Send message (OpenAI format).

OpenAI-compatible chat completion response.

Non-streaming (stream: false or omitted): Returns a single JSON object with the complete response.

Streaming (stream: true): Returns Server-Sent Events (SSE) with text/event-stream content type.

Each SSE event is prefixed with data: followed by a JSON object:

data: {"id":"chatcmpl-abc123","object":"chat.completion.chunk","created":1743037634,"model":"gpt-4","choices":[{"index":0,"delta":{"content":"Hello"},"finish_reason":null}]}

The stream ends with:

data: [DONE]

Key fields per chunk:

• id: unique completion ID
• object: always chat.completion.chunk
• created: Unix timestamp
• choices[0].delta.content: incremental text fragment
• choices[0].finish_reason: null during stream, stop on final chunk

JavaScript client example:

const response = await fetch(
  'https://app.customgpt.ai/api/v1/projects/{projectId}/chat/completions',
  {
    method: 'POST',
    headers: {
      'Authorization': 'Bearer YOUR_API_KEY',
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({
      messages: [{ role: 'user', content: 'Hello' }],
      stream: true
    })
  }
);

const reader = response.body.getReader();
const decoder = new TextDecoder();

while (true) {
  const { done, value } = await reader.read();
  if (done) break;

  const lines = decoder.decode(value).split('\n');
  for (const line of lines) {
    if (!line.startsWith('data: ')) continue;
    const payload = line.slice(6);
    if (payload === '[DONE]') break;

    const chunk = JSON.parse(payload);
    const text = chunk.choices[0]?.delta?.content || '';
    process.stdout.write(text);
  }
}