diff --git a/CHANGES.md b/CHANGES.md
index ae11470dd..6a08f7796 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,29 @@
+# Unreleased
+
+## Features
+
+- Make `code-lens` for nested let bindings configurable (#1567)
+- Add support for `.mlx` files, including formatting via `ocamlformat-mlx` and most OCaml LSP features (diagnostics, code actions, hover, etc.) (#1528)
+
+## Fixes
+
+- Improve precision of collected metrics timestamps. (#1565)
+- Fallback on `.merlin` configuration if no `dune-project` file is found and if
+  `dot-merlin-reader` is installed. (#1563, fixes #1522)
+
+# 1.24.0
+
+## Features
+
+- Support for OCaml 5.4 (#1559)
+
+# 1.23.1
+
+## Fixes
+
+- Fix hover on method calls not showing the type. (#1553, fixes #1552)
+- Fix error on opening `.mll` files (#1557)
+
 # 1.21.0
 
 ## Features
@@ -21,6 +47,7 @@
 - More precise diagnostics in the event of a failed identifier search (`Definition_query`) (#1518)
 
 - Remove `ocamlformat` application after `destruct` (that remove some useful parenthesis) (#1519)
+- Make compatible with Yojson 3.x by removing `Tuple` and `Variant` (#1534)
 
 - Add a new server option `standardHover`, that can be used by clients to
   disable the default hover provider.  When `standardHover = false`
diff --git a/dune-project b/dune-project
index 6a22c0439..bb25689bf 100644
--- a/dune-project
+++ b/dune-project
@@ -31,7 +31,7 @@ possible and does not make any assumptions about IO.
 ")
  (depends
   (jsonrpc (= :version))
-  (yojson (< 3.0.0))
+  yojson
   (ppx_yojson_conv_lib (>= "v0.14"))
   (cinaps :with-test)
   (ppx_expect (and (>= v0.15.0) (< 0.17.0) :with-test))
@@ -45,7 +45,7 @@ possible and does not make any assumptions about IO.
  (synopsis "LSP Server for OCaml")
  (description "An LSP server for OCaml.")
  (depends
-  (yojson (< 3.0.0))
+  yojson
   (base (>= v0.16.0))
   (lsp (= :version))
   (jsonrpc (= :version))
@@ -75,8 +75,9 @@ possible and does not make any assumptions about IO.
 
 (package
  (name jsonrpc)
- (synopsis "Jsonrpc protocol implemenation")
+ (synopsis "Jsonrpc protocol implementation")
  (description "See https://www.jsonrpc.org/specification")
  (depends
+  yojson
   (ocaml (>= 4.08))
   (odoc :with-doc)))
diff --git a/jsonrpc.opam b/jsonrpc.opam
index a0c16048f..dab01279e 100644
--- a/jsonrpc.opam
+++ b/jsonrpc.opam
@@ -1,6 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
-synopsis: "Jsonrpc protocol implemenation"
+synopsis: "Jsonrpc protocol implementation"
 description: "See https://www.jsonrpc.org/specification"
 maintainer: ["Rudi Grinberg <me@rgrinberg.com>"]
 authors: [
@@ -20,6 +20,7 @@ homepage: "https://github.com/ocaml/ocaml-lsp"
 bug-reports: "https://github.com/ocaml/ocaml-lsp/issues"
 depends: [
   "dune" {>= "3.0"}
+  "yojson"
   "ocaml" {>= "4.08"}
   "odoc" {with-doc}
 ]
diff --git a/jsonrpc/src/dune b/jsonrpc/src/dune
index 4d270c2dd..15f08b825 100644
--- a/jsonrpc/src/dune
+++ b/jsonrpc/src/dune
@@ -1,4 +1,5 @@
 (library
  (public_name jsonrpc)
+ (libraries yojson)
  (instrumentation
   (backend bisect_ppx)))
diff --git a/jsonrpc/src/import.ml b/jsonrpc/src/import.ml
index 1f6bd09ee..4caaad9d5 100644
--- a/jsonrpc/src/import.ml
+++ b/jsonrpc/src/import.ml
@@ -9,18 +9,7 @@ module Option = struct
 end
 
 module Json = struct
-  type t =
-    [ `Assoc of (string * t) list
-    | `Bool of bool
-    | `Float of float
-    | `Int of int
-    | `Intlit of string
-    | `List of t list
-    | `Null
-    | `String of string
-    | `Tuple of t list
-    | `Variant of string * t option
-    ]
+  type t = Yojson.Safe.t
 
   exception Of_json of (string * t)
 
diff --git a/jsonrpc/src/jsonrpc.mli b/jsonrpc/src/jsonrpc.mli
index 9b8193772..49effa685 100644
--- a/jsonrpc/src/jsonrpc.mli
+++ b/jsonrpc/src/jsonrpc.mli
@@ -1,18 +1,7 @@
 (** Jsonrpc implementation *)
 
 module Json : sig
-  type t =
-    [ `Assoc of (string * t) list
-    | `Bool of bool
-    | `Float of float
-    | `Int of int
-    | `Intlit of string
-    | `List of t list
-    | `Null
-    | `String of string
-    | `Tuple of t list
-    | `Variant of string * t option
-    ]
+  type t = Yojson.Safe.t
 
   (** Raised when conversions from json fail *)
   exception Of_json of (string * t)
diff --git a/lsp-fiber/src/import.ml b/lsp-fiber/src/import.ml
index da49c436b..11734fbed 100644
--- a/lsp-fiber/src/import.ml
+++ b/lsp-fiber/src/import.ml
@@ -64,11 +64,11 @@ module Json = struct
     | `Bool f -> Bool f
     | `Assoc o -> Record (List.map o ~f:(fun (k, v) -> k, to_dyn v))
     | `List l -> List (List.map l ~f:to_dyn)
-    | `Tuple args -> Tuple (List.map args ~f:to_dyn)
     | `Null -> Dyn.Variant ("Null", [])
-    | `Variant (name, Some arg) -> Variant (name, [ to_dyn arg ])
-    | `Variant (name, None) -> Variant (name, [])
     | `Intlit s -> String s
+    | _ -> Dyn.Variant ("Unsupported", [])
+    (* This last case is unused with Yojson >= 3 *)
+  [@@warning "-11"]
   ;;
 end
 
