Join the team redefining what a deeply personal and integrated assistant can be. As part of the Siri organization, you will help shape one of the world’s most widely used AI assistants. It runs on our next generation of Apple Intelligence, with capabilities like personal context understanding and on-screen awareness, and it is built with privacy from the ground up. We build the harness, the foundation that turns a model into an assistant that can act. This is a systems engineering role for people who understand how large language models behave.

Description

A model can't act on its own. The harness runs the agent loop, carries context and tools to the model, executes the tool calls it makes, and streams results back reliably. It spans models running on device and larger models in Private Cloud Compute. It handles everything from single-turn requests to long multi-step tasks that span apps, survive interruptions, and resume cleanly.

We're looking for a strong systems engineer who is fluent in how LLMs behave. The work is real-time and resource-constrained: responses must start fast enough for a voice assistant to feel instant, under tight latency, memory, and power limits on everything from Mac and iPhone to Apple Watch. Failures rarely have a single cause. In a typical week you might track down why a streamed response stalls, make tool calls cancel cleanly when the user interrupts, or replay a failed request to tell whether the model, the context, or the runtime was at fault. Every change to the harness changes how the model behaves, so we measure our work with evals, not just tests.

You'll join the team that owns the core runtime and work alongside senior engineers and researchers. You'll also partner closely with the modeling, tools, and context teams and with app and framework teams across Apple. You'll take features from design through production and grow your ownership of the system over time. You'll use agent harnesses every day while building one for an assistant used by hundreds of millions of people.","responsibilities":" - Build and evolve core parts of the agent runtime: the planning loop, session lifecycle, concurrency, and cancellation

Build the transcript and conversation state, and the platform that defines tools and dynamic instructions and delivers them to the model

Build the executor that dispatches tool calls into Apple's apps and services and handles their results and failures reliably

Integrate on-device and server models, including low-latency streaming and interruption mid-response

Build safety, security, and privacy protections into harness components, working with security and privacy partners

Validate harness changes with evals and latency metrics, and adapt the harness as each new model generation arrives

Build tracing, replay, and testing tools that make a nondeterministic system debuggable

Preferred Qualifications

Experience with Swift and Apple platform development

Experience building agent harnesses, orchestration frameworks, or multi-step tool-use systems

Experience with model inference integration, streaming protocols, or latency-sensitive client-server systems

Experience using evals to diagnose and improve LLM behavior

Experience designing APIs or platforms adopted by other engineering teams

Familiarity with privacy and security engineering in production systems

Active engagement with current research and practice in agent harness design, such as context engineering, tool use, and long-horizon agents, with a record of turning new ideas into practical improvements

Minimum Qualifications

Bachelor's degree in Computer Science or a related field, with 2+ years of industry experience

Strong programming skills in a systems language such as Swift, C++, Rust, Objective-C, or Go

Solid foundation in concurrency, inter-process communication, and performance optimization

Hands-on experience building LLM-powered systems such as agents, tool calling, or prompt and context design, through professional work or substantial personal projects

Daily use of agentic coding tools such as Claude Code, Codex, or Pi, with informed opinions on what makes their harnesses succeed or fail

Ability to communicate clearly and make progress on ambiguous problems

Pay & Benefits

At Apple, base pay is one part of our total compensation package and is determined within a range. This provides the opportunity to progress as you grow and develop within a role. The base pay range for this role is between $150,400 and $225,300, and your base pay will depend on your skills, qualifications, experience, and location.

Apple employees also have the opportunity to become an Apple shareholder through participation in Apple's discretionary employee stock programs. Apple employees are eligible for discretionary restricted stock unit awards, and can purchase Apple stock at a discount if voluntarily participating in Apple's Employee Stock Purchase Plan. You'll also receive benefits including: Comprehensive medical and dental coverage, retirement benefits, a range of discounted products and free services, and for formal education related to advancing your career at Apple, reimbursement for certain educational expenses - including tuition. Additionally, this role might be eligible for discretionary bonuses or commission payments as well as relocation. Learn more about Apple Benefits

Note: Apple benefit, compensation and employee stock programs are subject to eligibility requirements and other terms of the applicable plan or program.

Apple

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