nanobanana

name	nanobanana
description	Generate images from a text prompt via OpenRouter's image generation API (Nano Banana / Gemini Flash Image). Displays the result inside the widget and saves to disk for download.
version	0.2.4
type	extension
runtime	python3
entry	plugin.py
permissions	["net","tool","route","widget","read_settings"]
env_from_settings	["OPENROUTER_API_KEY"]
when_to_use	User wants to generate or render an image from a text description, right now, inside the web UI. Also saves the image to disk so it can be downloaded.
ui_tab	{"tab_id":"widget","title":"Nano Banana","icon":"image","render":{"kind":"declarative","schema_version":1,"components":[{"type":"form","title":"Generate an image","target":"result","route":"generate","method":"POST","job":true,"status_route":"status","interval_ms":1500,"max_ticks":120,"submit_label":"Generate","fields":[{"name":"prompt","label":"Prompt","type":"textarea","required":true},{"name":"model","label":"Model","type":"select","default":"google/gemini-3.1-flash-image-preview","options":[{"value":"google/gemini-3.1-flash-image-preview","label":"Nano Banana (Gemini 3.1 Flash)"},{"value":"google/gemini-3-pro-image-preview","label":"Nano Banana Pro (Gemini 3 Pro)"}]}]},{"type":"status","target":"result","idle":"Enter a prompt and press Generate.","loading":"Generating image…","success":"Done.","error":"Generation failed."},{"type":"markdown","target":"result","path":"error"},{"type":"image","target":"result","path":"image_url","label":"Generated image","alt":"Generated image"},{"type":"file","target":"result","path":"download_url","label":"Download image"}]}}

Nano Banana image generation widget

An extension skill that renders a generator inside the Widgets tab. Type a prompt, pick a model, press Generate, and the image appears directly in the card. From v0.2.0 the image is also saved to disk and a Download image button appears below it.

Backed by OpenRouter's image generation endpoint. Two Google models available: the default is Nano Banana (google/gemini-3.1-flash-image-preview).

Persistence and download (v0.2.0)

From v0.2.0, every generation saves the image to the skill's private state directory: ~/Ouroboros/data/state/skills/nanobanana/img_<12 hex chars>.<ext>.

Two separate routes serve the image:

• GET /api/extensions/nanobanana/media?image_id=... — inline preview (Content-Disposition: inline), used by the <img> tag in the widget.
• GET /api/extensions/nanobanana/download?image_id=... — attachment download, sets proper filename so the file saves as img_<hex>.png.

Neither route requires the OPENROUTER_API_KEY grant — they serve files already written to disk. A generated image stays accessible even if you later revoke the generation grant.

Setup

1. Put your OpenRouter API key into Ouroboros Settings → Providers → OpenRouter.
2. Run review_skill(skill="nanobanana") and wait for a PASS verdict.
3. On the Skills tab, click Grant access for OPENROUTER_API_KEY. The grant is content-hash-bound: any edit to this skill invalidates it.
4. Enable the skill on the Skills tab.
5. Open the Widgets tab — the Nano Banana card appears.

Usage

• Via the widget: type a prompt, optionally switch model, press Generate. The image appears below the form; the Download image button saves it locally.
• Via the agent: call ext_<token>_nanobanana_generate(prompt="..."). Returns JSON with file_path, image_id, image_url, download_url, bytes, mime, model on success, or error.

Security model

• OPENROUTER_API_KEY only reaches the extension after owner grants access on the Skills tab. Grant is bound to current content hash.
• Key read exclusively via PluginAPI.get_settings — never via os.environ.
• Single-host allowlist (openrouter.ai). Cross-host redirects refused.
• Download/media routes: two-layer path traversal defense (strict regex + Path.resolve().relative_to(state_dir)).

Limits

• Single image per request.
• Timeout: 60 seconds (dispatched via asyncio.to_thread).
• Prompts over 4 KB are truncated.
• State directory is not auto-cleaned. Delete old files freely — not part of the content hash, so deletion does not invalidate the grant.