Step 5 Preview

Step 5 Preview is StepFun's flagship model for agentic work, aimed at software engineering and professional knowledge work with particular strength in finance.

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input · usd / 1m tok

$1.00

output · usd / 1m tok

$2.70

context window

1.02mtokens

modalities · in → out

pricing

base api ratesusd per 1m tokens

input: $1.00
output: $2.70
cache read: $0.05

providers

StepFun hosts Step 5 Preview. Impossibl routes your request intelligently and handles failover automatically when a provider is down.

StepFun

specifications

takes text and image in, gives text outstepfun/step-5-preview

creatorStepFun
model typeText generation
context window1,024,000 tokens
maximum outputnot published
input
takes text and image in, gives text out
outputtext
tool callingnot verified
releasedsep 20, 2026
endpoint/v1/chat/completions

unknown means the public catalog does not establish that fact. a model's documented capabilities can differ from what a particular api supports. see the model documentation for integration details.

try it · your prompt, this model, live

# responses API
import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["IMPOSSIBL_API_KEY"],
    base_url="https://api.impossibl.com/v1",
)

resp = client.responses.create(
    model="stepfun/step-5-preview",
    input="▌",
)
print(resp.output_text)

edit the prompt, then run

# responses API
import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["IMPOSSIBL_API_KEY"],
    base_url="https://api.impossibl.com/v1",
)

resp = client.responses.create(
    model="stepfun/step-5-preview",
    input="▌",
)
print(resp.output_text)

edit the prompt, then run

benchmarks

benchmark results are not available for this model yet.

compare Step 5 Preview with other models

frontier labs and open weights, best-ranked firstusd / 1m tok · in / out

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impossibl models --all →

frequently asked questions

What is Step 5 Preview?

Step 5 Preview is StepFun's flagship model for agentic work, aimed at software engineering and professional knowledge work with particular strength in finance. It takes text and image input over a context of about one million tokens, reasons at a selectable effort level before answering, and supports tool calling and structured output.

How much does Step 5 Preview cost?

Step 5 Preview costs $1.00 per million input tokens and $2.70 per million output tokens through the Impossibl API. Cache reads cost $0.05 per million tokens. All rates are in USD.

view the pricing table ↑

What is the context length of Step 5 Preview?

Step 5 Preview has a 1,024,000-token context window through the Impossibl API.

What inputs and outputs does Step 5 Preview support?

Step 5 Preview accepts text and image as input. Step 5 Preview returns text.

How do I use Step 5 Preview through an API?

Step 5 Preview is available through the Impossibl API. Use stepfun/step-5-preview as the model identifier with /v1/chat/completions. The quickstart explains how to create an API key and send your first request.

follow the api quickstart →

When was Step 5 Preview released?

StepFun released Step 5 Preview on September 20, 2026.

Creator release announcement ↗

this page describes Step 5 Preview as listed by the impossibl public api. prices and availability come from that catalog, refreshed here every five minutes. this is an impossibl offering, not a comparison of independent hosting-provider quotes. model descriptions and release dates, where available, use the creator sources linked under the answers above.

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