diff --git a/docs/TROUBLESHOOTING.md b/docs/TROUBLESHOOTING.md
index 7d8b3f4..3075637 100644
--- a/docs/TROUBLESHOOTING.md
+++ b/docs/TROUBLESHOOTING.md
@@ -348,6 +348,27 @@ with sway/Xwayland using CPU readback. The initial polling change improved their
 reported rate from about 20 to 27 FPS. Those observations predate the narrowed
 integration; they do not establish hybrid-GPU or general NVIDIA support.
 
+### NVIDIA 580 (Pascal and older): black game window
+
+Driver 580 is the last branch for Pascal (GTX 10-series) and older GPUs. With
+`__GL_THREADED_OPTIMIZATIONS=1`, this driver with egl-x11 1.0.6 rejects the X11
+`EGLDisplay` with `EGL_BAD_DISPLAY` on every thread that has a context current.
+The display stays valid on other threads, and `eglReleaseThread()` makes it work
+again on the failing one. A small native EGL program outside Darling shows the
+same: `eglQueryString(display, EGL_VENDOR)` after `eglMakeCurrent` returns
+`NVIDIA` without the variable and fails with `EGL_BAD_DISPLAY` with it.
+
+In the Riot client the main thread loses EGL right after its first window frame;
+`CGLCreateContext` then fails with CGL error 10004 and, if another display is
+opened, glvnd hands it to Mesa's software renderer, which cannot present the
+game's NVIDIA Vulkan frames. The launcher therefore leaves threaded optimizations
+off (`__GL_THREADED_OPTIMIZATIONS=0`). Setting the variable to `1` before launch
+restores the old behaviour.
+
+Tested on a GTX 1060 6GB with driver 580.178.04 on NixOS, Hyprland and Xwayland:
+the client and the tutorial match render on the NVIDIA GPU. Newer drivers were not
+retested with the option off.
+
 ### Host-side checks
 
 These are host settings, not game settings. Run on AC power, and use a performance power profile (`powerprofilesctl set performance`, or `asusctl profile -P Performance` on ASUS laptops). On the tested desktop the game is limited mostly by its own main thread on the CPU, not by the GPU (see [status](STATUS.md#game-fps-2026-10-1314)), so laptop CPU power limits matter as much as the GPU choice.
diff --git a/patches/darling.patch b/patches/darling.patch
index 66477f9..49e767f 100644
--- a/patches/darling.patch
+++ b/patches/darling.patch
@@ -6257,7 +6257,7 @@ index deca16b87..d75d5e22d 100644
  
  set_property(TARGET OpenGL APPEND_STRING PROPERTY LINK_FLAGS
 diff --git a/src/frameworks/OpenGL/OpenGL.c b/src/frameworks/OpenGL/OpenGL.c
-index ffd7fe054..1ff212d34 100644
+index ffd7fe054..5b5712ea2 100644
 --- a/src/frameworks/OpenGL/OpenGL.c
 +++ b/src/frameworks/OpenGL/OpenGL.c
 @@ -2,11 +2,22 @@
@@ -6527,11 +6527,14 @@ index ffd7fe054..1ff212d34 100644
  
      if (surface == EGL_NO_SURFACE) {
          return NULL;
-@@ -171,14 +309,18 @@ CGLWindowRef CGLGetWindow(void *native_window) {
+@@ -171,14 +309,21 @@ CGLWindowRef CGLGetWindow(void *native_window) {
  }
  
  CGL_EXPORT void CGLDestroyWindow(CGLWindowRef window) {
 -    eglDestroySurface(display, (EGLSurface) window);
++    /* CGLGetWindow returns NULL when eglCreateWindowSurface fails. */
++    if (window == NULL)
++        return;
 +    p_eglDestroySurface(display, (EGLSurface) window);
  }
  
@@ -6548,7 +6551,7 @@ index ffd7fe054..1ff212d34 100644
  }
  
  static pthread_key_t current_context_key;
-@@ -198,18 +340,42 @@ CGLContextObj CGLGetCurrentContext(void) {
+@@ -198,18 +343,42 @@ CGLContextObj CGLGetCurrentContext(void) {
      return pthread_getspecific(key);
  }
  
@@ -6596,7 +6599,7 @@ index ffd7fe054..1ff212d34 100644
  }
  
  CGLError CGLSetFullScreen(CGLContextObj ctx) {
-@@ -223,11 +389,13 @@ CGLError CGLChoosePixelFormat(
+@@ -223,11 +392,13 @@ CGLError CGLChoosePixelFormat(
      CGLPixelFormatObj *result,
      GLint *number_of_screens
  ) {
@@ -6611,7 +6614,7 @@ index ffd7fe054..1ff212d34 100644
      for (int i = 0; i < count; i++) {
          format->attributes[i] = attrs[i];
      }
-@@ -251,6 +419,10 @@ CGLError CGLDescribePixelFormat(
+@@ -251,6 +422,10 @@ CGLError CGLDescribePixelFormat(
      CGLPixelFormatAttribute attr,
      GLint *value
  ) {
@@ -6622,7 +6625,7 @@ index ffd7fe054..1ff212d34 100644
      for (int i = 0; format->attributes[i] != 0; i++) {
          int has_arg = attribute_has_argument(format->attributes[i]);
  
