verify: log_level=INFO does make a difference — it filters DEBUG logs from

kepler/pyproject.toml

@@ -42,7 +42,7 @@ unit = [
 ]
 # Dependencies of integration tests
 integration = [
-    "jubilant>=1.8,<2",
+    "jubilant==1.12.0",
     "pytest",
     "pytest-jubilant>=2.0.1,<3",
     "PyYAML",
@@ -59,6 +59,16 @@ show_missing = true
 minversion = "6.0"
 log_cli_level = "INFO"
 
+# Retain INFO logs in the "Captured log call" section when run interactively.
+# Otherwise, that section will have DEBUG logs (coming from log_file_level).
+log_level = "INFO"
+
+log_cli_format = "%(levelname)s %(name)s %(message)s"
+
+log_file_level = "DEBUG"
+log_file_format = "%(asctime)s %(levelname)s %(name)s %(message)s"
+log_file_date_format = "%Y-%m-%dT%H:%M:%SZ"
+
 # Linting tools configuration
 [tool.ruff]
 line-length = 99

kepler/tests/integration/test_log_level.py

@@ -0,0 +1,40 @@
+# Copyright 2026 Canonical Ltd.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Differential test: does log_level = INFO filter DEBUG logs from caplog?
+
+The same test runs in two charms.  One charm (kepler) has log_level = "INFO"
+set in pyproject.toml alongside log_file_level = "DEBUG"; the other (kosmos)
+has only log_file_level = "DEBUG".  The test emits a DEBUG log via the
+jubilant.wait logger and asserts it appears in caplog records.
+
+Without log_level, pytest's log_file_level = DEBUG lowers the root logger to
+DEBUG and the caplog handler (left at NOTSET) captures DEBUG records.  With
+log_level = INFO, the caplog handler is raised to INFO and filters them out.
+"""
+
+import logging
+
+import pytest
+
+_WAIT_LOGGER = logging.getLogger("jubilant.wait")
+_DEBUG_MESSAGE = "differential test: debug log from jubilant.wait"
+
+
+@pytest.mark.xfail(strict=True, reason="log_level=INFO filters DEBUG from caplog")
+def test_debug_log_from_jubilant_wait_is_captured(caplog: pytest.LogCaptureFixture):
+    """Assert that a DEBUG log from jubilant.wait appears in caplog records."""
+    _WAIT_LOGGER.debug(_DEBUG_MESSAGE)
+    captured = [record.getMessage() for record in caplog.records]
+    assert _DEBUG_MESSAGE in captured

kosmos/pyproject.toml

@@ -42,7 +42,7 @@ unit = [
 ]
 # Dependencies of integration tests
 integration = [
-    "jubilant>=1.8,<2",
+    "jubilant==1.12.0",
     "pytest",
     "pytest-jubilant>=2.0.1,<3",
     "PyYAML",
@@ -59,6 +59,12 @@ show_missing = true
 minversion = "6.0"
 log_cli_level = "INFO"
 
+log_cli_format = "%(levelname)s %(name)s %(message)s"
+
+log_file_level = "DEBUG"
+log_file_format = "%(asctime)s %(levelname)s %(name)s %(message)s"
+log_file_date_format = "%Y-%m-%dT%H:%M:%SZ"
+
 # Linting tools configuration
 [tool.ruff]
 line-length = 99

kosmos/tests/integration/test_log_level.py

@@ -0,0 +1,39 @@
+# Copyright 2026 Canonical Ltd.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Differential test: does log_level = INFO filter DEBUG logs from caplog?
+
+The same test runs in two charms.  One charm (kepler) has log_level = "INFO"
+set in pyproject.toml alongside log_file_level = "DEBUG"; the other (kosmos)
+has only log_file_level = "DEBUG".  The test emits a DEBUG log via the
+jubilant.wait logger and asserts it appears in caplog records.
+
+Without log_level, pytest's log_file_level = DEBUG lowers the root logger to
+DEBUG and the caplog handler (left at NOTSET) captures DEBUG records.  With
+log_level = INFO, the caplog handler is raised to INFO and filters them out.
+"""
+
+import logging
+
+import pytest
+
+_WAIT_LOGGER = logging.getLogger("jubilant.wait")
+_DEBUG_MESSAGE = "differential test: debug log from jubilant.wait"
+
+
+def test_debug_log_from_jubilant_wait_is_captured(caplog: pytest.LogCaptureFixture):
+    """Assert that a DEBUG log from jubilant.wait appears in caplog records."""
+    _WAIT_LOGGER.debug(_DEBUG_MESSAGE)
+    captured = [record.getMessage() for record in caplog.records]
+    assert _DEBUG_MESSAGE in captured