diff --git a/src/th-cstor/Sidekick_th_cstor.ml b/src/th-cstor/Sidekick_th_cstor.ml
new file mode 100644
index 00000000..f8579db4
--- /dev/null
+++ b/src/th-cstor/Sidekick_th_cstor.ml
@@ -0,0 +1,95 @@
+
+(** {1 Theory for constructors} *)
+
+type ('c,'t) cstor_view =
+  | T_cstor of 'c * 't list
+  | T_other of 't
+
+module type S = sig
+  type lit
+  type term
+
+  (** Micro theory only *)
+  val cc_th : Sidekick_smt.CC.Theory.t
+end
+
+module type ARG = sig
+  module Fun : sig
+    type t
+    val equal : t -> t -> bool
+end
+  module T : sig
+    type t
+    val pp : t Fmt.printer
+    val equal : t -> t -> bool
+    val view_as_cstor : t -> (Fun.t,t) cstor_view
+  end
+end
+
+module Make(Arg : ARG with type T.t = Sidekick_smt.Term.t)
+(*   : S with type lit = Arg.Lit.t and type term = Arg.T.t *)
+= struct
+  module N = Sidekick_smt.Theory.CC_eq_class
+  module Expl = Sidekick_smt.Theory.CC_expl
+  module CC = Sidekick_smt.CC
+
+  open Arg
+  type term = T.t
+
+  type data = {
+    t: T.t;
+    n: N.t;
+  }
+  (* associate to each class a unique constructor term in the class (if any) *)
+
+  let pp_data out x = T.pp out x.t
+
+  let key : (_,_,data) Sidekick_cc.Key.t = Sidekick_cc.Key.create
+      ~pp:pp_data ~name:"cstor"
+      ~eq:(fun x y -> T.equal x.t y.t)
+      ~merge:(fun x _ -> x) ()
+
+  type t = unit
+
+  let on_merge (cc:CC.t) n1 tc1 n2 tc2 e_n1_n2 : unit =
+    Log.debugf 5
+      (fun k->k "(@[th-cstor.on_merge@ @[:c1 %a@ (term %a)@]@ @[:c2 %a@ (term %a)@]@])"
+          N.pp n1 T.pp tc1.t N.pp n2 T.pp tc2.t); 
+    let expl = Expl.mk_list [e_n1_n2; Expl.mk_merge n1 tc1.n; Expl.mk_merge n2 tc2.n] in
+    match T.view_as_cstor tc1.t, T.view_as_cstor tc2.t with
+    | T_cstor (f1, l1), T_cstor (f2, l2) ->
+      if Arg.Fun.equal f1 f2 then (
+        (* same function: injectivity *)
+        assert (List.length l1 = List.length l2);
+        List.iter2
+          (fun u1 u2 -> CC.Theory.merge cc (CC.add_term cc u1) (CC.add_term cc u2) expl)
+          l1 l2
+      ) else (
+        (* different function: disjointness *)
+        CC.Theory.raise_conflict cc expl
+      )
+    | _ -> assert false
+
+  let on_new_term _ n (t:T.t) =
+    match T.view_as_cstor t with
+    | T_cstor _ -> Some {t;n}
+    | _ -> None
+
+  let cc_th = Sidekick_smt.CC.Theory.make ~key ~on_new_term ~on_merge ()
+end
+
+
+(* TODO: default building of constructor terms
+include Make(struct
+    module Fun = Sidekick_smt.Cst
+    module T = struct
+      include Sidekick_smt.Term
+      let[@inline] view_as_cstor t = match view t with
+        | App_cst (c, args) when Fun.do_cc
+        | If (a,b,c) -> T_ite (a,b,c)
+        | Bool b -> T_bool b
+        | _ -> T_other t
+      end
+    end)
+   *)
+
diff --git a/src/th-cstor/dune b/src/th-cstor/dune
new file mode 100644
index 00000000..667e77f2
--- /dev/null
+++ b/src/th-cstor/dune
@@ -0,0 +1,7 @@
+
+(library
+  (name Sidekick_th_cstor)
+  (public_name sidekick.smt.th-cstor)
+  (libraries containers sidekick.smt)
+  (flags :standard -open Sidekick_util))
+