Inception FIM API

openapi: 3.1.0
info:
  title: Inception Chat FIM API
  version: 1.0.0
  description: Inception Labs LLM API — chat, FIM, and edit completions powered by Mercury diffusion language models. OpenAI-compatible request/response shapes with extensions for diffusion-specific features.
  contact:
    name: Inception Labs
    url: https://docs.inceptionlabs.ai
    email: support@inceptionlabs.ai
  license:
    name: Proprietary
  x-logo:
    url: https://docs.inceptionlabs.ai/logo.png
servers:
- url: https://api.inceptionlabs.ai
  description: Production
security:
- BearerAuth: []
tags:
- name: FIM
  description: Fill-in-the-middle code completion endpoints.
paths:
  /v1/fim/completions:
    post:
      summary: Create a fill-in-the-middle completion
      description: Generate a code completion given a `prompt` (prefix) and optional `suffix`. Designed for IDE-style inline completion. Returns a `FimCompletion` object, or a server-sent events stream of `FimCompletionChunk` deltas when `stream=true`. Tool calling and function calling are not supported.
      operationId: createFimCompletion
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/FIMCompletionRequest'
            example:
              model: mercury-edit-2
              prompt: "def fibonacci(n: int) -> int:\n    if n <= 1:\n        return n\n    return "
              suffix: '


                print(fibonacci(10))

                '
              max_tokens: 256
        required: true
      responses:
        '200':
          description: 'Successful response. Returns a JSON object when `stream=false`, or a server-sent events stream of `TextCompletionChunk` objects (terminated by `data: [DONE]`) when `stream=true`.'
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/FIMCompletionResponse'
              example:
                id: cmpl-7a2b3c4d5e
                object: text_completion
                created: 1745798400
                model: mercury-edit-2
                choices:
                - index: 0
                  finish_reason: stop
                  text: fibonacci(n - 1) + fibonacci(n - 2)
                usage:
                  prompt_tokens: 24
                  completion_tokens: 14
                  total_tokens: 38
                  reasoning_tokens: 0
                  cached_input_tokens: 0
            text/event-stream:
              schema:
                $ref: '#/components/schemas/TextCompletionChunk'
              x-stainless-stream-type: sse
              x-stainless-stream-event-schema:
                $ref: '#/components/schemas/TextCompletionChunk'
              x-stainless-stream-terminator: '[DONE]'
        '400':
          description: Bad Request — invalid parameters.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
              example:
                error:
                  message: You exceeded the maximum context length for this model of 128000. Please reduce the length of the messages or completion.
                  type: invalid_request_error
                  param: messages
                  code: context_length_exceeded
        '401':
          description: Unauthorized — missing or invalid API key.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
              example:
                error:
                  message: Incorrect API key provided
                  type: authentication_error
                  param: null
                  code: invalid_api_key
        '402':
          description: Payment Required — billing inactive or quota exceeded.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
              example:
                error:
                  message: Account is inactive
                  type: account_error
                  param: null
                  code: account_error
        '404':
          description: Not Found — model not available for this account.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
              example:
                error:
                  message: model `jupyter-2` not found
                  type: invalid_request_error
                  param: model
                  code: model_not_found
        '429':
          description: Too Many Requests — rate limit exceeded.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
              example:
                error:
                  message: Rate limit exceeded. Please try again later.
                  type: rate_limit_error
                  param: null
                  code: rate_limit_reached
        '500':
          description: Internal Server Error.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
              example:
                error:
                  message: The server had an error while processing your request.
