flash.comma.ai

This tool allows you to flash AGNOS onto your comma device.

AGNOS is the Ubuntu-based operating system for your comma 3/3X.

Requirements

A web browser which supports WebUSB (such as Google Chrome, Microsoft Edge, Opera), running on Windows, macOS, Linux, or Android.
A USB-C cable to power your device outside the car.
Another USB-C cable to connect the device to your computer.

USB Driver

You need additional driver software for Windows before you connect your device.

Download and install Zadig.
Under Device in the menu bar, select Create New Device.
Fill in three fields. The first field is just a description and you can fill in anything. The next two fields are very important. Fill them in with 18D1 and D00D respectively. Press "Install Driver" and give it a few minutes to install.

No additional software is required for macOS or Linux.

Fastboot

Follow these steps to put your device into fastboot mode:

Power off the device and wait for the LEDs to switch off.
Connect power to the OBD-C port (port 1).
Then, quickly connect the device to your computer using the USB-C port (port 2).
After a few seconds, the device should indicate it's in fastboot mode and show its serial number.

image showing comma three and two ports. the upper port is labeled 1. the lower port is labeled 2.

If your device shows the comma spinner with a loading bar, then it's not in fastboot mode. Unplug all cables, wait for the device to switch off, and try again.

Flashing

After your device is in fastboot mode, you can click the button to start flashing. A prompt may appear to select a device; choose the device labeled "Android".

The process can take 15+ minutes depending on your internet connection and system performance. Do not unplug the device until all steps are complete.

Troubleshooting

Cannot enter fastboot or device says "Press any key to continue"

Try using a different USB cable or USB port. Sometimes USB 2.0 ports work better than USB 3.0 (blue) ports. If you're using a USB hub, try connecting the device directly to your computer, or alternatively use a USB hub between your computer and the device.

My device's screen is blank

The device can still be in fastboot mode and reflashed normally if the screen isn't displaying anything. A blank screen is usually caused by installing older software that doesn't support newer displays. If a reflash doesn't fix the blank screen, then the device's display may be damaged.

After flashing, device says unable to mount data partition

This is expected after the filesystem is erased. Press confirm to finish resetting your device.

General Tips

Try another computer or OS
Try different USB ports on your computer
Try different USB-C cables, including the OBD-C cable that came with the device