diff --git a/lsp.opam b/lsp.opam
index 0cd52e318..f5041c33f 100644
--- a/lsp.opam
+++ b/lsp.opam
@@ -25,7 +25,7 @@ bug-reports: "https://github.com/ocaml/ocaml-lsp/issues"
 depends: [
   "dune" {>= "3.0"}
   "jsonrpc" {= version}
-  "yojson" {< "3.0.0"}
+  "yojson"
   "ppx_yojson_conv_lib" {>= "v0.14"}
   "cinaps" {with-test}
   "ppx_expect" {>= "v0.15.0" & < "0.17.0" & with-test}
diff --git a/lsp/bin/cinaps.ml b/lsp/bin/cinaps.ml
index c07c121b5..ea9753d61 100644
--- a/lsp/bin/cinaps.ml
+++ b/lsp/bin/cinaps.ml
@@ -7,7 +7,7 @@ let preprocess_metamodel =
     method! or_ path (types : Metamodel.type_ list) =
       match
         List.filter_map types ~f:(function
-          | Literal (Record []) -> None
+          | Metamodel.Literal (Record []) -> None
           | _ as t -> Some (self#type_ path t))
       with
       | [] -> assert false
@@ -17,10 +17,13 @@ let preprocess_metamodel =
          | Top (Alias s) when s.name = "TextDocumentContentChangeEvent" ->
            let t =
              let union_fields l1 l2 ~f =
-               let of_map =
-                 String.Map.of_list_map_exn ~f:(fun (x : Metamodel.property) -> x.name, x)
+               let of_map xs =
+                 List.map xs ~f:(fun (x : Metamodel.property) -> x.name, x)
+                 |> String.Map.of_list
                in
-               String.Map.merge (of_map l1) (of_map l2) ~f |> String.Map.values
+               String.Map.merge (of_map l1) (of_map l2) ~f
+               |> String.Map.bindings
+               |> List.map ~f:snd
              in
              union_fields f1 f2 ~f:(fun k t1 t2 ->
                if k = "text"
@@ -81,8 +84,9 @@ let expand_superclasses db (m : Metamodel.t) =
   let structures =
     let uniquify_fields fields =
       List.fold_left fields ~init:String.Map.empty ~f:(fun acc (f : Metamodel.property) ->
-        String.Map.set acc f.name f)
-      |> String.Map.values
+        String.Map.add acc ~key:f.name ~data:f)
+      |> String.Map.bindings
+      |> List.map ~f:snd
     in
     let rec fields_of_type (t : Metamodel.type_) =
       match t with
diff --git a/lsp/bin/dune b/lsp/bin/dune
index 6c2b237e6..1284abbaf 100644
--- a/lsp/bin/dune
+++ b/lsp/bin/dune
@@ -3,7 +3,7 @@
 (test
  (name test_metamodel)
  (modules test_metamodel)
- (libraries stdune yojson lsp_gen)
+ (libraries yojson lsp_gen)
  (deps metamodel/metaModel.json)
  (action
   (run ./test_metamodel.exe %{deps})))
@@ -13,4 +13,4 @@
  (instrumentation
   (backend bisect_ppx))
  (modules :standard \ test_metamodel)
- (libraries stdune dyn pp yojson))
+ (libraries dyn pp yojson))
diff --git a/lsp/bin/import.ml b/lsp/bin/import.ml
index c1b414f8f..d42629d14 100644
--- a/lsp/bin/import.ml
+++ b/lsp/bin/import.ml
@@ -1,13 +1,70 @@
-include struct
-  open Stdune
-  module List = List
-  module Id = Id
-  module String = String
-  module Code_error = Code_error
-  module Comparable = Comparable
-  module Top_closure = Top_closure
-  module Poly = Poly
-  module Option = Option
-
-  let sprintf = sprintf
+let sprintf = Printf.sprintf
+
+module Option = struct
+  include Option
+
+  let map t ~f = Option.map f t
+
+  let value_exn = function
+    | None -> assert false
+    | Some s -> s
+  ;;
+end
+
+module List = struct
+  include ListLabels
+
+  type ('a, 'b) skip_or_either =
+    | Skip
+    | Left of 'a
+    | Right of 'b
+
+  let rev_filter_partition_map =
+    let rec loop l accl accr ~f =
+      match l with
+      | [] -> accl, accr
+      | x :: l ->
+        (match f x with
+         | Skip -> loop l accl accr ~f
+         | Left y -> loop l (y :: accl) accr ~f
+         | Right y -> loop l accl (y :: accr) ~f)
+    in
+    fun l ~f -> loop l [] [] ~f
+  ;;
+
+  let filter_partition_map l ~f =
+    let l, r = rev_filter_partition_map l ~f in
+    rev l, rev r
+  ;;
+end
+
+module String = struct
+  include StringLabels
+
+  let to_dyn = Dyn.string
+
+  module Map = struct
+    include MoreLabels.Map.Make (String)
+
+    let of_list_reducei xs ~f =
+      List.fold_left xs ~init:empty ~f:(fun map (k, v) ->
+        update map ~key:k ~f:(function
+          | None -> Some v
+          | Some v' -> Some (f k v v')))
+    ;;
+
+    let of_list_map_exn xs ~f = List.map xs ~f |> of_list
+    let union_exn x y = union ~f:(fun _ _ _ -> assert false) x y
+  end
+end
+
+module Code_error = struct
+  let raise name data =
+    invalid_arg (sprintf "%s %s" name (Dyn.to_string (Dyn.record data)))
+  ;;
+end
+
+module Poly = struct
+  let equal = Stdlib.( = )
+  let compare = Stdlib.compare
 end
diff --git a/lsp/bin/metamodel/metamodel.ml b/lsp/bin/metamodel/metamodel.ml
index 7164d35bc..0fd145b54 100644
--- a/lsp/bin/metamodel/metamodel.ml
+++ b/lsp/bin/metamodel/metamodel.ml
@@ -1,4 +1,4 @@
-open Stdune
+open Import
 
 type doc =
   { since : string option
@@ -113,7 +113,7 @@ let fields = function
 ;;
 
 let field ?default (name : string) p fields =
-  match List.assoc fields name with
+  match List.assoc_opt name fields with
   | Some f -> p f
   | None ->
     (match default with
@@ -122,7 +122,7 @@ let field ?default (name : string) p fields =
 ;;
 
 let field_o name p fields =
-  match List.assoc fields name with
+  match List.assoc_opt name fields with
   | None -> None
   | Some f -> Some (p f)
 ;;
@@ -137,7 +137,7 @@ let literal lit json = if not (Poly.equal json lit) then error "unexpected liter
 let enum variants json =
   match json with
   | `String s ->
-    (match List.assoc variants s with
+    (match List.assoc_opt s variants with
      | None -> error "not a valid enum value" json
      | Some v -> v)
   | _ -> error "not a valid enum value" json
@@ -370,7 +370,7 @@ module Entity = struct
       String.Map.union_exn structures enumerations |> String.Map.union_exn typeAliases
     ;;
 
-    let find t x = String.Map.find_exn t x
+    let find t x = String.Map.find x t
   end
 end
 
diff --git a/lsp/bin/ocaml/json_gen.ml b/lsp/bin/ocaml/json_gen.ml
index 44af31da8..7f26ced93 100644
--- a/lsp/bin/ocaml/json_gen.ml
+++ b/lsp/bin/ocaml/json_gen.ml
@@ -34,7 +34,7 @@ let json_error_pat msg =
 ;;
 
 let is_json_constr (constr : Type.constr) =
-  List.mem [ "String"; "Int"; "Bool" ] constr.name ~equal:String.equal
+  List.mem ~set:[ "String"; "Int"; "Bool" ] constr.name
 ;;
 
 module Name = struct
diff --git a/lsp/bin/ocaml/ml.ml b/lsp/bin/ocaml/ml.ml
index 4973e02e2..7d76e8a9b 100644
--- a/lsp/bin/ocaml/ml.ml
+++ b/lsp/bin/ocaml/ml.ml
@@ -409,7 +409,7 @@ module Expr = struct
 
   let pp_constr f { tag; poly; args } =
     let tag =
-      let tag = String.capitalize tag in
+      let tag = String.capitalize_ascii tag in
       Pp.verbatim (if poly then "`" ^ tag else tag)
     in
     match args with
diff --git a/lsp/bin/ocaml/ocaml.ml b/lsp/bin/ocaml/ocaml.ml
index fe20955fc..5128925ca 100644
--- a/lsp/bin/ocaml/ocaml.ml
+++ b/lsp/bin/ocaml/ocaml.ml
@@ -79,9 +79,7 @@ module Expanded = struct
              | None -> init
              | Some data ->
                let new_record = { f with data } in
-               if List.mem ~equal:Poly.equal init new_record
-               then init
-               else new_record :: init)
+               if List.mem ~set:init new_record then init else new_record :: init)
         in
         super#field f ~init
     end
@@ -274,18 +272,18 @@ module Entities = struct
   type t = (Ident.t * Resolved.t) list
 
   let find db e : _ Named.t =
-    match List.assoc db e with
+    match List.assoc_opt e db with
     | Some s -> s
     | None -> Code_error.raise "Entities.find: unable to find" [ "e", Ident.to_dyn e ]
   ;;
 
   let of_map map ts =
-    List.map ts ~f:(fun (r : Resolved.t) -> String.Map.find_exn map r.name, r)
+    List.map ts ~f:(fun (r : Resolved.t) -> String.Map.find r.name map, r)
   ;;
 
   let rev_find (db : t) (resolved : Resolved.t) : Ident.t =
     match
-      List.filter_map db ~f:(fun (id, r) ->
+      List.filter_map db ~f:(fun (id, (r : Resolved.t)) ->
         if r.name = resolved.name then Some id else None)
     with
     | [] -> Code_error.raise "rev_find: resolved not found" []
@@ -327,17 +325,17 @@ end = struct
       [ Prim.Null; String; Bool; Number; Object; List ]
       |> List.map ~f:(fun s -> Resolved.Ident s)
     in
-    fun set -> List.for_all constrs ~f:(fun e -> List.mem set e ~equal:Poly.equal)
+    fun set -> List.for_all constrs ~f:(List.mem ~set)
   ;;
 
   let id = Type.name "Jsonrpc.Id.t"
 
   let is_same_as_id =
-    let sort = List.sort ~compare:Poly.compare in
+    let sort = List.sort ~cmp:Poly.compare in
     let constrs =
       [ Prim.String; Number ] |> List.map ~f:(fun s -> Resolved.Ident s) |> sort
     in
-    fun cs -> List.equal ( = ) constrs (sort cs)
+    fun cs -> List.equal ~eq:( = ) constrs (sort cs)
   ;;
 
