diff --git a/src/client/opamClient.ml b/src/client/opamClient.ml
index bd3129f5331..83944d24ed0 100644
--- a/src/client/opamClient.ml
+++ b/src/client/opamClient.ml
@@ -1846,10 +1846,17 @@ let init
           OpamStd.Sys.exit_because `Aborted);
       try
         (* Create the content of ~/.opam/config *)
-        let repos = match repo with
-          | Some r -> [r.repo_name, (r.repo_url, r.repo_trust)]
-          | None -> OpamFile.InitConfig.repositories init_config
-        in
+        let repos =
+          let open OpamFile.Repos_config in
+          match repo with
+        | Some r ->
+            [r.repo_name,
+           {repoc_url = r.repo_url; repoc_trust = r.repo_trust}]
+        | None ->
+            List.map (fun (n,(u,t)) ->
+              n, {repoc_url = u; repoc_trust = t})
+            ( OpamFile.InitConfig.repositories init_config)
+          in
         let config =
           update_with_init_config
             OpamFile.Config.(with_opam_root_version root_version empty)
diff --git a/src/format/opamFile.ml b/src/format/opamFile.ml
index 1d94fa0a9b9..c4397cb650a 100644
--- a/src/format/opamFile.ml
+++ b/src/format/opamFile.ml
@@ -1386,7 +1386,7 @@ module ConfigSyntax = struct
   let internal = "config"
   let format_version = OpamVersion.of_string "2.1"
   let file_format_version = OpamVersion.of_string "2.0"
-  let root_version = OpamVersion.of_string "2.2"
+  let root_version = OpamVersion.of_string "2.4"
 
   let default_old_root_version = OpamVersion.of_string "2.1~~previous"
 
@@ -1957,13 +1957,17 @@ module InitConfig = struct
   include SyntaxFile(InitConfigSyntax)
 end
 
-module Repos_configSyntax = struct
+module Repos_config_LegacySyntax = struct
 
   let internal = "repos-config"
   let format_version = OpamVersion.of_string "2.0"
   let file_format_version = OpamVersion.of_string "2.0"
 
-  type t = (url * trust_anchors option) OpamRepositoryName.Map.t
+  type repo = {
+    repoc_url: url;
+    repoc_trust: trust_anchors option;
+  }
+  type t = repo OpamRepositoryName.Map.t
 
   let empty = OpamRepositoryName.Map.empty
 
@@ -1973,8 +1977,10 @@ module Repos_configSyntax = struct
       ((Pp.V.map_list ~depth:1 @@
         InitConfigSyntax.pp_repository_def -|
         Pp.pp
-          (fun ~pos:_ (name, url, ta) -> (name, (url, ta)))
-          (fun (name, (url, ta)) -> (name, url, ta))) -|
+          (fun ~pos:_ (name, repoc_url, repoc_trust) ->
+             (name, {repoc_url; repoc_trust}))
+          (fun (name, {repoc_url; repoc_trust}) ->
+             (name, repoc_url, repoc_trust))) -|
        Pp.of_pair "repository-url-list"
          OpamRepositoryName.Map.(of_list, bindings));
   ]
@@ -1991,6 +1997,122 @@ module Repos_configSyntax = struct
   let pp = pp_cond ()
 
 end
+
+module Repos_config_Legacy = struct
+  include Repos_config_LegacySyntax
+  include SyntaxFile(Repos_config_LegacySyntax)
+  module BestEffort = MakeBestEffort(Repos_config_LegacySyntax)
+end
+
+module Repos_configSyntax = struct
+
+  let internal = "repos-config"
+  let format_version = OpamVersion.of_string "2.1"
+  let file_format_version = OpamVersion.of_string "2.0"
+
+  type repo = {
+    repoc_url: url;
+    repoc_trust: trust_anchors option;
+  }
+  type t = repo OpamRepositoryName.Map.t
+
+  let empty = OpamRepositoryName.Map.empty
+
+  let pp_repo =
+    let empty = { repoc_url = OpamUrl.empty; repoc_trust = None } in
+    Pp.I.fields ~name:"repos-config-repo" ~empty [
+      "url", Pp.ppacc
+        (fun repoc_url t -> { t with repoc_url })
+        (fun { repoc_url; _ } -> repoc_url)
+        Pp.V.url;
+      "fingerprint", Pp.ppacc_opt
+        (fun fingerprints t ->
+           match t.repoc_trust with
+           | Some x -> { t with repoc_trust = Some { x with fingerprints }}
+           | None -> { t with repoc_trust = Some { fingerprints; quorum = 1}})
+        (fun t ->
+           match t.repoc_trust with
+           | Some {fingerprints; _} -> Some fingerprints
+           | None -> None)
+        (Pp.V.map_list ~depth:1 Pp.V.string);
+      "quorum",
+      Pp.ppacc_opt
+        (fun quorum t ->
+           match t.repoc_trust with
+           | Some x -> { t with repoc_trust = Some { x with quorum }}
+           | None -> { t with repoc_trust = Some { quorum; fingerprints = []}})
+        (fun t ->
+           match t.repoc_trust with
+           | Some {quorum; _} -> Some quorum
+           | None -> None)
+        Pp.V.int;
+    ]
+
+  let sections =
+    Pp.map_list
+      (Pp.I.section "repo"
+       -| Pp.pp ~name:"repo section"
+         (fun ~pos (name_opt, content) ->
+            let url = "repo", (Some pos, "missing URL") in
+            let name_repo = "repo", (Some pos, "missing repository name") in
+            let repo, errs = Pp.parse ~pos pp_repo content in
+            let nr, errs =
+              match name_opt with
+              | Some name ->
+                Some (OpamRepositoryName.of_string name, repo), errs
+              | None ->
+                None, name_repo::errs
+            in
+            if OpamUrl.equal OpamUrl.empty repo.repoc_url then
+              None, url::errs
+            else nr, errs
+         )
+         (function
+           | Some (name, repo), _ ->
+             Some (OpamRepositoryName.to_string name),
+             Pp.print pp_repo (repo, [])
+           | None, _ -> None, []))
+    -| Pp.pp ~name:"repositories"
+      (fun ~pos:_ repos ->
+         let repos, errs = List.split repos in
+         let repos = List.filter_map Fun.id repos in
+         let map = OpamRepositoryName.Map.of_list repos in
+         let errs = List.flatten errs in
+         map, errs)
+      (fun (map, _errs) ->
+         OpamRepositoryName.Map.bindings map
+         |> List.map (fun x -> Some x, []))
+
+  let pp_cond ?f ?condition () =
+    let name = internal in
+    let format_version = file_format_version in
+    Pp.I.map_file @@
+    Pp.I.check_opam_version ~optional:true ?f ~format_version () -|
+    Pp.I.opam_version ~format_version ~undefined:true () -|
+    Pp.I.partition (fun i -> match i.pelem with
+        | Section ({ section_kind={pelem="repo";_}; section_name=Some _; _ }) ->
+          false
+        | _ -> true)
+    -| Pp.map_pair
+      (* we need to keep the fields parser in order to display
+         unknown field errors *)
+      (let condition =
+         (* we need to propagate the BestEffort condition value *)
+         OpamStd.Option.map (fun cond -> fun () -> cond empty) condition
+       in
+       Pp.I.fields ~name ~empty:() []
+       -| Pp.I.show_errors ~name ?condition ()
+       -| Pp.pp (fun ~pos:_ _ -> ()) (fun () -> ())
+      )
+      (sections
+       -| Pp.I.show_errors ~name ?condition ())
+    -| Pp.pp (fun ~pos:_ (_, map) -> map)
+      (fun t -> (), t)
+
+  let pp = pp_cond ()
+
+end
+
 module Repos_config = struct
   include Repos_configSyntax
   include SyntaxFile(Repos_configSyntax)
diff --git a/src/format/opamFile.mli b/src/format/opamFile.mli
index 45c51ef8320..445441d8554 100644
--- a/src/format/opamFile.mli
+++ b/src/format/opamFile.mli
@@ -1028,8 +1028,22 @@ module Repo_config_legacy : sig
   include IO_FILE with type t := t
 end
 
+module Repos_config_Legacy: sig
+  type repo = {
+    repoc_url: url;
+    repoc_trust: trust_anchors option;
+  }
+  type t = repo OpamRepositoryName.Map.t
+  include IO_FILE with type t := t
+  module BestEffort: BestEffortRead with type t := t
+end
+
 module Repos_config: sig
-  type t = (url * trust_anchors option) OpamRepositoryName.Map.t
+  type repo = {
+    repoc_url: url;
+    repoc_trust: trust_anchors option;
+  }
+  type t = repo OpamRepositoryName.Map.t
   include IO_FILE with type t := t
   module BestEffort: BestEffortRead with type t := t
 end
diff --git a/src/state/opamFormatUpgrade.ml b/src/state/opamFormatUpgrade.ml
index f488f661fb9..afcd2b887ec 100644
--- a/src/state/opamFormatUpgrade.ml
+++ b/src/state/opamFormatUpgrade.ml
@@ -352,7 +352,7 @@ let opam_file_from_1_2_to_2_0 ?filename opam =
 
 (* Global state changes that need to be propagated *)
 let gtc_none = { gtc_repo = false; gtc_switch = false }
-let _gtc_repo = { gtc_repo = true; gtc_switch = false }
+let gtc_repo = { gtc_repo = true; gtc_switch = false }
 let _gtc_switch = { gtc_repo = false; gtc_switch = true }
 let _gtc_both = { gtc_repo = true; gtc_switch = true }
 
