Nano Banana images with Gemini CLI

Overview

Use Gemini CLI plus the Nano Banana extension to generate and edit images via slash commands. Outputs are saved to ./nanobanana-output/ for review or delivery.

Prerequisites

• Confirm Gemini CLI is installed: gemini --version

• Confirm the extension is installed: gemini extensions install https://github.com/gemini-cli-extensions/nanobanana

• Ensure an API key is set: NANOBANANA_GEMINI_API_KEY , NANOBANANA_GOOGLE_API_KEY , GEMINI_API_KEY , or GOOGLE_API_KEY

• Optional: set NANOBANANA_MODEL=gemini-3-pro-image-preview for Nano Banana Pro

• If MCP tools are blocked by policy, run with approvals: gemini --approval-mode yolo -p "..." or allow the MCP server with --allowed-mcp-server-names nanobanana

Workflow

• Identify the request type (generate, edit, restore, icon, pattern, story, diagram).

• Ensure any input images are in the current directory or the extension search paths.

• Start Gemini CLI in the working directory: gemini (or use gemini --approval-mode yolo -p "..." for one-shot runs)

• Run the appropriate command:

• /generate "prompt" --count=3 --styles="watercolor,sketch"

• /edit input.png "instruction" --preview

• /restore old_photo.jpg "instruction"

• /icon "prompt" --sizes="64,128,256"

• /pattern "prompt" --type="seamless"

• /story "prompt" --steps=4

• /diagram "prompt" --type="architecture"

• /nanobanana "freeform instruction"

• Collect outputs from ./nanobanana-output/ and share the file paths.

Troubleshooting

• If generate_image is denied by policy, re-run with --approval-mode yolo or allow MCP server nanobanana .

• If you see No valid API key found , set NANOBANANA_GEMINI_API_KEY (or NANOBANANA_GOOGLE_API_KEY , GEMINI_API_KEY , GOOGLE_API_KEY ) and retry.

Prompting Guidance

• Specify subject, style, medium, lighting, composition, color palette, and constraints.

• For consistent series, repeat style and include specific variation goals.

• Use --count , --styles , and --variations for systematic exploration.

• Use --preview only when interactive output is desired.

Files and Tools

• Use scripts/example.py to list output images or fetch the newest output.

• Use references/api_reference.md for command options and file-handling details.

• Use assets/example_asset.txt as a prompt template.