OpenAI has disclosed Jalapeño, a custom AI inference accelerator developed with Broadcom and presented at Hot Chips. The company began designing the chip in mid-2024 and taped out its CoWoS package design in November 2025. Engineering samples use the A0 stepping, while a B0 revision in fabrication is projected by OpenAI to improve performance per watt by about 25%. Production is scheduled to ramp gradually during 2027. SemiAnalysis said it observed OpenAI engineers run parts of its InferenceX benchmark in OpenAI’s lab, but said the reported results were supplied by OpenAI and that it did not run the complete benchmark suite or AgentX’s longer-context, multi-turn tests. SemiAnalysis reported that Jalapeño exceeded Nvidia Blackwell and, in output-token throughput per megawatt, Nvidia Vera Rubin’s published multi-token-prediction results while Jalapeño used single-token prediction. The comparison remains limited by differing models, software maturity, and benchmark configurations. Jalapeño uses HBM4 memory with 15.4 TB/s of package bandwidth, a 700 W TDP, and a TSMC N3P compute die. Each rack contains 128 accelerators, and a scale-up network can link 16 racks, or 2,048 chips. OpenAI designed the chip for a unified inference pool rather than separate prefill and decode pools, and uses its Gluon programming language and Codex-assisted kernel development.