-@@ -304,24 +476,67 @@ GLuint CGLGetPixelFormatRetainCount(CGLPixelFormatObj pixelFormat) {
+@@ -304,24 +479,67 @@ GLuint CGLGetPixelFormatRetainCount(CGLPixelFormatObj pixelFormat) {
  }
  
  CGLError CGLCreateContext(CGLPixelFormatObj pixelFormat, CGLContextObj share, CGLContextObj *resultp) {
@@ -6691,7 +6694,7 @@ index ffd7fe054..1ff212d34 100644
  
      *resultp = context;
  
-@@ -333,7 +548,7 @@ CGLContextObj CGLRetainContext(CGLContextObj context) {
+@@ -333,7 +551,7 @@ CGLContextObj CGLRetainContext(CGLContextObj context) {
          return NULL;
      }
  
@@ -6700,7 +6703,7 @@ index ffd7fe054..1ff212d34 100644
      return context;
  }
  
-@@ -342,11 +557,17 @@ void CGLReleaseContext(CGLContextObj context) {
+@@ -342,11 +560,17 @@ void CGLReleaseContext(CGLContextObj context) {
          return;
      }
  
@@ -6721,7 +6724,7 @@ index ffd7fe054..1ff212d34 100644
  
      if (CGLGetCurrentContext() == context) {
          CGLSetCurrentContext(NULL);
-@@ -354,7 +575,11 @@ void CGLReleaseContext(CGLContextObj context) {
+@@ -354,7 +578,11 @@ void CGLReleaseContext(CGLContextObj context) {
  
      pthread_mutex_destroy(&(context->lock));
  
@@ -6734,7 +6737,7 @@ index ffd7fe054..1ff212d34 100644
  
      free(context);
  }
-@@ -383,9 +608,330 @@ CGLError CGLUnlockContext(CGLContextObj context) {
+@@ -383,9 +611,330 @@ CGLError CGLUnlockContext(CGLContextObj context) {
      return kCGLNoError;
  }
  
@@ -7067,7 +7070,7 @@ index ffd7fe054..1ff212d34 100644
  }
  
  CGLError CGLSetParameter(CGLContextObj context, CGLContextParameter parameter, const GLint *value) {
-@@ -394,8 +940,9 @@ CGLError CGLSetParameter(CGLContextObj context, CGLContextParameter parameter, c
+@@ -394,8 +943,9 @@ CGLError CGLSetParameter(CGLContextObj context, CGLContextParameter parameter, c
  
      if (parameter == kCGLCPSwapInterval)
      {
@@ -7078,7 +7081,7 @@ index ffd7fe054..1ff212d34 100644
          if (success)
              context->swap_interval = v;
          return success ? kCGLNoError : kCGLBadValue;
-@@ -417,14 +964,19 @@ CGLError CGLGetParameter(CGLContextObj context, CGLContextParameter parameter, G
+@@ -417,14 +967,19 @@ CGLError CGLGetParameter(CGLContextObj context, CGLContextParameter parameter, G
      return kCGLNoError;
  }
  
diff --git a/tools/run-riot-client.sh b/tools/run-riot-client.sh
index 75b6ec7..94ea1be 100755
--- a/tools/run-riot-client.sh
+++ b/tools/run-riot-client.sh
@@ -92,7 +92,10 @@ if [ -n "${RCLOL_REFRESH_HZ-}" ]; then export RCLOL_REFRESH_HZ; fi
 export MESA_NO_ERROR="${MESA_NO_ERROR:-1}"
 # NVIDIA proprietary driver: limit pre-rendered frames.
 export __GL_MaxFramesAllowed="${__GL_MaxFramesAllowed:-1}"
-export __GL_THREADED_OPTIMIZATIONS="${__GL_THREADED_OPTIMIZATIONS:-1}"
+# Threaded optimizations stay off: with them, NVIDIA 580 (the last branch for
+# Pascal GPUs) with egl-x11 1.0.6 rejects the X11 EGLDisplay with EGL_BAD_DISPLAY
+# on every thread that has a context current, and the game window stays black.
+export __GL_THREADED_OPTIMIZATIONS="${__GL_THREADED_OPTIMIZATIONS:-0}"
 export __GL_YIELD="${__GL_YIELD:-NOTHING}"
 # Reduce timer slack for tighter scheduling in the game process tree.
 if [ -w /proc/self/timerslack_ns ]; then