Windows desktop app renders external Markdown images as placeholders

Codex Desktop Windows: external Markdown images render as placeholders

Environment

• App: OpenAI.Codex
• Version: 26.519.2081.0
• Package: OpenAI.Codex_26.519.2081.0_x64__2p2nqsd0c76g0
• OS: Windows x64
• Shell: PowerShell

Summary

In Codex Desktop on Windows, Markdown image links to external HTTPS images rendered as broken image placeholders in the chat UI. This happened even when most image URLs were reachable and returned valid image content from PowerShell.

Steps to reproduce

1. In Codex Desktop on Windows, send an assistant response with Markdown image syntax using external HTTPS image URLs, for example:

![Ralph Fiennes](https://upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Ralph_Fiennes_from_%22The_White_Crow%22_at_Opening_Ceremony_of_the_Tokyo_International_Film_Festival_2018_%2831747095048%29_%28cropped%29.jpg/500px-Ralph_Fiennes_from_%22The_White_Crow%22_at_Opening_Ceremony_of_the_Tokyo_International_Film_Festival_2018_%2831747095048%29_%28cropped%29.jpg)

1. Observe the chat UI.
2. Validate the URLs from PowerShell with Invoke-WebRequest -Method Head or curl.exe -L.

Expected behavior

Images whose URLs return HTTP 200 and an image content type should render inline in the chat UI.

Actual behavior

The UI displayed image placeholders instead of the images.

Troubleshooting performed

• Three tested image URLs returned HTTP 200 with image/jpeg.
• One source URL from Britannica returned HTTP 403, so that specific source was legitimately blocked.
• One GQ image returned HTTP 200 but stalled during a full sequential download; downloading it in byte ranges worked.
• Local copies of all images were saved and verified as valid JPEG files with normal dimensions.
• Because every external image showed as a placeholder, including URLs that returned valid image responses, this looks like a Codex Desktop Windows image-rendering/fetching issue rather than only bad image URLs.

Workaround

Download images into the workspace and provide a local HTML preview/gallery. This avoids depending on external image rendering inside the Codex chat UI.

Related issue

Possibly adjacent: https://github.com/openai/codex/issues/14576