diff --git a/lib/build.ml b/lib/build.ml
index caf66985..5d6cbfe7 100644
--- a/lib/build.ml
+++ b/lib/build.ml
@@ -24,10 +24,12 @@ module Spec = struct
     revdep : package option;
     with_tests : bool;
     lower_bounds : bool;
+    local : bool;
     opam_version : [`V2_0 | `V2_1 | `Dev];
   } [@@deriving to_yojson]
 
   type list_revdeps = {
+    local : bool;
     opam_version : [`V2_0 | `V2_1 | `Dev];
   } [@@deriving to_yojson]
 
@@ -40,8 +42,8 @@ module Spec = struct
     ty : ty;
   }
 
-  let opam ?revdep ~platform ~lower_bounds ~with_tests ~opam_version pkg =
-    let ty = `Opam (`Build { revdep; lower_bounds; with_tests; opam_version }, pkg) in
+  let opam ?revdep ~platform ~lower_bounds ~with_tests ~local ~opam_version pkg =
+    let ty = `Opam (`Build { revdep; lower_bounds; with_tests; local; opam_version }, pkg) in
     { platform; ty }
 
   let pp_pkg ?revdep f pkg =
@@ -55,14 +57,16 @@ module Spec = struct
     | `Dev -> "dev"
 
   let pp_ty f = function
-    | `Opam (`List_revdeps {opam_version}, pkg) ->
-        Fmt.pf f "list revdeps of %s, using opam %s" (OpamPackage.to_string pkg)
+    | `Opam (`List_revdeps {local; opam_version}, pkg) ->
+        Fmt.pf f "list revdeps of %s, using opam %s%s" (OpamPackage.to_string pkg)
           (pp_opam_version opam_version)
-    | `Opam (`Build { revdep; lower_bounds; with_tests; opam_version }, pkg) ->
+          (if local then ", using a local switch" else "")
+    | `Opam (`Build { revdep; lower_bounds; with_tests; local; opam_version }, pkg) ->
       let action = if with_tests then "test" else "build" in
-      Fmt.pf f "%s %a%s, using opam %s" action (pp_pkg ?revdep) pkg
+      Fmt.pf f "%s %a%s, using opam %s%s" action (pp_pkg ?revdep) pkg
         (if lower_bounds then ", lower-bounds" else "")
         (pp_opam_version opam_version)
+          (if local then ", using a local switch" else "")
 end
 
 type t = {
@@ -143,8 +147,8 @@ module Op = struct
     let build_spec ~for_docker =
       let base = base_to_string base in
       match ty with
-      | `Opam (`List_revdeps { opam_version }, pkg) -> Opam_build.revdeps ~for_docker ~opam_version ~base ~variant ~pkg
-      | `Opam (`Build { revdep; lower_bounds; with_tests; opam_version }, pkg) -> Opam_build.spec ~for_docker ~opam_version ~base ~variant ~revdep ~lower_bounds ~with_tests ~pkg
+      | `Opam (`List_revdeps { local; opam_version }, pkg) -> Opam_build.revdeps ~for_docker ~local ~opam_version ~base ~variant ~pkg
+      | `Opam (`Build { revdep; lower_bounds; with_tests; local; opam_version }, pkg) -> Opam_build.spec ~for_docker ~local ~opam_version ~base ~variant ~revdep ~lower_bounds ~with_tests ~pkg
     in
     Current.Job.write job
       (Fmt.str "@.\
@@ -218,7 +222,8 @@ let v t ~label ~spec ~base ~master ~urgent commit =
   BC.run t { Op.Key.pool; commit; variant; ty } ()
   |> Current.Primitive.map_result (Result.map ignore) (* TODO: Create a separate type of cache that doesn't parse the output *)
 
