feat(scripts): add post-rebuild-check for the gaps a reinstall leaves

A rebuilt machine looks finished and isn't. Five gaps surfaced on velox within two days of its reinstall. Three looked fine on inspection: a stowed unit file, an enabled-looking timer, a present git clone. The script runs those five checks and prints a line for each whether or not it finds anything.

Every probe fails closed. A check that cannot run reports a finding rather than a pass, which matters more here than anywhere: a silent no-op in the checker is the exact failure it exists to catch. `systemctl --user` exits 1 with empty output when there is no user bus, so reading that as "no failed units" would call a machine healthy at the moment nothing was checked. Calls are bounded for the same reason. A check that hangs reports nothing at all, and the machine most in need of checking is the one it hangs on.

I suppressed three classes of finding, each because the live run produced them and reality disagreed. A timer-activated service is supposed to sit linked and not enabled. One expected tooling file is seed-only, so most projects legitimately never have one. Vendored package trees ship their own example files. Left in, those were 19 of the first run's 27 findings, and a check nobody reads is a check that isn't run.

The post-install checklist points at it, and 58 tests cover it.

1 files changed, 684 insertions, 0 deletions

diff --git a/tests/post-rebuild-check/test_post_rebuild_check.py b/tests/post-rebuild-check/test_post_rebuild_check.py
new file mode 100644
index 0000000..4894451
--- /dev/null
+++ b/tests/post-rebuild-check/test_post_rebuild_check.py
@@ -0,0 +1,684 @@
+"""Tests for the post-rebuild-check script.
+
+A rebuilt machine looks finished and isn't: on velox 2026-08-13 five gaps
+surfaced within two days, three of which LOOKED fine (a stowed unit file, an
+enabled timer, a present git clone). The script runs the five checks from the
+post-rebuild task and turns each silent no-op into a visible line:
+
+  1. failed systemd units (user and system scope)
+  2. user unit files present but not enabled (linked-and-inert timers)
+  3. tracked *.example files whose real sibling is missing
+  4. gitignore-mode projects missing tooling paths their own .gitignore names
+  5. signal-cli holds no registered account
+
+Exit 0 with every check clean, 1 when any check found something.
+
+Test seams (env vars the production script honors; for each, SET-BUT-EMPTY
+means "the real probe ran and found nothing", UNSET means "run the real
+probe"):
+  PRC_FAILED_UNITS      newline list of "scope:unit" (scope user|system)
+  PRC_UNIT_STATES       newline list of "unit-file state" for the user unit dir
+  PRC_LOCAL_SCAN_ROOTS  newline-separated roots to scan for *.example orphans
+  PRC_PROJECT_ROOTS     newline-separated project dirs for the tooling check
+  PRC_SIGNAL_ACCOUNTS   signal-cli listAccounts output ("" = no accounts);
+                        the special value MISSING means the binary is absent
+
+Run from repo root:
+    python3 -m unittest tests.post-rebuild-check.test_post_rebuild_check
+"""
+
+import os
+import subprocess
+import tempfile
+import time
+import unittest
+
+
+REPO_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", ".."))
+CHECK = os.path.join(REPO_ROOT, "scripts", "post-rebuild-check")
+
+
+def run_check(failed_units="", unit_states="", local_roots="",
+              project_roots="", signal_accounts="+15045551234"):
+    """Run the script with every probe stubbed; defaults are all-clean.
+
+    Roots are newline-separated. Empty means "the seam is set and names no
+    roots" -- the script tests with ${VAR+set}, so an empty value is still
+    set and never falls through to the real probe.
