Models

Model	What it's for
celeris-1	General purpose work at the lowest latency
celeris-1-magnus	More intelligent answers, still fast
celeris-1-decision	Yes/no, multiple-choice, and scoring decisions as probabilities

Each model has its own path segment in the base URL, its own properties below, and its own token rates.

celeris-1

celeris-1 is the first model from Celeris: a general purpose diffusion language model that delivers near-GPT-5 level intelligence with up to 15x faster response times.

Unlike autoregressive LLMs, which produce output one token at a time, a diffusion model can refine multiple output tokens in parallel. That parallel refinement suits classification, extraction, scoring, and query rewriting. Typical short requests complete in approximately 50–150 ms within the serving region. Measure your workload with the Server-Timing header.

celeris-1 handles general workloads well. For tasks that need more intelligence, such as extended multi-step reasoning, use celeris-1-magnus for that step and keep celeris-1 everywhere else.

Property	Value
Model name (model field)	celeris-1
Context window	131,072 tokens (prompt + requested maximum output)
Max output (max_tokens)	Any positive integer, bounded only by the context window (prompt + max_tokens ≤ 131,072). Defaults to 2,048 when omitted.
Especially strong at	Classification, extraction, scoring/judging, query rewriting, structured output
Input	Text and images (see Image input)
Output	Text or structured tool calls (see Tool calling)
Response mode	Complete JSON responses or OpenAI-compatible SSE streaming

The context window is a hard ceiling

Prompt tokens plus max_tokens must be at most 131,072, making the effective input limit 131,072 - max_tokens. Oversized requests are rejected up front with a 400 rather than silently truncated. See Rate limits for request limits shared by each workspace and model.

Image understanding

celeris-1 reads images as well as text. Attach one or more images as content parts and ask about them in the same request: screenshot triage, document and receipt extraction, image classification. Images are input only; the model replies with text and does not generate images. See Image input for encoding, sizing, billing, and limits.

celeris-1-magnus

Celeris-1 Magnus is more intelligent than celeris-1 and still fast, though not as fast as celeris-1. Use celeris-1-magnus in both the URL and the request body's model field.

Property	Value
Model name (model field)	celeris-1-magnus
Context window	131,072 tokens (prompt + requested maximum output)
Max output (max_tokens)	16,384 tokens, also bounded by the remaining context window. Defaults to 2,048 when omitted.
Input	Text and images (see Image input)
Output	Text or structured tool calls
Response mode	Complete JSON responses or OpenAI-compatible SSE streaming

Celeris-1 Magnus reasons before it answers unless the request sets chat_template_kwargs: {"enable_thinking": false}. The working can be returned separately from the final content; see Reasoning. Tool definitions use the same tools and tool_choice request fields as celeris-1.

The output limit is part of the context window

Prompt tokens plus max_tokens must be at most 131,072, and max_tokens must not exceed 16,384. Requests outside either limit are rejected with a 400.

celeris-1-decision

celeris-1-decision answers typed questions about your data, text or images, and returns probabilities. It supports two API formats:

• OpenAI Decisions API, POST /v1/decisions, with the OpenAI SDK.
• System One API, POST /v1/systemone, with the Jev SDK.

Both endpoints share the model's price and rate limits. This model does not serve the chat, Responses, or models endpoints.

Property	Value
Model name (model field)	celeris-1-decision
Context window	131,072 tokens. A fixed part is reserved for the answers, so the input limit is slightly lower.
Max output	Set by your questions. There is no max_tokens; see Request limits.
Input	Text and images (see Decisions)
Output	Probabilities for each question, with an optional explanation
Response mode	Complete JSON responses. No streaming.

Model routing and base URLs

The model you're calling is part of the URL path, ahead of the standard OpenAI-style /v1/... suffix:

https://inference.celeris.ai/<model>/v1

For Celeris-1 Magnus:

https://inference.celeris.ai/celeris-1-magnus/v1

Two things must agree:

1. the model segment of the URL path, and
2. the model field in the request body.

A request whose path names an unavailable model returns 404 Not Found. If the path is correct but the model body field does not match, the API returns a validation error.

You can list what a base URL serves with the standard models endpoint:

curl https://inference.celeris.ai/celeris-1/v1/models \
  -H "Authorization: Bearer $CELERIS_API_KEY"

Regions

Celeris aims to serve requests as close as possible to customers. The global base URL above selects the best available nearest region automatically, so most callers do not need to pick one. We recommend it for most customers.

Regional endpoints

A regional endpoint routes requests preferentially to a specific region. Use one when you want to target that region for latency or networking reasons:

Region	Base URL
US East (celeris-1)	https://us-east-1.aws.inference.celeris.ai/celeris-1/v1

During capacity constraints or maintenance, Celeris may temporarily serve a regional endpoint's requests from another region to maintain availability.

Whichever base URL you use, record end-to-end latency and the Server-Timing header; streaming requests also need a client-side time-to-first-token measurement.