> ## Documentation Index
> Fetch the complete documentation index at: https://docs.nanobananaapi.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Generate Image Callbacks (Nanobanana 2)

> When NanoBanana Generate-2 image generation tasks are completed, the system will send results to your provided callback URL via POST request

When you submit image generation tasks to the NanoBanana Generate-2 API (`/api/v1/nanobanana/generate-2`), you can set a callback address through the `callBackUrl` parameter. After the task is completed, the system will automatically push the results to your specified address.

## Callback Mechanism Overview

<Info>
  The callback mechanism eliminates the need for you to poll the API to query task status. The system will actively push task completion results to your server.
</Info>

### Callback Timing

The system will send callback notifications in the following situations:

* NanoBanana Generate-2 image generation task completed successfully
* NanoBanana Generate-2 image generation task failed
* Error occurred during task processing

### Callback Method

* **HTTP Method**: POST
* **Content Type**: application/json
* **Timeout Setting**: 15 seconds

## Callback Request Format

After task completion, the system will send a POST request to your `callBackUrl`. The actual response structure in production looks like the following:

<CodeGroup>
  ```json Success Callback Example theme={null}
  {
    "code": 200,
    "msg": "success",
    "data": {
      "taskId": "31ce2c17b257492959d62279e6d01a54",
      "paramJson": "{...}",
      "completeTime": "2026-02-27 24:00:00",
      "response": {
        "originImageUrl": null,
        "resultImageUrl": "https://tempfile.aiquickdraw.com/gemini-preview/xxxxxx.jpeg"
      },
      "successFlag": 1,
      "errorCode": null,
      "errorMessage": null,
      "operationType": "nano-banana-2_1k",
      "createTime": "2026-02-27 24:00:00"
    }
  }
  ```

  ```json Sensitive Content Failure Callback Example theme={null}
  {
    "code": 200,
    "msg": "success",
    "data": {
      "taskId": "7dc1089163a9b00eaa4719b8862ddade",
      "paramJson": "{}",
      "completeTime": "2026-01-27 24:00:00",
      "response": null,
      "successFlag": 3,
      "errorCode": 422,
      "errorMessage": "The input or output was flagged as sensitive. Please try again with different inputs. (E005) (uIJ6l3ruRD)",
      "operationType": "nano-banana-2_1k",
      "createTime": "2026-02-27 24:00:00"
    }
  }
  ```
</CodeGroup>

## Field and Status Description

<ParamField path="code" type="integer" required>
  Top-level `code` field indicating whether the callback request itself is successful.\
  In the current implementation it is typically **200** for normal callbacks.\
  Whether the generation task is successful should be determined by `data.successFlag` and `data.errorCode`.
</ParamField>

<ParamField path="msg" type="string" required>
  Status message, usually `"success"`. For detailed failure reasons, refer to `data.errorMessage`.
</ParamField>

<ParamField path="data.taskId" type="string" required>
  Task ID, consistent with the `taskId` returned when you submitted the task.
</ParamField>

<ParamField path="data.successFlag" type="integer" required>
  Generation status flag, with the same meaning as the **Get Task Details** endpoint:

  | Value | Description                                                                                   |
  | ----- | --------------------------------------------------------------------------------------------- |
  | 0     | GENERATING - Task is currently being processed                                                |
  | 1     | SUCCESS - Image generated successfully; you can read `response.resultImageUrl` for the result |
  | 2     | CREATE\_TASK\_FAILED - Failed to create the task                                              |
  | 3     | GENERATE\_FAILED - Generation failed (for example flagged as sensitive content)               |
</ParamField>

<ParamField path="data.errorCode" type="integer">
  Error code when `successFlag` ≠ 1, indicating the failure reason, for example:

  * `422`: The input or output was flagged as sensitive content (see the sensitive content failure example above)
</ParamField>

<ParamField path="data.errorMessage" type="string">
  Error message string, usually containing more detailed description for the failure.
</ParamField>

<ParamField path="data.response.resultImageUrl" type="string">
  Generated image URL on our server. Only present when `successFlag = 1` and generation succeeds.
</ParamField>

<ParamField path="data.paramJson" type="string">
  JSON string snapshot of the request parameters for this task. Useful for debugging and auditing.
</ParamField>

<ParamField path="data.operationType" type="string">
  Internal model/config identifier, for example `"nano-banana-2_1k"`.
</ParamField>

<ParamField path="data.createTime" type="string">
  Task creation time.
</ParamField>

<ParamField path="data.completeTime" type="string">
  Task completion time.
</ParamField>

## Callback Reception Examples

Here are example codes for receiving NanoBanana Generate-2 callbacks in popular programming languages:

<Tabs>
  <Tab title="Node.js">
    ```javascript theme={null}
    const express = require('express');
    const fs = require('fs');
    const https = require('https');
    const app = express();

    app.use(express.json());

    app.post('/nanobanana-generate-2-callback', (req, res) => {
      const { code, msg, data } = req.body;
      const {
        taskId,
        successFlag,
        errorCode,
        errorMessage,
        response
      } = data || {};
      const resultImageUrl = response?.resultImageUrl || '';
      
      console.log('Received NanoBanana Generate-2 callback:', {
        taskId,
        httpCode: code,
        successFlag,
        errorCode,
        message: msg,
        errorMessage
      });
      
      if (successFlag === 1) {
        // Task completed successfully
        console.log('NanoBanana Generate-2 task completed successfully');
        console.log(`Generated image URL: ${resultImageUrl}`);
        
        // Download the generated image
        if (resultImageUrl) {
          downloadFile(resultImageUrl, `nanobanana_generate2_result_${taskId}.jpg`)
            .then(() => console.log('Generated image downloaded successfully'))
            .catch(err => console.error('Failed to download generated image:', err));
        }
      } else {
        // Task failed
        console.log('NanoBanana Generate-2 task failed:', errorMessage || msg || 'Unknown error');
        
        if (errorCode === 422) {
          console.log('Content/safety checks failed - please adjust your prompt or inputs');
        }
      }
      
      // Return 200 status code to confirm callback receipt
      res.status(200).json({ status: 'received' });
    });

    // Helper function: download file
    function downloadFile(url, filename) {
      return new Promise((resolve, reject) => {
        const file = fs.createWriteStream(filename);
        
        https.get(url, (response) => {
          if (response.statusCode === 200) {
            response.pipe(file);
            file.on('finish', () => {
              file.close();
              resolve();
            });
          } else {
            reject(new Error(`HTTP ${response.statusCode}`));
          }
        }).on('error', reject);
      });
    }

    app.listen(3000, () => {
      console.log('NanoBanana Generate-2 callback server running on port 3000');
    });
    ```
  </Tab>

  <Tab title="Python">
    ```python theme={null}
    from flask import Flask, request, jsonify
    import requests
    import os

    app = Flask(__name__)

    @app.route('/nanobanana-generate-2-callback', methods=['POST'])
    def handle_callback():
        data = request.json
        
        code = data.get('code')
        msg = data.get('msg')
        callback_data = data.get('data', {})
        task_id = callback_data.get('taskId')
        success_flag = callback_data.get('successFlag')
        error_code = callback_data.get('errorCode')
        error_message = callback_data.get('errorMessage')
        response_data = callback_data.get('response') or {}
        result_image_url = response_data.get('resultImageUrl')
        
        print("Received NanoBanana Generate-2 callback:")
        print(f"Task ID: {task_id}")
        print(f"HTTP code: {code}, successFlag: {success_flag}, errorCode: {error_code}")
        print(f"msg: {msg}, errorMessage: {error_message}")
        
        if success_flag == 1:
            # Task completed successfully
            print("NanoBanana Generate-2 task completed successfully")
            print(f"Generated image URL: {result_image_url}")
            
            # Download the generated image
            if result_image_url:
                try:
                    result_filename = f"nanobanana_generate2_result_{task_id}.jpg"
                    download_file(result_image_url, result_filename)
                    print(f"Generated image downloaded as {result_filename}")
                except Exception as e:
                    print(f"Failed to download generated image: {e}")
        else:
            # Task failed
            print(f"NanoBanana Generate-2 task failed: {error_message or msg}")
            
            if error_code == 422:
                print("Content/safety checks failed - please adjust your prompt or inputs")
        
        # Return 200 status code to confirm callback receipt
        return jsonify({'status': 'received'}), 200

    def download_file(url, filename):
        """Download file from URL and save locally"""
        response = requests.get(url, stream=True)
        response.raise_for_status()
        
        os.makedirs('downloads', exist_ok=True)
        filepath = os.path.join('downloads', filename)
        
        with open(filepath, 'wb') as f:
            for chunk in response.iter_content(chunk_size=8192):
                f.write(chunk)

    if __name__ == '__main__':
        app.run(host='0.0.0.0', port=3000)
    ```
  </Tab>

  <Tab title="PHP">
    ```php theme={null}
    <?php
    header('Content-Type: application/json');

    // Get POST data
    $input = file_get_contents('php://input');
    $data = json_decode($input, true);

    $code = $data['code'] ?? null;
    $msg = $data['msg'] ?? '';
    $callbackData = $data['data'] ?? [];