+    """
+    env = dict(os.environ)
+    env["PRC_FAILED_UNITS"] = failed_units
+    env["PRC_UNIT_STATES"] = unit_states
+    env["PRC_LOCAL_SCAN_ROOTS"] = local_roots
+    env["PRC_PROJECT_ROOTS"] = project_roots
+    env["PRC_SIGNAL_ACCOUNTS"] = signal_accounts
+    return subprocess.run(
+        ["sh", CHECK], capture_output=True, text=True, timeout=30, env=env,
+    )
+
+
+class AllClean(unittest.TestCase):
+    # --- Normal cases ---------------------------------------------------
+
+    def test_all_clean_exits_zero(self):
+        r = run_check()
+        self.assertEqual(r.returncode, 0, r.stdout + r.stderr)
+
+    def test_all_clean_prints_one_line_per_check(self):
+        # The visible line per check is the point of the script: a silent
+        # no-op is exactly what let the velox gaps sit unseen for two days.
+        r = run_check()
+        for label in ("failed units", "unit files", "local files",
+                      "project tooling", "signal"):
+            self.assertIn(label, r.stdout.lower())
+
+    def test_all_clean_summary_says_clean(self):
+        r = run_check()
+        self.assertIn("all checks clean", r.stdout.lower())
+
+    def test_all_clean_no_deviation_lines(self):
+        r = run_check()
+        self.assertNotIn("DEVIATION", r.stdout)
+
+
+class FailedUnits(unittest.TestCase):
+    # --- Normal cases ---------------------------------------------------
+
+    def test_failed_user_unit_flags(self):
+        r = run_check(failed_units="user:calendar-sync.service")
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("calendar-sync.service", r.stdout)
+        self.assertIn("DEVIATION", r.stdout)
+
+    def test_failed_system_unit_flags(self):
+        r = run_check(failed_units="system:tlp.service")
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("tlp.service", r.stdout)
+
+    def test_multiple_failed_units_each_reported(self):
+        r = run_check(
+            failed_units="user:calendar-sync.service\nsystem:tlp.service")
+        self.assertIn("calendar-sync.service", r.stdout)
+        self.assertIn("tlp.service", r.stdout)
+
+    # --- Boundary cases -------------------------------------------------
+
+    def test_blank_lines_in_seam_ignored(self):
+        r = run_check(failed_units="\n\nuser:a.service\n\n")
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("a.service", r.stdout)
+
+
+class UnitFilesNotEnabled(unittest.TestCase):
+    # --- Normal cases ---------------------------------------------------
+
+    def test_disabled_timer_flags(self):
+        r = run_check(unit_states="roam-sync.timer disabled")
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("roam-sync.timer", r.stdout)
+
+    def test_linked_timer_flags(self):
+        # The exact velox case: a unit symlinked into the user dir by hand,
+        # never enabled — present, inert, and it LOOKS installed.
+        r = run_check(unit_states="signal-receive.timer linked")
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("signal-receive.timer", r.stdout)
+
+    def test_enabled_timer_passes(self):
+        r = run_check(unit_states="roam-sync.timer enabled")
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    def test_static_service_passes(self):
+        # A service with no [Install] section is pulled in by its timer;
+        # "static" is its healthy state, not a gap.
+        r = run_check(unit_states="roam-sync.service static")
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    def test_disabled_service_flags(self):
+        r = run_check(unit_states="obsbot-wb-guard.service disabled")
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("obsbot-wb-guard.service", r.stdout)
+
+    # --- Boundary cases -------------------------------------------------
+
+    def test_mixed_states_only_inert_reported(self):
+        r = run_check(unit_states="a.timer enabled\nb.timer disabled\n"
+                                  "c.service static\nd.service linked")
+        self.assertEqual(r.returncode, 1)
+        self.assertNotIn("a.timer", r.stdout)
+        self.assertIn("b.timer", r.stdout)
+        self.assertNotIn("c.service", r.stdout)
+        self.assertIn("d.service", r.stdout)
+
+    def test_masked_unit_passes(self):
+        # Masking is a deliberate act (ppd on laptops), not rebuild rot.
+        r = run_check(unit_states="power-profiles-daemon.service masked")
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    def test_service_whose_timer_is_enabled_passes(self):
+        # A timer-activated service is SUPPOSED to sit linked-not-enabled:
+        # the timer owns activation, and enabling the service too would run
+        # it at boot as well. Six of velox's units are this shape, and
+        # flagging them is the noise that gets a check ignored.
