# Privacy: Period Tracker

```text
Status: Draft
Owner: _null
Last reviewed: 2026-08-20
Governs: README.md as the project-facing overview for Privacy: Period Tracker
Review trigger: The first buildable feature release; any change to the stack, the
                privacy promise, or how the project is built and run
```

A private Android period tracker that learns **your** cycle rather than the
average person's — and never sells your data.

[What it is](#what-it-is) | [Status](#status) | [Build and run](#build-and-run) |
[Repository map](#repository-map) | [Project docs](#project-docs) |
[Agent notes](#agent-notes)

_{ Android / Google Play | Kotlin + Jetpack Compose | Room, offline-first |
Personalized prediction with an honest window | Discreet notifications |
No account, no server, no data sale }_

The core loop is:

```text
Track → Learn → Predict → Remind → Learn again
```

## What it is

A focused tracker that answers one question well: **when is my next period
likely to start?** It records confirmed period dates, learns the individual's
pattern from them, and produces a most-likely date with a window and a
confidence label — never a bare date presented as fact. From that it estimates
ovulation and the fertile window, and it asks discreetly whether the period
started, using both *yes* and *not yet* to improve the next forecast.

Two promises hold the product up:

> **Your period. Better predicted.** — once there is enough personal history,
> the app must not fall back to a generic 28-day cycle. A user recording 34, 35,
> 36, 34, 35 who is predicted 28 is a core product defect, not a tuning issue.

> **Your cycle belongs to you.** We will never sell period history, fertility
> information, ovulation estimates, cycle predictions or personally identifiable
> information — to advertisers, data brokers or anyone else.

The second is held structurally rather than remembered, and the rule was written
before the code it constrains: `checkModuleBoundaries` in the root
`build.gradle.kts` already carries `":core:ads" to emptySet()`, so when the ads
module arrives in Batch 07 it may declare **no** project dependency at all —
stricter than "nothing from the cycle database or the prediction domain". It is
not in `settings.gradle.kts` yet, so today the rule matches no module, which is
why the guard is proved against injected violations rather than trusted.

What it deliberately is **not** — no community, no pregnancy mode, no chatbot,
no article feed, no symptom encyclopedia, and not contraception — is in
[docs/planning/PROJECT_PLAN.md](docs/planning/PROJECT_PLAN.md).

## Status

Foundation through Batch 06 are closed, Batch 08 polish is complete, and
monetization (Batch 07) remains unbuilt. Every row below cites the file or test
that proves it.

| Surface | Status | Evidence |
| --- | --- | --- |
| Documentation tree and tracker convention | Adopted | this tree; milestones and issues in the tracker |
| Gradle / Kotlin / Compose project | Builds | `./gradlew assembleDebug` and `assembleRelease` both pass |
| Material 3 theme and tokens | Built | `core/designsystem` |
| Four-tab navigation shell | Built | `app/src/main/kotlin/dev/privacyllc/period/navigation/PeriodApp.kt` — Today, Calendar, Insights, Settings, each wired to its real screen |
| Cycle model and interval derivation | Built | `domain/cycle` (13 tests); `domain/prediction/src/main/kotlin/dev/privacyllc/period/domain/prediction/IntervalAnalysis.kt` (12 tests) |
| Prediction engine | Built — personalized | `PersonalPredictionEngine`, wired in `app/src/main/kotlin/dev/privacyllc/period/di/DataModule.kt`; the 12 acceptance tests from PRODUCT_PLAN §51 run against both engines (`PersonalAcceptanceTest`, `BaselineAcceptanceTest`), and `EngineComparisonTest` scores the personal engine against the retained baseline every build |
| Room persistence, DataStore | Built | `core/database` (schema v1 exported, `SchemaTest` + `scripts/schema-guard.sh`), `core/datastore`, `core/data` |
| Onboarding, Today, Calendar, Insights | Built | `app/src/main/kotlin/dev/privacyllc/period/feature/` — onboarding, today, calendar, insights; `OnboardingViewModelTest`, `TodayViewModelTest`, `TodayUiStateTest` |
| Fertility window and ovulation estimate | Built | `domain/prediction/src/main/kotlin/dev/privacyllc/period/domain/prediction/FertilityEstimate.kt`, 11 tests; shown on Today and Calendar |
| Discreet notifications | Built | `core/notifications` (24 JVM tests), instrumented `NotificationPrivacyTest` |
| App lock (PIN + fingerprint) | Built | `core/security` (Keystore-backed verifier, lockout policy), `app/src/main/kotlin/dev/privacyllc/period/lock` gate; 28 JVM tests plus `KeystoreVerifierTest` run on `PeriodMinSdk26` and `PeriodQA` |
| Discreet launcher alias | Built | `app/src/main/AndroidManifest.xml` aliases; `LauncherAliasSwitcherTest`, `PrivacyViewModelTest`; device checked on `emulator-5554` |
| Export My Data | Built | `core/export` (format pinned byte-for-byte against `core/export/src/test/resources/golden-v1.json`), written through the Storage Access Framework by `app/src/main/kotlin/dev/privacyllc/period/feature/export` |
| Monetization | Not built | Batch 07 |
| QA | Round 3 run, partial | [docs/qa/ClaudeReport.md](docs/qa/ClaudeReport.md) — partial at `0451fbe`; TalkBack, text scaling, `minSdk` and a real locked screen still unreached |

`BaselinePredictionEngine` is still in the tree, but it stopped being the
product in Batch 02. `DataModule` provides `PersonalPredictionEngine` — the
recency-weighted, trend-aware, "not yet"-conditioned engine PRODUCT_PLAN §12
specifies — and the baseline is now the control: `EngineComparisonTest` scores
both over the §51 fixtures every build, so "the new engine is better" is a number
rather than an opinion.

