On July 13, Stepfun unveiled three new things at once in Shanghai: the Agent-native system Step AOS, the terminal brand STEPX, and the STEPX Neo, dubbed "the world's first large-model-native Agent phone". Different from the "Android + a layer of AI kit" approach, Step AOS rewrites from Android, Linux, and RTOS all the way down to the kernel, treating the LLM as a first-class OS citizen. The most interesting technical piece is how capabilities are organized. Step AOS breaks communication, apps, files, and settings into smaller "directly callable by Agents" units according to the MCP (Model Context Protocol) standard — equivalent to elevating MCP from a tool-call protocol to an OS system-call protocol. The embedded Agent Amoo uses a "dual-domain three-step memory": the user domain remembers habits, the Agent domain accumulates experience, with the official claim that recall can be compressed to 15 ms and LongMemEval ranks first; the underlying on-device model is Step Edge, claimed to be first across 29 benchmarks — but the comparator wasn't disclosed. The execution chain goes "end-cloud multi-brain" — dynamically selecting on-device or cloud models based on complexity, cost, and latency; the first batch of ecosystem partners includes WPS, Meituan, CapCut, Ctrip, Amap, Alipay, Baidu, JD, Meitu Xiuxiu, and Weibo. On the security side, Stepfun proposes a "trusted execution environment + per-step auditability + on-demand authorization + one-click revocation" four-dimension framework, and jointly releases an Agent-security white paper with Shanghai AI Lab. STEPX Neo has also passed the currently highest-open-level national "AI Terminal Intelligence Grading" L3 certification — the first phone to receive this certificate. Commentary: the real signal of this path is that LLM companies are bypassing the App layer and incorporating the terminal experience as first-class OS citizens — the opposite of the "standalone AI hardware" route of Humane AI Pin and Rabbit r1, and a Chinese response to the rumored OpenAI "AI phone". Skepticism worth keeping: the on-device 29 firsts don't have a public comparator list, the ecosystem connections are still mostly calling existing App APIs, and the L3 certification's evaluation details haven't been made public — beyond the demo, the experience actually delivered to users still has some distance to go.