+        r = run_check(unit_states="roam-sync.service linked\n"
+                                  "roam-sync.timer enabled")
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    def test_service_whose_timer_is_inert_flags_the_timer_only(self):
+        # When the timer itself never got enabled, the timer is the finding.
+        # Naming the service too would double-count one gap.
+        r = run_check(unit_states="obs-record-watchdog.service linked\n"
+                                  "obs-record-watchdog.timer linked")
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("obs-record-watchdog.timer", r.stdout)
+        self.assertNotIn("obs-record-watchdog.service", r.stdout)
+
+    def test_service_without_a_timer_still_flags(self):
+        # Nothing else can start it, so linked-not-enabled means dead.
+        r = run_check(unit_states="emacs.service linked")
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("emacs.service", r.stdout)
+
+    def test_a_runtime_enabled_timer_suppresses_its_service(self):
+        # enabled-runtime is a live activation path (enabled until reboot)
+        # and generated means something produced and installed it, so the
+        # service beneath either is being started and is not a finding.
+        for state in ("enabled-runtime", "generated"):
+            with self.subTest(timer=state):
+                r = run_check(unit_states=f"foo.service linked\n"
+                                          f"foo.timer {state}")
+                self.assertEqual(r.returncode, 0,
+                                 f"a {state} timer failed to suppress")
+
+    def test_an_indirect_timer_does_not_suppress_its_service(self):
+        # "indirect" means the unit file itself is NOT enabled -- only that
+        # some Also= relative might be. Under this script's own fail-closed
+        # rule the uncertain case flags, so suppressing here would be the
+        # masked blind spot again in a narrower form.
+        r = run_check(unit_states="foo.service linked\nfoo.timer indirect")
+        self.assertEqual(r.returncode, 1,
+                         "an indirect timer suppressed a service nothing starts")
+        self.assertIn("foo.service", r.stdout)
+
+    def test_a_service_whose_timer_cannot_start_it_still_flags(self):
+        # Suppression is earned by a timer that can actually run the service.
+        # A masked, static, or absent timer starts nothing, so the service is
+        # as dead as one with no timer at all -- and suppressing on the mere
+        # presence of a timer line hides exactly that.
+        for state in ("masked", "static", "not-found"):
+            with self.subTest(timer=state):
+                r = run_check(unit_states=f"foo.service linked\n"
+                                          f"foo.timer {state}")
+                self.assertEqual(r.returncode, 1,
+                                 f"a {state} timer suppressed a dead service")
+                self.assertIn("foo.service", r.stdout)
+
+
+class LocalExampleOrphans(unittest.TestCase):
+    # --- Normal cases ---------------------------------------------------
+
+    def test_example_without_sibling_flags(self):
+        with tempfile.TemporaryDirectory() as root:
+            open(os.path.join(root, "auth.local.el.example"), "w").close()
+            r = run_check(local_roots=root)
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("auth.local.el.example", r.stdout)
+
+    def test_a_real_file_that_is_a_dangling_symlink_still_flags(self):
+        # A sibling that exists only as a broken link is not a config the
+        # machine can read, so it is the same gap as an absent one.