                  type: server_error
                  param: null
                  code: server_error
      security:
      - BearerAuth: []
      tags:
      - FIM
      x-codeSamples:
      - lang: python
        label: Python
        source: "import os\nfrom inceptionai import Inception\n\nclient = Inception(\n    api_key=os.environ.get(\"INCEPTION_API_KEY\"),  # defaults to this env var; can be omitted\n)\n\nfim_completion = client.fim.completions.create(\n    model=\"mercury-edit-2\",\n    prompt=\"def fibonacci(n: int) -> int:\\n    if n <= 1:\\n        return n\\n    return \",\n    suffix=\"\\n\\nprint(fibonacci(10))\\n\",\n    max_tokens=256,\n)\nprint(fim_completion)"
      - lang: typescript
        label: TypeScript
        source: "import Inception from 'inceptionai';\n\nconst client = new Inception({\n  apiKey: process.env['INCEPTION_API_KEY'], // defaults to this env var; can be omitted\n});\n\nconst fimCompletion = await client.fim.completions.create({\n  model: 'mercury-edit-2',\n  prompt: 'def fibonacci(n: int) -> int:\\n    if n <= 1:\\n        return n\\n    return ',\n  suffix: '\\n\\nprint(fibonacci(10))\\n',\n  max_tokens: 256\n});\nconsole.log(fimCompletion);"
components:
  schemas:
    TextChunkChoice:
      description: Represents a choice in a streaming text completion response chunk.
      properties:
        index:
          title: Index
          type: integer
        text:
          anyOf:
          - type: string
          - type: 'null'
          default: null
          description: The text in this chunk.
          title: Text
        finish_reason:
          type:
          - string
          - 'null'
          enum:
          - stop
          - length
          - content_filter
          - null
          description: The reason the model stopped generating tokens.
      required:
      - index
      title: TextChunkChoice
      type: object
    FIMCompletionResponse:
      properties:
        id:
          type: string
          title: Id
        object:
          type: string
          const: text_completion
          title: Object
          default: text_completion
        created:
          type: integer
          title: Created
        model:
          type: string
          title: Model
        choices:
          items:
            $ref: '#/components/schemas/TextCompletionChoice'
          type: array
          title: Choices
        usage:
          $ref: '#/components/schemas/FIMUsage'
        warning:
          anyOf:
          - type: string
          - type: 'null'
          title: Warning
      type: object
      required:
      - id
      - created
      - model
      - choices
      - usage
      - object
      title: FIMCompletionResponse
      example:
        id: cmpl-7a2b3c4d5e
        object: text_completion
        created: 1745798400
        model: mercury-edit-2
        choices:
        - index: 0
          finish_reason: stop
          text: fibonacci(n - 1) + fibonacci(n - 2)
        usage:
          prompt_tokens: 24
          completion_tokens: 14
          total_tokens: 38
          reasoning_tokens: 0
          cached_input_tokens: 0
    TextCompletionChoice:
      properties:
        index:
          type: integer
          title: Index
        text:
          type: string
          title: Text
        finish_reason:
          type:
          - string
          - 'null'
          enum:
          - stop
          - length
          - content_filter
          - null
          description: The reason the model stopped generating tokens.
      type: object
      required:
      - index
      - text
      - finish_reason
      title: TextCompletionChoice
      description: Choice for FIM completions.
    ErrorResponse:
      type: object
      title: ErrorResponse
      required:
      - error
      properties:
        error:
          $ref: '#/components/schemas/ErrorObject'
      example:
        error:
          message: You exceeded the maximum context length for this model of 128000. Please reduce the length of the messages or completion.
          type: invalid_request_error
          param: messages
          code: context_length_exceeded
    FIMCompletionRequest:
      properties:
        prompt:
          type: string
          title: Prompt
          description: The prompt to complete.
        suffix:
          type: string
          title: Suffix
          description: The suffix to complete.
        model:
          type: string
          title: Model
          description: The model to use for the FIM completion.
        max_tokens:
          type: integer
          title: Max Tokens
          description: Maximum number of tokens to generate.
          default: 512
          minimum: 1
          maximum: 8192
        top_p:
          type: number
          title: Top P
          description: Float that controls the cumulative probability of the top tokens to consider.