   (* Any type that includes null needs to be extracted to be converted to an
@@ -585,7 +583,7 @@ end = struct
         let literal_wrapper =
           match literal_wrapper with
           | None -> []
-          | Some { field_name; literal_value } ->
+          | Some { Mapper.field_name; literal_value } ->
             Json_gen.make_literal_wrapper_conv
               ~field_name
               ~literal_value
@@ -626,7 +624,7 @@ let resolve_typescript (ts : Unresolved.t list) =
   let db = Entities.of_map db ts in
   match
     let idents = new name_idents in
-    Ident.Top_closure.top_closure
+    Ident.top_closure
       ts
       ~key:(fun x -> Entities.rev_find db x)
       ~deps:(fun x -> idents#t x ~init:[] |> List.map ~f:(Entities.find db))
@@ -640,7 +638,7 @@ let resolve_typescript (ts : Unresolved.t list) =
 let of_resolved_typescript db (ts : Resolved.t list) =
   let simple_enums, everything_else =
     List.filter_partition_map ts ~f:(fun (t : Resolved.t) ->
-      if List.mem skipped_ts_decls t.name ~equal:String.equal
+      if List.mem ~set:skipped_ts_decls t.name
       then Skip
       else (
         match t.data with
@@ -650,7 +648,7 @@ let of_resolved_typescript db (ts : Resolved.t list) =
   let simple_enums =
     List.map simple_enums ~f:(fun (t : _ Named.t) ->
       (* "open" enums need an `Other constructor *)
-      let allow_other = List.mem ~equal:String.equal with_custom_values t.name in
+      let allow_other = List.mem ~set:with_custom_values t.name in
       let data =
         List.filter_map t.data ~f:(fun (constr, v) ->
           match (v : Ts_types.Enum.case) with
diff --git a/lsp/bin/typescript/ts_types.ml b/lsp/bin/typescript/ts_types.ml
index c454410ed..c6206f45c 100644
--- a/lsp/bin/typescript/ts_types.ml
+++ b/lsp/bin/typescript/ts_types.ml
@@ -262,7 +262,19 @@ module Unresolved = struct
 end
 
 module Ident = struct
-  module Id = Stdune.Id.Make ()
+  module Id = struct
+    type t = int
+
+    let counter = ref 0
+
+    let gen () =
+      incr counter;
+      !counter
+    ;;
+
+    let compare = Int.compare
+    let to_dyn = Dyn.int
+  end
 
   module T = struct
     type t =
@@ -282,9 +294,44 @@ module Ident = struct
 
   let make name = { name; id = Id.gen () }
 
-  module C = Comparable.Make (T)
-  module Set = C.Set
-  module Top_closure = Top_closure.Make (Set) (Stdune.Monad.Id)
+  module Keys = struct
+    include MoreLabels.Set.Make (T)
+
+    let add x y = add y x
+    let mem x y = mem y x
+  end
+
+  let top_closure ~key ~deps elements =
+    let rec loop res visited elt ~temporarily_marked =
+      let key = key elt in
+      if Keys.mem temporarily_marked key
+      then Error [ elt ]
+      else if not (Keys.mem visited key)
+      then (
+        let visited = Keys.add visited key in
+        let temporarily_marked = Keys.add temporarily_marked key in
+        deps elt
+        |> iter_elts res visited ~temporarily_marked
+        |> function
+        | Error l -> Error (elt :: l)
+        | Ok (res, visited) ->
+          let res = elt :: res in
+          Ok (res, visited))
+      else Ok (res, visited)
+    and iter_elts res visited elts ~temporarily_marked =
+      match elts with
+      | [] -> Ok (res, visited)
+      | elt :: elts ->
+        loop res visited elt ~temporarily_marked
+        |> (function
+         | Error _ as result -> result
+         | Ok (res, visited) -> iter_elts res visited elts ~temporarily_marked)
+    in
+    iter_elts [] Keys.empty elements ~temporarily_marked:Keys.empty
+    |> function
+    | Ok (res, _visited) -> Ok (List.rev res)
+    | Error elts -> Error elts
+  ;;
 end
 
 module Prim = struct
@@ -345,15 +392,15 @@ let subst unresolved =
     method inside s = {<inside = Some s>}
 
     method resolve n =
-      match String.Map.find params n with
+      match String.Map.find_opt n params with
       | Some [] -> assert false
       | Some (x :: _) -> `Resolved x
       | None ->
-        if inside = Some n then `Self else `Unresolved (String.Map.find_exn unresolved n)
+        if inside = Some n then `Self else `Unresolved (String.Map.find n unresolved)
 
     method push x y =
       let params =
-        String.Map.update params x ~f:(function
+        String.Map.update params ~key:x ~f:(function
           | None -> Some [ y ]
           | Some [] -> assert false
           | Some (y' :: xs) -> if y = y' then Some xs else Some (y :: y' :: xs))
@@ -362,9 +409,9 @@ let subst unresolved =
 
     method pop x =
       let params =
-        String.Map.update params x ~f:(function
+        String.Map.update params ~key:x ~f:(function
           | None ->
-            ignore (String.Map.find_exn params x);
+            ignore (String.Map.find x params);
             None
           | Some [] -> assert false
           | Some (_ :: xs) -> Some xs)
diff --git a/lsp/bin/typescript/ts_types.mli b/lsp/bin/typescript/ts_types.mli
index aa33961b9..7f3f72904 100644
--- a/lsp/bin/typescript/ts_types.mli
+++ b/lsp/bin/typescript/ts_types.mli
@@ -86,7 +86,9 @@ module Unresolved : sig
 end
 
 module Ident : sig
-  module Id : Id.S
+  module Id : sig
+    type t
+  end
 
   type t =
     { id : Id.t
@@ -96,13 +98,11 @@ module Ident : sig
   val to_dyn : t -> Dyn.t
   val make : string -> t
 
-  module Top_closure : sig
-    val top_closure
-      :  key:('a -> t)
-      -> deps:('a -> 'a list)
-      -> 'a list
-      -> ('a list, 'a list) result
-  end
+  val top_closure
+    :  key:('a -> t)
+    -> deps:('a -> 'a list)
+    -> 'a list
+    -> ('a list, 'a list) result
 end
 
 module Prim : sig
diff --git a/lsp/bin/typescript/typescript.ml b/lsp/bin/typescript/typescript.ml
index e755d14cd..84ed555fd 100644
--- a/lsp/bin/typescript/typescript.ml
+++ b/lsp/bin/typescript/typescript.ml
@@ -19,7 +19,7 @@ let name_table (defns : Unresolved.t list) =
 