+        with tempfile.TemporaryDirectory() as root:
+            open(os.path.join(root, "auth.local.el.example"), "w").close()
+            os.symlink("/nonexistent/stow/target",
+                       os.path.join(root, "auth.local.el"))
+            r = run_check(local_roots=root)
+        self.assertEqual(r.returncode, 1,
+                         "a dangling sibling counted as present")
+        self.assertIn("auth.local.el.example", r.stdout)
+
+    def test_example_with_sibling_passes(self):
+        with tempfile.TemporaryDirectory() as root:
+            open(os.path.join(root, "auth.local.el.example"), "w").close()
+            open(os.path.join(root, "auth.local.el"), "w").close()
+            r = run_check(local_roots=root)
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    def test_nested_example_found(self):
+        with tempfile.TemporaryDirectory() as root:
+            sub = os.path.join(root, "modules")
+            os.makedirs(sub)
+            open(os.path.join(sub, "mail.local.el.example"), "w").close()
+            r = run_check(local_roots=root)
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("mail.local.el.example", r.stdout)
+
+    # --- Boundary cases -------------------------------------------------
+
+    def test_two_roots_both_scanned(self):
+        with tempfile.TemporaryDirectory() as a, \
+             tempfile.TemporaryDirectory() as b:
+            open(os.path.join(a, "one.example"), "w").close()
+            open(os.path.join(b, "two.example"), "w").close()
+            r = run_check(local_roots=a + "\n" + b)
+        self.assertIn("one.example", r.stdout)
+        self.assertIn("two.example", r.stdout)
+
+    def test_vendored_package_dirs_not_scanned(self):
+        # elpa/ and friends hold third-party packages that ship their own
+        # .example docs. Those are the package's business, not this machine's,
+        # and one of them (dirvish's) was the only finding check 3 produced on
+        # velox — a standing false positive in front of any real one.
+        with tempfile.TemporaryDirectory() as root:
+            for vendor in ("elpa", "node_modules", ".venv", "straight"):
+                d = os.path.join(root, vendor, "pkg-1.0", "docs")
+                os.makedirs(d)
+                open(os.path.join(d, "config.example"), "w").close()
+            r = run_check(local_roots=root)
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    def test_an_unreadable_vendored_dir_is_not_a_finding(self):
+        # The vendored trees are excluded by design, so failing to descend
+        # into one is not a gap in what this check covers. Filtering find's
+        # output without pruning its descent turns a package directory
+        # nobody wanted read into a standing "could not fully scan".
+        with tempfile.TemporaryDirectory() as root:
+            locked = os.path.join(root, "elpa", "pkg-1.0")
+            os.makedirs(locked)
+            os.chmod(locked, 0o000)
+            try:
+                r = run_check(local_roots=root)
+            finally:
+                os.chmod(locked, 0o755)
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    def test_git_dir_not_scanned(self):
+        # .git holds hooks' sample files; those are git's, not the tree's.
+        with tempfile.TemporaryDirectory() as root:
+            g = os.path.join(root, ".git", "hooks")
+            os.makedirs(g)
+            open(os.path.join(g, "pre-commit.example"), "w").close()
+            r = run_check(local_roots=root)
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    # --- Error cases ----------------------------------------------------
+
+    def test_an_unreadable_subdirectory_is_a_finding_not_a_pass(self):
+        # find exits non-zero when it cannot descend somewhere, and prints
+        # what it did reach. Discarding that status hides every orphan under
+        # the unreadable directory behind a clean "ok" -- the same defect
+        # class as a probe that cannot run reading as a pass.
+        with tempfile.TemporaryDirectory() as root:
+            locked = os.path.join(root, "locked")
+            os.makedirs(locked)
+            open(os.path.join(locked, "auth.local.el.example"), "w").close()
+            os.chmod(locked, 0o000)
+            try:
+                r = run_check(local_roots=root)
+            finally:
+                os.chmod(locked, 0o755)
+        self.assertEqual(r.returncode, 1,
+                         "an unreadable directory read as nothing to check")
+        self.assertIn("could not", r.stdout.lower())
+
+    def test_missing_root_is_its_own_finding(self):
+        # A scan root that's gone is a rebuild gap too, not a pass.
+        r = run_check(local_roots="/nonexistent/scan-root")
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("/nonexistent/scan-root", r.stdout)
+
+    def test_a_path_with_spaces_is_one_root_not_three(self):
+        # Roots arrive newline-separated for this reason: splitting on spaces
+        # turns one real directory into several imaginary missing ones.
