Step 5 Preview: StepFun's frontier model with 1M context and video input

StepFun released Step 5 Preview, a flagship model for agentic work that natively supports text, image, and video input and offers a 1M-token context window. StepFun says the model delivers frontier-level performance across software engineering and professional knowledge work, with particular strength in finance, and supports multi-step agent tasks, long-document processing, and multimodal understanding. Step 5 Preview is billed on actual input and output token usage and can be integrated via the StepFun Open Platform Chat Completions API or Claude Code with Step Plan.

Step 5 Preview is StepFun’s flagship model for agentic work. It delivers frontier-level performance across software engineering and professional knowledge work, with particular strength in finance. It natively supports text, image, and video input and provides a 1M-token context window , making it suitable for tasks that require large amounts of information, tool calls, and continuous progress toward a deliverable. At a glance Core capabilities Long-context understanding and reasoning Analyze long documents, multiple source materials, and conversation history within a 1M-token context. Typical tasks : cross-document question answering and research material organization. Programming and software engineering Work across multiple programming languages and engineering tasks, with tools to advance development, modification, and verification. Typical tasks : troubleshooting, code changes, and test creation. Multi-step Agent tasks Use tools provided by an application to retrieve information, process documents, and continue through multi-step work. Typical tasks : deep research and analytical reporting. Multimodal understanding Combine images, video, and text to extract and analyze multimodal information. Typical tasks : chart analysis, screenshot question answering, and video summarization. Use cases - Software development : Combine code, dependency information, and error logs to locate problems, modify code, and recommend tests. - Long-document processing : Organize multiple sources in a long context, extract and summarize information, and cross-check details. - Research and analysis : Work with search, code execution, or document tools to break down tasks and produce structured results. - Multimodal understanding : Analyze screenshots, charts, and video, and output conclusions in a specified format. Input and output Image and video input See the Quickstart https://platform.stepfun.ai/docs/en/quickstart/overview for image and video request examples. For complete limits, see Image understanding best practices https://platform.stepfun.ai/docs/en/guides/developer/image-chat and Video understanding best practices https://platform.stepfun.ai/docs/en/guides/developer/video-chat . Features and configuration Integration 1. Create an API key on the StepFun Open Platform. 2. Open the Quickstart https://platform.stepfun.ai/docs/en/quickstart/overview , select Step 5 Preview, and switch between the text chat, image understanding, and video understanding examples. 3. Send a request with cURL or Python and read the result from choices 0 .message.content . 4. Before going live, use the API reference https://platform.stepfun.ai/docs/en/api-reference/chat/chat-completion-create to add timeout, retry, error-handling, and key-management logic. Quickstart See text, image, and video request examples. Chat Completions API See the complete request parameters, response fields, and usage information. Claude Code integration Configure Step Plan and enable 1M context. Pricing and rate limits Step 5 Preview is billed based on actual input and output token usage. For current prices, cache billing rules, and account rate limits, see Pricing and Rate Limits https://platform.stepfun.ai/docs/en/guides/pricing/details pricing-for-multimodal-reasoning-models . More information Quickstart https://platform.stepfun.ai/docs/en/quickstart/overview · API reference https://platform.stepfun.ai/docs/en/api-reference/chat/chat-completion-create · Claude Code integration https://platform.stepfun.ai/docs/en/step-plan/integrations/claude-code · Pricing and Rate Limits https://platform.stepfun.ai/docs/en/guides/pricing/details