 let resolve_all (defns : Unresolved.t list) =
   let names = name_table defns in
-  let defns = String.Map.values names |> List.map ~f:fst in
+  let defns = String.Map.bindings names |> List.map ~f:snd |> List.map ~f:fst in
   let names = String.Map.map ~f:snd names in
   Ts_types.resolve_all defns ~names, names
 ;;
diff --git a/ocaml-lsp-server.opam b/ocaml-lsp-server.opam
index 5f1a83a76..08c422c0e 100644
--- a/ocaml-lsp-server.opam
+++ b/ocaml-lsp-server.opam
@@ -20,7 +20,7 @@ homepage: "https://github.com/ocaml/ocaml-lsp"
 bug-reports: "https://github.com/ocaml/ocaml-lsp/issues"
 depends: [
   "dune" {>= "3.0"}
-  "yojson" {< "3.0.0"}
+  "yojson"
   "base" {>= "v0.16.0"}
   "lsp" {= version}
   "jsonrpc" {= version}
diff --git a/ocaml-lsp-server/bin/main.ml b/ocaml-lsp-server/bin/main.ml
index 6aef73d00..1be7332d9 100644
--- a/ocaml-lsp-server/bin/main.ml
+++ b/ocaml-lsp-server/bin/main.ml
@@ -4,20 +4,23 @@ module Cli = Lsp.Cli
 let () =
   Printexc.record_backtrace true;
   let version = ref false in
-  let read_dot_merlin = ref false in
+  let prefer_dot_merlin = ref false in
   let arg = Lsp.Cli.Arg.create () in
   let spec =
     [ "--version", Arg.Set version, "print version"
     ; ( "--fallback-read-dot-merlin"
-      , Arg.Set read_dot_merlin
-      , "read Merlin config from .merlin files. The `dot-merlin-reader` package must be \
-         installed" )
+      , Arg.Set prefer_dot_merlin
+      , "deprecated, same as --prefer-dot-merlin" )
+    ; ( "--prefer-dot-merlin"
+      , Arg.Set prefer_dot_merlin
+      , "always read Merlin config from existing .merlin files. The `dot-merlin-reader` \
+         package must be installed" )
     ]
     @ Cli.Arg.spec arg
   in
   let usage =
     "ocamllsp [ --stdio | --socket PORT | --port PORT | --pipe PIPE ] [ \
-     --clientProcessId pid ]"
+     --clientProcessId pid ] [ --prefer-dot-merlin ]"
   in
   Arg.parse spec (fun _ -> raise @@ Arg.Bad "anonymous arguments aren't allowed") usage;
   let channel =
@@ -37,7 +40,7 @@ let () =
     let module Exn_with_backtrace = Stdune.Exn_with_backtrace in
     match
       Exn_with_backtrace.try_with
-        (Ocaml_lsp_server.run channel ~read_dot_merlin:!read_dot_merlin)
+        (Ocaml_lsp_server.run channel ~prefer_dot_merlin:!prefer_dot_merlin)
     with
     | Ok () -> ()
     | Error exn ->
diff --git a/ocaml-lsp-server/docs/ocamllsp/config.md b/ocaml-lsp-server/docs/ocamllsp/config.md
index aea4ddfc3..4eb601516 100644
--- a/ocaml-lsp-server/docs/ocamllsp/config.md
+++ b/ocaml-lsp-server/docs/ocamllsp/config.md
@@ -15,12 +15,21 @@ interface config {
   */
   extendedHover: { enable : boolean }
 
-  /**
-  * Enable/Disable CodeLens
-  * @default false
-  * @since 1.16
-  */
-  codelens: { enable : boolean }
+  codelens: {
+    /**
+    * Enable/Disable CodeLens
+    * @default false
+    * @since 1.16
+    */
+    enable : boolean,
+
+    /**
+    * Enable CodeLens for nested let bindings
+    * @default false
+    * @since 1.25
+    */
+    forNestedBindings : boolean
+  }
 
   /**
   * Enable/Disable Dune diagnostics
diff --git a/ocaml-lsp-server/src/code_actions.ml b/ocaml-lsp-server/src/code_actions.ml
index 662599eea..3c2eb2f21 100644
--- a/ocaml-lsp-server/src/code_actions.ml
+++ b/ocaml-lsp-server/src/code_actions.ml
@@ -54,12 +54,10 @@ let compute_ocaml_code_actions (params : CodeActionParams.t) state doc =
       ]
   in
   let batchable, non_batchable =
-    List.partition_map
-      ~f:(fun ca ->
-        match ca.run with
-        | `Batchable f -> Left f
-        | `Non_batchable f -> Right f)
-      enabled_actions
+    List.partition_map enabled_actions ~f:(fun ca ->
+      match ca.run with
+      | `Batchable f -> Base.Either.First f
+      | `Non_batchable f -> Second f)
   in
   let* batch_results =
     if List.is_empty batchable
@@ -125,7 +123,7 @@ let compute server (params : CodeActionParams.t) =
     (match Document.syntax doc with
      | Ocamllex | Menhir | Cram | Dune ->
        Fiber.return (Reply.now (actions (dune_actions @ open_related)), state)
-     | Ocaml | Reason ->
+     | Ocaml | Reason | Mlx ->
        let reply () =
          let+ code_action_results = compute_ocaml_code_actions params state doc in
          List.concat [ code_action_results; dune_actions; open_related; merlin_jumps ]
diff --git a/ocaml-lsp-server/src/code_actions/action_construct.ml b/ocaml-lsp-server/src/code_actions/action_construct.ml
index 5a529543f..3fd5ea045 100644
--- a/ocaml-lsp-server/src/code_actions/action_construct.ml
+++ b/ocaml-lsp-server/src/code_actions/action_construct.ml
@@ -14,7 +14,7 @@ let code_action pipeline doc (params : CodeActionParams.t) =
       let src = Document.source doc in
       Compl.prefix_of_position ~short_path:false src pos
     in
-    if not (Merlin_analysis.Typed_hole.can_be_hole prefix)
+    if not (Typed_hole.can_be_hole prefix)
     then None
     else (
       let structures =
@@ -25,7 +25,7 @@ let code_action pipeline doc (params : CodeActionParams.t) =
         let pos = Mpipeline.get_lexing_pos pipeline pos in
         Mbrowse.enclosing pos [ Mbrowse.of_typedtree typedtree ]
       in
-      if not (Merlin_analysis.Typed_hole.is_a_hole structures)
+      if not (Typed_hole.is_a_hole structures)
       then None
       else (
         (* ocaml-lsp can provide [Construct] values as completion entries, so
diff --git a/ocaml-lsp-server/src/compl.ml b/ocaml-lsp-server/src/compl.ml
index c5054ff2f..3ef48110e 100644
--- a/ocaml-lsp-server/src/compl.ml
+++ b/ocaml-lsp-server/src/compl.ml
@@ -315,7 +315,7 @@ let complete
                 let* item = completion_item_capability in
                 item.deprecatedSupport)
            in
-           if not (Merlin_analysis.Typed_hole.can_be_hole prefix)
+           if not (Typed_hole.can_be_hole prefix)
            then Complete_by_prefix.complete merlin prefix pos ~resolve ~deprecated
            else (
              let reindex_sortText completion_items =
diff --git a/ocaml-lsp-server/src/config_data.ml b/ocaml-lsp-server/src/config_data.ml
index 3fe22ce36..ccfa0c808 100644
--- a/ocaml-lsp-server/src/config_data.ml
+++ b/ocaml-lsp-server/src/config_data.ml
@@ -192,70 +192,91 @@ module InlayHints = struct
 end
 
 module Lens = struct
-  type t = { enable : bool [@default true] }
+  type t =
+    { enable : bool [@default true]
+    ; for_nested_bindings : bool [@key "forNestedBindings"] [@default false]
+    }
   [@@deriving_inline yojson] [@@yojson.allow_extra_fields]
 
   let _ = fun (_ : t) -> ()
 
