diff --git a/infrastructure/xlsx/__init__.py b/infrastructure/xlsx/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/infrastructure/xlsx/scenario_export_workbook.py b/infrastructure/xlsx/scenario_export_workbook.py
new file mode 100644
index 000000000..0da8a6f4f
--- /dev/null
+++ b/infrastructure/xlsx/scenario_export_workbook.py
@@ -0,0 +1,20 @@
+"""Renders the Scenario Export workbook (ADR-0065).
+
+One ``.xlsx`` with one sheet per Scenario (model A2), each sheet's rows shaped by
+``domain.scenario_export`` and painted with the Monday-style branding in
+``infrastructure.xlsx.branding``. Programmatic openpyxl (no template) so a
+dynamic number of scenario sheets is handled natively.
+"""
+
+from __future__ import annotations
+
+from typing import Sequence
+
+from domain.scenario_export.scenario_sheet import ExportSheet
+
+
+def render_workbook(sheets: Sequence[tuple[str, ExportSheet]]) -> bytes:
+    """Render the scenario sheets into a single branded ``.xlsx`` as bytes. Each
+    tuple is a Scenario name and its shaped sheet; sheet order follows the input
+    (the requested ``scenario_ids`` order)."""
+    raise NotImplementedError
diff --git a/tests/infrastructure/xlsx/__init__.py b/tests/infrastructure/xlsx/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/infrastructure/xlsx/test_scenario_export_workbook.py b/tests/infrastructure/xlsx/test_scenario_export_workbook.py
new file mode 100644
index 000000000..d1dfaa79c
--- /dev/null
+++ b/tests/infrastructure/xlsx/test_scenario_export_workbook.py
@@ -0,0 +1,30 @@
+"""The Scenario Export workbook renderer (ADR-0065): one branded .xlsx with one
+sheet per Scenario, headers then rows, verified by re-opening the bytes."""
+
+from __future__ import annotations
+
+from io import BytesIO
+
+from openpyxl import load_workbook
+
+from domain.scenario_export.scenario_sheet import ExportSheet
+from infrastructure.xlsx.scenario_export_workbook import render_workbook
+
+
+def test_renders_a_sheet_named_for_the_scenario_with_headers_then_rows() -> None:
+    # arrange — one scenario's shaped sheet.
+    sheet = ExportSheet(
+        columns=("property_id", "loft_insulation"),
+        rows=({"property_id": 1, "loft_insulation": 1200.0},),
+    )
+
+    # act
+    data = render_workbook([("Fabric first", sheet)])
+
+    # assert — a real workbook with a sheet named for the scenario, the column
+    # contract as the header row, and the data beneath it.
+    workbook = load_workbook(BytesIO(data))
+    assert workbook.sheetnames == ["Fabric first"]
+    worksheet = workbook["Fabric first"]
+    assert [cell.value for cell in worksheet[1]] == ["property_id", "loft_insulation"]
+    assert [cell.value for cell in worksheet[2]] == [1, 1200.0]