-let list_revdeps t ~platform ~opam_version ~pkgopt ~base ~master ~after commit =
+(* TODO: Remove the duplicated opam_version parameter (already contained in t) *)
+let list_revdeps t ~platform ~local ~opam_version ~pkgopt ~base ~master ~after commit =
   Current.component "list revdeps" |>
   let> {PackageOpt.pkg; urgent; has_tests = _} = pkgopt
   and> base = base
@@ -227,7 +232,7 @@ let list_revdeps t ~platform ~opam_version ~pkgopt ~base ~master ~after commit =
   and> () = after in
   let t = { Op.config = t; master; urgent; base } in
   let { Platform.pool; variant; label = _ } = platform in
-  let ty = `Opam (`List_revdeps {Spec.opam_version}, pkg) in
+  let ty = `Opam (`List_revdeps {Spec.local; opam_version}, pkg) in
   BC.run t { Op.Key.pool; commit; variant; ty } ()
   |> Current.Primitive.map_result (Result.map (fun output ->
       String.split_on_char '\n' output |>
diff --git a/lib/build.mli b/lib/build.mli
index fd24ac2a..0d36c30b 100644
--- a/lib/build.mli
+++ b/lib/build.mli
@@ -6,6 +6,7 @@ module Spec : sig
     platform:Platform.t ->
     lower_bounds:bool ->
     with_tests:bool ->
+    local:bool ->
     opam_version:[`V2_0 | `V2_1 | `Dev] ->
     OpamPackage.t ->
     t
@@ -32,6 +33,7 @@ val v :
 val list_revdeps :
   t ->
   platform:Platform.t ->
+  local:bool ->
   opam_version:[`V2_0 | `V2_1 | `Dev] ->
   pkgopt:PackageOpt.t Current.t ->
   base:base Current.t ->
diff --git a/lib/opam_build.ml b/lib/opam_build.ml
index 602428b3..3fe2461c 100644
--- a/lib/opam_build.ml
+++ b/lib/opam_build.ml
@@ -55,7 +55,7 @@ let opam_install ~variant ~opam_version ~pin ~lower_bounds ~with_tests ~pkg =
       pkg
   ]
 
-let setup_repository ~variant ~for_docker ~opam_version =
+let setup_repository ~variant ~for_docker ~local ~opam_version =
   let open Obuilder_spec in
   let home_dir = match Variant.os variant with
     | `macOS -> None
@@ -99,6 +99,21 @@ let setup_repository ~variant ~for_docker ~opam_version =
   env "OPAMERRLOGLEN" "0" :: (* Show the whole log if it fails *)
   env "OPAMSOLVERTIMEOUT" "500" :: (* Increase timeout. Poor mccs is doing its best *)
   env "OPAMPRECISETRACKING" "1" :: (* Mitigate https://github.com/ocaml/opam/issues/3997 *)
+  (if local then
+     (* TODO: Check global switch parent directory with spaces on Windows *)
+     (* NOTE: Check that the package supports directories with spaces *)
+     let dirname = "directory with space" in
+     let packages = Variant.packages variant in
+     [
+       run "opam switch remove \"$(opam switch show)\"";
+       run "mkdir '%s' && opam switch create './%s' --packages '%s'"
+         dirname dirname packages;
+       (* NOTE: Check that the package supports being inside a dune project by
+          having a dune-project file in the parent directory and having a required dune version
+          too high so the call to dune would fail. *)
+       run "echo '(lang dune 9999.0)' > '%s'/dune-project" dirname;
+     ]
+   else []) @
   [
     run "rm -rf opam-repository/";
     copy ["."] ~dst:"opam-repository/";
@@ -111,7 +126,7 @@ let set_personality ~variant =
   else
     []
 
-let spec ~for_docker ~opam_version ~base ~variant ~revdep ~lower_bounds ~with_tests ~pkg =
+let spec ~for_docker ~local ~opam_version ~base ~variant ~revdep ~lower_bounds ~with_tests ~pkg =
   let opam_install = opam_install ~variant ~opam_version in
   let revdep = match revdep with
     | None -> []
@@ -126,18 +141,18 @@ let spec ~for_docker ~opam_version ~base ~variant ~revdep ~lower_bounds ~with_te
   in
   Obuilder_spec.stage ~from:base (
     set_personality ~variant
-    @ setup_repository ~variant ~for_docker ~opam_version
+    @ setup_repository ~variant ~for_docker ~local ~opam_version
     @ opam_install ~pin:true ~lower_bounds:false ~with_tests:false ~pkg
     @ lower_bounds
     @ revdep
     @ tests
   )
 
-let revdeps ~for_docker ~opam_version ~base ~variant ~pkg =
+let revdeps ~for_docker ~local ~opam_version ~base ~variant ~pkg =
   let open Obuilder_spec in
   let pkg = Filename.quote (OpamPackage.to_string pkg) in
   Obuilder_spec.stage ~from:base (
-    setup_repository ~variant ~for_docker ~opam_version
+    setup_repository ~variant ~for_docker ~local ~opam_version
     @ [
       run "echo '@@@OUTPUT' && \
            opam list -s --color=never --depends-on %s --coinstallable-with %s --installable --all-versions --recursive --depopts && \
diff --git a/lib/opam_build.mli b/lib/opam_build.mli
index e6619ac0..c0af6754 100644
--- a/lib/opam_build.mli
+++ b/lib/opam_build.mli
@@ -1,5 +1,6 @@
 val spec :
   for_docker:bool ->
+  local:bool ->
   opam_version:[`V2_0 | `V2_1 | `Dev] ->
   base:string ->
   variant:Variant.t ->
@@ -11,6 +12,7 @@ val spec :
 