-  let t_of_yojson =
-    (let _tp_loc = "ocaml-lsp-server/src/config_data.ml.Lens.t" in
-     function
-     | `Assoc field_yojsons as yojson ->
+  
+let t_of_yojson =
+  (let _tp_loc = "ocaml-lsp-server/src/config_data.ml.Lens.t" in
+   function
+   | `Assoc field_yojsons as yojson ->
        let enable_field = ref Ppx_yojson_conv_lib.Option.None
+       and for_nested_bindings_field = ref Ppx_yojson_conv_lib.Option.None
        and duplicates = ref []
        and extra = ref [] in
-       let rec iter = function
-         | (field_name, _field_yojson) :: tail ->
-           (match field_name with
-            | "enable" ->
-              (match Ppx_yojson_conv_lib.( ! ) enable_field with
-               | Ppx_yojson_conv_lib.Option.None ->
-                 let fvalue = bool_of_yojson _field_yojson in
-                 enable_field := Ppx_yojson_conv_lib.Option.Some fvalue
-               | Ppx_yojson_conv_lib.Option.Some _ ->
-                 duplicates := field_name :: Ppx_yojson_conv_lib.( ! ) duplicates)
-            | _ -> ());
-           iter tail
-         | [] -> ()
-       in
-       iter field_yojsons;
-       (match Ppx_yojson_conv_lib.( ! ) duplicates with
-        | _ :: _ ->
-          Ppx_yojson_conv_lib.Yojson_conv_error.record_duplicate_fields
-            _tp_loc
-            (Ppx_yojson_conv_lib.( ! ) duplicates)
-            yojson
-        | [] ->
-          (match Ppx_yojson_conv_lib.( ! ) extra with
-           | _ :: _ ->
-             Ppx_yojson_conv_lib.Yojson_conv_error.record_extra_fields
-               _tp_loc
-               (Ppx_yojson_conv_lib.( ! ) extra)
-               yojson
-           | [] ->
-             let enable_value = Ppx_yojson_conv_lib.( ! ) enable_field in
-             { enable =
-                 (match enable_value with
-                  | Ppx_yojson_conv_lib.Option.None -> true
-                  | Ppx_yojson_conv_lib.Option.Some v -> v)
-             }))
-     | _ as yojson ->
-       Ppx_yojson_conv_lib.Yojson_conv_error.record_list_instead_atom _tp_loc yojson
-     : Ppx_yojson_conv_lib.Yojson.Safe.t -> t)
+       let rec iter =
+         function
+         | (field_name, _field_yojson)::tail ->
+             ((match field_name with
+               | "enable" ->
+                   (match Ppx_yojson_conv_lib.(!) enable_field with
+                    | Ppx_yojson_conv_lib.Option.None ->
+                        let fvalue = bool_of_yojson _field_yojson in
+                        enable_field :=
+                          (Ppx_yojson_conv_lib.Option.Some fvalue)
+                    | Ppx_yojson_conv_lib.Option.Some _ ->
+                        duplicates := (field_name ::
+                          (Ppx_yojson_conv_lib.(!) duplicates)))
+               | "forNestedBindings" ->
+                   (match Ppx_yojson_conv_lib.(!) for_nested_bindings_field
+                    with
+                    | Ppx_yojson_conv_lib.Option.None ->
+                        let fvalue = bool_of_yojson _field_yojson in
+                        for_nested_bindings_field :=
+                          (Ppx_yojson_conv_lib.Option.Some fvalue)
+                    | Ppx_yojson_conv_lib.Option.Some _ ->
+                        duplicates := (field_name ::
+                          (Ppx_yojson_conv_lib.(!) duplicates)))
+               | _ -> ());
+              iter tail)
+         | [] -> () in
+       (iter field_yojsons;
+        (match Ppx_yojson_conv_lib.(!) duplicates with
+         | _::_ ->
+             Ppx_yojson_conv_lib.Yojson_conv_error.record_duplicate_fields
+               _tp_loc (Ppx_yojson_conv_lib.(!) duplicates) yojson
+         | [] ->
+             (match Ppx_yojson_conv_lib.(!) extra with
+              | _::_ ->
+                  Ppx_yojson_conv_lib.Yojson_conv_error.record_extra_fields
+                    _tp_loc (Ppx_yojson_conv_lib.(!) extra) yojson
+              | [] ->
+                  let (enable_value, for_nested_bindings_value) =
+                    ((Ppx_yojson_conv_lib.(!) enable_field),
+                      (Ppx_yojson_conv_lib.(!) for_nested_bindings_field)) in
+                  {
+                    enable =
+                      ((match enable_value with
+                        | Ppx_yojson_conv_lib.Option.None -> true
+                        | Ppx_yojson_conv_lib.Option.Some v -> v));
+                    for_nested_bindings =
+                      ((match for_nested_bindings_value with
+                        | Ppx_yojson_conv_lib.Option.None -> false
+                        | Ppx_yojson_conv_lib.Option.Some v -> v))
+                  })))
+   | _ as yojson ->
+       Ppx_yojson_conv_lib.Yojson_conv_error.record_list_instead_atom _tp_loc
+         yojson : Ppx_yojson_conv_lib.Yojson.Safe.t -> t)
   ;;
 
   let _ = t_of_yojson
 
-  let yojson_of_t =
-    (function
-     | { enable = v_enable } ->
+  
+let yojson_of_t =
+  (function
+   | { enable = v_enable; for_nested_bindings = v_for_nested_bindings } ->
        let bnds : (string * Ppx_yojson_conv_lib.Yojson.Safe.t) list = [] in
        let bnds =
-         let arg = yojson_of_bool v_enable in
-         ("enable", arg) :: bnds
-       in
-       `Assoc bnds
-     : t -> Ppx_yojson_conv_lib.Yojson.Safe.t)
+         let arg = yojson_of_bool v_for_nested_bindings in
+         ("forNestedBindings", arg) :: bnds in
+       let bnds =
+         let arg = yojson_of_bool v_enable in ("enable", arg) :: bnds in
+       `Assoc bnds : t -> Ppx_yojson_conv_lib.Yojson.Safe.t)
   ;;
 
   let _ = yojson_of_t
@@ -921,7 +942,7 @@ let _ = yojson_of_t
 [@@@end]
 
 let default =
-  { codelens = Some { enable = false }
+  { codelens = Some { enable = false; for_nested_bindings = false }
   ; extended_hover = Some { enable = false }
   ; standard_hover = Some { enable = true }
   ; inlay_hints =
diff --git a/ocaml-lsp-server/src/document.ml b/ocaml-lsp-server/src/document.ml
index ec1ec2956..fd4a64da4 100644
--- a/ocaml-lsp-server/src/document.ml
+++ b/ocaml-lsp-server/src/document.ml
@@ -8,7 +8,7 @@ module Kind = struct
 
   let of_fname_opt p =
     match Filename.extension p with
-    | ".ml" | ".eliom" | ".re" -> Some Impl
+    | ".ml" | ".eliom" | ".re" | ".mll" | ".mly" | ".mlx" -> Some Impl
     | ".mli" | ".eliomi" | ".rei" -> Some Intf
     | _ -> None
   ;;
@@ -32,6 +32,7 @@ module Syntax = struct
     | Menhir
     | Cram
     | Dune
+    | Mlx
 
   let human_name = function
     | Ocaml -> "OCaml"
@@ -40,6 +41,7 @@ module Syntax = struct
     | Menhir -> "Menhir/ocamlyacc"
     | Cram -> "Cram"
     | Dune -> "Dune"
+    | Mlx -> "OCaml.mlx"
   ;;
 
   let all =
@@ -52,6 +54,7 @@ module Syntax = struct
     ; "dune", Dune
     ; "dune-project", Dune
     ; "dune-workspace", Dune
+    ; "ocaml.mlx", Mlx
     ]
   ;;
 
@@ -61,6 +64,7 @@ module Syntax = struct
       | s ->
         (match Filename.extension s with
          | ".eliomi" | ".eliom" | ".mli" | ".ml" -> Ok Ocaml
+         | ".mlx" -> Ok Mlx
          | ".rei" | ".re" -> Ok Reason
          | ".mll" -> Ok Ocamllex
          | ".mly" -> Ok Menhir
@@ -156,10 +160,10 @@ end = struct
     let task =
       match
         Lev_fiber.Thread.task t.thread ~f:(fun () ->
-          let start = Unix.time () in
+          let start = Unix.gettimeofday () in
           let pipeline = make_pipeline () in
           let res = Mpipeline.with_pipeline pipeline (fun () -> f pipeline) in
-          let stop = Unix.time () in
+          let stop = Unix.gettimeofday () in
           res, start, stop)
       with
       | Error `Stopped -> assert false
@@ -252,7 +256,7 @@ let make wheel config pipeline (doc : DidOpenTextDocumentParams.t) ~position_enc
     let tdoc = Text_document.make ~position_encoding doc in
     let syntax = Syntax.of_text_document tdoc in
     match syntax with
-    | Ocaml | Reason -> make_merlin wheel config pipeline tdoc syntax
+    | Ocaml | Reason | Mlx -> make_merlin wheel config pipeline tdoc syntax
     | Ocamllex | Menhir | Cram | Dune -> Fiber.return (Other { tdoc; syntax }))
 ;;
 
@@ -421,8 +425,8 @@ let close t =
 let get_impl_intf_counterparts m uri =
   let fpath = Uri.to_path uri in
   let fname = Filename.basename fpath in
-  let ml, mli, eliom, eliomi, re, rei, mll, mly =
-    "ml", "mli", "eliom", "eliomi", "re", "rei", "mll", "mly"
+  let ml, mli, eliom, eliomi, re, rei, mll, mly, mlx =
+    "ml", "mli", "eliom", "eliomi", "re", "rei", "mll", "mly", "mlx"
   in
   let exts_to_switch_to =
     let kind =
@@ -436,13 +440,17 @@ let get_impl_intf_counterparts m uri =
     in
     match Syntax.of_fname fname with
     | Dune | Cram -> []
+    | Mlx ->
+      (match kind with
+       | Intf -> [ ml; mly; mll; mlx; re ]
+       | Impl -> [ rei; mli; mly; mll; rei ])
     | Ocaml ->
       (match kind with
-       | Intf -> [ ml; mly; mll; eliom; re ]
+       | Intf -> [ ml; mly; mll; eliom; re; mlx ]
        | Impl -> [ mli; mly; mll; eliomi; rei ])
     | Reason ->
       (match kind with
-       | Intf -> [ re; ml ]
+       | Intf -> [ re; ml; mlx ]
        | Impl -> [ rei; mli ])
     | Ocamllex -> [ mli; rei ]
     | Menhir -> [ mli; rei ]
diff --git a/ocaml-lsp-server/src/document.mli b/ocaml-lsp-server/src/document.mli
index 735bfd659..6585b6f0b 100644
--- a/ocaml-lsp-server/src/document.mli
+++ b/ocaml-lsp-server/src/document.mli
@@ -10,6 +10,7 @@ module Syntax : sig
     | Menhir
     | Cram
     | Dune
+    | Mlx
 
   val human_name : t -> string
   val markdown_name : t -> string
diff --git a/ocaml-lsp-server/src/dune.ml b/ocaml-lsp-server/src/dune.ml
index 9ebacc37b..e3dbdad2b 100644
--- a/ocaml-lsp-server/src/dune.ml
+++ b/ocaml-lsp-server/src/dune.ml
@@ -112,10 +112,7 @@ module Poll =
         | s -> Ok (`Mtime s.st_mtime)
       ;;
 
