 +1890,10 @@ br_status seq_rewriter::mk_seq_map(expr* f, expr* seqA, expr_ref& result) {
         return BR_REWRITE2;
     }
     if (str().is_concat(seqA, s1, s2)) {
-        result = str().mk_concat(str().mk_map(f, s1), str().mk_map(f, s2));
+        // introduce temporaries to ensure deterministic evaluation order of recursive map calls
+        auto m1 = str().mk_map(f, s1);
+        auto m2 = str().mk_map(f, s2);
+        result = str().mk_concat(m1, m2);
         return BR_REWRITE2;
     }
     return BR_FAILED;
@@ -1890,7 +1913,9 @@ br_status seq_rewriter::mk_seq_mapi(expr* f, expr* i, expr* seqA, expr_ref& resu
     }
     if (str().is_concat(seqA, s1, s2)) {
         expr_ref j(m_autil.mk_add(i, str().mk_length(s1)), m());
-        result = str().mk_concat(str().mk_mapi(f, i, s1), str().mk_mapi(f, j, s2));
+        auto left  = str().mk_mapi(f, i, s1);
+        auto right = str().mk_mapi(f, j, s2);
+        result = str().mk_concat(left, right);
         return BR_REWRITE2;
     }
     return BR_FAILED;
@@ -2046,8 +2071,8 @@ br_status seq_rewriter::mk_seq_prefix(expr* a, expr* b, expr_ref& result) {
                 SASSERT(bs.size() > 1);
                 s1 = s1.extract(s2.length(), s1.length() - s2.length());
                 as[0] = str().mk_string(s1);
-                result = str().mk_prefix(str().mk_concat(as.size(), as.data(), sort_a),
-                                              str().mk_concat(bs.size()-1, bs.data()+1, sort_a));
+                auto a = str().mk_concat(as.size(), as.data(), sort_a);
+                result = str().mk_prefix(a, str().mk_concat(bs.size()-1, bs.data()+1, sort_a));
                 TRACE(seq, tout << s1 << " " << s2 << " " << result << "\n";);
                 return BR_REWRITE_FULL;                
             }
@@ -2384,7 +2409,8 @@ br_status seq_rewriter::mk_str_stoi(expr* a, expr_ref& result) {
     }
     expr* b;
     if (str().is_itos(a, b)) {
-        result = m().mk_ite(m_autil.mk_ge(b, zero()), b, minus_one());
+        auto a = m_autil.mk_ge(b, zero());
+        result = m().mk_ite(a, b, minus_one());
         return BR_DONE;
     }
     if (str().is_ubv2s(a, b)) {
@@ -2395,7 +2421,8 @@ br_status seq_rewriter::mk_str_stoi(expr* a, expr_ref& result) {
     
     expr* c = nullptr, *t = nullptr, *e = nullptr;
     if (m().is_ite(a, c, t, e)) {
-        result = m().mk_ite(c, str().mk_stoi(t), str().mk_stoi(e));
+        auto a = str().mk_stoi(t);
+        result = m().mk_ite(c, a, str().mk_stoi(e));
         return BR_REWRITE_FULL;
     }
 
