diff --git a/evidence/native-width-dependency-supply-20261007/README.md b/evidence/native-width-dependency-supply-20261007/README.md
new file mode 100644
index 0000000000..ac7ab478e8
--- /dev/null
+++ b/evidence/native-width-dependency-supply-20261007/README.md
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+# Native width declaration supply
+
+Layout.get_content_width arranges at zero height: incoming height is unused,
+but arrangement styles still matter. Its original HeightDependency declaration
+now owns both answers through NativeOptimalWidth. The separate consumer override
+in NativeWidgetWidth is deleted; shared NativeWidgetMeasurementHeight selects
+container/leaf once and consumes the original compiled layout declaration.
+
+IndependentHeight remains conservative about styles. Undeclared arrangers and
+custom width methods still receive ContextHeight from Layout.__init_subclass__;
+explicit custom declarations retain their own policies. Box and relative-height
+resources, epochs, descendants, placement and raw style publication are unchanged.
+
+Four affected checks passed in 0.46 seconds: one container acquisition for a
+live custom getter, original native paint/raw writes, height-independent custom
+layout hooks retaining style inputs, and unknown layout/scalar behavior.
+Before/after AST covers 724/725 modules with zero omissions and all width
+supply/style/measurement consumers. There is no competing runtime writer of
+Layout._content_width_dependency; it remains class-declaration-owned.
+
+The original loaded source Toad App passed with ten tabs, 508 widgets, zero
+inputs/providers and empty stderr. Pointer first-display medians were 33.9 ms
+on each side (maxima 80.2/64.0 ms). Original cProfile native is_container calls
+were 453/270, versus 506/303 in retained prior source App profiles. These are
+observed calls, not compressed Chrome transitions or a controlled timing trial.
+app.json preserves raw profile rows/hashes; stdout/stderr are retained here;
+original profiles remain at
+/home/ts/.cache/agent-scratch/native-width-supply-app-20261007.
+
+Production is unchanged from a2056caa4. Private declaration-table replacement
+outside Layout.__init_subclass__ is not certified; normal custom methods and
+C3 subclass declarations still bind their original policy or conservative
+ContextHeight. This does not change box/relative source validity or cache reuse.
+No package/public operation or reliable overall latency gain. The actual
+agent-switch and ACP costs remain separate unresolved workflows.
diff --git a/evidence/native-width-dependency-supply-20261007/app-stderr.log b/evidence/native-width-dependency-supply-20261007/app-stderr.log
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/evidence/native-width-dependency-supply-20261007/app-stdout.log b/evidence/native-width-dependency-supply-20261007/app-stdout.log
new file mode 100644
index 0000000000..bf9276507e
--- /dev/null
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diff --git a/evidence/native-width-dependency-supply-20261007/app.json b/evidence/native-width-dependency-supply-20261007/app.json
new file mode 100644
index 0000000000..126961a721
--- /dev/null
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new file mode 100644
index 0000000000..665826cc38
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+....                                                                     [100%]
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diff --git a/evidence/native-width-dependency-supply-20261007/source.json b/evidence/native-width-dependency-supply-20261007/source.json
new file mode 100644
index 0000000000..212519dadb
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+        "get_content_width"
+      ],
+      [
+        "tests/test_height_independent_measurement.py",
+        160,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "tests/test_line_surface_style_measurement.py",
+        64,
+        "Load",
+        "widget._content_width_dependency"
+      ]
+    ]
+  },
+  "after": {
+    "revision": "66921a083f01f1bf438a242707b14b1feb2a77e8",
+    "modules": 725,
+    "omissions": [],
+    "sites": [
+      [
+        "src/textual/_measurement.py",
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+        "declaration",
+        "styles_sensitive"
+      ],
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+        "declaration",
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+      ],
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+        "Load",
+        "widget._content_width_dependency"
+      ],
+      [
+        "src/textual/_measurement.py",
+        196,
+        "Load",
+        "child._content_width_dependency"
+      ],
+      [
+        "src/textual/layout.py",
+        281,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "src/textual/layout.py",
+        246,
+        "Store",
+        "cls._content_width_dependency"
+      ],
+      [
+        "src/textual/layout.py",
+        254,
+        "Store",
+        "cls._content_width_dependency"
+      ],
+      [
+        "src/textual/layouts/stream.py",
+        124,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "src/textual/scroll_view.py",
+        63,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "src/textual/widget.py",
+        2104,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "src/textual/widget.py",
+        4163,
+        "Store",
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+      ],
+      [
+        "src/textual/widget.py",
+        326,
+        "Load",
+        "self._content_width_dependency"
+      ],
+      [
+        "src/textual/widgets/_button.py",
+        376,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "src/textual/widgets/_digits.py",
+        89,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "src/textual/widgets/_input.py",
+        701,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "src/textual/widgets/_option_list.py",
+        840,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "src/textual/widgets/_rich_log.py",
+        141,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "src/textual/widgets/_rule.py",
+        200,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "src/textual/widgets/_switch.py",
+        196,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "src/textual/widgets/_toggle_button.py",
+        231,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "tests/test_box_model.py",
+        14,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "tests/test_box_model.py",
+        53,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "tests/test_box_model.py",
+        102,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "tests/test_box_model.py",
+        151,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "tests/test_box_model.py",
+        175,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "tests/test_height_independent_measurement.py",
+        160,
+        "declaration",
+        "get_content_width"
+      ],
+      [
+        "tests/test_line_surface_style_measurement.py",
+        64,
+        "Load",
+        "widget._content_width_dependency"
+      ]
+    ]
+  }
+}
diff --git a/src/textual/_measurement.py b/src/textual/_measurement.py
index a0e7347ad7..583690b50c 100644
--- a/src/textual/_measurement.py
+++ b/src/textual/_measurement.py
@@ -94,16 +94,6 @@ class NativeWidgetWidth(NativeWidgetMeasurementHeight):
     def layout_dependency(self, widget: Widget) -> HeightDependency:
         return widget.layout._content_width_dependency
 
