diff --git a/dune-project b/dune-project
index 41c8548c..fe1a05c9 100644
--- a/dune-project
+++ b/dune-project
@@ -28,12 +28,18 @@
   dune
   (either
    (>= 1.0))
-  (trace :with-test)
-  (trace-tef :with-test)
-  (qcheck-core
-   (and
-    :with-test
-    (>= 0.19)))
+   (trace
+    (and
+     (>= 0.11)
+     :with-test))
+   (trace-tef
+    (and
+     (>= 0.11)
+     :with-test))
+   (qcheck-core
+    (and
+     :with-test
+     (>= 0.21)))
   (thread-local-storage
    (and
     (>= 0.2)
@@ -71,12 +77,18 @@
   (qcheck-core
    (and
     :with-test
-    (>= 0.19)))
+    (>= 0.21)))
   (hmap :with-test)
   (lwt (and (>= 5.0) (< 6.0)))
   base-unix
-  (trace :with-test)
-  (trace-tef :with-test)
+  (trace
+   (and
+    (>= 0.11)
+    :with-test))
+  (trace-tef
+   (and
+    (>= 0.11)
+    :with-test))
   (odoc :with-doc)))
 
 ; See the complete stanza docs at https://dune.readthedocs.io/en/stable/dune-files.html#dune-project
diff --git a/moonpool-lwt.opam b/moonpool-lwt.opam
index ff45e28b..22e4e492 100644
--- a/moonpool-lwt.opam
+++ b/moonpool-lwt.opam
@@ -11,12 +11,12 @@ depends: [
   "dune" {>= "3.0"}
   "moonpool" {= version}
   "ocaml" {>= "5.0"}
-  "qcheck-core" {with-test & >= "0.19"}
+  "qcheck-core" {with-test & >= "0.21"}
   "hmap" {with-test}
   "lwt" {>= "5.0" & < "6.0"}
   "base-unix"
-  "trace" {with-test}
-  "trace-tef" {with-test}
+  "trace" {>= "0.11" & with-test}
+  "trace-tef" {>= "0.11" & with-test}
   "odoc" {with-doc}
 ]
 build: [
diff --git a/moonpool.opam b/moonpool.opam
index 53301ff4..8a3d5b8a 100644
--- a/moonpool.opam
+++ b/moonpool.opam
@@ -12,9 +12,9 @@ depends: [
   "ocaml" {>= "5.0"}
   "dune" {>= "3.0"}
   "either" {>= "1.0"}
-  "trace" {with-test}
-  "trace-tef" {with-test}
-  "qcheck-core" {with-test & >= "0.19"}
+  "trace" {>= "0.11" & with-test}
+  "trace-tef" {>= "0.11" & with-test}
+  "qcheck-core" {with-test & >= "0.21"}
   "thread-local-storage" {>= "0.2" & < "0.3"}
   "odoc" {with-doc}
   "hmap" {with-test}
diff --git a/test/effect-based/t_fork_join.ml b/test/effect-based/t_fork_join.ml
index 5000c23c..f81a58ef 100644
--- a/test/effect-based/t_fork_join.ml
+++ b/test/effect-based/t_fork_join.ml
@@ -171,7 +171,7 @@ module Evaluator = struct
 
   let gen_fun =
     Q.Gen.(
-      frequency
+      oneof_weighted
         [
           ( 2,
             let+ n = 0 -- 100 in
@@ -190,7 +190,7 @@ module Evaluator = struct
         abs x
     in
     let open Q.Gen in
-    frequency
+    oneof_weighted
       [
         ( 1,
           let+ x = 1 -- 10000 in
@@ -208,13 +208,13 @@ module Evaluator = struct
           let+ f = gen_fun
           and+ csize = 1 -- 16
           and+ l = list_size (0 -- 290) (gen 1)
-          and+ r = oneofl [ R_add; R_max; R_add_shift ] in
+          and+ r = oneof_list [ R_add; R_max; R_add_shift ] in
           Map_arr (csize, f, l, r) );
         ( clamp_if_base 2,
           let+ f = gen_fun
           and+ csize = 1 -- 3
           and+ l = list_size (1 -- 7) (gen (min 3 (n - 1)))
-          and+ r = oneofl [ R_add; R_max; R_add_shift ] in
+          and+ r = oneof_list [ R_add; R_max; R_add_shift ] in
           Map_arr (csize, f, l, r) );
       ]
 
