| name | nano-banana-pro-openrouter |
| description | Generate or edit images via OpenRouter with the Gemini 3 Pro Image model. Use for prompt-only image generation, image edits, and multi-image compositing; supports 1K/2K/4K output. |
| metadata | {"emoji":"🍌","requires":{"bins":["uv"],"env":["OPENROUTER_API_KEY"]},"primaryEnv":"OPENROUTER_API_KEY"} |
Nano Banana Pro OpenRouter
Overview
Generate or edit images with OpenRouter using the google/gemini-3-pro-image-preview model. Support prompt-only generation, single-image edits, and multi-image composition.
Prompt-only generation
uv run {baseDir}/scripts/generate_image.py \
--prompt "A cinematic sunset over snow-capped mountains" \
--filename sunset.png
Edit a single image
uv run {baseDir}/scripts/generate_image.py \
--prompt "Replace the sky with a dramatic aurora" \
--input-image input.jpg \
--filename aurora.png
Compose multiple images
uv run {baseDir}/scripts/generate_image.py \
--prompt "Combine the subjects into a single studio portrait" \
--input-image face1.jpg \
--input-image face2.jpg \
--filename composite.png
Resolution
- Use
--resolution with 1K, 2K, or 4K.
- Default is
1K if not specified.
System prompt customization
The skill reads an optional system prompt from assets/SYSTEM_TEMPLATE. This allows you to customize the image generation behavior without modifying code.
Behavior and constraints
- Accept up to 3 input images via repeated
--input-image.
--filename accepts relative paths (saves to current directory) or absolute paths.- If multiple images are returned, append
-1, -2, etc. to the filename.
- Print
MEDIA: <path> for each saved image. Do not read images back into the response.
Troubleshooting
If the script exits non-zero, check stderr against these common blockers:
| Symptom | Resolution |
|---|
OPENROUTER_API_KEY is not set | Ask the user to set it. PowerShell: $env:OPENROUTER_API_KEY = "sk-or-..." / bash: export OPENROUTER_API_KEY="sk-or-..." |
uv: command not found or not recognized | macOS/Linux: curl -LsSf https://astral.sh/uv/install.sh | sh. Windows: powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex". Then restart the terminal. |
AuthenticationError / HTTP 401 | Key is invalid or has no credits. Verify at https://openrouter.ai/settings/keys. |
For transient errors (HTTP 429, network timeouts), retry once after 30 seconds. Do not retry the same error more than twice — surface the issue to the user instead.
