Step 5 Preview

stepfun-ai/step-5-preview is StepFun's next-generation flagship base model, built for real-world tasks with a focus on programming and professional expertise. It runs a 1,000,000-token context window with a 64,000-token maximum output, and takes text, image, and video as input while answering in text — so it is a long-context analyst and coding model, not an image or video generator. Reasoning effort is selectable across low, medium, and high (default medium), alongside streaming, tool calling, and structured outputs.

• App code — Vercel AI SDK or OpenAI SDK.
• Coding agent — anyr claude / anyr opencode / anyr codex (playbook).
• No code — playground.

Step 5 Preview is **BYOK-only**, served through AIHubMix. Add an AIHubMix key under Dashboard → BYOK and the request goes out with your key — AnyRouter charges nothing for a BYOK route, and AIHubMix bills you at its published rate of $1.08 per million input tokens, $3.0888 per million output tokens, and $0.054 per million cached input tokens. There is no platform route yet: StepFun's earlier Step 3.7 Flash and Step 3.5 Flash rows already cover the BYOK options if you need those generations instead.

Try it with the Vercel AI SDK. createAnyRouter() reads ANYROUTER_API_KEY:

import { createAnyRouter } from "@anyr/ai-sdk-provider"
import { generateText } from "ai"

const anyrouter = createAnyRouter()

const { text } = await generateText({
  model: anyrouter("stepfun-ai/step-5-preview"),
  prompt: "Review this module and list the three riskiest refactors.",
})
console.log(text)

Or launch a coding agent through the anyr CLI:

curl -fsSL https://anyrouter.dev/setup.sh | bash
anyr login
anyr claude --model "stepfun-ai/step-5-preview"

More: AI SDK · OpenAI SDK · coding agents · BYOK setup.