 val revdeps :
   for_docker:bool ->
+  local:bool ->
   opam_version:[`V2_0 | `V2_1 | `Dev] ->
   base:string ->
   variant:Variant.t ->
diff --git a/lib/variant.ml b/lib/variant.ml
index 4b1bc886..5faa97dc 100644
--- a/lib/variant.ml
+++ b/lib/variant.ml
@@ -21,6 +21,16 @@ let docker_tag t =
   t.distribution^"-ocaml-"^pp_ocaml_version t
 let distribution t = t.distribution
 
+let packages t =
+  let version = Ocaml_version.with_patch (Ocaml_version.of_string_exn t.ocaml_version) (Some 0) in
+  let comp =
+    let name, version = Ocaml_version.Opam.V2.package version in
+    name^"."^version
+  in
+  match Ocaml_version.Opam.V2.additional_packages version with
+  | [] -> comp
+  | extras -> comp^","^String.concat "," extras
+
 let pp f t = Fmt.pf f "%s/%s" (docker_tag t) (Ocaml_version.string_of_arch t.arch)
 
 let macos_homebrew = "macos-homebrew"
diff --git a/lib/variant.mli b/lib/variant.mli
index f45d14fb..a2fd33a6 100644
--- a/lib/variant.mli
+++ b/lib/variant.mli
@@ -11,6 +11,8 @@ val docker_tag : t -> string
 val distribution : t -> string
 val os : t -> [`linux | `macOS]
 
+val packages : t -> string
+
 val pp : t Fmt.t
 
 val macos_homebrew : string
diff --git a/service/pipeline.ml b/service/pipeline.ml
index 702edf50..c3baa4d4 100644
--- a/service/pipeline.ml
+++ b/service/pipeline.ml
@@ -58,29 +58,29 @@ let with_label l t =
   let> v = t in
   Current.Primitive.const v
 
-let build_spec ~platform ~opam_version pkg =
+let build_spec ~platform ~local ~opam_version pkg =
   let+ pkg = pkg in
-  Build.Spec.opam ~platform ~lower_bounds:false ~with_tests:false ~opam_version pkg
+  Build.Spec.opam ~platform ~lower_bounds:false ~with_tests:false ~local ~opam_version pkg
 
-let test_spec ~platform ~opam_version pkg =
+let test_spec ~platform ~local ~opam_version pkg =
   let+ pkg = pkg in
-  Build.Spec.opam ~platform ~lower_bounds:false ~with_tests:true ~opam_version pkg
+  Build.Spec.opam ~platform ~lower_bounds:false ~with_tests:true ~local ~opam_version pkg
 
-let lower_bounds_spec ~platform ~opam_version pkg =
+let lower_bounds_spec ~platform ~local ~opam_version pkg =
   let+ pkg = pkg in
-  Build.Spec.opam ~platform ~lower_bounds:true ~with_tests:false ~opam_version pkg
+  Build.Spec.opam ~platform ~lower_bounds:true ~with_tests:false ~local ~opam_version pkg
 
-let revdep_spec ~platform ~opam_version ~revdep pkg =
+let revdep_spec ~platform ~local ~opam_version ~revdep pkg =
   let+ revdep = revdep
   and+ pkg = pkg
   in
-  Build.Spec.opam ~platform ~lower_bounds:false ~with_tests:true ~revdep ~opam_version pkg
+  Build.Spec.opam ~platform ~lower_bounds:false ~with_tests:true ~revdep ~local ~opam_version pkg
 
