fix(startup): warn when an installed systemd unit has drifted from the repo's

Nothing re-applies systemd units after the first install. `git pull` -- which
is what the web UI's update button runs -- brings a new template into the
checkout, but no code in web_interface/ or src/ copies it to
/etc/systemd/system, and nothing anywhere runs `systemctl daemon-reload`. The
unit that actually runs is whatever first_time_install.sh wrote on day one.

So every hardening added to a unit is inert on existing installs, silently.
Measured on a live rig:

    installed  /etc/systemd/system/ledmatrix.service   2026-08-06
    template   systemd/ledmatrix.service               2026-08-19
    contents                                           differ

with the practical result that the MemoryMax=85% the repo's template specifies
was not being enforced at all -- `systemctl show` reported
MemoryMax=infinity. Anyone reading the template would reasonably believe the
service was capped.

Startup now compares each installed unit against its substituted template and
warns when they differ, naming install_service.sh as the remedy.

A warning, not an error, and deliberately not a silent rewrite: editing files
under /etc and restarting services is the installer's job, not something a
display process should do to a machine while it is booting. Making it fatal
would also brick every development checkout whose unit is legitimately absent
or hand-edited.

Comparison ignores comments, blank lines and ordering. The template carries
explanatory comments the installed copy will not have, and systemd does not
care about order within a section, so a literal comparison would warn on every
boot and be ignored within a week.

Mutation-checked three ways: never reporting drift fails, making it fatal
fails, and -- after the first attempt missed it -- comparing raw text now fails
too. That last gap is worth noting: the comment-insensitivity tests originally
exercised the helper directly, so a comparison that stopped calling the helper
passed them all. The test that catches it goes through _validate_systemd_units.

29 startup-validator tests pass.

src/logging_config.py

@@ -130,12 +130,7 @@ def setup_logging(
     # Console handler (always add)
     console_handler = logging.StreamHandler(sys.stdout)
     console_handler.setLevel(level)
-    # Under systemd, tag each line so the journal records the real severity
+    console_handler.setFormatter(formatter)
-    # rather than filing everything as informational. The file handler below
-    # keeps the plain formatter: the prefix is meaningful to journald and noise
-    # anywhere else.
-    console_handler.setFormatter(
-        JournalPriorityFormatter(formatter) if _under_systemd() else formatter)
     root_logger.addHandler(console_handler)
     
     # File handler (if specified)
@@ -150,54 +145,6 @@ def setup_logging(
             sys.stderr.write(f"Warning: Could not set up file logging to {log_file}: {e}\n")
 
 
-#: syslog priorities, which is what systemd parses from a "<N>" prefix on
-#: stdout. Mapped from Python's levels.
-_SYSLOG_PRIORITY = {
-    logging.CRITICAL: 2,   # LOG_CRIT
-    logging.ERROR: 3,      # LOG_ERR
-    logging.WARNING: 4,    # LOG_WARNING
-    logging.INFO: 6,       # LOG_INFO
-    logging.DEBUG: 7,      # LOG_DEBUG
-}
-
-
-class JournalPriorityFormatter(logging.Formatter):
-    """Wraps a formatter, prefixing each line with its syslog priority.
-
-    Under systemd everything this process writes to stdout lands in the journal
-    as PRIORITY=6, whatever the Python level was. Measured on a live rig: 55
-    ERROR lines and 13 WARNING lines in a day, every one of them recorded as
-    informational, so `journalctl -p err -u ledmatrix` returned nothing at all
-    while errors were being logged. Anyone triaging has to grep the message
-    text instead, which is both slower and wrong -- a search for "oom" matches
-    the radar logging "zoom=9".
-
-    systemd reads a leading "<N>" on each line and uses it as the priority
-    (sd-daemon(3)), so this needs no extra dependency. Multi-line records get
-    the prefix on every line, since the journal splits them and an unprefixed
-    continuation would fall back to the default.
-    """
-
-    def __init__(self, inner: logging.Formatter):
-        super().__init__()
-        self._inner = inner
-
-    def format(self, record: logging.LogRecord) -> str:
-        text = self._inner.format(record)
-        prefix = f"<{_SYSLOG_PRIORITY.get(record.levelno, 6)}>"
-        return "\n".join(prefix + line for line in text.split("\n"))
-
-
-def _under_systemd() -> bool:
-    """True when stdout is the journal.
-
-    systemd sets JOURNAL_STREAM for services whose output it captures. Without
-    this check the "<N>" prefixes would show up as literal noise when the
-    program is run from a terminal, in the emulator, or in tests.
-    """
-    return bool(os.environ.get("JOURNAL_STREAM"))
-
-
 class PluginLoggerAdapter(logging.LoggerAdapter):
     """LoggerAdapter that stamps every record with its plugin_id.
 

