diff --git a/src/proto_alpha/bin_sc_rollup_node/context.ml b/src/proto_alpha/bin_sc_rollup_node/context.ml
index d1093b01c8b1eb7ccc30406af260fabb87b9e561..d4ff0301ba5143104bbea8d979122a5c0324e83f 100644
--- a/src/proto_alpha/bin_sc_rollup_node/context.ml
+++ b/src/proto_alpha/bin_sc_rollup_node/context.ml
@@ -175,6 +175,7 @@ end
 
 module Inbox = struct
   include Sc_rollup.Inbox
+  module Message = Sc_rollup.Inbox_message
 
   include Sc_rollup.Inbox.Make_hashing_scheme (struct
     include
diff --git a/src/proto_alpha/bin_sc_rollup_node/context.mli b/src/proto_alpha/bin_sc_rollup_node/context.mli
index ae3cd8e94fd59b0d77a3306ce9d6581272ad2622..5e9aa163dd268185f39807fe0860430f8309a285 100644
--- a/src/proto_alpha/bin_sc_rollup_node/context.mli
+++ b/src/proto_alpha/bin_sc_rollup_node/context.mli
@@ -146,7 +146,7 @@ end
 module Inbox : sig
   type t = Sc_rollup.Inbox.t
 
-  module Message : module type of Sc_rollup.Inbox.Message
+  module Message : module type of Sc_rollup.Inbox_message
 
   val pp : Format.formatter -> t -> unit
 
diff --git a/src/proto_alpha/bin_sc_rollup_node/inbox.ml b/src/proto_alpha/bin_sc_rollup_node/inbox.ml
index 65eb6bd66be222dbaef9abd74462e59a3a82fa8d..31f3f208cfe86070922bf46cd70d495bc69f98d5 100644
--- a/src/proto_alpha/bin_sc_rollup_node/inbox.ml
+++ b/src/proto_alpha/bin_sc_rollup_node/inbox.ml
@@ -114,7 +114,7 @@ let get_messages Node_context.{l1_ctxt; rollup_address; _} head =
       when Sc_rollup.Address.(rollup = rollup_address) ->
         let messages =
           List.map
-            (fun message -> Sc_rollup.Inbox.Message.External message)
+            (fun message -> Sc_rollup.Inbox_message.External message)
             messages
         in
         List.rev_append messages accu
@@ -137,8 +137,8 @@ let get_messages Node_context.{l1_ctxt; rollup_address; _} head =
         let+ payload =
           Environment.wrap_tzresult @@ Script_repr.force_decode parameters
         in
-        let message = Sc_rollup.Inbox.Message.{payload; sender; source} in
-        Sc_rollup.Inbox.Message.Internal message :: accu
+        let message = Sc_rollup.Inbox_message.{payload; sender; source} in
+        Sc_rollup.Inbox_message.Internal message :: accu
     | _ -> return accu
   in
   let*? messages =
@@ -194,7 +194,7 @@ let process_head node_ctxt Layer1.(Head {level; hash = head_hash} as head) =
         lift
         @@ let*? level = Raw_level.of_int32 level in
            let*? messages =
-             List.map_e Sc_rollup.Inbox.Message.serialize messages
+             List.map_e Sc_rollup.Inbox_message.serialize messages
            in
            if messages = [] then return (history, inbox, ctxt)
            else
diff --git a/src/proto_alpha/bin_sc_rollup_node/interpreter.ml b/src/proto_alpha/bin_sc_rollup_node/interpreter.ml
index 6ebad14c0cb80f7022d7e8dd77663c529a3a5dc4..76e058a80523e2faac086888d89c810494f24430 100644
--- a/src/proto_alpha/bin_sc_rollup_node/interpreter.ml
+++ b/src/proto_alpha/bin_sc_rollup_node/interpreter.ml
@@ -106,7 +106,7 @@ module Make (PVM : Pvm.S) : S with module PVM = PVM = struct
 
   (** [mutate input] corrupts the payload of [input] for testing purposes. *)
   let mutate input =
-    let payload = Inbox.Message.unsafe_of_string "0xC4C4" in
+    let payload = Sc_rollup.Inbox_message.unsafe_of_string "0xC4C4" in
     {input with Sc_rollup.payload}
 
