diff --git a/src/not-so-smart/fetch.ml b/src/not-so-smart/fetch.ml
index 585a4fb17..fbd091ded 100644
--- a/src/not-so-smart/fetch.ml
+++ b/src/not-so-smart/fetch.ml
@@ -75,8 +75,6 @@ struct
         List.fold_left fold [] have |> List.split
 
   module V1 = struct
-    module Smart_flow = State_flow.Make (Smart)
-
     let fetch ?(uses_git_transport = false) ?(push_stdout = ignore)
         ?(push_stderr = ignore) ~capabilities ?deepen ?want:(refs = `None) ~host
         path flow store access fetch_cfg push_pack =
@@ -106,7 +104,7 @@ struct
 
       let ctx = Smart.Context.make ~client_caps in
 
-      Smart_flow.run sched io_raise io flow (prelude ctx) |> prj
+      State_flow.run sched io_raise Smart.pp_error io flow (prelude ctx) |> prj
       >>= fun (uids, refs) ->
       let hex =
         { Neg.to_hex = Uid.to_hex; of_hex = Uid.of_hex; compare = Uid.compare }
@@ -131,7 +129,9 @@ struct
           if res < 0 then Log.warn (fun m -> m "No common commits");
           let rec read_pack () =
             Log.debug (fun m -> m "Reading PACK file...");
-            Smart_flow.run sched io_raise io flow (recv_pack_state ctx) |> prj
+            State_flow.run sched io_raise Smart.pp_error io flow
+              (recv_pack_state ctx)
+            |> prj
             >>= fun should_continue ->
             if should_continue then read_pack () else return ()
           in
@@ -140,8 +140,6 @@ struct
   end
 
   module V2 = struct
-    module State_flow = State_flow.Make (Wire_proto_v2)
-
     let connect ?(uses_git_transport = false) ~host ~path ctx =
       let open Wire_proto_v2.Syntax in
       let return = Wire_proto_v2.return in
@@ -162,7 +160,9 @@ struct
         let* () = Wire_proto_v2.send ctx Flush () in
         Wire_proto_v2.return caps
       in
-      State_flow.run sched io_raise io flow (get_caps ctx) |> prj
+      State_flow.run sched io_raise Wire_proto_v2.pp_error io flow
+        (get_caps ctx)
+      |> prj
 
     let ls_refs_request ?(uses_git_transport = false) ~host ~path ctx flow req =
       let ls_refs_resp =
@@ -172,6 +172,7 @@ struct
         let* () = Wire_proto_v2.send ctx Ls_refs_req (`Client_caps caps, req) in
         Wire_proto_v2.recv ctx Ls_refs_res
       in
-      State_flow.run sched io_raise io flow ls_refs_resp |> prj
+      State_flow.run sched io_raise Wire_proto_v2.pp_error io flow ls_refs_resp
+      |> prj
   end
 end
diff --git a/src/not-so-smart/find_common.ml b/src/not-so-smart/find_common.ml
index d425ad1cf..5407c90c5 100644
--- a/src/not-so-smart/find_common.ml
+++ b/src/not-so-smart/find_common.ml
@@ -61,8 +61,6 @@ let io_monad (type t) { bind; return } =
    with Smart.v1 and implement a state of the art synchronisation algorithm, I
    translated as is [fetch-pack.c:find_common] in OCaml. *)
 
-module Smart_flow = State_flow.Make (Smart)
-
 let tips (type t) scheduler access store negotiator =
   let open (val io_monad scheduler : Io_monad with type s = t) in
   access.locals store >>= fun ref_lst ->
@@ -76,13 +74,15 @@ let consume_shallow_list (type t) scheduler io flow cfg deepen { of_hex; _ } ctx
     =
   let open (val io_monad scheduler : Io_monad with type s = t) in
   if cfg.stateless && Option.is_some deepen then
-    Smart_flow.run scheduler raise io flow Smart.(recv ctx shallows)
+    State_flow.run scheduler raise Smart.pp_error io flow
+      Smart.(recv ctx shallows)
     >>| fun shallows -> List.map (Smart.Shallow.map ~f:of_hex) shallows
   else return []
 
