Fix duplicate shared boxplot tick labels

ultraplot/axes/plot.py

@@ -6191,6 +6191,32 @@ def _parse_box_violin(fillcolor, fillalpha, edgecolor, **kw):
             edgecolor = edgecolor[0]
         return fillcolor, fillalpha, edgecolor, kw
 
+    def _boxplot_has_shared_tick_axis(self, axis_name: str) -> bool:
+        """
+        Return whether the boxplot tick axis is shared with sibling axes.
+        """
+        shared = (
+            self.get_shared_x_axes() if axis_name == "x" else self.get_shared_y_axes()
+        )
+        return len(shared.get_siblings(self)) > 1
+
+    def _apply_boxplot_tick_manager(
+        self,
+        axis_name: str,
+        positions: Iterable[Any],
+        tick_labels: Optional[Iterable[Any]] = None,
+    ) -> None:
+        """
+        Apply fixed tick locations/labels without appending duplicates on shared axes.
+        """
+        axis = self._axis_map[axis_name]
+        locator_positions = np.asarray(axis.convert_units(positions))
+        label_values = positions if tick_labels is None else tick_labels
+        axis.set_major_locator(mticker.FixedLocator(locator_positions))
+        axis.set_major_formatter(
+            mticker.FixedFormatter([str(label) for label in label_values])
+        )
+
     def _apply_boxplot(
         self,
         x,
@@ -6255,6 +6281,27 @@ def _apply_boxplot(
 
         # Plot boxes
         kw.setdefault("positions", x)
+        tick_labels = kw.get("tick_labels", kw.get("labels"))
+        manage_ticks = kw.pop("manage_ticks", True)
+        axis_name = "x" if vert else "y"
+        # Matplotlib's boxplot tick manager appends onto an existing
+        # FixedLocator/FixedFormatter pair. UltraPlot's stronger sharex/sharey
+        # modes currently share ticker state across sibling axes, so repeated
+        # boxplot calls in one shared group can duplicate tick labels.
+        #
+        # For now, avoid the native tick-manager path only for shared axes and
+        # install the intended fixed ticks ourselves. This keeps the fix narrow
+        # to the reported regression instead of changing global axis-sharing
+        # behavior in a bugfix PR.
+        #
+        # TODO: Revisit the shared ticker design more broadly. A deeper fix may
+        # be to stop aliasing ticker containers across shared axes, or to make
+        # the statistical-plot tick management path deduplicate shared fixed
+        # locators/formatters after the native call.
+        native_manage_ticks = manage_ticks and not self._boxplot_has_shared_tick_axis(
+            axis_name
+        )
+        kw["manage_ticks"] = native_manage_ticks
         if means:
             kw["showmeans"] = kw["meanline"] = True
         y = inputs._dist_clean(y)
@@ -6279,6 +6326,13 @@ def _apply_boxplot(
             # Use vert parameter
             artists = self._call_native("boxplot", y, vert=vert, **kw)
 
+        if manage_ticks and not native_manage_ticks:
+            self._apply_boxplot_tick_manager(
+                axis_name,
+                kw["positions"],
+                tick_labels=tick_labels,
+            )
+
         artists = artists or {}  # necessary?
         artists = {
             key: cbook.silent_list(type(objs[0]).__name__, objs) if objs else objs

ultraplot/tests/test_plot.py

@@ -303,6 +303,27 @@ def test_boxplot_mpl_versions(
                 assert "orientation" not in kwargs
 
 
+def test_boxplot_shared_x_axes_do_not_duplicate_tick_labels():
+    data = [np.random.random(size=j * 50) for j in range(1, 11)]
+    fig, axs = uplt.subplots(
+        nrows=2,
+        ncols=2,
+        sharex=2,
+        sharey=False,
+        xrotation=45,
+        xminorlocator="null",
+        grid=False,
+    )
+    for ax in axs:
+        ax.boxplot(data, showfliers=False, lw=0.5)
+
+    expected = [str(i) for i in range(len(data))]
+    for ax in axs:
+        labels = [tick.get_text() for tick in ax.xaxis.get_ticklabels()]
+        assert labels == expected
+    uplt.close(fig)
+
+
 def test_quiver_discrete_colors(rng):
     """
     Edge case where colors are discrete for quiver plots