diff --git a/master_changes.md b/master_changes.md
index 68d5e27b4c5..7ef1490b99c 100644
--- a/master_changes.md
+++ b/master_changes.md
@@ -26,6 +26,7 @@ users)
 ## Actions
 
 ## Install
+  * Remove the build directory as soon as possible when installing a package [#6906 @kit-ty-kate - fix #5884]
 
 ## Build (package)
 
@@ -148,6 +149,7 @@ users)
 
 ## Benchmarks
   * Add an even larger real-world diff to benchmark `opam update` [#6567 @kit-ty-kate]
+  * Add a benchmark for `opam install` [#6912 @kit-ty-kate]
 
 ## Reftests
 ### Tests
diff --git a/src/client/opamSolution.ml b/src/client/opamSolution.ml
index 9696b657594..2ff232eb526 100644
--- a/src/client/opamSolution.ml
+++ b/src/client/opamSolution.ml
@@ -683,6 +683,14 @@ let parallel_apply t
        | Left conf ->
          add_to_install nv conf;
          store_time ();
+         if not OpamClientConfig.(!r.keep_build_dir) then begin
+           (* NOTE: build_dir as defined above is the
+              "build dir in case of --inplace" so != OpamPath.Switch.build *)
+           let build_dir =
+             OpamPath.Switch.build t.switch_global.root t.switch nv
+           in
+           OpamFilename.rmdir build_dir;
+         end;
          Done (`Successful (OpamPackage.Set.add nv installed, removed))
        | Right exn ->
          store_time ();
@@ -864,17 +872,13 @@ let parallel_apply t
   end;
 
   let cleanup_artefacts graph =
+    (* NOTE: build dir removal is done directly after install
+       instead of here, for performance reasons. *)
     PackageActionGraph.iter_vertex (function
         | `Remove nv ->
           OpamAction.cleanup_package_artefacts t nv
           (* if reinstalled, only removes build dir *)
-        | `Install nv ->
-          if not OpamClientConfig.(!r.keep_build_dir) then
-            let build_dir =
-              OpamPath.Switch.build t.switch_global.root t.switch nv
-            in
-            OpamFilename.rmdir build_dir
-        | `Build _ | `Fetch _ -> ()
+        | `Build _ | `Fetch _ | `Install _ -> ()
         | `Change _ | `Reinstall _  -> assert false)
       graph
   in
diff --git a/tests/bench/bench.ml b/tests/bench/bench.ml
index c7b155144a9..d8ddd72ac2c 100644
--- a/tests/bench/bench.ml
+++ b/tests/bench/bench.ml
@@ -136,6 +136,37 @@ let () =
     in
     List.fold_left (+.) 0.0 l /. float_of_int n
   in
+  let time_install_core =
+    Gc.compact ();
+    launch (fmt "%s switch create -y eight ocaml-base-compiler.4.14.0" bin);
+    launch (fmt "%s install --download-only -y core.v0.15.1" bin);
+    launch "test -d ~/.opam/eight/.opam-switch/sources && rm -rf ~/.opam/eight/.opam-switch/sources";
+    launch "test -d ~/.opam/eight/.opam-switch/build && rm -rf ~/.opam/eight/.opam-switch/build";
+    time_cmd ~exit:0 (fmt "%s install -y core.v0.15.1" bin)
+  in
+  let time_install_big =
+    Gc.compact ();
+    launch (fmt "%s switch create nine --empty" bin);
+    OpamSystem.write "/tmp/opam-bench-bigpkg/repo" {|opam-version: "2.0"
+|};
+    OpamSystem.write "/tmp/opam-bench-bigpkg/packages/a.1/opam" {|opam-version: "2.0"
+url {
+  src: "https://github.com/ocaml/opam-repository/archive/refs/tags/2025-01-before-archiving-phase1.tar.gz"
+  checksum: "md5=215a5261ad8358e34eb3222b83c4c8be"
+}
+|};
+    OpamSystem.write "/tmp/opam-bench-bigpkg/packages/b.1/opam" {|opam-version: "2.0"
+build: ["rm" "-r" "packages"]
+url {
+  src: "https://github.com/ocaml/opam-repository/archive/refs/tags/2025-01-before-archiving-phase1.tar.gz"
+  checksum: "md5=215a5261ad8358e34eb3222b83c4c8be"
+}
+|};
+    launch (fmt "%s repo add tmp /tmp/opam-bench-bigpkg" bin);
+    let res = time_cmd ~exit:0 (fmt "%s install a.1 b.1" bin) in
+    launch (fmt "%s repo remove tmp -a" bin);
+    res
+  in
   let init_root tmp_root_dir repo =
     launch (fmt "rm -rf %s" tmp_root_dir);
     launch (fmt "mkdir -p %s" tmp_root_dir);
@@ -279,6 +310,16 @@ let () =
           "name": "OpamStd.String.split amortised over 10 runs",
           "value": %f,
           "units": "secs"
+        },
+        {
+          "name": "opam install core.v0.15.1",
+          "value": %f,
+          "units": "secs"
+        },
+        {
+          "name": "opam install large-pkg large-pkg2",
+          "value": %f,
+          "units": "secs"
         }
       ]
     },
@@ -363,6 +404,8 @@ let () =
       time_show_raw
       time_show_precise
       time_OpamStd_String_split_10
+      time_install_core
+      time_install_big
       time_update_no_diff_local
       time_update_no_diff_git
       time_update_small_diff_local