nano-banana-builder by chongdashu

---
name: nano-banana-builder
description: >
  Build full-stack web applications powered by Google Gemini's Nano Banana & Nano Banana Pro
  image generation APIs. Use when creating Next.js image generators, editors, galleries,
  or any web app that integrates gemini-2.5-flash-image or gemini-3-pro-image-preview models.
  Covers React components, server actions, API routes, storage, rate limiting, and
  production deployment patterns.
---

# Nano Banana Builder

Build production-ready web applications powered by Google's Nano Banana image generation APIs—creating everything from simple text-to-image generators to sophisticated iterative editors with multi-turn conversation.

---

## CRITICAL: Exact Model Names

**Use ONLY these exact model strings. Do not invent, guess, or add date suffixes.**

| Model String (use exactly) | Alias | Use Case |
|---------------------------|-------|----------|
| `gemini-2.5-flash-image` | Nano Banana | Fast iterations, drafts, high volume |
| `gemini-3-pro-image-preview` | Nano Banana Pro | Quality output, text rendering, 2K |

**Common mistakes to avoid:**
- ❌ `gemini-2.5-flash-preview-05-20` — wrong, date suffixes are for text models
- ❌ `gemini-2.5-pro-image` — wrong, 2.5 Pro doesn't do image generation
- ❌ `gemini-3-flash-image` — wrong, doesn't exist
- ❌ `gemini-pro-vision` — wrong, that's for image *input*, not generation

**The only valid image generation models are `gemini-2.5-flash-image` and `gemini-3-pro-image-preview`.**

---

## Philosophy: Conversational Image Generation

Nano Banana isn't just another image API—it's **conversational by design**. The core insight is that image generation works best as a dialogue, not a one-shot prompt.

**Think of it as working with an AI art director**:
- **Iterative refinement** → Build up images through conversation, not perfection in one prompt
- **Context awareness** → The model "remembers" previous generations and edits
- **Natural language editing** → Describe changes conversationally, not with parameters

### Before Building, Ask

- **What's the primary use case?** Text-to-image generation? Image editing? Multi-image composition? Style transfer?
- **Which model fits the need?** Nano Banana (speed/iterations) or Nano Banana Pro (quality/complex prompts)?
- **What's the user journey?** Single generation? Iterative refinement? Gallery browsing?
- **What are production constraints?** Rate limits? Storage? Cost per image? User volume?

### Core Principles

1. **Conversation over configuration**: Leverage Nano Banana's iterative editing rather than complex parameter UIs
2. **Model selection matters**: Use `gemini-2.5-flash-image` for speed/iterations, `gemini-3-pro-image-preview` for quality/complexity
3. **State as conversation history**: Track generations as chat messages to enable multi-turn editing
4. **Rate limit awareness**: Image generation has strict quotas—implement queuing and caching
5. **Storage strategy**: Store generated images (Vercel Blob/S3), not just inline base64

### Model Selection Framework

Choose based on use case:

| Use Case | Model | Why |
|----------|-------|-----|
| Rapid iterations, drafts | `gemini-2.5-flash-image` | Fast (2-5s), lower cost per image |
| Final output, quality | `gemini-3-pro-image-preview` | Superior quality, thinking, text rendering |
| Text-heavy images | `gemini-3-pro-image-preview` | Best typography, 2K resolution |
| Multi-turn editing | Either | Both support conversational editing |
| High volume | `gemini-2.5-flash-image` | Lower cost, faster throughput |

---

## Quick Start

### Basic Server Action

```typescript
// app/actions/generate.ts
'use server'

import { google } from '@ai-sdk/google'
import { generateText } from 'ai'

export async function generateImage(prompt: string) {
  const result = await generateText({
    model: google('gemini-2.5-flash-image'),
    prompt,
    providerOptions: {
      google: {
        responseModalities: ['IMAGE'],
        imageConfig: { aspectRatio: '16:9' }
      }
    }
  })

  return result.files[0] // { base64, uint8Array, mediaType }
}
```

### Client Component with useChat

```typescript
// app/components/ImageGenerator.tsx
'use client'

import { useChat } from '@ai-sdk/react'

export function ImageGenerator() {
  const { append, messages, isLoading } = useChat({
    api: '/api/generate'
  })

  return (
    <div>
      {messages.map(m => (
        <div key={m.id}>
          {m.parts?.map((part, i) =>
            part.type === 'image' && (
              <img key={i} src={part.url} alt="Generated" />
            )
          )}
        </div>
      ))}

      <button
        disabled={isLoading}
        onClick={() => append({
          role: 'user',
          content: 'A futuristic cityscape at dusk'
        })}
      >
        Generate
      </button>
    </div>
  )
}
```

