CruxCoach — Open-source Android app for Kilter Board, MoonBoard & Tension Board

One open-source Android app for all your climbing boards.

Kilter, MoonBoard, Tension and more — browse climbs, light up holds, log<br>your sessions, without an account, without Google services, without<br>anyone tracking your training.

7 boards, one app

Custom hold colors

Encrypted local logbook

German & English UI

Get on Zapstore<br>Download APK

Free. No account. Verifiable signed builds. Android 8.0+.

Existing catalogue and Bluetooth hold-lighting on all seven boards:

Kilter Board

MoonBoard

Tension Board

Grasshopper

Decoy

So iLL

Touchstone

Aurora and 12 Climb also appear on the board map as location-only layers.

What CruxCoach does

One app for every board you climb — open source, no account, no tracking, and your data never leaves your device unless you say so.

Browse every board's catalogue

Kilter, MoonBoard and five more boards — 496,000+ climbs in total. Filter by grade, angle, quality, move count, setter. Works offline once the board database is synced.

Light up holds via Bluetooth

Direct BLE to your Kilter Board, MoonBoard, Tension Board and more. Pick custom colors per role: start, hand, foot, top.

Set and share your own climbs

Create your own problems on any of the seven boards and publish them to the CruxCoach community over Nostr — no central server holding them, no gatekeeper.

Local, encrypted logbook

Sends, attempts, opinions, sessions — all stored on your device in an SQLCipher database. Never leaves unless you ask.

Share with climbers nearby

Other CruxCoach users at the same board see your current climb over Bluetooth — and you see theirs. No internet, no accounts.

Your training history, portable

Bring your history with you — import an Aurora data export (ascents, attempts, circuits), or sign in once with your Kilter account to pull your logbook directly. From there your data stays portable: export to JSON, or turn on automatic encrypted backup only you can restore.

Climb detail — grade, stats, and the hold sequence at a glance

Local logbook — every send and attempt stays on your device

Why CruxCoach exists.

On 26 March 2026, Aurora's Kilter app was pulled from the App Store and Play Store<br>after a dispute between Aurora Climbing and Kilter, LLC. Tens of thousands of climbers<br>lost access to their playlists, logbooks, and draft climbs overnight. The new official<br>app shipped half-finished, and people started asking the obvious question: why does my<br>training data live on someone else's server in the first place?

CruxCoach is one answer to that question. Your training history sits encrypted on your<br>phone. Your identity is a Nostr keypair you control, not an account someone can revoke.<br>The board database is content-addressed and downloaded to your device on first sync —<br>once you have it, you have it. And the whole thing is open source under the GPL: anyone<br>can audit it, fork it, run it.

It started narrow on purpose: Kilter only, Android only. With 0.2.0 it speaks the whole<br>family — Kilter, MoonBoard, Tension, Grasshopper, Decoy, So iLL and Touchstone. Still<br>Android only, still yours.

Privacy by architecture, not by promise

Privacy claims are easy. CruxCoach is built so the privacy holds even if we're lying about it.

No accounts, no signup. Your identity is a Nostr keypair generated on first launch, stored in the Android Keystore.

No Google Play Services. Works on de-Googled phones — GrapheneOS, /e/OS, LineageOS without GApps.

Encrypted local storage. Personal data lives in an SQLCipher database. Encryption key never leaves your device.

No telemetry, no analytics, no ads, no third-party SDKs. Outbound calls go to: Nostr relays you configure, Blossom servers for the board database, Codeberg for update checks, and the Kilter API only when you opt to import your logbook.

No central server we operate. The app uses public Nostr relays and Blossom servers run by independent operators.

Verifiable open-source builds. Code on Codeberg, releases signed, auto-updater pins the developer key on first install.

Runs on de-Googled Android — no Play Store, no Play Integrity

If your phone ships without Google services, CruxCoach is built for you:<br>nothing it does depends on Google.

No Google Play Services. CruxCoach calls no GMS APIs and runs fully on GrapheneOS, CalyxOS, /e/OS and LineageOS without GApps.

Install without the Play Store. Get it from Zapstore or sideload the signed APK from Codeberg. CruxCoach is not on Google Play and never requires it.

Updates without Google. The optional in-app updater pulls signed APK releases straight from Codeberg with TOFU certificate pinning — no Play Store and no Play Integrity check. On Zapstore installs it disables itself and lets the store update.

Install

Two ways to install today. Two more coming.

Zapstore recommended

Privacy-respecting, Nostr-native Android store. Verifies developer signatures. Auto-updates.

Open in Zapstore

Direct APK

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