feat: open a conversation on its first unread message, under a "New" line

Both UIs: a channel, DM or room with unread messages opens on the oldest of
them (MessageHistory::firstUnreadChannel / firstUnreadDm, own messages not
counted), a "New" line above it, so it reads down to the newest. Nothing
unread: the newest, as before.

L1: the first unread is selected and scrolled up top with the line in view;
the channel's unread count now counts down as you read towards the newest.
L2: the page holding it, scrolled to the line; an incoming message scrolls
down only when the list is already at its end. Sim hooks: sim_unread (L1),
sim_open("unread") (L2).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

examples/companion_radio/ui-core/MessageHistory.h

@@ -413,6 +413,31 @@ public:
     return -1;
   }
 
+  // Where reading resumes on opening a conversation with `unread` unread: the
+  // newest-first index (as histEntryForChannel / dmHistEntryForContact) of the
+  // oldest of the `unread` newest received messages -- our own don't count --
+  // or of the oldest held when some were pushed out. -1 when none is unread.
+  int firstUnreadChannel(int ch_idx, int unread) const {
+    int j = 0, last = -1;
+    for (int i = _hist_count - 1; i >= 0 && unread > 0; i--) {
+      const ChHistEntry& e = _hist[(_hist_head + i) % CH_HIST_MAX];
+      if (e.ch_idx != (uint8_t)ch_idx) continue;
+      last = j++;
+      if (strncmp(e.text, "Me: ", 4) != 0) unread--;
+    }
+    return last;
+  }
+  int firstUnreadDm(const uint8_t* prefix, int unread) const {
+    int j = 0, last = -1;
+    for (int i = _dm_hist_count - 1; i >= 0 && unread > 0; i--) {
+      const DmHistEntry& e = _dm_hist[(_dm_hist_head + i) % DM_HIST_MAX];
+      if (memcmp(e.prefix, prefix, 4) != 0) continue;
+      last = j++;
+      if (!e.outgoing) unread--;
+    }
+    return last;
+  }
+
   // Effective status for display. A pending ACK only reads as failed once its
   // deadline has passed AND no auto-resends remain — while resends_left > 0 the
   // entry stays pending (tickDmResends() retries / finalises it). Safety net for

examples/companion_radio/ui-core/UiCore.h

@@ -224,6 +224,28 @@ public:
     if (viewing && pos >= 0) _host->onViewedHistoryGrew(true);
     return pos;
   }
+#ifdef SIM_PLATFORM
+  // Sim tests: channel 0 and the first chat contact get 12 read messages, then 5 new.
+  void simUnreadDemo() {
+    uint32_t now = rtc_clock.getCurrentTime();
+    static const char* const W[] = { "Alice", "Bob", "Me", "Carol" };
+    const uint8_t* dm = nullptr;
+    ContactInfo c;
+    for (int i = 0; i < the_mesh.getNumContacts() && !dm; i++)
+      if (the_mesh.getContactByIdx(MAX_ANON_CONTACTS + i, c) && c.type == ADV_TYPE_CHAT) dm = c.id.pub_key;
+    for (int i = 0; i < 17; i++) {
+      char t[48];
+      snprintf(t, sizeof(t), "%s: message %d", i < 12 ? W[i % 4] : W[i % 2], i + 1);
+      addChannelMsg(0, t, now - (17 - i) * 120);
+      if (dm) {
+        bool out = i < 12 && i % 3 == 2;
+        if (!out) dm_unread.onIncoming(dm);
+        addDMMsg(dm, out, strstr(t, ": ") + 2, now - (17 - i) * 120);
+      }
+      if (i == 11) { history.setChUnread(0, 0); if (dm) clearDMUnread(dm); }
+    }
+  }
+#endif
   void armChannelRelay(int pos, uint32_t seq) override { history.armChannelRelay(pos, seq); }
   void onChannelRelayed(uint32_t seq, const uint8_t* repeater_hash = nullptr, uint8_t hash_size = 0) override {
     history.markChannelRelayed(seq, repeater_hash, hash_size);

