diff --git a/manifest/main.ml b/manifest/main.ml
index a474d07dbf3a925712da790ebef285031b13439f..260064f7093306e18e160b9a8e18080102799f63 100644
--- a/manifest/main.ml
+++ b/manifest/main.ml
@@ -4068,9 +4068,7 @@ let octez_crawler =
     ~synopsis:"Octez: library to crawl blocks of the L1 chain"
     ~deps:
       [
-        octez_base |> open_ ~m:"TzPervasives"
-        |> open_ ~m:"TzPervasives.Error_monad.Legacy_monad_globals"
-        |> open_;
+        octez_base |> open_ ~m:"TzPervasives" |> open_;
         octez_rpc_http |> open_;
         octez_base_unix;
         octez_stdlib_unix |> open_;
@@ -4085,9 +4083,7 @@ let octez_injector =
     ~synopsis:"Octez: library for building injectors"
     ~deps:
       [
-        octez_base |> open_ ~m:"TzPervasives"
-        |> open_ ~m:"TzPervasives.Error_monad.Legacy_monad_globals"
-        |> open_;
+        octez_base |> open_ ~m:"TzPervasives" |> open_;
         logs_lwt;
         octez_base_unix;
         octez_stdlib_unix |> open_;
@@ -4106,9 +4102,7 @@ let octez_smart_rollup_lib =
     ~synopsis:"Octez: library for Smart Rollups "
     ~deps:
       [
-        octez_base |> open_ ~m:"TzPervasives"
-        |> open_ ~m:"TzPervasives.Error_monad.Legacy_monad_globals"
-        |> open_;
+        octez_base |> open_ ~m:"TzPervasives" |> open_;
         octez_base_unix;
         octez_stdlib_unix |> open_;
         octez_crypto |> open_;
@@ -7478,8 +7472,7 @@ let octez_scoru_sequencer =
     ~synopsis:"Sequencer library for smart contract rollup"
     ~deps:
       [
-        octez_base |> open_ |> open_ ~m:"TzPervasives"
-        |> open_ ~m:"TzPervasives.Error_monad.Legacy_monad_globals";
+        octez_base |> open_ |> open_ ~m:"TzPervasives";
         Protocol.(octez_sc_rollup_layer2 alpha |> if_some |> open_);
         Protocol.(main alpha) |> open_;
         Protocol.(octez_sc_rollup_node alpha) |> if_some;
@@ -7519,8 +7512,7 @@ let _sc_sequencer_node =
     ~with_macos_security_framework:true
     ~deps:
       [
-        octez_base |> open_ |> open_ ~m:"TzPervasives"
-        |> open_ ~m:"TzPervasives.Error_monad.Legacy_monad_globals";
+        octez_base |> open_ |> open_ ~m:"TzPervasives";
         octez_clic;
         octez_client_base |> open_;
         octez_client_base_unix |> open_;
diff --git a/src/bin_sequencer_node/dune b/src/bin_sequencer_node/dune
index 270c52c4dee1068f592b81572ad4d6a0625c6991..ab8b306e86307b5d4da7e2f9f23d9552ed180949 100644
--- a/src/bin_sequencer_node/dune
+++ b/src/bin_sequencer_node/dune
@@ -24,7 +24,6 @@
   (:standard)
   -open Tezos_base
   -open Tezos_base.TzPervasives
-  -open Tezos_base.TzPervasives.Error_monad.Legacy_monad_globals
   -open Tezos_client_base
   -open Tezos_client_base_unix
   -open Tezos_client_commands
diff --git a/src/lib_crawler/dune b/src/lib_crawler/dune
index 44d5460e39f36d944438dd11b237da43bc5e9c5d..cb6d0801041044021f9eb67d701e84030bcd3342 100644
--- a/src/lib_crawler/dune
+++ b/src/lib_crawler/dune
@@ -15,7 +15,6 @@
  (flags
   (:standard)
   -open Tezos_base.TzPervasives
-  -open Tezos_base.TzPervasives.Error_monad.Legacy_monad_globals
   -open Tezos_base
   -open Tezos_rpc_http
   -open Tezos_stdlib_unix
diff --git a/src/lib_crawler/layer_1.ml b/src/lib_crawler/layer_1.ml
index 518f2a1dd736867f39504fcd0767de483168d829..c508589f1dacba4a61ac1bdcbfa6b2ccbb498531 100644
--- a/src/lib_crawler/layer_1.ml
+++ b/src/lib_crawler/layer_1.ml
@@ -177,7 +177,7 @@ let iter_heads l1_ctxt f =
   in
   Lwt.catch
     (fun () -> Lwt.no_cancel @@ loop l1_ctxt)
-    (function Iter_error e -> Lwt.return_error e | exn -> fail (Exn exn))
+    (function Iter_error e -> Lwt.return_error e | exn -> fail_with_exn exn)
 
