diff --git a/.gitignore b/.gitignore
index 18e905c..669f8f0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -26,6 +26,7 @@ Thumbs.db
 
 # Nix Cache to speed up tests
 .nix/
+.nix-dev-installed
 
 # Ignore logs
 *.log
diff --git a/flake.nix b/flake.nix
index 44ed837..5ade11f 100644
--- a/flake.nix
+++ b/flake.nix
@@ -25,7 +25,7 @@
       ##########################################################################
       packages = forAllSystems (system:
         let
-          pkgs = nixpkgs.legacyPackages.${system};
+          pkgs   = nixpkgs.legacyPackages.${system};
           pyPkgs = pkgs.python311Packages;
         in
         rec {
@@ -45,7 +45,7 @@
               pyPkgs.wheel
             ];
 
-            # Runtime dependencies (matches [project.dependencies])
+            # Runtime dependencies (matches [project.dependencies] in pyproject.toml)
             propagatedBuildInputs = [
               pyPkgs.pyyaml
               pyPkgs.pip
@@ -55,6 +55,7 @@
 
             pythonImportsCheck = [ "pkgmgr" ];
           };
+
           default = pkgmgr;
         }
       );
@@ -65,29 +66,35 @@
       devShells = forAllSystems (system:
         let
           pkgs = nixpkgs.legacyPackages.${system};
-          pkgmgrPkg = self.packages.${system}.pkgmgr;
 
           ansiblePkg =
             if pkgs ? ansible-core then pkgs.ansible-core
             else pkgs.ansible;
 
-          # Python 3 + pip für alles, was "python3 -m pip" macht
-          pythonWithPip = pkgs.python3.withPackages (ps: [
+          # Python 3.11 + pip + PyYAML direkt aus Nix
+          pythonWithDeps = pkgs.python311.withPackages (ps: [
             ps.pip
+            ps.pyyaml
           ]);
         in
         {
           default = pkgs.mkShell {
             buildInputs = [
-              pythonWithPip
-              pkgmgrPkg
+              pythonWithDeps
               pkgs.git
               ansiblePkg
             ];
 
             shellHook = ''
+              # Ensure src/ layout is importable:
+              #   pkgmgr lives in ./src/pkgmgr
+              export PYTHONPATH="$PWD/src:${PYTHONPATH:-}"
+              # Also add repo root in case tools/tests rely on it
+              export PYTHONPATH="$PWD:$PYTHONPATH"
+
               echo "Entered pkgmgr development shell for ${system}"
-              echo "pkgmgr CLI is available via the flake build"
+              echo "pkgmgr CLI (from source) is available via:"
+              echo "  python -m pkgmgr.cli --help"
             '';
           };
         }
diff --git a/pyproject.toml b/pyproject.toml
index f2013ce..31906a4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -49,4 +49,3 @@ include = ["pkgmgr*", "config*"]
 
 [tool.setuptools.package-data]
 "config" = ["defaults.yaml"]
-
diff --git a/scripts/test/test-integration.sh b/scripts/test/test-integration.sh
index c9a445d..63f82a2 100755
--- a/scripts/test/test-integration.sh
+++ b/scripts/test/test-integration.sh
@@ -20,7 +20,7 @@ docker run --rm \
     set -e;
     git config --global --add safe.directory /src || true;
     nix develop .#default --no-write-lock-file -c \
-      python -m unittest discover \
+      python3 -m unittest discover \
         -s tests/integration \
         -t /src \
         -p "$TEST_PATTERN";
diff --git a/scripts/test/test-unit.sh b/scripts/test/test-unit.sh
index d470852..45508e7 100755
--- a/scripts/test/test-unit.sh
+++ b/scripts/test/test-unit.sh
@@ -20,7 +20,7 @@ docker run --rm \
     set -e;
     git config --global --add safe.directory /src || true;
     nix develop .#default --no-write-lock-file -c \
-      python -m unittest discover \
+      python3 -m unittest discover \
         -s tests/unit \
         -t /src \
         -p "$TEST_PATTERN";
diff --git a/src/pkgmgr/__init__.py b/src/pkgmgr/__init__.py
index e69de29..42bb4c7 100644
--- a/src/pkgmgr/__init__.py
+++ b/src/pkgmgr/__init__.py
@@ -0,0 +1,14 @@
+from __future__ import annotations
+
+"""
+Top-level package for Kevin's package manager (pkgmgr).
+
+We re-export the CLI subpackage as the attribute ``cli`` so that
+``pkgutil.resolve_name("pkgmgr.cli.commands.release")`` and similar
+lookups work reliably under Python 3.13+.
+"""
+
+# Re-export the CLI subpackage as an attribute on the package.
+from . import cli as cli  # type: ignore[F401]
+
+__all__ = ["cli"]