examples/companion_radio/ui-lvgl/UITask.cpp

@@ -3620,22 +3620,33 @@ void UITask::setKeyboardVisible(bool show) {
   }
 }
 
+static const int THREAD_MAX_SHOWN = 50;   // newest bubbles built per conversation
+
+// Opens on the first unread (newest-first index `first`, -1: none), "New"
+// above it: the page that holds it, a few read ones above.
+void UITask::threadOpenAt(int first) {
+  _thread_new = first;
+  _thread_new_on = false;
+  _thread_skip = first < THREAD_MAX_SHOWN ? 0 : first - (THREAD_MAX_SHOWN - 4);
+}
+
 void UITask::openChannel(uint8_t channel_idx) {
   _thread_is_channel = true;
   _thread_channel = channel_idx;
-  _thread_skip = 0;
-  _core->history.setChUnread(channel_idx, 0);
+  MessageHistory& h = _core->history;
+  threadOpenAt(h.firstUnreadChannel(channel_idx, h.chUnread(channel_idx)));
+  h.setChUnread(channel_idx, 0);
   _screen = SCR_THREAD;
   buildThread();
 }
 
 void UITask::openDM(const uint8_t* pub_key) {
   _thread_is_channel = false;
-  _thread_skip = 0;
   memset(_thread_key, 0, sizeof(_thread_key));
   ContactInfo c;
   if (MessageHistory::contactByPrefix(pub_key, c)) memcpy(_thread_key, c.id.pub_key, PUB_KEY_SIZE);
   else memcpy(_thread_key, pub_key, 4);
+  threadOpenAt(_core->history.firstUnreadDm(_thread_key, _core->dmUnread(_thread_key)));
   _core->clearDMUnread(_thread_key);
   _screen = SCR_THREAD;
   buildThread();
@@ -3742,7 +3753,6 @@ uint32_t UITask::threadSignature() const {
 // Positions found in the shown messages ([WAY] / [LOC] / plain "lat,lon"),
 // for the Go / Save buttons under such a bubble.
 struct MsgLoc { int32_t lat, lon; char label[WAYPOINT_LABEL_LEN * 2]; };
-static const int THREAD_MAX_SHOWN = 50;   // newest bubbles built per conversation
 static MsgLoc* s_msg_locs = psramBuf<MsgLoc>(THREAD_MAX_SHOWN);
 static int    s_msg_loc_n = 0;
 
@@ -3765,6 +3775,28 @@ struct ThreadRow { uint32_t key, state; lv_obj_t* row; lv_obj_t* age; };
 static ThreadRow* s_th_rows = psramBuf<ThreadRow>(THREAD_MAX_SHOWN);
 static lv_obj_t* s_older_lbl = nullptr;   // "Older messages (n)" on the page's top
 static bool      s_th_rows_newest = false;   // built for the newest page (the one patched)
+static lv_obj_t* s_new_div = nullptr;   // "New" above the first unread
+
+// The line with "New" over the first message unread when the thread opened.
+static lv_obj_t* newDivider(lv_obj_t* list) {
+  lv_obj_t* d = lv_obj_create(list);
+  lv_obj_remove_style_all(d);
+  lv_obj_set_size(d, LV_PCT(100), LV_SIZE_CONTENT);
+  lv_obj_set_flex_flow(d, LV_FLEX_FLOW_ROW);
+  lv_obj_set_flex_align(d, LV_FLEX_ALIGN_CENTER, LV_FLEX_ALIGN_CENTER, LV_FLEX_ALIGN_CENTER);
+  lv_obj_set_style_pad_column(d, 6, 0);
+  lv_obj_remove_flag(d, LV_OBJ_FLAG_CLICKABLE);
+  for (int i = 0; i < 3; i++) {
+    if (i == 1) { label(d, "New", THEME_FONT_SMALL, theme::ACCENT); continue; }
+    lv_obj_t* l = lv_obj_create(d);
+    lv_obj_remove_style_all(l);
+    lv_obj_set_height(l, 1);
+    lv_obj_set_flex_grow(l, 1);
+    lv_obj_set_style_bg_color(l, lv_color_hex(theme::ACCENT), 0);
+    lv_obj_set_style_bg_opa(l, LV_OPA_COVER, 0);
+  }
+  return d;
+}
 
