git:20260624.0a2f9fa to git:20260710.0115f49

4 added, 4 removed. Audit A to A.

---

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:

skill-author: 'Marie-Lynne Block'

emoji: 🍌

requires:

- Python 3.10+

- uv

- OpenRouter API key

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.

Run commands from this skill folder so bundled scripts and assets resolve correctly.

### Prompt-only generation

```

uv run scripts/generate_image.py \

--prompt "A cinematic sunset over snow-capped mountains" \

--filename sunset.png

```

### Edit a single image

```

uv run scripts/generate_image.py \

--prompt "Replace the sky with a dramatic aurora" \

--input-image input.jpg \

--filename aurora.png

```

### Compose multiple images

```

uv run 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

+ ## System prompt customisation

- The skill reads an optional system prompt from `assets/SYSTEM_TEMPLATE`. This allows you to customize the image generation behavior without modifying code.

+ The skill reads an optional system prompt from `assets/SYSTEM_TEMPLATE`. This allows you to customise the image generation behaviour without modifying code.

- ## Behavior and constraints

+ ## Behaviour 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: <code>curl -LsSf https://astral.sh/uv/install.sh | sh</code>. Windows: <code>powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"</code>. Then restart the terminal. |

+ | `uv: command not found` or not recognised | macOS/Linux: <code>curl -LsSf https://astral.sh/uv/install.sh | sh</code>. Windows: <code>powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"</code>. 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.