MHoroszowski · MHoroszowski · May 17, 2026 · May 17, 2026
diff --git a/docs/api/enum/XlChartType.rst b/docs/api/enum/XlChartType.rst
@@ -231,3 +231,24 @@ XY_SCATTER_SMOOTH
 
 XY_SCATTER_SMOOTH_NO_MARKERS
     Scatter with Smoothed Lines and No Data Markers.
+
+WATERFALL
+    Waterfall (ChartEx). Office 2016+. Write + round-trip supported.
+
+TREEMAP
+    Treemap (ChartEx). Office 2016+. Round-trip preservation only.
+
+SUNBURST
+    Sunburst (ChartEx). Office 2016+. Round-trip preservation only.
+
+FUNNEL
+    Funnel (ChartEx). Office 2016+. Round-trip preservation only.
+
+BOX_WHISKER
+    Box & Whisker (ChartEx). Office 2016+. Round-trip preservation only.
+
+HISTOGRAM
+    Histogram (ChartEx). Office 2016+. Round-trip preservation only.
+
+PARETO
+    Pareto (ChartEx). Office 2016+. Round-trip preservation only.
diff --git a/docs/user/charts.rst b/docs/user/charts.rst
@@ -265,6 +265,54 @@ presentation with |pp|. There are more details in the API documentation for
 charts here: :ref:`chart-api`
 
 
+ChartEx — modern Office 2016 charts (waterfall, treemap, sunburst, ...)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Office 2016 introduced a new chart family — Waterfall, Treemap, Sunburst,
+Funnel, Box & Whisker, Histogram, and Pareto — that lives in a separate XML
+namespace (``cx:``, the *chart extensions* or "chartEx" part) rather than the
+classic ``c:`` chart tree. |pp| supports this family with two distinct
+capability levels:
+
+==================  ============================  =========================
+Capability          Chart types                   What you can do
+==================  ============================  =========================
+**Write**           ``WATERFALL``                 Author a brand-new chart
+**Round-trip**      ``WATERFALL``, ``TREEMAP``,   Open a deck that already
+only                ``SUNBURST``, ``FUNNEL``,     contains the chart, edit
+                    ``BOX_WHISKER``,              unrelated slides, and
+                    ``HISTOGRAM``, ``PARETO``     save without corrupting
+                                                  the chartEx part
+==================  ============================  =========================
+
+Authoring a waterfall chart uses the dedicated
+:class:`~pptx.chart.data.WaterfallChartData` container::
+
+    from pptx.chart.data import WaterfallChartData
+    from pptx.enum.chart import XL_CHART_TYPE
+
+    chart_data = WaterfallChartData()
+    chart_data.categories = ['Q1', 'Q2', 'Q3', 'Q4', 'Total']
+    chart_data.add_series('Revenue', (100, 50, -30, 80, 200), subtotals=[4])
+
+    graphic_frame = slide.shapes.add_chart(
+        XL_CHART_TYPE.WATERFALL, x, y, cx, cy, chart_data
+    )
+
+The returned |GraphicFrame| reports ``graphic_frame.has_chartex == True`` and
+its :attr:`~pptx.shapes.graphfrm.GraphicFrame.chartex` property returns a
+ChartEx proxy. (Classic charts continue to use ``.has_chart`` / ``.chart``.)
+
+The remaining ``cx:`` types currently have **round-trip preservation only** —
+``add_chart`` raises ``NotImplementedError`` for them, but a deck authored in
+PowerPoint that already contains a treemap, sunburst, etc. will read, modify,
+and save without damaging the existing chart. Writer support for those types
+is tracked as a follow-up to issue #14.
+
+The full set of ``cx:`` enum members is documented under
+:ref:`XlChartType`.