-    def styles_sensitive(self, widget: Widget) -> bool:
-        if widget.is_container and widget._native_measurement_layout_hooks:
-            from textual.layout import Layout
-
-            # Native optimal-width measurement selects the same arrangement.
-            # A custom width method retains its independently declared inputs.
-            if type(widget.layout).get_content_width is Layout.get_content_width:
-                return NATIVE_LAYOUT_HEIGHT.styles_sensitive(widget)
-        return super().styles_sensitive(widget)
-
 
 class NativeLayoutHeight(HeightDependency):
     def depends(self, widget: Widget) -> bool:
@@ -122,6 +112,13 @@ def styles_sensitive(self, widget: Widget) -> bool:
         return widget.layout._arrangement_height_dependency.styles_sensitive(widget)
 
 
+class NativeOptimalWidth(IndependentHeight):
+    """Native width arranges at zero height but reads arrangement styles."""
+
+    def styles_sensitive(self, widget: Widget) -> bool:
+        return NATIVE_LAYOUT_HEIGHT.styles_sensitive(widget)
+
+
 class FlowHeight(HeightDependency):
     def styles_sensitive(self, widget: Widget) -> bool:
         # Native placement consumes declared geometry rules and child boxes.
@@ -212,6 +209,7 @@ def depends(self, widget: Widget) -> bool:
 NATIVE_WIDGET_HEIGHT = NativeWidgetHeight()
 NATIVE_WIDGET_WIDTH = NativeWidgetWidth()
 NATIVE_LAYOUT_HEIGHT = NativeLayoutHeight()
+NATIVE_OPTIMAL_WIDTH = NativeOptimalWidth()
 FLOW_HEIGHT = FlowHeight()
 STREAM_HEIGHT = StreamHeight()
 GRID_HEIGHT = GridHeight()
diff --git a/src/textual/layout.py b/src/textual/layout.py
index efb50a1403..8fb208c2c9 100644
--- a/src/textual/layout.py
+++ b/src/textual/layout.py
@@ -6,7 +6,8 @@
 
 from textual._spatial_map import SpatialMap
 from textual._measurement import (
-    INDEPENDENT_HEIGHT, NATIVE_LAYOUT_HEIGHT, HeightDependency, height_dependency,
+    NATIVE_LAYOUT_HEIGHT, NATIVE_OPTIMAL_WIDTH,
+    HeightDependency, height_dependency,
 )
 from textual.canvas import Canvas, Rectangle
 from textual.geometry import Offset, Region, Size, Spacing
@@ -276,7 +277,7 @@ def arrange(
             An iterable of widget location
         """
 
-    @height_dependency(INDEPENDENT_HEIGHT)
+    @height_dependency(NATIVE_OPTIMAL_WIDTH)
     def get_content_width(self, widget: Widget, container: Size, viewport: Size) -> int:
         """Get the optimal content width by arranging children.
 
diff --git a/tests/test_native_width_dependency_supply.py b/tests/test_native_width_dependency_supply.py
new file mode 100644
index 0000000000..afdb71c9c8
--- /dev/null
+++ b/tests/test_native_width_dependency_supply.py
@@ -0,0 +1,18 @@
+"""Width style decisions consume the original class-bound measurement supply."""
+from textual._measurement import NATIVE_WIDGET_WIDTH
+from textual.widget import Widget
+
+
+def test_leaf_width_style_decision_reads_container_once():
+    class Counted(Widget):
+        reads = 0
+
+        @property
+        def is_container(self):
+            self.reads += 1
+            return super().is_container
+
+    leaf = Counted()
+    leaf.reads = 0
+    assert NATIVE_WIDGET_WIDTH.styles_sensitive(leaf)
+    assert leaf.reads == 1