# DeepSeek V4.1 Flash DeepSeek V4.1 Flash is DeepSeek's fast, low-cost model (DeepSeek's own API calls it `deepseek-flash`). It thinks before it answers by default, and you can turn thinking off or set its effort per request. Send the official DeepSeek request to TokLab: change the base URL and the API key, keep the body. ## Model ID | Model ID | Context window | Max output | Reasoning effort | Default | | --------------------- | -------------- | --------------------- | ---------------------------- | ------------------- | | `deepseek-v4.1-flash` | 1M tokens | 384K tokens (393,216) | `none`, `low`, `high`, `max` | Thinking on, `high` | Input: text and images. Output: text. See the [pricing page](https://toklab.ai/pricing) for current prices. ## Quick example ```bash curl https://api.toklab.ai/v1/chat/completions \ -H "Authorization: Bearer $TOKLAB_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "model": "deepseek-v4.1-flash", "messages": [{"role": "user", "content": "Give me three names for a coffee shop."}] }' ``` ```python import os from openai import OpenAI client = OpenAI( api_key=os.environ["TOKLAB_API_KEY"], base_url="https://api.toklab.ai/v1", ) completion = client.chat.completions.create( model="deepseek-v4.1-flash", messages=[{"role": "user", "content": "Give me three names for a coffee shop."}], ) print(completion.choices[0].message.content) ``` ```javascript import OpenAI from "openai"; const client = new OpenAI({ apiKey: process.env.TOKLAB_API_KEY, baseURL: "https://api.toklab.ai/v1", }); const completion = await client.chat.completions.create({ model: "deepseek-v4.1-flash", messages: [{ role: "user", content: "Give me three names for a coffee shop." }], }); console.log(completion.choices[0].message.content); ``` ```go package main import ( "bytes" "fmt" "io" "net/http" "os" ) func main() { body := []byte(`{"model": "deepseek-v4.1-flash", "messages": [{"role": "user", "content": "Give me three names for a coffee shop."}]}`) req, _ := http.NewRequest("POST", "https://api.toklab.ai/v1/chat/completions", bytes.NewReader(body)) req.Header.Set("Authorization", "Bearer "+os.Getenv("TOKLAB_API_KEY")) req.Header.Set("Content-Type", "application/json") resp, err := http.DefaultClient.Do(req) if err != nil { panic(err) } defer resp.Body.Close() out, _ := io.ReadAll(resp.Body) fmt.Println(string(out)) } ``` ## Endpoints | Format | Method and path | Authentication | | ------------------ | ------------------------------------------------ | ----------------------------------------------------------------------------- | | Chat Completions | `POST https://api.toklab.ai/v1/chat/completions` | `Authorization: Bearer ` | | Responses | `POST https://api.toklab.ai/v1/responses` | `Authorization: Bearer ` | | Anthropic Messages | `POST https://api.toklab.ai/v1/messages` | `x-api-key: ` or `Authorization: Bearer `, plus `anthropic-version` | All three return DeepSeek's official response format, streaming or not. Keep the API key in server-side code. ## Parameters Chat Completions fields: | Name | Type | Required | Default | Notes | | --------------------------------------- | ------------------- | -------- | ----------------------------------------------- | ------------------------------------------------------------------------------------------------------- | | `model` | string | Yes | — | `deepseek-v4.1-flash`. | | `messages` | object\[] | Yes | — | Text messages; images as `image_url` parts (see [Image input](#image-input)). | | `thinking.type` | enum | No | `enabled` | `enabled` or `disabled`. | | `reasoning_effort` | enum | No | `high` | `none` (thinking off), `low`, `high` or `max`. `minimal` runs as `low`, `medium` and `xhigh` as `high`. | | `max_tokens` | integer | No | 8K, or 64K with thinking (128K at `max` effort) | 1–393216. Includes the reasoning. | | `stop` | string or string\[] | No | — | Stop sequences. | | `response_format` | object | No | `{"type": "text"}` | `text` or `json_object`. `json_schema` returns 400. | | `tools` | object\[] | No | — | Function tools; `strict` is accepted. | | `tool_choice` | string or object | No | `none` without tools, `auto` with tools | `auto` and `none` are applied. `required` and a named function are accepted but do not force a call. | | `stream` | boolean | No | `false` | Stream server-sent events. | | `stream_options.include_usage` | boolean | No | `false` | Every chunk carries `usage`, `null` except on the last. | | `temperature` | number | No | 1 | 0–2. No effect in thinking mode. | | `top_p` | number | No | 1 | 0–1. In thinking mode values below 0.95 run as 0.95; without thinking it stays 1. | | `user_id` | string | No | — | Your end-user identifier. | | `logprobs`, `top_logprobs` | — | No | — | Accepted (`top_logprobs` 0–20), but no log probabilities are returned. | | `frequency_penalty`, `presence_penalty` | — | No | — | Deprecated by DeepSeek: accepted, no effect. | ## Thinking and effort Thinking is on by default at `high` effort. Turn it off with `"thinking": {"type": "disabled"}` or `"reasoning_effort": "none"`; the answer then comes straight away and costs fewer output tokens. `max` spends the most reasoning on hard problems. The reasoning comes back in `reasoning_content`, next to `content`, and is billed as output tokens. When a request carries `tools`, send every earlier assistant message back with its `reasoning_content`, as DeepSeek requires in tool-call conversations. ## Image input Images go in a user message's `content` as `image_url` parts, either a public `http(s)` URL or a base64 data URI: ```json {"role": "user", "content": [ {"type": "image_url", "image_url": {"url": "https://example.com/chart.png"}}, {"type": "text", "text": "What does this chart show?"