image-gen

---

name: image-gen description: Runs image operations through the image-gen CLI: text-to-image generation, single-image edits, multi-image composition, masked edits where supported, and multi-turn iterative editing through a small local session file. Default route is xAI Grok Imagine; OpenRouter routes are available as fallbacks. Use when the user asks for an image, illustration, concept art, product render, UI mockup, visual reference, style exploration, image edit/remix, multi-image blend, masked inpaint, or iterative refinement of a previous image. license: MIT compatibility: Requires the image-gen binary on PATH. Default Grok presets need XAI_API_KEY; OpenRouter presets and pass-through IDs need OPENROUTER_API_KEY. Keys may also live in the package-local .env. allowed-tools: Bash

image-gen

Use image-gen whenever a task needs a generated or edited image. It is one CLI for image operations: a single JSON object in, a single JSON object out, with the resulting file saved to disk.

When to use it

Invoke this skill when the user asks for, implies, or would clearly benefit from:

• an illustration, concept image, scene, poster, mood board, or visual reference
• a product render, packaging concept, character/environment study, or photoreal composition
• a UI mockup, app screen concept, labeled interface draft, or visual design direction
• an edit, remix, or transform of an existing image
• a composition that blends multiple input images, transfers style, or combines references
• a masked edit that constrains changes to a specific region (xAI Grok models)
• iterative refinement across multiple turns, where each turn builds on the previous output

Do not force image generation into tasks that are really diagrams, charts, code, or written design specs unless the user asks for a rendered visual. If the user has already indicated they want an image and the remaining details are ambiguous, generate one strong first pass instead of asking setup questions.

Operations

The CLI derives the operation from the request shape:

Request shape	Operation
prompt only	generate
prompt + one image_inputs entry	edit
prompt + multiple image_inputs entries	compose
prompt + one image_inputs + mask	mask_edit (xAI Grok models only)
prompt + session	continuation; previous primary output becomes the source image unless start_fresh is true

You can pass operation explicitly for clarity; the CLI validates it against the actual shape and returns a validation_error on mismatch.

Model selection

Default to grok when xAI is configured and the user only needs a fast draft. Default to nano-banana-2 for balanced OpenRouter image-input work. It remains the safest general fallback when Grok is unavailable or when the task needs Gemini-style image editing.

Model alias	Operations	Timeout	Use for	Avoid when
grok	generate, edit, compose, mask_edit	75s	Fast drafts, normal illustrations, first passes, visual exploration, cheap iteration	The image must contain accurate text or many tightly constrained elements
grok-pro	generate, edit, compose, mask_edit	90s	Polished finals, image edits, text-heavy scenes, multi-image composition, masked inpainting, 2K requests	The user only needs a quick draft
flux-klein	generate, edit, compose	60s	Cheapest OpenRouter route for fast generation and multi-reference edits	The task needs provider-native masking or premium quality
nano-banana-2	generate, edit, compose	90s	Balanced OpenRouter default for most generation, edit, and compose tasks	The task needs masking or a typography/design specialist
seedream	generate, edit, compose	90s	Recent balanced multi-reference fallback with strong consistency	The task needs masking or more than the advertised input cap
recraft	generate, edit	60s	Design, typography, branding, packaging, signage, and text-in-image attempts	The task needs multi-image composition or masking
flux-pro	generate	120s	Premium OpenRouter FLUX.2 Pro image-only generation	The task needs an image-input edit; flux-pro will reject it as a capability error
nano-banana-pro	generate, edit, compose	180s	Premium OpenRouter image-input work where longer latency is acceptable	A cheaper route can satisfy the request

Use grok first for day-to-day xAI work, then grok-pro for quality-sensitive work or any masked edit. On OpenRouter, prefer flux-klein for economy, nano-banana-2 for balanced default, nano-banana-pro for premium image-input work, and recraft when design/typography/branding matter. Keep n at 1 unless the user asks for variants or comparison is useful.

Before choosing a paid route in an unfamiliar environment, run image-gen --status. It reports configured providers, usable presets, per-preset timeouts, and capability flags (image_inputs, multi_image, mask, session_continuation) without revealing secrets.

