VK_EXT_primitive_restart_index allows for setting a custom primitive restart index and designed to help support OpenGL emulation atop the Vulkan API. VK_EXT_primitive_restart_index was developed by Mike Blumenkrantz of Valve's Linux graphics team. Blumenkrantz notably is one of the lead developers of Mesa's Zink driver for generic OpenGL-on-Vulkan. The primitive restart index extension was merged as part of Vulkan 1.4.348 at the start of the month.
RADV is now the first Mesa Vulkan driver supporting VK_EXT_primitive_restart_index for helping with future Zink usage.
Samuel Pitoiset of Valve's Linux graphics team took care of the implementation. It landed for Mesa 26.1 via this merge .
Separately and still under review are also primitive restart index implementations for Lavapipe and the Intel ANV driver .