    $taskId = $callbackData['taskId'] ?? '';
    $successFlag = $callbackData['successFlag'] ?? null;
    $errorCode = $callbackData['errorCode'] ?? null;
    $errorMessage = $callbackData['errorMessage'] ?? '';
    $response = $callbackData['response'] ?? [];
    $resultImageUrl = $response['resultImageUrl'] ?? '';

    error_log("Received NanoBanana Generate-2 callback:");
    error_log("Task ID: $taskId");
    error_log("HTTP code: $code, successFlag: $successFlag, errorCode: $errorCode");
    error_log("msg: $msg, errorMessage: $errorMessage");

    if ($successFlag === 1) {
        // Task completed successfully
        error_log("NanoBanana Generate-2 task completed successfully");
        
        error_log("Generated image URL: $resultImageUrl");
        
        // Download the generated image
        if (!empty($resultImageUrl)) {
            try {
                $resultFilename = "nanobanana_generate2_result_{$taskId}.jpg";
                downloadFile($resultImageUrl, $resultFilename);
                error_log("Generated image downloaded as $resultFilename");
            } catch (Exception $e) {
                error_log("Failed to download generated image: " . $e->getMessage());
            }
        }
    } else {
        // Task failed
        error_log("NanoBanana Generate-2 task failed: " . ($errorMessage ?: $msg));
        
        if ($errorCode === 422) {
            error_log("Content/safety checks failed - please adjust your prompt or inputs");
        }
    }

    // Return 200 status code to confirm callback receipt
    http_response_code(200);
    echo json_encode(['status' => 'received']);

    function downloadFile($url, $filename) {
        $downloadDir = 'downloads';
        if (!is_dir($downloadDir)) {
            mkdir($downloadDir, 0755, true);
        }
        
        $filepath = $downloadDir . '/' . $filename;
        
        $fileContent = file_get_contents($url);
        if ($fileContent === false) {
            throw new Exception("Failed to download file from URL");
        }
        
        $result = file_put_contents($filepath, $fileContent);
        if ($result === false) {
            throw new Exception("Failed to save file locally");
        }
    }
    ?>
    ```
  </Tab>
</Tabs>

## Best Practices

<Tip>
  ### Callback URL Configuration Recommendations

  1. **Use HTTPS**: Ensure callback URL uses HTTPS protocol for secure data transmission
  2. **Verify Source**: Verify the legitimacy of request sources in callback handling
  3. **Idempotent Processing**: The same taskId may receive multiple callbacks, ensure processing logic is idempotent
  4. **Quick Response**: Callback handling should return 200 status code quickly to avoid timeout
  5. **Asynchronous Processing**: Complex business logic should be processed asynchronously to avoid blocking callback response
  6. **Timely Download**: Download image files promptly after receiving successful callbacks
</Tip>

<Warning>
  ### Important Reminders

  * Callback URL must be a publicly accessible address
  * Server must respond within 15 seconds, otherwise it will be considered timeout
  * After 3 consecutive retry failures, the system will stop sending callbacks
  * Ensure stability of callback handling logic to avoid callback failures due to exceptions
  * Parse `data.info.resultImageUrl` field properly to get the generated image URL
  * Need to handle multiple error status codes (400, 500, 501), implement complete error handling
  * Handle both success and failure scenarios appropriately
</Warning>

## Troubleshooting

If you haven't received callback notifications, please check the following:

<AccordionGroup>
  <Accordion title="Network Connection Issues">
    * Confirm callback URL is accessible from the public internet
    * Check firewall settings to ensure inbound requests are not blocked
    * Verify domain name resolution is correct
  </Accordion>

  <Accordion title="Server Response Issues">
    * Ensure server returns HTTP 200 status code within 15 seconds
    * Check server logs for error information
    * Verify interface path and HTTP method are correct
  </Accordion>

  <Accordion title="Content Format Issues">
    * Confirm received POST request body is in JSON format
    * Check if Content-Type is application/json
    * Verify JSON parsing is correct
  </Accordion>

  <Accordion title="Image Processing Issues">
    * Confirm image URL is accessible
    * Check image download permissions and network connection
    * Verify image save path and permissions
    * Implement reasonable image download and storage logic
  </Accordion>

  <Accordion title="Content Policy Issues">
    * Review content policy violation prompts in error messages
    * Adjust flagged prompt content
    * Ensure prompts comply with platform content guidelines
    * Check for sensitive or inappropriate content
  </Accordion>

  <Accordion title="Task Failure Issues">
    * Check if generation parameters are reasonable
    * Verify input image format and quality (for auto aspect ratio)
    * Confirm prompt length and format
    * Consider adjusting generation parameters and retry
  </Accordion>
</AccordionGroup>

## Alternative Solution

If you cannot use the callback mechanism, you can also use polling:

<Card title="Polling Query Results" icon="radar" href="/nanobanana-api/get-task-details">
  Use the get task details interface to periodically query task status, recommended every 30 seconds.
</Card>