How do I tell Safari not to change the active tab on the error console when I reload a page?

Close the Resources tab then it always stays on the tab where you are on every reload

Usually I open the developer tools by using the "Inspect Element" context menu, and get the same behaviour as you describe (automatically switching to the Resource tab).

So I experimented and found an answer: If you open the developer tools to the Console tab by selecting Develop > Show Error Console from the menu, it will stay on the Console tab after a page refresh.

Also, if you open the developer tools using the "Toggle Web Inspector" icon or the Develop > Show Web Inspector menu item, it will stay on whatever tab you have selected after a page refresh.