Reproduction steps:

1. Open https://vscode.dev/github/microsoft/vscode

2. Open a file and use command Split Editor Right

3. Look carefully at the dividing line of tab on the right.
   

4. The browser method can observe that the width of the border line is inconsistent when the first tab of the editor and the second tab are activated.
   
   

Version: 1.87.2
Commit: 863d258
User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36
Embedder: vscode.dev