diff --git a/src/collector.ml b/src/core/collector.ml
similarity index 100%
rename from src/collector.ml
rename to src/core/collector.ml
diff --git a/src/core/dune b/src/core/dune
new file mode 100644
index 0000000..2240246
--- /dev/null
+++ b/src/core/dune
@@ -0,0 +1,12 @@
+
+(library
+ (name trace_core)
+ (public_name trace.core)
+ (synopsis "Lightweight stub for tracing")
+)
+
+(rule
+  (targets atomic_.ml)
+  (action
+    (with-stdout-to %{targets}
+     (run ./gen/gen.exe --ocaml %{ocaml_version} --atomic))))
diff --git a/src/gen/dune b/src/core/gen/dune
similarity index 100%
rename from src/gen/dune
rename to src/core/gen/dune
diff --git a/src/gen/gen.ml b/src/core/gen/gen.ml
similarity index 100%
rename from src/gen/gen.ml
rename to src/core/gen/gen.ml
diff --git a/src/core/trace_core.ml b/src/core/trace_core.ml
new file mode 100644
index 0000000..c8b5209
--- /dev/null
+++ b/src/core/trace_core.ml
@@ -0,0 +1,115 @@
+include Types
+module A = Atomic_
+module Collector = Collector
+
+type collector = (module Collector.S)
+
+(** Global collector. *)
+let collector : collector option A.t = A.make None
+
+let[@inline] enabled () =
+  match A.get collector with
+  | None -> false
+  | Some _ -> true
+
+let enter_span_collector_ (module C : Collector.S) ?__FUNCTION__ ~__FILE__
+    ~__LINE__ ?(data = fun () -> []) name : span =
+  let data = data () in
+  C.enter_span ?__FUNCTION__ ~__FILE__ ~__LINE__ ~data name
+
+let[@inline] enter_span ?__FUNCTION__ ~__FILE__ ~__LINE__ ?data name : span =
+  match A.get collector with
+  | None -> Collector.dummy_span
+  | Some coll ->
+    enter_span_collector_ coll ?__FUNCTION__ ~__FILE__ ~__LINE__ ?data name
+
+let[@inline] exit_span span : unit =
+  match A.get collector with
+  | None -> ()
+  | Some (module C) -> C.exit_span span
+
+let with_span_collector_ (module C : Collector.S) ?__FUNCTION__ ~__FILE__
+    ~__LINE__ ?(data = fun () -> []) name f =
+  let data = data () in
+  let sp = C.enter_span ?__FUNCTION__ ~__FILE__ ~__LINE__ ~data name in
+  match f sp with
+  | x ->
+    C.exit_span sp;
+    x
+  | exception exn ->
+    let bt = Printexc.get_raw_backtrace () in
+    C.exit_span sp;
+    Printexc.raise_with_backtrace exn bt
+
+let[@inline] with_span ?__FUNCTION__ ~__FILE__ ~__LINE__ ?data name f =
+  match A.get collector with
+  | None ->
+    (* fast path: no collector, no span *)
+    f Collector.dummy_span
+  | Some collector ->
+    with_span_collector_ collector ?__FUNCTION__ ~__FILE__ ~__LINE__ ?data name
+      f
+
+let message_collector_ (module C : Collector.S) ?span ?(data = fun () -> []) msg
+    : unit =
+  let data = data () in
+  C.message ?span ~data msg
+
+let[@inline] message ?span ?data msg : unit =
+  match A.get collector with
+  | None -> ()
+  | Some coll -> message_collector_ coll ?span ?data msg
+
+let messagef ?span ?data k =
+  match A.get collector with
+  | None -> ()
+  | Some (module C) ->
+    k (fun fmt ->
+        Format.kasprintf
+          (fun str ->
+            let data =
+              match data with
+              | None -> []
+              | Some f -> f ()
+            in
+            C.message ?span ~data str)
+          fmt)
+
+let counter_int name n : unit =
+  match A.get collector with
+  | None -> ()
+  | Some (module C) -> C.counter_int name n
+
+let counter_float name f : unit =
+  match A.get collector with
+  | None -> ()
+  | Some (module C) -> C.counter_float name f
+
+let set_thread_name name : unit =
+  match A.get collector with
+  | None -> ()
+  | Some (module C) -> C.name_thread name
+
+let set_process_name name : unit =
+  match A.get collector with
+  | None -> ()
+  | Some (module C) -> C.name_process name
+
+let setup_collector c : unit =
+  while
+    let cur = A.get collector in
+    match cur with
+    | Some _ -> invalid_arg "trace: collector already present"
+    | None -> not (A.compare_and_set collector cur (Some c))
+  do
+    ()
+  done
+
+let shutdown () =
+  match A.exchange collector None with
+  | None -> ()
+  | Some (module C) -> C.shutdown ()
