SnapShot shortcut cannot capture Xcode Device Hub on macOS 27

What happened

On macOS 27, with a simulator open in Xcode's Device Hub, invoking the configured T3 Code SnapShot shortcut consistently fails with “Snapshot failed — The active window is not available for capture.” The reporter supplied a screenshot of the error.

Diagnosis

The desktop trace records DesktopSnapShotError during desktop.snapShot.prepareCapture, before macOS capture starts. In the installed revision, captureSource throws window-unavailable when activeWindow() returns no window. The macOS lookup takes NSWorkspace.frontmostApplication.processIdentifier and searches the on-screen CoreGraphics window list for a layer-0 window with that owner PID.

A read-only OS probe while Device Hub was frontmost returned Device Hub with PID -1 from NSWorkspace, while CoreGraphics listed its visible layer-0 window under PID 35409. That PID belonged to Xcode's DeviceHub executable. The mismatched PIDs explain why the lookup returns no window. The cause of macOS reporting PID -1 for Device Hub has not been determined.

Steps to reproduce

1. Open a simulator in Xcode 27's Device Hub on macOS 27.
2. Bring Device Hub to the foreground and invoke the configured T3 Code SnapShot shortcut.
3. Observe “Snapshot failed — The active window is not available for capture.” The reporter says this happens consistently.

Version

T3 Code Nightly 0.0.43-nightly.20260916.1811 (ccf220be205f0e509021dbc8cbda90daa638e20d).

Environment

macOS 27.0 (build 26A428), Apple Silicon (arm64); Xcode 27.0 (build 27A266a); T3 Code desktop app. The t3 triage CLI ran under Node v26.8.2.

Evidence

2026-09-16 10:52:50 -05:00  desktop.snapShot.prepareCapture  Failure
DesktopSnapShotError: The active window is not available for capture.
  at captureSource (.../apps/desktop/dist-electron/main.cjs:97112:23)

NSWorkspace frontmost application: Device Hub, PID -1
CoreGraphics on-screen layer-0 window: Device Hub, owner PID 35409
PID 35409 executable: /Applications/Xcode.app/Contents/Applications/DeviceHub.app/Contents/MacOS/DeviceHub

Related issues

No matching issue found. #11713 also mentions Device Hub but concerns simulator installation detection, not SnapShot capture.

Fix applied or workaround

No T3 Code fix applied. A manual macOS window screenshot can be attached to the T3 Code composer as a workaround.

Filed by

Codex (Astra) via t3 triage.

Start at desktop.snapShot.prepareCapture and inspect captureSource and activeWindow in apps/desktop/dist-electron/main.cjs, where the trace shows the failure. Reproduce with Xcode Device Hub frontmost and compare the NSWorkspace PID with the CoreGraphics owner PID. Done means the configured SnapShot shortcut captures Device Hub instead of reporting that the active window is unavailable.