diff --git a/tests/pyproject.toml b/tests/pyproject.toml
index 72df969ba..fc0bc5a57 100644
--- a/tests/pyproject.toml
+++ b/tests/pyproject.toml
@@ -50,6 +50,11 @@ dependencies = [
     # MINT anything: the assertion is a request for a token, exchanged at the
     # deployed endpoint, exactly as a real service does it.
     "pyjwt[crypto]>=2.9",
+    # Reads the .xlsx half of every export a journey downloads. A workbook is a
+    # zip of XML, so a hand-rolled reader is possible and is a liability: the
+    # assertion would then depend on test code nobody reviews as carefully as
+    # the product. Read-only here — the suite writes no spreadsheets.
+    "openpyxl>=3.1",
 ]
 
 [dependency-groups]
diff --git a/tests/stand/ui/downloads.py b/tests/stand/ui/downloads.py
new file mode 100644
index 000000000..0275e44f9
--- /dev/null
+++ b/tests/stand/ui/downloads.py
@@ -0,0 +1,133 @@
+"""Read back what the browser downloaded, and what the grid behind it showed.
+
+A download event and a byte count prove the transport worked, which was never
+the part in doubt. What a journey has to prove is that the file holds the table
+the user was looking at — and CSV and XLSX are written by different code
+(client-side for timeseries exports, `rust_xlsxwriter` beside the `csv` crate
+for evidence exports), so the two formats are read back and compared against
+each other as well as against the grid.
+
+Every cell — from a CSV string, an XLSX number, or a rendered DOM node — is put
+through one normalizer, so `29`, `29.0` and a formatted `"+2,705"` compare as
+the same value while an empty cell stays distinct from a zero. That distinction
+is the whole point: a serializer that turns a missing value into 0 passes any
+assertion that only counts rows.
+"""
+
+from __future__ import annotations
+
+import csv
+from datetime import date, datetime
+from pathlib import Path
+
+from openpyxl import load_workbook
+from playwright.sync_api import Locator, Page
+
+#: A table read out of an export or off the screen: normalized cells, row-wise,
+#: header rows included.
+Table = list[list[str]]
+
+#: What the SPA renders in a cell that has no value — em dash, en dash or
+#: hyphen. Read as empty, so a rendered row compares against its export.
+_EMPTY_MARKERS = frozenset({"\u2014", "\u2013", "-", ""})
+
+#: Digit-group separators and signs the UI inserts and no exporter emits:
+#: narrow no-break space, no-break space, comma, plus.
+_GROUPING = ("\u202f", "\u00a0", ",", "+")
+
+
+def download_export(
+    page: Page, menu_item: str, *, into: Path, exact: bool = True
+) -> tuple[str, Table]:
+    """Click an export menu item, save the file, and read it back as a table."""
+    with page.expect_download() as download_info:
+        page.get_by_role("menuitem", name=menu_item, exact=exact).click()
+
+    download = download_info.value
+    destination = into / download.suggested_filename
+    download.save_as(destination)
+
+    return download.suggested_filename, read_export(destination)
+
+
+def read_export(path: Path) -> Table:
+    if path.suffix == ".csv":
+        return _read_csv(path)
+    if path.suffix == ".xlsx":
+        return _read_xlsx(path)
+    raise AssertionError(f"no reader for {path.name}; the suite reads .csv and .xlsx")
+
+
+def rendered_rows(table: Locator) -> Table:
+    """The grid as the browser rendered it, normalized like an exported table.
+
+    A virtualized grid keeps only its visible window in the DOM, so this is the
+    window, not the whole result — compare it against the head of an export and
+    take the row total from `aria-rowcount`.
+    """
+    rows: Table = []
+    for row in table.get_by_role("row").all():
+        cells = row.locator('[role="cell"], [role="columnheader"], td, th')
+        rows.append([_cell(text) for text in cells.all_inner_texts()])
+
+    return rows
+
+
+def claimed_row_count(table: Locator) -> int:
+    """What the grid says its full result set holds, virtualization aside."""
+    declared = table.get_attribute("aria-rowcount")
+    assert declared is not None, "grid declares no aria-rowcount to reconcile the export against"
+
+    return int(declared)
+
+
+def data_rows(table: Table, *, after: int) -> Table:
+    """Everything below the header rows, blank padding dropped."""
+    return [row for row in table[after:] if any(cell for cell in row)]
+
+
+def _read_csv(path: Path) -> Table:
+    # The exporters lead with a BOM so a spreadsheet keeps non-ASCII names.
+    text = path.read_text(encoding="utf-8-sig")
+
+    return [[_cell(value) for value in row] for row in csv.reader(text.splitlines()) if any(row)]
+
+
+def _read_xlsx(path: Path) -> Table:
+    workbook = load_workbook(path, read_only=True, data_only=True)
+    try:
+        sheet = workbook.worksheets[0]
+        rows = [[_cell(value) for value in row] for row in sheet.iter_rows(values_only=True)]
+    finally:
+        workbook.close()
+
+    return [row for row in rows if any(row)]
+
+
+def _cell(value: object) -> str:
+    if value is None:
+        return ""
+    if isinstance(value, bool):
+        return str(value)
+    if isinstance(value, datetime):
+        return value.date().isoformat()
+    if isinstance(value, date):
+        return value.isoformat()
+    if isinstance(value, int | float):
+        return _number(float(value))
+
+    text = " ".join(str(value).split())
+    if text in _EMPTY_MARKERS:
+        return ""
+
+    plain = text.replace("\u2212", "-")  # the UI signs negatives with U+2212
+    for separator in _GROUPING:
+        plain = plain.replace(separator, "")
+    try:
+        return _number(float(plain))
+    except ValueError:
+        return text
+
+
+def _number(value: float) -> str:
+    return str(int(value)) if value.is_integer() else repr(value)
diff --git a/tests/stand/ui/test_collaboration_card_evidence.py b/tests/stand/ui/test_collaboration_card_evidence.py
index b883ecf3c..9d55291a0 100644
--- a/tests/stand/ui/test_collaboration_card_evidence.py
+++ b/tests/stand/ui/test_collaboration_card_evidence.py
@@ -24,6 +24,7 @@
 from insight_stand import PersonaSession
 from playwright.sync_api import Page, expect
 