 // The shown message a bubble (or a button in it) belongs to, or -1.
 static int threadRowOf(lv_obj_t* o) {
@@ -4134,7 +4166,11 @@ void UITask::refreshThread() {
     drop--;
   }
   if (kept > 0) {
-    for (int r = 0; r < drop; r++) lv_obj_delete(s_th_rows[r].row);
+    bool at_end = lv_obj_get_scroll_bottom(_thread_list) <= theme::PAD;   // not when reading further up
+    for (int r = 0; r < drop; r++) {
+      if (s_new_div && s_th_rows[r].key == _thread_new_key) { lv_obj_delete(s_new_div); s_new_div = nullptr; }
+      lv_obj_delete(s_th_rows[r].row);
+    }
     memmove(s_th_rows, s_th_rows + drop, kept * sizeof(ThreadRow));
     memmove(s_msg_meta, s_msg_meta + drop, kept * sizeof(MsgMeta));
     for (int r = 0; r < kept; r++) {
@@ -4155,7 +4191,7 @@ void UITask::refreshThread() {
     for (int r = kept; r < n; r++) build(r);
     if (s_older_lbl) { char t[40]; olderText(t, sizeof(t)); setText(s_older_lbl, t); }
     s_th_rows_n = s_msg_meta_n = s_msg_loc_n = n;
-    if (n > kept) {   // new messages: down to them
+    if (n > kept && at_end) {   // new messages: down to them
       layoutNow(_thread_list);
       lv_obj_scroll_to_y(_thread_list, LV_COORD_MAX, LV_ANIM_OFF);
     }
@@ -4171,13 +4207,20 @@ void UITask::refreshThread() {
     pageButton(_thread_list, t, 1);
     s_older_lbl = lv_obj_get_child(lv_obj_get_child(_thread_list, -1), 0);
   }
-  for (int i = 0; i < n; i++) build(i);   // oldest first
+  s_new_div = nullptr;
+  for (int i = 0; i < n; i++) {   // oldest first
+    if (_thread_new >= 0 && _thread_skip + n - 1 - i == _thread_new) { _thread_new_key = keyOf(i); _thread_new_on = true; }
+    if (_thread_new_on && !s_new_div && keyOf(i) == _thread_new_key && (i > 0 || s_older_lbl)) s_new_div = newDivider(_thread_list);
+    build(i);
+  }
+  _thread_new = -1;
   s_th_rows_n = s_msg_meta_n = s_msg_loc_n = n;
   s_th_rows_newest = _thread_skip == 0;   // a page back is built whole each time
   if (_thread_skip > 0) pageButton(_thread_list, LV_SYMBOL_DOWN "  Newer messages", -1);
   if (n == 0) label(_thread_list, "No messages yet", THEME_FONT_BODY, theme::TEXT_MUTED);
   layoutNow(_thread_list);
   lv_obj_scroll_to_y(_thread_list, _thread_scroll_top ? 0 : LV_COORD_MAX, LV_ANIM_OFF);
+  if (s_new_div && !_thread_scroll_top) lv_obj_scroll_to_view(s_new_div, LV_ANIM_OFF);   // from the bottom: "New" on top
   _thread_scroll_top = false;
 }
 
@@ -4673,6 +4716,11 @@ void UITask::simDm() {
   }
 }
 
+void UITask::simUnread() {
+  _core->simUnreadDemo();
+  if (_screen == SCR_CHATS) refreshChats();
+}
+
 // Sim tests: straight to a screen by name.
 extern "C" EMSCRIPTEN_KEEPALIVE void sim_open(const char* name) {
   if (!s_ui) return;
@@ -4697,6 +4745,7 @@ extern "C" EMSCRIPTEN_KEEPALIVE void sim_open(const char* name) {
   if (!strncmp(name, "compose@", 8)) { s_ui->simCompose(name + 8); return; }
   if (!strcmp(name, "dm")) { s_ui->simDm(); return; }
   if (!strcmp(name, "send")) { s_ui->simSend(); return; }
+  if (!strcmp(name, "unread")) { s_ui->simUnread(); return; }
   if (!strcmp(name, "vector")) { s_ui->setVectorMap(true); return; }
   if (!strcmp(name, "maptools")) { s_ui->navToolsPopup(); return; }
   if (!strcmp(name, "areasel")) { s_ui->areaSelectBegin(); return; }

