Flutter windowing API — Linux X11 GLX BadAccess minimal repro

Minimal reproduction for flutter/flutter#186577: a single RegularWindowController construction under --enable-windowing crashes on Linux X11 + AMD Radeon (Mesa 26.1) with GLX BadAccess (error_code 10, minor_code 26) → "Lost connection to device".

The entire app is lib/main.dart (17 lines).

Reproduce

flutter channel main && flutter upgrade   # if not already on main
flutter config --enable-windowing         # one-time, global
flutter pub get
flutter run -d linux

Expected: window opens with the word "hello" centered.

Actual:

GLib-GObject-CRITICAL: invalid (NULL) pointer instance
GLib-GObject-CRITICAL: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
Gdk-WARNING: The program received an X Window System error.
  The error was 'BadAccess (attempt to access private resource denied)'.
  (Details: error_code 10 request_code 152 (GLX) minor_code 26)
Lost connection to device.

Triangulation on the same machine + SDK

App	--enable-windowing	Result
Stock flutter create (no windowing API used)	no	runs cleanly
This 17-line RegularWindowController app	yes	crashes
Flutter's own examples/multiple_windows	yes	crashes verbatim

So one RegularWindowController() construction is sufficient to trip the bug. The regular Linux renderer works fine on this stack; this is windowing-API-specific.

Environment

• Flutter main, 3.44.0-1.0.pre-557 (framework 0541913d86, engine 3e4e8b379e)
• CachyOS, kernel 7.0.5-2-cachyos
• X11 (XDG_SESSION_TYPE=x11)
• AMD Radeon Graphics (renoir, radeonsi), Mesa 26.1.0-arch2.1

Full triangulation, flutter doctor -v, and discussion in flutter/flutter#186577.