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Glossary

Terms used in the API, Console, and documentation.

Autoregressive model​

An LLM architecture that generates output one token at a time. Contrast with diffusion LLM.

Base URL​

The per-model API root: https://inference.celeris.ai/<model>/v1. The model is part of the path, ahead of the standard /v1 suffix. See Model routing.

celeris-1​

Celeris' general purpose diffusion language model. See Models.

Chat completion​

The request/response shape of the primary endpoint, POST /chat/completions: a messages array in, a choices array out, in the standard OpenAI wire format.

Context window​

The hard ceiling on prompt tokens plus requested maximum output: 131,072 tokens for celeris-1. Oversized requests are rejected with a 400, never silently truncated. See Models.

Credit​

The prepaid unit of billing. Usage draws down the workspace's credit balance at per-token rates; an exhausted balance returns 402 until topped up.

Diffusion LLM​

A language model that refines multiple output tokens in parallel rather than generating them strictly one at a time. See Models.

Error envelope​

The JSON body returned for Celeris API errors: {"error": {message, type, code}}. Branch handling on the stable code field. See Errors.

Key (API key)​

The ck_-prefixed bearer credential sent as Authorization: Bearer ck_.... Created, revealed, rotated, and revoked in the Console. A key belongs to a workspace and is owned by either a user or the workspace itself. See Authentication.

Organization​

The company context that owns one or more workspaces. See Companies and workspaces for switching, access, roles, and settings.

Playground​

The Console tool for testing prompts against the live model without writing client code. See Console.

Rate limit​

The per-workspace limit on sustained request rate. Exceeding it returns 429 with a Retry-After header. See Rate limits.

Reasoning (thinking)​

The model's optional step of working through a problem before answering, enabled per request with chat_template_kwargs: {"enable_thinking": true}. When separated, the working comes back apart from the answer, on message.reasoning for chat completions and as a type: "reasoning" output item on the Responses API. Its tokens are billed as completion tokens. Off by default. It is not separated on every request, so detect it per response. See Reasoning and Reasoning is not separated on every request.

Region​

The cloud region that serves a request. Celeris aims to serve requests as close as possible to customers. Network distance to the serving region affects end-to-end latency.

Retry-After​

The response header on every 429: the number of seconds to wait before retrying. Honor it as the floor under your backoff.

Server-Timing​

The response header on every successful request that reports service processing time until the response headers are ready. For streaming, that boundary precedes the first token. See Measuring latency.

service_busy​

One of the two 429 codes. The service is temporarily at capacity; retry after Retry-After.

Commercial access​

Organization-level access for higher limits. It is arranged through support, rather than requested from the Console. See Console § Commercial access.

Token​

The unit of model input/output and of billing. Every response's usage block reports prompt_tokens, completion_tokens, and total_tokens.

Trace ID (X-Client-Trace-Id)​

An optional caller-supplied request header that Celeris echoes in API responses. Use it to correlate application logs with support cases. See Support.

Usage​

The Console dashboard of completed request counts and token volumes over 24 hours, 7 days, or 30 days. Rejected requests are not included. See Console § Usage.

Workspace​

Where keys, credits, and usage live, inside an organization. API keys can be created at any time, but a workspace must be activated (by adding a payment method) and hold credit before its keys can serve requests. Credits and usage are shared across the workspace. API keys can be private to their owner or shared with the workspace. See Companies and workspaces.