-      let read_file s =
-        Fiber.of_thunk (fun () ->
-          Fiber.return (Result.try_with (fun () -> Io.String_path.read_file s)))
-      ;;
+      let read_file s = Fiber.of_thunk (fun () -> Fiber.return (Io.read_file s))
     end)
 
 type config =
diff --git a/ocaml-lsp-server/src/hover_req.ml b/ocaml-lsp-server/src/hover_req.ml
index 8a5f932b6..170135475 100644
--- a/ocaml-lsp-server/src/hover_req.ml
+++ b/ocaml-lsp-server/src/hover_req.ml
@@ -58,8 +58,10 @@ let hover_at_cursor parsetree (`Logical (cursor_line, cursor_col)) =
     then (
       match expr.pexp_desc with
       | Pexp_constant _ | Pexp_variant _ | Pexp_pack _ -> result := Some `Type_enclosing
-      | Pexp_ident { loc; _ } | Pexp_construct ({ loc; _ }, _) | Pexp_field (_, { loc; _ })
-        ->
+      | Pexp_ident { loc; _ }
+      | Pexp_construct ({ loc; _ }, _)
+      | Pexp_field (_, { loc; _ })
+      | Pexp_send (_, { loc; _ }) ->
         if is_at_cursor loc
         then result := Some `Type_enclosing
         else Ast_iterator.default_iterator.expr self expr
diff --git a/ocaml-lsp-server/src/import.ml b/ocaml-lsp-server/src/import.ml
index 48210f5fd..47daff368 100644
--- a/ocaml-lsp-server/src/import.ml
+++ b/ocaml-lsp-server/src/import.ml
@@ -9,7 +9,6 @@ include struct
   module Table = Table
   module Tuple = Tuple
   module Unix_env = Env
-  module Io = Io
   module Map = Map
   module Monoid = Monoid
   module Pid = Pid
@@ -18,6 +17,31 @@ include struct
   let sprintf = sprintf
 end
 
+module Io = struct
+  open Base
+
+  let read_file f =
+    Base.Result.try_with (fun () ->
+      let fd = Unix.openfile f [ O_CLOEXEC; O_RDONLY ] 0 in
+      Exn.protect
+        ~finally:(fun () -> Unix.close fd)
+        ~f:(fun () ->
+          match Unix.fstat fd with
+          | { Unix.st_size; _ } ->
+            let buf = Bytes.create st_size in
+            let rec loop pos remains =
+              if remains > 0
+              then (
+                let read = Unix.read fd buf pos remains in
+                if read = 0
+                then failwith (sprintf "unable to read all of %s" f)
+                else loop (pos + read) (remains - read))
+            in
+            loop 0 st_size;
+            Stdlib.Bytes.unsafe_to_string buf))
+  ;;
+end
+
 include struct
   open Base
   module Queue = Queue
@@ -37,13 +61,34 @@ include struct
 end
 
 module List = struct
-  include Stdune.List
-  open Base.List
+  include Base.List
 
+  let compare xs ys ~compare =
+    Base.List.compare (fun x y -> Ordering.to_int (compare x y)) xs ys
+  ;;
+
+  let sort xs ~compare = sort xs ~compare:(fun x y -> Ordering.to_int (compare x y))
+  let fold_left2 xs ys ~init ~f = Stdlib.List.fold_left2 f init xs ys
+  let assoc xs key = Assoc.find ~equal:Poly.equal xs key
+  let assoc_opt xs key = assoc xs key
+  let mem t x ~equal = mem t x ~equal
+  let map t ~f = map t ~f
+  let concat_map t ~f = concat_map t ~f
+  let flatten t = Stdlib.List.flatten t
+  let filter_map t ~f = filter_map t ~f
+  let fold_left t ~init ~f = fold_left t ~init ~f
   let findi xs ~f = findi xs ~f
+  let find_opt xs ~f = find xs ~f
+
+  let sort_uniq xs ~compare =
+    Stdlib.List.sort_uniq (fun x y -> Ordering.to_int (compare x y)) xs
+  ;;
+
+  let for_all xs ~f = for_all xs ~f
   let find_mapi xs ~f = find_mapi xs ~f
   let sub xs ~pos ~len = sub xs ~pos ~len
   let hd_exn t = hd_exn t
+  let hd_opt t = hd t
   let nth_exn t n = nth_exn t n
   let hd t = hd t
   let filter t ~f = filter t ~f
diff --git a/ocaml-lsp-server/src/inference.ml b/ocaml-lsp-server/src/inference.ml
index d51401e31..3771fe90f 100644
--- a/ocaml-lsp-server/src/inference.ml
+++ b/ocaml-lsp-server/src/inference.ml
@@ -71,6 +71,7 @@ let language_id_of_fname s =
   | ".mli" | ".eliomi" -> "ocaml.interface"
   | ".ml" | ".eliom" -> "ocaml"
   | ".rei" | ".re" -> "reason"
+  | ".mlx" -> "ocaml.mlx"
   | ".mll" -> "ocaml.ocamllex"
   | ".mly" -> "ocaml.menhir"
   | ext -> Code_error.raise "unsupported file extension" [ "extension", String ext ]
@@ -79,12 +80,12 @@ let language_id_of_fname s =
 let open_document_from_file (state : State.t) uri =
   let filename = Uri.to_path uri in
   Fiber.of_thunk (fun () ->
-    match Io.String_path.read_file filename with
-    | exception Sys_error _ ->
+    match Io.read_file filename with
+    | Error _ ->
       Log.log ~section:"debug" (fun () ->
         Log.msg "Unable to open file" [ "filename", `String filename ]);
       Fiber.return None
-    | text ->
+    | Ok text ->
       let languageId = language_id_of_fname filename in
       let text_document = TextDocumentItem.create ~uri ~languageId ~version:0 ~text in
       let params = DidOpenTextDocumentParams.create ~textDocument:text_document in
diff --git a/ocaml-lsp-server/src/inlay_hints.ml b/ocaml-lsp-server/src/inlay_hints.ml
index daf085a39..8e87a309d 100644
--- a/ocaml-lsp-server/src/inlay_hints.ml
+++ b/ocaml-lsp-server/src/inlay_hints.ml
@@ -29,22 +29,12 @@ let compute (state : State.t) { InlayHintParams.range; textDocument = { uri }; _
           c.hint_pattern_variables)
         |> Option.value ~default:false
       in
-      let hint_function_params =
-        Option.map state.configuration.data.inlay_hints ~f:(fun c ->
-          c.hint_function_params)
-        |> Option.value ~default:false
-      in
       Document.Merlin.with_pipeline_exn ~name:"inlay-hints" doc (fun pipeline ->
         let start = range.start |> Position.logical
         and stop = range.end_ |> Position.logical in
         let command =
           Query_protocol.Inlay_hints
-            ( start
-            , stop
-            , hint_let_bindings
-            , hint_pattern_variables
-            , hint_function_params
-            , not inside_test )
+            (start, stop, hint_let_bindings, hint_pattern_variables, not inside_test)
         in
         let hints = Query_commands.dispatch pipeline command in
         List.filter_map
diff --git a/ocaml-lsp-server/src/merlin_config.ml b/ocaml-lsp-server/src/merlin_config.ml
index 50ce15d5d..4e0a55096 100644
--- a/ocaml-lsp-server/src/merlin_config.ml
+++ b/ocaml-lsp-server/src/merlin_config.ml
@@ -119,7 +119,7 @@ module Dot_protocol_io =
       let write t x = write t [ x ]
     end)
 
