The Responses API supports streaming to receive tokens as they’re generated instead of waiting for the complete response. Set stream: true in your request, then read the response body as a stream of server-sent events (SSE). Each event contains a response chunk that you can display incrementally.
The Responses API is best supported on the Enterprise plan. Use https://enterprise.blackbox.ai as the base URL for full model availability and production reliability. The API is also available on standard plans at https://api.blackbox.ai, where it is currently experimental.
Basic Streaming Request
const response = await fetch('https://enterprise.blackbox.ai/v1/responses', {
method: 'POST',
headers: {
'Content-Type': 'application/json',
Authorization: `Bearer ${process.env.BLACKBOX_API_KEY}`,
},
body: JSON.stringify({
model: 'openai/gpt-5.3-codex',
input: [
{
type: 'message',
role: 'user',
content: 'Write a haiku about debugging code.',
},
],
stream: true,
}),
});
const reader = response.body.getReader();
const decoder = new TextDecoder();
while (true) {
const { done, value } = await reader.read();
if (done) break;
const chunk = decoder.decode(value);
const lines = chunk.split('\n');
for (const line of lines) {
if (line.startsWith('data:')) {
const data = line.substring(6).trim();
if (data) {
const event = JSON.parse(data);
if (event.type === 'response.output_text.delta') {
process.stdout.write(event.delta);
}
}
}
}
}
Streaming Events
The stream emits server-sent events in the following sequence:
| Event | Description |
|---|
response.created | Response initialized — signals the stream has started |
response.output_text.delta | Text chunk received — contains a delta field with the new text |
response.output_text.done | Text generation complete for the current output item |
response.completed | Full response complete, includes final usage statistics |
Event Payloads
response.output_text.delta
{
"type": "response.output_text.delta",
"delta": "Null pointer—"
}
response.completed
{
"type": "response.completed",
"response": {
"id": "resp_abc123",
"object": "response",
"model": "openai/gpt-5.3-codex",
"output": [
{
"type": "message",
"role": "assistant",
"content": [
{
"type": "output_text",
"text": "Null pointer—\nthe stack trace unfolds at dawn,\ncoffee grows cold."
}
]
}
],
"usage": {
"input_tokens": 12,
"output_tokens": 20
}
}
}
Request Parameters
Set to true to enable streaming. The response will be a stream of server-sent events instead of a single JSON object.
The model identifier to use. Example: openai/gpt-5.3-codex
Array of input messages with type, role, and content fields.
Next Steps
