[chris-addison]

Claudistopher:

A Metal driver that refuses to build the renderer now returns an error from open_window instead of panicking. Found in the native Unity Hub: Sentry issue UNITY-HUB-37DK shows Hub 4.0.0-beta.2 dying at startup on an Intel MacBookAir5,1 (macOS 26.7.2) with "Compiler encountered an internal error".

• Before: MetalRenderer::new was infallible. A refused MSL compile panicked with "error building metal library", a missing entry point with "error locating …", a refused pipeline with "could not create render pipeline state", and a missing Metal device called std::process::exit(1). new_renderer already returned a Result, but it could only ever be Ok.
• Now: MetalRenderer::new, new_headless and MetalHeadlessRenderer::new return Result<_, MetalRendererError>. The error carries the device name, the step that failed (for example "compiling the quads shader library") and Metal's own message. new_renderer passes it up through open_window, so an application can report it and exit. gpui_platform re-exports the type on macOS, so callers can downcast_ref it without depending on gpui_apple.
• current_headless_renderer keeps panicking when Metal fails, the same way the WGPU headless renderer does on the other platforms. It is test and bench support only.

No fallback renderer: the macOS wgpu renderer is a compile-time feature, not a runtime choice, and it runs Naga's MSL through the same driver compiler, so it would most likely fail the same way.

Testing

Two new tests in metal_renderer::tests run on a real Metal device, like the existing ones (the test-mac CI job runs them):

• a_shader_library_the_device_refuses_is_an_error hands the device an invalid source for the quads shader and checks that construction returns an error naming the device, the step and the compiler's text.
• a_missing_shader_entry_point_is_an_error checks the entry-point lookup the same way.

Locally on an Apple Silicon Mac: cargo test -p gpui_ce_apple --lib passes (15 tests), and clippy with -D warnings is clean on gpui_ce_apple, gpui_ce_platform and gpui_ce_macos (all targets).

A second commit fixes CI that was already broken on unity/hub-consolidated: renderer_source_audit::windows_default_renderer_has_no_wgpu_path failed on every platform, because it required gpui_windows/Cargo.toml to never mention gpui_wgpu, while the branch carries an optional, non-default wgpu feature for the per-window WGPU renderer. The audit now allows gpui_wgpu only as an optional dependency that the wgpu feature enables, fails when default or any other feature turns it on, and checks that a build without the feature creates the DirectX renderer. Adding wgpu to default, or dropping optional = true, makes it fail again (checked locally). default is ["gpui/default"] today.

This branch is unity/hub-consolidated (the Hub's current pin, 02e408c456) plus these two commits.

🤖 Generated with Claude Code