@@ -770,7 +770,10 @@ let from_1_3_dev7_to_2_0_alpha ~on_the_fly:_ root conf =
   in
   OpamFile.Repos_config.write (OpamPath.repos_config root)
     (OpamRepositoryName.Map.of_list
-       (List.map (fun (_, r, u) -> r, (u,None)) prio_repositories));
+       (List.map (fun (_, repo_name, repoc_url) ->
+            repo_name,
+            OpamFile.Repos_config.{repoc_url; repoc_trust = None})
+           prio_repositories));
   let prio_repositories =
     List.stable_sort (fun (prio1, _, _) (prio2, _, _) -> prio2 - prio1)
       prio_repositories
@@ -1147,6 +1150,32 @@ let v2_2 = OpamVersion.of_string "2.2"
 
 let from_2_2_beta_to_2_2 ~on_the_fly:_ _ conf = conf, gtc_none
 
+let v2_3 = OpamVersion.of_string "2.3"
+
+let from_2_2_to_2_3 ~on_the_fly:_ _ conf = conf, gtc_none
+
+let v2_4 = OpamVersion.of_string "2.4"
+
+let from_2_3_to_2_4 ~on_the_fly root conf =
+  (if on_the_fly then
+     OpamConsole.error_and_exit `Internal_error
+       "This 2.4 upgrade should be a hard upgrade");
+  let f = OpamPath.repos_config root in
+  OpamStd.Option.iter (fun old_repoconfig ->
+      let repos =
+        OpamRepositoryName.Map.map (fun old_repo ->
+            let OpamFile.Repos_config_Legacy.{repoc_url; repoc_trust} =
+              old_repo
+            in
+            OpamFile.Repos_config.{repoc_url; repoc_trust})
+          old_repoconfig
+      in
+      OpamFile.Repos_config.write f repos)
+    (OpamFile.Repos_config_Legacy.BestEffort.read_opt
+       (OpamFile.make
+          (OpamFile.filename f)));
+  conf, gtc_repo
+
 (* To add an upgrade layer
    * If it is a light upgrade, returns as second element if the repo or switch
      need an light upgrade with `gtc_*` values.
@@ -1156,7 +1185,7 @@ let from_2_2_beta_to_2_2 ~on_the_fly:_ _ conf = conf, gtc_none
 
 let latest_version = OpamFile.Config.root_version
 
-let latest_hard_upgrade = (* to *) v2_0_beta5
+let latest_hard_upgrade = (* to *) v2_4
 
 (* intermediate roots that need a hard upgrade when upgrading from them *)
 let v2_1_intermediate_roots = [
@@ -1218,9 +1247,11 @@ let as_necessary ?reinit requested_lock global_lock root config =
     let is_2_1_intermediate_root =
       List.exists (OpamVersion.equal root_version) v2_1_intermediate_roots
     in
+    (* As last hard upgrade is > 2.1~rc, we no more need that selection.
     let latest_hard_upgrade =
       if is_2_1_intermediate_root then v2_1_rc else latest_hard_upgrade
     in
+    *)
     (if is_2_1_intermediate_root then [
         v2_1_alpha,  from_2_0_to_2_1_alpha;
         v2_1_alpha2, from_2_1_alpha_to_2_1_alpha2;
@@ -1244,6 +1275,8 @@ let as_necessary ?reinit requested_lock global_lock root config =
       v2_2_alpha,  from_2_1_to_2_2_alpha;
       v2_2_beta,   from_2_2_alpha_to_2_2_beta;
       v2_2,        from_2_2_beta_to_2_2;
+      v2_3,        from_2_2_to_2_3;
+      v2_4,        from_2_3_to_2_4;
     ]
     |> List.filter (fun (v,_) ->
         OpamVersion.compare root_version v < 0)
diff --git a/src/state/opamRepositoryState.ml b/src/state/opamRepositoryState.ml
index b7e8ff69a64..66cd8be6ea5 100644
--- a/src/state/opamRepositoryState.ml
+++ b/src/state/opamRepositoryState.ml
@@ -164,10 +164,10 @@ let load lock_kind gt =
          load with best-effort (read-only)"
       (OpamVersion.to_string (OpamFile.Config.opam_root_version gt.config))
       (OpamVersion.to_string (OpamFile.Config.root_version));
-  let mk_repo name (url, ta) = {
+  let mk_repo name OpamFile.Repos_config.{repoc_url; repoc_trust} = {
     repo_name = name;
-    repo_url = url;
-    repo_trust = ta;
+    repo_url = repoc_url;
+    repo_trust = repoc_trust;
   } in
   let repositories = OpamRepositoryName.Map.mapi mk_repo repos_map in
   let repos_tmp_root = lazy (OpamFilename.mk_tmp_dir ()) in
@@ -280,7 +280,9 @@ let write_config rt =
   OpamFile.Repos_config.write (OpamPath.repos_config rt.repos_global.root)
     (OpamRepositoryName.Map.filter_map (fun _ r ->
          if r.repo_url = OpamUrl.empty then None
-         else Some (r.repo_url, r.repo_trust))
+         else
+           Some OpamFile.Repos_config.{ repoc_url = r.repo_url;
+                                        repoc_trust = r.repo_trust})
         rt.repositories)
 
 let check_last_update () =
diff --git a/tests/reftests/dune.inc b/tests/reftests/dune.inc
index 479710810d0..e2b0a6c3c08 100644
--- a/tests/reftests/dune.inc
+++ b/tests/reftests/dune.inc
@@ -1931,27 +1931,6 @@
    %{targets}
    (run ./run.exe %{exe:../../src/client/opamMain.exe.exe} %{dep:upgrade-format.test} %{read-lines:testing-env}))))
 
-(rule
- (alias reftest-upgrade-two-point-o)
- (enabled_if (and  (or (<> %{env:TESTALL=1} 0) (= %{env:TESTN0REP0=0} 1))))
- (action
-  (diff upgrade-two-point-o.test upgrade-two-point-o.out)))
-
-(alias
- (name reftest)
- (enabled_if (and  (or (<> %{env:TESTALL=1} 0) (= %{env:TESTN0REP0=0} 1))))
- (deps (alias reftest-upgrade-two-point-o)))
-
-(rule
- (targets upgrade-two-point-o.out)
- (deps root-N0REP0)
- (enabled_if (and  (or (<> %{env:TESTALL=1} 0) (= %{env:TESTN0REP0=0} 1))))
- (package opam)
- (action
-  (with-stdout-to
-   %{targets}
-   (run ./run.exe %{exe:../../src/client/opamMain.exe.exe} %{dep:upgrade-two-point-o.test} %{read-lines:testing-env}))))
-
 (rule
  (alias reftest-upgrade)
  (enabled_if (and  (or (<> %{env:TESTALL=1} 0) (= %{env:TESTN0REP0=0} 1))))
diff --git a/tests/reftests/init-ocaml-eval-variables.unix.test b/tests/reftests/init-ocaml-eval-variables.unix.test
index 0cd6ccdfee3..ea4b9900991 100644
--- a/tests/reftests/init-ocaml-eval-variables.unix.test
+++ b/tests/reftests/init-ocaml-eval-variables.unix.test
@@ -7,6 +7,9 @@ let opamroot = Sys.getenv "OPAMROOT"
 let opam_version = Printf.sprintf "opam-version: %S"
 let opam_version_2_0 = opam_version "2.0"
 let opam_version_2_1 = opam_version "2.1"
+let repos_config = Printf.sprintf {|opam-version: "2.0"
+repositories: "default" {"file://%s/REPO"}
+|} (Sys.getenv "BASEDIR")
 let repo = {|repositories: "default"|}
 let depext = {|
 depext: true
@@ -33,6 +36,10 @@ let _ =
   let content = get_files Sys.argv.(1) in
   let fd = open_out name in
   List.iter (fun l -> output_string fd (l^"\n")) content;
+  close_out fd;
+  let rcname = Filename.concat (Filename.concat opamroot "repo") "repos-config" in
+  let fd = open_out rcname in
+  output_string fd repos_config;
   close_out fd
 ### rm -rf "$OPAMROOT"
 ### ::::::::::::::::::::::::::
@@ -55,15 +62,24 @@ eval-variables: [sys-ocaml-version ["ocamlc" "-vnum"] "OCaml version present on
 ### # rw global state
 ### opam option jobs=4 | " ${OPAMROOTVERSION}($|,)" -> " current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         Light config upgrade, from 2.0 to current
+FMT_UPG                         Hard config upgrade, from 2.0 to current
 This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.0 to version current which can't be reverted.
 You may want to back it up before going further.
 
-Continue? [Y/n] y
+Perform the update and continue? [Y/n] y
 [NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
            opam option jobs=1 --global
 Format upgrade done.
-Set to '4' the field jobs in global configuration
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/REPO
+Update done, please now retry your command.
+# Return code 10 #
 ### opam-cat $OPAMROOT/config | grep eval-variables
 eval-variables: [[sys-ocaml-system ["sh" "-c" "ocamlc -config 2>/dev/null | tr -d '/r' | sed -n -e 's/system: //p'"] "Target system of the OCaml compiler present on your system"] [sys-ocaml-libc ["sh" "-c" "ocamlc -config 2>/dev/null | tr -d '/r' | sed -n -e 's/^os_type: Win32/msvc/p;s/^os_type: .*/libc/p'"] "Host C Runtime Library type of the OCaml compiler present on your system"] [sys-ocaml-cc ["sh" "-c" "ocamlc -config 2>/dev/null | tr -d '/r' | sed -n -e 's/^ccomp_type: //p'"] "Host C Compiler type of the OCaml compiler present on your system"] [sys-ocaml-arch ["sh" "-c" "ocamlc -config 2>/dev/null | tr -d '/r' | sed -n -e 's/i386/i686/;s/amd64/x86_64/;s/^architecture: //p'"] "Target architecture of the OCaml compiler present on your system"] [sys-ocaml-version ["ocamlc" "-vnum"] "OCaml version present on your system independently of opam, if any"]]
 ### rm "$OPAMROOT/config"
@@ -76,14 +92,23 @@ eval-variables: [[sys-ocaml-version ["ocamlc" "-vnum"] "OCaml version present on
 ### # rw global state
 ### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> " current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         Light config upgrade, from 2.1 to  current
+FMT_UPG                         Hard config upgrade, from 2.1 to  current
 This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1 to version  current which can't be reverted.
 You may want to back it up before going further.
 
