What variant of Codex are you using?
Codex App on macOS (26.417.41555 (1858)), Pro
What feature would you like to see?
I need the built-in image_gen / image_generation path in Codex App to support explicit, deterministic output dimensions for GPT Image workflows.
In ChatGPT web I can generate high-quality GPT-image-2 images and edit/iterate them while choosing specific output dimensions. In macOS Codex App, that does not appear to be available in the built-in path. In practice, this makes my workflow impossible, because I need exact dimensions on both the initial generation and subsequent edits.
From the public Codex repo, the current built-in tool surface still appears to expose only:
{ "type": "image_generation", "output_format": "png" }Relevant file:
codex-rs/tools/src/tool_spec.rs
By contrast, the CLI fallback now defaults to gpt-image-2 and already supports arbitrary valid WIDTHxHEIGHT sizes, with validation rules for:
- max edge
<= 3840
- both dimensions multiples of
16
- aspect ratio
<= 3:1
- total pixels between
655,360 and 8,294,400
Relevant file:
codex-rs/skills/src/assets/samples/imagegen/scripts/image_gen.py
What I need from the built-in Codex App path:
- explicit
size support on built-in image_gen
- arbitrary valid
WIDTHxHEIGHT, not only a few presets
- exact size control on both initial generation and edit iterations
- deterministic output sizing instead of prompt-only guessing
- clear validation errors for invalid sizes rather than silent fallback
This is the parity gap I’m trying to close:
- ChatGPT web: exact-dimension GPT Image workflow available
- Codex CLI fallback:
gpt-image-2 size control available
- Codex App built-in
image_gen: no explicit dimension control exposed
Additional information
Related issues:
#18636 Ability to reliably generate transparent images#18905 Codex image generation saves transparent-background requests as opaque RGB PNGs#18944 Built-in image_gen is missing basic image controls like transparent background, size, quality, and masks (closed as duplicate)
Those threads are related, but my blocker is specifically deterministic built-in dimension control in the macOS app workflow, for both generate and edit.
What variant of Codex are you using?
Codex App on macOS (
26.417.41555 (1858)), ProWhat feature would you like to see?
I need the built-in
image_gen/image_generationpath in Codex App to support explicit, deterministic output dimensions for GPT Image workflows.In ChatGPT web I can generate high-quality GPT-image-2 images and edit/iterate them while choosing specific output dimensions. In macOS Codex App, that does not appear to be available in the built-in path. In practice, this makes my workflow impossible, because I need exact dimensions on both the initial generation and subsequent edits.
From the public Codex repo, the current built-in tool surface still appears to expose only:
{ "type": "image_generation", "output_format": "png" }Relevant file:
codex-rs/tools/src/tool_spec.rsBy contrast, the CLI fallback now defaults to
gpt-image-2and already supports arbitrary validWIDTHxHEIGHTsizes, with validation rules for:<= 384016<= 3:1655,360and8,294,400Relevant file:
codex-rs/skills/src/assets/samples/imagegen/scripts/image_gen.pyWhat I need from the built-in Codex App path:
sizesupport on built-inimage_genWIDTHxHEIGHT, not only a few presetsThis is the parity gap I’m trying to close:
gpt-image-2size control availableimage_gen: no explicit dimension control exposedAdditional information
Related issues:
#18636Ability to reliably generate transparent images#18905Codex image generation saves transparent-background requests as opaque RGB PNGs#18944Built-in image_gen is missing basic image controls like transparent background, size, quality, and masks (closed as duplicate)Those threads are related, but my blocker is specifically deterministic built-in dimension control in the macOS app workflow, for both generate and edit.