 let handle_shallow (type t) scheduler io flow { of_hex; _ } access store ctx =
   let open (val io_monad scheduler : Io_monad with type s = t) in
-  Smart_flow.run scheduler raise io flow Smart.(recv ctx shallows)
+  State_flow.run scheduler raise Smart.pp_error io flow
+    Smart.(recv ctx shallows)
   >>= fun shallows ->
   let shallows = List.map (Smart.Shallow.map ~f:of_hex) shallows in
   fold_left_s shallows ~init:() ~f:(fun () -> function
@@ -115,13 +115,14 @@ let find_common (type t) scheduler io flow cfg
   >>= function
   | [] ->
       Log.debug (fun m -> m "Nothing to download.");
-      Smart_flow.run scheduler raise io flow Smart.(send ctx flush ())
+      State_flow.run scheduler raise Smart.pp_error io flow
+        Smart.(send ctx flush ())
       >>= fun () -> return `Close
   | (uid, _) :: others as refs ->
       Log.debug (fun m -> m "We want %d commit(s)." (List.length refs));
       access.shallowed store >>= fun shallowed ->
       let shallowed = List.map to_hex shallowed in
-      Smart_flow.run scheduler raise io flow
+      State_flow.run scheduler raise Smart.pp_error io flow
         Smart.(
           let uid = to_hex uid in
           let others = List.map (fun (uid, _) -> to_hex uid) others in
@@ -164,7 +165,8 @@ let find_common (type t) scheduler io flow cfg
                 m "count: %d, in-vain: %d, flush-at: %d.\n%!" !count !in_vain
                   !flush_at);
             if !flush_at <= !count then (
-              Smart_flow.run scheduler raise io flow Smart.(send ctx flush ())
+              State_flow.run scheduler raise Smart.pp_error io flow
+                Smart.(send ctx flush ())
               >>= fun () ->
               incr flushes;
               flush_at := next_flush stateless !count;
@@ -173,7 +175,8 @@ let find_common (type t) scheduler io flow cfg
                 consume_shallow_list scheduler io flow cfg None hex ctx
                 >>= fun _shallows ->
                 let rec loop () =
-                  Smart_flow.run scheduler raise io flow Smart.(recv ctx ack)
+                  State_flow.run scheduler raise Smart.pp_error io flow
+                    Smart.(recv ctx ack)
                   >>| Smart.Negotiation.map ~f:of_hex
                   >>= fun ack ->
                   match ack with
@@ -238,7 +241,7 @@ let find_common (type t) scheduler io flow cfg
       Log.debug (fun m ->
           m "Negotiation (got ready: %b, no-done: %b)." !got_ready no_done);
       (if (not !got_ready) || not no_done then
-       Smart_flow.run scheduler raise io flow
+       State_flow.run scheduler raise Smart.pp_error io flow
          Smart.(send ctx negotiation_done ())
       else return ())
       >>= fun () ->
@@ -247,14 +250,16 @@ let find_common (type t) scheduler io flow cfg
         incr flushes);
       (if (not !got_ready) || not no_done then (
        Log.debug (fun m -> m "Negotiation is done!");
-       Smart_flow.run scheduler raise io flow Smart.(recv ctx shallows)
+       State_flow.run scheduler raise Smart.pp_error io flow
+         Smart.(recv ctx shallows)
        >>= fun _shallows -> return ())
       else return ())
       >>= fun () ->
       let rec go () =
         if !flushes > 0 || cfg.multi_ack = `Some || cfg.multi_ack = `Detailed
         then (
-          Smart_flow.run scheduler raise io flow Smart.(recv ctx ack)
+          State_flow.run scheduler raise Smart.pp_error io flow
+            Smart.(recv ctx ack)
           >>| Smart.Negotiation.map ~f:of_hex
           >>= fun ack ->
           match ack with
diff --git a/src/not-so-smart/push.ml b/src/not-so-smart/push.ml
index 7d0b56666..aa6264408 100644
--- a/src/not-so-smart/push.ml
+++ b/src/not-so-smart/push.ml
@@ -39,8 +39,6 @@ struct
         pp_error = Flow.pp_error;
       }
 
