Sr. Machine Learning Engineer – LLMs, Agent Systems, and Simulation Tooling, Siri Core Modeling

Sr. Machine Learning Engineer – LLMs, Agent Systems, and Simulation Tooling, Siri Core Modeling

Sunnyvale, California, United States Machine Learning and AI

Join a pioneering team shaping the future of voice-first, agentic platforms. As a Senior Machine Learning Engineer, you’ll help define how next-generation intelligent agents reason, plan, and interact with people through natural voice and multimodal experiences. You will develop the foundations of scalable LLM reasoning systems that will power the next wave of human–AI interaction.

We’re seeking a senior ML engineer with strong expertise in large language models and agent-based systems to build the core reasoning and simulation capabilities behind a future platform for agentic voice experiences. You will work on advancing how LLMs plan, adapt, and evaluate actions in realistic environments, contributing to the development of reliable and trustworthy AI agents. Your work will focus on developing robust infrastructure and tooling for training, simulation, and evaluation of agentic LLMs.

You’ll design and run experiments in simulated environments, build scalable evaluation pipelines, and help integrate agent behaviors across client and backend systems. This role is an opportunity to push the boundaries of reasoning, adaptive behavior, and platform architecture for agent-based intelligence. You will collaborate closely with ML scientists, applied researchers, and product engineers to transform early research into deployable systems.

Together, we will shape a platform that empowers developers and end-users to build rich, voice-driven AI experiences.

• Design and implement scalable simulation and evaluation frameworks for LLM-based agents
• Collaborate with ML researchers to translate novel reasoning approaches into production-grade systems
• Develop infrastructure for training and experimentation with agentic behaviors
• Integrate agent reasoning capabilities into client-side and backend environments