## Build and run

Prerequisites: a JDK 21 and the Android SDK with **platform 37** and
**build-tools 37.0.0** installed, `ANDROID_HOME` set.

```bash
git config core.hooksPath .githooks   # per clone, every clone — see below

./gradlew test                        # JVM suites, no emulator, ~1s
./gradlew assembleDebug               # app/build/outputs/apk/debug/
./gradlew assembleRelease             # minified, unsigned
```

`compileSdk` is 37 because the current AndroidX libraries require it;
`targetSdk` is 36, Google Play's floor for new apps from 2026-08-31. They are
deliberately different — raising `targetSdk` opts the app into runtime behaviour
changes and is a tested decision, not a build fix.

**`git config core.hooksPath .githooks` is per clone.** Without it the hooks are
not installed and fail silently, which is the failure mode they exist to
prevent. `post-commit` pushes; see
[docs/architecture/githooks/README.md](docs/architecture/githooks/README.md).

## Repository map

```text
app/                     application module, MainActivity, navigation shell, DI
core/designsystem/       Material 3 theme and colour tokens
core/database/           Room entities, DAOs, converters, the exported schema
core/datastore/          user preferences that are not health history
core/data/               CycleRepository — the only module that touches a DAO
core/notifications/      reminder copy, privacy modes, WorkManager scheduling
domain/cycle/            pure Kotlin — period records, cycle derivation
domain/prediction/       pure Kotlin — the forecast, window and confidence
scripts/                 six from the template, plus schema-guard.sh, our own
.githooks/               pre-commit, commit-msg, post-commit
docs/                    product, architecture, design, brand, QA, security, history
```

`domain/*` are `kotlin("jvm")` modules and cannot see the Android SDK. That is
on purpose: the prediction engine is the product, so it needs the most tests,
and tests that need an emulator are tests that do not get run.

## Project docs

Detailed procedures belong in docs; **open work belongs in the tracker**, not in
this README.

| Doc | Purpose |
| --- | --- |
| [docs/DOC_TRUST_MAP.md](docs/DOC_TRUST_MAP.md) | Which document owns which answer, and which source wins when records disagree. **Read this first.** |
| [docs/planning/PRODUCT_PLAN.md](docs/planning/PRODUCT_PLAN.md) | The full V1 specification — prediction requirements, screens, copy, compliance |
| [docs/planning/PROJECT_PLAN.md](docs/planning/PROJECT_PLAN.md) | The short vision, the stack and its reasons, and what this is deliberately not |
| [docs/WORK_CYCLE.md](docs/WORK_CYCLE.md) | What happens at the end of a piece of work |
| [docs/architecture/README.md](docs/architecture/README.md) | Modules, boundaries, data shapes, migrations |
| [docs/design/README.md](docs/design/README.md) | Tone, and the four rules that settle design arguments |
| [docs/security/SECURITY.md](docs/security/SECURITY.md) | Threat model, the advertising boundary, logging rules |
| [docs/TOOLS.md](docs/TOOLS.md) | Which script to run, and which ones can stop you |

## Where the tracker is

Milestones are batches, issues are deliverables, and severity labels are exactly
`P0`, `P1`, `P2` and `release-blocker`. Credentials come from the environment,
never from this repository:

```bash
set -a; . ~/.openclaw/docker-registry.env; set +a
python3 scripts/forgejo-issue.py list
```

Two traps that cost an hour each otherwise: Cloudflare 1010-blocks clients that
do not look like a browser or curl, so every request needs
`User-Agent: curl/8.5.0` — `forgejo-issue.py` sends it and anything new must
too. And `/issues` returns pull requests unless `type=issues` is passed.

## Agent notes

- **Product truth comes from the code and the tracker before prose.**
- Do not keep a work list in this README or anywhere else in `docs/`.
- Finish with [docs/WORK_CYCLE.md](docs/WORK_CYCLE.md), every time: close what
  you finished with the evidence, close the milestone if the batch landed,
  update the documents the change triggered **in the same commit**, push, log
  the entry, then reconcile and write the summary and next action.
- Nothing on privacyllc.dev writes itself except the tracker counts and the
  pushed docs.
- **Do not claim a feature is built** unless you can cite the file, test or
  screenshot that proves it. The status table above is the standard.
- **Verify current stable versions before changing the toolchain.** The ones in
  `gradle/libs.versions.toml` were checked against the official sources on
  2026-08-18; PRODUCT_PLAN.md asks for that check rather than for its own
  numbers to be trusted.
- Never put a cycle date, a prediction or a fertility state into a log, an
  analytics event, or an ad request.