diff --git a/tests/test_render.py b/tests/test_render.py
index 1cb966d..9f20a06 100644
--- a/tests/test_render.py
+++ b/tests/test_render.py
@@ -421,6 +421,125 @@ assert terminal.process.written == "", repr(terminal.process.written)
 print("alternate scroll tests passed (3 lines per tick: arrows on alt screen, SGR when tracking, inert otherwise)")
 
 
+# the trackpad never fires the mousemap on macOS (#1838): the poller harvests
+# viewport displacement from the follow anchor into wheel lines, snaps back.
+# ticks are stepped one at a time — the poller reschedules itself, so a
+# blanket sublime.run_timeouts() would loop forever
+terminal, stream = make_terminal(rows=5, cols=20)
+Terminal._terminals[id(terminal)] = terminal
+terminal.view.id = lambda: id(terminal)
+terminal.view.text = "\n".join("row {}".format(i) for i in range(8))
+terminal.offset = 3
+ANCHOR = 3 * LINE_HEIGHT
+terminal.viewport_y = ANCHOR
+terminal.view.viewport = (0, ANCHOR)
+stream.feed("\x1b[?1002h\x1b[?1006h")
+
+del sublime._timeouts[:]
+terminal._sync_wheel_flag()
+assert terminal._trackpad_running
+terminal._sync_wheel_flag()
+assert len(sublime._timeouts) == 1, "one timer chain per terminal"
+
+
+def tick():
+    sublime._timeouts.pop(0)()
+
+
+def displace(pixels):
+    terminal.process.written = ""
+    terminal.view.viewport = (0, ANCHOR + pixels)
+    tick()
+    return terminal.process.written
+
+
+# the first tick only arms the baseline; a gesture on it must stay silent
+assert displace(50) == "", repr(terminal.process.written)
+assert terminal.view.viewport == (0, ANCHOR + 50), "arming must not snap"
+
+# 2.5 lines down: two wheel-down reports, snap back, the fraction kept
+assert displace(50) == "\x1b[<65;1;3M" * 2
+assert terminal.view.viewport == (0, ANCHOR), terminal.view.viewport
+assert terminal._trackpad_acc == 0.5, terminal._trackpad_acc
+
+# half a line more completes the kept fraction into one report
+assert displace(10) == "\x1b[<65;1;3M"
+
+# a resting tick clears the remainder, so it cannot fire a gesture later
+assert displace(10) == ""
+assert displace(0) == ""
+assert terminal._trackpad_acc == 0, terminal._trackpad_acc
+
+# upward displacement reports wheel-up
+assert displace(-30) == "\x1b[<64;1;3M"
+
+# a renderer re-anchor (fold reset, follow-scroll) is not a gesture
+displace(0)
+terminal.viewport_y = 0
+terminal.view.viewport = (0, 0)
+tick()
+assert terminal.process.written == "", repr(terminal.process.written)
+terminal.viewport_y = ANCHOR
+terminal.view.viewport = (0, ANCHOR)
+tick()
+
+# a queued follow-scroll must not starve the poller: apps repaint while
+# scrolling (less redraws per line, claude constantly), so this races every
+# gesture and used to read as shaking
+terminal._scroll_pending = True
+assert displace(40) == "\x1b[<65;1;3M" * 2
+terminal._scroll_pending = False
+
+# nor may the follow-scroll itself discard un-harvested displacement while
+# the anchor is unchanged: the poller owns the pin
+terminal.view.viewport = (0, ANCHOR + 30)
+scroll_to_cursor(terminal.view, terminal)
+assert terminal.view.viewport == (0, ANCHOR + 30), terminal.view.viewport
+terminal.process.written = ""
+tick()
+assert terminal.process.written == "\x1b[<65;1;3M", repr(terminal.process.written)
+assert terminal.view.viewport == (0, ANCHOR), terminal.view.viewport
+displace(0)  # drop the half-line remainder
+
+# a real anchor change still pins: that is the follow-scroll's job
+terminal.view.text += "row 8\n"
+scroll_to_cursor(terminal.view, terminal)
+assert terminal.viewport_y == ANCHOR + LINE_HEIGHT, terminal.viewport_y
+assert terminal.view.viewport == (0, ANCHOR + LINE_HEIGHT), terminal.view.viewport
+terminal.view.text = terminal.view.text[:-len("row 8\n")]
+terminal.viewport_y = ANCHOR
+terminal.view.viewport = (0, ANCHOR)
+tick()  # settle back on the restored anchor
+
+# a jump of a viewport or more (scrollbar, page scroll) disengages: the user
+# browses the scrollback natively until they come back to the anchor
+extent = terminal.view.viewport_extent()[1]
+assert displace(-extent) == ""
+assert not terminal._trackpad_engaged
+assert terminal.view.viewport == (0, ANCHOR - extent), "browsing must not snap"
+assert displace(-30) == "", "still browsing"
+terminal.view.viewport = (0, ANCHOR)
+tick()  # back at the anchor: re-engage
+assert terminal._trackpad_engaged
+assert displace(20) == "\x1b[<65;1;3M"
+
+# on the alt screen without tracking the same displacement turns into arrows
+stream.feed("\x1b[?1002l\x1b[?1006l\x1b[?1049h")
+terminal._sync_wheel_flag()
+assert len(sublime._timeouts) == 1, "capture never lapsed, no second chain"
+tick()  # alt entry left the anchor alone, but spend a tick anyway
+assert displace(-20) == "\x1b[A"
+
+# capture released: the poller stops and unhooks itself
+stream.feed("\x1b[?1049l")
+terminal._sync_wheel_flag()
+tick()
+assert not terminal._trackpad_running
+assert sublime._timeouts == [], sublime._timeouts
+
+print("trackpad tests passed (displacement harvested, fractions kept, jumps browse, poller unhooks)")
+
+
 # PgUp/PgDn with the configured modifier pages the view instead of reaching the
 # app; every other combination is sent as before. 24 scrollback rows above an
 # 8-row screen, viewport at the follow anchor
@@ -546,34 +665,56 @@ stream.feed("\x1b[?1049h")
 command.sync_alt_fold(terminal)
 assert terminal.view.folds == [(0, fold_end)], terminal.view.folds
 assert terminal.viewport_y == 0, terminal.viewport_y
-assert terminal.view.settings().get("scroll_past_end") is False, "alt screen must not be scrollable"
+assert terminal.view.settings().get("scroll_past_end") is True, \
+    "the scroll range must stay: the trackpad poller reads it"
 
