Gemini 3.1 Flash Lite Image (Stream)

Google’s Gemini 3.1 Flash Lite Image (Stream) for image generation via Gemini API. Real-time SSE delivery of thinking and image chunks.

Gemini 3.1 Flash Lite Image (Stream) generates images using Google’s Gemini 3.1 Flash Lite Image model through the native Gemini API via AnyFast. Responses are delivered in real-time using Server-Sent Events (SSE), with thinking chunks arriving first followed by the image data chunk.

Streaming requires a Direct group token. Select the Direct group when creating your token in the AnyFast console.

Key capabilities

• SSE Streaming — Real-time delivery of thinking and image chunks
• Thinking mode — Internal reasoning chunks (thought: true) stream before the final image
• Text-to-image — Generate images from text descriptions
• Image editing — Pass a reference image in inline_data alongside your text instruction
• Aspect ratio control — 1:1, 3:2, 2:3, 3:4, 4:3, 4:5, 5:4, 9:16, 16:9, 21:9
• Resolution control — Supports 1K (1024px). 2K and 4K are not supported.

SSE response format

The streaming endpoint returns newline-delimited SSE lines. Each line starts with data: followed by a JSON object. There are three chunk types:

1. Thinking chunks — Arrive first; parts[0].thought is true
2. Image chunk — Contains parts[0].inlineData with mimeType and base64 data (note: camelCase in stream response)
3. Final usage chunk — Contains top-level usageMetadata with thoughtsTokenCount and token details

data: {"candidates":[{"content":{"role":"model","parts":[{"text":"...","thought":true}]}}],"usageMetadata":{"trafficType":"ON_DEMAND"},"modelVersion":"gemini-3.1-flash-lite-image","createTime":"...","responseId":"..."}

data: {"candidates":[{"content":{"role":"model","parts":[{"inlineData":{"mimeType":"image/png","data":"<base64>"}}]}}],...}

data: {"usageMetadata":{"promptTokenCount":8,"candidatesTokenCount":1120,"totalTokenCount":1392,"trafficType":"ON_DEMAND","promptTokensDetails":[{"modality":"TEXT","tokenCount":8}],"candidatesTokensDetails":[{"modality":"IMAGE","tokenCount":1120}],"thoughtsTokenCount":264}}

In the streaming response, the image field is named inlineData (camelCase). In the non-streaming request body, the field is inline_data (snake_case). This is a native Gemini API behaviour.

Text-to-image example

cURL

curl "https://www.anyfast.ai/v1beta/models/gemini-3.1-flash-lite-image:streamGenerateContent?key=YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [
      {
        "role": "user",
        "parts": [
          { "text": "Generate an image of a sunset over mountains" }
        ]
      }
    ],
    "generationConfig": {
      "responseModalities": ["TEXT", "IMAGE"],
      "imageConfig": {
        "aspectRatio": "16:9",
        "imageSize": "1K"
      }
    }
  }'

Image editing example (with reference image)

Include both a text instruction and an inline_data reference image in the same parts array.

cURL

# First encode your image to base64:
# BASE64=$(base64 -i your_photo.jpg)
#
# Then send the request:
curl "https://www.anyfast.ai/v1beta/models/gemini-3.1-flash-lite-image:streamGenerateContent?key=YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [
      {
        "role": "user",
        "parts": [
          {
            "text": "Hi, this is a picture of me. Can you add a llama next to me?"
          },
          {
            "inline_data": {
              "mime_type": "image/jpeg",
              "data": "<YOUR_BASE64_ENCODED_IMAGE>"
            }
          }
        ]
      }
    ],
    "generationConfig": {
      "responseModalities": ["TEXT", "IMAGE"],
      "imageConfig": {
        "aspectRatio": "1:1",
        "imageSize": "1K"
      }
    }
  }'

Parameters

Parameter	Type	Required	Description
key	string	Yes	API key (query parameter)
alt	string	No	Set to sse for explicit SSE mode (optional, streaming is default)
contents[].parts[].text	string	Yes	Text prompt or instruction
contents[].parts[].inline_data.mime_type	string	No	Reference image type: image/jpeg, image/png, image/webp
contents[].parts[].inline_data.data	string	No	Base64-encoded reference image
generationConfig.responseModalities	array	Yes	["IMAGE"] or ["TEXT", "IMAGE"]
generationConfig.imageConfig.aspectRatio	string	No	1:1 / 3:2 / 2:3 / 3:4 / 4:3 / 4:5 / 5:4 / 9:16 / 16:9 / 21:9
generationConfig.imageConfig.imageSize	string	No	1K only. 2K and 4K are not supported.

API Reference

View the interactive API playground for Gemini 3.1 Flash Lite Image (Stream).