diff --git a/c/set-protocol/include/set_plot.h b/c/set-protocol/include/set_plot.h
index ed91f87..ded4ca3 100644
--- a/c/set-protocol/include/set_plot.h
+++ b/c/set-protocol/include/set_plot.h
@@ -31,7 +31,8 @@ enum set_plot_operation {
 PCAN_ABI_API uint32_t set_plot_abi_version(void);
 /** Evaluates one operation. Returns output count, or 0 for invalid arguments.
  * TRANSFORM rejects malformed viewports; invalid gesture values return the
- * unchanged viewport. Zoom is restricted to 1..128, with focus anchoring.
+ * unchanged viewport. Zoom is restricted to 1..10000000 on X and 1..128 on Y,
+ * with focus anchoring.
  * Screen fractions increase downwards; set inverted=1 for the Y value axis.
  */
 PCAN_ABI_API size_t set_plot_eval(uint32_t operation, const double *input,
diff --git a/c/set-protocol/include/set_signal.h b/c/set-protocol/include/set_signal.h
index 5626c97..cf2a768 100644
--- a/c/set-protocol/include/set_signal.h
+++ b/c/set-protocol/include/set_signal.h
@@ -13,6 +13,7 @@ extern "C" {
 #endif
 enum { SET_SIGNAL_POLYNOMIAL, SET_SIGNAL_LINEAR, SET_SIGNAL_PCHIP, SET_SIGNAL_SPLINE };
 /* Caller-owned workspace: at least 14*count+128 doubles. No heap or globals.
+ * Bounds: 2..100000 input points, 2..1000000 output points.
  * Inputs may be unsorted; duplicate times are averaged. No extrapolation.
  * meta[0..2] = original count, unique count, RMSE at original measurements.
  * endpoint=1 includes the last time; 0 samples a cyclic period [first,last).
diff --git a/c/set-protocol/src/set_plot.c b/c/set-protocol/src/set_plot.c
index 37e17ea..2bd8b0d 100644
--- a/c/set-protocol/src/set_plot.c
+++ b/c/set-protocol/src/set_plot.c
@@ -7,6 +7,9 @@
 #include "set_plot.h"
 #include <math.h>
 
+/* Allow sample-level X navigation in multi-million-point recordings. */
+#define MIN_VIEW_WIDTH (1.0 / 10000000)
+
 static double clamp(double v, double lo, double hi) { return fmin(hi, fmax(lo, v)); }
 static int finite_values(const double *v, size_t n) {
     size_t i;
@@ -23,12 +26,12 @@ size_t set_plot_eval(uint32_t op, const double *v, size_t n, double *out, size_t
         cap < (op == SET_PLOT_TRANSFORM || op == SET_PLOT_LIMITS ? 4U : 1U)) return 0;
     if (op == SET_PLOT_TRANSFORM) {
         double w, h, fx, fy;
-        if (!finite_values(v, 4) || v[2] < 1.0/128 || v[2] > 1 ||
+        if (!finite_values(v, 4) || v[2] < MIN_VIEW_WIDTH || v[2] > 1 ||
             v[3] < 1.0/128 || v[3] > 1 || v[0] < 0 || v[1] < 0 ||
             v[0] + v[2] > 1.000000000001 || v[1] + v[3] > 1.000000000001) return 0;
         out[0] = v[0]; out[1] = v[1]; out[2] = v[2]; out[3] = v[3];
         if (!finite_values(v + 4, 6) || v[4] <= 0 || v[5] <= 0) return 4;
-        w = clamp(v[2] / v[4], 1.0/128, 1);
+        w = clamp(v[2] / v[4], MIN_VIEW_WIDTH, 1);
         h = clamp(v[3] / v[5], 1.0/128, 1);
         fx = clamp(v[8], 0, 1); fy = clamp(v[9], 0, 1);
         out[0] = clamp(v[0] + (v[2] - w) * fx - v[6] * w, 0, 1 - w);
diff --git a/c/set-protocol/src/set_signal.c b/c/set-protocol/src/set_signal.c
index 45b9b7c..96a0533 100644
--- a/c/set-protocol/src/set_signal.c
+++ b/c/set-protocol/src/set_signal.c
@@ -40,7 +40,7 @@ int set_signal_reconstruct(const double *input_x,const double *input_y,size_t co
     double coef[6]={0},r[6][6]={{0}},origin,span,scale=1,rmse=0;
     size_t i,j,k,n=0; unsigned pass;
     if(!input_x||!input_y||!out_x||!out_y||!meta||!work || count<2||count>100000
-       ||output_count<2||output_count>10000||work_count<14*count+128
+       ||output_count<2||output_count>1000000||work_count<14*count+128
        ||method<0||method>3||(endpoint!=0&&endpoint!=1)) return 1;
     pairs=(point *)work; x=work+2*count; y=x+count; d=y+count; h=d+count;
     s=h+count; q=s+count; column=q+6*count;
diff --git a/c/set-protocol/tests/fixtures/plot-v1.json b/c/set-protocol/tests/fixtures/plot-v1.json
index a06e11f..62ed262 100644
--- a/c/set-protocol/tests/fixtures/plot-v1.json
+++ b/c/set-protocol/tests/fixtures/plot-v1.json
@@ -4,7 +4,7 @@
     {"name":"zoom_x_anchor","op":0,"input":[0,0,1,1,2,1,0,0,0.25,0.5],"output":[0.125,0,0.5,1]},
     {"name":"zoom_y_anchor","op":0,"input":[0,0,1,1,1,4,0,0,0.5,0.75],"output":[0,0.5625,1,0.25]},
     {"name":"pan_clamp","op":0,"input":[0.25,0.25,0.5,0.5,1,1,20,-20,0.5,0.5],"output":[0,0.5,0.5,0.5]},
-    {"name":"zoom_limit","op":0,"input":[0,0,1,1,1000,1000,0,0,0.5,0.5],"output":[0.49609375,0.49609375,0.0078125,0.0078125]},
+    {"name":"zoom_limit","op":0,"input":[0,0,1,1,1000,1000,0,0,0.5,0.5],"output":[0.4995,0.49609375,0.001,0.0078125]},
     {"name":"ignore_invalid_zoom","op":0,"input":[0.25,0.25,0.5,0.5,0,1,0,0,0.5,0.5],"output":[0.25,0.25,0.5,0.5]},
     {"name":"horizontal_spread","op":1,"input":[100,2,8],"output":[1]},
     {"name":"vertical_contract","op":1,"input":[2,-100,8],"output":[2]},
diff --git a/python/set_devices/can_log_trends.py b/python/set_devices/can_log_trends.py
index 6ba5cbc..27d752d 100644
--- a/python/set_devices/can_log_trends.py
+++ b/python/set_devices/can_log_trends.py
@@ -10,6 +10,7 @@ from dataclasses import dataclass
 from protocan.legacycan import PROJECTS, LegacyCanFormat, decode
 
