Solo Forge

Local-first intermittent fasting, calorie, weight & workout tracker

Solo Forge is a free and open source, local-first Android fitness app for fasting, nutrition, weight tracking, and workout timing. It is GPL-3.0 licensed and built to keep user data on the device, with no backend, account system, analytics, or cloud telemetry.

The only intentional outbound network request is a user-initiated OpenRouter call for food analysis (photo or text description), using an API key supplied by the user. AI features can be switched off entirely in Settings.

Website: soloforge.dimitroff.work — landing page and privacy policy. Maintained in the separate soloforge-site repo (Cloudflare Pages, deploys on push); update it when a release changes features, screenshots, or the store description.

Screenshots

Current Features

• Intermittent fasting timer with 16:8, 18:6, 20:4, and 36 hour modes.
• Smart fasting reminders driven by timer state instead of fixed daily spam.
• AI-assisted food analysis (photo or text description) through an automatic OpenRouter model escalation chain, with an off switch in Settings.
• Manual meal entry and one-tap meal presets when the user does not want to use AI.
• Editable food entries, including proportional macro recalculation by total grams.
• Local nutrition tracking with calorie and macro goals.
• Versioned JSON backup: export, import (merge or replace), and an optional auto-backup folder that rewrites the backup file on every data change.
• Weight tracking with edit/delete support, history, charting, and a weekly weigh-in reminder.
• Workout timers:
  • simple session timer with pause/resume
  • interval timer with periodic audio cues
  • exercise/rest toggle timer
• Home dashboard with daily fasting, nutrition, workout, weight, and calendar progress.
• Configurable bottom tabs.
• Local Room migrations with exported schemas and migration tests.

Privacy Model

Solo Forge is designed around local ownership of fitness data.

• No backend.
• No authentication.
• No analytics SDKs.
• No crash reporting SDKs.
• No Firebase.
• No broad media, contacts, or logs permissions.
• Android system cloud backup is disabled (allowBackup=false); device migration uses the explicit export/import flow.
• The OpenRouter API key is stored in encrypted local preferences and is never included in backups.
• Backup is explicit: a versioned JSON file exported on demand, or auto-written to a user-selected folder (which the user can sync to Drive/Dropbox themselves).

The app declares INTERNET only for food analysis through OpenRouter. That call happens only when the user starts an analysis; with AI features off, the app makes zero network calls.

Food analysis starts with google/gemini-3.1-flash-lite, escalates to openai/gpt-5.4-mini when confidence is low or hidden/mixed ingredients are likely, and uses google/gemini-3.1-pro-preview only if uncertainty remains.

Tech Stack

• Kotlin
• Jetpack Compose
• Material 3
• Single-activity architecture
• Hilt dependency injection
• Room SQLite storage
• DataStore preferences
• EncryptedSharedPreferences for the OpenRouter API key
• WorkManager for scheduled reminders
• Foreground services for active timers
• CameraX for food capture
• Ktor and kotlinx.serialization for OpenRouter
• Coil for image loading
• Hand-rolled Compose charts (no chart library)

Requirements

• Android Studio with Android SDK installed
• JDK 17
• Android emulator or physical Android device
• Min SDK 26
• Compile SDK 35
• Target SDK 35

Build

Clone the repo and open it in Android Studio, or build from the command line:

.\gradlew.bat assembleDebug

The debug APK is generated at:

app/build/outputs/apk/debug/app-debug.apk

Install on a connected emulator or device:

adb install -r app/build/outputs/apk/debug/app-debug.apk

Tests

Run the unit tests (backup format, calendar math, food escalation, OpenRouter parsing):

.\gradlew.bat testDebugUnitTest

Run the connected Room migration tests with an emulator or device attached:

.\gradlew.bat :app:connectedDebugAndroidTest

Run lint:

.\gradlew.bat lintDebug

F-Droid

Solo Forge is published on F-Droid as com.kbul.spicycrab. Listing content comes from:

.fdroid.yml
fastlane/metadata/android/en-US/

The fdroiddata recipe uses UpdateCheckMode: Tags with AutoUpdateMode: Version, so pushing a vX.Y.Z release tag is what triggers an F-Droid release (published in roughly 2–7 days). The official recipe deliberately has no AntiFeatures: — the F-Droid reviewer removed the NonFreeNet flag during inclusion review (fdroiddata MR !38080) because the OpenRouter feature is off by default, opt-in, and requires the user's own key. Do not re-add it.

Project Layout

app/src/main/java/com/kbul/spicycrab/
├── MainActivity.kt
├── SpicyCrabApp.kt
├── data/
│   ├── backup/
│   ├── db/
│   └── prefs/
├── di/
├── domain/
│   ├── fasting/
│   ├── nutrition/
│   ├── weight/
│   └── workout/
├── network/
├── notifications/
└── ui/
    ├── common/
    ├── fasting/
    ├── food/
    ├── home/
    ├── nav/
    ├── onboarding/
    ├── settings/
    ├── theme/
    ├── weight/
    └── workout/

The package name still uses the original com.kbul.spicycrab namespace. The app-facing brand is Solo Forge.

Room Migrations

Room migrations are mandatory. Do not use destructive migration fallbacks.

For schema changes:

1. Edit the entity.
2. Bump the Room database version.
3. Add a migration in Migrations.kt.
4. Append it to ALL_MIGRATIONS.
5. Build once to export the new schema under app/schemas/.
6. Add or update an androidTest migration test.

Branding

Brand notes and early SVG assets live in:

BRAND-BRIEF.md
brand/

License

Solo Forge is licensed under the GNU General Public License v3.0. See LICENSE for the full license text.

Status

Solo Forge is released and published on F-Droid, with debug-signed APKs on GitHub releases. Core features — fasting, food tracking, weight, workouts, dashboard, and JSON backup export/import — are in place; development continues on UI polish and broader device testing.