diff --git a/pyproject.toml b/pyproject.toml
index cff7e24..c3fb216 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -10,6 +10,7 @@ packages = [
 	{ include = "signaloid", from = "src" }
 ]
 
+
 [tool.poetry-dynamic-versioning]
 enable = true
 vcs = "git"
@@ -30,7 +31,7 @@ types-tabulate = "^0.9.0"
 types-PyYAML = "^6.0.0"
 
 [build-system]
-requires = ["poetry-core>=1.0.0", "poetry-dynamic-versioning>=1.0.0,<2.0.0"]
+requires = ["poetry-core>=1.9.1", "poetry-dynamic-versioning>=1.0.0,<2.0.0"]
 build-backend = "poetry_dynamic_versioning.backend"
 
 [tool.poetry.dependencies]
@@ -52,6 +53,7 @@ scipy = [
 	{ version = ">=1.14.0", python = ">=3.11" },
 ]
 
+
 [tool.poetry.extras]
 sheets = ["gspread", "google-api-python-client", "oauth2client"]
 
@@ -64,6 +66,13 @@ strict = true
 disallow_any_generics = false
 python_version = "3.10"
 exclude = '(^|/)\.venv/'
+# `signaloid` is a PEP 420 namespace package, so it has no top-level `py.typed`
+# marker. Resolve it from the source tree (via `mypy_path`) rather than as an
+# installed distribution, so `mypy -p signaloid` type-checks the sources
+# directly instead of failing on the absent namespace-level marker.
+mypy_path = "src"
+namespace_packages = true
+explicit_package_bases = true
 
 [[tool.mypy.overrides]]
 module = [
diff --git a/src/signaloid/__init__.py b/src/signaloid/__init__.py
deleted file mode 100644
index 860f233..0000000
--- a/src/signaloid/__init__.py
+++ /dev/null
@@ -1,6 +0,0 @@
-from .distributional import DistributionalValue, DiracDelta
-
-__all__ = [
-    "DistributionalValue",
-    "DiracDelta",
-]
diff --git a/src/signaloid/py.typed b/src/signaloid/circuitpython/py.typed
similarity index 100%
rename from src/signaloid/py.typed
rename to src/signaloid/circuitpython/py.typed
diff --git a/src/signaloid/distributional/distributional.py b/src/signaloid/distributional/distributional.py
index fe325be..8807a2d 100644
--- a/src/signaloid/distributional/distributional.py
+++ b/src/signaloid/distributional/distributional.py
@@ -59,6 +59,8 @@
     },
 }
 
+UR_TYPE_ATHENS = 0x04
+
 # First byte of the Ux Binary Data format, used to distinguish it from the legacy format
 UX_BINARY_FORMAT_MARKER = 0xF0
 
@@ -67,16 +69,17 @@ class DistributionalValue:
     def __init__(
         self,
         particle_value: float | None = None,
-        UR_type: int | None = None,
+        UR_type: int = UR_TYPE_ATHENS,
         dirac_deltas: list[DiracDelta] | None = None,
         double_precision: bool = True,
     ) -> None:
         self.particle_value: float | None = particle_value
-        self.UR_type: int | None = UR_type
+        self.UR_type: int = UR_type
         self._dirac_deltas: list[DiracDelta] = (
             dirac_deltas if dirac_deltas is not None else []
         )
         self.double_precision = double_precision
+
         """
         properties
         """
diff --git a/src/signaloid/distributional/py.typed b/src/signaloid/distributional/py.typed
new file mode 100644
index 0000000..e69de29
diff --git a/src/signaloid/distributional_distance/py.typed b/src/signaloid/distributional_distance/py.typed
new file mode 100644
index 0000000..e69de29
diff --git a/src/signaloid/distributional_information_plotting/py.typed b/src/signaloid/distributional_information_plotting/py.typed
new file mode 100644
index 0000000..e69de29
diff --git a/src/signaloid/statistical_tests/py.typed b/src/signaloid/statistical_tests/py.typed
new file mode 100644
index 0000000..e69de29
diff --git a/src/signaloid/uxdata_toolkit.py b/src/signaloid/uxdata_toolkit/__init__.py
similarity index 99%
rename from src/signaloid/uxdata_toolkit.py
rename to src/signaloid/uxdata_toolkit/__init__.py
index d57419c..90ce787 100644
--- a/src/signaloid/uxdata_toolkit.py
+++ b/src/signaloid/uxdata_toolkit/__init__.py
@@ -283,7 +283,3 @@ def main(argv: list[str] | None = None) -> None:
     else:
         print("Unknown command. Use -h for help.")
         sys.exit(1)
-
-
-if __name__ == "__main__":
-    main()
diff --git a/src/signaloid/uxdata_toolkit/__main__.py b/src/signaloid/uxdata_toolkit/__main__.py
new file mode 100644
index 0000000..f0963ea
--- /dev/null
+++ b/src/signaloid/uxdata_toolkit/__main__.py
@@ -0,0 +1,30 @@
+#   Copyright (c) 2026, Signaloid.
+#
+#   Permission is hereby granted, free of charge, to any person obtaining a copy
+#   of this software and associated documentation files (the "Software"), to
+#   deal in the Software without restriction, including without limitation the
+#   rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+#   sell copies of the Software, and to permit persons to whom the Software is
+#   furnished to do so, subject to the following conditions:
+#
+#   The above copyright notice and this permission notice shall be included in
+#   all copies or substantial portions of the Software.
+#
+#   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+#   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+#   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+#   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+#   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+#   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+#   DEALINGS IN THE SOFTWARE.
+
+"""
+Entry point for running the Ux Data Toolkit as a module:
+
+    python -m signaloid.uxdata_toolkit
+"""
+
+from signaloid.uxdata_toolkit import main
+
+if __name__ == "__main__":
+    main()
diff --git a/src/signaloid/uxdata_toolkit/py.typed b/src/signaloid/uxdata_toolkit/py.typed
new file mode 100644
index 0000000..e69de29
diff --git a/src/signaloid/uxdata_toolkit_test.py b/src/signaloid/uxdata_toolkit/uxdata_toolkit_test.py
similarity index 100%
rename from src/signaloid/uxdata_toolkit_test.py
rename to src/signaloid/uxdata_toolkit/uxdata_toolkit_test.py