-  module Smart_flow = State_flow.Make (Smart)
-
   let push ?(uses_git_transport = true) ~capabilities:client_caps cmds ~host
       path flow store access push_cfg pack =
     let fiber ctx =
@@ -57,7 +55,7 @@ struct
       return (Smart.Advertised_refs.map ~fuid:Uid.of_hex ~fref:Ref.v v)
     in
     let ctx = Smart.Context.make ~client_caps in
-    Smart_flow.run sched fail io flow (fiber ctx) |> prj
+    State_flow.run sched fail Smart.pp_error io flow (fiber ctx) |> prj
     >>= fun advertised_refs ->
     Pck.commands sched
       ~capabilities:(Smart.Advertised_refs.capabilities advertised_refs)
@@ -66,10 +64,12 @@ struct
     |> prj
     >>= function
     | None ->
-        Smart_flow.run sched fail io flow Smart.(send ctx flush ()) |> prj
+        State_flow.run sched fail Smart.pp_error io flow
+          Smart.(send ctx flush ())
+        |> prj
         >>= fun () -> return ()
     | Some cmds -> (
-        Smart_flow.run sched fail io flow
+        State_flow.run sched fail Smart.pp_error io flow
           Smart.(
             send ctx commands
               (Commands.map ~fuid:Uid.to_hex ~fref:Ref.to_string cmds))
@@ -101,14 +101,16 @@ struct
               Log.debug (fun m ->
                   m "report-status capability: %b." report_status);
               if report_status then
-                Smart_flow.run sched fail io flow Smart.(recv ctx status)
+                State_flow.run sched fail Smart.pp_error io flow
+                  Smart.(recv ctx status)
                 |> prj
                 >>| Smart.Status.map ~f:Ref.v
               else
                 let cmds = List.map R.ok (Smart.Commands.commands cmds) in
                 return (Smart.Status.v cmds)
           | Some payload ->
-              Smart_flow.run sched fail io flow Smart.(send ctx pack payload)
+              State_flow.run sched fail Smart.pp_error io flow
+                Smart.(send ctx pack payload)
               |> prj
               >>= fun () -> go ()
         in
diff --git a/src/not-so-smart/smart.ml b/src/not-so-smart/smart.ml
index b462d549b..4b5690111 100644
--- a/src/not-so-smart/smart.ml
+++ b/src/not-so-smart/smart.ml
@@ -50,6 +50,10 @@ module Value = struct
 
   type error = [ Protocol.Encoder.error | Protocol.Decoder.error ]
 
+  let pp_error ppf = function
+    | #Protocol.Encoder.error as err -> Protocol.Encoder.pp_error ppf err
+    | #Protocol.Decoder.error as err -> Protocol.Decoder.pp_error ppf err
+
   let encode :
       type a. encoder -> a send -> a -> (unit, [> Encoder.error ]) State.t =
    fun encoder w v ->
@@ -137,10 +141,6 @@ let send_advertised_refs : _ send = Advertised_refs
 
 include State.Scheduler (Value)
 
-let pp_error ppf = function
-  | #Protocol.Encoder.error as err -> Protocol.Encoder.pp_error ppf err
-  | #Protocol.Decoder.error as err -> Protocol.Decoder.pp_error ppf err
-
 module Unsafe = struct
   let write context packet =
     let encoder = Context.encoder context in
diff --git a/src/not-so-smart/state.ml b/src/not-so-smart/state.ml
index 371e23776..231ba7249 100644
--- a/src/not-so-smart/state.ml
+++ b/src/not-so-smart/state.ml
@@ -29,6 +29,7 @@ module type VALUE = sig
   type encoder
   type decoder
 
+  val pp_error : error Fmt.t
   val encode : encoder -> 'a send -> 'a -> (unit, error) t
   val decode : decoder -> 'a recv -> ('a, error) t
 end
@@ -77,6 +78,8 @@ module Scheduler
 struct
   type error = Value.error
 
+  let pp_error = Value.pp_error
+
   let bind : ('a, 'err) t -> f:('a -> ('b, 'err) t) -> ('b, 'err) t =
     let rec bind' m ~f =
       match m with
diff --git a/src/not-so-smart/state.mli b/src/not-so-smart/state.mli
index 9b382edbf..e864d2bfc 100644
--- a/src/not-so-smart/state.mli
+++ b/src/not-so-smart/state.mli
@@ -28,6 +28,7 @@ module type VALUE = sig
   type encoder
   type decoder
 