examples/companion_radio/ui-lvgl/UITask.h

@@ -130,6 +130,7 @@ public:
   void simMapAt(const char* spec);      // Map tools > Live tiles
   void simCompose(const char* text);    // the open thread's field: this text, keyboard up
   void simDm();                         // the first chat contact's thread
+  void simUnread();                     // read and new messages to open on
   void simSend() { sendFromCompose(); } // the field, sent
   // Navigation map (NavMap.h)
   void navTargetsPopup();
@@ -425,6 +426,7 @@ private:
   void buildNode();
   void refreshNode();
   void buildThread();
+  void threadOpenAt(int first);
   void refreshThread();
   void refreshThreadAges();
   uint32_t threadSignature() const;
@@ -539,6 +541,9 @@ private:
   bool     _thread_is_channel = false;
   int      _thread_skip = 0;          // newest messages above the page shown (Older / Newer)
   bool     _thread_scroll_top = false;
+  int      _thread_new = -1;          // on opening: newest-first index of the first unread (-1: none)
+  uint32_t _thread_new_key = 0;       // and that message, marked with "New" while the thread is open
+  bool     _thread_new_on = false;
   int      loadThreadPage(int& total);
   uint8_t  _thread_channel = 0;
   uint8_t  _thread_key[PUB_KEY_SIZE] = {0};

examples/companion_radio/ui-new/MessagesScreen.h

@@ -47,7 +47,8 @@ class MessagesScreen : public UIScreen {
   int _hist_sel, _hist_scroll;
   FullscreenMsgView _fs;
   int  _unread_at_entry;    // channel unread count when entering CHANNEL_HIST
-  int  _viewing_max_seen;  // highest _hist_sel reached in current session
+  int  _unread_base = 0;    // messages filed since: the unread are indices base.. base+count-1
+  int  _seen_lo = 0, _seen_hi = -1;   // the indices shown so far this session
 
   // KEYBOARD
   KeyboardWidget* _kb;
@@ -143,6 +144,11 @@ class MessagesScreen : public UIScreen {
   int _dm_hist_sel, _dm_hist_scroll;
   FullscreenMsgView _dm_fs;
 
+  // "New" over the first message unread when the conversation opened (index
+  // as _hist_sel / _dm_hist_sel, -1: none); the first render scrolls it up top.
+  int  _new_idx = -1;
+  bool _anchor_new = false;
+
   int _hist_visible = 2;  // updated in render(); for history list scroll clamping
 
   void expandMsg(const char* tmpl, char* out, int out_len) const {   // ui-core/MessageText.h
@@ -681,7 +687,6 @@ class MessagesScreen : public UIScreen {
       // Filed at index 0 by sendText(): the unread index range is stale, and
       // the user is active in this channel -- fully read.
       _unread_at_entry = 0;
-      _viewing_max_seen = 0;
     } else {
       _dm_hist_sel = 0;
       _dm_hist_scroll = 0;
@@ -969,7 +974,7 @@ public:
       _sel_channel_idx(0), _sending_to_channel(false),
       _msg_sel(0), _msg_scroll(0), _active_msg_count(0),
       _hist_sel(0), _hist_scroll(0),
-      _unread_at_entry(0), _viewing_max_seen(0),
+      _unread_at_entry(0),
       _history(task->core().history),
       _dm_hist_sel(-1), _dm_hist_scroll(0),
       _ctx_dirty(false), _pin_picker_active(false), _direct_entry(false), _reply_mode(false),
@@ -1003,8 +1008,14 @@ public:
     return _phase == DM_HIST && memcmp(_sel_contact.id.pub_key, pub_key, 4) == 0;
   }
   void onViewedHistoryGrew(bool channel) {
-    if (channel) { if (_hist_sel > 0)    { _hist_sel++; _hist_scroll++; } }
-    else         { if (_dm_hist_sel > 0) { _dm_hist_sel++; _dm_hist_scroll++; } }
+    if (channel) {
+      if (_hist_sel > 0) { _hist_sel++; _hist_scroll++; }
+      _unread_base++;
+      if (_seen_hi >= 0) { _seen_lo++; _seen_hi++; }
+    } else {
+      if (_dm_hist_sel > 0) { _dm_hist_sel++; _dm_hist_scroll++; }
+    }
+    if (_new_idx >= 0) _new_idx++;
   }
 