@@ -2703,7 +2730,10 @@ br_status seq_rewriter::mk_re_reverse(expr* r, expr_ref& result) {
     zstring zs;
     unsigned lo = 0, hi = 0;
     if (re().is_concat(r, r1, r2)) {
-        result = re().mk_concat(re().mk_reverse(r2), re().mk_reverse(r1));
+        // deterministic evaluation order for reverse operands
+        auto a_rev = re().mk_reverse(r2);
+        auto b_rev = re().mk_reverse(r1);
+        result = re().mk_concat(a_rev, b_rev);
         return BR_REWRITE2;
     }
     else if (re().is_star(r, r1)) {
@@ -2715,15 +2745,22 @@ br_status seq_rewriter::mk_re_reverse(expr* r, expr_ref& result) {
         return BR_REWRITE2;
     }
     else if (re().is_union(r, r1, r2)) {
-        result = re().mk_union(re().mk_reverse(r1), re().mk_reverse(r2));
+        // ensure deterministic evaluation order of parameters
+        auto a = re().mk_reverse(r1);
+        auto b = re().mk_reverse(r2);
+        result = re().mk_union(a, b);
         return BR_REWRITE2;
     }
     else if (re().is_intersection(r, r1, r2)) {
-        result = re().mk_inter(re().mk_reverse(r1), re().mk_reverse(r2));
+        auto a = re().mk_reverse(r1);
+        auto b = re().mk_reverse(r2);
+        result = re().mk_inter(a, b);
         return BR_REWRITE2;
     }
     else if (re().is_diff(r, r1, r2)) {
-        result = re().mk_diff(re().mk_reverse(r1), re().mk_reverse(r2));
+        auto a = re().mk_reverse(r1);
+        auto b = re().mk_reverse(r2);
+        result = re().mk_diff(a, b);
         return BR_REWRITE2;
     }
     else if (m().is_ite(r, p, r1, r2)) {
@@ -2767,8 +2804,9 @@ br_status seq_rewriter::mk_re_reverse(expr* r, expr_ref& result) {
         return BR_DONE;
     }
     else if (re().is_to_re(r, s) && str().is_concat(s, s1, s2)) {
-        result = re().mk_concat(re().mk_reverse(re().mk_to_re(s2)), 
-                                re().mk_reverse(re().mk_to_re(s1)));
+        auto a_rev = re().mk_reverse(re().mk_to_re(s2));
+        auto b_rev = re().mk_reverse(re().mk_to_re(s1));
+        result = re().mk_concat(a_rev, b_rev);
         return BR_REWRITE3;
     }
     else {
@@ -2957,7 +2995,11 @@ void seq_rewriter::mk_antimirov_deriv_rec(expr* e, expr* r, expr* path, expr_ref
         }
         else {
             // observe that the precondition |r1|>0 is is implied by c1 for use of mk_seq_first
-            m_br.mk_and(m().mk_not(m().mk_eq(r1, str().mk_empty(seq_sort))), m().mk_eq(mk_seq_first(r1), e), c1);
+            {
+                auto is_non_empty = m().mk_not(m().mk_eq(r1, str().mk_empty(seq_sort)));
+                auto eq_first = m().mk_eq(mk_seq_first(r1), e);
+                m_br.mk_and(is_non_empty, eq_first, c1);
+            }
             m_br.mk_and(path, c1, c2);
             if (m().is_false(c2))
                 result = nothing();
@@ -2970,7 +3012,11 @@ void seq_rewriter::mk_antimirov_deriv_rec(expr* e, expr* r, expr* path, expr_ref
         if (re().is_to_re(r2, r1)) {
             // here r1 is a sequence
             // observe that the precondition |r1|>0 of mk_seq_last is implied by c1
-            m_br.mk_and(m().mk_not(m().mk_eq(r1, str().mk_empty(seq_sort))), m().mk_eq(mk_seq_last(r1), e), c1);
+            {
+                auto is_non_empty = m().mk_not(m().mk_eq(r1, str().mk_empty(seq_sort)));
+                auto eq_last = m().mk_eq(mk_seq_last(r1), e);
+                m_br.mk_and(is_non_empty, eq_last, c1);
+            }
             m_br.mk_and(path, c1, c2);
             if (m().is_false(c2))
                 result = nothing();