@@ -280,7 +280,7 @@ let t_for_nested ~min ~chunk_size () =
   let neg x = -x in
   Q.Test.make
     ~name:(spf "t_for_nested ~min:%d" min)
-    Q.(small_list (small_list small_int))
+    Q.(list_small (list_small nat_small))
     (fun l ->
       let ref_l1 = List.map (List.map neg) l in
       let ref_l2 = List.map (List.map neg) ref_l1 in
@@ -302,7 +302,7 @@ let t_for_nested ~min ~chunk_size () =
 let t_map ~chunk_size () =
   let ppa = Q.Print.(array string) in
   Q.Test.make ~name:"map1"
-    Q.(small_list small_int |> Q.set_stats [ "len", List.length ])
+    Q.(list_small nat_small |> Q.set_stats [ "len", List.length ])
     (fun l ->
       let@ pool = Ws_pool.with_ ~num_threads:4 () in
       let@ () = Ws_pool.run_wait_block pool in
diff --git a/test/lwt/echo_client.ml b/test/lwt/echo_client.ml
index 25a05b37..ee098551 100644
--- a/test/lwt/echo_client.ml
+++ b/test/lwt/echo_client.ml
@@ -25,7 +25,7 @@ let main ~port ~n ~n_conn ~verbose ~msg_per_conn () : unit =
 
     let@ () = M_lwt.spawn_lwt in
     let _sp =
-      Trace.enter_manual_span ~parent:None ~__FILE__ ~__LINE__ "connect.client"
+      Trace.enter_span ~parent:None ~__FILE__ ~__LINE__ "connect.client"
     in
     Trace.message "connecting new client…";
 
@@ -43,9 +43,7 @@ let main ~port ~n ~n_conn ~verbose ~msg_per_conn () : unit =
 
     for _j = 1 to msg_per_conn do
       let _sp =
-        Trace.enter_manual_span
-          ~parent:(Some (Trace.ctx_of_span _sp))
-          ~__FILE__ ~__LINE__ "write.loop"
+        Trace.enter_span ~parent:(Some _sp) ~__FILE__ ~__LINE__ "write.loop"
       in
 
       let s = spf "hello %d" _j in
@@ -57,10 +55,10 @@ let main ~port ~n ~n_conn ~verbose ~msg_per_conn () : unit =
       Lwt_io.read_into_exactly ic buf 0 (String.length s) |> await_lwt;
       if verbose then
         Printf.printf "read: %s\n%!" (Bytes.sub_string buf 0 (String.length s));
-      Trace.exit_manual_span _sp;
+      Trace.exit_span _sp;
       ()
     done;
-    Trace.exit_manual_span _sp
+    Trace.exit_span _sp
   in
 
   (* start the first [n_conn] tasks *)
diff --git a/test/lwt/echo_server.ml b/test/lwt/echo_server.ml
index b603257f..9d4b3630 100644
--- a/test/lwt/echo_server.ml
+++ b/test/lwt/echo_server.ml
@@ -22,7 +22,7 @@ let main ~port ~verbose ~runner:_ () : unit =
   let handle_client client_addr (ic, oc) : _ Lwt.t =
     let@ () = M_lwt.spawn_lwt in
     let _sp =
-      Trace.enter_manual_span ~parent:None ~__FILE__ ~__LINE__ "handle.client"
+      Trace.enter_span ~parent:None ~__FILE__ ~__LINE__ "handle.client"
         ~data:(fun () -> [ "addr", `String (str_of_sockaddr client_addr) ])
     in
 
