diff --git a/apps/lightcraft/src/main.rs b/apps/lightcraft/src/main.rs
index 00665e87..94aeefa1 100644
--- a/apps/lightcraft/src/main.rs
+++ b/apps/lightcraft/src/main.rs
@@ -98,6 +98,8 @@ fn window_wgpu_options() -> eframe::egui_wgpu::WgpuConfiguration {
     if let eframe::egui_wgpu::WgpuSetup::CreateNew(n) = &mut c.wgpu_setup {
         n.instance_descriptor.backends = lightcraft_engine::gpu::backend::window_backends();
         n.instance_descriptor.backend_options = lightcraft_engine::gpu::backend::backend_options();
+        // no indirect-call validation pipeline: Intel Metal fails to compile it and the window never opens (#250)
+        n.instance_descriptor.flags = lightcraft_engine::gpu::backend::instance_flags_from_env(n.instance_descriptor.flags);
     }
     c
 }
@@ -999,6 +1001,16 @@ mod tests {
         }
     }
 
+    /// Issue #250: the window's device is created without wgpu's indirect-call validation pipeline,
+    /// which Intel Macs' Metal compiler fails to build (the device was lost, the window never opened).
+    #[test]
+    fn window_has_no_indirect_call_validation_pipeline() {
+        let eframe::egui_wgpu::WgpuSetup::CreateNew(n) = window_wgpu_options().wgpu_setup else { panic!("expected CreateNew") };
+        if std::env::var_os("WGPU_VALIDATION_INDIRECT_CALL").is_none() {
+            assert!(!n.instance_descriptor.flags.contains(eframe::wgpu::InstanceFlags::VALIDATION_INDIRECT_CALL));
+        }
+    }
+
     /// Issue #234: Windows opens links with the URL protocol handler (the default browser), not
     /// File Explorer, and passes the whole map link, `?`, `&` and `#` included, as one argument.
     #[test]
diff --git a/crates/gpu/src/backend.rs b/crates/gpu/src/backend.rs
index 041f5773..81bfe719 100644
--- a/crates/gpu/src/backend.rs
+++ b/crates/gpu/src/backend.rs
@@ -145,6 +145,25 @@ pub fn backend_options() -> wgpu::BackendOptions {
     o
 }
 
+/// wgpu's instance flags for every instance LightCraft creates, from `flags` (wgpu's defaults with its
+/// environment variables applied) without `VALIDATION_INDIRECT_CALL`, unless
+/// `WGPU_VALIDATION_INDIRECT_CALL` asks for it (any value but `0`). That validation builds an internal
+/// compute pipeline when each device is created; Intel Macs' Metal compiler fails on it ("Compiler
+/// encountered an internal error"), the device is lost and the window never opens (#250). It only
+/// guards indirect draws and dispatches, which neither LightCraft nor egui issue.
+pub fn instance_flags(flags: wgpu::InstanceFlags, env: Option<&str>) -> wgpu::InstanceFlags {
+    if env.is_some_and(|v| v != "0") {
+        flags | wgpu::InstanceFlags::VALIDATION_INDIRECT_CALL
+    } else {
+        flags - wgpu::InstanceFlags::VALIDATION_INDIRECT_CALL
+    }
+}
+
+/// [`instance_flags`] with `WGPU_VALIDATION_INDIRECT_CALL` read from the environment.
+pub fn instance_flags_from_env(flags: wgpu::InstanceFlags) -> wgpu::InstanceFlags {
+    instance_flags(flags, std::env::var("WGPU_VALIDATION_INDIRECT_CALL").ok().as_deref())
+}
+
 /// `LIGHTCRAFT_GPU_BACKEND=off`.
 pub(crate) fn env_off() -> bool {
     env_choice() == BackendChoice::Off
@@ -195,6 +214,17 @@ pub fn read_init_marker(path: &std::path::Path) -> Option<String> {
 #[cfg(test)]
 #[allow(clippy::unwrap_used)]
 mod tests {
+
+    /// #250: the indirect-call validation pipeline is off unless asked for; other flags are kept.
+    #[test]
+    fn indirect_call_validation_is_off_unless_asked_for() {
+        use wgpu::InstanceFlags as F;
+        let base = F::VALIDATION_INDIRECT_CALL | F::DEBUG;
+        assert_eq!(instance_flags(base, None), F::DEBUG);
+        assert_eq!(instance_flags(base, Some("0")), F::DEBUG);
+        assert_eq!(instance_flags(F::empty(), Some("1")), F::VALIDATION_INDIRECT_CALL);
+        assert_eq!(instance_flags(F::empty(), None), F::empty());
+    }
     use super::*;
 
     #[test]
diff --git a/crates/gpu/src/ctx.rs b/crates/gpu/src/ctx.rs
index 2f4abd4d..8d73703c 100644
--- a/crates/gpu/src/ctx.rs
+++ b/crates/gpu/src/ctx.rs
@@ -284,6 +284,8 @@ impl Gpu {
         desc.backends = backends;
         // DX12 shaders compile with FXC (issue #471)
         desc.backend_options = crate::backend::backend_options();
+        // no indirect-call validation pipeline: Intel Metal fails to compile it (#250)
+        desc.flags = crate::backend::instance_flags_from_env(desc.flags);
         let instance = wgpu::Instance::new(desc);
         let adapter = pollster::block_on(
             instance.request_adapter(&wgpu::RequestAdapterOptions { power_preference: wgpu::PowerPreference::HighPerformance, ..Default::default() }),
diff --git a/crates/gpu/src/nn.rs b/crates/gpu/src/nn.rs
index 689aecbe..ca0975e9 100644
--- a/crates/gpu/src/nn.rs
+++ b/crates/gpu/src/nn.rs
@@ -86,6 +86,8 @@ fn make_device(backends: wgpu::Backends) -> Result<Dev, String> {
     desc.backends = backends;
     // DX12 shaders compile with FXC (issue #471)
     desc.backend_options = crate::backend::backend_options();
+    // no indirect-call validation pipeline: Intel Metal fails to compile it (#250)
+    desc.flags = crate::backend::instance_flags_from_env(desc.flags);
     let instance = wgpu::Instance::new(desc);
     let wanted = std::env::var("LIGHTCRAFT_GPU_ADAPTER").ok().map(|s| s.trim().to_lowercase()).filter(|s| !s.is_empty());
     let adapter = match &wanted {