Mesa 26.0.0‑rc2 is the second release candidate for the upcoming 26.0.0 series, and it finally patches the nasty nvk crash that occurs when an unbound descriptor set contains a dynamic buffer. The radv video driver now computes tile sizes more reliably, while panvk’s sparse image handling respects non‑opaque bind flags, fixing the “image not found” errors some of us saw on Vulkan experiments. A few regressions remain – the PVR driver temporarily disables the buffer device address extension and enabling ZPASS_PIXEL_COUNT can shave a few frames off older NVIDIA GPUs.

Mesa 26.0.0 Release Candidate 2: What’s Fixed, What Still Bites, and How to Try It

The second release candidate of Mesa 26.0.0 landed this week, bringing a handful of driver tweaks that actually matter for everyday gaming and graphics work. In this article you’ll see which regressions were squashed, where the new bugs are hiding, and how to give the RC a spin without breaking your whole desktop.

Quick rundown – why bother with an RC?

If you live on the bleeding‑edge of Linux graphics (think Vulkan‑only titles, Wayland compositors, or GPU compute experiments), Mesa’s release candidates are the only way to see fixes before they get baked into your distro. The “rc2” label means the developers have already ironed out a few obvious crashes from rc1 and feel confident enough to push another test build. It also tells you there’s still at least one more candidate coming, so don’t treat this as the final word.

What actually changed?

• nvk driver – The NVIDIA Vulkan driver now tolerates unbound descriptor sets that contain dynamic buffers.
• radv/video – Tile‑size calculation is more reliable, which fixes occasional video playback stutter on AMD GPUs.
• panvk – Sparse image binding now respects non‑opaque flags, ending a weird “image not found” error.
• aco optimizer – Several parser quirks around the SALU p_insert opcode were corrected. If you’ve ever gotten “invalid instruction” errors compiling shaders for newer AMD cards, this should cut down on those noise messages.
• freedreno – The gen8 EFU float control fix removes a handful of floating‑point precision warnings that showed up in Android GPU Inspector.

There are dozens more tiny patches (mostly typo fixes or warning silences), but the list above hits the most visible parts of the stack.

Known rough edges

• ZPASS_PIXEL_COUNT – The nvk driver now enables this counter, which is great for profiling, but on a few older GPUs it re‑introduces a minor performance dip during heavy occlusion queries. If you notice FPS drops in a Vulkan benchmark after enabling the flag, turn it off in your app’s debug settings.
• Transient images in Zink – The patch lets you blit with temporary images again, yet I’ve seen a rare “invalid memory access” on Intel Xe2+ when the driver tries to recycle those buffers too quickly. Keep an eye on the dmesg output if you’re pushing frame‑rate limits.
• Buffer device address extension – The PVR driver temporarily disables this feature. Applications that rely on GPU‑side pointer arithmetic (e.g., some compute shaders) will fall back to a slower path.

How to test rc2 without blowing up your system

1. Back up your current Mesa packages. On Arch you can pacman -Qi mesa and note the version, then copy the package files from /var/cache/pacman/pkg. This way you can roll back with a single pacman -U <old‑pkg> if something goes sideways.

2. Pull the rc2 tarball

   wget https://mesa.freedesktop.org/archive/mesa-26.0.0-rc2.tar.xz
   tar xf mesa-26.0.0-rc2.tar.xz
   cd mesa-26.0.0-rc2
   

   Using the official tarball guarantees you’re testing exactly what the developers posted, not a distro‑modified snapshot.

3. Configure with the drivers you care about.

   meson setup build \
   -Dprefix=/usr/local \
   -Ddri-drivers=auto \
   -Dvulkan-drivers=auto \
   -Degl=true \
   -Dgallium-omx=disabled
   

   Enabling only the drivers you need reduces compile time and eliminates unrelated regressions.

4. Compile and install.

   ninja -C build
   sudo ninja -C build install
   

   The sudo step overwrites the system libraries, so after a reboot your X/Wayland session will pick up the new Mesa.

5. Validate with a known workload.
   Run something like vulkaninfo | grep driverVersion to confirm the version string shows “26.0.0‑rc2”. Then launch a Vulkan game you own and watch for crashes or visual glitches. If you hit a problem, file it at the Mesa issue tracker with the exact log snippet – the developers still need concrete reports before the final release.

Should you stick to rc2?

If your daily driver is stable and you don’t need any of the fixes listed above, stay on the distro’s current Mesa version. The RC series is great for early adopters but can still bring regressions that haven’t been fully vetted across all hardware combos.

On the other hand, if you’ve already been tripping over an nvk binding crash or radv video stutter, give rc2 a spin – the patches are small enough to revert if needed, and you’ll be ahead of the curve when 26.0.0 ships.

Happy testing, and may your shaders compile on the first try!