+        with tempfile.TemporaryDirectory() as base:
+            root = os.path.join(base, "a dir with spaces")
+            os.makedirs(root)
+            open(os.path.join(root, "orphan.example"), "w").close()
+            r = run_check(local_roots=root)
+        self.assertEqual(r.stdout.count("DEVIATION"), 1, r.stdout)
+        self.assertIn("orphan.example", r.stdout)
+
+
+class ProjectTooling(unittest.TestCase):
+    def project(self, root, gitignore_lines, present=()):
+        os.makedirs(os.path.join(root, ".git"))
+        with open(os.path.join(root, ".gitignore"), "w") as f:
+            f.write("\n".join(gitignore_lines) + "\n")
+        for p in present:
+            path = os.path.join(root, p)
+            if p.endswith("/"):
+                os.makedirs(path, exist_ok=True)
+            else:
+                open(path, "w").close()
+
+    # --- Normal cases ---------------------------------------------------
+
+    def test_ignored_but_absent_tooling_flags(self):
+        with tempfile.TemporaryDirectory() as root:
+            self.project(root, [".ai/", ".claude/", "todo.org"])
+            r = run_check(project_roots=root)
+        self.assertEqual(r.returncode, 1)
+        for missing in (".ai", ".claude", "todo.org"):
+            self.assertIn(missing, r.stdout)
+
+    def test_ignored_and_present_tooling_passes(self):
+        with tempfile.TemporaryDirectory() as root:
+            self.project(root, [".ai/", "CLAUDE.md"],
+                         present=(".ai/", "CLAUDE.md"))
+            r = run_check(project_roots=root)
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    def test_claude_md_absence_never_flags(self):
+        # CLAUDE.md is seed-only: install-lang writes it once and the project
+        # owns it afterward, so most projects legitimately never have one.
+        # Ratio shows the identical absences in the identical projects, which
+        # is what proves it is the steady state and not reinstall drift.
+        with tempfile.TemporaryDirectory() as root:
+            self.project(root, [".ai/", "CLAUDE.md"], present=(".ai/",))
+            r = run_check(project_roots=root)
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    def test_missing_ai_dir_still_flags(self):
+        # The one that carries real working state — 374 files in .emacs.d's
+        # case — and that nothing restores: not git, not stow, not bootstrap.
+        with tempfile.TemporaryDirectory() as root:
+            self.project(root, [".ai/", "CLAUDE.md"])
+            r = run_check(project_roots=root)
+        self.assertEqual(r.returncode, 1)
+        self.assertIn(".ai", r.stdout)
+        self.assertNotIn("CLAUDE.md", r.stdout)
+
+    def test_unignored_tooling_never_expected(self):
+        # A project that never gitignored todo.org never had one to lose;
+        # the project's own .gitignore is the record of what it should hold.
+        with tempfile.TemporaryDirectory() as root:
+            self.project(root, [".ai/"], present=(".ai/",))
+            r = run_check(project_roots=root)
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    # --- Boundary cases -------------------------------------------------
+
+    def test_anchored_ignore_style_recognized(self):
+        # Both /.ai/ (anchored) and .ai/ (unanchored) styles exist across
+        # the fleet; the sweep-gitignore audit hit exactly this split.
+        with tempfile.TemporaryDirectory() as root:
+            self.project(root, ["/.ai/", "/CLAUDE.md"])
+            r = run_check(project_roots=root)
+        self.assertEqual(r.returncode, 1)
+        self.assertIn(".ai", r.stdout)
+
+    def test_a_worktree_or_submodule_is_still_a_project(self):
+        # In a worktree or submodule, .git is a file pointing at the real
+        # gitdir rather than a directory, so a -d test skips the project
+        # silently.
+        with tempfile.TemporaryDirectory() as root:
+            with open(os.path.join(root, ".git"), "w") as f:
+                f.write("gitdir: /somewhere/else\n")
+            with open(os.path.join(root, ".gitignore"), "w") as f:
+                f.write(".ai/\n")
+            r = run_check(project_roots=root)
+        self.assertEqual(r.returncode, 1)
+        self.assertIn(".ai", r.stdout)
+
+    def test_an_unreadable_gitignore_is_a_finding_not_a_pass(self):
+        # grep exits 2 on error and 1 on no-match, so treating both as
+        # "nothing named" lets an unreadable ignore file pass the project
+        # silently.