   // Room logins (who is logged in this session, the saved passwords, the one
@@ -1037,11 +1048,56 @@ public:
   // the scroll/selection view state. Shared by the Enter-on-contact path and the
   // post-login auto-enter.
   void openDmHistory() {
-    _task->clearDMUnread(_sel_contact.id.pub_key);
-    _dm_hist_sel = -1;
+    beginDmView();
+    _phase = DM_HIST;
+  }
+
+  // Opening a conversation: on its first unread message ("New" above it), else
+  // on the compose row under the newest.
+  void beginDmView() {
+    const uint8_t* key = _sel_contact.id.pub_key;
+    _new_idx = _history.firstUnreadDm(key, _task->getDMUnread(key));
+    _anchor_new = _new_idx >= 0;
+    _task->clearDMUnread(key);
+    _dm_hist_sel = _new_idx;
     _dm_hist_scroll = 0;
     _dm_fs.active = false;
-    _phase = DM_HIST;
+  }
+  void beginChannelView(uint8_t channel_idx) {
+    _sel_channel_idx = channel_idx;
+    _unread_at_entry = (int)_history.chUnread(channel_idx);
+    _unread_base = 0;
+    _seen_lo = 0; _seen_hi = -1;
+    _new_idx = _history.firstUnreadChannel(channel_idx, _unread_at_entry);
+    _anchor_new = _new_idx >= 0;
+    _hist_scroll = 0;
+    _hist_sel = _new_idx >= 0 ? _new_idx : _history.histCountForChannel(channel_idx) > 0 ? 0 : -1;
+    _fs.active = false;
+  }
+
+  // On the first unread (sel), opening: the scroll showing it highest with
+  // "New" above it (stack(s) lays out from s, sets div_y when "New" fits).
+  template <class Stack> static int anchorScroll(Stack stack, const int& div_y, int sel, int count) {
+    int pick = -1;
+    for (int s = sel > 8 ? sel - 8 : 0; s <= sel; s++) {
+      int n = stack(s);
+      if (s + n - 1 < sel) continue;
+      if (div_y >= 0 || sel + 1 >= count) return s;
+      if (pick < 0) pick = s;
+    }
+    return pick >= 0 ? pick : sel;
+  }
+
+  // "New" between two lines, lh tall, over the first message unread on opening.
+  static void drawNewDivider(DisplayDriver& d, int y, int w, int lh) {
+    const char* t = "New";
+    int tw = d.getTextWidth(t);
+    int tx = (w - tw) / 2, mid = y + lh / 2;
+    d.setColor(DisplayDriver::LIGHT);
+    d.fillRect(1, mid, tx - 4, 1);
+    d.fillRect(tx + tw + 3, mid, w - 1 - (tx + tw + 3), 1);
+    d.setCursor(tx, y + 1);
+    d.print(t);
   }
 
 
@@ -1070,15 +1126,21 @@ public:
   // "what has the user seen on screen" logic is pure phase-machine state.
   void updateChannelUnread() {
     if (_sel_channel_idx < 0 || _sel_channel_idx >= MAX_GROUP_CHANNELS) return;
-    // histEntryForChannel is newest-first: index 0 = newest (unread), higher = older.
-    // Count everything actually rendered on screen as seen — not just the
-    // highlighted row — so a taller screen that fits more boxes at once marks
-    // more read up front, instead of requiring a press per row.
-    int seen_to = _hist_scroll + _hist_visible - 1;
-    if (_hist_sel > seen_to) seen_to = _hist_sel;
-    if (seen_to > _viewing_max_seen) _viewing_max_seen = seen_to;
-    // Each step down from 0 sees one more message; seen count = max_seen + 1.
-    int remaining = _unread_at_entry - (_viewing_max_seen + 1);
+    // histEntryForChannel is newest-first: index 0 = newest, higher = older;
+    // the unread from opening are _unread_base onwards. Count everything
+    // actually rendered on screen as seen — not just the highlighted row — so
+    // a taller screen that fits more boxes at once marks more read up front,
+    // instead of requiring a press per row. Reading starts at the first unread
+    // and goes down to the newest, so what's been shown is one stretch.
+    int lo = _hist_scroll, hi = _hist_scroll + _hist_visible - 1;
+    if (_hist_sel >= 0 && _hist_sel < lo) lo = _hist_sel;
+    if (_hist_sel > hi) hi = _hist_sel;
+    if (_seen_hi < 0 || lo < _seen_lo) _seen_lo = lo;
+    if (hi > _seen_hi) _seen_hi = hi;
+    int a = _seen_lo > _unread_base ? _seen_lo : _unread_base;
+    int b = _unread_base + _unread_at_entry - 1;
+    if (_seen_hi < b) b = _seen_hi;
+    int remaining = _unread_at_entry - (b >= a ? b - a + 1 : 0);
     _history.setChUnread(_sel_channel_idx, (uint8_t)(remaining > 0 ? remaining : 0));
   }
 