+from .downloads import Table, claimed_row_count, download_export, rendered_rows
 from .flows import sign_in
 from .pages.person_view import PersonView
 
@@ -66,11 +67,23 @@ def test_collaboration_card_menu_opens_and_exports_supporting_data(
         "summary-grain evidence has no per-record reference, so nothing should offer to copy one"
     )
 
-    evidence.export().click()
-    with page.expect_download() as download_info:
-        page.get_by_role("menuitem", name="CSV", exact=True).click()
-    download = download_info.value
-    assert download.suggested_filename.endswith(".csv")
-    destination = tmp_path / download.suggested_filename
-    download.save_as(destination)
-    assert destination.stat().st_size > 0
+    exported: dict[str, Table] = {}
+    for menu_item, suffix in (("CSV", ".csv"), ("Excel", ".xlsx")):
+        evidence.export().click()
+        filename, table_out = download_export(page, menu_item, into=tmp_path)
+        assert filename.endswith(suffix), filename
+        exported[suffix] = table_out
+
+    assert exported[".csv"] == exported[".xlsx"], (
+        "a summary-grain value is serialized separately per format; both must read the same"
+    )
+
+    header, *records = exported[".csv"]
+    assert len(records) == claimed_row_count(table), (
+        "the export holds a different number of days than the grid claims"
+    )
+
+    on_screen = rendered_rows(table)
+    assert on_screen[0][1:] == header, "exported columns differ from the rendered ones"
+    for shown, written in zip(on_screen[1:], records, strict=False):
+        assert shown[1:] == written, "a rendered day differs from the one exported"
diff --git a/tests/stand/ui/test_git_output_timeseries.py b/tests/stand/ui/test_git_output_timeseries.py
index 42b4abd6e..f8ca1493e 100644
--- a/tests/stand/ui/test_git_output_timeseries.py
+++ b/tests/stand/ui/test_git_output_timeseries.py
@@ -6,9 +6,10 @@
 the table presentation, switches presentations, or produces browser downloads.
 Those behaviors exist only after the component renders and handles user input.
 
-Metric values are not asserted because the stand manifest declares no golden
-metrics. The journey instead verifies the stable structure built from seeded Git
-activity and that both export paths produce non-empty browser downloads.
+Metric values are not asserted against anything this suite invented, because the
+stand manifest declares no golden metrics. What is asserted is a reconciliation:
+the numbers in both downloaded files are the numbers the deployed table renders,
+which holds whatever the seed contains.
 """
 
 from __future__ import annotations
@@ -21,12 +22,21 @@
 from insight_stand import PersonaSession
 from playwright.sync_api import Page, expect
 
+from .downloads import Table, download_export, rendered_rows
 from .flows import sign_in
 from .pages.person_view import PersonView
 