-Continue? [Y/n] y
+Perform the update and continue? [Y/n] y
 [NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
            opam option jobs=1 --global
 Format upgrade done.
-Set to '4' the field jobs in global configuration
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/REPO
+Update done, please now retry your command.
+# Return code 10 #
 ### opam-cat $OPAMROOT/config | grep eval-variables
 eval-variables: [[sys-ocaml-system ["sh" "-c" "ocamlc -config 2>/dev/null | tr -d '/r' | sed -n -e 's/system: //p'"] "Target system of the OCaml compiler present on your system"] [sys-ocaml-version ["ocamlc" "-vnum"] "OCaml version present on your system independently of opam, if any"] [sys-ocaml-arch ["sh" "-c" "ocamlc -config 2>/dev/null | tr -d '/r' | sed -n -e 's/i386/i686/;s/amd64/x86_64/;s/^architecture: //p'"] "Target architecture of the OCaml compiler present on your system"] [sys-ocaml-cc ["sh" "-c" "ocamlc -config 2>/dev/null | tr -d '/r' | sed -n -e 's/^ccomp_type: //p'"] "Host C Compiler type of the OCaml compiler present on your system"] [sys-ocaml-libc ["sh" "-c" "ocamlc -config 2>/dev/null | tr -d '/r' | sed -n -e 's/^os_type: Win32/msvc/p;s/^os_type: .*/libc/p'"] "Host C Runtime Library type of the OCaml compiler present on your system"]]
diff --git a/tests/reftests/init.test b/tests/reftests/init.test
index d02ba15037f..67fb42378b5 100644
--- a/tests/reftests/init.test
+++ b/tests/reftests/init.test
@@ -242,7 +242,9 @@ wrap-install-commands: ["%{hooks}%/a-script.sh" "wrap-install"]
 wrap-remove-commands: ["%{hooks}%/a-script.sh" "wrap-remove"]
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "norepo" {"file://${BASEDIR}/REPO"}
+repo "norepo" {
+url: "file://${BASEDIR}/REPO"
+}
 ### sh $OPAMROOT/opam-init/hooks/a-script.sh test
 script test launched STOP i repeat STOP script test launched
 ### :: partially configured opamrc ::
@@ -296,4 +298,6 @@ wrap-install-commands: ["%{hooks}%/a-script.sh" "wrap-install"]
 wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "norepo" {"file://${BASEDIR}/REPO"}
+repo "norepo" {
+url: "file://${BASEDIR}/REPO"
+}
diff --git a/tests/reftests/opamroot-versions.test b/tests/reftests/opamroot-versions.test
index 059becf1a75..d66fb1d948e 100644
--- a/tests/reftests/opamroot-versions.test
+++ b/tests/reftests/opamroot-versions.test
@@ -12,7 +12,7 @@ installed-switches: "foo"
 switch: "foo"
 |}
 let neant = "neant: 0"
-let repo = {|repositories: [ "default" {"file:///${BASEDIR/dontexist"} ]|}
+let repo = Printf.sprintf {|repo "default" {url:"file://%s/dontexist"}|} (Sys.getenv "BASEDIR")
 let switch_config = {|synopsis: "foo"|}
 let _ =
   let configs =
@@ -29,7 +29,7 @@ let _ =
        ])
   in
   let files = [
-    "repos-config", [ repo ];
+    "repos-config", [ opam_version "2.0"; repo ];
     "switch-config", [ opam_version "2.0"; switch_config ];
   ] @ configs
   in
@@ -80,7 +80,7 @@ GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 [WARNING] Errors in ${BASEDIR}/OPAM/repo/repos-config, some fields have been ignored:
-            - At ${BASEDIR}/OPAM/repo/repos-config:2:0-2:8::
+            - At ${BASEDIR}/OPAM/repo/repos-config:3:0-3:8::
               Invalid field neant
 
 RSTATE                          Cache found
@@ -91,7 +91,7 @@ GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 [WARNING] No switch is currently set, perhaps you meant '--set-default'?
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 [WARNING] Errors in ${BASEDIR}/OPAM/repo/repos-config, some fields have been ignored:
-            - At ${BASEDIR}/OPAM/repo/repos-config:2:0-2:8::
+            - At ${BASEDIR}/OPAM/repo/repos-config:3:0-3:8::
               Invalid field neant
 
 RSTATE                          Cache found
@@ -261,7 +261,7 @@ GSTATE                          root version (4.8) is greater than running binar
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 GSTATE                          root version (4.8) is greater than running binary's current; load with best-effort (read-only)
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
-FORMAT                          File errors in ${BASEDIR}/OPAM/repo/repos-config, ignored fields: At ${BASEDIR}/OPAM/repo/repos-config:2:0-2:8::
+FORMAT                          File errors in ${BASEDIR}/OPAM/repo/repos-config, ignored fields: At ${BASEDIR}/OPAM/repo/repos-config:3:0-3:8::
 Invalid field neant
 RSTATE                          root version (4.8) is greater than running binary's current; load with best-effort (read-only)
 RSTATE                          Cache found
@@ -568,13 +568,15 @@ let invariant_sw_sys_comp = {|invariant: ["i-am-sys-compiler"]|}
 let root_version =  Printf.sprintf "opam-root-version: %S"
 let synopsis = Printf.sprintf "synopsis: %S"
 let opam_root = Printf.sprintf "opam-root: %S" opamroot
-let repos_config = Printf.sprintf {|
-opam-version: "2.0"
-repositories: "default" {"file://%s/default"}
-|} (Sys.getenv "BASEDIR" |> String.map (function '\\' -> '/' | c -> c))
+let repos_config v = {|opam-version: "2.0"
+|} ^
+  Printf.sprintf
+  (if v < 2.4 then {|repositories: ["default" {"file://%s/default"}]|}
+   else {|repo "default" {url:"file://%s/default"}|})
+  (Sys.getenv "BASEDIR" |> String.map (function '\\' -> '/' | c -> c))
 let opam_20 =
   [ "config", [ opam_version_2_0; repo; installed_switches; eval; default_compiler ];
-    "repo/repos-config", [ repos_config ];
+    "repo/repos-config", [ repos_config 2.0 ];
     "default/.opam-switch/switch-config", [ opam_version_2_0; synopsis "default switch" ];
     "default/.opam-switch/switch-state", [ opam_version_2_0; sw_state_default ];
     "sw-comp/.opam-switch/switch-config", [ opam_version_2_0; synopsis "switch with compiler" ];
@@ -587,7 +589,7 @@ let opam_20 =
   ]
 let opam_21alpha =
   [ "config", [ opam_version_2_0; repo; installed_switches; eval; default_compiler ];
-    "repo/repos-config", [ repos_config ];
+    "repo/repos-config", [ repos_config 2.1 ];
     "default/.opam-switch/switch-config", [ opam_version_2_1; synopsis "default switch"; invariant_default ];
     "default/.opam-switch/switch-state", [ opam_version_2_0; sw_state_default ];
     "sw-comp/.opam-switch/switch-config", [ opam_version_2_1; synopsis "switch with compiler"; invariant_sw_comp ];
@@ -600,7 +602,7 @@ let opam_21alpha =
   ]
 let opam_21alpha2 =
   [ "config", [ opam_version_2_1; repo; installed_switches; eval; default_compiler; depext; ];
-    "repo/repos-config", [ repos_config ];
+    "repo/repos-config", [ repos_config 2.1 ];
     "default/.opam-switch/switch-config", [ opam_version_2_1; synopsis "default switch"; invariant_default ];
     "default/.opam-switch/switch-state", [ opam_version_2_0; sw_state_default ];
     "sw-comp/.opam-switch/switch-config", [ opam_version_2_1; synopsis "switch with compiler"; invariant_sw_comp ];
@@ -614,7 +616,7 @@ let opam_21alpha2 =
 let opam_21rc =
   let root_version =  {|opam-root-version: "2.1~rc"|} in
   [ "config", [ opam_version_2_0; root_version; repo; installed_switches; eval; default_compiler; default_invariant; depext ];
-    "repo/repos-config", [ repos_config ];
+    "repo/repos-config", [ repos_config 2.1 ];
     "default/.opam-switch/switch-config", [ opam_version_2_0; synopsis "default switch"; invariant_default ];
     "default/.opam-switch/switch-state", [ opam_version_2_0; sw_state_default ];
     "sw-comp/.opam-switch/switch-config", [ opam_version_2_0; synopsis "switch with compiler"; invariant_sw_comp ];
@@ -627,7 +629,7 @@ let opam_21rc =
   ]
 let opam_current v =
   [ "config", [ opam_version_2_0; root_version v; repo; installed_switches; eval; default_compiler; default_invariant; depext ];
-    "repo/repos-config", [ repos_config ];
+    "repo/repos-config", [ repos_config (float_of_string (String.sub v 0 3)) ];
     "default/.opam-switch/switch-config", [ opam_version_2_0; synopsis "default switch"; invariant_default ];
     "default/.opam-switch/switch-state", [ opam_version_2_0; sw_state_default ];
     "sw-comp/.opam-switch/switch-config", [ opam_version_2_0; synopsis "switch with compiler"; invariant_sw_comp ];
@@ -687,18 +689,33 @@ No configuration file found, using built-in defaults.
 ### :V:1:a: From 2.0 root, global
 ### ocaml generate.ml 2.0
 ### # ro global state
-### opam option jobs | "${OPAMROOTVERSION}$" -> "current"
+### opam option jobs | "${OPAMROOTVERSION}" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.0 to current
-FMT_UPG                         Format upgrade done
-### # ro global state, ro repo state, ro switch state
-### opam list | "${OPAMROOTVERSION}$" -> "current"
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.0 to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.0 to version current, which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.0 to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
+### # ro global state, ro repo state, ro switch state
+### opam list | "${OPAMROOTVERSION}$" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ sw-sys-comp
 STATE                           Inferred invariant: from base packages { i-am-sys-compiler.1 }, (roots { i-am-sys-compiler.1 }) => ["i-am-sys-compiler"]
 STATE                           Switch state loaded in 0.000s
@@ -710,8 +727,6 @@ i-am-sys-compiler    1           One-line description
 ### # ro global state, ro repo state, rw switch state
 ### opam install i-am-another-package --switch sw-comp | "${OPAMROOTVERSION}$" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.0 to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ sw-comp
@@ -731,34 +746,31 @@ Done.
 ### # rw global state
 ### opam switch sw-comp | " ${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.0 tocurrent
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.0 to versioncurrent which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
-Format upgrade done.
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ sw-comp
 STATE                           Switch state loaded in 0.000s
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables | grep -v eval-variables:
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
+default-invariant: ["ocaml" {>= "4.05.0"}]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 installed-switches: ["sw-comp" "sw-sys-comp" "default"]
 opam-root-version: current
 opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat $OPAMROOT/sw-comp/.opam-switch/switch-config
 invariant: ["i-am-compiler" {>= "2"}]
 opam-version: "2.0"
@@ -775,25 +787,32 @@ roots: ["i-am-another-package.2" "i-am-compiler.2" "i-am-package.2"]
 ### :V:1:b: From 2.0 root, local
 ### ocaml generate.ml 2.0 local
 ### # ro global state, ro repo state, ro switch state
-### opam list | "${OPAMROOTVERSION}$" -> "current"
+### opam list | "${OPAMROOTVERSION}" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.0 to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.0 to version current, which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.0 to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
-STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
-STATE                           Inferred invariant: from base packages { i-am-sys-compiler.2 }, (roots { i-am-sys-compiler.2 }) => ["i-am-sys-compiler"]
-STATE                           Switch state loaded in 0.000s
-# Packages matching: installed
-# Name            # Installed # Synopsis
-i-am-sys-compiler 2           One-line description
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### # ro global state, ro repo state, rw switch state
 ### OPAMSYSCOMP=2
 ### opam install i-am-package | "${OPAMROOTVERSION}$" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.0 to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
@@ -812,22 +831,14 @@ Done.
 ### # rw global state
 ### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.0 to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.0 to version current which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables | grep -v eval-variables:
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
+default-invariant: ["ocaml" {>= "4.05.0"}]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 installed-switches: ["sw-sys-comp" "sw-comp" "${BASEDIR}" "default"]
 jobs: 4
 opam-root-version: current
@@ -835,9 +846,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -856,24 +872,31 @@ roots: ["i-am-package.2" "i-am-sys-compiler.2"]
 ### :V:1:c: From 2.0 root, local unknown from config
 ### ocaml generate.ml 2.0 orphaned
 ### # ro global state, ro repo state, ro switch state
-### opam list | "${OPAMROOTVERSION}$" -> " current"
+### opam list | "${OPAMROOTVERSION}" -> " current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.0 to  current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.0 to version  current, which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.0 to  current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
-STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
-STATE                           Inferred invariant: from base packages { i-am-sys-compiler.2 }, (roots { i-am-sys-compiler.2 }) => ["i-am-sys-compiler"]
-STATE                           Switch state loaded in 0.000s
-# Packages matching: installed
-# Name            # Installed # Synopsis
-i-am-sys-compiler 2           One-line description
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### # ro global state, ro repo state, rw switch state
 ### opam install i-am-package | "${OPAMROOTVERSION}$" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.0 to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
@@ -892,22 +915,14 @@ Done.
 ### # rw global state
 ### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.0 to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.0 to version current which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables | grep -v eval-variables:
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
+default-invariant: ["ocaml" {>= "4.05.0"}]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 installed-switches: ["sw-sys-comp" "sw-comp" "default"]
 jobs: 4
 opam-root-version: current
@@ -915,9 +930,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -984,7 +1004,9 @@ swh-fallback: false
 switch: "sw-sys-comp"
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -1005,20 +1027,25 @@ roots: ["i-am-package.2" "i-am-sys-compiler.2"]
 No configuration file found, using built-in defaults.
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 [WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.0 to current
+FMT_UPG                         Hard config upgrade, from 2.0 to current
 This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.0 to version current which can't be reverted.
 You may want to back it up before going further.
 
