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

Input: text and images. Output: text. See the pricing page for current prices.

Quick example

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."}]
  }'

Endpoints

All three return DeepSeek's official response format, streaming or not. Keep the API key in server-side code.

Parameters

Chat Completions fields:

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:

{"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. 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:

{
  "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:

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. 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.

Related

• DeepSeek V4.1 Flash pricing
• Download OpenAPI
• Copyable Markdown

Optional LLM group

The groups you can use depend on your account permissions and the model. The pricing page 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:<group> (see Model tiers). Replace GROUP_NAME below with one of your groups. Omit the header or use auto to keep the key's default behavior.

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:<group> next to the model ID for every model your key can call in more than one group.