[Feature]: Preview HTML and image files from Workspace Preview

[nguyenlephong]

Problem

Codex Relay already makes it practical to follow and steer a local Codex session from a phone while keeping the workspace on the developer machine. The workspace preview is especially useful because it reduces the need to return to the computer just to check what Codex produced.

Today, the Files tab is useful for reading text and source code, and Markdown has a rendered preview. However, HTML files are shown as source rather than rendered output, while image files are treated as binary and cannot be previewed. This makes it difficult to review common Codex artifacts such as standalone HTML reports, screenshots, diagrams, and other image assets directly from mobile.

Proposal

Add an extensible rendered-file preview flow to Workspace Preview, with a small initial scope:

• Render .html and .htm files in a read-only, isolated WebView.
• Preview common image formats such as PNG, JPEG, GIF, and WebP, with fit-to-screen and zoom/pan support where practical.
• Keep View source / Edit available for HTML so rendered preview does not replace the existing editor.
• Keep paths scoped to the configured workspace, block navigation outside the preview by default, and avoid exposing a native bridge to rendered HTML.
• Show a clear fallback for unsupported, oversized, or unreadable files.
• Route previews through a small MIME/type-based contract so more formats can be added later without coupling each one directly to the Files UI.

A reasonable first acceptance scope could be:

1. Tapping a supported HTML file opens its rendered preview.
2. Tapping a supported image opens an image preview.
3. HTML can still be opened as source and edited through the existing flow.
4. Existing text, code, and Markdown behavior remains unchanged.
5. Preview reads are workspace-scoped and do not modify files.

I would be happy to help implement this after aligning on the preferred UX and security boundaries.

Alternatives considered

• Start a local HTTP server and open the HTML through the Web preview. This works in some cases, but it requires extra setup and is a different workflow from selecting a file in the workspace.
• Read the HTML source or inspect the file on the computer. This misses the main benefit of reviewing generated output from mobile.
• Ask Codex to describe the image or HTML output. That can help, but it is not a substitute for seeing the actual artifact.

[nguyenlephong]

If the maintainers are open to this direction, I'd be glad to contribute the implementation and open a focused PR.

I can start with a small first slice—PNG, JPEG, GIF, and WebP preview plus a workspace-scoped HTML preview—then include focused tests and iOS simulator verification. Before I begin, I'd appreciate guidance on the preferred UX and security boundaries, especially JavaScript execution, local relative assets, and navigation from rendered HTML. I'm happy to adapt the scope to fit the project's conventions.