diff --git a/nonos/api/analysis.py b/nonos/api/analysis.py
index 70f77812..044d8ed3 100644
--- a/nonos/api/analysis.py
+++ b/nonos/api/analysis.py
@@ -448,7 +448,7 @@ def __init__(
         *,
         inifile: str = "",
         code: str = "",
-        directory="",
+        directory: Optional[str] = None,
         rotate_by: Optional[float] = None,
         rotate_with: Optional[str] = None,
         rotate_grid: int = -1,  # deprecated
@@ -462,6 +462,8 @@ def __init__(
 
         self.inifile = inifile
         self.code = code
+        if directory is None:
+            directory = os.getcwd()
         self.directory = directory
         self._rotate_by = _parse_rotation_angle(
             rotate_by=rotate_by,
@@ -1533,9 +1535,21 @@ def __init__(
         inifile: str = "",
         code: str = "",
         geometry: str = "unknown",
-        directory: str = "",
+        directory: Optional[str] = None,
         fluid: Optional[str] = None,
     ) -> None:
+        if isinstance(input_dataset, str):
+            directory_from_input = os.path.dirname(input_dataset)
+            if directory is None:
+                directory = directory_from_input
+            elif os.path.abspath(directory_from_input) != os.path.abspath(directory):
+                raise ValueError(
+                    f"directory value {directory!r} does not match "
+                    f"directory name from input_dataset ({directory_from_input!r})"
+                )
+            del directory_from_input
+            input_dataset = os.path.basename(input_dataset)
+
         self.params = Parameters(inifile=inifile, code=code, directory=directory)
         self._read = self.params.loadSimuFile(
             input_dataset, geometry=geometry, cell="edges", fluid=fluid
diff --git a/nonos/api/from_simulation.py b/nonos/api/from_simulation.py
index 4a3bfd8f..e9043751 100644
--- a/nonos/api/from_simulation.py
+++ b/nonos/api/from_simulation.py
@@ -43,7 +43,14 @@ def __init__(
         code: Optional[str] = None,
         directory: Optional[str] = None,
     ) -> None:
-        self.directory = directory or ""
+        if not directory:
+            directory = os.getcwd()
+        elif not os.path.exists(directory):
+            raise FileNotFoundError(f"No such file or directory {directory}")
+        elif not os.path.isdir(directory):
+            raise ValueError(f"{directory} is not a directory")
+
+        self.directory = directory
         self.paramfile = inifile or ""
         self.code: Code
         if code:
@@ -311,7 +318,7 @@ def funnel_on_type(
     elif _code is Code.IDEFIX or _code is Code.PLUTO:
         if isinstance(input_dataset, str):
             filename = os.path.join(directory, input_dataset)
-            if (m := re.search(r"\d+", filename)) is None:
+            if (m := re.search(r"\d+", input_dataset)) is None:
                 raise ValueError("filename format is not correct")
             else:
                 on = int(m.group())
@@ -441,7 +448,7 @@ def idfxReadVTK(
         if V.geometry == "unknown":
             raise RuntimeError(
                 "Geometry couldn't be determined from data. "
-                "Try to set the geometry keyword argument explicitely."
+                "Try to set the geometry keyword argument explicitly."
             )
 
         slist = s.split()  # DIMENSIONS....
diff --git a/tests/test_load_data.py b/tests/test_load_data.py
index 557504e9..5873d95c 100644
--- a/tests/test_load_data.py
+++ b/tests/test_load_data.py
@@ -57,18 +57,28 @@ def test_roundtrip_other_dir(test_data_dir, tmp_path):
     assert dsnpy.nfields == 1
 
 
-def test_api_vtk_by_name(test_data_dir):
-    os.chdir(test_data_dir / "idefix_spherical_planet3d")
-
-    on = 500
-
-    ds = GasDataSet(f"data.{on:04d}.vtk")
-    assert ds.on == on
+@pytest.mark.parametrize(
+    "from_abs_path",
+    [
+        pytest.param(True, id="from absolute path"),
+        pytest.param(False, id="from relative path"),
+    ],
+)
+def test_api_vtk_by_name(test_data_dir, from_abs_path):
+    data_dir = test_data_dir / "idefix_spherical_planet3d"
+    if from_abs_path:
+        input_ = str((data_dir / "data.0500.vtk").absolute())
+    else:
+        os.chdir(data_dir)
+        input_ = "data.0500.vtk"
+
+    ds = GasDataSet(input_)
+    assert ds.on == 500
 
     with pytest.raises(
-        FileNotFoundError, match="In idfxReadVTK: datawrong.0500.vtk not found."
+        FileNotFoundError, match=r"In idfxReadVTK: .*datawrong\.0500\.vtk not found\."
     ):
-        GasDataSet(f"datawrong.{on:04d}.vtk")
+        GasDataSet(input_.replace("data.0500", "datawrong.0500"))
 
 
 def test_api_vtk_by_name_fargo(test_data_dir):