          default: 1.0
          minimum: 0.0
          maximum: 1.0
        top_k:
          type: integer
          title: Top K
          description: Limits sampling to the `k` most likely tokens. Must be `-1` (disables the cutoff and considers all tokens) or an integer from 1 to 1000; other values such as 0 are rejected.
          default: -1
          minimum: -1
          maximum: 1000
        frequency_penalty:
          type: number
          title: Frequency Penalty
          description: Number between -2 and 2. Positive values penalize tokens based on their existing frequency in the text so far, decreasing the model's likelihood to repeat the same line verbatim.
          default: 0.0
          minimum: -2.0
          maximum: 2.0
        presence_penalty:
          type: number
          title: Presence Penalty
          description: Number between -2 and 2. Positive values penalize tokens based on whether they have appeared in the text so far, increasing the model's likelihood to talk about new topics.
          default: 1.5
          minimum: -2.0
          maximum: 2.0
        repetition_penalty:
          type: number
          title: Repetition Penalty
          description: Penalizes tokens that have already appeared in the generated text. Must be greater than 0. Values greater than 1.0 discourage repetition; 1.0 applies no penalty.
          default: 1.0
          minimum: 0
        stop:
          items:
            type: string
          type: array
          title: Stop
          description: A list of sequences where the API will stop generating further tokens. The returned text will not contain the stop sequences. Defaults to common code-block boundaries.
          default:
          - '


            '
          - "\n \n"
        stream:
          type: boolean
          title: Stream
          description: Whether to stream the response.
          default: false
        stream_options:
          $ref: '#/components/schemas/StreamOptions'
          description: Options that control streaming behavior.
      type: object
      required:
      - prompt
      - model
      title: FIMCompletionRequest
    TextCompletionChunk:
      description: Model for a single chunk in a streaming text completion response.
      properties:
        id:
          title: Id
          type: string
        object:
          const: text_completion
          default: text_completion
          title: Object
          type: string
        created:
          title: Created
          type: integer
        model:
          title: Model
          type: string
        choices:
          items:
            $ref: '#/components/schemas/TextChunkChoice'
          title: Choices
          type: array
      required:
      - id
      - created
      - model
      - choices
      - object
      title: TextCompletionChunk
      type: object
    FIMUsage:
      properties:
        prompt_tokens:
          type: integer
          title: Prompt Tokens
        reasoning_tokens:
          type: integer
          title: Reasoning Tokens
        completion_tokens:
          type: integer
          title: Completion Tokens
        total_tokens:
          type: integer
          title: Total Tokens
        cached_input_tokens:
          type: integer
          title: Cached Input Tokens
      type: object
      required:
      - prompt_tokens
      - reasoning_tokens
      - completion_tokens
      - total_tokens
      - cached_input_tokens
      title: FIMUsage
      description: Usage for FIM completions.
    StreamOptions:
      properties:
        include_usage:
          type: boolean
          title: Include Usage
          description: 'If true, an additional chunk is streamed before the `data: [DONE]` message containing the token usage statistics for the entire request. Inside that chunk, `choices` is an empty array and the `usage` field is populated.'
          default: false
      type: object
      title: StreamOptions
      description: Options for controlling streaming behavior. Only used when `stream=true`.
      required: []
    ErrorObject:
      type: object
      title: ErrorObject
      required:
      - message
      - type
      properties:
        message:
          type: string
          description: Human-readable error message.
        type:
          type: string
          description: Error category, e.g. `invalid_request_error`, `rate_limit_error`.
        param:
          type:
          - string
          - 'null'
          description: Offending parameter, if applicable.
        code:
          type:
          - string
          - 'null'
          description: Machine-readable error code.
  securitySchemes:
    BearerAuth:
      type: http
      scheme: bearer
      description: 'API key provided as a Bearer token: `Authorization: Bearer <api_key>`. Get an API key at https://platform.inceptionlabs.ai.'