 # Quality vector of this module's tests.
 pytestmark = pytest.mark.reliability
 
+#: A row of the timeseries proper, as opposed to a header or a totals row: it
+#: leads with the bucket it covers.
+BUCKET = re.compile(r"\d{4}-\d{2}-\d{2}")
+
+
+def timeseries_rows(exported: Table) -> Table:
+    return [row for row in exported if row and BUCKET.fullmatch(row[0])]
+
 
 @pytest.mark.requires_seed("dev_lead")
 def test_git_output_repository_timeseries_switches_views_and_downloads(
@@ -55,16 +65,40 @@ def test_git_output_repository_timeseries_switches_views_and_downloads(
     expect(table.get_by_role("cell", name="Total", exact=True)).to_be_visible()
     expect(table.get_by_role("cell", name="Grand total", exact=True)).to_be_visible()
 
+    exported: dict[str, Table] = {}
     for menu_item, suffix in (("CSV (.csv)", ".csv"), ("Excel (.xlsx)", ".xlsx")):
         git_output.export().click()
-        with page.expect_download() as download_info:
-            page.get_by_role("menuitem", name=menu_item).click()
-        download = download_info.value
-        assert download.suggested_filename.startswith("output-by-repository_")
-        assert download.suggested_filename.endswith(suffix)
-        destination = tmp_path / download.suggested_filename
-        download.save_as(destination)
-        assert destination.stat().st_size > 0
+        filename, table_out = download_export(page, menu_item, into=tmp_path, exact=False)
+        assert filename.startswith("output-by-repository_"), filename
+        assert filename.endswith(suffix), filename
+        exported[suffix] = table_out
+
+    assert timeseries_rows(exported[".csv"]) == timeseries_rows(exported[".xlsx"]), (
+        "the two formats are written by different code and must still carry the same series"
+    )
+
+    on_screen = rendered_rows(table)
+    repository = on_screen[0][1]
+    assert exported[".csv"][0][0] == on_screen[0][0], (
+        "exported bucket header differs from the table's"
+    )
+    assert all(column.startswith(f"{repository} —") for column in exported[".csv"][0][1:]), (
+        f"csv columns are not the rendered repository's: {exported['.csv'][0]}"
+    )
+    assert repository in exported[".xlsx"][0], (
+        f"xlsx columns lost the repository: {exported['.xlsx'][0]}"
+    )
+
+    rendered_series = [row for row in on_screen if row and BUCKET.fullmatch(row[0])]
+    assert rendered_series, "no bucket rows on screen to reconcile the export against"
+    for shown, written in zip(rendered_series, timeseries_rows(exported[".csv"]), strict=True):
+        bucket, commits, merged, lines = shown
+        assert [commits, merged] == written[1:3], (
+            f"{bucket}: counts on screen and in the export differ"
+        )
+        assert [n.replace(",", "") for n in re.findall(r"[\d,]+", lines)] == written[3:5], (
+            f"{bucket}: the rendered lines cell and the exported columns differ"
+        )
 
     git_output.chart_view().click()
     expect(git_output.metric_selector()).to_be_visible()
diff --git a/tests/stand/ui/test_metric_evidence_drilldown.py b/tests/stand/ui/test_metric_evidence_drilldown.py
index a28049245..961ee1e39 100644
--- a/tests/stand/ui/test_metric_evidence_drilldown.py
+++ b/tests/stand/ui/test_metric_evidence_drilldown.py
@@ -3,8 +3,8 @@
 Why this is a browser test and not an API test: the analytics suite exercises
 the evidence endpoints directly, but it cannot prove that a user can traverse
 the deployed SPA from the personal dashboard into Git output, select a concrete
-repository-and-time bucket, and receive the nested supporting-data dialog with
-working browser downloads.
+repository-and-time bucket, and receive the nested supporting-data dialog whose
+downloads carry the records it displays.
 """
 
 from __future__ import annotations
@@ -17,6 +17,7 @@
 from insight_stand import PersonaSession
 from playwright.sync_api import Page, expect
 
+from .downloads import Table, claimed_row_count, download_export, rendered_rows
 from .flows import sign_in
 from .pages.person_view import PersonView
 
@@ -58,12 +59,23 @@ def test_git_commit_bucket_opens_and_exports_supporting_data(
     copy_ref.click()
     expect(evidence.dialog.get_by_role("button", name="Copied")).to_be_visible()
 
