The application scope in PeriodApplication was built with SupervisorJob and
no CoroutineExceptionHandler, and ReminderCoordinator launchIns two Room
flows on it. SupervisorJob stops a failing child cancelling its siblings; it
does not stop the exception, which reaches the thread's default handler and
ends the process.
That scope is the one that runs with nobody watching. Application.onCreate
runs in every process, including the ones WorkManager starts after a reboot
and at the daily reminder — no Activity, no screen, nothing to show an error.
Both ViewModels already install a handler; the one place a crash is invisible
did not.
The trigger is real rather than theoretical: repository.forecast runs the
prediction engine inside the flow, and Prediction's init block enforces its
window invariants with require.
Three layers, outermost last:
- ReminderCoordinator catches per chain, so one failing collection cannot
take the other down. Doing nothing on failure is deliberate — cancelling
the schedule would turn a failed read into reminders silently switched
off until the user next touched a notification setting.
- ReminderWorker returns success and posts nothing when it cannot read what
it needs, which is already its behaviour with no history. Cancellation is
rethrown rather than swallowed.
- The scope handler is a backstop whose only job is that the process lives.
It cannot log: checkNoHealthLogging covers this module, and an exception
message here can carry a date derived from a cycle.
The chains moved into internal functions taking flows so the catch is
reachable from a test. CycleRepository is final with an internal constructor,
which is right for a data boundary and wrong for faking, and adding a mocking
library to reach one catch would have been the worse trade.
Proved to fail, per GUARDS.md §1: removing the handler fails exactly one test
(ApplicationScopeTest.kt:69), and removing either catch fails exactly its own.
GUARDS.md gains §8. prove-guard.sh decides a guard caught the mutation from
the runner's exit code, and cannot tell a broken test from a malformed
command. Its first use here reported a clean catch when Gradle had actually
rejected `:app:test --tests` as an unknown option and run nothing. The same
tool's line-counting fallback also means the three documented boundary proofs
in architecture/README.md have been exiting 3 rather than 0 since they were
written; they now carry the fail pattern that makes them exit 0.
closes#45
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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