+  val pp_error : error Fmt.t
   val encode : encoder -> 'a send -> 'a -> (unit, error) t
   val decode : decoder -> 'a recv -> ('a, error) t
 end
@@ -57,6 +58,7 @@ module Scheduler
                 and type decoder = Context.decoder) : sig
   type error = Value.error
 
+  val pp_error : error Fmt.t
   val return : 'v -> ('v, 'err) t
   val bind : ('a, 'err) t -> f:('a -> ('b, 'err) t) -> ('b, 'err) t
   val ( >>= ) : ('a, 'err) t -> ('a -> ('b, 'err) t) -> ('b, 'err) t
diff --git a/src/not-so-smart/state_flow.ml b/src/not-so-smart/state_flow.ml
index a9bb6ef67..f32ac3796 100644
--- a/src/not-so-smart/state_flow.ml
+++ b/src/not-so-smart/state_flow.ml
@@ -7,70 +7,60 @@ let io_buffer_size = 65536
 
 type ('a, 's) raise = exn -> ('a, 's) io
 
-module Make (Read_write : sig
-  type ('a, 'err) t = ('a, 'err) State.t
-  type error
+let run :
+    type fl s err.
+    s scheduler ->
+    ('a, s) raise ->
+    err Fmt.t ->
+    (fl, 'error, s) flow ->
+    fl ->
+    ('res, [ `Protocol of err ]) State.t ->
+    ('res, s) io =
+ fun scheduler io_raise pp_error flow_ops flow state ->
+  let { bind; return } = scheduler in
+  let ( >>= ) = bind in
 
-  val pp_error : error Fmt.t
-end) =
-struct
-  type nonrec error = Read_write.error
+  let failwithf fmt =
+    Format.kasprintf (fun err -> io_raise (Failure err)) fmt
+  in
 
-  let run :
-      type fl s.
-      s scheduler ->
-      ('a, s) raise ->
-      (fl, 'error, s) flow ->
-      fl ->
-      ('res, [ `Protocol of error ]) Read_write.t ->
-      ('res, s) io =
-   fun scheduler io_raise flow_ops flow state ->
-    let { bind; return } = scheduler in
-    let ( >>= ) = bind in
+  let cbuff = Cstruct.create io_buffer_size in
 
-    let failwithf fmt =
-      Format.kasprintf (fun err -> io_raise (Failure err)) fmt
-    in
+  let rec unwrap = function
+    | State.Return v ->
+        Log.debug (fun m -> m "got return ");
+        return v
+    | Error (`Protocol err) ->
+        Log.err (fun m -> m "Got a protocol error: %a." pp_error err);
+        failwithf "%a" pp_error err
+    | Read { k; buffer; off; len; eof } -> (
+        let rd_n_bytes = min (Cstruct.len cbuff) len in
+        Log.debug (fun m -> m "Start to read %d byte(s)." rd_n_bytes);
+        flow_ops.recv flow (Cstruct.sub cbuff 0 rd_n_bytes) >>= function
+        | Ok `End_of_flow ->
+            Log.debug (fun m -> m "Got end of input.");
+            unwrap (eof ())
+        | Ok (`Input len) ->
+            Log.debug (fun m -> m "Got %d/%d byte(s)." len rd_n_bytes);
+            Cstruct.blit_to_bytes cbuff 0 buffer off len;
+            unwrap (k len)
+        | Error err ->
+            Log.err (fun m -> m "Got an error: %a." flow_ops.pp_error err);
+            failwithf "%a" flow_ops.pp_error err)
+    | Write { k; buffer; off; len } ->
+        (* TODO: almost always we can write in one go instead of calling a loop,
+                 so we should try writing and call loop if we aren't done *)
+        let rec loop tmp =
+          if Cstruct.is_empty tmp then unwrap (k len)
+          else
+            flow_ops.send flow tmp >>= function
+            | Ok shift ->
+                Log.debug (fun m ->
+                    m "Wrote %d byte(s). %s" shift (Cstruct.to_string tmp));
+                loop (Cstruct.shift tmp shift)
+            | Error err -> failwithf "%a" flow_ops.pp_error err
+        in
+        Cstruct.of_string buffer ~off ~len |> loop
+  in
 