@@ -3002,8 +3048,15 @@ void seq_rewriter::mk_antimirov_deriv_rec(expr* e, expr* r, expr* path, expr_ref
             result = mk_antimirov_deriv_union(c1, re().mk_ite_simplify(r1nullable, mk_antimirov_deriv(e, r2, path), nothing()));
     }
     else if (m().is_ite(r, c, r1, r2)) {
-        c1 = simplify_path(e, m().mk_and(c, path));
-        c2 = simplify_path(e, m().mk_and(m().mk_not(c), path));
+        {
+            auto cp = m().mk_and(c, path);
+            c1 = simplify_path(e, cp);
+        }
+        {
+            auto notc = m().mk_not(c);
+            auto np = m().mk_and(notc, path);
+            c2 = simplify_path(e, np);
+        }
         if (m().is_false(c1))
             result = mk_antimirov_deriv(e, r2, c2);
         else if (m().is_false(c2))
@@ -3018,7 +3071,11 @@ void seq_rewriter::mk_antimirov_deriv_rec(expr* e, expr* r, expr* path, expr_ref
             // SASSERT(u().is_char(c1));
             // SASSERT(u().is_char(c2));
             // case: c1 <= e <= c2
-            range = simplify_path(e, m().mk_and(u().mk_le(c1, e), u().mk_le(e, c2)));
+            // deterministic evaluation for range bounds
+            auto a_le = u().mk_le(c1, e);
+            auto b_le = u().mk_le(e, c2);
+            auto rng_cond = m().mk_and(a_le, b_le);
+            range = simplify_path(e, rng_cond);
             psi = simplify_path(e, m().mk_and(path, range));
         }
         else if (!str().is_string(r1) && str().is_unit_string(r2, c2)) {
@@ -3399,12 +3456,22 @@ expr_ref seq_rewriter::mk_regex_reverse(expr* r) {
         result = mk_regex_concat(mk_regex_reverse(r2), mk_regex_reverse(r1));
     else if (m().is_ite(r, c, r1, r2))
         result = m().mk_ite(c, mk_regex_reverse(r1), mk_regex_reverse(r2));
-    else if (re().is_union(r, r1, r2))
-        result = re().mk_union(mk_regex_reverse(r1), mk_regex_reverse(r2));
-    else if (re().is_intersection(r, r1, r2))
-        result = re().mk_inter(mk_regex_reverse(r1), mk_regex_reverse(r2));
-    else if (re().is_diff(r, r1, r2))
-        result = re().mk_diff(mk_regex_reverse(r1), mk_regex_reverse(r2));
+    else if (re().is_union(r, r1, r2)) {
+        // enforce deterministic evaluation order
+        auto a1 = mk_regex_reverse(r1);
+        auto b1 = mk_regex_reverse(r2);
+        result = re().mk_union(a1, b1);
+    }
+    else if (re().is_intersection(r, r1, r2)) {
+        auto a1 = mk_regex_reverse(r1);
+        auto b1 = mk_regex_reverse(r2);
+        result = re().mk_inter(a1, b1);
+    }
+    else if (re().is_diff(r, r1, r2)) {
+        auto a1 = mk_regex_reverse(r1);
+        auto b1 = mk_regex_reverse(r2);
+        result = re().mk_diff(a1, b1);
+    }
     else if (re().is_star(r, r1))
         result = re().mk_star(mk_regex_reverse(r1));
     else if (re().is_plus(r, r1))
@@ -3982,8 +4049,13 @@ expr_ref seq_rewriter::mk_derivative_rec(expr* ele, expr* r) {
             // if ((isdigit ele) and (ele = (hd r1))) then (to_re (tl r1)) else []
             //
             hd = mk_seq_first(r1);
-            m_br.mk_and(u().mk_le(m_util.mk_char('0'), ele), u().mk_le(ele, m_util.mk_char('9')), 
-                m().mk_and(m().mk_not(m().mk_eq(r1, str().mk_empty(seq_sort))), m().mk_eq(hd, ele)), result);
+            // isolate nested conjunction for deterministic evaluation
+            auto a0 = u().mk_le(m_util.mk_char('0'), ele);
+            auto a1 = u().mk_le(ele, m_util.mk_char('9'));
+            auto a2 = m().mk_not(m().mk_eq(r1, str().mk_empty(seq_sort)));
+            auto a3 = m().mk_eq(hd, ele);
