macOS Dock icon renders red/maroon halo in transparent area on some display profiles

The issue names no files or tests; start by locating the source Dock icon, shipped icon assets, and the packaging or asset-generation entry point. Compare RGB values beneath transparent pixels and the alpha-aware resizing or color-profile handling, then reproduce on the reported display configuration. Done means the Dock icon's transparent area remains free of a red or maroon halo.

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

26.715.31925 (build 5551)

What subscription do you have?

Unknown / not relevant to icon rendering

What platform is your computer?

Darwin 25.5.0 arm64 arm (macOS 26.5.2 build 25F84; Apple M1 Max)

What issue are you seeing?

The Codex macOS app icon renders with a conspicuous red/maroon halo across its nominally transparent canvas in the Dock. Neighboring Dock icons render normally, so the discoloration is localized to the Codex icon rather than being a uniform display tint.

The reporter's machine/display configuration has previously exposed the same kind of red shift when transparent PNGs were scaled through an incorrect straight-alpha/premultiplied-alpha path. This Codex release is the first shipping app they have seen exhibit the problem directly in its app icon.

What steps can reproduce the bug?

1. Run Codex App 26.715.31925 on the external C34J79x display configured as the main display at 3440 x 1440 and 100 Hz.
2. Show Codex in the macOS Dock.
3. Observe the reddish rectangular halo surrounding the purple Codex glyph, including areas intended to be transparent.

The issue was captured in a screenshot on 2026-07-19. In-product feedback thread ID: 019f7bfd-cd55-7f41-b2d9-1e2c10cbf7ed.

What is the expected behavior?

The transparent area surrounding the Codex glyph should remain visually transparent and should not introduce a red or maroon color cast when macOS scales or composites the app icon.

Additional information

The symptom is consistent with hidden reddish RGB values beneath zero or near-zero alpha leaking during scaling/compositing, or with a straight-alpha versus premultiplied-alpha mismatch. That is a hypothesis, not a confirmed root cause. Please inspect the source icon's RGB values under transparent pixels and the alpha-aware resizing/color-profile conversion used to produce the shipped icon assets.

The screenshot itself carries the C34J79x RGB display profile. The adjacent Calendar and Home icons in the same screenshot are not red-shifted.