Iris Shaders Crash: Missing sampler Sampler1 in GlCommandEncoder

What the log looks like

java\.lang\.IllegalStateException: Missing sampler Sampler1
Missing sampler Sampler1[\s\S]{0,160}com\.mojang\.blaze3d\.opengl\.GlCommandEncoder\.trySetup

How to fix it

1. Update Iris Shaders and Sodium to the newest release for your Minecraft 26.1+ version, as this crash is caused by an injection-order bug in Iris versions 1.10.9 through 1.11.4.
2. If no fixed Iris build is available yet, turn off shaders before loading into the world by pressing K on the title screen or setting enableShaders=false inside config/iris.properties.
3. If you are playing on NeoForge (or running a modded development environment) where OpenGL validation is active, add -Dneoforge.disableGlValidation=true to your launcher's JVM arguments to skip the strict sampler check so Iris's fallback texture binding can run.
4. If the crash only triggers with a specific PBR shader pack such as BSL or Complementary Unbound, open Shader Pack Settings and disable PBR / normal-map materials until Iris is updated.

Check your own log