nano-banana + Gemini key

The nano-banana skill generates images by calling the Gemini CLI’s nanobanana extension, which hits Google’s gemini-2.5-flash-image (or gemini-3-pro-image-preview) endpoints. With the free Gemini API tier, you get ~500 images/day — plenty for personal use.

What’s installed

Component	Where	Notes
@google/gemini-cli	Global npm install	npm install -g @google/gemini-cli
nanobanana extension	~/.gemini/extensions/nanobanana/	Installed via gemini extensions install
nano-banana skill	~/.claude/skills/nano-banana/SKILL.md	The Claude Code wrapper
GEMINI_API_KEY	User env var (setx) + ~/.nano-banana/.env	Persisted across reboots
Extension enablement	~/.gemini/extensions/extension-enablement.json	Must NOT have "overrides": ["/C:/Users/justi/*"]

Verify it works

gemini --yolo -p "/generate 'a single yellow banana on white background'"

If everything’s good, an image appears in ./nanobanana-output/. If you see “GEMINI_API_KEY not set”, the env var didn’t propagate — open a new terminal.

Get a Gemini API key

If you ever rotate yours:

1. Visit aistudio.google.com/apikey
2. Sign in with any Google account (no payment method required)
3. Click “Create API key”
4. Copy the key (starts with AIza...)
5. Update it in two places:
   • User env var: setx GEMINI_API_KEY "your-key"
   • ~/.nano-banana/.env: edit the file

Caution

The API key is sensitive. Don’t commit it to git, don’t paste in public chats, don’t embed in screenshots. Treat like a password.

The extension enablement gotcha

A known quirk during setup: gemini extensions list returns empty even when extensions are installed. Cause: the extension has an “overrides” entry in ~/.gemini/extensions/extension-enablement.json that disables it for your home directory.

Fix: edit the file so the extension’s overrides array is empty ([]) or remove the entry entirely.

{
  "nanobanana": {
    "overrides": []
  }
}

That re-enables it globally.

Free-tier limits

As of May 2026:

• gemini-2.5-flash-image: ~500 images/day, free
• gemini-3-pro-image-preview: ~150 images/day, free (higher quality)
• Resolution: up to 4K
• Aspect ratios: 1:1, 16:9, 9:16, 4:3, 3:2, 21:9 etc.

Hard rate limits (per minute) exist but you’ll hit the daily cap first if you’re bulk-generating.

Cost if you exceed free tier

Per Google’s pricing as of mid-2026:

• ~$0.04 per 1K image (flash)
• ~$0.14 per 4K image (pro)

Trivial unless you batch-generate at scale.

Models the skill knows about

The skill accepts model aliases:

Alias	Real model	Use for
flash (default)	gemini-2.5-flash-image	Daily use, speed, volume
pro	gemini-3-pro-image-preview	High-quality featured images, 4K

Override per call: gemini --yolo -p "/generate '...' --model pro"

Where outputs go

Default: ./nanobanana-output/ in whatever directory you ran the command from.

In the Content Engine workflow, outputs get moved to 80-Content/assets/[slug]/. In the Visual Journal workflow, into 10-Daily/ next to the day’s note.

When the skill triggers

The skill is set up to be invoked for ANY image request the user makes. The frontmatter:

description: REQUIRED for all image generation requests. Generate and edit images using Nano Banana (Gemini CLI). Handles blog featured images, YouTube thumbnails, icons, diagrams, patterns, illustrations, photos, visual assets, graphics, artwork, pictures. Use this skill whenever the user asks to create, generate, make, draw, design, or edit any image or visual content.

If you ever want Claude to use a different image tool, edit this frontmatter.