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FIM Completion API (Beta)

POST 
/completions

FIM (Fill In the Middle) Completion API.
User must set base_url="https://api.deepseek.com/beta" to use this feature.

Request​

Body

required

    model stringrequired

    Possible values: [deepseek-flash, deepseek-v4-pro]

    ID of the model to use. Use deepseek-flash or deepseek-v4-pro.

    prompt stringrequired

    The prompt to generate completions for.

    echo booleannullable

    Echo back the prompt in addition to the completion. Cannot be used together with suffix or logprobs.

    logprobs integernullable

    Possible values: <= 20

    Include the log probabilities on the logprobs most likely output tokens, as well the chosen tokens. For example, if logprobs is 20, the API will return a list of the 20 most likely tokens. The API will always return the logprob of the sampled token, so there may be up to logprobs+1 elements in the response.

    The maximum value for logprobs is 20.

    max_tokens integernullable

    The maximum number of tokens that can be generated in the completion.

    stop

    object

    nullable

    Up to 16 sequences where the API will stop generating further tokens. The returned text will not contain the stop sequence.

    oneOf

    string

    stream booleannullable

    Whether to stream back partial progress. If set, tokens will be sent as data-only server-sent events as they become available, with the stream terminated by a data: [DONE] message. Example Python code.

    stream_options

    object

    nullable

    Options for streaming response. Must be set together with stream: true; if stream is not set to true, the API returns a 400 error.

    include_usage boolean

    If set to true, all chunks in the stream will include a usage field, whose value is null on every chunk except the last one. If omitted or set to false, the usage field is absent from all chunks except the last one.

    Either way, the last chunk before the data: [DONE] message carries the token usage statistics for the entire request in its usage field. Note that no separate usage-only chunk is emitted: the statistics ride on the last content chunk, whose choices array always contains exactly one element that carries no new content and a non-null finish_reason.

    suffix stringnullable

    The suffix that comes after a completion of inserted text.

    temperature numbernullable

    Possible values: <= 2

    Default value: 1

    What sampling temperature to use, between 0 and 2. Higher values like 0.8 will make the output more random, while lower values like 0.2 will make it more focused and deterministic.

    We generally recommend altering this or top_p but not both.

    top_p numbernullable

    Possible values: <= 1

    Default value: 1

    An alternative to sampling with temperature, called nucleus sampling, where the model considers the results of the tokens with top_p probability mass. So 0.1 means only the tokens comprising the top 10% probability mass are considered.

    The value must be greater than 0 and at most 1. We generally recommend altering this or temperature but not both.

    frequency_penalty deprecated

    This parameter is no longer supported. It will not take effect if you pass it to the API.

    presence_penalty deprecated

    This parameter is no longer supported. It will not take effect if you pass it to the API.

Responses​

OK

Schema

    id stringrequired

    A unique identifier for the completion.

    choices

    object[]

    required

    The list of completion choices the model generated for the input prompt.

  • Array [

    • finish_reason stringrequired

    Possible values: [stop, length, content_filter, insufficient_system_resource, aborted]

    The reason the model stopped generating tokens. This will be stop if the model hit a natural stop point or a provided stop sequence, length if the maximum number of tokens specified in the request was reached, content_filter if content was omitted due to a flag from our content filters, insufficient_system_resource if the request is interrupted due to insufficient resource of the inference system, or aborted if the generation was interrupted.

    index integerrequired

    logprobs

    object

    nullable

    required

    text_offset integer[]
    token_logprobs number[]
    tokens string[]
    top_logprobs object[]
    text stringrequired

  • ]

    • created integerrequired

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

    model stringrequired

    The model used for completion.

    system_fingerprint string

    This fingerprint represents the backend configuration that the model runs with.

    object stringrequired

    Possible values: [text_completion]

    The object type, which is always "text_completion"

    usage

    object

    Usage statistics for the completion request.

    completion_tokens integerrequired

    Number of tokens in the generated completion.

    prompt_tokens integerrequired

    Number of tokens in the prompt. It equals prompt_cache_hit_tokens + prompt_cache_miss_tokens.

    prompt_tokens_details

    object

    required

    Breakdown of tokens used in the prompt.

    cached_tokens integer

    Number of tokens in the prompt that hit the context cache. Same as prompt_cache_hit_tokens.

    prompt_cache_hit_tokens integerrequired

    Number of tokens in the prompt that hits the context cache.

    prompt_cache_miss_tokens integerrequired

    Number of tokens in the prompt that misses the context cache.

    total_tokens integerrequired

    Total number of tokens used in the request (prompt + completion).

    completion_tokens_details

    object

    Breakdown of tokens used in a completion.

    reasoning_tokens integer

    Tokens generated by the model for reasoning.

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