Streaming

Replace <BASE_URL> using values from Endpoints.

Stream chat completion tokens using Server-Sent Events (SSE).

Enable streaming

Set "stream": true in the chat completions request body:

{
  "model": "deepseek/deepseek-chat",
  "messages": [{"role": "user", "content": "Count to five."}],
  "stream": true
}

Use stream: true for reasoning / long-thinking models. Non-streaming requests may be cut off by CDN (e.g. Cloudflare) ~100s first-byte limits. On the streaming path the gateway periodically sends SSE comment lines (: keepalive), which SDKs ignore.

Response format

Content-Type: text/event-stream
Each line: data: <json chunk>
Terminator: data: [DONE]

Example (data: JSON is usually one line on the wire; line breaks here are for readability):

data: {
  "id": "chatcmpl-...",
  "object": "chat.completion.chunk",
  "choices": [
    {
      "index": 0,
      "delta": { "content": "One" },
      "finish_reason": null
    }
  ]
}

data: {
  "id": "chatcmpl-...",
  "object": "chat.completion.chunk",
  "choices": [
    {
      "index": 0,
      "delta": { "content": ", two" },
      "finish_reason": null
    }
  ]
}

data: [DONE]

Usage in stream

The final stream chunks may include a usage object with token counts (model-dependent).

curl example

curl -N "${SNX_BASE_URL}/chat/completions" \
  -H "Authorization: Bearer ${SNX_API_KEY}" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "deepseek/deepseek-chat",
    "stream": true,
    "messages": [{"role": "user", "content": "Say hi"}]
  }'

Use -N to disable curl buffering.

OpenAI SDK (Python)

stream = client.chat.completions.create(
    model="deepseek/deepseek-chat",
    messages=[{"role": "user", "content": "Say hi"}],
    stream=True,
)
for chunk in stream:
    delta = chunk.choices[0].delta.content or ""
    print(delta, end="", flush=True)

Error handling

Phase	Behavior
Pre-stream	HTTP 4xx/5xx with JSON `error` object (same as non-streaming)
Mid-stream	Client should handle truncated SSE

Quota, balance, and auth errors typically occur before the first byte of the stream.