+    exported: dict[str, Table] = {}
     for menu_item, suffix in (("CSV", ".csv"), ("Excel", ".xlsx")):
         evidence.export().click()
-        with page.expect_download() as download_info:
-            page.get_by_role("menuitem", name=menu_item, exact=True).click()
-        download = download_info.value
-        assert download.suggested_filename.endswith(suffix)
-        destination = tmp_path / download.suggested_filename
-        download.save_as(destination)
-        assert destination.stat().st_size > 0
+        filename, table_out = download_export(page, menu_item, into=tmp_path)
+        assert filename.endswith(suffix), filename
+        exported[suffix] = table_out
+
+    assert exported[".csv"] == exported[".xlsx"], (
+        "one export serializes each format separately; both must carry the same records"
+    )
+
+    header, *records = exported[".csv"]
+    assert len(records) == claimed_row_count(table), (
+        "the export holds a different number of records than the grid claims"
+    )
+
+    on_screen = rendered_rows(table)
+    assert on_screen[0][1:] == header, "exported columns differ from the rendered ones"
+    for shown, written in zip(on_screen[1:], records, strict=False):
+        assert shown[1:] == written, "a rendered record differs from the one exported"
diff --git a/tests/uv.lock b/tests/uv.lock
index 7b0413a2b..98c5f2053 100644
--- a/tests/uv.lock
+++ b/tests/uv.lock
@@ -325,6 +325,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/c6/4d/556cb290170f41b97ce50fd872e10a266f141d7a38352bb3071e4ae61f41/datamodel_code_generator-0.71.0-py3-none-any.whl", hash = "sha256:680b68338d59e98a0559eeb54d8e5ca33c35b3ec0bef922ec2cc783f2cb28e9a", size = 452379, upload-time = "2026-07-24T15:32:02.467Z" },
 ]
 
+[[package]]
+name = "et-xmlfile"
+version = "2.0.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/d3/38/af70d7ab1ae9d4da450eeec1fa3918940a5fafb9055e934af8d6eb0c2313/et_xmlfile-2.0.0.tar.gz", hash = "sha256:dab3f4764309081ce75662649be815c4c9081e88f0837825f90fd28317d4da54", size = 17234, upload-time = "2024-10-25T17:25:40.039Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/c1/8b/5fe2cc11fee489817272089c4203e679c63b570a5aaeb18d852ae3cbba6a/et_xmlfile-2.0.0-py3-none-any.whl", hash = "sha256:7a91720bc756843502c3b7504c77b8fe44217c85c537d85037f0f536151b2caa", size = 18059, upload-time = "2024-10-25T17:25:39.051Z" },
+]
+
 [[package]]
 name = "genson"
 version = "1.4.0"
@@ -465,6 +474,7 @@ version = "0.1.0"
 source = { editable = "." }
 dependencies = [
     { name = "httpx" },
+    { name = "openpyxl" },
     { name = "playwright" },
     { name = "pydantic" },
     { name = "pyjwt", extra = ["crypto"] },
@@ -482,6 +492,7 @@ dev = [
 [package.metadata]
 requires-dist = [
     { name = "httpx", specifier = ">=0.27" },
+    { name = "openpyxl", specifier = ">=3.1" },
     { name = "playwright", specifier = "==1.62.0" },
     { name = "pydantic", specifier = ">=2.13" },
     { name = "pyjwt", extras = ["crypto"], specifier = ">=2.9" },
@@ -673,6 +684,18 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/79/7b/2c79738432f5c924bef5071f933bcc9efd0473bac3b4aa584a6f7c1c8df8/mypy_extensions-1.1.0-py3-none-any.whl", hash = "sha256:1be4cccdb0f2482337c4743e60421de3a356cd97508abadd57d47403e94f5505", size = 4963, upload-time = "2025-04-22T14:54:22.983Z" },
 ]
 
+[[package]]
+name = "openpyxl"
+version = "3.1.5"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "et-xmlfile" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/3d/f9/88d94a75de065ea32619465d2f77b29a0469500e99012523b91cc4141cd1/openpyxl-3.1.5.tar.gz", hash = "sha256:cf0e3cf56142039133628b5acffe8ef0c12bc902d2aadd3e0fe5878dc08d1050", size = 186464, upload-time = "2024-06-28T14:03:44.161Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/c0/da/977ded879c29cbd04de313843e76868e6e13408a94ed6b987245dc7c8506/openpyxl-3.1.5-py2.py3-none-any.whl", hash = "sha256:5282c12b107bffeef825f4617dc029afaf41d0ea60823bbb665ef3079dc79de2", size = 250910, upload-time = "2024-06-28T14:03:41.161Z" },
+]
+
 [[package]]
 name = "packaging"
 version = "26.2"