> ## Documentation Index
> Fetch the complete documentation index at: https://platform.stepfun.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# All Reasoning Models

## Model overview

Our reasoning models are built for deep analytical work — logical reasoning, math, coding, and long-running agent tasks.

## Models

### Step 3.7 Flash

Recommended. Our flagship multimodal reasoning model. Building on the high-throughput reasoning and tool-calling capabilities of `step-3.5-flash`, it adds **native multimodal input** — understanding images and videos directly, without an additional vision MCP or auxiliary model. Powered by a 198B-parameter / 11B-activation sparse MoE architecture and offering three reasoning effort levels (low / medium / high). A fast and dependable model for agent, coding, and multimodal workloads. 256K context.

[View detailed documentation →](/en/guides/models/step-3.7-flash)

### Step 3.5 Flash

Text-only reasoning. Our flagship language reasoning model. It delivers top-tier reasoning quality and fast, reliable execution — decomposing and planning complex tasks, and reliably orchestrating tool calls. Suitable for logical reasoning, math, software engineering, deep research, and other complex workloads. 256K context.

## Context length

Context length is how much input a model can "look back" and consider when generating a response. A longer context lets the model use more history, improving coherence and accuracy. The limit applies to both input and output — total tokens (not characters) cannot exceed the model's context window.

| Model          | Context length |
| -------------- | -------------- |
| Step 3.7 Flash | 256K           |
| Step 3.5 Flash | 256K           |

## Quickstart

<Columns cols={2}>
  <Card title="Reasoning model best practices" href="/en/guides/developer/reasoning">
    See recommended prompting and usage patterns for complex reasoning workloads.
  </Card>

  <Card title="Migrate from OpenAI" href="/en/guides/developer/openai">
    Switch existing OpenAI-compatible integrations to Stepfun with minimal code changes.
  </Card>

  <Card title="Multi-turn conversations" href="/en/guides/developer/multiple-round">
    Store message history and pass context back to the model for continuous dialogue.
  </Card>

  <Card title="JSON Mode" href="/en/guides/developer/json-mode">
    Return machine-parseable JSON so model output can plug into application logic.
  </Card>

  <Card title="Streaming responses" href="/en/guides/developer/stream">
    Stream tokens to the UI as they are generated for a faster perceived response.
  </Card>

  <Card title="Tool Call" href="/en/guides/developer/tool-call">
    Let the model invoke tools and external systems to complete real tasks.
  </Card>

  <Card title="Prompt cache" href="/en/guides/developer/prompt-cache">
    Reuse repeated context to reduce cost and improve latency in repeated requests.
  </Card>
</Columns>