"Your cycle belongs to you" was a promise the app could not keep: there was no
way to get the data out.
## The format, because it outlives the batch
One pretty-printed JSON file. The issue asks for "human-readable" and means it —
this is what somebody's archive will be in for years, so it is a contract with
eight rules written down beside it, not an implementation detail.
Pinned byte-for-byte against a committed golden file, which doubles as the
documented example so SECURITY.md links at it rather than keeping a second copy
that would drift. A reformat, a reordered key or a changed date rendering all
fail in a test rather than in an archive.
Dates are ISO calendar dates with no timezone and no conversion, ever.
Converters.kt stores a LocalDate as its epoch day precisely so it "cannot carry
a timezone by accident", and a zone-aware formatter here would shift every date
for users east or west of whoever wrote it — a cycle tracker off by one day is
wrong in the way that matters. There is a test that renders the same fixture in
UTC, +14 and -12 and requires identical bytes, because that bug would never fire
where it was written.
## Plaintext, and that is the decision rather than the default
An earlier note said this would be encrypted. It should not be, and SECURITY.md
now says why: the export is the copy that makes a lost Keystore key survivable
instead of final — the exact condition recorded for ever revisiting database
encryption. Putting it behind a passphrase reproduces the failure that decision
was taken to avoid: a forgotten secret and an archive nobody, including this
app, can open. §45's "prefer encrypted backup/export formats" is scoped to
backup, which this is not.
## Only the user's own data, as a compile error
:core:export is pure JVM and depends on :domain:cycle alone. Prediction,
PredictionAccuracy, FertilityEstimate and CycleRecord live in
:domain:prediction and are simply not on its classpath, and kotlin("jvm") keeps
android.os.Build off it too — so a forecast or a device fact cannot be added by
accident. The key set is asserted with assertEquals rather than contains, so a
new field is a failing test rather than a silent addition.
Row ids are out because they are monotonic and would disclose how many records
the user DELETED. The Play entitlement is out because a purchase one file-edit
away from being granted is a purchase that will be.
## No second copy, ever
The Storage Access Framework writes straight into the document the user picked.
The alternative — write to cacheDir, share by FileProvider, delete after —
creates the temporary file the issue warns about and races the receiving app
still reading it. A test walks cacheDir after a successful export and requires
it empty; it fails the moment anybody reintroduces that pattern.
The destination is parked until the session is unlocked. Returning from the
picker can re-lock, and writing while locked would hand the whole history to
whoever took the phone during the save dialog.
## Two new guards, both proved to fail
checkNoSharedStorageWrites: §45's shared-storage ban was enforced by nobody
having typed it. checkPermissions structurally cannot see it — it matches
<uses-permission>, and a <provider> declaring FileProvider merges green.
checkNoHealthLogging gains a completeness check. A module missing from
modulesSeeingHealthData was silently exempt with a green build, which
app/proguard-rules.pro has described as a hazard since before :core:security and
:core:export existed. Every module must now be in that list or in an explicit
modulesWithNoHealthData with its reason; being in neither is a violation rather
than an exemption.
261 JVM tests, none skipped. Five guards green.
closes#35
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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