Removing:

const onColumnResized = (params) => {
    params.api.resetRowHeights();
  }

in the new version seems to solve the issue and works properly.
But, am not sure if it has some other consequences.

Anyways should be described in breaking changes if this is expected.

Hi,

Your ticket has been flagged as in_zendesk, it means that we recognize this as an issue worth investigating so we have moved it to our official support channel for customers (zendesk)

We will carry on there with the investigation and we will update you as soon as possible.

Thanks

Hi @croraf!

Thank you for reporting this - much appreciated.

The row auto-height rendering logic was changed in AG Grid v26.0 as part of:
AG-5607 Enhance Row Auto Height Support

As part of this change row height changes are detected by the grid which refreshes the rows automatically without having to call gridApi.resetRowHeights() in the onColumnResized event handler as before. Actually keeping the calls
to gridApi.resetRowHeights() causes rows to render twice, producing the flicker you reported.

This information was logged as part of MORE INFORMATION but not as a breaking change - thank you for noticing this omission. I've now corrected this and updated the to log this information specifically as a BREAKING CHANGE.

I'm including this information below for full context:
The row auto-height behavior has been changed. When a column uses auto height (colDef.autoHeight=true), there is no need to call gridApi.resetRowHeights() in the onColumnResized event handler anymore to force the rows to update their row height after a column resize operation, as the grid will automatically resize the rows when it detects a height change.

From v26.0 onward, keeping these calls to gridApi.resetRowHeights() causes flicker as rows render themselves twice instead of once. Please remove calls to gridApi.resetRowHeights() in onColumnResized event handler to avoid flicker in row re-rendering.

Thanks for reporting this - we appreciate your time!

Great!