-let should_read_dot_merlin = ref false
+let prefer_dot_merlin = ref false
 
 type db =
   { running : (string, entry) Table.t
@@ -299,13 +299,13 @@ let config (t : t) : Mconfig.t Fiber.t =
     t.entry <- Some entry
   in
   let* () = Fiber.return () in
-  if !should_read_dot_merlin
+  if !prefer_dot_merlin
   then Fiber.return (Mconfig.get_external_config t.path t.initial)
   else (
     match find_project_context t.directory with
     | None ->
       let+ () = destroy t in
-      t.initial
+      Mconfig.get_external_config t.path t.initial
     | Some (ctx, config_path) ->
       let* entry = get_process t.db ~dir:ctx.process_dir in
       let* () =
diff --git a/ocaml-lsp-server/src/merlin_config.mli b/ocaml-lsp-server/src/merlin_config.mli
index bc057f038..b8431d471 100644
--- a/ocaml-lsp-server/src/merlin_config.mli
+++ b/ocaml-lsp-server/src/merlin_config.mli
@@ -4,7 +4,7 @@ open Import
 
 type t
 
-val should_read_dot_merlin : bool ref
+val prefer_dot_merlin : bool ref
 val config : t -> Mconfig.t Fiber.t
 val destroy : t -> unit Fiber.t
 
diff --git a/ocaml-lsp-server/src/ocaml_lsp_server.ml b/ocaml-lsp-server/src/ocaml_lsp_server.ml
index 3a2ea56f4..b0746ebc5 100644
--- a/ocaml-lsp-server/src/ocaml_lsp_server.ml
+++ b/ocaml-lsp-server/src/ocaml_lsp_server.ml
@@ -203,7 +203,7 @@ let set_diagnostics detached diagnostics doc =
        in
        Diagnostics.set diagnostics (`Merlin (uri, [ no_reason_merlin ]));
        async (fun () -> Diagnostics.send diagnostics (`One uri))
-     | Reason | Ocaml ->
+     | Reason | Ocaml | Mlx ->
        async (fun () ->
          let* () = Diagnostics.merlin_diagnostics diagnostics merlin in
          Diagnostics.send diagnostics (`One uri)))
@@ -363,7 +363,11 @@ module Formatter = struct
   ;;
 end
 
-let text_document_lens (state : State.t) { CodeLensParams.textDocument = { uri }; _ } =
+let text_document_lens
+      (state : State.t)
+      { CodeLensParams.textDocument = { uri }; _ }
+      ~for_nested_bindings
+  =
   let store = state.store in
   let doc = Document_store.get store uri in
   match Document.kind doc with
@@ -372,7 +376,11 @@ let text_document_lens (state : State.t) { CodeLensParams.textDocument = { uri }
   | `Merlin doc ->
     let+ outline = Document.Merlin.dispatch_exn ~name:"outline" doc Outline in
     let rec symbol_info_of_outline_item (item : Query_protocol.item) =
-      let children = List.concat_map item.children ~f:symbol_info_of_outline_item in
+      let children =
+        if for_nested_bindings
+        then List.concat_map item.children ~f:symbol_info_of_outline_item
+        else []
+      in
       match item.outline_type with
       | None -> children
       | Some typ ->
@@ -496,6 +504,7 @@ let on_request
   match req with
   | Client_request.UnknownRequest { meth; params } ->
     (match
+       List.assoc
        [ ( Req_switch_impl_intf.meth
          , fun ~params state ->
              Fiber.of_thunk (fun () ->
@@ -514,8 +523,7 @@ let on_request
          , Semantic_highlighting.Debug.on_request_full )
        ; ( Req_hover_extended.meth
          , fun ~params _ -> Req_hover_extended.on_request ~params rpc )
-       ]
-       |> List.assoc_opt meth
+       ] meth
      with
      | None ->
        Jsonrpc.Response.Error.raise
@@ -620,7 +628,8 @@ let on_request
   | TextDocumentCodeLensResolve codeLens -> now codeLens
   | TextDocumentCodeLens req ->
     (match state.configuration.data.codelens with
-     | Some { enable = true } -> later text_document_lens req
+     | Some { enable = true; for_nested_bindings } ->
+       later (text_document_lens ~for_nested_bindings) req
      | _ -> now [])
   | TextDocumentHighlight req -> later highlight req
   | DocumentSymbol { textDocument = { uri }; _ } -> later document_symbol uri
@@ -954,10 +963,10 @@ let run_in_directory =
   fun () -> if Sys.win32 then for_windows else run_in_directory
 ;;
 
-let run channel ~read_dot_merlin () =
+let run channel ~prefer_dot_merlin () =
   Merlin_utils.Lib_config.set_program_name "ocamllsp";
   Merlin_utils.Lib_config.System.set_run_in_directory (run_in_directory ());
-  Merlin_config.should_read_dot_merlin := read_dot_merlin;
+  Merlin_config.prefer_dot_merlin := prefer_dot_merlin;
   Unix.putenv "__MERLIN_MASTER_PID" (string_of_int (Unix.getpid ()));
   Lev_fiber.run ~sigpipe:`Ignore (fun () ->
     let* input, output = stream_of_channel channel in
diff --git a/ocaml-lsp-server/src/ocaml_lsp_server.mli b/ocaml-lsp-server/src/ocaml_lsp_server.mli
index e74891253..76cc6c224 100644
--- a/ocaml-lsp-server/src/ocaml_lsp_server.mli
+++ b/ocaml-lsp-server/src/ocaml_lsp_server.mli
@@ -1,4 +1,4 @@
-val run : Lsp.Cli.Channel.t -> read_dot_merlin:bool -> unit -> unit
+val run : Lsp.Cli.Channel.t -> prefer_dot_merlin:bool -> unit -> unit
 
 module Diagnostics = Diagnostics
 module Version = Version
diff --git a/ocaml-lsp-server/src/ocamlformat.ml b/ocaml-lsp-server/src/ocamlformat.ml
index 28437f21f..4c6ce3757 100644
--- a/ocaml-lsp-server/src/ocamlformat.ml
+++ b/ocaml-lsp-server/src/ocamlformat.ml
@@ -100,9 +100,11 @@ let message = function
 type formatter =
   | Reason of Document.Kind.t
   | Ocaml of Uri.t
+  | Mlx of Uri.t
 
 let args = function
   | Ocaml uri -> [ sprintf "--name=%s" (Uri.to_path uri); "-" ]
+  | Mlx uri -> [ "--impl"; sprintf "--name=%s" (Uri.to_path uri); "-" ]
   | Reason kind ->
     [ "--parse"; "re"; "--print"; "re" ]
     @
@@ -114,6 +116,7 @@ let args = function
 let binary_name t =
   match t with
   | Ocaml _ -> "ocamlformat"
+  | Mlx _ -> "ocamlformat-mlx"
   | Reason _ -> "refmt"
 ;;
 
@@ -128,6 +131,7 @@ let formatter doc =
   match Document.syntax doc with
   | (Dune | Cram | Ocamllex | Menhir) as s -> Error (Unsupported_syntax s)
   | Ocaml -> Ok (Ocaml (Document.uri doc))
+  | Mlx -> Ok (Mlx (Document.uri doc))
   | Reason ->
     Ok
       (Reason
diff --git a/ocaml-lsp-server/src/ocamlformat.mli b/ocaml-lsp-server/src/ocamlformat.mli
index 0d6edc6c1..186f692ba 100644
--- a/ocaml-lsp-server/src/ocamlformat.mli
+++ b/ocaml-lsp-server/src/ocamlformat.mli
@@ -1,6 +1,7 @@
 (** Generic formatting facility for OCaml and Reason sources.
 
