Codex Desktop SSH remote PDF preview fails for valid PDFs slightly above 1 MiB

Summary

In Codex Desktop connected to an SSH remote workspace, PDF preview fails for valid PDFs slightly above 1 MiB. Smaller PDFs preview correctly, PNG previews work, and the same PDFs are valid according to standard PDF tools.

Environment

• Codex Desktop on macOS
• SSH remote workspace
• Remote Codex CLI: codex-cli 0.142.5
• Tested against two separate SSH remote hosts with the same behavior

Observed behavior

The PDF preview pane shows a generic preview failure message:

This preview could not be loaded

In my localized UI the message was:

このプレビューを読み込めませんでした

No explicit size-limit message is shown.

Reproduction

On an SSH remote workspace, create valid PDF 1.4 files with different sizes and open them from Codex Desktop's PDF preview.

Observed threshold:

• Opens: minimal_padded_1024kib.pdf
• size: 1,048,576 bytes
• PDF 1.4, 1 page, not encrypted
• Fails: minimal_padded_1050kib.pdf
• size: 1,075,200 bytes
• PDF 1.4, 1 page, not encrypted

A normal report/research PDF around 3.2 MB also fails in the same remote workspace.

Validation

The failing PDFs are valid outside Codex preview:

• pdfinfo: OK
• pdftoppm: renders pages to PNG successfully
• Ghostscript: gs -q -dNOPAUSE -dBATCH -sDEVICE=nullpage file.pdf exits 0
• Python pypdf: reports expected page count and is_encrypted=False
• macOS Preview opens the copied PDF normally
• Codex can display PNGs rendered from the PDF

Expected behavior

Codex Desktop should preview valid PDFs from SSH remote workspaces above 1 MiB, or show a clear size/transfer limit error if there is an intentional limit.

Notes

This seems distinct from the local 10 MB preview-size limit. The failing remote PDF is only slightly above 1 MiB, and the UI does not show a "file too large" message.

Possibly related:

• #29125
• #26805
• #29779

If this should be tracked under an existing remote-preview issue, feel free to close as duplicate. I opened this because it has a minimal size-threshold reproduction.