+        with tempfile.TemporaryDirectory() as root:
+            self.project(root, [".ai/"])
+            os.chmod(os.path.join(root, ".gitignore"), 0o000)
+            try:
+                r = run_check(project_roots=root)
+            finally:
+                os.chmod(os.path.join(root, ".gitignore"), 0o644)
+        self.assertEqual(r.returncode, 1,
+                         "an unreadable .gitignore read as nothing to check")
+        self.assertIn("could not", r.stdout.lower())
+
+    def test_non_git_dir_skipped(self):
+        with tempfile.TemporaryDirectory() as root:
+            with open(os.path.join(root, ".gitignore"), "w") as f:
+                f.write(".ai/\n")
+            r = run_check(project_roots=root)
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    def test_project_without_gitignore_skipped(self):
+        with tempfile.TemporaryDirectory() as root:
+            os.makedirs(os.path.join(root, ".git"))
+            r = run_check(project_roots=root)
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    def test_unrelated_ignore_lines_no_flags(self):
+        with tempfile.TemporaryDirectory() as root:
+            self.project(root, ["*.pyc", "node_modules/", "dist/"])
+            r = run_check(project_roots=root)
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+
+class SignalAccount(unittest.TestCase):
+    # --- Normal cases ---------------------------------------------------
+
+    def test_registered_account_passes(self):
+        r = run_check(signal_accounts="Number: +15045173983 ...")
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+    def test_no_account_flags(self):
+        # The velox case: a wiped registration silently breaks paging for
+        # the whole fleet, because agent-text relays into this machine.
+        r = run_check(signal_accounts="")
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("signal", r.stdout.lower())
+
+    # --- Error cases ----------------------------------------------------
+
+    def test_missing_binary_flags(self):
+        r = run_check(signal_accounts="MISSING")
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("signal-cli", r.stdout)
+
+    def test_a_stray_signal_missing_in_the_environment_is_ignored(self):
+        # The script's own internal flag must not be settable from outside,
+        # or a caller's unrelated variable turns a registered account into a
+        # "signal-cli is not installed" finding.
+        env = dict(os.environ)
+        env.update({"PRC_FAILED_UNITS": "", "PRC_UNIT_STATES": "",
+                    "PRC_LOCAL_SCAN_ROOTS": "", "PRC_PROJECT_ROOTS": "",
+                    "PRC_SIGNAL_ACCOUNTS": "+15045551234",
+                    "signal_missing": "1"})
+        r = subprocess.run(["sh", CHECK], capture_output=True, text=True,
+                           timeout=30, env=env)
+        self.assertEqual(r.returncode, 0, r.stdout)
+
+
+class ProbeFailure(unittest.TestCase):
+    """A probe that could not run must never read as a clean check.
+
+    This is the defect the whole script exists to catch, so it would be the
+    worst possible place to have it. `systemctl --user` exits 1 with empty
+    output when there is no user bus -- over ssh, from cron, under sudo, or on
+    a TTY before the graphical session starts. Reading that as "no failed
+    units" reports a machine as healthy precisely when nothing can be checked.
+    """
+
+    def unset(self, *names):
+        """Run with the named seams unset, so the real probes execute."""
+        env = dict(os.environ)
+        env.update({"PRC_FAILED_UNITS": "", "PRC_UNIT_STATES": "",
+                    "PRC_LOCAL_SCAN_ROOTS": "", "PRC_PROJECT_ROOTS": "",
+                    "PRC_SIGNAL_ACCOUNTS": "+15045551234"})
+        for n in names:
+            env.pop(n, None)
+        env["XDG_RUNTIME_DIR"] = "/nonexistent-runtime-dir"
+        return subprocess.run(["sh", CHECK], capture_output=True, text=True,
+                              timeout=30, env=env)
+
+    # --- Error cases ----------------------------------------------------
+
+    def test_unreachable_user_bus_is_a_finding_not_a_pass(self):
+        r = self.unset("PRC_FAILED_UNITS")
+        self.assertEqual(r.returncode, 1,
+                         "a failed probe reported the machine as clean")
+        self.assertIn("could not", r.stdout.lower())
+
+    def test_unreachable_user_bus_fails_the_unit_state_check_too(self):
+        r = self.unset("PRC_UNIT_STATES")
+        self.assertEqual(r.returncode, 1,
+                         "a failed probe reported the machine as clean")
+
+    def test_an_unusable_tmpdir_is_a_finding_not_a_pass(self):
+        # Every check stages its input through a temp file. If that write
+        # fails, each loop reads nothing and every check comes back clean --
+        # with real findings passed in.
