diff --git a/pyproject.toml b/pyproject.toml
index 8786562..68d7bae 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -19,6 +19,15 @@ dependencies = [
 [project.scripts]
 utils = "utils:main"
 
+[tool.pytest.ini_options]
+# Live tests open a real GUI dialog and are intended for local manual
+# testing only; they are deselected by default (e.g. in the pipeline)
+# and run explicitly with: uv run pytest -m live
+addopts = "-m 'not live'"
+markers = [
+    "live: opens a real GUI dialog, intended for local manual testing",
+]
+
 [build-system]
 requires = ["uv_build>=0.12.20,<0.13.0"]
 build-backend = "uv_build"
diff --git a/src/utils/logging_config.py b/src/utils/logging_config.py
index 0b8a4f4..ca1c78e 100755
--- a/src/utils/logging_config.py
+++ b/src/utils/logging_config.py
@@ -27,7 +27,7 @@ class LoggingSettings(BaseSettingsConfig):
     LOG_FILE_PATH: str = "logs/monitoring_backend.log"
     LOG_BACKUP_COUNT: int = Field(default=30, ge=0)
 
-    def model_post_init(self, __context: Any) -> None:
+    def model_post_init(self, __context: Any, /) -> None:
         self.setup_logging()
 
     def setup_logging(self) -> None:
diff --git a/src/utils/misc.py b/src/utils/misc.py
index 87caca4..c40d127 100644
--- a/src/utils/misc.py
+++ b/src/utils/misc.py
@@ -1,8 +1,8 @@
-
 def readlines(path: str) -> list[str]:
     with open(path, "r") as fid:
         lines = fid.readlines()
     return lines
 
+
 def read(path: str) -> str:
     return "".join(readlines(path))
diff --git a/test/conftest.py b/test/conftest.py
new file mode 100644
index 0000000..e7b922d
--- /dev/null
+++ b/test/conftest.py
@@ -0,0 +1,31 @@
+"""Make the test suite runnable on machines without Tk system libraries.
+
+``utils.filedialogs`` imports tkinter at module level, and the CI runner
+lacks the Tk shared libraries (``import tkinter`` fails on a missing
+``libtk8.6.so``). Since pytest imports every test module at collection
+time — including the deselected ``test_filedialogs_live.py`` — a minimal
+stub is registered in ``sys.modules`` here, before any test module is
+imported, whenever tkinter is not importable.
+
+The hermetic tests in ``test_filedialogs.py`` mock every tkinter
+touchpoint anyway, so the stub is never actually used.
+"""
+
+import sys
+import types
+
+try:
+    import tkinter  # noqa: F401
+except ImportError:
+    _tk_stub = types.ModuleType("tkinter")
+    _filedialog_stub = types.ModuleType("tkinter.filedialog")
+
+    def _tk_unavailable(*args, **kwargs):
+        raise AssertionError("real tkinter was called without a display")
+
+    _tk_stub.Tk = _tk_unavailable
+    _tk_stub.filedialog = _filedialog_stub
+    _filedialog_stub.askdirectory = _tk_unavailable
+    _filedialog_stub.askopenfilename = _tk_unavailable
+    sys.modules["tkinter"] = _tk_stub
+    sys.modules["tkinter.filedialog"] = _filedialog_stub
diff --git a/test/test_filedialogs.py b/test/test_filedialogs.py
index 857d52a..6c56e78 100644
--- a/test/test_filedialogs.py
+++ b/test/test_filedialogs.py
@@ -1,35 +1,55 @@
+"""Hermetic tests for ``utils.filedialogs``.
+
+These tests never open a real dialog: every tkinter touchpoint is mocked,
+so they run headless and even on machines without Tk system libraries
+(e.g. the CI runner, where ``import tkinter`` fails on a missing
+``libtk8.6.so``). ``conftest.py`` registers a tkinter stub in that case,
+so ``utils.filedialogs`` can be imported at all.
+
+For tests that open a real dialog, see ``test_filedialogs_live.py``
+(marker ``live``, excluded from the default run).
+"""
+
 from unittest import mock
 
 from utils.filedialogs import get_dir_path_from_dialog, get_file_path_from_dialog
 
 
 def test_get_dir_path_from_dialog_returns_selected_path():
-    with mock.patch("tkinter.Tk"), mock.patch(
-        "tkinter.filedialog.askdirectory", return_value="/tmp/somewhere"
-    ) as dialog:
+    with (
+        mock.patch("tkinter.Tk"),
+        mock.patch(
+            "tkinter.filedialog.askdirectory", return_value="/tmp/somewhere"
+        ) as dialog,
+    ):
         result = get_dir_path_from_dialog(initialdir="/tmp", title="Pick")
     assert result == "/tmp/somewhere"
     dialog.assert_called_once_with(initialdir="/tmp", title="Pick")
 
