Host: keyboard layout read on the main thread; a call cut off mid-action is unknown (#244)

native2/Sources/DesktopMac/System.swift

@@ -58,11 +58,13 @@ extension Mac {
 			NSWorkspace.shared.runningApplications.contains { $0.bundleIdentifier == "com.apple.ScreenSaver.Engine" }
 		}
 
-		var layout: JSON?
-		if let source = TISCopyCurrentKeyboardLayoutInputSource()?.takeRetainedValue(),
-		   let id = tisString(source, kTISPropertyInputSourceID)
-		{
-			layout = .object(["id": JSON(id), "name": tisString(source, kTISPropertyLocalizedName).map(JSON.string)])
+		// Text Input Sources must be read on the main thread: off it, HIToolbox can trap on a queue assertion and take
+		// the host down mid-call, which agents saw as "host closed the connection" after a desktop_open (#244).
+		let layout = await MainActor.run { () -> JSON? in
+			guard let source = TISCopyCurrentKeyboardLayoutInputSource()?.takeRetainedValue(),
+			      let id = tisString(source, kTISPropertyInputSourceID)
+			else { return nil }
+			return .object(["id": JSON(id), "name": tisString(source, kTISPropertyLocalizedName).map(JSON.string)])
 		}
 		let pointer = CGEvent(source: nil).map(\.location).map { point -> JSON in
 			.object(["x": JSON(Double(point.x)), "y": JSON(Double(point.y)), "display_index": WindowPlaces().pointerDisplay(point).map { JSON($0) }])

native2/Sources/desktop-tools-mcp/main.swift

@@ -203,7 +203,22 @@ func call(_ key: String, tool: String, arguments: JSON) async -> JSON {
 		if case .system("connect", _) = error {
 			return errorResult("The Desktop Tools 2 host isn't serving at \(socketPath). Start it with: native2/.build/debug/desktop-tools-host")
 		}
-		return errorResult(error.description)
+		// The request may have reached the host, which can stop or restart mid-call. An action may then have taken
+		// effect, as a desktop_open whose host stopped after Xcode opened the file did (#244), so it is unknown, never
+		// a plain error an agent reads as "nothing happened".
+		if Contract.actions.contains(tool) {
+			let action: JSON = .object([("action", .object([
+				("outcome", "unknown"), ("action", JSON(tool)), ("retry_safety", "unsafe"),
+				("error", .object([("code", "HOST_CONNECTION_LOST"), ("message", JSON(
+					"\(error.description) The Desktop Tools host stopped while running \(tool), so it may have taken effect. "
+						+ "Observe the target (desktop_windows, desktop_inspect) before deciding whether to act again; don't repeat it blindly."))])),
+			]))])
+			return .object([
+				("content", [.object([("type", "text"), ("text", "Outcome: unknown.")]), .object([("type", "text"), ("text", JSON(action.text))])]),
+				("isError", true),
+			])
+		}
+		return errorResult("\(error.description) Nothing was changed by this read; call it again.")
 	} catch {
 		return errorResult(String(describing: error))
 	}