diff --git a/test/blackbox-tests/test-cases/deprecated-library-name/features.t b/test/blackbox-tests/test-cases/deprecated-library-name/features.t
index 3416bd29daaf..5d826871ca4b 100644
--- a/test/blackbox-tests/test-cases/deprecated-library-name/features.t
+++ b/test/blackbox-tests/test-cases/deprecated-library-name/features.t
@@ -96,8 +96,7 @@ that wasn't found:
   1 | (executable (name prog) (libraries a))
                                          ^
   Error: Library "a" not found.
-  -> required by _build/default/c/.prog.eobjs/byte/dune__exe__Prog.cmi
-  -> required by _build/default/c/.prog.eobjs/native/dune__exe__Prog.cmx
+  -> required by _build/default/c/.merlin-conf/exe-prog
   -> required by _build/default/c/prog.exe
   [1]
 
diff --git a/test/blackbox-tests/test-cases/enabled_if/eif-context_name.t/run.t b/test/blackbox-tests/test-cases/enabled_if/eif-context_name.t/run.t
index b35f3c2886b1..cf92d493de60 100644
--- a/test/blackbox-tests/test-cases/enabled_if/eif-context_name.t/run.t
+++ b/test/blackbox-tests/test-cases/enabled_if/eif-context_name.t/run.t
@@ -34,8 +34,7 @@ dune >= 2.8
   18 |  (libraries bar))
                    ^^^
   Error: Library "bar" in _build/default is hidden (unsatisfied 'enabled_if').
-  -> required by _build/default/.bar_exe.eobjs/byte/dune__exe__Bar_exe.cmi
-  -> required by _build/default/.bar_exe.eobjs/native/dune__exe__Bar_exe.cmx
+  -> required by _build/default/.merlin-conf/exe-bar_exe
   -> required by _build/default/bar_exe.exe
   [1]
 
diff --git a/test/blackbox-tests/test-cases/enabled_if/eif-ocaml_version.t/run.t b/test/blackbox-tests/test-cases/enabled_if/eif-ocaml_version.t/run.t
index a604bbb08d5a..21ee608cca8b 100644
--- a/test/blackbox-tests/test-cases/enabled_if/eif-ocaml_version.t/run.t
+++ b/test/blackbox-tests/test-cases/enabled_if/eif-ocaml_version.t/run.t
@@ -10,7 +10,6 @@ This one is disabled (version too low)
                    ^^^^^^^^^^
   Error: Library "futurecaml" in _build/default is hidden (unsatisfied
   'enabled_if').
-  -> required by _build/default/.main2.eobjs/byte/dune__exe__Main2.cmi
-  -> required by _build/default/.main2.eobjs/native/dune__exe__Main2.cmx
+  -> required by _build/default/.merlin-conf/exe-main2
   -> required by _build/default/main2.exe
   [1]
diff --git a/test/blackbox-tests/test-cases/enabled_if/eif-simple.t/run.t b/test/blackbox-tests/test-cases/enabled_if/eif-simple.t/run.t
index d0f07cbe00a5..cf66be46c43d 100644
--- a/test/blackbox-tests/test-cases/enabled_if/eif-simple.t/run.t
+++ b/test/blackbox-tests/test-cases/enabled_if/eif-simple.t/run.t
@@ -30,5 +30,6 @@ Test the enabled_if field for libraries:
   Error: Library "foo" in _build/default is hidden (unsatisfied 'enabled_if').
   -> required by library "bar" in _build/default
   -> required by executable main in dune:44
+  -> required by _build/default/.merlin-conf/exe-main
   -> required by _build/default/main.exe
   [1]
diff --git a/test/blackbox-tests/test-cases/exec-missing.t/run.t b/test/blackbox-tests/test-cases/exec-missing.t/run.t
index c679a3aa281b..bd807ea84875 100644
--- a/test/blackbox-tests/test-cases/exec-missing.t/run.t
+++ b/test/blackbox-tests/test-cases/exec-missing.t/run.t
@@ -5,5 +5,6 @@ When using dune exec, the external-lib-deps command refers to the executable:
   3 |  (libraries does-not-exist))
                   ^^^^^^^^^^^^^^
   Error: Library "does-not-exist" not found.
