Bike unlocked again · ~1 s after reconnect
Lasso is an iPhone app made for Cowboy e-bikes with a faulty battery: cells out of balance, worn cells or a tired contact that make the pack cut out for a moment under load. The bike loses power, reboots locked, drops its Bluetooth connection, and the motor is gone. The Cowboy app's Auto Unlock does not kick in again mid-ride. Lasso notices the drop and sends the unlock within about a second of the bike coming back, so you keep pedalling with assist instead of stopping in traffic.
iPhone · iOS 17+ · 7-day free trial · no subscription
How it works
As you already have. Lasso reuses that Bluetooth pairing. No code, no Cowboy account.
It shows up by name, usually already marked as linked.
It watches the Bluetooth link and re-unlocks the bike when it reboots mid-ride.
The problem
Cowboy batteries age like any lithium pack. When cell groups drift out of balance, the weakest group hits the battery management system's low-voltage cut-off first, especially under load on a hill or at a start, and the pack switches off for a fraction of a second even though the display still showed plenty of charge. A worn cell or a tired contact does the same. The bike's main board loses power, reboots, and a Cowboy always boots locked: no motor assist, lights off, and the Bluetooth connection to your phone is dropped. Three to five seconds later the bike is back on Bluetooth, locked.
The official app's Auto Unlock only fires on a fresh approach and movement detection, not on a reconnect mid-ride, so you ride without assist until you stop, open the app or press the button, and wait for the unlock.
Replacing the battery fixes it; Lasso is the cheap alternative while you ride the old one down.
The fix
Lasso uses iOS's Bluetooth background mode with state restoration, so the system wakes it for bike events even when the app is not on screen, and relaunches it if iOS had to free memory. iOS shares one Bluetooth link between Lasso and the Cowboy app, so both coexist.
A ride starts when the bike is seen unlocked. If the link drops and comes back within 60 seconds with the bike locked, that was a reboot, and Lasso writes the unlock. A lock notification within 15 seconds of the bike moving is treated the same way. A lock at standstill, or a reconnect after a longer absence, ends the ride and is respected, so your bike still locks when you park it.
One byte on the bike's lock characteristic. The bike acknowledges in about 60 milliseconds. Nothing in the motor controller or firmware is touched.
A Live Activity on the Lock Screen and in the Dynamic Island shows lock state, battery, voltage, speed, distance and how many times it re-unlocked. A notification confirms each re-unlock.
Every connect, disconnect, drop and lock change with the error code, how long the link was up, signal strength, battery voltage and speed. Export it as text to understand how your battery is doing, or to send to support.
If your bike needs a longer pause after rebooting or a different write type, switch to Patient, Key fob or Aggressive in Settings without a new app version.
The app
Compatibility
Tested
The re-unlock has been verified on a real bike by forcing the bike's communication board to reboot and watching Lasso bring it back unlocked.
Untested
Public reverse engineering of the Cowboy Bluetooth protocol shows the same lock mechanism on these models, so Lasso will most likely work, but nobody has confirmed it yet.
The 7-day trial exists for exactly this: try it on your bike, and if it does not work, you have paid nothing. Please report your result either way through support; it helps the next rider.
Price
7 days free
then Lifetime, one-time. No subscription.
Try everything free for 7 days, then one Lifetime purchase.
Download on the App StoreFAQ
An ageing battery can briefly lose contact or sag under load. The bike's electronics reboot, and a Cowboy always starts up locked. The app's Auto Unlock does not run again mid-ride, so the motor stays off until you stop and unlock by hand.
Lasso is tested on a Cowboy 3 running firmware 4.21.5. Cowboy 4, Cowboy 4 ST, Cruiser, Cruiser ST and Cross expose the same Bluetooth lock mechanism according to public reverse engineering, but they have not been verified. Lasso is free to try for 7 days.
No. You keep using the Cowboy app for everything else. Lasso reuses the Bluetooth pairing the Cowboy app created and runs next to it; iOS shares one Bluetooth connection between both apps.
No. It writes the same unlock command the official app sends, and can toggle the lights. It never changes motor controller settings, speed limits or firmware.
An idle Bluetooth Low Energy connection costs very little. Lasso only wakes up for bike events: connect, disconnect and lock changes.
GPLv3
The code is on GitHub under the GPLv3, including a platform-neutral description of the Cowboy Bluetooth protocol (lock characteristic, dashboard stream, Nordic UART with Modbus frames) for anyone who wants to build an Android version. Protocol knowledge builds on the Bronco Unleashed, Cowboy Untamed and cowboyunleashed projects.
Before you install
Lasso