Codex Image Generation

Codex Image Generation

Generate images through Codex's built-in image_gen tool. Do not invent a codex image subcommand: Codex image generation is agentic and is invoked through codex or codex exec.

Choose the execution path

1. If this agent already has the built-in image_gen tool, use it directly. Do not recursively start another Codex session.
2. Otherwise, invoke codex exec and explicitly tell the child agent to use its built-in imagegen skill and image_gen tool.

Both paths use Codex's ChatGPT authentication and do not require OPENAI_API_KEY. Never silently switch to the Image API, the openai CLI, or an SDK script.

Preflight for codex exec

Run:

codex --version
codex login status
codex features list

Require:

• A current Codex CLI installation.
• A ChatGPT login. If Codex is not logged in, ask the user to run codex login and choose ChatGPT authentication.
• image_generation enabled. It is normally enabled by default; if it is disabled, add --enable image_generation to the invocation.
• A Codex plan, provider, and selected reasoning model that expose image generation. The built-in tool may be unavailable on unsupported plans, including ChatGPT Free.

Do not print or inspect authentication files or tokens.

Generate with codex exec

Resolve the workspace and destination to absolute paths before composing the request. Create the destination's parent directory, then run:

codex exec \
  --cd "/absolute/path/to/workspace" \
  --sandbox workspace-write \
  --ask-for-approval never \
  --ephemeral \
  --skip-git-repo-check \
  - <<'CODEX_IMAGE_REQUEST'
Use your built-in `imagegen` skill and built-in `image_gen` tool.
Do not use the Image API fallback, `OPENAI_API_KEY`, `openai` CLI, Python SDK,
SVG, HTML, or a placeholder.

Intent: Generate one new raster image.
Use case: product-mockup
Prompt: A matte black ceramic coffee mug on a pale limestone surface.
Composition: Wide editorial product shot; mug in the right third; clean
negative space on the left.
Lighting: Soft overcast window light with natural contact shadows.
Palette: Warm off-white, charcoal, and muted stone.
Exact text: No text.
Constraints: No logo, watermark, border, frame, or extra objects.
Destination: /absolute/path/to/workspace/assets/mug-hero.png

After generation, copy the selected generated PNG to Destination, leaving the
Codex-generated original in place. Do not overwrite an existing destination.
Verify that Destination exists and is non-empty. Finish with the destination
path and the final prompt.
CODEX_IMAGE_REQUEST

Use a quoted heredoc delimiter so shell syntax in the image prompt is not evaluated. Replace the example values before running the command.

Keep --sandbox workspace-write; never use --dangerously-bypass-approvals-and-sandbox for image generation. Omit --skip-git-repo-check when repository membership is already guaranteed.

Edit or use references

Attach each local image with --image. State whether each image is an edit target or a visual reference:

codex exec \
  --cd "/absolute/path/to/workspace" \
  --sandbox workspace-write \
  --ask-for-approval never \
  --ephemeral \
  --skip-git-repo-check \
  --image "/absolute/path/to/workspace/input/product.png" \
  --image "/absolute/path/to/workspace/input/style-reference.png" \
  - <<'CODEX_IMAGE_REQUEST'
Use your built-in `imagegen` skill and built-in `image_gen` tool.
Do not use the Image API fallback or create an SDK script.

Intent: Edit the first attached image.
Image roles:
- product.png: edit target.
- style-reference.png: lighting and color reference only.
Change: Replace only the background with a warm limestone studio surface.
Preserve: Product identity, shape, proportions, label, camera angle, crop, and
all readable text.
Constraints: Do not redesign the product or add props.
Destination: /absolute/path/to/workspace/assets/product-edited.png

After generation, copy the selected generated PNG to Destination, leaving the
Codex-generated original in place. Do not overwrite an existing destination.
Verify that Destination exists and is non-empty.
CODEX_IMAGE_REQUEST

Use at most five attached images. For edits, repeat preservation invariants in the prompt. A mask, exact pixel boundary, or direct image-model parameter is not part of the built-in Codex image control surface.

Prompt contract

Include only fields that improve the request:

• Intent: generate or edit.
• Use case: the intended asset type.
• Prompt or Change: the subject and requested outcome.
• Image roles: edit target versus style, composition, or content reference.
• Composition: framing, viewpoint, subject placement, and negative space.
• Style: medium and visual treatment.
• Lighting, Palette, and Materials: concrete visual properties.
• Exact text: copy verbatim, or explicitly say no text.
• Preserve: edit invariants.
• Constraints: omissions and hard negatives.
• Transparency: request an actual transparent background when needed.
• Destination: an absolute .png path inside a writable workspace.

Treat aspect ratio, orientation, dimensions, and transparency as prompt requirements, not deterministic CLI flags. Preserve a detailed user prompt; augment a vague prompt only enough to make the requested asset actionable.

For multiple distinct assets, request one image_gen call per asset. For variants, describe each intended variation explicitly. The built-in tool does not expose n.

Output and validation

Codex first saves built-in results below $CODEX_HOME/generated_images/<session>/<call>.png. There is no built-in destination-path argument. The child agent must copy the selected image into the workspace and leave the generated original in place.

After codex exec exits:

1. Confirm every destination exists and is non-empty.
2. Inspect each image with the host agent's image-viewing tool when available.
3. Check subject, composition, exact text, edit invariants, constraints, and alpha when transparency was requested.
4. If validation fails, make one targeted prompt change and regenerate to a versioned filename. Never overwrite unless the user requested replacement.
5. Report the final path and prompt. Do not claim success from Codex's text response when the expected file is missing.

Complete option reference

Read references/options.md before adding flags, changing models, attaching images, or promising exact quality, dimensions, format, count, background, or seed controls. It separates the complete built-in image schema from Codex session flags and unsupported Image API parameters.