diff --git a/src/haclient/__init__.py b/src/haclient/__init__.py
index 6943747..d4b9853 100644
--- a/src/haclient/__init__.py
+++ b/src/haclient/__init__.py
@@ -12,6 +12,9 @@
 
 from __future__ import annotations
 
+from importlib.metadata import PackageNotFoundError
+from importlib.metadata import version as _pkg_version
+
 from haclient.api import HAClient
 from haclient.config import ConnectionConfig, ServicePolicy
 from haclient.core.connection import Connection
@@ -67,4 +70,7 @@
     "register_domain",
 ]
 
-__version__ = "0.2.0"
+try:
+    __version__ = _pkg_version("haclient")
+except PackageNotFoundError:  # pragma: no cover - only hit when package not installed
+    __version__ = "0.0.0+unknown"
diff --git a/tests/test_packaging.py b/tests/test_packaging.py
new file mode 100644
index 0000000..0fd888f
--- /dev/null
+++ b/tests/test_packaging.py
@@ -0,0 +1,26 @@
+"""Packaging metadata tests.
+
+Ensures the package version is single-sourced from installed metadata
+(see issue #78).
+"""
+
+from __future__ import annotations
+
+from importlib.metadata import version as pkg_version
+
+import haclient
+
+
+def test_version_matches_package_metadata() -> None:
+    """``haclient.__version__`` must match installed package metadata.
+
+    This guards against the previous drift where ``pyproject.toml`` and
+    ``haclient/__init__.py`` declared different versions.
+    """
+    assert haclient.__version__ == pkg_version("haclient")
+
+
+def test_version_is_non_empty_string() -> None:
+    """``__version__`` must be a non-empty string."""
+    assert isinstance(haclient.__version__, str)
+    assert haclient.__version__