+            auto inner = m().mk_and(a2, a3);
+            m_br.mk_and(a0, a1, inner, result);
             tl = re().mk_to_re(mk_seq_rest(r1));            
             return re_and(result, tl);
         }
@@ -4017,7 +4089,10 @@ expr_ref seq_rewriter::mk_derivative_rec(expr* ele, expr* r) {
                 // tl = rest of reverse(r2) i.e. butlast of r2
                 //hd = str().mk_nth_i(r2, m_autil.mk_sub(str().mk_length(r2), one()));
                 hd = mk_seq_last(r2);
-                m_br.mk_and(m().mk_not(m().mk_eq(r2, str().mk_empty(seq_sort))), m().mk_eq(hd, ele), result);
+                // factor nested constructor calls to enforce deterministic argument evaluation order
+                auto a_non_empty = m().mk_not(m().mk_eq(r2, str().mk_empty(seq_sort)));
+                auto a_eq        = m().mk_eq(hd, ele);
+                m_br.mk_and(a_non_empty, a_eq, result);
                 tl = re().mk_to_re(mk_seq_butlast(r2));
                 return re_and(result, re().mk_reverse(tl));
             }
@@ -4302,9 +4377,11 @@ br_status seq_rewriter::mk_str_in_regexp(expr* a, expr* b, expr_ref& result) {
         (re().is_union(b, b1, eps) && re().is_epsilon(eps)) ||
         (re().is_union(b, eps, b1) && re().is_epsilon(eps)))
     {
-        result = m().mk_ite(m().mk_eq(str().mk_length(a), zero()),
-            m().mk_true(),
-            re().mk_in_re(a, b1));
+        // deterministic evaluation order: build sub-expressions first
+        auto len_a = str().mk_length(a);
+        auto is_empty = m().mk_eq(len_a, zero());
+        auto in_b1 = re().mk_in_re(a, b1);
+        result = m().mk_ite(is_empty, m().mk_true(), in_b1);
         return BR_REWRITE_FULL;
     }
     if (str().is_empty(a)) {
@@ -4334,9 +4411,10 @@ br_status seq_rewriter::mk_str_in_regexp(expr* a, expr* b, expr_ref& result) {
         expr_ref len_hd(m_autil.mk_int(re().min_length(hd)), m()); 
         expr_ref len_a(str().mk_length(a), m());
         expr_ref len_tl(m_autil.mk_sub(len_a, len_hd), m());
-        result = m().mk_and(m_autil.mk_ge(len_a, len_hd),
-                            re().mk_in_re(str().mk_substr(a, zero(), len_hd), hd),
-                            re().mk_in_re(str().mk_substr(a, len_hd, len_tl), tl));
+        auto ge_len = m_autil.mk_ge(len_a, len_hd);
+        auto prefix = re().mk_in_re(str().mk_substr(a, zero(), len_hd), hd);
+        auto suffix = re().mk_in_re(str().mk_substr(a, len_hd, len_tl), tl);
+        result = m().mk_and(ge_len, prefix, suffix);
         return BR_REWRITE_FULL;
     }
     if (get_re_head_tail_reversed(b, hd, tl)) {
@@ -4345,10 +4423,11 @@ br_status seq_rewriter::mk_str_in_regexp(expr* a, expr* b, expr_ref& result) {
         expr_ref len_a(str().mk_length(a), m());
         expr_ref len_hd(m_autil.mk_sub(len_a, len_tl), m());
         expr* s = nullptr;
-        result = m().mk_and(m_autil.mk_ge(len_a, len_tl),
-            re().mk_in_re(str().mk_substr(a, zero(), len_hd), hd),
-            (re().is_to_re(tl, s) ? m().mk_eq(s, str().mk_substr(a, len_hd, len_tl)) :
-                re().mk_in_re(str().mk_substr(a, len_hd, len_tl), tl)));
+        auto ge_len = m_autil.mk_ge(len_a, len_tl);
+        auto prefix = re().mk_in_re(str().mk_substr(a, zero(), len_hd), hd);
+        auto tail_seq = str().mk_substr(a, len_hd, len_tl);
+        auto tail = (re().is_to_re(tl, s) ? m().mk_eq(s, tail_seq) : re().mk_in_re(tail_seq, tl));
+        result = m().mk_and(ge_len, prefix, tail);
         return BR_REWRITE_FULL;
     }
 