+
+
 About colors
 ~~~~~~~~~~~~
 

diff --git a/features/cht-chartex-roundtrip.feature b/features/cht-chartex-roundtrip.feature
@@ -0,0 +1,47 @@
+Feature: ChartEx round-trip behavior
+  In order to preserve modern chart parts in saved presentations
+  As a developer using python-pptx
+  I need ChartEx content and classic-chart content to round-trip correctly
+
+
+  Scenario Outline: A waterfall ChartEx part survives save and reopen
+    Given a blank slide
+      And ChartEx waterfall data case q4-total
+     When I add the ChartEx waterfall via <add-path>
+      And I round-trip the presentation for ChartEx inspection
+     Then the active ChartEx frame exposes ChartEx but not a classic chart
+      And the active ChartEx part content type is the ChartEx content type
+      And the active ChartEx partname contains chartEx
+      And the active ChartEx series values are 100.0, 50.0, -30.0, 80.0, 200.0
+
+    Examples: round-trip entry points
+      | add-path    |
+      | add_chart   |
+      | add_chartex |
+
+
+  Scenario: Classic and ChartEx chart frames coexist on one slide across round-trip
+    Given a blank slide
+      And ChartEx waterfall data case regional-rollup
+     When I add a classic chart beside a ChartEx waterfall
+     Then the slide has one classic chart frame and one ChartEx frame
+      And the classic chart frame still exposes only a classic chart
+      And the ChartEx frame still exposes only a ChartEx chart
+     When I round-trip the presentation for ChartEx inspection
+     Then the slide has one classic chart frame and one ChartEx frame
+      And the classic chart frame still exposes only a classic chart
+      And the ChartEx frame still exposes only a ChartEx chart
+      And the active ChartEx series values are 30.0, -10.0, 25.0, 15.0, 60.0
+
+
+  Scenario: A blank presentation exposes no ChartEx frames
+    Given a blank slide
+     Then the slide has no ChartEx graphic frames
+
+
+  Scenario: A blank presentation saves without any ChartEx package parts
+    Given a blank slide
+     When I round-trip the presentation for ChartEx inspection
+     Then the slide has no ChartEx graphic frames
+      And the saved package contains no ChartEx partnames
+      And the saved package contains no ChartEx content type declaration
diff --git a/features/cht-chartex-types.feature b/features/cht-chartex-types.feature
@@ -0,0 +1,34 @@
+Feature: ChartEx chart type members
+  In order to use the ChartEx chart type enumeration safely
+  As a developer using python-pptx
+  I need deferred members to fail explicitly and modern members to exist in a private range
+
+
+  Scenario Outline: Writer-deferred ChartEx types fail through add_chart
+    Given a blank slide
+      And ChartEx waterfall data case q4-total
+     When I attempt to add deferred ChartEx type <member-name>
+     Then adding deferred ChartEx type <member-name> raises NotImplementedError
+
+    Examples: writer-deferred ChartEx members
+      | member-name |
+      | TREEMAP     |
+      | SUNBURST    |
+      | FUNNEL      |
+      | BOX_WHISKER |
+      | HISTOGRAM   |
+      | PARETO      |
+
+
+  Scenario Outline: ChartEx enum members exist in the private high range
+    Then XL_CHART_TYPE.<member-name> exists with value <value>
+
+    Examples: ChartEx enum members
+      | member-name | value |
+      | WATERFALL   | 1001  |
+      | TREEMAP     | 1002  |
+      | SUNBURST    | 1003  |
+      | FUNNEL      | 1004  |
+      | BOX_WHISKER | 1005  |
+      | HISTOGRAM   | 1006  |
+      | PARETO      | 1007  |
diff --git a/features/cht-chartex-waterfall.feature b/features/cht-chartex-waterfall.feature
@@ -0,0 +1,54 @@
+Feature: ChartEx waterfall charts
+  In order to add Office 2016 waterfall charts to a slide
+  As a developer using python-pptx
+  I need the ChartEx writer path to create modern chart graphic frames
+
+
+  Scenario Outline: Add a waterfall chart through either public entry point
+    Given a blank slide
+      And ChartEx waterfall data case q4-total
+     When I add the ChartEx waterfall via <add-path>
+     Then the active ChartEx frame exposes ChartEx but not a classic chart
+      And the active ChartEx chart type is waterfall
+      And the active ChartEx series is named Revenue
+      And the active ChartEx series values are 100.0, 50.0, -30.0, 80.0, 200.0
+
+    Examples: public waterfall entry points
+      | add-path    |
+      | add_chart   |
+      | add_chartex |
+
+
+  Scenario Outline: Waterfall category labels are preserved on creation
+    Given a blank slide
+      And ChartEx waterfall data case <data-case>
+     When I add the ChartEx waterfall via <add-path>
+     Then the active ChartEx category labels are <category-labels>
+
+    Examples: category label sets
+      | data-case       | add-path    | category-labels                      |
+      | q4-total        | add_chart   | Q1, Q2, Q3, Q4, Total               |
+      | q4-total        | add_chartex | Q1, Q2, Q3, Q4, Total               |
+      | cash-bridge     | add_chart   | Start, Sales, Returns, Ops, Tax, End |
+      | cash-bridge     | add_chartex | Start, Sales, Returns, Ops, Tax, End |
+      | regional-rollup | add_chart   | East, West, Midwest, Online, Total  |
+      | regional-rollup | add_chartex | East, West, Midwest, Online, Total  |
+
+
+  Scenario Outline: Waterfall subtotal markers survive round-trip
+    Given a blank slide
+      And ChartEx waterfall data case <data-case>
+     When I add the ChartEx waterfall via <add-path>
+      And I round-trip the presentation for ChartEx inspection
+     Then the active ChartEx frame exposes ChartEx but not a classic chart
+      And the active ChartEx subtotal indices are <subtotal-indices>
+      And the active ChartEx category labels are <category-labels>
+
+    Examples: subtotal preservation cases
+      | data-case       | add-path    | subtotal-indices | category-labels                      |
+      | q4-total        | add_chart   | 4                | Q1, Q2, Q3, Q4, Total               |
+      | q4-total        | add_chartex | 4                | Q1, Q2, Q3, Q4, Total               |
+      | cash-bridge     | add_chart   | 0, 5             | Start, Sales, Returns, Ops, Tax, End |
+      | cash-bridge     | add_chartex | 0, 5             | Start, Sales, Returns, Ops, Tax, End |
+      | regional-rollup | add_chart   | 4                | East, West, Midwest, Online, Total  |
+      | regional-rollup | add_chartex | 4                | East, West, Midwest, Online, Total  |