 
 def test_get_dir_path_from_dialog_returns_empty_string_on_cancel():
-    with mock.patch("tkinter.Tk"), mock.patch(
-        "tkinter.filedialog.askdirectory", return_value=""
+    with (
+        mock.patch("tkinter.Tk"),
+        mock.patch("tkinter.filedialog.askdirectory", return_value=""),
     ):
         assert get_dir_path_from_dialog() == ""
 
 
 def test_get_file_path_from_dialog_returns_selected_path():
-    with mock.patch("tkinter.Tk"), mock.patch(
-        "tkinter.filedialog.askopenfilename", return_value="/tmp/file.txt"
-    ) as dialog:
+    with (
+        mock.patch("tkinter.Tk"),
+        mock.patch(
+            "tkinter.filedialog.askopenfilename", return_value="/tmp/file.txt"
+        ) as dialog,
+    ):
         result = get_file_path_from_dialog(filetypes=[("Text", "*.txt")])
     assert result == "/tmp/file.txt"
     dialog.assert_called_once_with(filetypes=[("Text", "*.txt")])
 
 
 def test_get_file_path_from_dialog_returns_empty_string_on_cancel():
-    with mock.patch("tkinter.Tk"), mock.patch(
-        "tkinter.filedialog.askopenfilename", return_value=""
+    with (
+        mock.patch("tkinter.Tk"),
+        mock.patch("tkinter.filedialog.askopenfilename", return_value=""),
     ):
         assert get_file_path_from_dialog() == ""
diff --git a/test/test_filedialogs_live.py b/test/test_filedialogs_live.py
new file mode 100644
index 0000000..86fba9b
--- /dev/null
+++ b/test/test_filedialogs_live.py
@@ -0,0 +1,30 @@
+"""Live dialog tests for ``utils.filedialogs``.
+
+These tests open a real OS dialog and require a working display.
+They are excluded from the default (and pipeline) runs by the
+``live`` marker configured in ``pyproject.toml`` and only run when
+explicitly requested, e.g.::
+
+    uv run pytest -m live
+
+Choose a path in the dialog (or cancel it) — either outcome passes,
+as long as the dialog returns consistently.
+"""
+
+import os
+
+import pytest
+
+from utils.filedialogs import get_dir_path_from_dialog, get_file_path_from_dialog
+
+
+@pytest.mark.live
+def test_get_dir_path_from_dialog_live():
+    result = get_dir_path_from_dialog(title="Test: pick a directory")
+    assert result == "" or os.path.isdir(result)
+
+
+@pytest.mark.live
+def test_get_file_path_from_dialog_live():
+    result = get_file_path_from_dialog(title="Test: pick a file")
+    assert result == "" or os.path.isfile(result)
diff --git a/test/test_logging_config.py b/test/test_logging_config.py
index b28f059..d89abfb 100755
--- a/test/test_logging_config.py
+++ b/test/test_logging_config.py
@@ -16,7 +16,7 @@ SECONDS_PER_DAY = 24 * 60 * 60
 
 
 @pytest.fixture
-def restore_root_logger() -> Generator[None, None, None]:
+def restore_root_logger() -> Generator[None]:
     root = logging.getLogger()
     old_handlers = root.handlers[:]
     old_level = root.level
@@ -45,7 +45,9 @@ def test_invalid_log_level_falls_back_to_info(restore_root_logger: None) -> None
         LoggingSettings(LOG_LEVEL="NOT_A_LEVEL", LOG_TO_FILE=False)
 
     assert logging.getLogger().level == logging.INFO
-    log_error.assert_called_once_with("Invalid log level %r; falling back to INFO.", "NOT_A_LEVEL")
+    log_error.assert_called_once_with(
+        "Invalid log level %r; falling back to INFO.", "NOT_A_LEVEL"
+    )
 
 
 def test_configures_console_handler_only(restore_root_logger: None) -> None:
@@ -66,7 +68,9 @@ def test_configures_file_handler_and_creates_parent_dir(
 
     handlers = logging.getLogger().handlers
     assert any(type(handler) is logging.StreamHandler for handler in handlers)
-    file_handlers = [handler for handler in handlers if isinstance(handler, logging.FileHandler)]
+    file_handlers = [
+        handler for handler in handlers if isinstance(handler, logging.FileHandler)
+    ]
     assert len(file_handlers) == 1
     assert log_file.parent.exists()
     assert isinstance(file_handlers[0], TimedRotatingFileHandler)
@@ -77,12 +81,16 @@ def test_configures_file_handler_and_creates_parent_dir(
     assert file_handlers[0].encoding.lower() == "utf-8"
 
