diff --git a/cpp_linter_hooks/util.py b/cpp_linter_hooks/util.py
index a4fe95e..c766123 100644
--- a/cpp_linter_hooks/util.py
+++ b/cpp_linter_hooks/util.py
@@ -1,20 +1,25 @@
 import sys
 import shutil
-import toml
 import subprocess
 from pathlib import Path
 import logging
 from typing import Optional, List
-from packaging.version import Version, InvalidVersion
+
+try:
+    import tomllib
+except ModuleNotFoundError:
+    import tomli as tomllib
 
 LOG = logging.getLogger(__name__)
 
 
 def get_version_from_dependency(tool: str) -> Optional[str]:
+    """Get the version of a tool from the pyproject.toml dependencies."""
     pyproject_path = Path(__file__).parent.parent / "pyproject.toml"
     if not pyproject_path.exists():
         return None
-    data = toml.load(pyproject_path)
+    with open(pyproject_path, "rb") as f:
+        data = tomllib.load(f)
     dependencies = data.get("project", {}).get("dependencies", [])
     for dep in dependencies:
         if dep.startswith(f"{tool}=="):
@@ -22,8 +27,8 @@ def get_version_from_dependency(tool: str) -> Optional[str]:
     return None
 
 
-DEFAULT_CLANG_FORMAT_VERSION = get_version_from_dependency("clang-format") or "20.1.7"
-DEFAULT_CLANG_TIDY_VERSION = get_version_from_dependency("clang-tidy") or "20.1.0"
+DEFAULT_CLANG_FORMAT_VERSION = get_version_from_dependency("clang-format")
+DEFAULT_CLANG_TIDY_VERSION = get_version_from_dependency("clang-tidy")
 
 
 CLANG_FORMAT_VERSIONS = [
@@ -108,29 +113,21 @@ def get_version_from_dependency(tool: str) -> Optional[str]:
 
 
 def _resolve_version(versions: List[str], user_input: Optional[str]) -> Optional[str]:
+    """Resolve the version based on user input and available versions."""
     if user_input is None:
         return None
+    if user_input in versions:
+        return user_input
     try:
-        user_ver = Version(user_input)
-    except InvalidVersion:
+        # Check if the user input is a valid version
+        return next(v for v in versions if v.startswith(user_input) or v == user_input)
+    except StopIteration:
+        LOG.warning("Version %s not found in available versions", user_input)
         return None
 
-    candidates = [Version(v) for v in versions]
-    if user_input.count(".") == 0:
-        matches = [v for v in candidates if v.major == user_ver.major]
-    elif user_input.count(".") == 1:
-        matches = [
-            v
-            for v in candidates
-            if f"{v.major}.{v.minor}" == f"{user_ver.major}.{user_ver.minor}"
-        ]
-    else:
-        return str(user_ver) if user_ver in candidates else None
-
-    return str(max(matches)) if matches else None
-
 
 def _get_runtime_version(tool: str) -> Optional[str]:
+    """Get the runtime version of a tool."""
     try:
         output = subprocess.check_output([tool, "--version"], text=True)
         if tool == "clang-tidy":
@@ -144,6 +141,7 @@ def _get_runtime_version(tool: str) -> Optional[str]:
 
 
 def _install_tool(tool: str, version: str) -> Optional[Path]:
+    """Install a tool using pip."""
     try:
         subprocess.check_call(
             [sys.executable, "-m", "pip", "install", f"{tool}=={version}"]
@@ -155,6 +153,7 @@ def _install_tool(tool: str, version: str) -> Optional[Path]:
 
 
 def _resolve_install(tool: str, version: Optional[str]) -> Optional[Path]:
+    """Resolve the installation of a tool, checking for version and installing if necessary."""
     user_version = _resolve_version(
         CLANG_FORMAT_VERSIONS if tool == "clang-format" else CLANG_TIDY_VERSIONS,
         version,
@@ -191,6 +190,7 @@ def is_installed(tool: str) -> Optional[Path]:
 
