Dart dart:io: POST /v1/images on Sume from a command-line script

A server-side or command-line Dart tool can call the image API with the SDK alone.

The request is the same in every language: POST https://api.sume.com/v1/images with a bearer key from SUME_API_KEY, a JSON body with model, prompt and aspect_ratio, and a client timeout above the route's 30-second wait. The route defaults to mode: "sync", so the status code decides what you do next (docs read 2026-10-07):

Status codes to branch on

Dart code

Save as gen.dart and run SUME_API_KEY=... dart run gen.dart. Only the Dart SDK is needed.

import 'dart:convert';
import 'dart:io';

Future<void> main() async {
  final key = Platform.environment['SUME_API_KEY'];
  if (key == null || key.isEmpty) {
    stderr.writeln('SUME_API_KEY missing');
    exit(1);
  }
  final client = HttpClient()..connectionTimeout = const Duration(seconds: 10);
  final req = await client.postUrl(Uri.parse('https://api.sume.com/v1/images'));
  req.headers.set('Authorization', 'Bearer $key');
  req.headers.contentType = ContentType.json;
  req.write(jsonEncode({
    'model': 'bytedance-seed/seedream-5-lite',
    'prompt': 'matte ceramic mug on a white sweep, soft shadow',
    'aspect_ratio': '16:9',
  }));
  final res = await req.close().timeout(const Duration(seconds: 40));
  final text = await res.transform(utf8.decoder).join();
  if (res.statusCode == 200) {
    print('done: ${jsonDecode(text)['data'][0]['url']}');
  } else if (res.statusCode == 202) {
    print('queued, follow status_url: $text');
  } else {
    print('error ${res.statusCode}: $text');
  }
  client.close();
}

Notes

Keep the key on the server. Do not ship SUME_API_KEY inside a Flutter app; call your own backend, which calls Sume.

connectionTimeout covers only the connect step; the .timeout(...) on the response covers the sync wait.

One bytedance-seed/seedream-5-lite image is $0.04375 billed (list $0.035 x 1.25). Prices here are Sume's list-times-1.25 figures. The catalog states the billable formula as "list × 1.25 → ceil usd cents", so treat the dollar amounts as the pre-rounding value and read the exact charge from billable_amount_usd_micros in the submit envelope. Failed or cancelled generations are not billed.

Sources: Sume Image API docs and Jobs and results (read 2026-10-07).