+        env = dict(os.environ)
+        env.update({"PRC_FAILED_UNITS": "user:calendar-sync.service",
+                    "PRC_UNIT_STATES": "", "PRC_LOCAL_SCAN_ROOTS": "",
+                    "PRC_PROJECT_ROOTS": "",
+                    "PRC_SIGNAL_ACCOUNTS": "+15045551234",
+                    "TMPDIR": "/nonexistent-tmp-dir"})
+        r = subprocess.run(["sh", CHECK], capture_output=True, text=True,
+                           timeout=30, env=env)
+        self.assertEqual(r.returncode, 1,
+                         "an unwritable TMPDIR swallowed a real finding")
+
+
+class RealUnitDirEnumeration(unittest.TestCase):
+    """Check 2's unseamed path, where the unit files are read off disk.
+
+    The PRC_UNIT_STATES seam skips this enumeration entirely, so a defect in
+    it survives every seamed test. That is where the dangling-stow-link case
+    lives, and a dangling stow link is precisely the requirement's headline
+    example of a unit file that LOOKED fine.
+    """
+
+    def run_real(self, config_home):
+        env = dict(os.environ)
+        env.update({"PRC_FAILED_UNITS": "", "PRC_LOCAL_SCAN_ROOTS": "",
+                    "PRC_PROJECT_ROOTS": "",
+                    "PRC_SIGNAL_ACCOUNTS": "+15045551234",
+                    "XDG_CONFIG_HOME": config_home})
+        env.pop("PRC_UNIT_STATES", None)
+        return subprocess.run(["sh", CHECK], capture_output=True, text=True,
+                              timeout=30, env=env)
+
+    # --- Boundary cases -------------------------------------------------
+
+    def test_a_dangling_stow_link_is_enumerated_not_skipped(self):
+        with tempfile.TemporaryDirectory() as home:
+            unit_dir = os.path.join(home, "systemd", "user")
+            os.makedirs(unit_dir)
+            os.symlink("/nonexistent/stow/roam-sync.timer",
+                       os.path.join(unit_dir, "roam-sync.timer"))
+            r = self.run_real(home)
+        self.assertEqual(r.returncode, 1,
+                         "a dangling stow link read as nothing to check")
+        self.assertIn("roam-sync.timer", r.stdout)
+        self.assertIn("missing target", r.stdout)
+
+    # --- Error cases ----------------------------------------------------
+
+    def test_a_missing_unit_directory_is_a_finding(self):
+        with tempfile.TemporaryDirectory() as home:
+            r = self.run_real(home)
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("no user unit directory", r.stdout)
+
+
+class WedgedSystemctl(unittest.TestCase):
+    """A systemd manager that never answers must not hang the check.
+
+    Seen live on velox 2026-08-17: the user manager spun at 96% CPU with
+    `is-enabled`, `cat`, and `list-unit-files` all hanging while `list-units`
+    still returned. Unbounded, the check stops at the first unit and never
+    runs checks 3 through 5, so the machine most in need of checking is the
+    one it reports nothing about.
+    """
+
+    def run_with_fake(self, script_body, timeout_s="1"):
+        """Run against a fake systemctl, with check 2's unit dir empty.
+
+        Pointing XDG_CONFIG_HOME at an empty directory keeps check 2 from
+        making one call per real unit, so the test measures the bound rather
+        than the size of this machine's unit directory.