 from .can485_board import BoardFrame, SdLogImport, parse_sd_log
+from .trend_limits import MAX_TOTAL_POINTS
 
 
 @dataclass
@@ -63,7 +64,7 @@ def _values(frame: BoardFrame):
 
 
 def read_can_log(lines, *, reference_timestamp: float, capacity: int,
-                 max_total_points: int = 1_000_000,
+                 max_total_points: int = MAX_TOTAL_POINTS,
                  frame_limit: int = 100_000) -> tuple[list[CanLogChannel], SdLogImport]:
     imported = parse_sd_log(lines, reference_timestamp, limit=frame_limit)
     channels = {}
diff --git a/python/set_devices/plot_processing.py b/python/set_devices/plot_processing.py
index ef4fa9a..c128c39 100644
--- a/python/set_devices/plot_processing.py
+++ b/python/set_devices/plot_processing.py
@@ -9,11 +9,35 @@ are separate objects, never channels in the acquisition or measurement model.
 """
 from __future__ import annotations
 import csv
+from bisect import bisect_left, bisect_right
+from operator import itemgetter
 from dataclasses import dataclass
 from datetime import datetime, timezone
 from .signal_reconstruction import METHODS, reconstruct
 
 
+class FrozenPoints(tuple):
+    """Normalized immutable samples, reusable across processing requests."""
+
+    def __new__(cls, points):
+        if isinstance(points, cls):
+            return points
+        result = super().__new__(cls, ((float(x), float(y)) for x, y in points))
+        result.ordered = all(result[i - 1][0] <= result[i][0] for i in range(1, len(result)))
+        return result
+
+    def between(self, left, right):
+        if self.ordered:
+            start = bisect_left(self, left, key=itemgetter(0))
+            stop = bisect_right(self, right, key=itemgetter(0))
+            if start == 0 and stop == len(self):
+                return self
+            result = tuple.__new__(type(self), self[start:stop])
+            result.ordered = True
+            return result
+        return FrozenPoints((x, y) for x, y in self if left <= x <= right)
+
+
 @dataclass(frozen=True)
 class Axis:
     label: str = "Время"
@@ -36,7 +60,7 @@ class Series:
 
     def __post_init__(self):
         # A source may reuse mutable buffers immediately after publication.
-        object.__setattr__(self, "points", tuple((float(x), float(y)) for x, y in self.points))
+        object.__setattr__(self, "points", FrozenPoints(self.points))
 
