Qwen3.5 4B | EmpirioLabs AI Docs

POST /v1/chat/completions

Qwen3.5 4B is a low-cost multimodal reasoning model with 256K context, image and video input, function tools, and structured output.

At a glance

Field	Value
Model id	`qwen3-5-4b`
Input modalities	Text, Image, Video
Output modalities	Text
Context window	256K
Weight precision	FP8 weights + FP8 KV
Max output tokens	32,768
Features	reasoning, vision, video, function_calling, structured_output, cache, multimodal, json_mode, logprobs
Native inference	Yes
New	Yes
Supported endpoints	`POST /v1/chat/completions`, `POST /v1/responses`, `POST /v1/messages`, `POST /v1/completions`

Pricing

Charge	Spec	Rate
Input	per 1M prompt tokens	$0.04
Output	per 1M generated tokens	$0.07
Implicit cache read	per 1M cached input tokens	$0.02

Example request

$ curl https://api.empiriolabs.ai/v1/chat/completions \
>   -H 'Authorization: Bearer $EMPIRIOLABS_API_KEY' \
>   -H 'Content-Type: application/json' \
>   -d '{"model": "qwen3-5-4b", "messages": [{"role":"user","content":"Hello"}]}'

Parameters

Parameter	Type	Required	Default	Description
`temperature`	number	no	`0.7`	Sampling temperature. 0 is deterministic and 2 is maximum randomness. · Range: 0 – 2
`top_p`	number	no	`0.95`	Nucleus sampling probability mass. Lower values make outputs more focused. · Range: 0 – 1
`max_tokens`	integer	no	`4096`	Maximum output tokens. · Range: 1 – 32768
`stop`	string	no	—	Up to 4 strings where the model will stop generating further tokens.
`reasoning_effort`	enum	no	`"medium"`	Reasoning effort. none disables thinking; low, medium, high, and max set bounded thinking budgets. · Allowed: `none`, `low`, `medium`, `high`, `max`
`enable_thinking`	boolean	no	true	Enable the model reasoning channel before final output.
`thinking_budget`	integer	no	`4096`	Maximum thinking tokens before the final answer. If max_tokens is lower, the service reserves room for the answer. · Range: 1024 – 32768
`top_k`	integer	no	`20`	Limit sampling to the top K candidate tokens when supported. · Range: 1 – 200
`min_p`	number	no	`0`	Minimum probability threshold for token sampling. · Range: 0 – 1
`presence_penalty`	number	no	`0`	Penalty for tokens that already appeared in the generated text. · Range: -2 – 2
`frequency_penalty`	number	no	`0`	Penalty based on how often a token has already appeared. · Range: -2 – 2
`repetition_penalty`	number	no	`1`	Penalty used by SGLang to reduce repeated text. · Range: 0.1 – 2
`seed`	integer	no	—	Optional random seed for reproducible sampling. · Range: 0 – 2147483647
`logprobs`	boolean	no	false	Return token log probabilities when supported.
`top_logprobs`	integer	no	—	Return up to this many top token log probabilities. · Range: 0 – 20
`logit_bias`	object	no	—	Bias token IDs by adding positive or negative values before sampling.
`tools`	array	no	—	OpenAI-compatible function tool definitions.
`tool_choice`	object	no	—	OpenAI-compatible function tool selection.
`response_format`	object	no	—	Structured JSON output instructions.
`stream`	boolean	no	false	Stream response deltas using server-sent events.

Notes

Supports text, image, and video input, streaming, function tools, structured JSON output, seed control, and thinking mode on by default. Use reasoning_effort or thinking_budget for bounded thinking, or enable_thinking=false for direct answers. Automatic cache reads are billed at the cached-input rate when reported by the model service. Explicit cache controls are not supported.

Machine-readable schema: GET https://api.empiriolabs.ai/v1/models/qwen3-5-4b.