-    let cbuff = Cstruct.create io_buffer_size in
-
-    let rec unwrap = function
-      | State.Return v ->
-          Log.debug (fun m -> m "got return ");
-          return v
-      | Error (`Protocol err) ->
-          Log.err (fun m ->
-              m "Got a protocol error: %a." Read_write.pp_error err);
-          failwithf "%a" Read_write.pp_error err
-      | Read { k; buffer; off; len; eof } -> (
-          let rd_n_bytes = min (Cstruct.len cbuff) len in
-          Log.debug (fun m -> m "Start to read %d byte(s)." rd_n_bytes);
-          flow_ops.recv flow (Cstruct.sub cbuff 0 rd_n_bytes) >>= function
-          | Ok `End_of_flow ->
-              Log.debug (fun m -> m "Got end of input.");
-              unwrap (eof ())
-          | Ok (`Input len) ->
-              Log.debug (fun m -> m "Got %d/%d byte(s)." len rd_n_bytes);
-              Cstruct.blit_to_bytes cbuff 0 buffer off len;
-              unwrap (k len)
-          | Error err ->
-              Log.err (fun m -> m "Got an error: %a." flow_ops.pp_error err);
-              failwithf "%a" flow_ops.pp_error err)
-      | Write { k; buffer; off; len } ->
-          (* TODO: almost always we can write in one go instead of calling a loop,
-                   so we should try writing and call loop if we aren't done *)
-          let rec loop tmp =
-            if Cstruct.is_empty tmp then unwrap (k len)
-            else
-              flow_ops.send flow tmp >>= function
-              | Ok shift ->
-                  Log.debug (fun m ->
-                      m "Wrote %d byte(s). %s" shift (Cstruct.to_string tmp));
-                  loop (Cstruct.shift tmp shift)
-              | Error err -> failwithf "%a" flow_ops.pp_error err
-          in
-          Cstruct.of_string buffer ~off ~len |> loop
-    in
-
-    unwrap state
-end
+  unwrap state
diff --git a/src/not-so-smart/state_flow.mli b/src/not-so-smart/state_flow.mli
index bab268386..75e05f2ea 100644
--- a/src/not-so-smart/state_flow.mli
+++ b/src/not-so-smart/state_flow.mli
@@ -4,21 +4,11 @@ val io_buffer_size : int
 
 type ('a, 's) raise = exn -> ('a, 's) Sigs.io
 
-module Make : functor
-  (Read_write : sig
-     type ('a, 'err) t = ('a, 'err) State.t
-     type error
-
-     val pp_error : error Fmt.t
-   end)
-  -> sig
-  type nonrec error = Read_write.error
-
-  val run :
-    's Sigs.scheduler ->
-    ('res, 's) raise ->
-    ('fl, 'error, 's) Sigs.flow ->
-    'fl ->
-    ('res, [ `Protocol of error ]) State.t ->
-    ('res, 's) Sigs.io
-end
+val run :
+  's Sigs.scheduler ->
+  ('res, 's) raise ->
+  'err Fmt.t ->
+  ('fl, 'error, 's) Sigs.flow ->
+  'fl ->
+  ('res, [ `Protocol of 'err ]) State.t ->
+  ('res, 's) Sigs.io
diff --git a/src/not-so-smart/wire_proto_v2.ml b/src/not-so-smart/wire_proto_v2.ml
index 0fa3c7063..691ade9bb 100644
--- a/src/not-so-smart/wire_proto_v2.ml
+++ b/src/not-so-smart/wire_proto_v2.ml
@@ -38,6 +38,12 @@ module Value = struct
   type encoder = Pkt_line.Encoder.encoder
   type decoder = Pkt_line.Decoder.decoder
 
+  let pp_error ppf = function
+    | #Proto_vals_v2.Encoder.error as err ->
+        Proto_vals_v2.Encoder.pp_error ppf err
+    | #Proto_vals_v2.Decoder.error as err ->
+        Proto_vals_v2.Decoder.pp_error ppf err
+
   let encode : type a. encoder -> a send -> a -> (unit, error) State.t =
    fun encoder w v ->
     let encoder_state =
@@ -78,9 +84,3 @@ module Value = struct
 end
 
 include State.Scheduler (Value)
-
-let pp_error ppf = function
-  | #Proto_vals_v2.Encoder.error as err ->
-      Proto_vals_v2.Encoder.pp_error ppf err
-  | #Proto_vals_v2.Decoder.error as err ->
-      Proto_vals_v2.Decoder.pp_error ppf err