@@ -45,7 +45,7 @@ let main ~port ~verbose ~runner:_ () : unit =
     done;
     if verbose then
       Printf.printf "done with client on %s\n%!" (str_of_sockaddr client_addr);
-    Trace.exit_manual_span _sp;
+    Trace.exit_span _sp;
     Trace.message "exit handle client"
   in
 
diff --git a/test/lwt/hash_client.ml b/test/lwt/hash_client.ml
index 1e807184..eb6d7d87 100644
--- a/test/lwt/hash_client.ml
+++ b/test/lwt/hash_client.ml
@@ -21,9 +21,7 @@ let main ~port ~ext ~dir ~n_conn () : unit =
   (* TODO: *)
   let run_task () : unit Lwt.t =
     let@ () = M_lwt.spawn_lwt in
-    let _sp =
-      Trace.enter_manual_span ~parent:None ~__FILE__ ~__LINE__ "run-task"
-    in
+    let _sp = Trace.enter_span ~parent:None ~__FILE__ ~__LINE__ "run-task" in
 
     let seen = Str_tbl.create 16 in
 
@@ -35,9 +33,7 @@ let main ~port ~ext ~dir ~n_conn () : unit =
         ()
       else if Sys.is_directory file then (
         let _sp =
-          Trace.enter_manual_span
-            ~parent:(Some (Trace.ctx_of_span _sp))
-            ~__FILE__ ~__LINE__ "walk-dir"
+          Trace.enter_span ~parent:(Some _sp) ~__FILE__ ~__LINE__ "walk-dir"
             ~data:(fun () -> [ "d", `String file ])
         in
 
@@ -55,7 +51,7 @@ let main ~port ~ext ~dir ~n_conn () : unit =
       )
     in
     walk dir;
-    Trace.exit_manual_span _sp
+    Trace.exit_span _sp
   in
 
   (* start the first [n_conn] tasks *)
diff --git a/test/lwt/hash_server.ml b/test/lwt/hash_server.ml
index e7028176..f689b749 100644
--- a/test/lwt/hash_server.ml
+++ b/test/lwt/hash_server.ml
@@ -167,7 +167,7 @@ let main ~port ~runner () : unit =
   let handle_client client_addr (ic, oc) =
     let@ () = Moonpool_lwt.spawn_lwt in
     let _sp =
-      Trace.enter_manual_span ~parent:None ~__FILE__ ~__LINE__ "handle.client"
+      Trace.enter_span ~parent:None ~__FILE__ ~__LINE__ "handle.client"
         ~data:(fun () -> [ "addr", `String (str_of_sockaddr client_addr) ])
     in
 
@@ -199,7 +199,7 @@ let main ~port ~runner () : unit =
           Lwt_io.flush oc |> await_lwt
       done
     with End_of_file | Unix.Unix_error (Unix.ECONNRESET, _, _) ->
-      Trace.exit_manual_span _sp;
+      Trace.exit_span _sp;
       Trace.message "exit handle client"
   in
 
diff --git a/test/t_props.ml b/test/t_props.ml
index fe187073..e3484d75 100644
--- a/test/t_props.ml
+++ b/test/t_props.ml
@@ -13,7 +13,7 @@ let with_pool ~kind () f =
 let () =
   add_test @@ fun ~kind ->
   Q.Test.make ~name:"map then join_list"
-    Q.(small_list small_int)
+    Q.(list_small nat_small)
     (fun l ->
       let@ pool = with_pool ~kind () in
       let l' = List.map (fun x -> Fut.spawn ~on:pool (fun () -> x + 1)) l in
@@ -24,7 +24,7 @@ let () =
 let () =
   add_test @@ fun ~kind ->
   Q.Test.make ~name:"map bind"
-    Q.(small_list small_int)
+    Q.(list_small nat_small)
     (fun l ->
       let@ pool = with_pool ~kind () in
       let open Fut.Infix in