@@ -40,8 +40,9 @@ final class RunnerTests: XCTestCase {
   /// discloses dispatched: no.
   /// `ALERT_UNRESOLVED` means required alert acquisition failed or exhausted its deadline.
   /// It establishes no absence and activates nothing, so dispatched: no.
-  /// `BACK_SWIPE_NO_CHANGE` is a back swipe that left the app's screen unchanged, and
-  /// `BACK_SWIPE_UNVERIFIED` one whose screen could not be sampled afterwards. Both ran the swipe.
+  /// `BACK_SWIPE_NO_CHANGE` is a back swipe that left the app's screen unchanged.
+  /// `BACK_SWIPE_UNVERIFIED` is one whose screen kept changing on its own before the swipe, or could
+  /// not be sampled afterwards. Both ran the swipe.
   enum RunnerWireErrorCode {
     static let mainThreadTimeout = "MAIN_THREAD_TIMEOUT"
     static let appNotRunning = "APP_NOT_RUNNING"
 
@@ -66,12 +66,13 @@ extension RunnerTests {
   @MainActor
   func testInAppBackOnAnUnreadableTreeVerifiesTheSwipeOnTheSoleScreen() throws {
     let status = try launchBackFixture(["--agent-device-back-regression"])
+    // Terminates whichever fixture instance is running when the test leaves, on every path.
+    defer { endBackFixture() }
     let answered = try withRejectedAppTree(framesReadable: false) { try performInAppBack(app: app) }
     let soleScreenOpen = soleScreenRouteIsOpen(for: app)
     let answeredLabel = status.label
     endBackFixture()
     _ = try launchBackFixture([])
-    defer { endBackFixture() }
     let ignored = try withRejectedAppTree(framesReadable: false) { try performInAppBack(app: app) }
 
     guard soleScreenOpen else {
 
@@ -286,7 +286,7 @@ export const SYSTEM_COMMAND_OUTPUT_SCHEMAS = {
 const appStateCommandDescription =
   'Show foreground app/activity (Android and HarmonyOS; iOS and macOS answer per session)';
 const backCommandDescription =
-  'Navigate back in the app or through system navigation. Use in-app for the app navigation stack and system when the platform back behavior is required. On iOS both modes swipe from the left edge and succeed only when the app screen changes; an unchanged screen refuses with reason back_swipe_no_change. An app with a left-edge drawer may open the drawer instead. Press a visible back or close control by its ref directly.';
+  'Navigate back in the app or through system navigation. Use in-app for the app navigation stack and system when the platform back behavior is required. On iOS both modes swipe from the left edge and succeed only when the app screen changes. Reason back_swipe_no_change: the swipe was sent and the screen did not change; press the visible back or close control. Reason back_swipe_unverified: the swipe may or may not have navigated, because the screen kept changing before it or could not be sampled after it; check with snapshot. When the screen cannot be sampled before the swipe, back does not swipe. An app with a left-edge drawer may open the drawer instead. Press a visible back or close control by its ref directly.';
 const homeCommandDescription =
   'Send the selected device to its home screen. This leaves the app session open but moves the foreground away from the app.';
 const orientationCommandDescription =
 
@@ -124,7 +124,10 @@ iOS Simulator launch behavior:
 Back, orientation, and hardware buttons:
 
 - `back` uses app-owned back navigation: the back keyevent on Android, the visible back control on macOS, and the Siri Remote Menu button on tvOS. `--in-app` names this default explicitly.
-- On iOS, `back` is the left-edge back swipe, with or without `--in-app` or `--system`. It succeeds only when the app's screen changes. An unchanged screen refuses with `reason: back_swipe_no_change`. It waits up to about a second for the screen to stop changing before it swipes. If the screen keeps changing on its own, or cannot be sampled after the swipe, the result is an unknown outcome (`back_swipe_unverified`). If the screen cannot be sampled before the swipe, `back` does not swipe.
+- On iOS, `back` is the left-edge back swipe, with or without `--in-app` or `--system`. It succeeds only when the app's screen changes. It waits up to about a second for the screen to stop changing before it swipes.
+- `reason: back_swipe_no_change`: the swipe was sent and the screen did not change. Press the visible back or close control.
+- `reason: back_swipe_unverified`: the swipe may or may not have navigated, because the screen kept changing before the swipe or could not be sampled after it. Check with `snapshot`.
+- If the screen cannot be sampled before the swipe, `back` does not swipe.
 - An app with a left-edge drawer may open the drawer instead of going back. When a back or close control is visible, press it by its ref.
 - `back --system` sends system back input: the Android back keyevent, the iOS back swipe, or the tvOS Siri Remote Menu button. macOS has no system back, so it refuses before dispatch.
 - `orientation portrait|portrait-upside-down|landscape-left|landscape-right` works on iOS and Android mobile targets only. On ADB-backed Android it turns auto-rotate off, and the lock persists after the session ends until something turns it back on. A foldable iPhone simulator (iPhone Duo) refuses `portrait-upside-down`, and refuses every rotation in a scoped simulator set (`--ios-simulator-device-set`).