+        """
+        with tempfile.TemporaryDirectory() as d:
+            fake = os.path.join(d, "systemctl")
+            with open(fake, "w") as f:
+                f.write(script_body)
+            os.chmod(fake, 0o755)
+            env = dict(os.environ)
+            env.update({"PRC_LOCAL_SCAN_ROOTS": "", "PRC_PROJECT_ROOTS": "",
+                        "PRC_SIGNAL_ACCOUNTS": "+15045551234",
+                        "PRC_SYSTEMCTL": fake,
+                        "PRC_SYSTEMCTL_TIMEOUT": timeout_s,
+                        "XDG_CONFIG_HOME": d})
+            env.pop("PRC_FAILED_UNITS", None)
+            env.pop("PRC_UNIT_STATES", None)
+            start = time.monotonic()
+            r = subprocess.run(["sh", CHECK], capture_output=True,
+                               text=True, timeout=60, env=env)
+            return r, time.monotonic() - start
+
+    # --- Error cases ----------------------------------------------------
+
+    def test_a_hanging_systemctl_is_bounded_and_reported(self):
+        r, _ = self.run_with_fake("#!/bin/sh\nsleep 300\n")
+        self.assertEqual(r.returncode, 1)
+        self.assertIn("could not query user units", r.stdout)
+        # The run must reach the end rather than stopping at the first call.
+        self.assertIn("check 5/5", r.stdout)
+
+    def test_a_hanging_systemctl_does_not_stall_the_whole_run(self):
+        # The fake sleeps 8s against a 1s bound, so a bounded run lands near
+        # 2s (two calls) and an unbounded one near 16s. Deliberately short
+        # enough that losing the bound fails this assertion in seconds rather
+        # than hitting the subprocess ceiling a minute later -- a regression
+        # nobody waits out is a regression nobody catches.
+        _, elapsed = self.run_with_fake("#!/bin/sh\nsleep 8\n")
+        self.assertLess(elapsed, 6,
+                        "the run was not bounded by PRC_SYSTEMCTL_TIMEOUT")
+
+
+class Reporting(unittest.TestCase):
+    # --- Normal cases ---------------------------------------------------
+
+    def test_findings_counted_in_summary(self):
+        # Assert the count in the summary line specifically. A bare
+        # assertIn("2") passes on the always-present "check 2/5" text, so it
+        # stays green even when the counter is arithmetically wrong.
+        r = run_check(failed_units="user:a.service\nuser:b.service",
+                      unit_states="c.timer disabled")
+        self.assertEqual(r.returncode, 1)
+        summary = r.stdout.strip().splitlines()[-1]
+        self.assertEqual(summary, "3 finding(s) across 5 checks")
+
+    def test_the_summary_count_tracks_every_check(self):
+        # One finding from each of the five, so a counter that drops or
+        # double-counts any single check shows up here.
+        with tempfile.TemporaryDirectory() as scan, \
+             tempfile.TemporaryDirectory() as proj:
+            open(os.path.join(scan, "orphan.example"), "w").close()
+            os.makedirs(os.path.join(proj, ".git"))
+            with open(os.path.join(proj, ".gitignore"), "w") as f:
+                f.write(".ai/\n")
+            r = run_check(failed_units="user:a.service",
+                          unit_states="b.timer disabled",
+                          local_roots=scan, project_roots=proj,
+                          signal_accounts="")
+        summary = r.stdout.strip().splitlines()[-1]
+        self.assertEqual(summary, "5 finding(s) across 5 checks")
+
+    def test_help_exits_zero(self):
+        r = subprocess.run(["sh", CHECK, "--help"],
+                           capture_output=True, text=True, timeout=10)
+        self.assertEqual(r.returncode, 0)
+        self.assertIn("post-rebuild-check", r.stdout)
+
+    # --- Error cases ----------------------------------------------------
+
+    def test_unknown_flag_errors(self):
+        r = subprocess.run(["sh", CHECK, "--bogus"],
+                           capture_output=True, text=True, timeout=10)
+        self.assertNotEqual(r.returncode, 0)
+
+
+if __name__ == "__main__":
+    unittest.main()