@@ -1109,7 +1171,8 @@ public:
     _pick_fav_slot = -1;
     _direct_entry = false;
     _unread_at_entry = 0;
-    _viewing_max_seen = 0;
+    _new_idx = -1;
+    _anchor_new = false;
     _ch_view.reset();
     _ch_view_pending_rebuild = false;
   }
@@ -1235,10 +1298,7 @@ public:
 
   void enterDM(const ContactInfo& ci) {
     _sel_contact = ci;
-    _task->clearDMUnread(ci.id.pub_key);
-    _dm_hist_sel = -1;
-    _dm_hist_scroll = 0;
-    _dm_fs.active = false;
+    beginDmView();
     _room_mode = false;
     _phase = DM_HIST;
     _direct_entry = true;
@@ -1249,10 +1309,7 @@ public:
   // to. Caller must have already reset() the screen.
   void enterRoom(const ContactInfo& ci) {
     _sel_contact = ci;
-    _task->clearDMUnread(ci.id.pub_key);
-    _dm_hist_sel = -1;
-    _dm_hist_scroll = 0;
-    _dm_fs.active = false;
+    beginDmView();
     _room_mode = true;
     _phase = DM_HIST;
     _direct_entry = true;
@@ -1262,12 +1319,7 @@ public:
   // Open a channel's history directly (used by the Favourites dial). Caller
   // must have already reset() the screen.
   void enterChannel(uint8_t channel_idx) {
-    _sel_channel_idx = channel_idx;
-    _unread_at_entry = (int)_history.chUnread(channel_idx);
-    _hist_scroll = 0;
-    _hist_sel = _history.histCountForChannel(channel_idx) > 0 ? 0 : -1;
-    _viewing_max_seen = _hist_sel >= 0 ? _hist_sel : 0;
-    _fs.active = false;
+    beginChannelView(channel_idx);
     _phase = CHANNEL_HIST;
     _direct_entry = true;
   }
@@ -1503,7 +1555,8 @@ public:
       // Fixed-track scrollbar metrics + a stable gutter reserve (decided by a
       // whole-list fit test, not last frame's visible count) so message boxes
       // don't reflow their width as messages arrive.
-      HistScroll hs = compact_dm
+      auto scrollMetrics = [&]() {
+        return compact_dm
           ? computeHistScrollH(display, dm_count, _dm_hist_scroll, hist_start_y, cby, 1, compactH)
           : computeHistScroll(display, expand, dm_count, _dm_hist_scroll,
           hist_start_y, cby, lh,
@@ -1514,20 +1567,24 @@ public:
             char tmp_sender[33];
             return bodyAt(idx, tmp_sender, sizeof(tmp_sender));
           });
+      };
+      HistScroll hs = scrollMetrics();
       int reserve = hs.reserve;
-      {
-        // Stack boxes upward from just above the compose row, so item 0 (the
-        // newest message) lands at the bottom of the list and older messages
-        // sit progressively higher — same anchor convention as a typical
-        // messenger, instead of newest-at-top. box_ys[i] still corresponds
-        // to item (_dm_hist_scroll + i), same as before; only its y flips.
+      int div_y = -1;   // "New", when shown
+      // Stack boxes upward from just above the compose row, so item 0 (the
+      // newest message) lands at the bottom of the list and older messages
+      // sit progressively higher — same anchor convention as a typical
+      // messenger, instead of newest-at-top. box_ys[i] still corresponds
+      // to item (s + i), same as before; only its y flips.
+      auto stack = [&](int s) {
         const int fixed_bh = 2 * lh + 1;
         const int box_gap = expand ? 2 : 1;
         int cur_y = cby - box_gap;   // reserve the same gap against compose as between boxes
-        for (int ii = 0; ii < MAX_VIS_BOXES && (_dm_hist_scroll + ii) < dm_count; ii++) {
-          int bh = compact_dm ? compactH(_dm_hist_scroll + ii, reserve) : fixed_bh;
+        n_vis = 0; div_y = -1;
+        for (int ii = 0; ii < MAX_VIS_BOXES && (s + ii) < dm_count; ii++) {
+          int bh = compact_dm ? compactH(s + ii, reserve) : fixed_bh;
           if (expand) {
-            int rp = _history.dmHistEntryForContact(_sel_contact.id.pub_key, _dm_hist_scroll + ii);
+            int rp = _history.dmHistEntryForContact(_sel_contact.id.pub_key, s + ii);
             if (rp >= 0) {
               char hsb[33];
               const char* hbody = skipReplyPrefix(dmDisplayParts(_history.dmAtPos(rp), is_room, filtered_name, hsb, sizeof(hsb)));
@@ -1538,8 +1595,20 @@ public:
           if (box_top < hist_start_y) break;
           box_ys[n_vis] = box_top; box_hs[n_vis] = bh; n_vis++;
           cur_y = box_top - box_gap;
+          if (s + ii == _new_idx && _new_idx + 1 < dm_count) {   // "New" over it, below the older ones
+            if (cur_y - lh < hist_start_y) break;
+            div_y = cur_y - lh;
+            cur_y = div_y - box_gap;
+          }
         }
+        return n_vis;
+      };
+      if (_anchor_new) {
+        _anchor_new = false;
+        _dm_hist_scroll = anchorScroll(stack, div_y, _dm_hist_sel, dm_count);
+        hs = scrollMetrics();
       }
+      stack(_dm_hist_scroll);
       _hist_visible = n_vis;
       for (int i = 0; i < n_vis && (_dm_hist_scroll + i) < dm_count; i++) {
         int item = _dm_hist_scroll + i;
@@ -1614,6 +1683,8 @@ public:
         drawHeadedBubble(display, y, bh, lh, sel, reserve, e.outgoing, sender, body, age, mark, expand, mq_delay);
       }
 