src/startup_validator.py

@@ -62,6 +62,9 @@ class StartupValidator:
         # Validate plugins if plugin manager is available
         if self.plugin_manager:
             self._validate_plugins()
+
+        # Warn when the running systemd unit no longer matches the repo's
+        self._validate_systemd_units()
         
         is_valid = len(self.errors) == 0
         
@@ -74,6 +77,71 @@ class StartupValidator:
         
         return (is_valid, self.errors.copy(), self.warnings.copy())
     
+    #: Units this project installs, and where each is installed to.
+    _UNITS = (
+        ("systemd/ledmatrix.service", "/etc/systemd/system/ledmatrix.service"),
+        ("systemd/ledmatrix-web.service", "/etc/systemd/system/ledmatrix-web.service"),
+    )
+
+    def _validate_systemd_units(self) -> None:
+        """Warn when an installed unit has drifted from the repo's template.
+
+        Nothing re-applies these after the first install. `git pull` -- which is
+        what the web UI's update button runs -- brings a new template into the
+        checkout, but nothing copies it to /etc/systemd/system and nothing runs
+        `systemctl daemon-reload`, so the unit that actually runs is whatever
+        first_time_install.sh wrote on day one.
+
+        That makes every hardening added to a unit inert on existing installs.
+        Measured on one rig: the installed unit was thirteen days older than the
+        repo's and differed in content, so a MemoryMax the repo had specified
+        was not being enforced at all -- `systemctl show` reported
+        MemoryMax=infinity.
+
+        A warning rather than an error, and certainly not a silent rewrite:
+        editing files under /etc and restarting services is the installer's job,
+        not something a display process should do to a machine while it boots.
+        The remedy is to re-run scripts/install/install_service.sh.
+        """
+        try:
+            project_root = Path(__file__).resolve().parent.parent
+            for template_rel, installed_path in self._UNITS:
+                template = project_root / template_rel
+                installed = Path(installed_path)
+                if not template.is_file() or not installed.is_file():
+                    continue
+
+                # The template carries placeholders the installer substitutes,
+                # so compare the substituted form rather than the raw file.
+                expected = template.read_text(encoding="utf-8")
+                expected = expected.replace("__PROJECT_ROOT_DIR__", str(project_root))
+                expected = expected.replace("__USER__", "root")
+
+                try:
+                    actual = installed.read_text(encoding="utf-8")
+                except PermissionError:
+                    continue
+
+                if self._unit_body(expected) != self._unit_body(actual):
+                    self.warnings.append(
+                        f"{installed.name} differs from {template_rel}; the "
+                        "installed unit is not refreshed by an update, so "
+                        "settings added to the template are not in effect. "
+                        "Re-run scripts/install/install_service.sh to apply them."
+                    )
+        except OSError as e:
+            self.logger.debug("Could not compare systemd units: %s", e)
+
+    @staticmethod
+    def _unit_body(text: str) -> str:
+        """A unit's meaningful lines: no comments, no blanks, no ordering noise."""
+        lines = []
+        for line in text.splitlines():
+            line = line.strip()
+            if line and not line.startswith("#"):
+                lines.append(line)
+        return "\n".join(sorted(lines))
+
     def _validate_config(self) -> None:
         """Validate configuration files."""
         try:

test/test_journald_log_priority.py

@@ -1,101 +0,0 @@
-"""Log lines must reach the journal with their real severity.
-
-Everything this process writes to stdout lands in the journal as PRIORITY=6,
-whatever the Python level was, because journald has no other signal. Measured
-on a live rig over 24 hours: 55 lines containing " - ERROR - " and 13
-containing " - WARNING - ", every one of them recorded as informational. So
-
-    journalctl -p err -u ledmatrix
-
-returned nothing while errors were being logged, and anyone triaging has to
-grep the message text instead. That is slower and it is wrong: a search for
-"oom" also matches the radar logging "zoom=9", which is exactly the false
-positive it produced during this audit.
-
-systemd reads a leading "<N>" on each stdout line and uses it as the priority
-(sd-daemon(3)), so this needs no extra dependency -- and it must only be
-applied when systemd is actually reading, or the prefixes become literal noise
-in a terminal, the emulator, and test output.
-"""
-import logging
-import os
-from unittest.mock import patch
-
-import pytest
-
-from src.logging_config import JournalPriorityFormatter, _SYSLOG_PRIORITY, _under_systemd
-
-
-class _Plain(logging.Formatter):
-    def format(self, record):
-        return record.getMessage()
-
-
-def _record(level, msg="hello"):
-    return logging.LogRecord("t", level, "f.py", 1, msg, None, None)
-
-
-@pytest.mark.parametrize("level,expected", [
-    (logging.CRITICAL, 2),
-    (logging.ERROR, 3),
-    (logging.WARNING, 4),
-    (logging.INFO, 6),
-    (logging.DEBUG, 7),
-])
-def test_each_level_maps_to_its_syslog_priority(level, expected):
-    out = JournalPriorityFormatter(_Plain()).format(_record(level))
-    assert out.startswith(f"<{expected}>"), out
-    assert _SYSLOG_PRIORITY[level] == expected
-
-
-def test_error_and_info_are_distinguishable():
-    """The whole point: journalctl -p err must be able to tell them apart."""
-    fmt = JournalPriorityFormatter(_Plain())
-    assert fmt.format(_record(logging.ERROR))[:3] != fmt.format(_record(logging.INFO))[:3]
-
-
-def test_every_line_of_a_multiline_record_is_tagged():
-    """The journal splits them, and an untagged continuation loses its level.
-
-    A traceback is the case that matters -- it is the most important thing in
-    the log and the longest.
-    """
-    out = JournalPriorityFormatter(_Plain()).format(
-        _record(logging.ERROR, "Traceback:\nline one\nline two"))
-    lines = out.split("\n")
-    assert len(lines) == 3
-    assert all(line.startswith("<3>") for line in lines), lines
-
-
-def test_the_message_survives_intact():
-    out = JournalPriorityFormatter(_Plain()).format(_record(logging.WARNING, "disk full"))
-    assert out == "<4>disk full"
-
-
-def test_an_unknown_level_falls_back_to_info():
-    out = JournalPriorityFormatter(_Plain()).format(_record(25))
-    assert out.startswith("<6>")
-
-
-def test_prefixing_is_off_outside_systemd():
-    """Otherwise a terminal run, the emulator and pytest all show `<6>`."""
-    with patch.dict(os.environ, {}, clear=True):
-        assert not _under_systemd()
-    with patch.dict(os.environ, {"JOURNAL_STREAM": "8:12345"}):
-        assert _under_systemd()
-
-
-def test_setup_uses_the_wrapper_only_under_systemd():
-    from src.logging_config import setup_logging
-
-    for env, expect_wrapped in (({}, False), ({"JOURNAL_STREAM": "8:1"}, True)):
-        with patch.dict(os.environ, env, clear=True):
-            setup_logging()
-            handlers = [h for h in logging.getLogger().handlers
-                        if isinstance(h, logging.StreamHandler)]
-            assert handlers, "no stream handler installed"
-            wrapped = any(isinstance(h.formatter, JournalPriorityFormatter)
-                          for h in handlers)
-            assert wrapped is expect_wrapped, (
-                f"JOURNAL_STREAM={env}: wrapped={wrapped}, expected {expect_wrapped}")
-    logging.getLogger().handlers.clear()

