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Snapshot setup on macOS fails with misleading 'Could not set up the GNOME extension' (osascript test-capture failure)#18595

openedOct 12, 2026byJjerome-marshall-ntx

What happened

Setting up Snapshots locally on macOS fails at step 1 Access with:

Couldn't finish this step. Try again or check Advanced for help. Error invoking remote method 'desktop:setup-snap-shot': DesktopSnapShotSetupError: Could not set up the GNOME extension.

Screenshots (from reporter, to be attached): SCR-20261012-mutk.png (Set up snapshots dialog, Screen Recording Allowed, Accessibility Allowed, red error + Advanced text) and SCR-20261012-mzss.png (Local environment LWX5WD4KCC, local server).

macOS permissions are both Allowed, so this is not a TCC-denied permission row. The host is local macOS, not Linux/GNOME.

Environment

Actual cause (from logs)

~/.t3/userdata/logs/desktop.trace.ndjson, span desktop.snapShot.setup / desktop.ipc.method channel desktop:setup-snap-shot:

  • Outer: DesktopSnapShotSetupError: Could not set up the GNOME extension. (thrown from apps/desktop/dist-electron/main.cjs)
  • Inner: UnknownError: An error occurred in Effect.tryPromise
  • Root: Error: Command failed: /usr/bin/osascript -l JavaScript -e ObjC.import("CoreGraphics"); ObjC.import("AppKit"); function run() { const app = $.NSWorkspace.sharedWorkspace.frontmostApplication; ... $.CGWindowListCopyWindowInfo($.kCGWindowListOptionOnScreenOnly | $.kCGWindowListExcludeDesktopElements, ...) ... }

So on macOS the failing step is the JXA/osascript frontmost-window test capture ("Test a snapshot of the current window"), mis-reported with the Linux/GNOME error string.

I ran the same osascript by hand and it succeeds (exit 0), so the script itself is fine; the spawn from inside the Nightly Electron main process fails.

Expected

  1. On macOS, a failing osascript test-capture should report a macOS-specific error (and stderr), not "Could not set up the GNOME extension."
  2. Snapshot setup should succeed when Screen Recording + Accessibility are Allowed, or say exactly which app bundle (T3 Code vs T3 Code Nightly vs Helper Renderer) is missing which permission.

Repro

  1. On macOS with T3 Code Nightly, open Settings > SnapShots, turn on.
  2. Step 1 Access shows Screen Recording Allowed, Accessibility Allowed.
  3. Click Test capture and continue -> red "Couldn't finish this step", Advanced shows the GNOME-extension error above.

Notes

  • No Linux/GNOME host involved (flux: reporter first suspected fleet Linux machines machine0/machine01, but settings show local Mac server).
  • Happy to attach the two screenshots and a redacted trace excerpt on request; the screenshots didn't transfer to this filing session so adding them separately.
JJulius MarmingeOct 12, 2026

Note

Grok responding on behalf of Julius.

The error message is a real bug, confirmed on main. The capture failure underneath it is most likely a permissions setup issue.

Wrong message (bug): in apps/desktop/src/snapShot/DesktopSnapShot.ts, the test-mac-capture action maps every failure to DesktopSnapShotSetupError({ reason: "setup-failed" }). DesktopSnapShotSetupError.message only has wording for KDE and Hyprland, so every other action gets "Could not set up the GNOME extension." That includes the macOS test capture. The macOS case needs its own message, and it should pass through the osascript stderr.

Capture failure (likely setup): you said the same script works from your terminal. That points to TCC: macOS grants permissions to each bundle separately. You have both T3 Code and T3 Code (Nightly) installed, so the Allowed rows may belong to the other bundle. Workaround: in System Settings → Privacy & Security, remove both T3 Code entries under Screen Recording and under Accessibility, then quit Nightly, relaunch it, and grant both permissions again.

If capture still fails after that, please post the stderr from the osascript error in desktop.trace.ndjson, redacted as needed.