lost connection

[simontheflutist]

followed instructions on flash.comma.ai

port 1 cable is my Comma 3X's OBD-C.

Bug Report - flash.comma.ai

Device: comma four
Serial: N/A
Error: LOST_CONNECTION
Step: CONNECTING
Last Message: N/A

OS: Linux
Sandbox: None detected
Browser: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/151.0.0.0 Safari/537.36
URL: https://flash.comma.ai/
Time: 2026-08-08T00:24:01.285Z

Console Logs

[2026-08-08T00:23:45.605Z] [info] flash.comma.ai version: 2a2da7f
[2026-08-08T00:23:45.947Z] [info] [ImageManager] Initialized
[2026-08-08T00:23:55.238Z] [error] [Flash] Connection error {}
[2026-08-08T00:23:55.240Z] [debug] [Flash] error 4

[simontheflutist]

error when using my Apple USB-C

Bug Report - flash.comma.ai

Device: comma four
Serial: N/A
Error: LOST_CONNECTION
Step: CONNECTING
Last Message: N/A

OS: Linux
Sandbox: None detected
Browser: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/151.0.0.0 Safari/537.36
URL: https://flash.comma.ai/
Time: 2026-08-08T00:28:38.434Z

Console Logs

[2026-08-08T00:28:23.856Z] [info] flash.comma.ai version: 2a2da7f
[2026-08-08T00:28:23.903Z] [info] [ImageManager] Initialized
[2026-08-08T00:28:36.371Z] [error] [Flash] Connection error {}
[2026-08-08T00:28:36.373Z] [debug] [Flash] error 4

[simontheflutist]

power from car harness, data from laptop

Bug Report - flash.comma.ai

Device: comma four
Serial: N/A
Error: LOST_CONNECTION
Step: CONNECTING
Last Message: N/A

OS: Linux
Sandbox: None detected
Browser: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/151.0.0.0 Safari/537.36
URL: https://flash.comma.ai/
Time: 2026-08-08T00:39:04.991Z

Console Logs

[2026-08-08T00:38:48.405Z] [info] flash.comma.ai version: 2a2da7f
[2026-08-08T00:38:49.272Z] [info] [ImageManager] Initialized
[2026-08-08T00:38:58.233Z] [error] [Flash] Connection error {}
[2026-08-08T00:38:58.235Z] [debug] [Flash] error 4

[simontheflutist]

On my Android phone, USB-C to data port simply doesn't work. The device just boots normally and doesn't show up in flash.comma.ai.

[simontheflutist]

What I've tried: two different USB-C cables, my 3X's OBD-C and an Apple USB-C. Laptop (Chrome/Ubuntu) and S26 phone (Chrome/Android). Power from 5V Dell charger and from 12V car harness.

[simontheflutist]

Tried a third USB cable of unknown provenance. Same error. Chrome with and without incognito mode.

[simontheflutist]

Same error on a fourth USB cable. Support ticket 82804.

[stefpi]

work around for now

start a chrome instance with a fresh user data directory:

google-chrome --user-data-dir=/tmp/flash-chrome-test https://flash.comma.ai

and then run the flash process as normal

[stefpi]

another good place to look when stuff like this happens is: chrome://device-log/

for example. I was also having connection issues and the following was in my device log:

this is a bad experience though, so we need to figure out why this happens in the first place

[adeebshihadeh]

Looks like a permission issue?

[stefpi]

my chromium was installed from the ubuntu app center via snap which requires a connection to raw-usb snap package in order for flash to work.

in comparison, my google chrome installed via .deb from google website runs outside of sandbox and doesn't need anything.

[simontheflutist]

my Google Chrome is installed via deb too. Before trying your workaround @stefpi this is the error I get in device-log:

[simontheflutist]

@stefpi even with your user-dir workaround, I get the same error.

Bug Report - flash.comma.ai

Device: comma four
Serial: N/A
Error: LOST_CONNECTION
Step: CONNECTING
Last Message: N/A

OS: Linux
Sandbox: None detected
Browser: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/151.0.0.0 Safari/537.36
URL: https://flash.comma.ai/
Time: 2026-08-08T02:28:09.761Z

Console Logs

[2026-08-08T02:27:56.225Z] [info] flash.comma.ai version: 2a2da7f
[2026-08-08T02:27:57.560Z] [info] [ImageManager] Initialized
[2026-08-08T02:28:03.894Z] [error] [Flash] Connection error {}
[2026-08-08T02:28:03.895Z] [debug] [Flash] error 4

[andiradulescu]

permission error for #227 (comment) reported in #110

might be a good time to put a PR to detect this case and show the user the command it needs to run

[simontheflutist]

@andiradulescu that report is for snap install chromium. I'm on Google's deb:

(base) simon@simon-Precision-5560:~$ sudo apt show google-chrome-stable
Package: google-chrome-stable
Version: 151.0.7922.108-1
Priority: optional
Section: web
Maintainer: Chrome Linux Team <chromium-dev@chromium.org>
Installed-Size: 452 MB
Provides: www-browser
Pre-Depends: dpkg (>= 1.14.0)
Depends: ca-certificates, fonts-liberation, libasound2 (>= 1.0.17), libatk-bridge2.0-0 (>= 2.5.3), libatk1.0-0 (>= 2.11.90), libatspi2.0-0 (>= 2.9.90), libc6 (>= 2.25), libcairo2 (>= 1.6.0), libcups2 (>= 1.6.0), libcurl3-gnutls | libcurl3-nss | libcurl4 | libcur>
Download-Size: 140 MB
APT-Manual-Installed: yes
APT-Sources: https://dl.google.com/linux/chrome-stable/deb stable/main amd64 Packages
Description: The web browser from Google
 Google Chrome is a browser that combines a minimal design with sophisticated technology to make the web faster, safer, and easier.

[andiradulescu]

@simontheflutist yes, I read, I forgot to quote #227 (comment)