Providers and ModelsStepFun

Step 3.5 Flash

Step 3.5 Flash
StepFun · Text Generation
POST /v1/chat/completions

StepFun text reasoning model for agents, coding, tool calling, and long-context analysis.

At a glance

FieldValue
Model idstep-3-5-flash
Model release date2026-02-12
Input modalitiesText
Output modalitiesText
Context window256K
Weight precision-
Max output tokens131,072
RegionInternational
Featuresreasoning, function_calling, prompt_cache, agentic_coding, web_search
Native inferenceNo
NewYes
Supported endpointsPOST /v1/chat/completions, POST /v1/responses, POST /v1/messages, POST /v1beta/models/step-3-5-flash:generateContent

Pricing

ChargeSpecRate
Inputper 1M prompt tokens$0.10
Outputper 1M generated tokens$0.30
Implicit cache readper 1M cached input tokens$0.02
Web Search (Linkup)per call when invoked$0.013

Example request

$curl https://api.empiriolabs.ai/v1/chat/completions \
>  -H 'Authorization: Bearer $EMPIRIOLABS_API_KEY' \
>  -H 'Content-Type: application/json' \
>  -d '{"model": "step-3-5-flash", "messages": [{"role":"user","content":"Hello"}]}'

Parameters

ParameterTypeRequiredDefaultDescription
temperaturenumberno0.5Sampling temperature. · Range: 0 – 2
top_pnumberno0.9Nucleus sampling probability mass. · Range: 0 – 1
max_tokensintegerno4096Maximum output tokens. Reasoning tokens count toward this limit. · Range: 1 – 131072
stoparrayno-Stop sequences.
frequency_penaltynumberno0Penalty for repeated tokens. · Range: 0 – 1
reasoning_formatenumno"general"Reasoning trace format returned by StepFun. · Allowed: general, deepseek-style
toolsarrayno-OpenAI-compatible function tools.
tool_choicestringno-OpenAI-compatible tool choice.
web_search_linkupbooleannofalseOptional web search powered by Linkup. When enabled, recent web sources are retrieved using your latest user message as the query and provided to the model as additional context. Adds $0.013 per call when invoked on top of the model’s normal token cost. Disabled by default.

Notes

Text-only reasoning with 256K context, function tools, prompt-cache billing, and optional Linkup web search.

Machine-readable schema: GET https://api.empiriolabs.ai/v1/models/step-3-5-flash.