 # a second render leaves the fold alone
 command.sync_alt_fold(terminal)
 assert terminal.view.folds == [(0, fold_end)], terminal.view.folds
 
-# a disturbed fold is re-asserted on the next render
+# a disturbed fold is re-asserted on the next render, keeping the anchor:
+# apps repaint the boundary row every scroll, and a per-repair reset made the
+# poller read the thrashing anchor as phantom down-lines (dead trackpad-up)
+terminal.viewport_y = 60
 terminal.view.folds = [(0, fold_end - 2)]
 command.sync_alt_fold(terminal)
 assert terminal.view.folds == [(0, fold_end)], terminal.view.folds
+assert terminal.viewport_y == 60, terminal.viewport_y
 
 stream.feed("\x1b[?1049l")
 command.sync_alt_fold(terminal)
 assert terminal.view.folds == [], terminal.view.folds
-assert terminal.view.settings().get("scroll_past_end") is True, "primary screen scrolls past end again"
+assert terminal.view.settings().get("scroll_past_end") is True, "left untouched"
 
-# without scrollback there is nothing to fold, but the scroll lock still applies
+# without scrollback there is nothing to fold
 terminal, stream = make_terminal(rows=5, cols=20)
 terminal.view = FakeView("r0\nr1\nr2\nr3\nr4\n")
 command = make_command(terminal.view)
 stream.feed("\x1b[?1049h")
 command.sync_alt_fold(terminal)
 assert terminal.view.folds == [], terminal.view.folds
-assert terminal.view.settings().get("scroll_past_end") is False, "alt screen must not be scrollable"
 
 print("alt fold tests passed (scrollback folded on entry, restored on exit)")
 