} ]} ``` A URL may be at most 8192 characters and point to an image of at most 32 MiB. Replace the example URL with a publicly reachable image of your own. ## Billing dimensions See the [current rates on the pricing page](https://toklab.ai/pricing). A request is billed by the tokens it uses: * input tokens that miss the cache (`prompt_cache_miss_tokens`), * input tokens that hit the cache (`prompt_cache_hit_tokens`), * output tokens, including reasoning. Rates depend on when the request runs. Peak hours are 01:00–04:00 and 06:00–10:00 UTC, Monday to Friday; every other hour, weekends included, is off-peak at half the peak rates. The charge is taken from the `usage` reported with the finished response. A request that fails is not charged. Your account's usage records show the exact charge for every request. ## Output A non-streaming Chat Completions request returns: ```json { "id": "bc86988e-...", "object": "chat.completion", "created": 1790585983, "model": "deepseek-v4.1-flash", "choices": [{ "index": 0, "finish_reason": "stop", "logprobs": null, "message": {"role": "assistant", "reasoning_content": "...", "content": "..."} }], "usage": { "prompt_tokens": 36, "completion_tokens": 39, "total_tokens": 75, "prompt_cache_hit_tokens": 0, "prompt_cache_miss_tokens": 36, "prompt_tokens_details": {"cached_tokens": 0}, "completion_tokens_details": {"reasoning_tokens": 0} } } ``` With `"stream": true` each chunk carries a `delta` with `reasoning_content` or `content`, and the last chunk before `data: [DONE]` carries the usage. ## Responses API and Codex `POST /v1/responses` takes the Responses body: `input`, `instructions`, `max_output_tokens`, `reasoning.effort` (as `reasoning_effort` above), `text.format` (`text` or `json_object`; `json_schema` is accepted but not enforced), `tools` (`function` and the `apply_patch` custom tool), `tool_choice`, `temperature`, `top_p`, `top_logprobs`, `user` and `stream`. The reasoning comes back as a `reasoning` item with `reasoning_text` content, and a stream carries numbered events from `response.created` to `response.completed`, with the reasoning in `response.reasoning_text.delta` events. The API is stateless: `previous_response_id`, `conversation` and built-in tools such as `web_search` are ignored, so send the whole conversation in `input`. To use DeepSeek V4.1 Flash in Codex, add a provider to `~/.codex/config.toml` and set `TOKLAB_API_KEY`: ```toml model = "deepseek-v4.1-flash" model_provider = "toklab" show_raw_agent_reasoning = true [model_providers.toklab] name = "TokLab" base_url = "https://api.toklab.ai/v1" env_key = "TOKLAB_API_KEY" wire_api = "responses" ``` ## Anthropic Messages format Code written for the Anthropic Messages API can call DeepSeek V4.1 Flash too: send the Messages body to `/v1/messages` with `"model": "deepseek-v4.1-flash"`. `system`, `max_tokens`, `tools`, `tool_choice` (`auto`, `none`), `thinking` (`enabled`, `disabled`) and `temperature` (0–2) are applied; `output_config.effort` and `metadata.user_id` are accepted; `top_k`, `stop_sequences` and `tool_choice` `any` have no effect. The reasoning comes back as `thinking` blocks. Images go in as `base64` or `url` sources. ## Errors Errors use `{"error": {"code": ..., "message": "..."}}` (the Messages endpoint uses Anthropic's error shape). The `code` is a code from the [common error catalog](https://toklab.ai/docs/api/errors). Failed requests are not charged. ## Tips * Turn thinking off for simple, fast steps such as classification or extraction; keep it on for reasoning, math and code. * Keep long, reused context at the start of the prompt: cached input is billed at a fraction of the input rate. * Run large batch jobs off-peak, when every rate is half. ## Pricing Every rate this model is billed at, read live from the price list billing uses. A tier applies when its condition matches, checked top to bottom. ### deepseek-v4.1-flash | When | Input (per 1M tokens) | Output (per 1M tokens) | Cache read (per 1M tokens) | | --- | --- | --- | --- | | Day Mon–Fri UTC · Hour 01:00–04:00 UTC or Hour 06:00–10:00 UTC | $0.24 | $0.96 | $0.0048 | | Otherwise | $0.12 | $0.48 | $0.0024 | ## Related * [DeepSeek V4.1 Flash pricing](https://toklab.ai/pricing) * [Download OpenAPI](https://toklab.ai/docs/deepseek-v4-1-flash.openapi.json) * [Copyable Markdown](https://toklab.ai/docs/deepseek-v4-1-flash.md) ## Optional LLM group The groups you can use depend on your account permissions and the model. The [pricing page](https://toklab.ai/pricing) lists each group's prices. API calls keep your API key and model ID. To select a group, send its exact name in the optional `X-SeedRouter-Group` request header, or append it to the model ID as `model:` (see [Model tiers](https://toklab.ai/docs/api/model-tiers)). Replace `GROUP_NAME` below with one of your groups. Omit the header or use `auto` to keep the key's default behavior. ```http X-SeedRouter-Group: GROUP_NAME ``` A restricted API key may have fewer group options than your account. Requests use the selected group's pricing and do not switch to another group if it is unavailable. This option supports HTTP LLM calls, including SSE; it does not apply to WebSocket, image or video calls. To see the groups your key can use, call `GET /v1/models`: it lists `model:` next to the model ID for every model your key can call in more than one group.