-Continue? [Y/n] y
+Perform the update and continue? [Y/n] y
 [NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
            opam option jobs=1 --global
 Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
 
 <><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
 [default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### opam switch --short
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 ${BASEDIR}
@@ -1129,7 +1156,9 @@ wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "
 wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat $OPAMROOT/sw-comp/.opam-switch/switch-config
 invariant: ["i-am-compiler"]
 opam-version: "2.0"
@@ -1202,7 +1231,9 @@ wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "
 wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -1278,7 +1309,9 @@ wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "
 wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -1344,7 +1377,9 @@ swh-fallback: false
 switch: "sw-sys-comp"
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -1497,7 +1532,9 @@ wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "
 wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat $OPAMROOT/sw-comp/.opam-switch/switch-config
 invariant: ["i-am-compiler"]
 opam-version: "2.0"
@@ -1572,7 +1609,9 @@ wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "
 wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -1650,7 +1689,9 @@ wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "
 wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -1716,7 +1757,9 @@ swh-fallback: false
 switch: "sw-sys-comp"
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -1794,16 +1837,31 @@ wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "ma
 ### # ro global state
 ### opam option jobs | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1~rc to current
-FMT_UPG                         Format upgrade done
-### # ro global state, ro repo state, ro switch state
-### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.1~rc to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1~rc to version current which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1~rc to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
+### # ro global state, ro repo state, ro switch state
+### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ sw-sys-comp
 STATE                           Switch state loaded in 0.000s
 # Packages matching: installed
@@ -1814,8 +1872,6 @@ i-am-sys-compiler    1           One-line description
 ### # ro global state, ro repo state, rw switch state
 ### opam install i-am-another-package --switch sw-comp | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1~rc to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ sw-comp
@@ -1832,15 +1888,6 @@ Done.
 ### # rw global state
 ### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.1~rc to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1~rc to version current which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables | grep -v eval-variables:
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -1848,7 +1895,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 installed-switches: ["sw-sys-comp" "sw-comp" "default"]
 jobs: 4
 opam-root-version: current
@@ -1856,9 +1903,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat $OPAMROOT/sw-comp/.opam-switch/switch-config
 invariant: ["i-am-compiler"]
 opam-version: "2.0"
@@ -1872,21 +1924,29 @@ roots: ["i-am-another-package.2" "i-am-compiler.2" "i-am-package.2"]
 ### ocaml generate.ml 2.1~rc local
 ### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1~rc to current
-FMT_UPG                         Format upgrade done
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.1~rc to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1~rc to version current which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
-STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
-STATE                           Switch state loaded in 0.000s
-# Packages matching: installed
-# Name            # Installed # Synopsis
-i-am-sys-compiler 2           One-line description
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### # ro global state, ro repo state, rw switch state
 ### opam install i-am-package | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1~rc to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
@@ -1904,15 +1964,6 @@ Done.
 ### # rw global state
 ### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.1~rc to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1~rc to version current which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables | grep -v eval-variables:
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -1920,7 +1971,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 installed-switches: ["sw-sys-comp" "sw-comp" "${BASEDIR}" "default"]
 jobs: 4
 opam-root-version: current
@@ -1928,9 +1979,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -1946,21 +2002,29 @@ roots: ["i-am-package.2" "i-am-sys-compiler.2"]
 ### ocaml generate.ml 2.1~rc local
 ### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1~rc to current
-FMT_UPG                         Format upgrade done
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.1~rc to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1~rc to version current which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
-STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
-STATE                           Switch state loaded in 0.000s
-# Packages matching: installed
-# Name            # Installed # Synopsis
-i-am-sys-compiler 2           One-line description
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### # ro global state, ro repo state, rw switch state
 ### opam install i-am-package | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1~rc to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
@@ -1978,15 +2042,6 @@ Done.
 ### # rw global state
 ### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.1~rc to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1~rc to version current which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables | grep -v eval-variables:
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -1994,7 +2049,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 installed-switches: ["sw-sys-comp" "sw-comp" "${BASEDIR}" "default"]
 jobs: 4
 opam-root-version: current
@@ -2002,9 +2057,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -2065,7 +2125,9 @@ swh-fallback: false
 switch: "sw-sys-comp"
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -2082,20 +2144,25 @@ roots: ["i-am-package.2" "i-am-sys-compiler.2"]
 No configuration file found, using built-in defaults.
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 [WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.1~rc to current
+FMT_UPG                         Hard config upgrade, from 2.1~rc to current
 This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1~rc to version current which can't be reverted.
 You may want to back it up before going further.
 
-Continue? [Y/n] y
+Perform the update and continue? [Y/n] y
 [NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
            opam option jobs=1 --global
 Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
 