@@ -4614,11 +4693,17 @@ br_status seq_rewriter::mk_re_union(expr* a, expr* b, expr_ref& result) {
 br_status seq_rewriter::mk_re_complement(expr* a, expr_ref& result) {
     expr *e1 = nullptr, *e2 = nullptr;
     if (re().is_intersection(a, e1, e2)) {
-        result = re().mk_union(re().mk_complement(e1), re().mk_complement(e2));
+        // enforce deterministic evaluation order for nested complement arguments
+        auto a1 = re().mk_complement(e1);
+        auto b1 = re().mk_complement(e2);
+        result = re().mk_union(a1, b1);
         return BR_REWRITE2;
     }
     if (re().is_union(a, e1, e2)) {
-        result = re().mk_inter(re().mk_complement(e1), re().mk_complement(e2));
+        // enforce deterministic evaluation order for nested complement arguments
+        auto a1 = re().mk_complement(e1);
+        auto b1 = re().mk_complement(e2);
+        result = re().mk_inter(a1, b1);
         return BR_REWRITE2;
     }
     if (re().is_empty(a)) {
@@ -5011,7 +5096,9 @@ void seq_rewriter::elim_condition(expr* elem, expr_ref& cond) {
         rep.insert(elem, solution);
         rep(cond);
         if (!is_uninterp_const(elem)) { 
-            cond = m().mk_and(m().mk_eq(elem, solution), cond);
+            // ensure deterministic evaluation order when augmenting condition
+            auto eq_sol = m().mk_eq(elem, solution);
+            cond = m().mk_and(eq_sol, cond);
         }
     }    
     else if (all_ranges) {
@@ -5074,11 +5161,16 @@ br_status seq_rewriter::reduce_re_is_empty(expr* r, expr_ref& result) {
     }
     // Partial DNF expansion:
     else if (re().is_intersection(r, r1, r2) && re().is_union(r1, r3, r4)) {
-        result = eq_empty(re().mk_union(re().mk_inter(r3, r2), re().mk_inter(r4, r2)));
+        // enforce deterministic order for nested intersections inside union
+        auto a1 = re().mk_inter(r3, r2);
+        auto b1 = re().mk_inter(r4, r2);
+        result = eq_empty(re().mk_union(a1, b1));
         return BR_REWRITE3;
     }
     else if (re().is_intersection(r, r1, r2) && re().is_union(r2, r3, r4)) {
-        result = eq_empty(re().mk_union(re().mk_inter(r3, r1), re().mk_inter(r4, r1)));
+        auto a1 = re().mk_inter(r3, r1);
+        auto b1 = re().mk_inter(r4, r1);
+        result = eq_empty(re().mk_union(a1, b1));
         return BR_REWRITE3;
     }
     return BR_FAILED;
diff --git a/src/ast/sls/sls_bv_tracker.h b/src/ast/sls/sls_bv_tracker.h
index 7c9b02a46..5b228a36b 100644
--- a/src/ast/sls/sls_bv_tracker.h
+++ b/src/ast/sls/sls_bv_tracker.h
@@ -42,8 +42,37 @@ class sls_tracker {
     struct value_score {
         value_score() : value(unsynch_mpz_manager::mk_z(0)) {};
         value_score(value_score&&) noexcept = default;
+        value_score(const value_score &other) {
+            m = other.m;
+            if (other.m && !unsynch_mpz_manager::is_zero(other.value)) {
+                m->set(value, other.value);
+            }
+            score = other.score;
+            score_prune = other.score_prune;
+            has_pos_occ = other.has_pos_occ;
+            has_neg_occ = other.has_neg_occ;
+            distance = other.distance;
+            touched = other.touched;
+        }
         ~value_score() { if (m) m->del(value); }
-        value_score& operator=(value_score&&) = default;
+        value_score& operator=(value_score&&) noexcept = default;
+        value_score &operator=(const value_score &other) {
+            if (this != &other) {
+                if (m)
+                    m->del(value);
+                m = other.m;
+                if (other.m && !unsynch_mpz_manager::is_zero(other.value)) {
+                    m->set(value, other.value);
+                }
+                score = other.score;
+                score_prune = other.score_prune;
+                has_pos_occ = other.has_pos_occ;
+                has_neg_occ = other.has_neg_occ;
+                distance = other.distance;
+                touched = other.touched;
+            }
+            return *this;
+        }
         unsynch_mpz_manager * m = nullptr;
         mpz value;
         double score = 0.0;
diff --git a/src/cmd_context/extra_cmds/proof_cmds.cpp b/src/cmd_context/extra_cmds/proof_cmds.cpp
index ea585bfae..22348fd2b 100644
--- a/src/cmd_context/extra_cmds/proof_cmds.cpp
+++ b/src/cmd_context/extra_cmds/proof_cmds.cpp
@@ -314,7 +314,7 @@ public:
         if (m_trim)
             trim().assume(m_lits);
         if (m_on_clause_eh)
-            m_on_clause_eh(m_on_clause_ctx, assumption(), m_deps.size(), m_deps.data(), m_lits.size(), m_lits.data());
+            m_on_clause_eh(m_on_clause_ctx, assumption(), m_deps.size(), m_deps.data(), m_lits.size(), m_lits.data(), 0u);
         m_lits.reset();
         m_proof_hint.reset();
         m_deps.reset();
@@ -328,7 +328,7 @@ public:
         if (m_trim)
             trim().infer(m_lits, m_proof_hint);
         if (m_on_clause_eh)
-            m_on_clause_eh(m_on_clause_ctx, m_proof_hint, m_deps.size(), m_deps.data(), m_lits.size(), m_lits.data());
+            m_on_clause_eh(m_on_clause_ctx, m_proof_hint, m_deps.size(), m_deps.data(), m_lits.size(), m_lits.data(), 0u);
         m_lits.reset();
         m_proof_hint.reset();
         m_deps.reset();
@@ -342,7 +342,7 @@ public:
         if (m_trim)
             trim().del(m_lits);
         if (m_on_clause_eh)
-            m_on_clause_eh(m_on_clause_ctx, del(), m_deps.size(), m_deps.data(), m_lits.size(), m_lits.data());
+            m_on_clause_eh(m_on_clause_ctx, del(), m_deps.size(), m_deps.data(), m_lits.size(), m_lits.data(), 0u);
         m_lits.reset();
         m_proof_hint.reset();
         m_deps.reset();
diff --git a/src/nlsat/nlsat_explain.cpp b/src/nlsat/nlsat_explain.cpp
index 83c5f31b6..ff1ae6a07 100644
--- a/src/nlsat/nlsat_explain.cpp
+++ b/src/nlsat/nlsat_explain.cpp
@@ -1226,6 +1226,7 @@ namespace nlsat {
          * https://arxiv.org/abs/2003.00409 
          */
         void project_cdcac(polynomial_ref_vector & ps, var max_x) {
+            bool first = true;
             if (ps.empty())
                 return;
 
