Tk 8.7 will be compatible with both Tcl 8.7 and Tcl 9.0; there is no Tk 9.0 currently in development. The version and/or patchlevel of Tcl and Tk will not necessarily be identical, but there are places in Tkinter code which assume they are. A few examples which I am aware of:

Linked PRs

• gh-104496: IDLE - fix About for mixed tcl/tk versions #104585
• [3.11] gh-104496: IDLE - fix About for mixed tcl/tk versions (GH-104585) #104587
• gh-104496: Use correct Tcl or Tk version in Tkinter tests #107688
• [3.12] gh-104496: Use correct Tcl or Tk version in Tkinter tests (GH-107688) #107709
• [3.11] gh-104496: Use correct Tcl or Tk version in Tkinter tests (GH-107688) #107719