   (** [feed_input level message_index ~fuel ~failing_ticks state
@@ -163,7 +163,7 @@ module Make (PVM : Pvm.S) : S with module PVM = PVM = struct
           List.fold_left_i_es
             (fun message_counter (state, fuel) message ->
               let*? payload =
-                Sc_rollup.Inbox.Message.(
+                Sc_rollup.Inbox_message.(
                   message |> serialize |> Environment.wrap_tzresult)
               in
               let input =
diff --git a/src/proto_alpha/bin_sc_rollup_node/store.ml b/src/proto_alpha/bin_sc_rollup_node/store.ml
index 2aab02f4ac21e8fa7b49fe8298d3b1c0bfb20992..8670a2dfe964e9006f2dc5a4c6e315b580aa9792 100644
--- a/src/proto_alpha/bin_sc_rollup_node/store.ml
+++ b/src/proto_alpha/bin_sc_rollup_node/store.ml
@@ -293,10 +293,10 @@ module Messages = Make_append_only_map (struct
 
   let string_of_key = Block_hash.to_b58check
 
-  type value = Sc_rollup.Inbox.Message.t list
+  type value = Sc_rollup.Inbox_message.t list
 
   let value_encoding =
-    Data_encoding.(list @@ dynamic_size Sc_rollup.Inbox.Message.encoding)
+    Data_encoding.(list @@ dynamic_size Sc_rollup.Inbox_message.encoding)
 end)
 
 (** Inbox state for each block *)
diff --git a/src/proto_alpha/lib_protocol/alpha_context.ml b/src/proto_alpha/lib_protocol/alpha_context.ml
index 43d36fd849f9991200c281e2d0beec2574367658..92decb272643ab93e20339653d7bb7419ba11163 100644
--- a/src/proto_alpha/lib_protocol/alpha_context.ml
+++ b/src/proto_alpha/lib_protocol/alpha_context.ml
@@ -59,11 +59,11 @@ module Sc_rollup = struct
   include Sc_rollup_PVM_sig
   module ArithPVM = Sc_rollup_arith
   module Wasm_2_0_0PVM = Sc_rollup_wasm.V2_0_0
+  module Inbox_message = Sc_rollup_inbox_message_repr
 
   module Inbox = struct
     include Sc_rollup_inbox_repr
     include Sc_rollup_inbox_storage
-    module Message = Sc_rollup_inbox_message_repr
 
     module Internal_for_tests = struct
       include Sc_rollup_inbox_repr.Internal_for_tests
diff --git a/src/proto_alpha/lib_protocol/alpha_context.mli b/src/proto_alpha/lib_protocol/alpha_context.mli
index 988d6ad409905fe30f89e87bb5320c27e669e39d..48b4e04fb96b8c67c620b6bdfa615dfd05d076ce 100644
--- a/src/proto_alpha/lib_protocol/alpha_context.mli
+++ b/src/proto_alpha/lib_protocol/alpha_context.mli
@@ -2917,29 +2917,48 @@ module Sc_rollup : sig
     val hash_string : unreachable -> t
   end
 
-  module Inbox : sig
-    type t
+  (** See {!Sc_rollup_inbox_message_repr}. *)
+  module Inbox_message : sig
+    type internal_inbox_message = {
+      payload : Script.expr;
+      sender : Contract_hash.t;
+      source : public_key_hash;
+    }
 
-    (** See {!Sc_rollup_inbox_message_repr}. *)
-    module Message : sig
-      type internal_inbox_message = {
-        payload : Script.expr;
-        sender : Contract_hash.t;
-        source : public_key_hash;
-      }
+    type t = Internal of internal_inbox_message | External of string
 
-      type t = Internal of internal_inbox_message | External of string
+    type serialized = private string
 
-      type serialized = private string
+    val encoding : t Data_encoding.t
 
-      val encoding : t Data_encoding.t
+    val unsafe_of_string : string -> serialized
 
-      val unsafe_of_string : string -> serialized
+    val serialize : t -> serialized tzresult
 
-      val serialize : t -> serialized tzresult
+    val deserialize : serialized -> t tzresult
+  end
 
-      val deserialize : serialized -> t tzresult
-    end
+  type input = {
+    inbox_level : Raw_level.t;
+    message_counter : Z.t;
+    payload : Inbox_message.serialized;
+  }
+
+  val input_equal : input -> input -> bool
+
+  val input_encoding : input Data_encoding.t
+
+  type input_request =
+    | No_input_required
+    | Initial
+    | First_after of Raw_level.t * Z.t
+
+  val input_request_encoding : input_request Data_encoding.t
+
+  val input_request_equal : input_request -> input_request -> bool
+
+  module Inbox : sig
+    type t
 
     val pp : Format.formatter -> t -> unit
 
@@ -2985,7 +3004,7 @@ module Sc_rollup : sig
         History.t ->
         t ->
         Raw_level.t ->
-        Message.serialized list ->
+        Inbox_message.serialized list ->
         tree option ->
         (tree * History.t * t) tzresult Lwt.t
 
