Feature request: robust remote previews for videos and correctly rendered PDFs

What feature would you like to see?

Codex App should provide a reliable artifact preview/opening path for files generated in a remote workspace, especially:

• Video artifacts such as .mp4, .webm, .mov, and .gif.
• PDF artifacts generated by LaTeX/XeLaTeX or research/report pipelines.
• PDFs containing non-Latin text, CJK text, Unicode symbols, math fonts, embedded fonts, and selectable text layers.

When Codex is connected to a remote/SSH workspace and a command generates an artifact, the app should be able to preview or open that artifact directly from the conversation or workspace file browser, without requiring the user to set up a separate HTTP server, SSH tunnel, file copy, or external viewer.

Current pain point

A common Codex workflow is to run long experiments or document-generation jobs remotely, then inspect the generated outputs before deciding the next instruction. For example:

• A video-generation or visualization task produces preview.mp4, demo.gif, or a contact sheet.
• A LaTeX/XeLaTeX build produces paper.pdf, report.pdf, or slides.pdf.
• A research workflow needs the user to inspect whether the rendered PDF text, equations, CJK characters, and embedded fonts are correct.

Today, remote artifact review is not reliable enough for these workflows. In practice, users often have to manually download the file, expose the workspace with a temporary server, forward a port, or open a separate remote viewer just to inspect the artifact.

There is already a closely related issue for media artifacts in remote mobile Codex: #25202. This feature request is the broader version of that need: a consistent remote artifact preview/opening path across Codex App surfaces, including both video previews and high-fidelity PDF rendering.

There is also a separate PDF preview-size request in #26805. This request is different: it is primarily about rendering correctness and remote preview/opening behavior, not only the maximum previewable file size.

Expected behavior

For videos:

• Show an inline thumbnail or preview card for common video formats.
• Allow playback from the Codex App when the artifact is produced in a remote workspace.
• Provide an “Open” or “Download” action backed by a secure relay/attachment mechanism if inline playback is not feasible.
• Avoid relying on local filesystem paths that are meaningful only on the remote host.

For PDFs:

• Render PDFs with embedded fonts correctly.
• Preserve CJK/Unicode/XeLaTeX text rendering.
• Render math symbols and equations correctly.
• Preserve selectable/searchable text when the PDF contains a text layer.
• Provide a fallback “Open externally” or “Download” action when inline rendering fails.
• Surface a clear error when a PDF cannot be rendered, rather than silently showing broken/missing text.

For remote workspaces generally:

• Files linked by the assistant from the workspace should be openable from the client UI.
• Files selected in the workspace file browser should use the same preview/opening mechanism.
• The behavior should be consistent across local and remote sessions as much as possible.

Why this matters

Codex is increasingly useful for long-running remote development and research workflows. Many important outputs are not plain text diffs:

• ML/video generation experiments produce videos, GIFs, and visual previews.
• Computer vision workflows produce rendered videos, contact sheets, masks, and figures.
• Academic/research workflows produce LaTeX/XeLaTeX PDFs with equations and multilingual text.
• UI and documentation workflows produce visual artifacts that need quick inspection before the next iteration.

Without reliable remote artifact preview, the user has to leave Codex to inspect results. That breaks the feedback loop: Codex can run the experiment, but the user cannot conveniently verify whether the output is correct before giving the next instruction.

Possible implementation direction

One possible design would be to treat generated workspace artifacts as first-class previewable attachments:

• The remote host/app-server exposes artifacts through a secure, temporary relay or signed attachment URL.
• The client UI renders supported formats inline where possible.
• Unsupported or failed previews still get a reliable download/open action.
• PDF rendering uses a mature renderer with embedded-font/CJK/Unicode support, with clear fallback behavior.

The exact implementation is up to the Codex team, but the important user-facing requirement is: remote-generated videos and PDFs should be easy to inspect from the Codex App itself.