Codex ImageGen loses PNG transparency whenever a reference image is supplied

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

Version 26.825.51511

What subscription do you have?

Pro

What platform is your computer?

macOS 26.6.2 (Build 25G83) Darwin 25.6.0 arm64 arm

What issue are you seeing?

Summary

Transparent PNG generation works correctly when no reference image is supplied. However, whenever a reference image is included, the generated result has no alpha channel and contains a white/gray checkerboard baked into the image.

This occurs both when:

1. Editing/regenerating the supplied image.
2. Requesting a completely new image while using the supplied image only as a visual/compositional reference.

Steps to reproduce

1. In the Codex desktop app, use the built-in image-generation tool.
2. Generate a four-frame game sprite strip and explicitly request a genuine transparent RGBA background.
3. Do not supply a reference image.
4. Inspect the generated PNG.
5. Repeat the request while supplying the first transparent PNG as a reference.
6. Explicitly state that this is a brand-new generation, not an edit, and that transparency must use alpha-zero pixels rather than a painted checkerboard.
7. Inspect the new PNG.

Expected result

The reference-guided output should be an RGBA PNG with genuine transparent pixels outside the sprites. Providing a reference image should not disable transparent output.

Actual result

Without a reference:

• PNG mode: RGBA
• Alpha channel: present
• Alpha range: 0–255
• Approximately 50.6% of pixels fully transparent

With a reference:

• PNG mode: RGB
• Alpha channel: absent
• The transparency checkerboard is baked into the image pixels

A follow-up request specifically asking ImageGen to remove the checkerboard and produce actual transparency also returned an RGB PNG with no alpha channel.

Reproducibility

• Reference-free generation: 1/1 produced correct RGBA transparency
• Reference-based attempts: 3/3 produced opaque RGB images with a baked checkerboard

The issue therefore appears specific to generation/editing workflows that include a reference image.

Technical verification

The files were checked using:

• file
• sips -g hasAlpha
• Pillow alpha-channel inspection

What steps can reproduce the bug?

Feedback ID: 01a06c25-e19b-7881-abc1-d08ee18aefb7

What is the expected behavior?

No response

Additional information

No response

Reproduce the issue in the Codex desktop app using a transparent PNG as a reference, then inspect both outputs with file, sips -g hasAlpha, and Pillow alpha-channel inspection. The fix is complete when reference-guided generation preserves an RGBA PNG with alpha-zero transparent pixels instead of baking in a checkerboard, while reference-free generation continues to work.