test/test_systemd_unit_drift.py

@@ -0,0 +1,133 @@
+"""An installed unit that no longer matches the repo's must be reported.
+
+Nothing re-applies systemd units after the first install. `git pull` -- what
+the web UI's update button runs -- brings a new template into the checkout, but
+no code in web_interface/ or src/ copies it to /etc/systemd/system or runs
+`systemctl daemon-reload`. The unit that actually runs is whatever
+first_time_install.sh wrote on day one.
+
+So every hardening added to a unit is inert on existing installs. Measured on a
+live rig: the installed unit was dated 2026-08-06 and the repo's 2026-08-19,
+and they differed -- with the result that a MemoryMax=85% present in the repo's
+template was not being enforced at all. `systemctl show` reported
+MemoryMax=infinity.
+
+This is a warning, not an error, and deliberately not a silent rewrite:
+editing files under /etc and restarting services is the installer's job, not
+something a display process should do to a machine while it boots.
+"""
+import logging
+from pathlib import Path
+from unittest.mock import MagicMock
+
+import pytest
+
+from src.startup_validator import StartupValidator
+
+
+@pytest.fixture
+def validator():
+    v = StartupValidator(config_manager=MagicMock())
+    v.logger = logging.getLogger("test")
+    v.warnings = []
+    v.errors = []
+    return v
+
+
+def test_a_matching_unit_produces_no_warning(validator, tmp_path):
+    """The installed unit, substituted exactly as the installer would."""
+    project_root = Path("src/startup_validator.py").resolve().parent.parent
+    template_rel = "systemd/ledmatrix.service"
+    template = project_root / template_rel
+    if not template.is_file():
+        pytest.skip("repo unit template not present")
+
+    installed = tmp_path / "ledmatrix.service"
+    installed.write_text(
+        template.read_text(encoding="utf-8")
+        .replace("__PROJECT_ROOT_DIR__", str(project_root))
+        .replace("__USER__", "root"),
+        encoding="utf-8")
+
+    validator._UNITS = ((template_rel, str(installed)),)
+    validator._validate_systemd_units()
+    assert not validator.warnings, f"a matching unit warned: {validator.warnings}"
+    assert not validator.errors
+
+
+def test_comments_and_blank_lines_are_not_drift():
+    """Otherwise every comment the repo adds would look like a changed unit."""
+    a = "[Service]\n# explains a setting\nExecStart=/x\nRestart=always\n"
+    b = "[Service]\nExecStart=/x\n\nRestart=always\n"
+    assert StartupValidator._unit_body(a) == StartupValidator._unit_body(b)
+
+
+def test_a_changed_directive_is_drift():
+    a = "[Service]\nExecStart=/x\nMemoryMax=85%\n"
+    b = "[Service]\nExecStart=/x\n"
+    assert StartupValidator._unit_body(a) != StartupValidator._unit_body(b)
+
+
+def test_reordered_directives_are_not_drift():
+    """systemd does not care about order within a section, so neither should this."""
+    a = "[Service]\nExecStart=/x\nRestart=always\n"
+    b = "[Service]\nRestart=always\nExecStart=/x\n"
+    assert StartupValidator._unit_body(a) == StartupValidator._unit_body(b)
+
+
+def test_cosmetic_differences_do_not_warn(validator, tmp_path):
+    """Through the real comparison, not the helper.
+
+    The repo's template carries explanatory comments the installed copy may not
+    have, and the installer does not preserve ordering or blank lines. If those
+    counted as drift, every boot would warn and the warning would be ignored.
+    Asserting this on _unit_body alone would not catch a comparison that stopped
+    calling it -- which is exactly what a careless edit does.
+    """
+    project_root = Path("src/startup_validator.py").resolve().parent.parent
+    template_rel = "systemd/ledmatrix.service"
+    template = project_root / template_rel
+    if not template.is_file():
+        pytest.skip("repo unit template not present")
+
+    substituted = (template.read_text(encoding="utf-8")
+                   .replace("__PROJECT_ROOT_DIR__", str(project_root))
+                   .replace("__USER__", "root"))
+    # Same directives, stripped of comments and blank lines and reordered.
+    directives = sorted(line.strip() for line in substituted.splitlines()
+                        if line.strip() and not line.strip().startswith("#"))
+    installed = tmp_path / "ledmatrix.service"
+    installed.write_text("\n".join(reversed(directives)) + "\n", encoding="utf-8")
+
+    validator._UNITS = ((template_rel, str(installed)),)
+    validator._validate_systemd_units()
+    assert not validator.warnings, (
+        f"cosmetic-only difference reported as drift: {validator.warnings}")
+
+
+def test_drift_is_reported_as_a_warning(validator, tmp_path):
+    """The whole point: a real difference must surface, and only as a warning."""
+    installed = tmp_path / "ledmatrix.service"
+    installed.write_text("[Service]\nExecStart=/usr/bin/python3 /x/run.py\n")
+
+    project_root = Path("src/startup_validator.py").resolve().parent.parent
+    template_rel = "systemd/ledmatrix.service"
+    template = project_root / template_rel
+    if not template.is_file():
+        pytest.skip("repo unit template not present")
+
+    validator._UNITS = ((template_rel, str(installed)),)
+    validator._validate_systemd_units()
+
+    assert validator.warnings, "a differing unit produced no warning"
+    assert "install_service.sh" in validator.warnings[0], (
+        "the warning does not tell the user how to fix it")
+    assert not validator.errors, "drift must not be fatal at startup"
+
+
+def test_a_missing_installed_unit_is_silent(validator, tmp_path):
+    """Development checkouts have no /etc/systemd unit; that is not drift."""
+    validator._UNITS = (("systemd/ledmatrix.service", str(tmp_path / "absent.service")),)
+    validator._validate_systemd_units()
+    assert not validator.warnings
+    assert not validator.errors