A free, local-first 5/3/1 Wendler + BBB strength training tracker for iOS and Android. Built with React Native (Expo SDK 55) by a Claude coding agent on a 30-minute cron loop.
App · 531strength.com | Dev blog · 531strength.com/blog | How it's built · 531strength.com/process
Every 5/3/1 tracker I tried was either too general (treated it like any other program), too social (feeds, leaderboards, communities), or paywalled the features that mattered. I wanted something that did the Boring But Big math correctly, showed me a plate diagram without asking me anything, and got out of the way. So I built it.
No account required. No ads. No subscription. No data leaves your phone.
Enter your training maxes once. The app handles the rest: weekly percentages, plate math, BBB accessory sets, rest timers, cycle tracking, and PR detection. Implements Jim Wendler's 5/3/1 program exactly as written — including the 7th Week Protocol.
Program
- 5/3/1 structure — Day 1 (5/5/5+), Day 2 (3/3/3+), Day 3 (5/3/1+), Day 4 TM verification (7th Week Protocol — no deload week)
- BBB accessory sets — Boring But Big 5x10 calculated automatically at 50% Training Max
- All four lifts — squat, bench press, overhead press, deadlift
During a session
- Plate calculator — visual bar + plate layout for every working set, no input required
- Rest timer — background-safe countdown with alarm on completion; Android shows a live chronometer notification
- AMRAP logging — tap your reps, get your estimated 1RM, detect PRs automatically
Tracking
- PR detection — estimated 1RM logged after every AMRAP; certificate on new records
- Cycle progress — grid view of every session in the current cycle
- TM adjustment suggestions — after TM test week, calm data-driven suggestions
- Lift rollback — undo the last N sessions for any lift (settings Danger Zone)
Privacy
- Local-only — SQLite on-device, zero telemetry, no account, nothing ever leaves your phone
- lbs + kg — full unit support with correct increment rules per lift
| Platform | Link |
|---|---|
| Android | Google Play |
| iOS App Store | In App Store review - coming soon |
The entire app is built by a Claude coding agent running on a 30-minute cron. Each iteration the agent reads a Discord task queue, picks 12-15 improvements to ship, implements them across design/data/domain/features layers, runs the CI gauntlet, and commits - all autonomously. 94+ iterations have run; every line of code is the product of 30-minute agent sessions.
The agent team: rn-designer → rn-frontend → rn-qa. Orchestrated via the rn-expo-pipeline and do-work skills in .claude/skills/.
See 531strength.com/process for a full walkthrough of the loop, and the dev blog for field logs written by each expedition.
Stack
| Layer | Technology |
|---|---|
| Framework | React Native 0.83+ (New Architecture), Expo SDK 55 |
| Navigation | expo-router (file-based) |
| Database | Drizzle ORM + expo-sqlite |
| State / async | TanStack Query |
| Animation | React Native Reanimated 4 |
| Notifications | expo-notifications (iOS), react-native-notify-kit (Android live notification) |
| Haptics | expo-haptics |
| Linting | Biome (TypeScript strict) |
| Testing | Jest + @testing-library/react-native + fast-check (property tests) |
| E2E | Maestro |
Directory layout
apps/mobile/src/
app/ # expo-router routes (thin shells only)
design/ # tokens, theme, primitives — only place hex/px live
domain/ # pure 5/3/1 math — no React, no async, no DB
data/ # Drizzle ORM + expo-sqlite, TanStack Query hooks
features/ # screen composition
lib/ # pure helpers: haptics, time, plate logic, routes
Boundary rules
Four hard rules, enforced by a reviewer agent on every commit:
- Hex/px literals live only in
design/— all other layers import from tokens domain/is pure — no React, no async, no Drizzle; property-tested with fast-check- Components consume data via hooks — never import Drizzle directly
app/routes are thin shells — no logic, just param extraction and feature composition
These boundaries exist because the app is built by an agent: the reviewer enforces them automatically, so the system cannot drift even across hundreds of iterations.
# Prerequisites: Node 22, pnpm 9.15+
corepack enable && corepack prepare pnpm@latest --activate
pnpm install
# Build the dev-client APK (needs Android SDK + JDK 17)
pnpm build:dev
# OR build in the cloud (needs `eas login`)
eas build --profile development -p android
# Boot Metro — connect the dev-client APK
pnpm --filter @fivethreeone/mobile startThis project uses a custom dev client (not Expo Go). Native modules like expo-notifications and react-native-notify-kit require it. Install the dev-client APK on a device or emulator and connect via Metro. JS/TS edits hot-reload instantly; rebuilds are only needed when native modules change.
pnpm typecheck # tsc --noEmit across workspace
pnpm lint # biome
pnpm test # jest
pnpm run ci # full CI chain (typecheck + lint + test + boundary checks)
pnpm verify # ci + Metro bundle check + web build
# e2e (requires Maestro + dev client on device)
maestro test .maestro/flows/ # all flows
maestro test .maestro/flows/01-onboarding.yaml # individual flow| Doc | Purpose |
|---|---|
docs/DESIGN.md |
Product + visual design spec |
docs/ARCHITECTURE.md |
Stack, layout, boundary rules |
docs/CONTRIBUTING.md |
How to add a task, run the orchestrator |
docs/decision-log.md |
Notable decisions and their reasoning |
CLAUDE.md |
Agent orientation — start here if you're a Claude agent |
Source available — free to run for personal use; redistribution and commercial use require explicit permission. See LICENSE for full terms and docs/PRIVACY.md for data handling (short version: SQLite on-device, zero telemetry, nothing ever leaves your phone).