[🐛 Bug]: SE_NODE_STEREOTYPE_EXTRA not merged into config.toml in Docker Hub-Node mode

[Tiamoz01]

Description

I’m running Selenium Grid Hub in WSL and starting a Chrome Node container with the following command:·

docker run -d \
  -e SE_EVENT_BUS_HOST=<event_bus_ip_or_name> \
  -e SE_NODE_STEREOTYPE_EXTRA='{"myApp:version":"beta","myApp:publish":"public"}' \
  --shm-size="2g" \
  selenium/node-chrome:4.35.0-20250909

Problem:

The environment variable SE_NODE_STEREOTYPE_EXTRA is not automatically merged into config.toml.

As a result, the Node's stereotype does not include the custom attributes, and I cannot target a specific Node in my tests using myApp:version.

I tried a workaround by mounting a custom config.toml into the Node container and starting the Node with:

java -jar /opt/selenium/selenium-server.jar node --config /opt/selenium/config.toml

This successfully overrides the Node stereotype.

However, when I specify options.set_capability('myApp:version', 'beta') in the client, the Node container logs an exception:

Exception managing chrome: Unable to discover proper chromedriver version in offline mode

Request / Question:

Is there a supported way to:

Add custom stereotype attributes to a Node using Docker Hub-Node mode (so SE_NODE_STEREOTYPE_EXTRA works correctly), and

Avoid issues with ChromeDriver version detection when using these custom capabilities?

This would allow targeting specific Nodes for automated tests without breaking ChromeDriver integration.

Reproducible Code

Start Selenium Hub:

docker run -d -p 4442-4444:4442-4444 --name selenium-hub selenium/hub:4.35.0-20250909


Start Node with custom stereotype:

docker run -d \
  --link selenium-hub:hub \
  -e SE_EVENT_BUS_HOST=selenium-hub \
  -e SE_NODE_STEREOTYPE_EXTRA='{"myApp:version":"beta"}' \
  --shm-size="2g" \
  selenium/node-chrome:4.35.0-20250909


Run a Selenium client targeting myApp:version:

from selenium import webdriver
from selenium.webdriver import ChromeOptions

options = ChromeOptions()
options.set_capability("myApp:version", "beta")
driver = webdriver.Remote(
    command_executor="http://localhost:4444",
    options=options
)


Actual Result:

Node does not recognize myApp:version.

Using a mounted config.toml triggers ChromeDriver version detection errors.

Environment:

Selenium 4.35.0-20250909

Docker Desktop on WSL2

Python 3.12

---

ℹ️ Last known working version: 4.8.0

[selenium-ci]

@Tiamoz01, thank you for creating this issue. We will troubleshoot it as soon as we can.

Selenium Triage Team: remember to follow the Triage Guide

[VietND96]

Looks like a regression issue after introducing node-all-browsers recently. I can reproduce with following logs

Backing up original environment variables...

Backed up original SE_NODE_BROWSER_VERSION=stable to SE_NODE_BROWSER_VERSION_ORIGINAL

Backed up original SE_NODE_PLATFORM_NAME=Linux to SE_NODE_PLATFORM_NAME_ORIGINAL

Backed up original SE_NODE_STEREOTYPE_EXTRA={\"myApp:version\":\"beta\",\"myApp:publish\":\"public\"} to SE_NODE_STEREOTYPE_EXTRA_ORIGINAL

Backed up original SE_NODE_MAX_SESSIONS=1 to SE_NODE_MAX_SESSIONS_ORIGINAL

===Start generating stereotype for browser: CHROME===

Inherited original SE_NODE_BROWSER_VERSION_ORIGINAL=stable to SE_NODE_BROWSER_VERSION

Inherited original SE_NODE_PLATFORM_NAME_ORIGINAL=Linux to SE_NODE_PLATFORM_NAME

Inherited original SE_NODE_STEREOTYPE_EXTRA_ORIGINAL={"myApp:version":"beta","myApp:publish":"public"} to SE_NODE_STEREOTYPE_EXTRA

Inherited original SE_NODE_MAX_SESSIONS_ORIGINAL=1 to SE_NODE_MAX_SESSIONS

Merging SE_NODE_STEREOTYPE_EXTRA={myApp:version:beta,myApp:publish:public} to main stereotype for CHROME

Failed to merge SE_NODE_STEREOTYPE_EXTRA for CHROME. Please check the format of the JSON string. Keep using main stereotype.

JSON format is broken due to missing quote characters, will fix it soon