Chat completions

POST https://api.llmbase.ai/v1/chat/completions

The chat completions endpoint is compatible with the OpenAI Chat API. Any client that works with OpenAI will work here — change only the base URL and key.

Request body

Required fields

Field	Type	Description
model	string	Model ID, e.g. "zai-org/glm-5". See Models.
messages	array	Conversation history. At least one message required.

Messages

Each message is an object with a role and content:

[
  { "role": "system",    "content": "You are a helpful assistant." },
  { "role": "user",      "content": "Summarise this article: ..." },
  { "role": "assistant", "content": "Here is a summary: ..." },
  { "role": "user",      "content": "Make it shorter." }
]

Roles:

Role	Description
system	Sets the behaviour and persona of the assistant
user	A message from the end user
assistant	A previous response from the model (for multi-turn conversations)

User messages support multimodal content (text + images) as an array of parts:

{
  "role": "user",
  "content": [
    { "type": "text", "text": "What is in this image?" },
    { "type": "image_url", "image_url": { "url": "https://example.com/image.jpg" } }
  ]
}

Optional parameters

Parameter	Type	Default	Description
stream	boolean	false	Stream tokens as SSE. See Streaming.
temperature	number	model default	Sampling temperature 0–2. Lower = more deterministic.
top_p	number	model default	Nucleus sampling probability mass 0–1.
max_tokens	integer	model max	Maximum tokens to generate.
frequency_penalty	number	0	Penalises repeated tokens by frequency -2.0–2.0.
presence_penalty	number	0	Penalises tokens that have appeared at all -2.0–2.0.
stop	string | string[]	—	Up to 4 sequences where generation stops.
seed	integer	—	Fixed seed for deterministic outputs (best-effort).

Non-streaming response

{
  "id": "chatcmpl-a1b2c3d4e5f6a1b2c3d4e5f6",
  "object": "chat.completion",
  "created": 1741000000,
  "model": "zai-org/glm-5",
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": "Hello! I can help you with a wide range of tasks..."
      },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 12,
    "completion_tokens": 48,
    "total_tokens": 60
  }
}

finish_reason values

Value	Meaning
stop	Model finished naturally
length	max_tokens limit reached
content_filter	Response was filtered
tool_calls	Model called a tool (not yet supported)

Streaming

Set "stream": true to receive a stream of Server-Sent Events. Each event is a JSON-encoded chat.completion.chunk.

curl https://api.llmbase.ai/v1/chat/completions \
  -H "Authorization: Bearer $LLMBASE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "zai-org/glm-5",
    "messages": [{ "role": "user", "content": "Count to 5." }],
    "stream": true
  }'

The stream is a sequence of data: {...} lines, terminated by data: [DONE]:

data: {"id":"chatcmpl-...","object":"chat.completion.chunk","created":1741000000,"model":"zai-org/glm-5","choices":[{"index":0,"delta":{"role":"assistant"},"finish_reason":null}]}

data: {"id":"chatcmpl-...","object":"chat.completion.chunk","created":1741000000,"model":"zai-org/glm-5","choices":[{"index":0,"delta":{"content":"1"},"finish_reason":null}]}

data: {"id":"chatcmpl-...","object":"chat.completion.chunk","created":1741000000,"model":"zai-org/glm-5","choices":[{"index":0,"delta":{},"finish_reason":"stop"}],"usage":{"prompt_tokens":10,"completion_tokens":9,"total_tokens":19}}

data: [DONE]

Token usage is included in the final chunk of every stream.

Streaming with the OpenAI SDK

const stream = await client.chat.completions.create({
  model: "zai-org/glm-5",
  messages: [{ role: "user", content: "Write a short poem." }],
  stream: true,
});

for await (const chunk of stream) {
  process.stdout.write(chunk.choices[0]?.delta?.content ?? "");
}

Full example

import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "https://api.llmbase.ai/v1",
  apiKey: process.env.LLMBASE_API_KEY,
});

const response = await client.chat.completions.create({
  model: "zai-org/glm-5",
  messages: [
    { role: "system", content: "You are a concise assistant." },
    { role: "user",   content: "Explain recursion in one sentence." },
  ],
  temperature: 0.7,
  max_tokens: 100,
});

console.log(response.choices[0].message.content);
// → "Recursion is when a function calls itself until a base condition is met."

Error responses

Errors are returned as JSON with an error object:

{
  "error": {
    "message": "Model not found: unknown/model",
    "type": "invalid_request_error"
  }
}

HTTP status	Meaning
400	Bad request — missing or invalid fields
401	Authentication failed — check your API key
404	Model not found
502	All upstream providers failed — retry with backoff