+  -> required by _build/default/.merlin-conf/exe-x
   -> required by _build/default/x.exe
   [1]
diff --git a/test/blackbox-tests/test-cases/forbidden_libraries.t b/test/blackbox-tests/test-cases/forbidden_libraries.t
index a92a7aec0049..d774cb4e77c9 100644
--- a/test/blackbox-tests/test-cases/forbidden_libraries.t
+++ b/test/blackbox-tests/test-cases/forbidden_libraries.t
@@ -24,7 +24,6 @@ Test the `forbidden_libraries` feature
   -> required by library "b" in _build/default
   -> required by library "c" in _build/default
   -> required by executable main in dune:5
-  -> required by _build/default/.main.eobjs/byte/dune__exe__Main.cmi
-  -> required by _build/default/.main.eobjs/native/dune__exe__Main.cmx
+  -> required by _build/default/.merlin-conf/exe-main
   -> required by _build/default/main.exe
   [1]
diff --git a/test/blackbox-tests/test-cases/invalid-dune-package.t b/test/blackbox-tests/test-cases/invalid-dune-package.t
index 68874fdf6ab7..350cad878a39 100644
--- a/test/blackbox-tests/test-cases/invalid-dune-package.t
+++ b/test/blackbox-tests/test-cases/invalid-dune-package.t
@@ -17,7 +17,6 @@ Now we attempt to use an invalid dune-package library:
   $ OCAMLPATH=$PWD/findlib dune exec ./foo.exe
   File "$TESTCASE_ROOT/findlib/baz/dune-package", line 1, characters 0-0:
   Error: Invalid first line, expected: (lang <lang> <version>)
-  -> required by _build/default/.foo.eobjs/byte/dune__exe__Foo.cmi
-  -> required by _build/default/.foo.eobjs/native/dune__exe__Foo.cmx
+  -> required by _build/default/.merlin-conf/exe-foo
   -> required by _build/default/foo.exe
   [1]
diff --git a/test/blackbox-tests/test-cases/optional-executable.t b/test/blackbox-tests/test-cases/optional-executable.t
index 640b562d224b..c70ae3e02b0d 100644
--- a/test/blackbox-tests/test-cases/optional-executable.t
+++ b/test/blackbox-tests/test-cases/optional-executable.t
@@ -26,8 +26,7 @@ Test optional executable
   3 |  (libraries does-not-exist)
                   ^^^^^^^^^^^^^^
   Error: Library "does-not-exist" not found.
-  -> required by _build/default/.x.eobjs/byte/dune__exe__X.cmi
-  -> required by _build/default/.x.eobjs/native/dune__exe__X.cmx
+  -> required by _build/default/.merlin-conf/exe-x
   -> required by _build/default/x.exe
   -> required by alias all
   [1]
@@ -37,8 +36,7 @@ Test optional executable
   3 |  (libraries does-not-exist)
                   ^^^^^^^^^^^^^^
   Error: Library "does-not-exist" not found.
-  -> required by _build/default/.x.eobjs/byte/dune__exe__X.cmi
-  -> required by _build/default/.x.eobjs/native/dune__exe__X.cmx
+  -> required by _build/default/.merlin-conf/exe-x
   -> required by _build/default/x.exe
   -> required by %{exe:x.exe} at dune:8
   -> required by alias run-x in dune:6
@@ -60,8 +58,7 @@ The following command should fail because the executable is not optional:
   3 |  (libraries does-not-exist))
                   ^^^^^^^^^^^^^^
   Error: Library "does-not-exist" not found.
-  -> required by _build/default/.x.eobjs/byte/dune__exe__X.cmi
-  -> required by _build/default/.x.eobjs/native/dune__exe__X.cmx
+  -> required by _build/default/.merlin-conf/exe-x
   -> required by _build/default/x.exe
   -> required by _build/install/default/bin/x
   -> required by _build/default/x.install
@@ -152,8 +149,7 @@ present even if the binary is not optional.
   3 |  (libraries doesnotexistatall)
                   ^^^^^^^^^^^^^^^^^
   Error: Library "doesnotexistatall" not found.
