WebdriverIO v9 Migration Issues: Shadow DOM selectors, scoping regression & severe flakiness vs v8

I migrated a large test suite from WebdriverIO v8 → v9 and ran into multiple regressions that make v9 unusable for our shadow-DOM-heavy application.

Key issues:

1. Shadow DOM selectors frequently fail

Errors like:

WebDriverError: Failed to execute 'evaluate' on 'XPathExpression':

The node provided is '#document-fragment'

Dropdowns inside shadow roots fail to open ~55% of the time.

2. Element scoping broken

In v8:

JavaScriptcard.$('.button') // correct scoping``Show more lines

In v9, the same code returns elements from all matching containers.

This causes wrong-click issues when multiple cards exist.

3. Element staleness

In v9, elements become stale after any state update, requiring:

• frequent re-fetching
• retry loops
• multiple pauses

This adds complexity and slows tests down.

4. Performance regression

Tests become 30–40% slower

Some interactions now take 3–4 seconds vs. 200–300ms in v8

Workarounds add 20+ lines per test section

Question:

Are these known issues with v9's BiDi implementation?

Is shadow DOM currently expected to be unstable in v9?

Is the recommended approach to stay on v8 for shadow-DOM-heavy applications until v9 matures?

Any guidance from WDIO team or other teams who migrated would help.