StepFun, a Chinese artificial intelligence startup backed by Tencent, launched the STEPX Neo on Oct. 13, a smartphone whose AI agent is built into the operating system itself rather than sitting in a separate app. Pre-orders opened that evening on JD.com, Tmall and Douyin at 3,999 yuan, about $560, with a first sales event on Oct. 16.

The device runs Step AOS 1.0, an operating system StepFun built around a native agent called Amoo. The company's pitch is straightforward: instead of opening a ride-hailing app, typing an address and picking a car, users tell the phone where they want to go, and the agent—software that takes a goal and carries it out on its own—handles the remaining steps. StepFun told the launch audience that in the agent era, AI is no longer an add-on to a smartphone but the product itself.

StepFun first showed the agent, the operating system and the STEPX brand in Shanghai on July 13, without a price or sales date. At the time, the company said conventional smartphone software was never built for autonomous task execution. The months in between turned that argument into a shippable device, complete with a price and retail channels.

Assistants such as Siri and Gemini live inside iOS and Android as features of those systems. StepFun says Step AOS 1.0 was instead built from scratch for the agent, with long-term memory, task scheduling and security controls placed in the base layer. The company describes the system as a mix of Android, Linux and real-time operating system components.

Under the hood, Step AOS breaks phone functions such as messaging, apps, files and settings into small blocks the agent can call directly, using Model Context Protocol, or MCP, a shared standard that lets AI programs plug into other software. Users get two entrances: the familiar app grid and a separate space for the agent.

Amoo keeps one memory for the user's facts, habits and preferences, and another for what it has learned about carrying out tasks. Simple commands like setting an alarm run on a small model inside the phone, some of them offline, while harder requests that span several apps go to a larger model in the cloud. A second MiniLED screen on the back of the device shows what Amoo is doing, giving users a view of the agent's actions.

Nearly 100 companies and products, including Alipay, Tencent, Ctrip, Didi and Meituan, have signed on to Amoo, with payments, travel bookings and content creation still completed on their own platforms. The breadth of that roster matters because the agent's day-to-day reach depends on how many services it can plug into. That is StepFun's alternative to the screen-reading and simulated-click approach used by ByteDance's Doubao phone agent, which drew blocks from major Chinese apps in December. The two designs mark out competing paths for how agents and apps coexist: through agreed integrations, or by operating interfaces the apps did not build for that purpose.

StepFun was founded in 2023 by former Microsoft vice president Jiang Daxin and builds its own large language model, or LLM, the kind of AI system behind ChatGPT. Its flagship, Step 5 Preview, arrived in September with 600 billion parameters—the internal numbers a model adjusts while training—of which 27 billion are active at a time. The model can take in up to 1 million tokens, the chunks of text AI services count and bill by, at once. The smaller Step 3.5 Flash, released earlier this year, is open-source under an Apache 2.0 license.

The 3,999-yuan price includes 12 months of the STEPX Token Plan, which provides 100 billion tokens a month. StepFun has not said what the AI service will cost after the first year, leaving open how much it will cost to keep the agent running once the included supply runs out.