@@ -2993,12 +3012,12 @@ module Sc_rollup : sig
         inbox_context ->
         t ->
         Raw_level.t ->
-        Message.serialized list ->
+        Inbox_message.serialized list ->
         tree option ->
         (tree * t) tzresult Lwt.t
 
       val get_message_payload :
-        tree -> Z.t -> Sc_rollup_inbox_message_repr.serialized option Lwt.t
+        tree -> Z.t -> Inbox_message.serialized option Lwt.t
 
       val form_history_proof :
         inbox_context ->
@@ -3032,18 +3051,17 @@ module Sc_rollup : sig
         Raw_level.t * Z.t ->
         history_proof ->
         proof ->
-        Sc_rollup_PVM_sig.input option tzresult Lwt.t
+        input option tzresult Lwt.t
 
       val produce_proof :
         inbox_context ->
         History.t ->
         history_proof ->
         Raw_level.t * Z.t ->
-        (proof * Sc_rollup_PVM_sig.input option) tzresult Lwt.t
+        (proof * input option) tzresult Lwt.t
 
       val empty : inbox_context -> Sc_rollup_repr.t -> Raw_level.t -> t Lwt.t
 
-      (*xx*)
       module Internal_for_tests : sig
         val eq_tree : tree -> tree -> bool
 
@@ -3105,25 +3123,6 @@ module Sc_rollup : sig
     val inbox : context -> rollup -> (t * context) tzresult Lwt.t
   end
 
-  type input = {
-    inbox_level : Raw_level.t;
-    message_counter : Z.t;
-    payload : Inbox.Message.serialized;
-  }
-
-  val input_equal : input -> input -> bool
-
-  val input_encoding : input Data_encoding.t
-
-  type input_request =
-    | No_input_required
-    | Initial
-    | First_after of Raw_level.t * Z.t
-
-  val input_request_encoding : input_request Data_encoding.t
-
-  val input_request_equal : input_request -> input_request -> bool
-
   module Outbox : sig
     (** See {!Sc_rollup_outbox_message_repr}. *)
     module Message : sig
@@ -3457,7 +3456,7 @@ module Sc_rollup : sig
       Raw_level.t ->
       pvm_name:string ->
       t ->
-      (bool * Sc_rollup_PVM_sig.input option) tzresult Lwt.t
+      (bool * input option) tzresult Lwt.t
 
     val produce :
       (module PVM_with_context_and_state) -> Raw_level.t -> t tzresult Lwt.t
diff --git a/src/proto_alpha/lib_protocol/sc_rollup_management_protocol.ml b/src/proto_alpha/lib_protocol/sc_rollup_management_protocol.ml
index 0118f102407fc71f992819d0e83883186a2635bc..575a60114f3e226d5d82d54d0ff53b1b6c34e5d0 100644
--- a/src/proto_alpha/lib_protocol/sc_rollup_management_protocol.ml
+++ b/src/proto_alpha/lib_protocol/sc_rollup_management_protocol.ml
@@ -64,7 +64,7 @@ let make_internal_inbox_message ctxt ty ~payload ~sender ~source =
       payload
   in
   let payload = Micheline.strip_locations payload in
-  (Sc_rollup.Inbox.Message.Internal {payload; sender; source}, ctxt)
+  (Sc_rollup.Inbox_message.Internal {payload; sender; source}, ctxt)
 
 let transactions_batch_of_internal ctxt transactions =
   let open Lwt_tzresult_syntax in
@@ -167,5 +167,5 @@ module Internal_for_tests = struct
     Sc_rollup.Outbox.Message.Internal_for_tests.serialize
       output_message_internal
 
-  let deserialize_inbox_message = Sc_rollup.Inbox.Message.deserialize
+  let deserialize_inbox_message = Sc_rollup.Inbox_message.deserialize
 end
diff --git a/src/proto_alpha/lib_protocol/sc_rollup_management_protocol.mli b/src/proto_alpha/lib_protocol/sc_rollup_management_protocol.mli
index 688fd402cd86a99f90f5a3fbf931069d7d56610c..817068a8a2208c24b077d61ba6b9d3075d7acfd9 100644
--- a/src/proto_alpha/lib_protocol/sc_rollup_management_protocol.mli
+++ b/src/proto_alpha/lib_protocol/sc_rollup_management_protocol.mli
@@ -69,7 +69,7 @@ val make_internal_inbox_message :
   payload:'a ->
   sender:Contract_hash.t ->
   source:public_key_hash ->
-  (Sc_rollup.Inbox.Message.t * context) tzresult Lwt.t
+  (Sc_rollup.Inbox_message.t * context) tzresult Lwt.t
 