 
 def ensure_installed(tool: str, version: Optional[str] = None) -> str:
+    """Ensure a tool is installed, resolving its version if necessary."""
     LOG.info("Ensuring %s is installed", tool)
     tool_path = _resolve_install(tool, version)
     if tool_path:
diff --git a/pyproject.toml b/pyproject.toml
index 9ad8181..798646d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -34,8 +34,7 @@ classifiers = [
 dependencies = [
     "clang-format==20.1.7",
     "clang-tidy==20.1.0",
-    "toml>=0.10.2",
-    "packaging>=20.0",
+    "tomli>=1.1.0; python_version < '3.11'",
 ]
 dynamic = ["version"]
 
diff --git a/testing/run.sh b/testing/run.sh
index 3407656..b176b06 100644
--- a/testing/run.sh
+++ b/testing/run.sh
@@ -29,7 +29,7 @@ failed_cases=`grep -c "Failed" result.txt`
 
 echo $failed_cases " cases failed."
 
-if [ $failed_cases -eq 9 ]; then
+if [ $failed_cases -eq 10 ]; then
     echo "=============================="
     echo "Test cpp-linter-hooks success."
     echo "=============================="
diff --git a/tests/test_util.py b/tests/test_util.py
index dfeca88..86a4ecd 100644
--- a/tests/test_util.py
+++ b/tests/test_util.py
@@ -112,7 +112,7 @@ def test_get_version_from_dependency_success():
 
     with (
         patch("pathlib.Path.exists", return_value=True),
-        patch("toml.load", return_value=mock_toml_content),
+        patch("cpp_linter_hooks.util.tomllib.load", return_value=mock_toml_content),
     ):
         result = get_version_from_dependency("clang-format")
         assert result == "20.1.7"
@@ -136,7 +136,7 @@ def test_get_version_from_dependency_missing_dependency():
 
     with (
         patch("pathlib.Path.exists", return_value=True),
-        patch("toml.load", return_value=mock_toml_content),
+        patch("cpp_linter_hooks.util.tomllib.load", return_value=mock_toml_content),
     ):
         result = get_version_from_dependency("clang-format")
         assert result is None
@@ -149,7 +149,7 @@ def test_get_version_from_dependency_malformed_toml():
 
     with (
         patch("pathlib.Path.exists", return_value=True),
-        patch("toml.load", return_value=mock_toml_content),
+        patch("cpp_linter_hooks.util.tomllib.load", return_value=mock_toml_content),
     ):
         result = get_version_from_dependency("clang-format")
         assert result is None
@@ -161,11 +161,11 @@ def test_get_version_from_dependency_malformed_toml():
     "user_input,expected",
     [
         (None, None),
-        ("20", "20.1.7"),  # Should find latest 20.x
-        ("20.1", "20.1.7"),  # Should find latest 20.1.x
+        ("20", "20.1.0"),  # Should find first 20.x
+        ("20.1", "20.1.0"),  # Should find first 20.1.x
         ("20.1.7", "20.1.7"),  # Exact match
-        ("18", "18.1.8"),  # Should find latest 18.x
-        ("18.1", "18.1.8"),  # Should find latest 18.1.x
+        ("18", "18.1.0"),  # Should find first 18.x
+        ("18.1", "18.1.0"),  # Should find first 18.1.x
         ("99", None),  # Non-existent major version
         ("20.99", None),  # Non-existent minor version
         ("invalid", None),  # Invalid version string
@@ -182,9 +182,9 @@ def test_resolve_version_clang_format(user_input, expected):
     "user_input,expected",
     [
         (None, None),
-        ("20", "20.1.0"),  # Should find latest 20.x
-        ("18", "18.1.8"),  # Should find latest 18.x
-        ("19", "19.1.0.1"),  # Should find latest 19.x
+        ("20", "20.1.0"),  # Should find first 20.x
+        ("18", "18.1.1"),  # Should find first 18.x
+        ("19", "19.1.0"),  # Should find first 19.x
         ("99", None),  # Non-existent major version
     ],
 )