Principal Engineer, AI Systems

Block•Bay Area, CA, United States of America, CA

9h•$319,000 - $478,600•Remote

About The Position

Block is building toward one of the most ambitious technical visions in our history: an AGI-enabled entity that fundamentally transforms how we deliver economic empowerment. We're assembling a world-class team of AI experts to design and ship autonomous agents and agentic workflows that operate across Square, Cash App, and the broader Block ecosystem. This work is about creating solutions—you'll be building AI that acts, decides, and completes real tasks for real users from across all of Block's business functions. As a Principal Engineer, you'll join as a senior individual contributor with significant technical leadership responsibilities.

Requirements

15+ years of experience in software engineering or machine learning, with recent professional experience building autonomous agents or agentic workflows in production
Deep experience building autonomous agents or agentic workflows in production environments—not just prototypes or demos
Fluency in the core primitives of agentic systems: context management, planning, tool use, memory, evaluation, and multi-step reasoning
Experience bringing frontier LLM capabilities into production products, with hands-on experience in prompt engineering, retrieval-augmented generation, and model optimization
A track record of taking AI-powered products from zero to scale in fast-paced, product-driven environments, with the judgment that comes from operating in production
Strong software engineering fundamentals with the ability to write production-quality code and make sound architectural decisions
Experience providing technical leadership within teams—you've shaped technical direction, driven execution, and elevated others
Product-minded engineering approach—you think in terms of user outcomes, not just model metrics
Excellent collaboration and communication skills, with ability to build alignment across engineering, product, and design
Comfort navigating extreme ambiguity in a domain that's evolving weekly
Alignment with Block's mission of economic empowerment and using technology to create access and opportunity

Nice To Haves

Experience at leading AI organizations with a track record of translating research into production agent systems
Background building or scaling agentic products at startups (including early-stage or pivoting companies)
Experience with model fine-tuning, distillation, or RLHF to improve agent performance
Familiarity with agent evaluation, safety, and alignment challenges in production contexts

Responsibilities

Ship, architect, build, and own end-to-end delivery of autonomous agents and agentic workflows that deliver real business value for Block, ensuring reliability, safety, and performance at scale
Design agent orchestration systems including planning, tool use, memory, evaluation, and multi-agent coordination at production scale
Integrate and optimize frontier LLMs into agent architectures, making decisions on model selection, fine-tuning, prompt engineering, and context retrieval strategies
Drive deeper model optimization work (fine-tuning, distillation, RLHF) where it unlocks agent capability or efficiency
Lead detailed technical planning by breaking down ambitious objectives into concrete, sequenced tasks with clear ownership and execution paths
Provide technical mentorship and guidance to engineers across experience levels, elevating team capabilities through code review, pairing, and knowledge sharing
Partner closely with technical and non-technical stakeholders to translate business objectives into agent-powered product experiences
Keep Block at the frontier by continuously evaluating emerging AI capabilities and making pragmatic tradeoffs across model performance, latency, cost, and user experience
Foster a culture of technical excellence, high-quality delivery, rapid experimentation, and learning within your team and beyond