+      if (div_y >= 0) drawNewDivider(display, div_y, display.width() - reserve, lh);
+
       if (dm_count == 0) {
         display.setColor(DisplayDriver::LIGHT);
         display.drawTextCentered(display.width()/2, display.height()/2, "No messages yet");
@@ -1705,7 +1776,8 @@ public:
       const int MAX_VIS_BOXES = 8;
       int box_ys[MAX_VIS_BOXES], box_hs[MAX_VIS_BOXES], n_vis = 0;
       // Fixed-track scrollbar metrics + stable gutter reserve (see DM history above).
-      HistScroll hs = computeHistScroll(display, expand, ch_hist_count, _hist_scroll,
+      auto scrollMetrics = [&]() {
+        return computeHistScroll(display, expand, ch_hist_count, _hist_scroll,
           hist_start_y, cby, lh,
           [&](int idx) -> const char* {
             int rp = _history.histEntryForChannel(_sel_channel_idx, idx);
@@ -1714,18 +1786,22 @@ public:
             const char* s = strstr(t, ": ");
             return skipReplyPrefix(s ? s + 2 : t);
           });
+      };
+      HistScroll hs = scrollMetrics();
       int reserve = hs.reserve;
-      {
-        // Stack boxes upward from just above the compose row — see the DM
-        // history block above for why (newest at the bottom, like a typical
-        // messenger). box_ys[i] still corresponds to item (_hist_scroll + i).
+      int div_y = -1;   // "New", when shown
+      // Stack boxes upward from just above the compose row — see the DM
+      // history block above for why (newest at the bottom, like a typical
+      // messenger). box_ys[i] still corresponds to item (s + i).
+      auto stack = [&](int s) {
         const int fixed_bh = 2 * lh + 1;
         const int box_gap = expand ? 2 : 1;
         int cur_y = cby - box_gap;   // reserve the same gap against compose as between boxes
-        for (int ii = 0; ii < MAX_VIS_BOXES && (_hist_scroll + ii) < ch_hist_count; ii++) {
+        n_vis = 0; div_y = -1;
+        for (int ii = 0; ii < MAX_VIS_BOXES && (s + ii) < ch_hist_count; ii++) {
           int bh = fixed_bh;
           if (expand) {
-            int rp = _history.histEntryForChannel(_sel_channel_idx, _hist_scroll + ii);
+            int rp = _history.histEntryForChannel(_sel_channel_idx, s + ii);
             if (rp >= 0) {
               const char* rtext = _history.chAtPos(rp).text;
               const char* rsep = strstr(rtext, ": ");
@@ -1737,8 +1813,20 @@ public:
           if (box_top < hist_start_y) break;
           box_ys[n_vis] = box_top; box_hs[n_vis] = bh; n_vis++;
           cur_y = box_top - box_gap;
+          if (s + ii == _new_idx && _new_idx + 1 < ch_hist_count) {   // "New" over it, below the older ones
+            if (cur_y - lh < hist_start_y) break;
+            div_y = cur_y - lh;
+            cur_y = div_y - box_gap;
+          }
         }
+        return n_vis;
+      };
+      if (_anchor_new) {
+        _anchor_new = false;
+        _hist_scroll = anchorScroll(stack, div_y, _hist_sel, ch_hist_count);
+        hs = scrollMetrics();
       }
+      stack(_hist_scroll);
       _hist_visible = n_vis;
       updateChannelUnread();  // mark everything in the just-computed visible window as seen
 