---

## Advanced Implementation

For complete implementations including:
- **Server Actions** with model selection, storage, and error handling
- **API Routes** with streaming responses
- **Client Components** with iterative editing and galleries
- **Advanced Patterns** like multi-image composition and batch generation

See **references/advanced-patterns.md**

---

## Configuration & Operations

For detailed configuration and operational concerns:
- **Provider Options** (responseModalities, imageConfig, thinkingConfig)
- **Storage Strategy** (Vercel Blob, S3/R2 implementations)
- **Rate Limiting** (Upstash Redis patterns, quota management)
- **Cost Optimization** strategies

See **references/configuration.md**

---

## Anti-Patterns to Avoid

❌ **Inventing model names or adding date suffixes**:
Why wrong: Image generation models have specific names; date suffixes like `-preview-05-20` are for text models only
Better: Use exactly `gemini-2.5-flash-image` or `gemini-3-pro-image-preview` — no variations

❌ **Using Gemini 2.5 Pro for images**:
Why wrong: Gemini 2.5 Pro doesn't generate images directly
Better: Use `gemini-2.5-flash-image` or `gemini-3-pro-image-preview`

❌ **Storing only base64 in database**:
Why wrong: Blobs database, expensive storage, slow retrieval
Better: Store in object storage (Vercel Blob/S3), save URL only

❌ **No rate limit handling**:
Why wrong: Will hit 429 errors in production, poor UX
Better: Implement rate limiting with user-friendly error messages

❌ **Ignoring multi-turn context**:
Why wrong: Wastes Nano Banana's conversational editing strength
Better: Track chat history for iterative refinement

❌ **Hardcoding API keys client-side**:
Why wrong: Exposes credentials, security risk
Better: Use server actions / API routes with environment variables

❌ **Using wrong aspect ratio**:
Why wrong: 21:9 on 1:1 request wastes tokens, unexpected crop
Better: Match aspect ratio to intended use case

❌ **No loading states**:
Why wrong: Image generation takes 5-30s, users think it's broken
Better: Show progress indicators and estimated wait time

❌ **Generating on every keystroke**:
Why wrong: Wastes quota, slow response
Better: Debounce prompts, require explicit action

---

## Variation Guidance

**IMPORTANT**: Every app should feel uniquely designed for its specific purpose.

**Vary across dimensions**:
- **UI Style**: Minimal, brutalist, playful, professional, dark, light
- **Color Scheme**: Warm, cool, monochrome, vibrant, muted
- **Layout**: Single page, multi-step wizard, sidebar, grid, list
- **Interaction**: Click-to-generate, drag-and-drop, real-time typing, batch

**Avoid overused patterns**:
- ❌ Default Tailwind purple gradients
- ❌ Generic "AI startup" aesthetic
- ❌ Same component libraries for every project
- ❌ Inter/Roboto fonts without thought

**Context should drive design**:
- **Meme generator** → Bold, fun, casual
- **Product mockup tool** → Clean, professional, grid-based
- **Art exploration** → Gallery-first, visual-heavy
- **Brand asset creator** → Polished, template-guided

---

## Environment Setup

```bash
# .env.local
GEMINI_API_KEY=your_api_key_here

# For Vercel Blob storage
BLOB_READ_WRITE_TOKEN=your_vercel_token

# For S3 (optional)
S3_BUCKET=your-bucket
S3_ENDPOINT=https://your-endpoint.r2.cloudflarestorage.com
S3_ACCESS_KEY_ID=your_key
S3_SECRET_ACCESS_KEY=your_secret

# For Upstash rate limiting (optional)
UPSTASH_REDIS_REST_URL=your_url
UPSTASH_REDIS_REST_TOKEN=your_token
```

```bash
# Install dependencies
npm install @ai-sdk/google ai @ai-sdk/react @vercel/blob

# Or if using separate packages
npm install google-genai
```

---

## Remember

**Nano Banana enables conversational image generation that feels like working with a creative partner, not a tool.**

The best apps:
- Leverage multi-turn editing for refinement
- Choose models intentionally (speed vs quality)
- Handle rate limits gracefully
- Store images efficiently
- Provide great loading states
- Feel uniquely designed for their purpose

You're building more than an image generator—you're creating a creative experience. Design it thoughtfully.