 <><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
 [default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### opam switch --short
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 ${BASEDIR}
@@ -2132,18 +2199,33 @@ wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "ma
 ### :V:5:a: From 2.1 root, global
 ### ocaml generate.ml 2.1
 ### # ro global state
-### opam option jobs | "${OPAMROOTVERSION}$" -> "current"
+### opam option jobs | "${OPAMROOTVERSION}" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1 to current
-FMT_UPG                         Format upgrade done
-### # ro global state, ro repo state, ro switch state
-### opam list | "${OPAMROOTVERSION}$" -> "current"
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.1 to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1 to version current, which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1 to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
+### # ro global state, ro repo state, ro switch state
+### opam list | "${OPAMROOTVERSION}$" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ sw-sys-comp
 STATE                           Switch state loaded in 0.000s
 # Packages matching: installed
@@ -2154,8 +2236,6 @@ i-am-sys-compiler    1           One-line description
 ### # ro global state, ro repo state, rw switch state
 ### opam install i-am-another-package --switch sw-comp | "${OPAMROOTVERSION}$" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1 to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ sw-comp
@@ -2172,8 +2252,6 @@ Done.
 ### # ro global state, rw repo state
 ### opam repo add root-config ./root-config | "${OPAMROOTVERSION}$" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1 to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 [root-config] Initialised
@@ -2183,15 +2261,6 @@ RSTATE                          Cache found
 ### # rw global state
 ### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.1 to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1 to version current which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables | grep -v eval-variables:
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -2199,7 +2268,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 installed-switches: ["sw-sys-comp" "sw-comp" "default"]
 jobs: 4
 opam-root-version: current
@@ -2207,9 +2276,17 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: ["default" {"file://${BASEDIR}/default"} "root-config" {"file://${BASEDIR}/root-config"}]
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
+repo "root-config" {
+url: "file://${BASEDIR}/root-config"
+}
 ### opam-cat $OPAMROOT/sw-comp/.opam-switch/switch-config
 invariant: ["i-am-compiler"]
 opam-version: "2.0"
@@ -2223,20 +2300,28 @@ roots: ["i-am-another-package.2" "i-am-compiler.2" "i-am-package.2"]
 ### ocaml generate.ml 2.1 local
 ### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1 to current
-FMT_UPG                         Format upgrade done
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.1 to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1 to version current which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
-STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
-STATE                           Switch state loaded in 0.000s
-# Packages matching: installed
-# Name            # Installed # Synopsis
-i-am-sys-compiler 2           One-line description
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### opam install i-am-package | "${OPAMROOTVERSION}$" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1 to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
@@ -2254,15 +2339,6 @@ Done.
 ### # rw global state
 ### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.1 to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1 to version current which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables | grep -v eval-variables:
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -2270,7 +2346,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 installed-switches: ["sw-sys-comp" "sw-comp" "${BASEDIR}" "default"]
 jobs: 4
 opam-root-version: current
@@ -2278,9 +2354,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -2296,21 +2377,29 @@ roots: ["i-am-package.2" "i-am-sys-compiler.2"]
 ### # ro global state, ro repo state, ro switch state
 ### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1 to current
-FMT_UPG                         Format upgrade done
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.1 to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1 to version current which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
-STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
-STATE                           Switch state loaded in 0.000s
-# Packages matching: installed
-# Name            # Installed # Synopsis
-i-am-sys-compiler 2           One-line description
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### # ro global state, ro repo state, rw switch state
 ### opam install i-am-package | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1 to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
@@ -2327,15 +2416,6 @@ Done.
 ### # rw global state
 ### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.1 to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1 to version current which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables | grep -v eval-variables:
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -2343,7 +2423,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 installed-switches: ["sw-sys-comp" "sw-comp" "${BASEDIR}" "default"]
 jobs: 4
 opam-root-version: current
@@ -2351,9 +2431,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -2367,23 +2452,31 @@ roots: ["i-am-package.2" "i-am-sys-compiler.2"]
 ### :V:5:d: Upgraded root and local 2.1 switch not recorded
 ### ocaml generate.ml 2.1 orphaned 2.1
 ### # ro global state, ro repo state, ro switch state
-### opam list | "${OPAMROOTVERSION}$" -> "current"
+### opam list | "${OPAMROOTVERSION}" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.1 to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1 to version current, which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1 to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
-STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
-STATE                           Switch state loaded in 0.000s
-# Packages matching: installed
-# Name            # Installed # Synopsis
-i-am-sys-compiler 2           One-line description
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### # ro global state, ro repo state, rw switch state
 ### opam install i-am-package | "${OPAMROOTVERSION}$" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.1 to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
@@ -2400,15 +2493,6 @@ Done.
 ### # rw global state
 ### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.1 to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1 to version current which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables | grep -v eval-variables:
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -2416,7 +2500,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 installed-switches: ["sw-sys-comp" "sw-comp" "default"]
 jobs: 4
 opam-root-version: current
@@ -2424,9 +2508,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -2443,20 +2532,25 @@ roots: ["i-am-package.2" "i-am-sys-compiler.2"]
 No configuration file found, using built-in defaults.
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 [WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.1 to current
+FMT_UPG                         Hard config upgrade, from 2.1 to current
 This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.1 to version current which can't be reverted.
 You may want to back it up before going further.
 
-Continue? [Y/n] y
+Perform the update and continue? [Y/n] y
 [NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
            opam option jobs=1 --global
 Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
 
 <><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
 [default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables | grep -v eval-variables:
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
 default-invariant: ["i-am-sys-compiler"]
@@ -2493,18 +2587,33 @@ i-am-sys-compiler 2           One-line description
 ### :V:6:a: From 2.2~alpha root, global
 ### ocaml generate.ml 2.2~alpha
 ### # ro global state
-### opam option jobs | "${OPAMROOTVERSION}$" -> "current"
+### opam option jobs | "${OPAMROOTVERSION}" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~alpha to current
-FMT_UPG                         Format upgrade done
-### # ro global state, ro repo state, ro switch state
-### opam list | "${OPAMROOTVERSION}$" -> "current"
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.2~alpha to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~alpha to version current, which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~alpha to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
+### # ro global state, ro repo state, ro switch state
+### opam list | "${OPAMROOTVERSION}$" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ sw-sys-comp
 STATE                           Switch state loaded in 0.000s
 # Packages matching: installed
@@ -2515,8 +2624,6 @@ i-am-sys-compiler    1           One-line description
 ### # ro global state, ro repo state, rw switch state
 ### opam install i-am-another-package --switch sw-comp | "${OPAMROOTVERSION}$" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~alpha to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ sw-comp
@@ -2533,8 +2640,6 @@ Done.
 ### # ro global state, rw repo state
 ### opam repo add root-config ./root-config | "${OPAMROOTVERSION}$" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~alpha to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 [root-config] Initialised
@@ -2544,15 +2649,6 @@ RSTATE                          Cache found
 ### # rw global state
 ### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.2~alpha to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~alpha to version current which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -2560,7 +2656,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 eval-variables: [sys-comp-version ["sh" "-c" "echo $OPAMSYSCOMP"] "comp version"]
 installed-switches: ["sw-sys-comp" "sw-comp" "default"]
 jobs: 4
@@ -2569,9 +2665,17 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: ["default" {"file://${BASEDIR}/default"} "root-config" {"file://${BASEDIR}/root-config"}]
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
+repo "root-config" {
+url: "file://${BASEDIR}/root-config"
+}
 ### opam-cat $OPAMROOT/sw-comp/.opam-switch/switch-config
 invariant: ["i-am-compiler"]
 opam-version: "2.0"
@@ -2585,21 +2689,29 @@ roots: ["i-am-another-package.2" "i-am-compiler.2" "i-am-package.2"]
 ### ocaml generate.ml 2.2~alpha local
 ### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~alpha to current
-FMT_UPG                         Format upgrade done
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.2~alpha to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~alpha to version current which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
-STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
-STATE                           Switch state loaded in 0.000s
-# Packages matching: installed
-# Name            # Installed # Synopsis
-i-am-sys-compiler 2           One-line description
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### # ro global state, ro repo state, rw switch state
 ### opam install i-am-package | "${OPAMROOTVERSION}$" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~alpha to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
@@ -2617,15 +2729,83 @@ Done.
 ### # rw global state
 ### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+Set to '4' the field jobs in global configuration
+### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
+default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
+default-invariant: ["i-am-sys-compiler"]
+depext: true
+depext-cannot-install: false
+depext-run-installs: true
+download-jobs: 3
+eval-variables: [sys-comp-version ["sh" "-c" "echo $OPAMSYSCOMP"] "comp version"]
+installed-switches: ["sw-sys-comp" "sw-comp" "${BASEDIR}" "default"]
+jobs: 4
+opam-root-version: current
+opam-version: "2.0"
+repositories: "default"
+swh-fallback: false
+switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
+### opam-cat $OPAMROOT/repo/repos-config
+opam-version: "2.0"
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
+### opam-cat _opam/.opam-switch/switch-config
+invariant: ["i-am-sys-compiler" | "i-am-compiler"]
+opam-root: "${BASEDIR}/OPAM"
+opam-version: "2.0"
+synopsis: "local switch"
+### opam-cat _opam/.opam-switch/switch-state
+compiler: ["i-am-sys-compiler.2"]
+installed: ["i-am-package.2" "i-am-sys-compiler.2"]
+opam-version: "2.0"
+roots: ["i-am-package.2" "i-am-sys-compiler.2"]
+### :V:6:c: From 2.2~alpha root, local unknown from config
+### ocaml generate.ml 2.2~alpha local
+### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 [WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.2~alpha to current
+FMT_UPG                         Hard config upgrade, from 2.2~alpha to current
 This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~alpha to version current which can't be reverted.
 You may want to back it up before going further.
 