@@ -1244,8 +1245,6 @@ namespace nlsat {
             // Remark: after vanishing coefficients are eliminated, ps may not contain max_x anymore
             
             polynomial_ref_vector samples(m_pm);
-
-            
             if (x < max_x)
                 cac_add_cell_lits(ps, x, samples);
 
@@ -1256,9 +1255,18 @@ namespace nlsat {
                 }
                 TRACE(nlsat_explain, tout << "project loop, processing var "; display_var(tout, x); tout << "\npolynomials\n";
                       display(tout, ps); tout << "\n";);
-                add_lcs(ps, x);
-                psc_discriminant(ps, x);
-                psc_resultant(ps, x);
+                if (first) { // The first run is special because x is not constrained by the sample, we cannot surround it by the root functions.
+                    // we make the polynomials in ps delinable
+                    add_lcs(ps, x);
+                    psc_discriminant(ps, x);
+                    psc_resultant(ps, x);
+                    first = false;
+                }
+                else {
+                    add_lcs(ps, x);
+                    psc_discriminant(ps, x);
+                    psc_resultant_sample(ps, x, samples);
+                }
                 
                 if (m_todo.empty())
                     break;
diff --git a/src/sat/smt/euf_proof.cpp b/src/sat/smt/euf_proof.cpp
index 6f240a88d..b28f5e9a2 100644
--- a/src/sat/smt/euf_proof.cpp
+++ b/src/sat/smt/euf_proof.cpp
@@ -382,7 +382,7 @@ namespace euf {
         for (unsigned i = 0; i < n; ++i) 
             m_clause.push_back(literal2expr(lits[i]));
         auto hint = status2proof_hint(st);
-        m_on_clause(m_on_clause_ctx, hint, 0, nullptr, m_clause.size(), m_clause.data());
+        m_on_clause(m_on_clause_ctx, hint, 0, nullptr, m_clause.size(), m_clause.data(), 0u);
     }
 
     void solver::on_proof(unsigned n, literal const* lits, sat::status st) {
diff --git a/src/smt/smt_clause_proof.cpp b/src/smt/smt_clause_proof.cpp
index bc4105e13..b537a44dc 100644
--- a/src/smt/smt_clause_proof.cpp
+++ b/src/smt/smt_clause_proof.cpp
@@ -192,8 +192,19 @@ namespace smt {
         TRACE(clause_proof, tout << m_trail.size() << " " << st << " " << v << "\n";);
         if (ctx.get_fparams().m_clause_proof)
             m_trail.push_back(info(st, v, p));
-        if (m_on_clause_eh) 
-            m_on_clause_eh(m_on_clause_ctx, p, 0, nullptr, v.size(), v.data());
+        if (m_on_clause_eh) {
+            // Encode status as an integer flag for simplicity.
+            unsigned st_code = 0;
+            switch (st) {
+                case status::assumption:    st_code = 1; break;
+                case status::lemma:         st_code = 2; break;
+                case status::th_lemma:      st_code = 3; break;
+                case status::th_assumption: st_code = 4; break;
+                case status::deleted:       st_code = 5; break;
+                default:                    st_code = 0; break;
+            }
+            m_on_clause_eh(m_on_clause_ctx, p, 0, nullptr, v.size(), v.data(), st_code);
+        }
         
         if (m_has_log) {
             init_pp_out();
diff --git a/src/tactic/user_propagator_base.h b/src/tactic/user_propagator_base.h
index 1b480fb04..ffe87d27c 100644
--- a/src/tactic/user_propagator_base.h
+++ b/src/tactic/user_propagator_base.h
@@ -27,7 +27,7 @@ namespace user_propagator {
     typedef std::function<void(void*, callback*, unsigned)>                  pop_eh_t;
     typedef std::function<void(void*, callback*, expr*)>                     created_eh_t;
     typedef std::function<void(void*, callback*, expr*, unsigned, bool)>     decide_eh_t;
-    typedef std::function<void(void*, expr*, unsigned, unsigned const*, unsigned, expr* const*)>        on_clause_eh_t;
+    typedef std::function<void(void*, expr*, unsigned, unsigned const*, unsigned, expr* const*, unsigned const)>        on_clause_eh_t;
     typedef std::function<bool(void*, callback*, expr*, expr*)>              binding_eh_t;
 
