fix(nav): back from a list-opened chat returns to that list (#1400)

app/src/main/java/com/m57/hermescontrol/Navigation.kt

@@ -215,14 +215,22 @@ fun MainNavigation(sessionId: String? = null) {
     var lastBackPressTime by remember { mutableLongStateOf(0L) }
     val backToastText = stringResource(R.string.press_back_again_to_exit)
 
-    // Double-back to exit on root ChatScreen
+    // Double-back to exit on root ChatScreen — unless the chat was opened from
+    // a list (History, Bots): then the first back returns to that list (Telegram
+    // chat-list parity) and only a further double-back exits.
     BackHandler(enabled = currentScreen == ChatScreen && backStack.size == 1) {
-        val now = System.currentTimeMillis()
-        if (now - lastBackPressTime < 2000L) {
-            (context as? Activity)?.finish()
+        val pendingReturn = NavigationController.chatReturnScreen
+        if (pendingReturn != null) {
+            NavigationController.consumeChatReturnScreen()
+            NavigationController.navigateTo(pendingReturn)
         } else {
-            lastBackPressTime = now
-            Toast.makeText(context, backToastText, Toast.LENGTH_SHORT).show()
+            val now = System.currentTimeMillis()
+            if (now - lastBackPressTime < 2000L) {
+                (context as? Activity)?.finish()
+            } else {
+                lastBackPressTime = now
+                Toast.makeText(context, backToastText, Toast.LENGTH_SHORT).show()
+            }
         }
     }
 

app/src/main/java/com/m57/hermescontrol/NavigationController.kt

@@ -33,6 +33,16 @@ object NavigationController {
         private set
     var pendingNewChatNavigation: PendingNewChatNavigation? by mutableStateOf(null)
         private set
+
+    /**
+     * The list screen a chat was opened from (History, Bots). Back out of that
+     * chat returns here instead of exiting the app (Telegram chat-list parity).
+     * Consumed by MainNavigation's root-chat back handler; cleared by any other
+     * navigation so a stale target can never hijack a later back press.
+     */
+    var chatReturnScreen: NavKey? by mutableStateOf(null)
+        private set
+
     val pendingSessionId: String? get() = pendingChatNavigation?.sessionId
 
     private var nextChatNavigationRequestId = 0L
@@ -45,8 +55,18 @@ object NavigationController {
      */
     fun isPrimaryScreen(key: NavKey): Boolean = key == ChatScreen || ScreenRegistry.ALL_SCREENS.any { it.key == key }
 
+    /** Returns the armed return screen and disarms it. */
+    fun consumeChatReturnScreen(): NavKey? = chatReturnScreen.also { chatReturnScreen = null }
+
     fun navigateTo(key: NavKey) {
         val stack = backStack ?: return
+
+        // Any explicit navigation invalidates the pending chat return — only a
+        // session/chat opened from a list arms it again (see [queueChatNavigation]).
+        // This must precede the dedup guard: re-selecting Chat in the drawer is
+        // still an explicit navigation and must not keep a stale return armed.
+        chatReturnScreen = null
+
         if (stack.lastOrNull() == key) return
 
         if (key == ChatScreen) {
@@ -73,11 +93,16 @@ object NavigationController {
     }
 
     fun openChatSession(sessionId: String) {
-        queueChatNavigation(sessionId, scrollToBottom = false)
+        // Opened from a list (History cards, search results, Bots): arm the
+        // return so back from the chat lands back on that list instead of
+        // exiting the app (Telegram chat-list parity).
+        queueChatNavigation(sessionId, scrollToBottom = false, returnToList = true)
     }
 
     fun openChatSessionFromNotification(sessionId: String) {
-        queueChatNavigation(sessionId, scrollToBottom = true)
+        // A notification open is not a list navigation: back keeps the classic
+        // root-chat exit flow.
+        queueChatNavigation(sessionId, scrollToBottom = true, returnToList = false)
     }
 
     fun openNewChat() {
@@ -91,8 +116,18 @@ object NavigationController {
     private fun queueChatNavigation(
         sessionId: String,
         scrollToBottom: Boolean,
+        returnToList: Boolean,
     ) {
         if (sessionId.isBlank()) return
+        // Snapshot the origin BEFORE navigateTo resets the stack to [ChatScreen].
+        val returnScreen =
+            if (returnToList) {
+                backStack
+                    ?.lastOrNull()
+                    ?.takeIf { it != ChatScreen && isPrimaryScreen(it) }
+            } else {
+                null
+            }
         pendingChatNavigation =
             PendingChatNavigation(
                 sessionId = sessionId,
@@ -100,6 +135,8 @@ object NavigationController {
                 requestId = ++nextChatNavigationRequestId,
             )
         navigateTo(ChatScreen)
+        // Set after navigateTo so the reset itself does not disarm the return.
+        chatReturnScreen = returnScreen
     }
 