 
 @dataclass(frozen=True)
@@ -103,7 +127,7 @@ def prepare(snapshot, key, method="pchip", output_count=1000, degree=2):
     if snapshot.x_range is not None:
         left, right = snapshot.x_range
         selected = Series(selected.key, selected.label,
-                          tuple((x, y) for x, y in selected.points if left <= x <= right),
+                          selected.points.between(left, right),
                           y_unit=selected.y_unit)
     return Request(selected, snapshot.axis, snapshot.source, method, output_count, degree, snapshot.x_range)
 
diff --git a/python/set_devices/qt_ports/plot_dual_axis.py b/python/set_devices/qt_ports/plot_dual_axis.py
index e1606f5..f57dfc7 100644
--- a/python/set_devices/qt_ports/plot_dual_axis.py
+++ b/python/set_devices/qt_ports/plot_dual_axis.py
@@ -11,6 +11,9 @@ from protocan.plot import Bounds, Viewport
 
 
 def small_amplitude(values, threshold=30):
+    extent = getattr(values, "finite_extent", None)
+    if extent is not None:
+        return max(abs(extent[0]), abs(extent[1])) <= threshold
     magnitude = max((abs(v) for v in values if math.isfinite(v)), default=None)
     return magnitude is not None and magnitude <= threshold
 
@@ -52,7 +55,8 @@ class DualAxisPlot:
             for series in self._series:
                 if series.visible and not series.discrete:
                     groups[series.key in self.right_axis_keys].extend(
-                        v for v in series.values if math.isfinite(v))
+                        getattr(series.values, "finite_extent", None) or
+                        (v for v in series.values if math.isfinite(v)))
             ranges = []
             for values in groups:
                 low, high = (min(values), max(values)) if values else (0, 1)
diff --git a/python/set_devices/qt_ports/plot_processing.py b/python/set_devices/qt_ports/plot_processing.py
index 9fb49ca..a328bd2 100644
--- a/python/set_devices/qt_ports/plot_processing.py
+++ b/python/set_devices/qt_ports/plot_processing.py
@@ -21,7 +21,7 @@ except ImportError:
         QVBoxLayout, QWidget,
     )
 
-from set_devices.signal_reconstruction import METHODS
+from set_devices.signal_reconstruction import MAX_OUTPUT_POINTS, METHODS
 from set_devices.plot_processing import Snapshot, prepare, process, write_csv
 
 RESULT_COLORS = ("#FF70D0", "#50D5FF", "#FFD166", "#83E377", "#B99AFF", "#FF9870")
@@ -88,8 +88,8 @@ class SignalProcessingPanel(QWidget):
         row.addWidget(self.degree)
         row.addWidget(QLabel("Точек результата"))
         self.count = QSpinBox()
-        self.count.setRange(2, 10000)
-        self.count.setValue(1000)
+        self.count.setRange(2, MAX_OUTPUT_POINTS)
+        self.count.setValue(10000)
         row.addWidget(self.count)
         self.apply_button = QPushButton("Рассчитать")
         self.apply_button.clicked.connect(self.calculate)
diff --git a/python/set_devices/signal_reconstruction.py b/python/set_devices/signal_reconstruction.py
index 470c031..cbaadc0 100644
--- a/python/set_devices/signal_reconstruction.py
+++ b/python/set_devices/signal_reconstruction.py
@@ -9,6 +9,8 @@ from dataclasses import dataclass
 from functools import lru_cache
 from protocan.native import NativeProtocol
 
+MAX_OUTPUT_POINTS = 1_000_000
+
 METHODS = {"polynomial": "Аппроксимация: полином МНК", "linear": "Интерполяция: линейная",
            "pchip": "Интерполяция: PCHIP", "spline": "Восстановление: кубический сплайн"}
 
@@ -35,8 +37,8 @@ def library():
         raise ValueError("Пересоберите SETProtocol с set_signal.c и set_wavegen.c") from error
 