The gpt-image alias was removed in 0.3.0. If the user explicitly asks for it, use nano-banana-pro, flux-pro, or pass openai/gpt-5.4-image-2 directly as a vendor/slug OpenRouter model ID.

Prompting guidance

Write image prompts as production briefs, not chatty requests. Include the subject, composition, medium, lighting, camera/viewpoint, mood, palette, and constraints that matter. Omit filler like "please" or "make me".

For UI mockups, specify the screen type, layout hierarchy, visual style, typography mood, color system, device/frame, and which text must appear. Prefer grok-pro for strict UI/layout prompts.

For edits, name the source image role and describe only the intended transformation. Example: "Use the reference as the product silhouette; preserve its proportions; replace the material with brushed aluminum; render on a warm studio background."

For multi-image composition with xAI Grok, refer to inputs by index: <IMAGE_0>, <IMAGE_1>, etc. Example: "Use <IMAGE_0> as the silhouette and <IMAGE_1> as the surface texture."

For masked edits, the mask should be a same-size PNG where white areas are editable and black areas are preserved. Describe only the change inside the masked region.

For text inside images, keep requested text short and exact. If text accuracy is critical, choose grok-pro and warn that image models can still misspell small text.

Calling pattern

Run the CLI with a single JSON object by argv or stdin. Always inspect the JSON result before replying. Prefer stdin when the prompt comes from user text or contains quotes, apostrophes, or newlines; it avoids shell escaping mistakes.

Simple generation:

image-gen '{"prompt":"retrofuturist lunar workshop, warm task lighting, medium-format editorial photo, 16:9","model":"grok","aspect_ratio":"16:9"}'

Single-image edit:

image-gen '{"prompt":"turn the reference sketch into a clean product render; preserve the silhouette and proportions; use satin black metal and soft studio lighting","model":"grok-pro","image_inputs":["./sketch.png"]}'

Multi-image composition:

image-gen '{"prompt":"Use <IMAGE_0> as the silhouette and <IMAGE_1> as the surface; soft studio light","model":"grok-pro","image_inputs":["./silhouette.png","./material.jpg"]}'

Masked edit:

image-gen '{"prompt":"replace only the masked area with a navy textile","model":"grok-pro","image_inputs":["./photo.png"],"mask":"./mask.png"}'

Multi-turn session:

image-gen '{"prompt":"studio render of a brutalist espresso cup","session":{"path":"./session.json"},"model":"grok-pro"}'
image-gen '{"prompt":"now place it on a pale travertine surface, soft morning light","session":{"path":"./session.json"}}'
image-gen '{"prompt":"different direction: a chrome-finished cup","session":{"path":"./session.json","start_fresh":true}}'

Safer stdin pattern for quote-heavy or multi-line prompts:

image-gen <<'JSON'
{"prompt":"a bookstore called The Navigator's Desk, hand-painted sign, rainy evening street photo","model":"grok","aspect_ratio":"16:9"}
JSON

Useful input fields:

• prompt - required natural-language prompt
• model - preset alias, known xAI model ID, or full OpenRouter vendor/slug; defaults to grok
• aspect_ratio - 1:1, 16:9, 9:16, 4:3, 3:4, 4:1, 1:4, 8:1, 1:8, 2:3, 3:2, 9:19.5, 19.5:9, 9:20, 20:9, 1:2, 2:1, or auto. xAI does not accept 4:1, 1:4, 8:1, or 1:8.
• size - model-specific hint such as 1024, 1K, 2K, or 4K; xAI maps supported hints to 1k or 2k
• n - number of images, 1-4
• image_inputs - local image paths or HTTPS URLs for edit/compose/mask_edit operations (preferred name)
• reference_images - legacy alias for image_inputs; do not combine with image_inputs
• mask - mask image for masked edits (xAI Grok only; one image_input required)
• operation - optional, validated against the request shape
• session - { "path": string, "start_fresh"?: boolean } for multi-turn continuation
• output - explicit file path, or a directory only if it already exists or ends with /
• output_dir - directory for generated filenames when output is not set
• system - optional preamble for global style or policy constraints
• seed - passed through to OpenRouter when supported; not sent to xAI

Local image paths are read and sent as base64 data URIs. HTTPS URLs pass through. Plain HTTP URLs are rejected.