 let wait_first l1_ctxt =
   let rec loop l1_ctxt =
diff --git a/src/lib_injector/disk_persistence.ml b/src/lib_injector/disk_persistence.ml
index 200a04899376a28419b2754b3b77eff9bb950814..e5f8089697b1fd922a700ee511d87a0af46bfdcd 100644
--- a/src/lib_injector/disk_persistence.ml
+++ b/src/lib_injector/disk_persistence.ml
@@ -151,28 +151,29 @@ let create_dir dir =
   return_unit
 
 let read_value file encoding =
-  let open Lwt_syntax in
+  let open Lwt_result_syntax in
   trace (Cannot_read_file file)
   @@ Lwt.catch
        (fun () ->
          Lwt_io.with_file ~flags:[Unix.O_RDONLY; O_CLOEXEC] ~mode:Input file
          @@ fun channel ->
-         let+ bytes = Lwt_io.read channel in
-         Result.map_error (fun e -> [Decoding_error e])
-         @@ Data_encoding.Binary.of_bytes
-              encoding
-              (Bytes.unsafe_of_string bytes))
+         let*! bytes = Lwt_io.read channel in
+         let*? v =
+           Result.map_error (fun e -> [Decoding_error e])
+           @@ Data_encoding.Binary.of_bytes
+                encoding
+                (Bytes.unsafe_of_string bytes)
+         in
+         return v)
        (function
-         | Unix.Unix_error (e, _, _) -> fail (Unix_error e) | e -> fail (Exn e))
+         | Unix.Unix_error (e, _, _) -> tzfail (Unix_error e)
+         | e -> fail_with_exn e)
 
 let maybe_read_value ~warn file encoding =
   let open Lwt_syntax in
   let* v = read_value file encoding in
-  match v with
-  | Error e ->
-      let+ () = warn file e in
-      None
-  | Ok v -> return_some v
+  let* () = Result.iter_error_s (warn file) v in
+  return (Result.to_option v)
 
 let write_value file encoding value =
   trace (Cannot_write_file file)
diff --git a/src/lib_injector/dune b/src/lib_injector/dune
index 29183b8723669486bef56517cd5e2a63e4b99ed9..35314fb771bfacbbdfaa8990b179eea575d6d480 100644
--- a/src/lib_injector/dune
+++ b/src/lib_injector/dune
@@ -19,7 +19,6 @@
  (flags
   (:standard)
   -open Tezos_base.TzPervasives
-  -open Tezos_base.TzPervasives.Error_monad.Legacy_monad_globals
   -open Tezos_base
   -open Tezos_stdlib_unix
   -open Tezos_micheline
diff --git a/src/lib_injector/injector_functor.ml b/src/lib_injector/injector_functor.ml
index 2aa820d2f7a7942a9553aec5990578d74b0d9eef..24e84da0da50b3c38749a477f038e3f706a2f3cc 100644
--- a/src/lib_injector/injector_functor.ml
+++ b/src/lib_injector/injector_functor.ml
@@ -692,11 +692,12 @@ module Make (Parameters : PARAMETERS) = struct
         state.signer.sk
         Unsigned_op.value
     in
-    Tezos_shell_services.Shell_services.Injection.operation
-      state.cctxt
-      ~chain:state.cctxt#chain
-      signed_op_bytes
-    >>=? fun oph ->
+    let* oph =
+      Tezos_shell_services.Shell_services.Injection.operation
+        state.cctxt
+        ~chain:state.cctxt#chain
+        signed_op_bytes
+    in
     let*! () = Event.(emit2 injected) state nb oph in
     return oph
 
@@ -797,10 +798,11 @@ module Make (Parameters : PARAMETERS) = struct
     List.rev rev_ops
 