+
+module Internal_ = struct
+  module Atomic_ = Atomic_
+end
diff --git a/src/trace.mli b/src/core/trace_core.mli
similarity index 100%
rename from src/trace.mli
rename to src/core/trace_core.mli
diff --git a/src/types.ml b/src/core/types.ml
similarity index 100%
rename from src/types.ml
rename to src/core/types.ml
diff --git a/src/dune b/src/dune
index f26ef78..82c7d7f 100644
--- a/src/dune
+++ b/src/dune
@@ -1,11 +1,6 @@
 (library
+ (name trace)
  (public_name trace)
  (synopsis "Lightweight stub for tracing")
- (name trace)
+ (libraries trace.core)
 )
-
-(rule
-  (targets atomic_.ml)
-  (action
-    (with-stdout-to %{targets}
-     (run ./gen/gen.exe --ocaml %{ocaml_version} --atomic))))
diff --git a/src/trace.ml b/src/trace.ml
index c8b5209..5684517 100644
--- a/src/trace.ml
+++ b/src/trace.ml
@@ -1,115 +1 @@
-include Types
-module A = Atomic_
-module Collector = Collector
-
-type collector = (module Collector.S)
-
-(** Global collector. *)
-let collector : collector option A.t = A.make None
-
-let[@inline] enabled () =
-  match A.get collector with
-  | None -> false
-  | Some _ -> true
-
-let enter_span_collector_ (module C : Collector.S) ?__FUNCTION__ ~__FILE__
-    ~__LINE__ ?(data = fun () -> []) name : span =
-  let data = data () in
-  C.enter_span ?__FUNCTION__ ~__FILE__ ~__LINE__ ~data name
-
-let[@inline] enter_span ?__FUNCTION__ ~__FILE__ ~__LINE__ ?data name : span =
-  match A.get collector with
-  | None -> Collector.dummy_span
-  | Some coll ->
-    enter_span_collector_ coll ?__FUNCTION__ ~__FILE__ ~__LINE__ ?data name
-
-let[@inline] exit_span span : unit =
-  match A.get collector with
-  | None -> ()
-  | Some (module C) -> C.exit_span span
-
-let with_span_collector_ (module C : Collector.S) ?__FUNCTION__ ~__FILE__
-    ~__LINE__ ?(data = fun () -> []) name f =
-  let data = data () in
-  let sp = C.enter_span ?__FUNCTION__ ~__FILE__ ~__LINE__ ~data name in
-  match f sp with
-  | x ->
-    C.exit_span sp;
-    x
-  | exception exn ->
-    let bt = Printexc.get_raw_backtrace () in
-    C.exit_span sp;
-    Printexc.raise_with_backtrace exn bt
-
-let[@inline] with_span ?__FUNCTION__ ~__FILE__ ~__LINE__ ?data name f =
-  match A.get collector with
-  | None ->
-    (* fast path: no collector, no span *)
-    f Collector.dummy_span
-  | Some collector ->
-    with_span_collector_ collector ?__FUNCTION__ ~__FILE__ ~__LINE__ ?data name
-      f
-
-let message_collector_ (module C : Collector.S) ?span ?(data = fun () -> []) msg
-    : unit =
-  let data = data () in
-  C.message ?span ~data msg
-
-let[@inline] message ?span ?data msg : unit =
-  match A.get collector with
-  | None -> ()
-  | Some coll -> message_collector_ coll ?span ?data msg
-
-let messagef ?span ?data k =
-  match A.get collector with
-  | None -> ()
-  | Some (module C) ->
-    k (fun fmt ->
-        Format.kasprintf
-          (fun str ->
-            let data =
-              match data with
-              | None -> []
-              | Some f -> f ()
-            in
-            C.message ?span ~data str)
-          fmt)
-
-let counter_int name n : unit =
-  match A.get collector with
-  | None -> ()
-  | Some (module C) -> C.counter_int name n
-
-let counter_float name f : unit =
-  match A.get collector with
-  | None -> ()
-  | Some (module C) -> C.counter_float name f
-
-let set_thread_name name : unit =
-  match A.get collector with
-  | None -> ()
-  | Some (module C) -> C.name_thread name
-
-let set_process_name name : unit =
-  match A.get collector with
-  | None -> ()
-  | Some (module C) -> C.name_process name
-
-let setup_collector c : unit =
-  while
-    let cur = A.get collector in
-    match cur with
-    | Some _ -> invalid_arg "trace: collector already present"
-    | None -> not (A.compare_and_set collector cur (Some c))
-  do
-    ()
-  done
-
-let shutdown () =
-  match A.exchange collector None with
-  | None -> ()
-  | Some (module C) -> C.shutdown ()
-
-module Internal_ = struct
-  module Atomic_ = Atomic_
-end
+include Trace_core