 def reconstruct(points, method="pchip", output_count=1000, degree=2, *, endpoint=True, with_model=False):
-    if method not in METHODS or type(output_count) is not int or not 2 <= output_count <= 10000:
-        raise ValueError("Неизвестный метод или число выходных точек вне 2…10000")
+    if method not in METHODS or type(output_count) is not int or not 2 <= output_count <= MAX_OUTPUT_POINTS:
+        raise ValueError(f"Неизвестный метод или число выходных точек вне 2…{MAX_OUTPUT_POINTS}")
     count = len(points)
     if not 2 <= count <= 100000 or type(degree) is not int or not 1 <= degree <= 5:
         raise ValueError("Нужно 2…100000 исходных точек, степень 1…5")
diff --git a/python/set_devices/trend_limits.py b/python/set_devices/trend_limits.py
new file mode 100644
index 0000000..569d515
--- /dev/null
+++ b/python/set_devices/trend_limits.py
@@ -0,0 +1,5 @@
+"""Shared limits for host-side trend history buffers."""
+
+DEFAULT_CAPACITY = 100_000
+MAX_CAPACITY = 5_000_000
+MAX_TOTAL_POINTS = 10_000_000
diff --git a/python/tests/test_plot.py b/python/tests/test_plot.py
index 142b547..11f14f1 100644
--- a/python/tests/test_plot.py
+++ b/python/tests/test_plot.py
@@ -53,6 +53,21 @@ class PlotTests(unittest.TestCase):
         crossed = markers.move(Marker.A, 1900).move(Marker.B, 1100)
         self.assertEqual(-800, self.core.delta(crossed.a, crossed.b))
 
+    def test_deep_x_zoom_preserves_anchor_and_allows_pan_and_zoom_out(self):
+        view = Viewport()
+        for _ in range(65):
+            view = view.transform(self.core, zoom_x=1.25, focus_x=.3)
+            self.assertAlmostEqual(.3, view.x + .3 * view.width)
+        self.assertLess(view.width * 5_000_000, 3)
+        moved = view.transform(self.core, pan_x=.2)
+        self.assertLess(moved.x, view.x)
+        self.assertEqual(view.width, moved.width)
+        expanded = moved.transform(self.core, zoom_x=.8)
+        self.assertGreater(expanded.width, moved.width)
+        limited = view.transform(self.core, zoom_x=1e10)
+        self.assertEqual(1e-7, limited.width)
+        self.assertEqual(limited, limited.transform(self.core, zoom_x=2))
+
     def test_invalid_numeric_inputs_do_not_escape_to_painter(self):
         for value in (math.nan, math.inf, -math.inf):
             self.assertEqual(Viewport(), Viewport().transform(self.core, zoom_x=value))
diff --git a/python/tests/test_plot_processing.py b/python/tests/test_plot_processing.py
index 37cd575..ac83b7a 100644
--- a/python/tests/test_plot_processing.py
+++ b/python/tests/test_plot_processing.py
@@ -21,6 +21,20 @@ from set_devices.signal_reconstruction import METHODS
 
 
 class PlotProcessingTests(unittest.TestCase):
+    def test_million_output_points_for_all_methods(self):
+        snapshot = Snapshot([Series("a", "A", [(0, 1), (1, 3), (2, 5)])])
+        for method in METHODS:
+            with self.subTest(method=method):
+                curve = process(prepare(snapshot, "a", method, 1_000_000, 1))
+                self.assertEqual(1_000_000, len(curve.points))
+                self.assertEqual((0., 2.), (curve.points[0][0], curve.points[-1][0]))
+                for x, y in curve.points[::10000]:
+                    self.assertAlmostEqual(1 + 2 * x, y)
+                self.assertAlmostEqual(5., curve.points[-1][1])
+                self.assertTrue(curve.pieces)
+        with self.assertRaises(ValueError):
+            process(prepare(snapshot, "a", "linear", 1_000_001))
+
     def test_snapshot_copies_mutable_samples_and_excludes_hidden_and_digital(self):
         points = [[0, 0], [1, 1]]
         channel = Series("a", "Analog", points)
diff --git a/python/tests/test_plot_processing_qt.py b/python/tests/test_plot_processing_qt.py
index b0194e8..9d3e50d 100644
--- a/python/tests/test_plot_processing_qt.py
+++ b/python/tests/test_plot_processing_qt.py
@@ -56,6 +56,7 @@ class ProcessingQtTests(unittest.TestCase):
             self.panel.method.setCurrentIndex(self.panel.method.findData(method))
             self.calculate()
             self.assertEqual(method, self.panel.curve.request.method)
+
             self.panel.count.setValue(self.panel.count.value() + 1)
             self.assertEqual(index + 1, len(self.panel.curves))
             self.assertTrue(self.panel.export_button.isEnabled())
@@ -67,6 +68,12 @@ class ProcessingQtTests(unittest.TestCase):
         self.assertEqual((), self.panel.curves)
         self.assertIsNone(self.panel.curve)
 
+    def test_large_output_count_reaches_worker(self):
+        self.assertEqual(10000, self.panel.count.value())
+        self.panel.count.setValue(1_000_000)
+        self.calculate()
+        self.assertEqual(1_000_000, len(self.panel.curve.points))
+
     def test_repeated_request_does_not_duplicate_curve(self):
         self.calculate()
         self.calculate()