@@ -1784,6 +1872,8 @@ public:
         drawHeadedBubble(display, y, bh, lh, sel, reserve, outgoing, sender, body, age, mark, expand, mq_delay);
       }
 
+      if (div_y >= 0) drawNewDivider(display, div_y, display.width() - reserve, lh);
+
       if (ch_hist_count == 0) {
         display.setColor(DisplayDriver::LIGHT);
         display.drawTextCentered(display.width()/2, display.height()/2, "No messages yet");
@@ -2200,16 +2290,12 @@ public:
         if (_pick_target) { commitPickTargetChannel(_sel_channel_idx); return true; }
         if (_pick_fav_slot >= 0) { commitPickFavChannel(_sel_channel_idx); return true; }
         if (_pick_bot_channel) { commitPickBotChannel(_sel_channel_idx); return true; }
-        int hc = _history.histCountForChannel(_sel_channel_idx);
-        _unread_at_entry = (int)_history.chUnread(_sel_channel_idx);
-        _hist_scroll = 0;
-        _hist_sel = hc > 0 ? 0 : -1;
-        _viewing_max_seen = _hist_sel >= 0 ? _hist_sel : 0;
+        beginChannelView(_sel_channel_idx);
         _phase = CHANNEL_HIST;
         // Not updateChannelUnread() here: _hist_visible is still whatever this
         // channel's first render() hasn't computed yet (stale, shared with
-        // DM_HIST) — calling it now could ratchet _viewing_max_seen past what's
-        // actually about to be shown. render() calls it once that's fresh.
+        // DM_HIST) — calling it now could mark more seen than is about to be
+        // shown. render() calls it once that's fresh.
         if (_share_mode) beginShareCompose(true);
         return true;
       }

examples/companion_radio/ui-new/UITask.cpp

@@ -2210,6 +2210,17 @@ void UITask::simMessage(const char* text) {
   onMessageArrived(ev);
 }
 
+// Sim tests: read and new messages (UiCore::simUnreadDemo), then channel 0
+// (which 0) or the first chat contact (1) opened as from the list.
+void UITask::simUnread(int which) {
+  if (which < 0) { _core->simUnreadDemo(); return; }
+  if (which == 0) { openChannelHistory(0); return; }
+  for (int i = 0; i < the_mesh.getNumContacts(); i++) {
+    ContactInfo c;
+    if (the_mesh.getContactByIdx(MAX_ANON_CONTACTS + i, c) && c.type == ADV_TYPE_CHAT) { openContactDM(c); return; }
+  }
+}
+
 void UITask::simCompose(const char* text) {
   gotoMessagesScreen();
   ((MessagesScreen*)messages_screen)->simCompose(text);
@@ -2716,6 +2727,11 @@ extern "C" EMSCRIPTEN_KEEPALIVE void sim_compose(const char* text) {
   if (g_sim_ui_task_for_js) g_sim_ui_task_for_js->simCompose(text);
 }
 
+// Sim tests: -1 files read and new messages, 0 opens channel 0, 1 the first DM.
+extern "C" EMSCRIPTEN_KEEPALIVE void sim_unread(int which) {
+  if (g_sim_ui_task_for_js) g_sim_ui_task_for_js->simUnread(which);
+}
+
 // Sim tests: a channel message arrives, alerted in Settings > Message alert's
 // style (0 Normal, 1 Compact, 2 Off).
 extern "C" EMSCRIPTEN_KEEPALIVE void sim_message(const char* text, int style) {

examples/companion_radio/ui-new/UITask.h

@@ -284,6 +284,7 @@ public:
 #ifdef SIM_PLATFORM
   void simCompose(const char* text);   // sim tests: a channel post's keyboard holding `text`
   void simMessage(const char* text);   // sim tests: a channel message arrives
+  void simUnread(int which);           // sim tests: read and new messages, opened
 #endif
   void openContactDM(const ContactInfo& ci);
   void openChannelHistory(uint8_t channel_idx);   // Favourites dial: open a pinned channel