   (* Ignore operations that are allowed to fail. *)
-  let ignore_ignorable_failing_operations state operations = function
+  let ignore_ignorable_failing_operations state operations =
+    let open Lwt_result_syntax in
+    function
     | Ok res -> return (`Injected res)
     | Error err ->
-        let open Lwt_result_syntax in
         let+ operations_to_drop =
           List.fold_left_es
             (fun to_drop op ->
@@ -1471,22 +1473,24 @@ module Make (Parameters : PARAMETERS) = struct
     return_unit
 
   let worker_of_signer signer_pkh =
+    let open Result_syntax in
     match Worker.find_opt table signer_pkh with
     | None ->
         (* TODO: https://gitlab.com/tezos/tezos/-/issues/2818
            maybe lazily start worker here *)
-        error (No_worker_for_source signer_pkh)
-    | Some worker -> ok worker
+        tzfail (No_worker_for_source signer_pkh)
+    | Some worker -> return worker
 
   let worker_of_tag tag =
+    let open Result_syntax in
     match Tags_table.find_opt tags_table tag with
     | None ->
         Format.kasprintf
-          (fun s -> error (No_worker_for_tag s))
+          (fun s -> tzfail (No_worker_for_tag s))
           "%a"
           Parameters.Tag.pp
           tag
-    | Some worker -> ok worker
+    | Some worker -> return worker
 
   let add_pending_operation ?source op =
     let open Lwt_result_syntax in
diff --git a/src/lib_scoru_sequencer/dune b/src/lib_scoru_sequencer/dune
index e15cae69fa9a7b6aca214a6899006191241ed8e9..cddccfa20fbf2511a14c58843c87c030043a387d 100644
--- a/src/lib_scoru_sequencer/dune
+++ b/src/lib_scoru_sequencer/dune
@@ -20,7 +20,6 @@
   (:standard)
   -open Tezos_base
   -open Tezos_base.TzPervasives
-  -open Tezos_base.TzPervasives.Error_monad.Legacy_monad_globals
   -open Tezos_smart_rollup_layer2_alpha
   -open Tezos_protocol_alpha
   -open Tezos_workers
diff --git a/src/lib_scoru_sequencer/rpc_server.ml b/src/lib_scoru_sequencer/rpc_server.ml
index 8f3e6bd134bf2457a819661360f3249bfacbec2d..95236ebbed622376501520161078697b33ace848 100644
--- a/src/lib_scoru_sequencer/rpc_server.ml
+++ b/src/lib_scoru_sequencer/rpc_server.ml
@@ -35,7 +35,7 @@ module Local_directory = Make_directory (struct
 
   type subcontext = unit
 
-  let context_of_prefix _ll_node_ctxt () = return ()
+  let context_of_prefix _ll_node_ctxt () = Lwt_result_syntax.return_unit
 end)
 
 (* Register server handlers *)
diff --git a/src/lib_scoru_sequencer/seq_batcher.ml b/src/lib_scoru_sequencer/seq_batcher.ml
index dcaa70d5661f42645eefd5bc5acfb8388e4d2954..bddb569f604d2259e90883f61919ab2b6c9f6ec8 100644
--- a/src/lib_scoru_sequencer/seq_batcher.ml
+++ b/src/lib_scoru_sequencer/seq_batcher.ml
@@ -304,10 +304,11 @@ let init _conf ~signer node_ctxt =
 
 (* This is a batcher worker for a single scoru *)
 let worker =
+  let open Result_syntax in
   lazy
     (match Lwt.state worker_promise with
-    | Lwt.Return worker -> ok worker
-    | Lwt.Fail _ | Lwt.Sleep -> error Sc_rollup_node_errors.No_batcher)
+    | Lwt.Return worker -> return worker
+    | Lwt.Fail _ | Lwt.Sleep -> tzfail Sc_rollup_node_errors.No_batcher)
 
 let handle_request_error rq =
   let open Lwt_syntax in
diff --git a/src/lib_smart_rollup/dune b/src/lib_smart_rollup/dune
index 7924ffa64331529abc51db6bb523daa2601801a5..780eb1767e5684876ddd621f3320a34186ff9bd3 100644
--- a/src/lib_smart_rollup/dune
+++ b/src/lib_smart_rollup/dune
@@ -14,7 +14,6 @@
  (flags
   (:standard)
   -open Tezos_base.TzPervasives
-  -open Tezos_base.TzPervasives.Error_monad.Legacy_monad_globals
   -open Tezos_base
   -open Tezos_stdlib_unix
   -open Tezos_crypto))