 
+# a fresh view gets one blank scrollback row: sublime has no layout above row
+# 0, so without it the trackpad poller has no upward slack — and on the alt
+# screen no line ever retires to provide it (trackpad-up was dead in less)
+terminal, stream = make_terminal(rows=5, cols=20)
+Terminal._terminals[id(terminal)] = terminal
+terminal.view.id = lambda: id(terminal)
+command = make_command(terminal.view)
+stream.feed("hello")
+command.run(None)
+assert terminal.offset == 1, terminal.offset
+assert terminal.view.text.startswith("\nhello"), repr(terminal.view.text)
+command.run(None)  # only a fresh view is seeded
+assert terminal.offset == 1, terminal.offset
+del sublime._timeouts[:]  # drop the follow-scrolls the renders queued
+
+print("seed row tests passed (blank row above a fresh screen, seeded once)")
+
+
 # a row whose first cells were never written: they read back as default cells
 # (StaticDefaultDict), so they form their own uncoloured run and the coloured
 # run that follows keeps the right column
diff --git a/vterm/commands.py b/vterm/commands.py
index 62ea63d..204f707 100644
--- a/vterm/commands.py
+++ b/vterm/commands.py
@@ -152,8 +152,8 @@ class VtermKeypressCommand(sublime_plugin.TextCommand):
 
     def page_scrolled(self, terminal, key=None, **mods):
         """Page the view one screen over the scrollback, before vterm_show_cursor,
-        whose scroll would pull the viewport straight back down. The alt screen is
-        folded and has no scroll range, so an app there keeps the key.
+        whose scroll would pull the viewport straight back down. The alt screen
+        has its scrollback folded away, so an app there keeps the key.
 
         Returns:
             bool: the view consumed the key; False sends it to the app.
diff --git a/vterm/mouse.py b/vterm/mouse.py
index 71daa1f..d0a833b 100644
--- a/vterm/mouse.py
+++ b/vterm/mouse.py
@@ -1,6 +1,10 @@
 """ SGR mouse reporting while the app tracks the mouse; otherwise sublime keeps drag_select """
+import math
+
+import sublime
 import sublime_plugin
 
+from .render import following
 from .terminal import Terminal
 
 # SGR button numbers for the wheel; 64 is the "scroll" bit plus direction
@@ -11,6 +15,27 @@ WHEEL_DOWN = 65
 # line per report and has no setting of its own
 WHEEL_LINES = 3
 
+# trackpad poll period: one frame at 60 Hz, so a snapped-back displacement
+# never exceeds a frame's worth of motion
+TRACKPAD_POLL_MS = 16
+
+
+def send_scroll(terminal, up, lines, cell=None):
+    """Report `lines` scroll lines to the app, or fake arrow keys on the alt screen.
+
+    One report per line, never one batched write: pi matches the SGR form
+    against a whole stdin chunk and drops anything longer."""
+    if terminal.screen.mouse_reporting_enabled():
+        if cell is None:
+            cell = (1, terminal.screen.lines // 2 + 1)
+        for _ in range(lines):
+            terminal.send_mouse(WHEEL_UP if up else WHEEL_DOWN, cell[0], cell[1], pressed=True)
+    elif terminal.screen.alternate_buffer_mode:
+        # alternate scroll: an alt-screen app that does not track the mouse
+        # gets arrow keys per wheel tick, as kitty/iTerm2/xterm do
+        for _ in range(lines):
+            terminal.send_key(key="up" if up else "down")
+
 
 def _event_to_cell(view, terminal, event, clamp=False):
     """Map a mouse event to 1-based (col, row) on the live screen, or None.
@@ -72,7 +97,7 @@ class VtermScrollCommand(sublime_plugin.TextCommand):
     """Bound to scroll wheel in the mousemap while the app tracks the mouse or is on the alt screen."""
 
     def run(self, edit, event=None, up=False):
-        """Report the wheel to the app, or fake arrow keys on the alt screen.
+        """Report one wheel notch to the app.
 