Result handling

Successful output looks like:

{"ok":true,"operation":"edit","path":"/abs/path/image.png","paths":["/abs/path/image.png"],"model":"grok-imagine-image-pro","alias":"grok-pro","provider":"xai","bytes":893000,"elapsed_ms":2840,"cost_usd":0.07,"prompt":"...","inputs":{"images":["/abs/in.png"],"mask":null},"session":null}

Use path for the primary image and paths when n > 1. Inspect operation to confirm what the call did, and inputs to confirm which sources the model saw. The session field returns the absolute session path, the new turn number, and the new primary_output after a continuation turn; treat it as the source of truth for follow-up calls.

Never paste base64 into the chat. Do not claim visual details you have not inspected; generation succeeded means the file exists, not that the composition is perfect.

In the final reply:

• state what operation ran and where the image was saved
• include cost and model only when useful or when the user cares about spend/model choice
• include Markdown image syntax if the current UI can render local paths
• still provide the absolute path, because some desktop/webview environments block arbitrary filesystem image loading

Portable presentation pattern:

Generated image saved here: `/absolute/path/from/tool/output.png`

![generated image](/absolute/path/from/tool/output.png)

If the Markdown image appears broken in the UI, the saved file path is still the source of truth.

Sessions

Sessions are local JSON files. They store prompts, model/provider info, output paths, and a primary_output pointer. They never store API keys or base64 image payloads.

• Pass session.path to enable continuation. The first call creates the file; later calls read it and continue.
• By default, the previous turn's primary_output is prepended to image_inputs for the next call. Empty image_inputs becomes a single-image edit; non-empty image_inputs becomes a multi-image compose.
• Pass session.start_fresh: true to skip pre-loading the previous output for that turn (useful for branching).
• If the session file is malformed or its previous primary output has been deleted, the CLI returns a session_error and does not call the provider.

Errors and recovery

Failures return JSON with ok:false, error, and code.

• auth_error - tell the user the selected provider key is missing/invalid (XAI_API_KEY for Grok presets, OPENROUTER_API_KEY for OpenRouter presets); do not ask for the key in chat unless they volunteer to set it
• validation_error - fix the JSON, model alias, aspect ratio, output path, image input, mask, session shape, or operation hint and retry once
• capability_error - the chosen model cannot perform the requested operation. Switch to a model that can, or drop the unsupported field. The most common pattern is mask outside Grok or image_inputs on flux-pro.
• session_error - the session file is malformed or the previous primary output has been deleted. Either start a new session path, fix the file, or pass start_fresh: true.
• api_error - if the chosen model is unavailable, retry once with this fallback ladder: grok-pro -> grok, flux-pro -> grok, flux-klein -> nano-banana-2, recraft -> nano-banana-2, premium OpenRouter alias -> nano-banana-2; otherwise summarize the provider error
• network_error - retry once if the task is important; mention timeout/connectivity if it fails again. Some OpenRouter presets legitimately take 60-180 seconds; check --status or --list-models before assuming a job is stuck.

Do not loop repeatedly on paid generations. One corrective retry is usually enough.

Quality checklist before replying

Ask yourself:

1. Did I choose the cheapest model that can perform the requested operation?
2. Did the prompt include enough visual direction to avoid a generic result?
3. For edits/compose/mask_edit, did I pass the source images through image_inputs?
4. For masked edits, did I confirm the model supports masking before sending?
5. For multi-turn work, am I reusing the same session path across turns?
6. Did I avoid pasting base64 or assuming Markdown rendering works everywhere?
7. Did I give the user the exact saved path and any important caveat?

If the generated result is obviously a draft and the user wanted polish, offer the next concrete iteration rather than apologizing vaguely.