-Continue? [Y/n] y
+Perform the update and continue? [Y/n] y
 [NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
            opam option jobs=1 --global
 Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          No cache found
+RSTATE                          loaded opam files from repo default in 0.000s
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
+### # ro global state, ro repo state, rw switch state
+### opam install i-am-package | "${OPAMROOTVERSION}($|,)" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
+STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
+STATE                           Switch state loaded in 0.000s
+STATE                           Detected changed packages (marked for reinstall): {}
+The following actions will be performed:
+=== install 1 package
+  - install i-am-package 2
+
+<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
+-> installed i-am-package.2
+STATE                           dependencies (0.000) result={ i-am-sys-compiler.2 }
+Done.
+### # rw global state
+### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -2633,7 +2813,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 eval-variables: [sys-comp-version ["sh" "-c" "echo $OPAMSYSCOMP"] "comp version"]
 installed-switches: ["sw-sys-comp" "sw-comp" "${BASEDIR}" "default"]
 jobs: 4
@@ -2642,9 +2822,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -2655,25 +2840,343 @@ compiler: ["i-am-sys-compiler.2"]
 installed: ["i-am-package.2" "i-am-sys-compiler.2"]
 opam-version: "2.0"
 roots: ["i-am-package.2" "i-am-sys-compiler.2"]
-### :V:6:c: From 2.2~alpha root, local unknown from config
-### ocaml generate.ml 2.2~alpha local
+### :V:6:d: Upgraded root and local 2.2~alpha switch not recorded
+### ocaml generate.ml 2.2~alpha orphaned 2.2~alpha
+### # ro global state, ro repo state, ro switch state
+### opam list | "${OPAMROOTVERSION}" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.2~alpha to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~alpha to version current, which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          No cache found
+RSTATE                          loaded opam files from repo default in 0.000s
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
+### # ro global state, ro repo state, rw switch state
+### opam install i-am-package | "${OPAMROOTVERSION}$" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
+STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
+STATE                           Switch state loaded in 0.000s
+STATE                           Detected changed packages (marked for reinstall): {}
+The following actions will be performed:
+=== install 1 package
+  - install i-am-package 2
+
+<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
+-> installed i-am-package.2
+STATE                           dependencies (0.000) result={ i-am-sys-compiler.2 }
+Done.
+### # rw global state
+### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+Set to '4' the field jobs in global configuration
+### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
+default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
+default-invariant: ["i-am-sys-compiler"]
+depext: true
+depext-cannot-install: false
+depext-run-installs: true
+download-jobs: 3
+eval-variables: [sys-comp-version ["sh" "-c" "echo $OPAMSYSCOMP"] "comp version"]
+installed-switches: ["sw-sys-comp" "sw-comp" "default"]
+jobs: 4
+opam-root-version: current
+opam-version: "2.0"
+repositories: "default"
+swh-fallback: false
+switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
+### opam-cat $OPAMROOT/repo/repos-config
+opam-version: "2.0"
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
+### opam-cat _opam/.opam-switch/switch-config
+invariant: ["i-am-sys-compiler" | "i-am-compiler"]
+opam-root: "${BASEDIR}/OPAM"
+opam-version: "2.0"
+synopsis: "local switch"
+### opam-cat _opam/.opam-switch/switch-state
+compiler: ["i-am-sys-compiler.2"]
+installed: ["i-am-package.2" "i-am-sys-compiler.2"]
+opam-version: "2.0"
+roots: ["i-am-package.2" "i-am-sys-compiler.2"]
+### :V:6:e: reinit from 2.2~alpha
+### ocaml generate.ml 2.2~alpha
+### opam init --reinit --bypass-checks --no-setup | grep -v Cygwin | "${OPAMROOTVERSION}($|,)" -> "current"
+No configuration file found, using built-in defaults.
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.2~alpha to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~alpha to version current which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
+           opam option jobs=1 --global
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          No cache found
+RSTATE                          loaded opam files from repo default in 0.000s
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
+### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
+default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
+default-invariant: ["i-am-sys-compiler"]
+depext: true
+depext-cannot-install: false
+depext-run-installs: true
+download-jobs: 3
+eval-variables: [sys-comp-version ["sh" "-c" "echo $OPAMSYSCOMP"] "comp version"]
+installed-switches: ["sw-sys-comp" "sw-comp" "default"]
+opam-root-version: current
+opam-version: "2.0"
+repositories: "default"
+swh-fallback: false
+switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
+### opam switch --short
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+${BASEDIR}
+default
+sw-comp
+sw-sys-comp
+### opam list
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
+STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
+STATE                           Switch state loaded in 0.000s
+# Packages matching: installed
+# Name            # Installed # Synopsis
+i-am-package      2           One-line description
+i-am-sys-compiler 2           One-line description
+### rm -rf _opam
+### :V:7:a: From 2.2~beta root, global
+### ocaml generate.ml 2.2~beta
+### # ro global state
+### opam option jobs | "${OPAMROOTVERSION}" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.2~beta to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~beta to version current, which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          No cache found
+RSTATE                          loaded opam files from repo default in 0.000s
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
+### # ro global state, ro repo state, ro switch state
+### opam list | "${OPAMROOTVERSION}$" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
+STATE                           LOAD-SWITCH-STATE @ sw-sys-comp
+STATE                           Switch state loaded in 0.000s
+# Packages matching: installed
+# Name               # Installed # Synopsis
+i-am-another-package 2           One-line description
+i-am-package         2           One-line description
+i-am-sys-compiler    1           One-line description
+### # ro global state, ro repo state, rw switch state
+### opam install i-am-another-package --switch sw-comp | "${OPAMROOTVERSION}$" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
+STATE                           LOAD-SWITCH-STATE @ sw-comp
+STATE                           Switch state loaded in 0.000s
+STATE                           Detected changed packages (marked for reinstall): {}
+The following actions will be performed:
+=== install 1 package
+  - install i-am-another-package 2
+
+<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
+-> installed i-am-another-package.2
+STATE                           dependencies (0.000) result={ i-am-compiler.2 }
+Done.
+### # ro global state, rw repo state
+### opam repo add root-config ./root-config | "${OPAMROOTVERSION}$" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
+[root-config] Initialised
+[NOTE] Repository root-config has been added to the selections of switch sw-sys-comp only.
+       Run `opam repository add root-config --all-switches|--set-default' to use it in all existing switches, or in newly created switches, respectively.
+
+### # rw global state
+### opam option jobs=4 | "${OPAMROOTVERSION}$" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+Set to '4' the field jobs in global configuration
+### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
+default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
+default-invariant: ["i-am-sys-compiler"]
+depext: true
+depext-cannot-install: false
+depext-run-installs: true
+download-jobs: 3
+eval-variables: [sys-comp-version ["sh" "-c" "echo $OPAMSYSCOMP"] "comp version"]
+installed-switches: ["sw-sys-comp" "sw-comp" "default"]
+jobs: 4
+opam-root-version: current
+opam-version: "2.0"
+repositories: "default"
+swh-fallback: false
+switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
+### opam-cat $OPAMROOT/repo/repos-config
+opam-version: "2.0"
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
+repo "root-config" {
+url: "file://${BASEDIR}/root-config"
+}
+### opam-cat $OPAMROOT/sw-comp/.opam-switch/switch-config
+invariant: ["i-am-compiler"]
+opam-version: "2.0"
+synopsis: "switch with compiler"
+### opam-cat $OPAMROOT/sw-comp/.opam-switch/switch-state
+compiler: ["i-am-compiler.2"]
+installed: ["i-am-another-package.2" "i-am-compiler.2" "i-am-package.2"]
+opam-version: "2.0"
+roots: ["i-am-another-package.2" "i-am-compiler.2" "i-am-package.2"]
+### :V:7:b: From 2.2~beta root, local
+### ocaml generate.ml 2.2~beta local
+### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.2~beta to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~beta to version current which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          No cache found
+RSTATE                          loaded opam files from repo default in 0.000s
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
+### # ro global state, ro repo state, rw switch state
+### opam install i-am-package | "${OPAMROOTVERSION}$" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
+STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
+STATE                           Definition missing for installed package i-am-sys-compiler.2, copying from repo
+STATE                           Switch state loaded in 0.000s
+STATE                           Detected changed packages (marked for reinstall): {}
+The following actions will be performed:
+=== install 1 package
+  - install i-am-package 2
+
+<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
+-> installed i-am-package.2
+STATE                           dependencies (0.000) result={ i-am-sys-compiler.2 }
+Done.
+### # rw global state
+### opam option jobs=4 | "${OPAMROOTVERSION}$" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+Set to '4' the field jobs in global configuration
+### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
+default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
+default-invariant: ["i-am-sys-compiler"]
+depext: true
+depext-cannot-install: false
+depext-run-installs: true
+download-jobs: 3
+eval-variables: [sys-comp-version ["sh" "-c" "echo $OPAMSYSCOMP"] "comp version"]
+installed-switches: ["sw-sys-comp" "sw-comp" "${BASEDIR}" "default"]
+jobs: 4
+opam-root-version: current
+opam-version: "2.0"
+repositories: "default"
+swh-fallback: false
+switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
+### opam-cat $OPAMROOT/repo/repos-config
+opam-version: "2.0"
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
+### opam-cat _opam/.opam-switch/switch-config
+invariant: ["i-am-sys-compiler" | "i-am-compiler"]
+opam-root: "${BASEDIR}/OPAM"
+opam-version: "2.0"
+synopsis: "local switch"
+### opam-cat _opam/.opam-switch/switch-state
+compiler: ["i-am-sys-compiler.2"]
+installed: ["i-am-package.2" "i-am-sys-compiler.2"]
+opam-version: "2.0"
+roots: ["i-am-package.2" "i-am-sys-compiler.2"]
+### :V:7:c: From 2.2~beta root, local unknown from config
+### ocaml generate.ml 2.2~beta local
 ### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~alpha to current
-FMT_UPG                         Format upgrade done
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.2~beta to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~beta to version current which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
-STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
-STATE                           Switch state loaded in 0.000s
-# Packages matching: installed
-# Name            # Installed # Synopsis
-i-am-sys-compiler 2           One-line description
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### # ro global state, ro repo state, rw switch state
 ### opam install i-am-package | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~alpha to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
@@ -2688,17 +3191,8 @@ The following actions will be performed:
 STATE                           dependencies (0.000) result={ i-am-sys-compiler.2 }
 Done.
 ### # rw global state
-### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
+### opam option jobs=4 | "${OPAMROOTVERSION}$" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.2~alpha to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~alpha to version current which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -2706,7 +3200,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 eval-variables: [sys-comp-version ["sh" "-c" "echo $OPAMSYSCOMP"] "comp version"]
 installed-switches: ["sw-sys-comp" "sw-comp" "${BASEDIR}" "default"]
 jobs: 4
@@ -2715,9 +3209,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -2728,26 +3227,32 @@ compiler: ["i-am-sys-compiler.2"]
 installed: ["i-am-package.2" "i-am-sys-compiler.2"]
 opam-version: "2.0"
 roots: ["i-am-package.2" "i-am-sys-compiler.2"]
-### :V:6:d: Upgraded root and local 2.2~alpha switch not recorded
-### ocaml generate.ml 2.2~alpha orphaned 2.2~alpha
+### :V:7:d: Upgraded root and local 2.2~beta switch not recorded
+### ocaml generate.ml 2.2~beta orphaned 2.2~beta
 ### # ro global state, ro repo state, ro switch state
-### opam list | "${OPAMROOTVERSION}$" -> "current"
+### opam list | "${OPAMROOTVERSION}" -> "current"
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.2~beta to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~beta to version current, which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~alpha to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
-STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
-STATE                           Switch state loaded in 0.000s
-# Packages matching: installed
-# Name            # Installed # Synopsis
-i-am-sys-compiler 2           One-line description
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### # ro global state, ro repo state, rw switch state
 ### opam install i-am-package | "${OPAMROOTVERSION}$" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~alpha to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
@@ -2762,17 +3267,8 @@ The following actions will be performed:
 STATE                           dependencies (0.000) result={ i-am-sys-compiler.2 }
 Done.
 ### # rw global state
-### opam option jobs=4 | "${OPAMROOTVERSION}($|,)" -> "current"
+### opam option jobs=4 | "${OPAMROOTVERSION}$" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.2~alpha to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~alpha to version current which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -2780,7 +3276,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 eval-variables: [sys-comp-version ["sh" "-c" "echo $OPAMSYSCOMP"] "comp version"]
 installed-switches: ["sw-sys-comp" "sw-comp" "default"]
 jobs: 4
@@ -2789,9 +3285,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -2802,26 +3303,29 @@ compiler: ["i-am-sys-compiler.2"]
 installed: ["i-am-package.2" "i-am-sys-compiler.2"]
 opam-version: "2.0"
 roots: ["i-am-package.2" "i-am-sys-compiler.2"]
-### :V:6:e: reinit from 2.2~alpha
-### ocaml generate.ml 2.2~alpha
-### opam init --reinit --bypass-checks --no-setup | grep -v Cygwin | "${OPAMROOTVERSION}($|,)" -> "current"
+### :V:7:e: reinit from 2.2~beta
+### ocaml generate.ml 2.2~beta
+### opam init --reinit --bypass-checks --no-setup | grep -v Cygwin | "${OPAMROOTVERSION}" -> "current"
 No configuration file found, using built-in defaults.
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 [WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.2~alpha to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~alpha to version current which can't be reverted.
+FMT_UPG                         Hard config upgrade, from 2.2~beta to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~beta to version current, which can't be reverted.
 You may want to back it up before going further.
 