         Only bound while the app owns the wheel; otherwise sublime scrolls the
         view over the real scrollback text and this never runs.
@@ -80,20 +105,65 @@ class VtermScrollCommand(sublime_plugin.TextCommand):
         terminal = Terminal.from_id(self.view.id())
         if not terminal:
             return
-        if terminal.screen.mouse_reporting_enabled():
-            cell = _event_to_cell(self.view, terminal, event, clamp=True) if event else None
-            if cell is None:
-                cell = (1, terminal.screen.lines // 2 + 1)
-            # one report per line, never one batched write: pi matches the SGR
-            # form against a whole stdin chunk and drops anything longer
-            for _ in range(WHEEL_LINES):
-                terminal.send_mouse(WHEEL_UP if up else WHEEL_DOWN, cell[0], cell[1], pressed=True)
-        elif terminal.screen.alternate_buffer_mode:
-            # alternate scroll: an alt-screen app that does not track the mouse
-            # gets arrow keys per wheel tick, as kitty/iTerm2/xterm do
-            for _ in range(WHEEL_LINES):
-                terminal.send_key(key="up" if up else "down")
+        cell = None
+        if terminal.screen.mouse_reporting_enabled() and event:
+            cell = _event_to_cell(self.view, terminal, event, clamp=True)
+        send_scroll(terminal, up, WHEEL_LINES, cell)
 
     def want_event(self):
         """Ask sublime for the wheel coordinates."""
         return True
+
+
+def ensure_trackpad(terminal):
+    """Start the poller that turns trackpad scrolling into wheel lines.
+
+    The trackpad never fires the mousemap scroll bindings on macOS
+    (sublime_text#1838); its only trace is viewport movement. While the app
+    owns the wheel the mousemap keeps the physical wheel off the viewport, so
+    any displacement from the follow anchor is trackpad scroll: harvest whole
+    lines from it, send them like wheel lines, and snap the viewport back."""
+    if terminal._trackpad_running:
+        return
+    terminal._trackpad_running = True
+    terminal._trackpad_acc = 0.0
+    terminal._trackpad_engaged = True
+    terminal._trackpad_baseline = None
+    sublime.set_timeout(lambda: _trackpad_tick(terminal), TRACKPAD_POLL_MS)
+
+
+def _trackpad_tick(terminal):
+    """One poll: harvest viewport displacement, reschedule while captured."""
+    view = terminal.view
+    if Terminal.from_id(view.id()) is not terminal or not terminal.alive \
+            or not terminal._wheel_captured:
+        terminal._trackpad_running = False
+        return
+    anchor = terminal.viewport_y
+    extent = view.viewport_extent()[1]
+    if (anchor, extent) != terminal._trackpad_baseline:
+        # the renderer moved the anchor (follow-scroll, fold, resize): re-arm
+        # around the new position instead of reading the move as a gesture
+        terminal._trackpad_baseline = (anchor, extent)
+        terminal._trackpad_acc = 0.0
+    else:
+        dy = view.viewport_position()[1] - anchor
+        if not terminal._trackpad_engaged:
+            if following(view, terminal):
+                terminal._trackpad_engaged = True
+                terminal._trackpad_acc = 0.0
+        elif dy == 0:
+            # at rest a stale fraction must not fire on the next gesture
+            terminal._trackpad_acc = 0.0
+        elif abs(dy) >= extent:
+            # scrollbar/minimap jump or page scroll, not a trackpad gesture:
+            # let the user browse until they return to the anchor
+            terminal._trackpad_engaged = False
+        else:
+            terminal._trackpad_acc += dy / view.line_height()
+            lines = math.trunc(terminal._trackpad_acc)
+            terminal._trackpad_acc -= lines
+            if lines:
+                send_scroll(terminal, up=lines < 0, lines=abs(lines))
+            view.set_viewport_position((0, anchor), False)
+    sublime.set_timeout(lambda: _trackpad_tick(terminal), TRACKPAD_POLL_MS)
diff --git a/vterm/render.py b/vterm/render.py
index 6c631d8..f758f96 100644
--- a/vterm/render.py
+++ b/vterm/render.py
@@ -172,6 +172,14 @@ class VtermRenderCommand(sublime_plugin.TextCommand):
             terminal.pending_clear_screen = False
             self.clear_view(edit, terminal, wipe_screen=True)
 
+        if view.size() == 0 and terminal.offset == 0:
+            # one blank scrollback row above a fresh screen: sublime has no
+            # layout above row 0, and the trackpad poller needs upward slack —
+            # without it, trackpad-up is dead until a line retires, which on
+            # the alt screen is never
+            view.insert(edit, 0, "\n")
+            terminal.offset = 1
+
         self.update_lines(edit, terminal)
         self.sync_alt_fold(terminal)
 
