diff --git a/piker/ui/_display.py b/piker/ui/_display.py
index e33c2c74..415827fb 100644
--- a/piker/ui/_display.py
+++ b/piker/ui/_display.py
@@ -654,6 +654,19 @@ def graphics_update_cycle(
 
         # run synchronous update on all linked flows
         for curve_name, flow in chart._flows.items():
+
+            if (
+                not (do_rt_update or do_append)
+                and liv
+                # even if we're downsampled bigly
+                # draw the last datum in the final
+                # px column to give the user the mx/mn
+                # range of that set.
+            ):
+                # always update the last datum-element
+                # graphic for all flows
+                flow.draw_last(array_key=curve_name)
+
             # TODO: should the "main" (aka source) flow be special?
             if curve_name == chart.data_key:
                 continue
diff --git a/piker/ui/_flows.py b/piker/ui/_flows.py
index 7960d649..01bbbece 100644
--- a/piker/ui/_flows.py
+++ b/piker/ui/_flows.py
@@ -34,6 +34,7 @@ import numpy as np
 from numpy.lib import recfunctions as rfn
 import pyqtgraph as pg
 from PyQt5.QtGui import QPainterPath
+from PyQt5.QtCore import QLineF
 
 from ..data._sharedmem import (
     ShmArray,
@@ -335,12 +336,6 @@ class Flow(msgspec.Struct):  # , frozen=True):
     graphics: Curve
     _shm: ShmArray
 
-    draw_last: Optional[
-        Callable[
-            [np.ndarray, str],
-            tuple[np.ndarray]
-        ]
-    ] = None
     is_ohlc: bool = False
     render: bool = True  # toggle for display loop
 
@@ -594,7 +589,6 @@ class Flow(msgspec.Struct):  # , frozen=True):
             # TODO: append logic inside ``.render()`` isn't
             # correct yet for step curves.. remove this to see it.
             should_redraw = True
-            # draw_last = True
             slice_to_head = -2
 
         # downsampling incremental state checking
@@ -690,8 +684,47 @@ class Flow(msgspec.Struct):  # , frozen=True):
         graphics.update()
         profiler('.update()')
 
+        # track downsampled state
+        self._in_ds = r._in_ds
+
         return graphics
 
+    def draw_last(
+        self,
+        array_key: Optional[str] = None,
+
+    ) -> None:
+
+        # shm read and slice to view
+        (
+            xfirst, xlast, src_array,
+            ivl, ivr, in_view,
+        ) = self.read()
+
+        g = self.graphics
+        array_key = array_key or self.name
+        x, y = g.draw_last_datum(
+            g.path,
+            src_array,
+            src_array,
+            False,  # never reset path
+            array_key,
+        )
+
+        if self._in_ds:
+            # we only care about the last pixel's
+            # worth of data since that's all the screen
+            # can represent on the last column where
+            # the most recent datum is being drawn.
+            uppx = self._last_uppx
+            y = y[-uppx:]
+            ymn, ymx = y.min(), y.max()
+            # print(f'drawing uppx={uppx} mxmn line: {ymn}, {ymx}')
+            g._last_line = QLineF(
+                x[-2], ymn,
+                x[-1], ymx,
+            )
+
 
 def by_index_and_key(
     renderer: Renderer,