-Continue? [Y/n] y
-[NOTE] The 'jobs' option was reset, its value was 1 and its new value will vary according to the current number of cores on your machine. You can restore the fixed value using:
-           opam option jobs=1 --global
+Perform the update and continue? [Y/n] y
 Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
 
 <><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
 [default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
 default-invariant: ["i-am-sys-compiler"]
@@ -2856,21 +3360,34 @@ STATE                           Switch state loaded in 0.000s
 i-am-package      2           One-line description
 i-am-sys-compiler 2           One-line description
 ### rm -rf _opam
-### :V:7:a: From 2.2~beta root, global
-### ocaml generate.ml 2.2~beta
+### :V:8:a: From 2.2 root, global
+### ocaml generate.ml 2.2
 ### # ro global state
-### opam option jobs | "${OPAMROOTVERSION}$" -> "current"
+### opam option jobs | "${OPAMROOTVERSION}" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~beta to current
-FMT_UPG                         Format upgrade done
-### # ro global state, ro repo state, ro switch state
-### opam list | "${OPAMROOTVERSION}$" -> "current"
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.2 to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2 to version current, which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~beta to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
+### # ro global state, ro repo state, ro switch state
+### opam list
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
+RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ sw-sys-comp
 STATE                           Switch state loaded in 0.000s
 # Packages matching: installed
@@ -2879,10 +3396,8 @@ i-am-another-package 2           One-line description
 i-am-package         2           One-line description
 i-am-sys-compiler    1           One-line description
 ### # ro global state, ro repo state, rw switch state
-### opam install i-am-another-package --switch sw-comp | "${OPAMROOTVERSION}$" -> "current"
+### opam install i-am-another-package --switch sw-comp
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~beta to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ sw-comp
@@ -2897,10 +3412,8 @@ The following actions will be performed:
 STATE                           dependencies (0.000) result={ i-am-compiler.2 }
 Done.
 ### # ro global state, rw repo state
-### opam repo add root-config ./root-config | "${OPAMROOTVERSION}$" -> "current"
+### opam repo add root-config ./root-config
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~beta to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 [root-config] Initialised
@@ -2908,15 +3421,8 @@ RSTATE                          Cache found
        Run `opam repository add root-config --all-switches|--set-default' to use it in all existing switches, or in newly created switches, respectively.
 
 ### # rw global state
-### opam option jobs=4 | "${OPAMROOTVERSION}$" -> "current"
+### opam option jobs=4
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.2~beta to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~beta to version 2.2, which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -2924,7 +3430,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 eval-variables: [sys-comp-version ["sh" "-c" "echo $OPAMSYSCOMP"] "comp version"]
 installed-switches: ["sw-sys-comp" "sw-comp" "default"]
 jobs: 4
@@ -2933,9 +3439,17 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: ["default" {"file://${BASEDIR}/default"} "root-config" {"file://${BASEDIR}/root-config"}]
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
+repo "root-config" {
+url: "file://${BASEDIR}/root-config"
+}
 ### opam-cat $OPAMROOT/sw-comp/.opam-switch/switch-config
 invariant: ["i-am-compiler"]
 opam-version: "2.0"
@@ -2945,25 +3459,31 @@ compiler: ["i-am-compiler.2"]
 installed: ["i-am-another-package.2" "i-am-compiler.2" "i-am-package.2"]
 opam-version: "2.0"
 roots: ["i-am-another-package.2" "i-am-compiler.2" "i-am-package.2"]
-### :V:7:b: From 2.2~beta root, local
-### ocaml generate.ml 2.2~beta local
+### :V:8:b: From 2.2 root, local
+### ocaml generate.ml 2.2 local
 ### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~beta to current
-FMT_UPG                         Format upgrade done
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.2 to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2 to version current which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
-STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
-STATE                           Switch state loaded in 0.000s
-# Packages matching: installed
-# Name            # Installed # Synopsis
-i-am-sys-compiler 2           One-line description
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### # ro global state, ro repo state, rw switch state
-### opam install i-am-package | "${OPAMROOTVERSION}$" -> "current"
+### opam install i-am-package
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~beta to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
@@ -2979,15 +3499,8 @@ The following actions will be performed:
 STATE                           dependencies (0.000) result={ i-am-sys-compiler.2 }
 Done.
 ### # rw global state
-### opam option jobs=4 | "${OPAMROOTVERSION}$" -> "current"
+### opam option jobs=4
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.2~beta to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~beta to version 2.2, which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -2995,7 +3508,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 eval-variables: [sys-comp-version ["sh" "-c" "echo $OPAMSYSCOMP"] "comp version"]
 installed-switches: ["sw-sys-comp" "sw-comp" "${BASEDIR}" "default"]
 jobs: 4
@@ -3004,9 +3517,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -3017,25 +3535,31 @@ compiler: ["i-am-sys-compiler.2"]
 installed: ["i-am-package.2" "i-am-sys-compiler.2"]
 opam-version: "2.0"
 roots: ["i-am-package.2" "i-am-sys-compiler.2"]
-### :V:7:c: From 2.2~beta root, local unknown from config
-### ocaml generate.ml 2.2~beta local
+### :V:8:c: From 2.2 root, local unknown from config
+### ocaml generate.ml 2.2 local
 ### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~beta to current
-FMT_UPG                         Format upgrade done
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.2 to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2 to version current which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
-STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
-STATE                           Switch state loaded in 0.000s
-# Packages matching: installed
-# Name            # Installed # Synopsis
-i-am-sys-compiler 2           One-line description
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### # ro global state, ro repo state, rw switch state
 ### opam install i-am-package | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~beta to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
@@ -3050,15 +3574,8 @@ The following actions will be performed:
 STATE                           dependencies (0.000) result={ i-am-sys-compiler.2 }
 Done.
 ### # rw global state
-### opam option jobs=4 | "${OPAMROOTVERSION}$" -> "current"
+### opam option jobs=4
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.2~beta to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~beta to version 2.2, which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -3066,7 +3583,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 eval-variables: [sys-comp-version ["sh" "-c" "echo $OPAMSYSCOMP"] "comp version"]
 installed-switches: ["sw-sys-comp" "sw-comp" "${BASEDIR}" "default"]
 jobs: 4
@@ -3075,9 +3592,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -3088,26 +3610,32 @@ compiler: ["i-am-sys-compiler.2"]
 installed: ["i-am-package.2" "i-am-sys-compiler.2"]
 opam-version: "2.0"
 roots: ["i-am-package.2" "i-am-sys-compiler.2"]
-### :V:7:d: Upgraded root and local 2.2~beta switch not recorded
-### ocaml generate.ml 2.2~beta orphaned 2.2~beta
+### :V:8:d: Upgraded root and local 2.2 switch not recorded
+### ocaml generate.ml 2.2 orphaned 2.2
 ### # ro global state, ro repo state, ro switch state
-### opam list | "${OPAMROOTVERSION}$" -> "current"
+### opam list
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
+[WARNING] Removing global switch 'this-internal-error' as it no longer exists
+FMT_UPG                         Hard config upgrade, from 2.2 to 2.4
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2 to version 2.4, which can't be reverted.
+You may want to back it up before going further.
+
+Perform the update and continue? [Y/n] y
+Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~beta to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
-STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
-STATE                           Switch state loaded in 0.000s
-# Packages matching: installed
-# Name            # Installed # Synopsis
-i-am-sys-compiler 2           One-line description
+
+<><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
+[default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### # ro global state, ro repo state, rw switch state
-### opam install i-am-package | "${OPAMROOTVERSION}$" -> "current"
+### opam install i-am-package
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-FMT_UPG                         On-the-fly config upgrade, from 2.2~beta to current
-FMT_UPG                         Format upgrade done
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          Cache found
 STATE                           LOAD-SWITCH-STATE @ ${BASEDIR}
@@ -3122,15 +3650,8 @@ The following actions will be performed:
 STATE                           dependencies (0.000) result={ i-am-sys-compiler.2 }
 Done.
 ### # rw global state
-### opam option jobs=4 | "${OPAMROOTVERSION}$" -> "current"
+### opam option jobs=4
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
-[WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.2~beta to current
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~beta to version 2.2, which can't be reverted.
-You may want to back it up before going further.
-
-Continue? [Y/n] y
-Format upgrade done.
 Set to '4' the field jobs in global configuration
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
@@ -3138,7 +3659,7 @@ default-invariant: ["i-am-sys-compiler"]
 depext: true
 depext-cannot-install: false
 depext-run-installs: true
-download-jobs: 1
+download-jobs: 3
 eval-variables: [sys-comp-version ["sh" "-c" "echo $OPAMSYSCOMP"] "comp version"]
 installed-switches: ["sw-sys-comp" "sw-comp" "default"]
 jobs: 4
@@ -3147,9 +3668,14 @@ opam-version: "2.0"
 repositories: "default"
 swh-fallback: false
 switch: "sw-sys-comp"
+wrap-build-commands: ["%{hooks}%/sandbox.sh" "build"] {os = "linux" | os = "macos"}
+wrap-install-commands: ["%{hooks}%/sandbox.sh" "install"] {os = "linux" | os = "macos"}
+wrap-remove-commands: ["%{hooks}%/sandbox.sh" "remove"] {os = "linux" | os = "macos"}
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -3160,24 +3686,29 @@ compiler: ["i-am-sys-compiler.2"]
 installed: ["i-am-package.2" "i-am-sys-compiler.2"]
 opam-version: "2.0"
 roots: ["i-am-package.2" "i-am-sys-compiler.2"]
-### :V:7:e: reinit from 2.2~beta
-### ocaml generate.ml 2.2~beta
-### opam init --reinit --bypass-checks --no-setup | grep -v Cygwin
+### :V:8:e: reinit from 2.2
+### ocaml generate.ml 2.2
+### opam init --reinit --bypass-checks --no-setup | grep -v Cygwin | "${OPAMROOTVERSION}" -> "current"
 No configuration file found, using built-in defaults.
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 [WARNING] Removing global switch 'this-internal-error' as it no longer exists
-FMT_UPG                         Light config upgrade, from 2.2~beta to 2.2
-This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2~beta to version 2.2, which can't be reverted.
+FMT_UPG                         Hard config upgrade, from 2.2 to current
+This version of opam requires an update to the layout of ${BASEDIR}/OPAM from version 2.2 to version current, which can't be reverted.
 You may want to back it up before going further.
 