-  -> required by _build/default/exe/.bar.eobjs/byte/dune__exe__Bar.cmi
-  -> required by _build/default/exe/.bar.eobjs/native/dune__exe__Bar.cmx
+  -> required by _build/default/exe/.merlin-conf/exe-bar
   -> required by _build/default/exe/bar.exe
   -> required by _build/install/default/bin/dunetestbar
   -> required by %{bin:dunetestbar} at dune:3
diff --git a/test/blackbox-tests/test-cases/overlapping-deps.t b/test/blackbox-tests/test-cases/overlapping-deps.t
index e2d80c2442f9..6fc73cb15b15 100644
--- a/test/blackbox-tests/test-cases/overlapping-deps.t
+++ b/test/blackbox-tests/test-cases/overlapping-deps.t
@@ -67,7 +67,7 @@ And we see the error:
     $TESTCASE_ROOT/use/../external/_build/install/default/lib/some_package2
     -> required by library "some_package1" in
        $TESTCASE_ROOT/use/../external/_build/install/default/lib/some_package1
-  -> required by _build/default/proj2/.bar.objs/byte/bar.cmo
+  -> required by _build/default/proj2/.merlin-conf/lib-bar
   -> required by _build/default/proj2/bar.cma
   -> required by %{cma:proj2/bar} at command line:1
   [1]
@@ -106,7 +106,6 @@ We also make sure the error exists for executables:
     -> required by library "some_package1" in
        $TESTCASE_ROOT/use/../external/_build/install/default/lib/some_package1
   -> required by executable bar in proj2/dune:2
-  -> required by _build/default/proj2/.bar.eobjs/byte/dune__exe__Bar.cmi
-  -> required by _build/default/proj2/.bar.eobjs/native/dune__exe__Bar.cmx
+  -> required by _build/default/proj2/.merlin-conf/exe-bar
   -> required by _build/default/proj2/bar.exe
   [1]
diff --git a/test/blackbox-tests/test-cases/pkg/ocamlformat/ocamlformat-dev-tool-deps-conflict-project-deps.t b/test/blackbox-tests/test-cases/pkg/ocamlformat/ocamlformat-dev-tool-deps-conflict-project-deps.t
index 645e741baf1e..8dde4bd3473b 100644
--- a/test/blackbox-tests/test-cases/pkg/ocamlformat/ocamlformat-dev-tool-deps-conflict-project-deps.t
+++ b/test/blackbox-tests/test-cases/pkg/ocamlformat/ocamlformat-dev-tool-deps-conflict-project-deps.t
@@ -126,8 +126,7 @@ There is no leak here. It is not taking the "printer" lib from dev-tools.
   3 |  (libraries printer))
                   ^^^^^^^
   Error: Library "printer" not found.
-  -> required by _build/default/.foo.eobjs/byte/dune__exe__Foo.cmi
-  -> required by _build/default/.foo.eobjs/native/dune__exe__Foo.cmx
+  -> required by _build/default/.merlin-conf/exe-foo
   -> required by _build/default/foo.exe
   -> required by _build/install/default/bin/foo
   [1]
diff --git a/test/blackbox-tests/test-cases/ppx/ppx-runtime-dependencies.t/run.t b/test/blackbox-tests/test-cases/ppx/ppx-runtime-dependencies.t/run.t
index d0796bcfd73a..547478a26165 100644
--- a/test/blackbox-tests/test-cases/ppx/ppx-runtime-dependencies.t/run.t
+++ b/test/blackbox-tests/test-cases/ppx/ppx-runtime-dependencies.t/run.t
@@ -114,8 +114,7 @@ not been marked with (kind ppx_rewriter).
                         ^
   Error: Ppx dependency on a non-ppx library "b". If "b" is in fact a ppx
   rewriter library, it should have (kind ppx_rewriter) in its dune file.
-  -> required by _build/default/bin/.main.eobjs/byte/dune__exe__Main.cmi
-  -> required by _build/default/bin/.main.eobjs/native/dune__exe__Main.cmx
+  -> required by _build/default/bin/.merlin-conf/exe-main
   -> required by _build/default/bin/main.exe
   [1]
 
diff --git a/test/blackbox-tests/test-cases/virtual-libraries/double-implementation.t/run.t b/test/blackbox-tests/test-cases/virtual-libraries/double-implementation.t/run.t
index 25a90548ffd4..830e6358ba03 100644
--- a/test/blackbox-tests/test-cases/virtual-libraries/double-implementation.t/run.t
+++ b/test/blackbox-tests/test-cases/virtual-libraries/double-implementation.t/run.t
@@ -7,6 +7,7 @@ Executable that tries to use two implementations for the same virtual lib
   - "impl2" in _build/default/impl2
   This cannot work.