     fun consumePendingChatNavigation(): PendingChatNavigation? =
@@ -113,6 +150,7 @@ object NavigationController {
     /** Clear the stack and navigate to the given screen atomically. */
     fun resetTo(screen: NavKey) {
         val stack = backStack ?: return
+        chatReturnScreen = null
         stack.clear()
         stack.add(screen)
     }

app/src/test/java/com/m57/hermescontrol/NavigationControllerTest.kt

@@ -23,6 +23,7 @@ class NavigationControllerTest {
         NavigationController.backStack = null
         NavigationController.consumePendingSessionId()
         NavigationController.consumePendingNewChatNavigation()
+        NavigationController.consumeChatReturnScreen()
     }
 
     @After
@@ -30,6 +31,7 @@ class NavigationControllerTest {
         NavigationController.backStack = null
         NavigationController.consumePendingSessionId()
         NavigationController.consumePendingNewChatNavigation()
+        NavigationController.consumeChatReturnScreen()
     }
 
     // ── Dedup guard: navigateTo with same key ──────────────────────────────
@@ -171,6 +173,92 @@ class NavigationControllerTest {
         assertFalse(NavigationController.consumePendingChatNavigation()?.scrollToBottom == true)
     }
 
+    // ── Chat return screen: back from a list-opened chat returns to that list ──
+
+    @Test
+    fun `openChatSession from a list arms the list as the return screen`() {
+        NavigationController.backStack = NavBackStack<NavKey>(HistoryScreen)
+
+        NavigationController.openChatSession("stored-session")
+
+        assertEquals(ChatScreen, NavigationController.backStack?.lastOrNull())
+        assertEquals(HistoryScreen, NavigationController.chatReturnScreen)
+        assertEquals(HistoryScreen, NavigationController.consumeChatReturnScreen())
+        assertNull("consume must disarm", NavigationController.consumeChatReturnScreen())
+    }
+
+    @Test
+    fun `openChatSession from Bots arms Bots`() {
+        NavigationController.backStack = NavBackStack<NavKey>(BotsScreen)
+
+        NavigationController.openChatSession("bot-session")
+
+        assertEquals(BotsScreen, NavigationController.consumeChatReturnScreen())
+    }
+
+    @Test
+    fun `openChatSession from chat arms nothing`() {
+        NavigationController.backStack = NavBackStack<NavKey>(ChatScreen)
+
+        NavigationController.openChatSession("stored-session")
+
+        assertNull(NavigationController.consumeChatReturnScreen())
+    }
+
+    @Test
+    fun `notification open never arms a return screen`() {
+        NavigationController.backStack = NavBackStack<NavKey>(HistoryScreen)
+
+        NavigationController.openChatSessionFromNotification("stored-session")
+
+        assertEquals(ChatScreen, NavigationController.backStack?.lastOrNull())
+        assertNull(NavigationController.consumeChatReturnScreen())
+    }
+
+    @Test
+    fun `drawer navigation disarms a stale return screen`() {
+        NavigationController.backStack = NavBackStack<NavKey>(HistoryScreen)
+        NavigationController.openChatSession("stored-session")
+        assertEquals(HistoryScreen, NavigationController.chatReturnScreen)
+
+        // User opens the drawer and picks Skills instead of pressing back.
+        NavigationController.navigateTo(SkillsScreen)
+
+        assertNull("explicit navigation must invalidate the return", NavigationController.consumeChatReturnScreen())
+    }
+
+    @Test
+    fun `re-tapping chat in the drawer also disarms the return`() {
+        NavigationController.backStack = NavBackStack<NavKey>(HistoryScreen)
+        NavigationController.openChatSession("stored-session")
+        assertEquals(HistoryScreen, NavigationController.chatReturnScreen)
+
+        // Same-screen dedup would skip the body — the clear must still run.
+        NavigationController.navigateTo(ChatScreen)
+
+        assertNull(NavigationController.consumeChatReturnScreen())
+    }
+
+    @Test
+    fun `openNewChat does not arm a return screen`() {
+        NavigationController.backStack = NavBackStack<NavKey>(HistoryScreen)
+
+        NavigationController.openNewChat()
+
+        assertNull(NavigationController.consumeChatReturnScreen())
+    }
+
+    @Test
+    fun `resetTo disarms the return screen`() {
+        NavigationController.backStack = NavBackStack<NavKey>(HistoryScreen)
+        NavigationController.openChatSession("stored-session")
+        assertEquals(HistoryScreen, NavigationController.chatReturnScreen)
+
+        NavigationController.resetTo(ChatScreen)
+
+        assertNull(NavigationController.consumeChatReturnScreen())
+    }
+
     // ── resetTo: atomic clear + navigate ──────────────────────────────────
 
     @Test