 (* List the revdeps of [pkg] (using [builder] and [image]) and test each one
    (using [spec] and [base], merging [source] into [master]). *)
-let test_revdeps ~ocluster ~opam_version ~master ~base ~platform ~pkgopt ~after source =
+let test_revdeps ~ocluster ~local ~opam_version ~master ~base ~platform ~pkgopt ~after source =
   let revdeps =
-    Build.list_revdeps ~opam_version ~base ocluster ~platform ~pkgopt ~master ~after source |>
+    Build.list_revdeps ~local ~opam_version ~base ocluster ~platform ~pkgopt ~master ~after source |>
     Current.map OpamPackage.Set.elements
   in
   let pkg = Current.map (fun {PackageOpt.pkg = pkg; urgent = _; has_tests = _} -> pkg) pkgopt in
@@ -89,7 +89,7 @@ let test_revdeps ~ocluster ~opam_version ~master ~base ~platform ~pkgopt ~after
     revdeps
     |> Node.list_map (module OpamPackage) (fun revdep ->
         let image =
-          let spec = revdep_spec ~platform ~opam_version ~revdep pkg in
+          let spec = revdep_spec ~platform ~local ~opam_version ~revdep pkg in
           Build.v ocluster ~label:"build" ~base ~spec ~master ~urgent source
         in
         let label = Current.map OpamPackage.to_string revdep
@@ -109,7 +109,7 @@ let get_significant_available_pkg = function
 let build_with_cluster ~ocluster ~analysis ~lint ~master source =
   let pkgs = Current.map Analyse.Analysis.packages analysis in
   let pkgs = Current.map (List.filter_map get_significant_available_pkg) pkgs in
-  let build ~opam_version ~lower_bounds ~revdeps label variant =
+  let build ?(local=false) ~opam_version ~lower_bounds ~revdeps label variant =
     let arch = Variant.arch variant in
     let pool = Conf.pool_of_arch variant in
     let platform = {Platform.label; pool; variant} in
@@ -138,13 +138,13 @@ let build_with_cluster ~ocluster ~analysis ~lint ~master source =
               Build.Docker (Current_docker.Raw.Image.of_hash repo_id)
         in
         let image =
-          let spec = build_spec ~platform ~opam_version pkg in
+          let spec = build_spec ~platform ~local ~opam_version pkg in
           Build.v ocluster ~label:"build" ~base ~spec ~master ~urgent source in
         let build = Node.action `Built image
         and tests =
           Node.bool_map (fun () ->
             let action =
-              let spec = test_spec ~platform ~opam_version pkg in
+              let spec = test_spec ~platform ~local ~opam_version pkg in
               Build.v ocluster ~label:"test" ~base ~spec ~master ~urgent source
             in
             let action = Node.action `Built action in
@@ -153,7 +153,7 @@ let build_with_cluster ~ocluster ~analysis ~lint ~master source =
         and lower_bounds_check =
           if lower_bounds then
             let action =
-              let spec = lower_bounds_spec ~platform ~opam_version pkg in
+              let spec = lower_bounds_spec ~platform ~local ~opam_version pkg in
               Build.v ocluster ~label:"lower-bounds" ~base ~spec ~master ~urgent source
             in
             let action = Node.action `Built action in
@@ -161,7 +161,7 @@ let build_with_cluster ~ocluster ~analysis ~lint ~master source =
           else
             Node.empty
         and revdeps =
-          if revdeps then test_revdeps ~ocluster ~opam_version ~master ~base ~platform ~pkgopt source ~after:image
+          if revdeps then test_revdeps ~ocluster ~local ~opam_version ~master ~base ~platform ~pkgopt source ~after:image
           else Node.empty
         in
         let label = Current.map OpamPackage.to_string pkg in
@@ -222,17 +222,18 @@ let build_with_cluster ~ocluster ~analysis ~lint ~master source =
   let analysis = Node.action `Analysed analysis
   and lint = Node.action `Linted lint
   and extras =
-    let build ~opam_version ~distro ~arch ~compiler label =
+    let build ?local ~opam_version ~distro ~arch ~compiler label =
       let variant = Variant.v ~arch ~distro ~compiler in
       let label = if String.equal label "" then "" else label^"-" in
       let label = Fmt.str "%socaml-%s" label (Variant.pp_ocaml_version variant) in
-      build ~opam_version ~lower_bounds:false ~revdeps:false label variant
+      build ?local ~opam_version ~lower_bounds:false ~revdeps:false label variant
     in
     let master_distro = Distro.tag_of_distro master_distro in
     List.fold_left (fun acc comp_full ->
       let comp = Ocaml_version.to_string (Ocaml_version.with_just_major_and_minor comp_full) in
       build ~opam_version:`V2_0 ~arch:`X86_64 ~distro:master_distro ~compiler:(comp, None) "opam-2.0" ::
       build ~opam_version:`V2_1 ~arch:`X86_64 ~distro:master_distro ~compiler:(comp, None) "opam-2.1" ::
+      build ~local:true ~opam_version ~arch:`X86_64 ~distro:master_distro ~compiler:(comp, None) "local-switch" ::
       List.filter_map (fun v ->
         match Ocaml_version.extra v with
         | None -> None