gemini-2.5-flash-image-stream

Generate images using Gemini 2.5 Flash Image in streaming mode via SSE. The endpoint returns newline-delimited Server-Sent Events. Thinking chunks (thought=true) arrive first, followed by the image chunk containing inlineData, and finally a usage metadata chunk.

POST /v1beta/models/gemini-2.5-flash-image:streamGenerateContent

cURL

cURL

curl --request POST \
  --url 'https://www.anyfast.ai/v1beta/models/gemini-2.5-flash-image:streamGenerateContent?key=<token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "contents": [
    {
      "role": "user",
      "parts": [
        {
          "text": "Generate an image of a sunset over mountains"
        }
      ]
    }
  ],
  "generationConfig": {
    "responseModalities": [
      "TEXT",
      "IMAGE"
    ],
    "imageConfig": {
      "aspectRatio": "16:9",
      "imageSize": "1K"
    }
  }
}
'

import requests

url = "https://www.anyfast.ai/v1beta/models/gemini-2.5-flash-image:streamGenerateContent"

payload = {
    "contents": [
        {
            "role": "user",
            "parts": [{ "text": "Generate an image of a sunset over mountains" }]
        }
    ],
    "generationConfig": {
        "responseModalities": ["TEXT", "IMAGE"],
        "imageConfig": {
            "aspectRatio": "16:9",
            "imageSize": "1K"
        }
    }
}
headers = {"Content-Type": "application/json"}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {'Content-Type': 'application/json'},
  body: JSON.stringify({
    contents: [
      {role: 'user', parts: [{text: 'Generate an image of a sunset over mountains'}]}
    ],
    generationConfig: {
      responseModalities: ['TEXT', 'IMAGE'],
      imageConfig: {aspectRatio: '16:9', imageSize: '1K'}
    }
  })
};

fetch('https://www.anyfast.ai/v1beta/models/gemini-2.5-flash-image:streamGenerateContent', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://www.anyfast.ai/v1beta/models/gemini-2.5-flash-image:streamGenerateContent",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'contents' => [
        [
                'role' => 'user',
                'parts' => [
                                [
                                                                'text' => 'Generate an image of a sunset over mountains'
                                ]
                ]
        ]
    ],
    'generationConfig' => [
        'responseModalities' => [
                'TEXT',
                'IMAGE'
        ],
        'imageConfig' => [
                'aspectRatio' => '16:9',
                'imageSize' => '1K'
        ]
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://www.anyfast.ai/v1beta/models/gemini-2.5-flash-image:streamGenerateContent"

	payload := strings.NewReader("{\n  \"contents\": [\n    {\n      \"role\": \"user\",\n      \"parts\": [\n        {\n          \"text\": \"Generate an image of a sunset over mountains\"\n        }\n      ]\n    }\n  ],\n  \"generationConfig\": {\n    \"responseModalities\": [\n      \"TEXT\",\n      \"IMAGE\"\n    ],\n    \"imageConfig\": {\n      \"aspectRatio\": \"16:9\",\n      \"imageSize\": \"1K\"\n    }\n  }\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://www.anyfast.ai/v1beta/models/gemini-2.5-flash-image:streamGenerateContent")
  .header("Content-Type", "application/json")
  .body("{\n  \"contents\": [\n    {\n      \"role\": \"user\",\n      \"parts\": [\n        {\n          \"text\": \"Generate an image of a sunset over mountains\"\n        }\n      ]\n    }\n  ],\n  \"generationConfig\": {\n    \"responseModalities\": [\n      \"TEXT\",\n      \"IMAGE\"\n    ],\n    \"imageConfig\": {\n      \"aspectRatio\": \"16:9\",\n      \"imageSize\": \"1K\"\n    }\n  }\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://www.anyfast.ai/v1beta/models/gemini-2.5-flash-image:streamGenerateContent")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Content-Type"] = 'application/json'
request.body = "{\n  \"contents\": [\n    {\n      \"role\": \"user\",\n      \"parts\": [\n        {\n          \"text\": \"Generate an image of a sunset over mountains\"\n        }\n      ]\n    }\n  ],\n  \"generationConfig\": {\n    \"responseModalities\": [\n      \"TEXT\",\n      \"IMAGE\"\n    ],\n    \"imageConfig\": {\n      \"aspectRatio\": \"16:9\",\n      \"imageSize\": \"1K\"\n    }\n  }\n}"

response = http.request(request)
puts response.read_body

200

{
  "candidates": [
    {
      "content": {
        "role": "model",
        "parts": [
          {
            "inlineData": {
              "mimeType": "image/png",
              "data": "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg=="
            }
          }
        ]
      }
    }
  ],
  "usageMetadata": {
    "trafficType": "ON_DEMAND"
  },
  "modelVersion": "gemini-2.5-flash-image"
}

{
  "error": {
    "code": 123,
    "message": "<string>",
    "status": "<string>"
  }
}

{
  "error": {
    "code": 123,
    "message": "<string>",
    "status": "<string>"
  }
}

{
  "error": {
    "code": 123,
    "message": "<string>",
    "status": "<string>"
  }
}

Query Parameters

key · string · required

API Key

alt · enum<string>

Set to sse for explicit Server-Sent Events mode (optional, streaming is the default behaviour of this endpoint)

Available options: sse

Body

application/json

contents · object[] · required

Array of conversation turns. Each turn has a role and parts. A part can be a text prompt, or an inline_data image (base64). To use a reference image, include both a text part and an inline_data part in the same parts array.

Show child attributes

Example:

[
  {
    "role": "user",
    "parts": [
      {
        "text": "Generate an image of a sunset over mountains"
      }
    ]
  }
]

generationConfig · object · required

Show child attributes

Response

200

application/json

Streaming SSE response. Each line starts with "data:" followed by a JSON chunk. Three chunk types are delivered in order: (1) Thinking chunks — parts[0].thought is true; (2) Image chunk — parts[0].inlineData contains mimeType and base64 data (camelCase); (3) Final usage chunk — top-level usageMetadata with thoughtsTokenCount.

A single SSE chunk. Three variants are possible: thinking chunk (parts[].thought=true), image chunk (parts[].inlineData), or usage chunk (no candidates).

candidates · object[]

Present in thinking and image chunks; absent in the final usage chunk.

Show child attributes

usageMetadata · object

Token usage. Final chunk contains full details including thoughtsTokenCount.

Show child attributes

modelVersion · string

Example:

"gemini-2.5-flash-image"

createTime · string

Example:

"2025-01-01T00:00:00Z"

responseId · string

Example:

"abc123"