-    Relies on [ocamlformat] for OCaml and [refmt] for reason *)
+    Relies on [ocamlformat] for OCaml, [ocamlformat-mlx] for OCaml.mlx, and
+    [refmt] for Reason. *)
 
 open Import
 
diff --git a/ocaml-lsp-server/src/typed_hole.ml b/ocaml-lsp-server/src/typed_hole.ml
index f34d39f1f..7062c1893 100644
--- a/ocaml-lsp-server/src/typed_hole.ml
+++ b/ocaml-lsp-server/src/typed_hole.ml
@@ -1,5 +1,23 @@
 open Import
 
+let syntax_repr = "_"
+let can_be_hole s = String.equal syntax_repr s
+
+(* the pattern matching below is taken and modified (minimally, to adapt the
+   return type) from [Query_commands.dispatch]'s [Construct] branch;
+
+   If we directly dispatched [Construct] command to merlin, we'd be doing
+   useless computations: we need info whether the expression at the cursor is a
+   hole, we don't need constructed expressions yet.
+
+   Ideally, merlin should return a callback [option], which is [Some] when the
+   context is applicable. *)
+let is_a_hole = function
+  | (_, Browse_raw.Module_expr { mod_desc = Tmod_hole; _ }) :: (_, _) :: _
+  | (_, Browse_raw.Expression { exp_desc = Texp_hole; _ }) :: _ -> true
+  | [] | (_, _) :: _ -> false
+;;
+
 let in_range range holes =
   match range with
   | None -> holes
diff --git a/ocaml-lsp-server/src/typed_hole.mli b/ocaml-lsp-server/src/typed_hole.mli
index eca4e3b87..03ee8d8ee 100644
--- a/ocaml-lsp-server/src/typed_hole.mli
+++ b/ocaml-lsp-server/src/typed_hole.mli
@@ -1,3 +1,19 @@
+(** This module should be used to work with typed holes. The main goal is to
+    hide syntactic representation of a typed hole, which may change in future *)
+
+(** checks whether the current string matches the syntax representation of a
+    typed hole *)
+val can_be_hole : string -> bool
+
+(** [is_a_hole nodes] checks whether the leaf node [1] is a typed hole
+
+    Note: this function is extracted from merlin sources handling [Construct]
+    command in [merlin/src/frontend/query_commands.ml]
+
+    [1] leaf node is the head of the list, as
+    [Mbrowse.t = (Env.t * Browse_raw.node) list]*)
+val is_a_hole : (Ocaml_typing.Env.t * Merlin_specific.Browse_raw.node) list -> bool
+
 val find
   :  range:Range.t option
   -> position:Position.t
diff --git a/ocaml-lsp-server/src/workspace_symbol.ml b/ocaml-lsp-server/src/workspace_symbol.ml
index a0251a6b1..55bc91638 100644
--- a/ocaml-lsp-server/src/workspace_symbol.ml
+++ b/ocaml-lsp-server/src/workspace_symbol.ml
@@ -365,9 +365,7 @@ let run server (state : State.t) (params : WorkspaceSymbolParams.t) =
          | Error `Cancelled -> assert false
          | Error (`Exn exn) -> Exn_with_backtrace.reraise exn)
     in
-    List.partition_map symbols_results ~f:(function
-      | Ok r -> Left r
-      | Error e -> Right e)
+    List.partition_result symbols_results
   in
   let+ () =
     match errors with
diff --git a/ocaml-lsp-server/test/e2e-new/code_lens.ml b/ocaml-lsp-server/test/e2e-new/code_lens.ml
new file mode 100644
index 000000000..efac601a1
--- /dev/null
+++ b/ocaml-lsp-server/test/e2e-new/code_lens.ml
@@ -0,0 +1,117 @@
+open Test.Import
+
+let change_config client params = Client.notification client (ChangeConfiguration params)
+
+let codelens client textDocument =
+  Client.request
+    client
+    (TextDocumentCodeLens
+       { textDocument; workDoneToken = None; partialResultToken = None })
+;;
+
+let json_of_codelens cs = `List (List.map ~f:CodeLens.yojson_of_t cs)
+
+let%expect_test "enable codelens for nested let bindings" =
+  let source =
+    {ocaml|
+let toplevel = "Hello"
+
+let func x = x
+
+let f x =
+  let y = 10 in
+  let z = 3 in
+  x + y + z
+|ocaml}
+  in
+  let req client =
+    let text_document = TextDocumentIdentifier.create ~uri:Helpers.uri in
+    let* () =
+      change_config
+        client
+        (DidChangeConfigurationParams.create
+           ~settings:(`Assoc [ "codelens", `Assoc [ "forNestedBindings", `Bool true ] ]))
+    in
+    let* resp_codelens_toplevel = codelens client text_document in
+    Test.print_result (json_of_codelens resp_codelens_toplevel);
+    Fiber.return ()
+  in
+  Helpers.test source req;
+  [%expect
+    {|
+    [
+      {
+        "command": { "command": "", "title": "int -> int" },
+        "range": {
+          "end": { "character": 11, "line": 8 },
+          "start": { "character": 0, "line": 5 }
+        }
+      },
+      {
+        "command": { "command": "", "title": "int" },
+        "range": {
+          "end": { "character": 12, "line": 6 },
+          "start": { "character": 2, "line": 6 }
+        }
+      },
+      {
+        "command": { "command": "", "title": "int" },
+        "range": {
+          "end": { "character": 11, "line": 7 },
+          "start": { "character": 2, "line": 7 }
+        }
+      },
+      {
+        "command": { "command": "", "title": "'a -> 'a" },
+        "range": {
+          "end": { "character": 14, "line": 3 },
+          "start": { "character": 0, "line": 3 }
+        }
+      },
+      {
+        "command": { "command": "", "title": "string" },
+        "range": {
+          "end": { "character": 22, "line": 1 },
+          "start": { "character": 0, "line": 1 }
+        }
+      }
+    ]
+    |}]
+;;
+
+let%expect_test "enable codelens (default settings disable it for nested let binding)" =
+  let source =
+    {ocaml|
+let x =
+  let y = 10 in
+  "Hello"
+
+let () = ()
+|ocaml}
+  in
+  let req client =
+    let text_document = TextDocumentIdentifier.create ~uri:Helpers.uri in
+    let* () =
+      change_config
+        client
+        (DidChangeConfigurationParams.create
+           ~settings:(`Assoc [ "codelens", `Assoc [ "enable", `Bool true ] ]))
+    in
+    let* resp_codelens_toplevel = codelens client text_document in
+    Test.print_result (json_of_codelens resp_codelens_toplevel);
+    Fiber.return ()
+  in
+  Helpers.test source req;
+  [%expect
+    {|
+    [
+      {
+        "command": { "command": "", "title": "string" },
+        "range": {
+          "end": { "character": 9, "line": 3 },
+          "start": { "character": 0, "line": 1 }
+        }
+      }
+    ]
+    |}]
+;;
diff --git a/ocaml-lsp-server/test/e2e-new/dune b/ocaml-lsp-server/test/e2e-new/dune
index ba58aa87a..a65361f61 100644
--- a/ocaml-lsp-server/test/e2e-new/dune
+++ b/ocaml-lsp-server/test/e2e-new/dune
@@ -44,6 +44,7 @@
     action_inline
     action_mark_remove
     code_actions
+    code_lens
     completion
     completions
     construct
@@ -51,6 +52,7 @@
     document_flow
     exit_notification
     for_ppx
+    hover
     hover_extended
     inlay_hints
     jump_to_typed_hole
diff --git a/ocaml-lsp-server/test/e2e-new/hover.ml b/ocaml-lsp-server/test/e2e-new/hover.ml
new file mode 100644
index 000000000..466352e9a
--- /dev/null
+++ b/ocaml-lsp-server/test/e2e-new/hover.ml
@@ -0,0 +1,43 @@
+open Test.Import
+
+let print_hover hover =
+  match hover with
+  | None -> print_endline "no hover response"
+  | Some hover ->
+    hover |> Hover.yojson_of_t |> Yojson.Safe.pretty_to_string ~std:false |> print_endline
+;;
+
+let hover client position =
+  Client.request
+    client
+    (TextDocumentHover
+       { HoverParams.position
+       ; textDocument = TextDocumentIdentifier.create ~uri:Helpers.uri
+       ; workDoneToken = None
+       })
+;;
+
+let%expect_test "object method call" =
+  let source =
+    {ocaml|
+let f (o : <  g : int -> unit >) = o#g 4
+|ocaml}
+  in
+  let position = Position.create ~line:1 ~character:38 in
+  let req client =
+    let* resp = hover client position in
+    let () = print_hover resp in
+    Fiber.return ()
+  in
+  Helpers.test source req;
+  [%expect
+    {|
+    {
+      "contents": { "kind": "plaintext", "value": "int -> unit" },
+      "range": {
+        "end": { "character": 38, "line": 1 },
+        "start": { "character": 35, "line": 1 }
+      }
+    }
+    |}]
+;;