 (** [outbox_message_of_outbox_message_repr ctxt msg] returns a typed version of
     of the given outbox message [msg].
@@ -108,5 +108,5 @@ module Internal_for_tests : sig
   (** [deserialize_inbox_message bs] decodes an inbox message from the given data
       [bs]. *)
   val deserialize_inbox_message :
-    Sc_rollup.Inbox.Message.serialized -> Sc_rollup.Inbox.Message.t tzresult
+    Sc_rollup.Inbox_message.serialized -> Sc_rollup.Inbox_message.t tzresult
 end
diff --git a/src/proto_alpha/lib_protocol/test/integration/test_sc_rollup_wasm.ml b/src/proto_alpha/lib_protocol/test/integration/test_sc_rollup_wasm.ml
index 02f3faa28eb1d1ac51d3b153ed6799b46ec06596..a56433f603b7b0e5650fff85882aa084acb227a8 100644
--- a/src/proto_alpha/lib_protocol/test/integration/test_sc_rollup_wasm.ml
+++ b/src/proto_alpha/lib_protocol/test/integration/test_sc_rollup_wasm.ml
@@ -237,7 +237,7 @@ let should_boot_complete_boot_sector boot_sector () =
   return_unit
 
 let arbitrary_input i payload =
-  match Sc_rollup.Inbox.Message.serialize (External payload) with
+  match Sc_rollup.Inbox_message.serialize (External payload) with
   | Ok payload ->
       Sc_rollup.
         {
diff --git a/src/proto_alpha/lib_protocol/test/pbt/test_refutation_game.ml b/src/proto_alpha/lib_protocol/test/pbt/test_refutation_game.ml
index 795bc63b1510abfcc06daf04355aa2fba18b4aa9..d111bd4599319cd359eb895170b6ae04865a68a2 100644
--- a/src/proto_alpha/lib_protocol/test/pbt/test_refutation_game.ml
+++ b/src/proto_alpha/lib_protocol/test/pbt/test_refutation_game.ml
@@ -65,7 +65,7 @@ let number_of_ticks_of_int64_exn ?(__LOC__ = __LOC__) n =
 let make_external_inbox_message str =
   WithExceptions.Result.get_ok
     ~loc:__LOC__
-    Inbox.Message.(External str |> serialize)
+    Inbox_message.(External str |> serialize)
 
 let game_status_of_refute_op_result = function
   | [
diff --git a/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_management_protocol.ml b/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_management_protocol.ml
index 5cd6c391bd54fdfdbfcbf718260ccf8cc8324e63..186f88bb2f884b49ba14994a0a7dcb263eae0fdc 100644
--- a/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_management_protocol.ml
+++ b/src/proto_alpha/lib_protocol/test/unit/test_sc_rollup_management_protocol.ml
@@ -40,14 +40,14 @@ let check_encode_decode_inbox_message message =
   let open Lwt_result_syntax in
   let open Sc_rollup_management_protocol in
   let*? bytes =
-    Environment.wrap_tzresult @@ Sc_rollup.Inbox.Message.serialize message
+    Environment.wrap_tzresult @@ Sc_rollup.Inbox_message.serialize message
   in
   let*? message' =
     Environment.wrap_tzresult
     @@ Internal_for_tests.deserialize_inbox_message bytes
   in
   let*? bytes' =
-    Environment.wrap_tzresult @@ Sc_rollup.Inbox.Message.serialize message'
+    Environment.wrap_tzresult @@ Sc_rollup.Inbox_message.serialize message'
   in
   Assert.equal_string ~loc:__LOC__ (bytes :> string) (bytes' :> string)
 
@@ -144,10 +144,10 @@ let test_encode_decode_internal_inbox_message () =
 let test_encode_decode_external_inbox_message () =
   let open Lwt_result_syntax in
   let assert_prefix message =
-    let inbox_message = Sc_rollup.Inbox.Message.External message in
+    let inbox_message = Sc_rollup.Inbox_message.External message in
     let*? real_encoding =
       Environment.wrap_tzresult
-      @@ Sc_rollup.Inbox.Message.serialize inbox_message
+      @@ Sc_rollup.Inbox_message.serialize inbox_message
     in
     let real_encoding = (real_encoding :> string) in
     (* The prefix consists of a tag (0 for internal, 1 for external). *)
@@ -167,7 +167,7 @@ let test_encode_decode_external_inbox_message () =
   let* () = assert_prefix "0123456789" in
   let* () = assert_prefix (String.init 256 (Fun.const 'A')) in
   let assert_encoding_failure message =
-    let inbox_message = Sc_rollup.Inbox.Message.External message in
+    let inbox_message = Sc_rollup.Inbox_message.External message in
     let*! res = check_encode_decode_inbox_message inbox_message in
     assert_encoding_failure ~loc:__LOC__ res
   in