   -> required by executable foo in dune:2
+  -> required by _build/default/.merlin-conf/exe-foo
   -> required by _build/default/foo.exe
   -> required by alias default in dune:11
   [1]
diff --git a/test/blackbox-tests/test-cases/virtual-libraries/github2896.t b/test/blackbox-tests/test-cases/virtual-libraries/github2896.t
index 0292384712ba..db616d0af6b6 100644
--- a/test/blackbox-tests/test-cases/virtual-libraries/github2896.t
+++ b/test/blackbox-tests/test-cases/virtual-libraries/github2896.t
@@ -23,8 +23,8 @@ where vlib is a virtual library, and impl implements this library.
   Error: Library "vlib" was pulled in.
   -> required by library "lib" in _build/default/lib
   -> required by library "impl" in _build/default/impl
-  -> required by _build/default/impl/.impl.objs/byte/vlib.cmo
-  -> required by _build/default/impl/impl.cma
+  -> required by _build/default/impl/.merlin-conf/lib-impl
+  -> required by _build/default/impl/vlib__impl__.ml-gen
   -> required by alias impl/all
   [1]
 
@@ -37,7 +37,6 @@ The implementation impl was built, but it's not usable:
   -> required by library "lib" in _build/default/lib
   -> required by library "impl" in _build/default/impl
   -> required by executable foo in dune:1
-  -> required by _build/default/.foo.eobjs/byte/dune__exe__Foo.cmi
-  -> required by _build/default/.foo.eobjs/native/dune__exe__Foo.cmx
+  -> required by _build/default/.merlin-conf/exe-foo
   -> required by _build/default/foo.exe
   [1]
diff --git a/test/blackbox-tests/test-cases/virtual-libraries/missing-implementation.t/run.t b/test/blackbox-tests/test-cases/virtual-libraries/missing-implementation.t/run.t
index ea95323aacb4..d1a0203ee714 100644
--- a/test/blackbox-tests/test-cases/virtual-libraries/missing-implementation.t/run.t
+++ b/test/blackbox-tests/test-cases/virtual-libraries/missing-implementation.t/run.t
@@ -3,6 +3,7 @@ Executable that tries to build against a virtual library without an implementati
   Error: No implementation found for virtual library "vlib" in
   _build/default/vlib.
   -> required by executable foo in dune:2
+  -> required by _build/default/.merlin-conf/exe-foo
   -> required by _build/default/foo.exe
   -> required by alias default in dune:5
   [1]
diff --git a/test/blackbox-tests/test-cases/virtual-libraries/virtual-modules-excluded-by-modules-field.t b/test/blackbox-tests/test-cases/virtual-libraries/virtual-modules-excluded-by-modules-field.t
index 3598ec206985..454cd8e3ea23 100644
--- a/test/blackbox-tests/test-cases/virtual-libraries/virtual-modules-excluded-by-modules-field.t
+++ b/test/blackbox-tests/test-cases/virtual-libraries/virtual-modules-excluded-by-modules-field.t
@@ -76,7 +76,6 @@ This should be ignored if we are in vendored_dirs
   Error: No implementation found for virtual library "foo" in
   _build/default/src.
   -> required by executable bar in dune:3
-  -> required by _build/default/.bar.eobjs/byte/dune__exe__Bar.cmi
-  -> required by _build/default/.bar.eobjs/native/dune__exe__Bar.cmx
+  -> required by _build/default/.merlin-conf/exe-bar
   -> required by _build/default/bar.exe
   [1]
diff --git a/test/blackbox-tests/test-cases/virtual-libraries/vlib-wrong-default-impl.t/run.t b/test/blackbox-tests/test-cases/virtual-libraries/vlib-wrong-default-impl.t/run.t
index 772372a657c0..ce661aece294 100644
--- a/test/blackbox-tests/test-cases/virtual-libraries/vlib-wrong-default-impl.t/run.t
+++ b/test/blackbox-tests/test-cases/virtual-libraries/vlib-wrong-default-impl.t/run.t
@@ -4,8 +4,7 @@ library is not actually an implementation of the virtual library.
   $ dune build @default
   Error: "not_an_implem" is not an implementation of "vlibfoo".
   -> required by executable exe in exe/dune:2
-  -> required by _build/default/exe/.exe.eobjs/byte/dune__exe__Exe.cmi
-  -> required by _build/default/exe/.exe.eobjs/native/dune__exe__Exe.cmx
+  -> required by _build/default/exe/.merlin-conf/exe-exe
   -> required by _build/default/exe/exe.exe
   -> required by alias exe/default in exe/dune:5
   [1]