[Windows] Built-in XLSX preview shows filter buttons and borders but no header or cell text

What version of the Codex App are you using (From “About Codex” dialog)?

Windows desktop app, observed 2026-09-11. The exact About Codex version was not captured; the executable metadata available to this session did not expose a product version.

What subscription do you have?

Not collected for this report.

What platform is your computer?

Windows x64.

What issue are you seeing?

The built-in XLSX preview displays spreadsheet cell/selection borders and filter dropdown buttons, but the expected header text and table content appear blank. The user explicitly confirmed the affected surface is the Codex built-in Excel renderer, not Microsoft Excel.

This makes a nonempty workbook look like a failed/empty export. Both the original and modified workbook review files were reported as blank in the preview. A cropped screenshot provided by the user shows white cells, blue selection borders and filter arrows, with no visible text.

Read-only inspection of the exact local review files found:

• Nonempty worksheet XML with header cells and shared-string references.
• The primary table worksheet has 258 row records; another sheet has 15.
• Workbook-window visibility is visible; worksheet visibility is not hidden.
• The selected table worksheet retains pageBreakPreview, zoom 85%, and normal-view zoom 55%.
• Files are small, approximately 23 KB, with two original sheets (the modified file has one additional test sheet).

These observations establish that the preview is not showing the available workbook contents. They do not establish the renderer's internal failure or whether a specific view/style/import feature triggers it. No worker error was captured for this report.

What steps can reproduce the bug?

1. Open a local .xlsx review artifact from a file link in a Codex desktop conversation.
2. Inspect it in Codex's built-in spreadsheet preview.
3. Observe that the table boundaries/filter controls are visible while header text and data are not displayed.
4. Independently inspect the same XLSX package: the header cells and worksheet data are present.

Observed on existing engineering workbooks exported from embedded Excel OLE, including separately named review copies whose workbook-window visibility was made visible. The raw hidden-window exports and visible review copies were kept distinct. A public minimal reproduction has not yet been prepared; private workbooks and engineering drawings are intentionally not uploaded.

What is the expected behavior?

Show the actual cell text and headers. If a workbook feature cannot be rendered, show an explicit preview error or limitation instead of an apparently empty spreadsheet.

Additional information

Potentially related: #31749 reports a blank workbook panel on macOS with a captured worker exception. This report is Windows-specific partial rendering (borders and filter controls appear), and no evidence yet establishes the same root cause. Please merge if maintainers determine they are duplicates.

This report describes a user-observed preview defect; it does not claim a fix or a generic failure of all XLSX files. No workbook contents, source paths, engineering identifiers, credentials, or private session logs are included.

Start by reproducing the blank Windows XLSX preview from a local file link, then compare the preview with the worksheet XML containing the 258 row records and shared-string references. Done means the built-in preview displays headers and cell text, or presents an explicit error or limitation when it cannot render the workbook.