codex-gateway-imagegen

name	codex-gateway-imagegen
description	Generate raster images through the Responses-compatible gateway already configured for Codex, then save the result into the current workspace. Use when a user asks for image generation in Codex CLI, wants the output as a local file, or when the built-in image path is unavailable and the session must call the configured gateway directly.

Codex Gateway Imagegen

Use this skill to turn a prompt into an image file through the gateway defined in ~/.codex/config.toml.

It supports both:

• text-to-image generation
• image editing with one or more reference images

Quick Start

1. Confirm whether the user wants generation or editing, then confirm the output path.
2. Choose a size that matches the target:
   • Square image: 1024x1024
   • Portrait / phone screenshot: 1024x1536
   • Landscape: 1536x1024
3. Run scripts/generate_gateway_image.py relative to this skill root.
4. If image generation is rate-limited, keep the original prompt, images, size, and action. Do not shorten, rewrite, simplify, or otherwise change the prompt. The helper script retries the same request with backoff.
5. If the request fails inside the sandbox with TLS, schannel, or read-timeout errors, rerun the same command with escalated host-network access.
6. Report the saved file path.

Workflow

1. Shape the prompt

Write the prompt as a production spec, not a fragment. Include:

• Subject
• Scene
• Visual style
• Composition
• Lighting
• Output cues such as livestream screenshot, poster, photorealistic, 9:16 vertical
• UI overlays or exact on-screen elements when needed

If the user wants a live-app screenshot feel, say so explicitly and describe the overlays.

If the user wants editing, also describe:

• what should stay close to the reference image
• what should change
• whether the edit is loose restyling or high-fidelity preservation

2. Pick a legal size

Default to 1024x1024 unless the composition clearly needs another aspect ratio.

Known-good sizes from this workflow:

• 1024x1024
• 1024x1536

If the gateway returns an error like Invalid size ... below the current minimum pixel budget, increase the requested size instead of retrying the same one.

3. Generate with the helper script

The scripts/... path below is relative to this skill root. If running manually from the repository root, expand it to .codex/skills/codex-gateway-imagegen/scripts/....

For text-to-image:

python3 scripts/generate_gateway_image.py --prompt "<prompt>" --out "<output-path>" --size 1024x1024

For image editing with a local reference image:

python3 scripts/generate_gateway_image.py --prompt "<prompt>" --image "<reference-image>" --action edit --out "<output-path>" --size 1024x1536

For image editing with multiple references:

python3 scripts/generate_gateway_image.py --prompt "<prompt>" --image "<reference-1>" --image "<reference-2>" --action edit --out "<output-path>" --size 1024x1536

Optional inputs:

• --image <path>: local reference image, repeatable
• --image-url <url>: remote reference image, repeatable
• --mask <path>: local mask image for targeted edit regions
• --action auto|generate|edit: defaults to auto
• --max-retries <number>: maximum retries for image rate-limit errors, defaults to 5

The script:

• Reads base_url from ~/.codex/config.toml
• Reads OPENAI_API_KEY from ~/.codex/auth.json
• Calls /responses
• Uses model="gpt-5.5" by default
• Requests the image_generation tool with action=auto|generate|edit
• Sends prompt text as input_text
• Sends reference images as input_image
• Sends an optional mask as input_image_mask
• Decodes the returned base64 image and writes the output file

Important:

• The Responses model remains the main model such as gpt-5.5
• Image generation and editing are performed through the image_generation tool
• For editing, prefer --action edit and include at least one --image

4. Handle the common failure modes

If the call fails inside the sandbox with networking or TLS symptoms such as:

• Authentication failed, see inner exception
• schannel: AcquireCredentialsHandle failed
• The read operation timed out

then treat that as an environment-path problem first, not necessarily a gateway problem. Rerun the same script outside the sandbox with escalated host-network access.

If the call reaches the gateway and returns an HTTP error body, inspect the body before changing the prompt.

If the gateway or stream returns rate_limit_exceeded for image generation, do not change the prompt. Retry the original request after the reported delay or backoff interval. Prompt simplification is not a fix for image-per-minute limits.

If the result ignores the reference image too loosely:

• strengthen the prompt with explicit preservation instructions
• switch from auto to edit
• use a mask when only part of the image should change

5. Save outputs deliberately

If the user asked for an image for the current task, save it directly into the current workspace with a descriptive name such as:

• hero_poster.png
• livestream_vertical_v2.png
• product_mockup_square.png

Do not leave the final asset only in a temp location.

References

• Read references/troubleshooting.md when the request fails and you need the quick decision tree.