     class plugin : public decl_plugin {
diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
index 206dc0530..77cf2f6fd 100644
--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -21,6 +21,7 @@ add_executable(test-z3
   api_polynomial.cpp
   api_pb.cpp
   api_datalog.cpp
+  parametric_datatype.cpp
   arith_rewriter.cpp
   arith_simplifier_plugin.cpp
   ast.cpp
diff --git a/src/test/main.cpp b/src/test/main.cpp
index c6bb23378..005b7ab59 100644
--- a/src/test/main.cpp
+++ b/src/test/main.cpp
@@ -179,6 +179,7 @@ int main(int argc, char ** argv) {
     TST(api_polynomial);
     TST(api_pb);
     TST(api_datalog);
+    TST(parametric_datatype);
     TST(cube_clause);
     TST(old_interval);
     TST(get_implied_equalities);
diff --git a/src/test/parametric_datatype.cpp b/src/test/parametric_datatype.cpp
new file mode 100644
index 000000000..2a31803aa
--- /dev/null
+++ b/src/test/parametric_datatype.cpp
@@ -0,0 +1,122 @@
+/*++
+Copyright (c) 2025 Microsoft Corporation
+
+Module Name:
+
+    parametric_datatype.cpp
+
+Abstract:
+
+    Test parametric datatypes with type variables.
+
+Author:
+
+    Copilot 2025-10-12
+
+--*/
+
+#include "api/z3.h"
+#include "util/util.h"
+#include <iostream>
+
+
+/**
+ * Test Z3_mk_polymorphic_datatype API with explicit parameters.
+ * 
+ * This test demonstrates the API that explicitly accepts type parameters.
+ */
+static void test_polymorphic_datatype_api() {
+    std::cout << "test_polymorphic_datatype_api\n";
+    
+    Z3_config cfg = Z3_mk_config();
+    Z3_context ctx = Z3_mk_context(cfg);
+    Z3_del_config(cfg);
+    
+    // Create type variables alpha and beta for polymorphic datatype
+    Z3_symbol alpha_sym = Z3_mk_string_symbol(ctx, "alpha");
+    Z3_symbol beta_sym = Z3_mk_string_symbol(ctx, "beta");
+    Z3_sort alpha = Z3_mk_type_variable(ctx, alpha_sym);
+    Z3_sort beta = Z3_mk_type_variable(ctx, beta_sym);
+    
+    // Define parametric triple datatype with constructor mk-triple(first: alpha, second: beta, third: alpha)
+    Z3_symbol triple_name = Z3_mk_string_symbol(ctx, "triple");
+    Z3_symbol mk_triple_name = Z3_mk_string_symbol(ctx, "mk-triple");
+    Z3_symbol is_triple_name = Z3_mk_string_symbol(ctx, "is-triple");
+    Z3_symbol first_name = Z3_mk_string_symbol(ctx, "first");
+    Z3_symbol second_name = Z3_mk_string_symbol(ctx, "second");
+    Z3_symbol third_name = Z3_mk_string_symbol(ctx, "third");
+    
+    Z3_symbol field_names[3] = {first_name, second_name, third_name};
+    Z3_sort field_sorts[3] = {alpha, beta, alpha};  // Use type variables
+    unsigned sort_refs[3] = {0, 0, 0};  // Not recursive references
+    
+    Z3_constructor mk_triple_con = Z3_mk_constructor(
+        ctx, mk_triple_name, is_triple_name, 3, field_names, field_sorts, sort_refs
+    );
+    
+    // Create the parametric datatype using Z3_mk_polymorphic_datatype
+    Z3_constructor constructors[1] = {mk_triple_con};
+    Z3_sort type_params[2] = {alpha, beta};
+    Z3_sort triple = Z3_mk_polymorphic_datatype(ctx, triple_name, 2, type_params, 1, constructors);
+    
+    Z3_del_constructor(ctx, mk_triple_con);
+    
+    std::cout << "Created parametric triple datatype using Z3_mk_polymorphic_datatype\n";
+    std::cout << "triple sort: " << Z3_sort_to_string(ctx, triple) << "\n";
+    
+    // Now instantiate the datatype with concrete types
+    Z3_sort int_sort = Z3_mk_int_sort(ctx);
+    Z3_sort bool_sort = Z3_mk_bool_sort(ctx);
+    
+    // Create (triple Int Bool)
+    Z3_sort params_int_bool[2] = {int_sort, bool_sort};
+    Z3_sort triple_int_bool = Z3_mk_datatype_sort(ctx, triple_name, 2, params_int_bool);
+    
+    std::cout << "Instantiated triple with Int and Bool\n";
+    std::cout << "triple_int_bool: " << Z3_sort_to_string(ctx, triple_int_bool) << "\n";
+    
+    // Get constructors and accessors from the instantiated datatype
+    Z3_func_decl mk_triple_int_bool = Z3_get_datatype_sort_constructor(ctx, triple_int_bool, 0);
+    Z3_func_decl first_int_bool = Z3_get_datatype_sort_constructor_accessor(ctx, triple_int_bool, 0, 0);
+    Z3_func_decl second_int_bool = Z3_get_datatype_sort_constructor_accessor(ctx, triple_int_bool, 0, 1);
+    Z3_func_decl third_int_bool = Z3_get_datatype_sort_constructor_accessor(ctx, triple_int_bool, 0, 2);
+    
+    std::cout << "Got constructors and accessors from instantiated datatype\n";
+    
+    // Create a constant t : (triple Int Bool)
+    Z3_symbol t_sym = Z3_mk_string_symbol(ctx, "t");
+    Z3_ast t = Z3_mk_const(ctx, t_sym, triple_int_bool);
+    
+    // Create (first t) - should be Int
+    Z3_ast first_t = Z3_mk_app(ctx, first_int_bool, 1, &t);
+    
+    // Create (third t) - should also be Int
+    Z3_ast third_t = Z3_mk_app(ctx, third_int_bool, 1, &t);
+    
+    // Create the equality (= (first t) (third t))
+    Z3_ast eq = Z3_mk_eq(ctx, first_t, third_t);
+    
+    std::cout << "Created term: " << Z3_ast_to_string(ctx, eq) << "\n";
+    
+    // Verify the term was created successfully
+    ENSURE(eq != nullptr);
+    
+    // Check that first_t and third_t have the same sort (Int)
+    Z3_sort first_t_sort = Z3_get_sort(ctx, first_t);
+    Z3_sort third_t_sort = Z3_get_sort(ctx, third_t);
+    
+    std::cout << "Sort of (first t): " << Z3_sort_to_string(ctx, first_t_sort) << "\n";
+    std::cout << "Sort of (third t): " << Z3_sort_to_string(ctx, third_t_sort) << "\n";
+    
+    // Both should be Int
+    ENSURE(Z3_is_eq_sort(ctx, first_t_sort, int_sort));
+    ENSURE(Z3_is_eq_sort(ctx, third_t_sort, int_sort));
+    
+    std::cout << "test_polymorphic_datatype_api passed!\n";
+    
+    Z3_del_context(ctx);
+}
+
+void tst_parametric_datatype() {
+    test_polymorphic_datatype_api();
+}
diff --git a/src/util/mpz.cpp b/src/util/mpz.cpp
index 0d4df44a2..94d95d85c 100644
--- a/src/util/mpz.cpp
+++ b/src/util/mpz.cpp
@@ -2332,7 +2332,6 @@ bool mpz_manager<SYNCH>::is_perfect_square(mpz const & a, mpz & root) {
     set(sq_lo, 1);    
 