@@ -200,25 +208,27 @@ class VtermRenderCommand(sublime_plugin.TextCommand):
 
     def sync_alt_fold(self, terminal):
         """Hide the scrollback while the app owns the alt screen: fold it away
-        (the view text is its only copy) and drop past-end scrolling so the
-        view has no scroll range. The fold is re-checked every render — the
-        screen's first row is replaced on every region scroll, and an edit at
-        the fold boundary can silently disturb a fold."""
+        (the view text is its only copy). The scroll range stays: the trackpad
+        poller pins the viewport and needs the slack to read the trackpad.
+        The fold is re-checked every render — the screen's first row is
+        replaced on every region scroll, and an edit at the fold boundary can
+        silently disturb a fold."""
         view = self.view
         alt = terminal.screen.alternate_buffer_mode
         if not alt and not terminal.applied_alt_screen:
             return
-        if alt != terminal.applied_alt_screen:
-            terminal.applied_alt_screen = alt
-            view.settings().set("scroll_past_end", not alt)
+        terminal.applied_alt_screen = alt
         end = view.text_point(terminal.offset, 0) - 1 if alt and terminal.offset else 0
         want = [(0, end)] if end > 0 else []
-        if [(r.begin(), r.end()) for r in view.folded_regions()] == want:
+        had = [(r.begin(), r.end()) for r in view.folded_regions()]
+        if had == want:
             return
         view.unfold(sublime.Region(0, view.size()))
-        if want and view.fold(sublime.Region(0, end)):
-            # a fold collapses the layout; a stale viewport anchor would stop
-            # the follow-scroll gate from re-engaging
+        if want and view.fold(sublime.Region(0, end)) and not had:
+            # a fresh fold collapses the layout; a stale viewport anchor would
+            # stop the follow-scroll gate from re-engaging. re-asserting a
+            # disturbed fold keeps the anchor: apps repaint the boundary row
+            # every scroll, and resetting per repair thrashes the poller
             terminal.viewport_y = 0
 
     def sync_cursor_style(self, terminal):
@@ -535,6 +545,11 @@ def scroll_to_cursor(view, terminal):
     """Follow the output: pin the viewport to the bottom of the live screen."""
     terminal._scroll_pending = False
     y = bottom_y(view, terminal)
+    if y == terminal.viewport_y and terminal._trackpad_running and terminal._trackpad_engaged:
+        # the anchor is unchanged and the trackpad poller owns the pin:
+        # re-pinning here would discard displacement it has not harvested yet,
+        # and apps repaint while scrolling, so this races every gesture
+        return
     terminal.viewport_y = y
     view.set_viewport_position((0, y), False)
 
diff --git a/vterm/terminal.py b/vterm/terminal.py
index 450b8a5..ff3830d 100644
--- a/vterm/terminal.py
+++ b/vterm/terminal.py
@@ -109,6 +109,12 @@ class Terminal:
         self._send_lock = threading.Lock()
         self._wheel_captured = False
         self._scroll_pending = False
+        # trackpad poller (mouse.ensure_trackpad): reschedule guard, fractional
+        # line remainder, harvesting vs. browsing, last seen (anchor, extent)
+        self._trackpad_running = False
+        self._trackpad_acc = 0.0
+        self._trackpad_engaged = True
+        self._trackpad_baseline = None
         self.pending_clear = False
         self.pending_clear_screen = False
         # a forced frame (set on activation); rendering stays on the renderer
@@ -392,6 +398,11 @@ class Terminal:
         if captured != self._wheel_captured:
             self._wheel_captured = captured
             self.view.settings().set("vterm_view.wheel_captured", captured)
+        if captured and not self._trackpad_running:
+            # checked every renderer tick, so a poller that just stopped on a
+            # capture flap is restarted within a frame or two
+            from .mouse import ensure_trackpad  # module-level import would cycle
+            ensure_trackpad(self)
 
     def send_focus(self, focused):
         """Report focus gain or loss, when the app asked for it (?1004)."""