Chat Completions

POST /v1/chat/completions speaks the OpenAI chat completions wire format. Authenticate with Authorization: Bearer sapi_.... For everything not called out below — message formats, tool calling, response shape — see OpenAI Compatibility; this page only covers what’s specific to SingularityAPI.

Request notes

• model — required. A catalog slug (e.g. deepseek-v4-flash) or contract/{slug} for a contract. Must match exactly; see Models & Pricing for the catalog.
• Output limit field — DeepSeek and Kimi models take max_tokens; gpt-5.6 models take max_completion_tokens. Sending the wrong field for the model is a 400. The value must be a positive integer, no larger than the model’s max output. Omit it and the per-model default is injected server-side — check the receipt’s transformed_fields to see when this happened.
• stream — boolean. See Streaming for the SSE details.
• Unsupported or reserved parameters are rejected with a 400, not silently dropped.

Example

$
curl https://api.singularityapi.dev/v1/chat/completions \
>
  -H "Authorization: Bearer $SINGULARITY_API_KEY" \
>
  -H "Content-Type: application/json" \
>
  -d '{
>
    "model": "deepseek-v4-flash",
>
    "messages": [{"role": "user", "content": "Say hello."}]
>
  }'

A response looks like this:

1
{
2
  "id": "chatcmpl-abc123",
3
  "object": "chat.completion",
4
  "created": 1690000000,
5
  "model": "deepseek-v4-flash",
6
  "choices": [
7
    {
8
      "index": 0,
9
      "message": {
10
        "role": "assistant",
11
        "content": "Hello! How can I help you today?"
12
      },
13
      "finish_reason": "stop"
14
    }
15
  ],
16
  "usage": {
17
    "prompt_tokens": 9,
18
    "completion_tokens": 10,
19
    "total_tokens": 19
20
  }
21
}

model in the response is the served model — the catalog model that actually ran the request. On a direct catalog call this matches what you sent; on a contract call it’s the contract’s current target.

Response headers

Every response carries:

• x-singularity-request-id
• x-singularity-receipt-id
• x-singularity-contract-revision — present on contract calls only

Use the receipt ID to pull the exact cost and token usage from GET /v1/receipts/{id}.

Limits

• A request may run up to ~230 seconds. Exceeding it returns 504 request_timeout.
• Request bodies over the size cap are rejected with 413 request_too_large.