     bool result = false;
-    bool first = true;
     // lo*lo <= *this < hi*hi
 
     // first find small interval lo*lo <= a <<= hi*hi
diff --git a/src/util/obj_hashtable.h b/src/util/obj_hashtable.h
index 36715facf..cf7cdff05 100644
--- a/src/util/obj_hashtable.h
+++ b/src/util/obj_hashtable.h
@@ -58,6 +58,13 @@ public:
     struct key_data {
         Key *  m_key = nullptr;
         Value  m_value;
+        key_data() {}
+        key_data(Key *key) : m_key(key) {}
+        key_data(Key *k, Value const &v) : m_key(k), m_value(v) {}
+        key_data(key_data &&kd) noexcept = default;
+        key_data(key_data const &kd) noexcept = default;
+        key_data &operator=(key_data const &kd)  = default;
+        key_data &operator=(key_data &&kd) = default;
         Value const & get_value() const { return m_value; }
         Key & get_key () const { return *m_key; }
         unsigned hash() const { return m_key->hash(); }
diff --git a/src/util/warning.cpp b/src/util/warning.cpp
index 033c93780..c7becf49f 100644
--- a/src/util/warning.cpp
+++ b/src/util/warning.cpp
@@ -24,6 +24,10 @@ Revision History:
 #include "util/buffer.h"
 #include "util/vector.h"
 
+#ifndef SINGLE_THREAD
+#include <mutex>
+#endif
+
 #ifdef _WINDOWS
 #if defined( __MINGW32__ ) && ( defined( __GNUG__ ) || defined( __clang__ ) )
 #include <crtdbg.h>
@@ -67,6 +71,10 @@ static bool g_use_std_stdout = false;
 static std::ostream* g_error_stream = nullptr;
 static std::ostream* g_warning_stream = nullptr;
 
+#ifndef SINGLE_THREAD
+static std::mutex g_warning_mutex;
+#endif
+
 void send_warnings_to_stdout(bool flag) {
     g_use_std_stdout = flag;
 }
@@ -129,6 +137,9 @@ void print_msg(std::ostream * out, const char* prefix, const char* msg, va_list
 
 void warning_msg(const char * msg, ...) {
     if (g_warning_msgs) {
+#ifndef SINGLE_THREAD
+        std::lock_guard<std::mutex> lock(g_warning_mutex);
+#endif
         va_list args;
         va_start(args, msg);
         print_msg(g_warning_stream, "WARNING: ", msg, args);