 
-def test_configures_custom_log_backup_count(tmp_path: Path, restore_root_logger: None) -> None:
+def test_configures_custom_log_backup_count(
+    tmp_path: Path, restore_root_logger: None
+) -> None:
     log_file = tmp_path / "app.log"
     LoggingSettings(LOG_TO_FILE=True, LOG_FILE_PATH=str(log_file), LOG_BACKUP_COUNT=7)
 
     file_handler = next(
-        handler for handler in logging.getLogger().handlers if isinstance(handler, TimedRotatingFileHandler)
+        handler
+        for handler in logging.getLogger().handlers
+        if isinstance(handler, TimedRotatingFileHandler)
     )
 
     assert file_handler.backupCount == 7
@@ -99,7 +107,9 @@ def test_writes_records_to_console_and_file(
     logging.getLogger("test.logging_output").info("record is written")
 
     file_handler = next(
-        handler for handler in logging.getLogger().handlers if isinstance(handler, TimedRotatingFileHandler)
+        handler
+        for handler in logging.getLogger().handlers
+        if isinstance(handler, TimedRotatingFileHandler)
     )
     file_handler.flush()
 
@@ -112,7 +122,9 @@ def test_rotates_active_log_file(tmp_path: Path, restore_root_logger: None) -> N
     LoggingSettings(LOG_FILE_PATH=str(log_file))
     logger = logging.getLogger("test.logging_rotation")
     file_handler = next(
-        handler for handler in logging.getLogger().handlers if isinstance(handler, TimedRotatingFileHandler)
+        handler
+        for handler in logging.getLogger().handlers
+        if isinstance(handler, TimedRotatingFileHandler)
     )
 
     logger.info("before rollover")
@@ -137,7 +149,9 @@ def test_removes_old_rotated_files_after_backup_limit(
     LoggingSettings(LOG_FILE_PATH=str(log_file), LOG_BACKUP_COUNT=2)
     logger = logging.getLogger("test.logging_retention")
     file_handler = next(
-        handler for handler in logging.getLogger().handlers if isinstance(handler, TimedRotatingFileHandler)
+        handler
+        for handler in logging.getLogger().handlers
+        if isinstance(handler, TimedRotatingFileHandler)
     )
     base_timestamp = int(time.time())
 
@@ -146,7 +160,8 @@ def test_removes_old_rotated_files_after_backup_limit(
         file_handler.flush()
         rollover_timestamp = base_timestamp + day * SECONDS_PER_DAY
         file_handler.rolloverAt = rollover_timestamp + SECONDS_PER_DAY
-        monkeypatch.setattr(time, "time", lambda: rollover_timestamp)
+        # Bind the loop variable via a default argument to avoid late binding (B023).
+        monkeypatch.setattr(time, "time", lambda now=rollover_timestamp: now)
         file_handler.doRollover()
 
     assert len(list(tmp_path.glob("app.*.log"))) == 2
@@ -162,7 +177,9 @@ def test_setup_logging_is_idempotent(tmp_path: Path, restore_root_logger: None)
     settings = LoggingSettings(LOG_TO_FILE=True, LOG_FILE_PATH=str(log_file))
 
     first_file_handler = next(
-        handler for handler in logging.getLogger().handlers if isinstance(handler, logging.FileHandler)
+        handler
+        for handler in logging.getLogger().handlers
+        if isinstance(handler, logging.FileHandler)
     )
     first_handler_count = len(logging.getLogger().handlers)
 
diff --git a/test/test_misc.py b/test/test_misc.py
index 2968c01..f167e75 100644
--- a/test/test_misc.py
+++ b/test/test_misc.py
@@ -1,4 +1,3 @@
-
 from pathlib import Path
 
 from utils.misc import read, readlines
@@ -12,6 +11,7 @@ with a second line
 and a third line
 """
 
+
 def test_readlines_str():
     result = readlines(TEST_FILE_PATH)
     assert result
@@ -19,6 +19,7 @@ def test_readlines_str():
     assert all(isinstance(element, str) for element in result)
     assert result[1].strip() == "with a second line"
 
+
 def test_path_str():
     result = read(TEST_FILE_PATH)
     assert result