-Continue? [Y/n] y
+Perform the update and continue? [Y/n] y
 Format upgrade done.
+
+<><> Rerunning init and update ><><><><><><><><><><><><><><><><><><><><><><><><>
+GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
 RSTATE                          No cache found
 RSTATE                          loaded opam files from repo default in 0.000s
 
 <><> Updating repositories ><><><><><><><><><><><><><><><><><><><><><><><><><><>
 [default] no changes from file://${BASEDIR}/default
+Update done, please now retry your command.
+# Return code 10 #
 ### opam-cat $OPAMROOT/config | '"${OPAMROOTVERSION}"' -> "current" | grep -v sys-pkg-manager-cmd | grep -v global-variables
 default-compiler: ["i-am-sys-compiler" "i-am-compiler"]
 default-invariant: ["i-am-sys-compiler"]
@@ -3212,8 +3743,8 @@ STATE                           Switch state loaded in 0.000s
 i-am-package      2           One-line description
 i-am-sys-compiler 2           One-line description
 ### rm -rf _opam
-### :V:8:a: From 2.2 root, global
-### ocaml generate.ml $OPAMROOTVERSION
+### :V:9:a: From 2.4 root, global
+### ocaml generate.ml 2.4
 ### # ro global state
 ### opam option jobs
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
@@ -3276,7 +3807,12 @@ swh-fallback: false
 switch: "sw-sys-comp"
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: ["default" {"file://${BASEDIR}/default"} "root-config" {"file://${BASEDIR}/root-config"}]
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
+repo "root-config" {
+url: "file://${BASEDIR}/root-config"
+}
 ### opam-cat $OPAMROOT/sw-comp/.opam-switch/switch-config
 invariant: ["i-am-compiler"]
 opam-version: "2.0"
@@ -3286,8 +3822,8 @@ compiler: ["i-am-compiler.2"]
 installed: ["i-am-another-package.2" "i-am-compiler.2" "i-am-package.2"]
 opam-version: "2.0"
 roots: ["i-am-another-package.2" "i-am-compiler.2" "i-am-package.2"]
-### :V:8:b: From 2.2 root, local
-### ocaml generate.ml $OPAMROOTVERSION local
+### :V:9:b: From 2.4 root, local
+### ocaml generate.ml 2.4 local
 ### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
@@ -3336,7 +3872,9 @@ swh-fallback: false
 switch: "sw-sys-comp"
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -3347,8 +3885,8 @@ compiler: ["i-am-sys-compiler.2"]
 installed: ["i-am-package.2" "i-am-sys-compiler.2"]
 opam-version: "2.0"
 roots: ["i-am-package.2" "i-am-sys-compiler.2"]
-### :V:8:c: From 2.2 root, local unknown from config
-### ocaml generate.ml $OPAMROOTVERSION local
+### :V:9:c: From 2.4 root, local unknown from config
+### ocaml generate.ml 2.4 local
 ### opam list | "${OPAMROOTVERSION}($|,)" -> "current"
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
@@ -3396,7 +3934,9 @@ swh-fallback: false
 switch: "sw-sys-comp"
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -3407,8 +3947,8 @@ compiler: ["i-am-sys-compiler.2"]
 installed: ["i-am-package.2" "i-am-sys-compiler.2"]
 opam-version: "2.0"
 roots: ["i-am-package.2" "i-am-sys-compiler.2"]
-### :V:8:d: Upgraded root and local 2.2 switch not recorded
-### ocaml generate.ml $OPAMROOTVERSION orphaned 2.2
+### :V:9:d: Upgraded root and local 2.4 switch not recorded
+### ocaml generate.ml 2.4 orphaned 2.4
 ### # ro global state, ro repo state, ro switch state
 ### opam list
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
@@ -3457,7 +3997,9 @@ swh-fallback: false
 switch: "sw-sys-comp"
 ### opam-cat $OPAMROOT/repo/repos-config
 opam-version: "2.0"
-repositories: "default" {"file://${BASEDIR}/default"}
+repo "default" {
+url: "file://${BASEDIR}/default"
+}
 ### opam-cat _opam/.opam-switch/switch-config
 invariant: ["i-am-sys-compiler" | "i-am-compiler"]
 opam-root: "${BASEDIR}/OPAM"
@@ -3468,9 +4010,9 @@ compiler: ["i-am-sys-compiler.2"]
 installed: ["i-am-package.2" "i-am-sys-compiler.2"]
 opam-version: "2.0"
 roots: ["i-am-package.2" "i-am-sys-compiler.2"]
-### :V:8:e: reinit from 2.2
-### ocaml generate.ml 2.2
-### opam init --reinit --bypass-checks --no-setup | grep -v Cygwin
+### :V:9:e: reinit from 2.4
+### ocaml generate.ml 2.4
+### opam init --reinit --bypass-checks --no-setup | grep -v Cygwin | "${OPAMROOTVERSION}" -> "current"
 No configuration file found, using built-in defaults.
 GSTATE                          LOAD-GLOBAL-STATE @ ${BASEDIR}/OPAM
 RSTATE                          LOAD-REPOSITORY-STATE @ ${BASEDIR}/OPAM
@@ -3513,3 +4055,4 @@ STATE                           Switch state loaded in 0.000s
 # Name            # Installed # Synopsis
 i-am-package      2           One-line description
 i-am-sys-compiler 2           One-line description
+### rm -rf _opam
diff --git a/tests/reftests/repository.test b/tests/reftests/repository.test
index fa07335b318..9030137ee1c 100644
--- a/tests/reftests/repository.test
+++ b/tests/reftests/repository.test
@@ -838,34 +838,34 @@ nourl        file://${BASEDIR}/nourl nourl
 no     --
 ### <OPAM/repo/repos-config>
 opam-version: "2.0"
-repositories: [ "nourl" ]
+repo "nourl" { }
 ### opam repo --all
 [WARNING] Errors in ${BASEDIR}/OPAM/repo/repos-config, some fields have been ignored:
-            - At ${BASEDIR}/OPAM/repo/repos-config:2:16-2:23::
-              expected url
+            - In ${BASEDIR}/OPAM/repo/repos-config:
+              missing URL
 
 # Repository # Url # Switches(rank)
 ### <nourl/packages/yes/yes.1/opam>
 opam-version: "2.0"
 ### opam update nourl
 [WARNING] Errors in ${BASEDIR}/OPAM/repo/repos-config, some fields have been ignored:
-            - At ${BASEDIR}/OPAM/repo/repos-config:2:16-2:23::
-              expected url
+            - In ${BASEDIR}/OPAM/repo/repos-config:
+              missing URL
 
 [ERROR] Unknown repositories or installed packages: nourl
 # Return code 40 #
 ### opam list -A
 [WARNING] Errors in ${BASEDIR}/OPAM/repo/repos-config, some fields have been ignored:
-            - At ${BASEDIR}/OPAM/repo/repos-config:2:16-2:23::
-              expected url
+            - In ${BASEDIR}/OPAM/repo/repos-config:
+              missing URL
 
 # Packages matching: any
 # No matches found
 ### sh -c "rm OPAM/repo/state-*.cache"
 ### opam list -A
 [WARNING] Errors in ${BASEDIR}/OPAM/repo/repos-config, some fields have been ignored:
-            - At ${BASEDIR}/OPAM/repo/repos-config:2:16-2:23::
-              expected url
+            - In ${BASEDIR}/OPAM/repo/repos-config:
+              missing URL
 
 # Packages matching: any
 # No matches found
diff --git a/tests/reftests/upgrade-two-point-o.test b/tests/reftests/upgrade-two-point-o.test.disabled
similarity index 94%
rename from tests/reftests/upgrade-two-point-o.test
rename to tests/reftests/upgrade-two-point-o.test.disabled
index d880a4c45b1..bd6d3c88452 100644
--- a/tests/reftests/upgrade-two-point-o.test
+++ b/tests/reftests/upgrade-two-point-o.test.disabled
@@ -1,3 +1,4 @@
+### : Disabled with the integration of the new hard upgrade for 2.4, this test make no more sense
 N0REP0
 ### <pkg:i-am-compiler.1>
 opam-version: "2.0"