Cerebras Chat API

openapi: 3.1.0
info:
  title: Cerebras Inference Chat API
  description: 'OpenAI-compatible REST API for ultra-low-latency inference on open-weight

    large language models hosted on Cerebras wafer-scale silicon. Supports

    chat completions, text completions, and model discovery via Bearer

    token authentication. Generated as a best-effort spec from public

    Cerebras inference documentation; verify against the official API

    reference at https://inference-docs.cerebras.ai before production use.

    '
  version: 1.0.0
  contact:
    name: Cerebras Inference
    url: https://inference-docs.cerebras.ai
  license:
    name: Cerebras Terms of Service
    url: https://www.cerebras.ai/terms
servers:
- url: https://api.cerebras.ai/v1
  description: Cerebras Inference Cloud
security:
- bearerAuth: []
tags:
- name: Chat
  description: OpenAI-compatible chat completions.
paths:
  /chat/completions:
    post:
      tags:
      - Chat
      summary: Create a chat completion
      description: 'Generates a model response for the given chat conversation. Supports

        streaming via server-sent events and tool/function calling. Drop-in

        compatible with the OpenAI client libraries.

        '
      operationId: createChatCompletion
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/ChatCompletionRequest'
      responses:
        '200':
          description: Chat completion response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ChatCompletionResponse'
            text/event-stream:
              schema:
                type: string
                description: Server-sent events stream of chat completion chunks.
        '400':
          $ref: '#/components/responses/ErrorResponse'
        '401':
          $ref: '#/components/responses/ErrorResponse'
        '429':
          $ref: '#/components/responses/ErrorResponse'
components:
  schemas:
    ChatMessage:
      type: object
      required:
      - role
      properties:
        role:
          type: string
          enum:
          - system
          - user
          - assistant
          - developer
          - tool
        content:
          oneOf:
          - type: string
          - type: array
            items:
              type: object
        name:
          type: string
        tool_call_id:
          type: string
        tool_calls:
          type: array
          items:
            type: object
    TimeInfo:
      type: object
      properties:
        queue_time:
          type: number
        prompt_time:
          type: number
        completion_time:
          type: number
        total_time:
          type: number
    ChatCompletionResponse:
      type: object
      properties:
        id:
          type: string
        object:
          type: string
          example: chat.completion
        created:
          type: integer
        model:
          type: string
        system_fingerprint:
          type: string
        choices:
          type: array
          items:
            type: object
            properties:
              index:
                type: integer
              finish_reason:
                type: string
                enum:
                - stop
                - length
                - tool_calls
                - content_filter
              message:
                $ref: '#/components/schemas/ChatMessage'
              logprobs:
                type: object
                nullable: true
        usage:
          $ref: '#/components/schemas/Usage'
        time_info:
          $ref: '#/components/schemas/TimeInfo'
    Error:
      type: object
      properties:
        error:
          type: object
          properties:
            message:
              type: string
            type:
              type: string
            code:
              type: string
            param:
              type: string
    Usage:
      type: object
      properties:
        prompt_tokens:
          type: integer
        completion_tokens:
          type: integer
        total_tokens:
          type: integer
    ChatCompletionRequest:
      type: object
      required:
      - model
      - messages
      properties:
        model:
          type: string
          description: Model identifier (e.g. llama3.1-8b, qwen-3-235b-a22b-instruct-2507, gpt-oss-120b).
        messages:
          type: array
          items:
            $ref: '#/components/schemas/ChatMessage'
        temperature:
          type: number
          minimum: 0
          maximum: 1.5
        top_p:
          type: number
          minimum: 0
          maximum: 1
        max_completion_tokens:
          type: integer
        stream:
          type: boolean
          default: false
        stop:
          oneOf:
          - type: string
          - type: array
            items:
              type: string
        seed:
          type: integer
        frequency_penalty:
          type: number
        presence_penalty:
          type: number
        logprobs:
          type: boolean
        top_logprobs:
          type: integer
        tools:
          type: array
          items:
            type: object
        tool_choice:
          oneOf:
          - type: string
          - type: object
        parallel_tool_calls:
          type: boolean
        response_format:
          type: object
        user:
          type: string
        reasoning_effort:
          type: string
  responses:
    ErrorResponse:
      description: Error response.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: API Key
      description: Provision a CEREBRAS_API_KEY at https://cloud.cerebras.ai