CEcerebras

Create chat completion

Generate conversational responses using a structured message format with roles (system, user, assistant, developer, tool). Best for chatbots, assistants, and multi-turn conversations.

post/v1/chat/completions

Request

  • Base URL
    https://api.cerebras.ai
  • Auth
    HTTP bearer

Headers

Content-Type'application/json' | 'application/vnd.msgpack'

The media type of the request body. Supported values: application/json, application/vnd.msgpack. Default: application/json.

Content-Encoding'gzip'

The compression encoding applied to the request body. When set, the request body must be gzip-compressed. Can be combined with any supported Content-Type. Supported values: gzip.

queue_thresholdstring

Controls the queue time threshold for requests using the flex or auto service tiers. Requests are preemptively rejected if the rolling average queue time exceeds this threshold. Valid range: 50–20000 (milliseconds). Private Preview.

Request body

modelstring required

The ID of the model to use for generating a response.

clear_thinkingboolean nullable

Controls whether thinking content from previous conversation turns is included in the prompt context.

  • false - Thinking from all previous turns is preserved in the conversation history. Recommended for agentic workflows where reasoning from past tool-calling turns may be relevant for future tool calls.
  • true (default) - Thinking from earlier turns is excluded. Recommended for general chat conversations where reasoning from past turns is less relevant for performance.

When this parameter is not specified or set to null, the API defaults to clear_thinking: true.

Only supported on the zai-glm-4.7 model. For additional information, see Preserved thinking in the Z.ai documentation.

frequency_penaltynumber nullable

A number between -2.0 and 2.0. Positive values reduce the likelihood of the model repeating tokens by applying a penalty proportional to how frequently each token has already appeared in the generated output.

logit_biasobject nullable

Modify the likelihood of specified tokens appearing in the completion. Accepts a JSON object that maps tokens (specified by their token ID in the tokenizer) to an associated bias value from -100 to 100. Mathematically, the bias is added to the logits generated by the model prior to sampling. The exact effect will vary per model, but values between -1 and 1 should decrease or increase likelihood of selection; values like -100 or 100 should result in a ban or exclusive selection of the relevant token.

logprobsboolean

Whether to return log probabilities of the output tokens.

max_completion_tokensinteger nullable

The maximum number of tokens that can be generated in the completion, including reasoning tokens. The total length of input tokens and generated tokens is limited by the model's context length.

parallel_tool_callsboolean nullable

Whether to enable parallel function calling during tool use. When enabled (default), the model can request multiple tool calls simultaneously in a single response. When disabled, only one tool call is made at a time.

presence_penaltynumber nullable

A number between -2.0 and 2.0. Positive values reduce the likelihood of the model repeating tokens that have already appeared in the output, encouraging the model to introduce new topics.

prompt_cache_keystring nullable

An opaque identifier that groups related requests so they reuse the same prompt cache. Requests sharing the same 'prompt_cache_key' are routed together, which increases cache hits and reduces time to first token.

Set it to a stable identifier like a conversation ID, user ID, or session ID.

Requires account-level enablement. Contact us or reach out to your account representative to request access.

reasoning_effort'low' | 'medium' | 'high' | 'none' nullable

Controls the amount of reasoning the model performs. Supported values vary by model:

  • gpt-oss-120b: low, medium (default), high
  • zai-glm-4.7: none (disables reasoning)
  • gemma-4-31b: none (default), low, medium, high (all enable reasoning equivalently). raw and hidden reasoning formats are not supported.
seedinteger nullable

If specified, the system will make a best effort to sample deterministically so repeated requests with the same seed and parameters return the same result. Determinism is not guaranteed.

service_tier'priority' | 'default' | 'auto' | 'flex' nullable

Controls request prioritization.

Note: This feature is in Private Preview. For access or more information, contact us or reach out to your account representative.

Available options:

  • priority - Highest priority processing (Only available for dedicated endpoints, not shared endpoints.)
  • default - Standard priority processing
  • auto - Automatically uses the highest available service tier
  • flex - Lowest priority processing

See Service Tiers for more information.

stopstring nullable

Up to 4 sequences where the API will stop generating further tokens. The returned text will not contain the stop sequence.

streamboolean nullable

If set to true, partial message deltas will be sent.

temperaturenumber nullable

Sampling temperature between 0 and 2.0. Higher values (e.g. 0.8) make output more random; lower values (e.g. 0.2) make it more focused and deterministic. We recommend altering this or top_p, not both.

top_logprobsinteger nullable

An integer between 0 and 20 specifying the number of most likely tokens to return at each token position, each with an associated log probability. If using this parameter, logprobs must also be set to true.

top_pnumber nullable

Nucleus sampling parameter. The model considers only the tokens comprising the top top_p probability mass (e.g. 0.1 means only the tokens comprising the top 10% probability mass are considered). We recommend altering this or temperature, not both.

userstring nullable

A unique identifier representing your end-user, which can help monitor and detect abuse.

Response

Successful response

idstring

A unique identifier for the chat completion.

createdinteger

Unix timestamp (in seconds) of when the completion was created.

modelstring

The model used for the chat completion.

object'chat.completion'

The object type. Always chat.completion.

system_fingerprintstring

A fingerprint for the model or backend used to generate the response.

service_tierstring nullable

The service tier used for the request, or null if not specified.

service_tier_used'priority' | 'default' | 'flex' nullable

The service tier used for processing the request. Only present when service_tier is set to auto in the request.

Changes

No recorded changes to this operation across all 1 revision of this API.