Principal Software Engineer, Breeze

About the Role
We are seeking a Principal Software Engineer to be the technical anchor for the Breeze Assistant platform. This role sits at the intersection of robust distributed systems, bleeding-edge Generative AI, and real customer outcomes.

You are not just following a roadmap — you are helping define it. You will shape how Breeze moves from a highly capable assistant to a trusted, proactive agent: one that delivers durable, shareable artifacts grounded in CRM data; dynamically generates the UI a user needs for the task at hand; orchestrates multi-step workflows across HubSpot and third-party tools; and learns from every interaction to get better. The scale is real — millions of users, petabytes of context, and a platform that every HubSpot engineering team depends on.

Key Expectations
Agentic Platform Architecture: Define the patterns for how AI agents safely interact with HubSpot's CRM, agentic primitives (skills, tools, memory, scheduled prompts), and third-party ecosystems (Slack, Google Workspace, Gong, etc.). You set the bar for how Breeze orchestrates deterministic and non-deterministic steps — choosing the right blend for trust, cost, and outcome quality.
Building Breakthrough Surfaces: Breeze already delivers a significant volume of artifacts across reports, decks, and pages. You will extend the platform so every HubSpot team builds their highest-value deliverables into Breeze — expanding artifact types, opening the platform for internal builders, and driving toward Breeze being the default surface for customers and teams to build on.
Complete Customer Context: Work closely with the Context team to ensure every Breeze interaction is powered by complete, trustworthy growth context: company and industry data, outcome history, learning loops, and customer goals. You will build the technical bridges that let context evolve from a data layer into a dynamic, active collaborator in every user's GTM work.
Rapid GenAI Experimentation: Act as a zero-to-one builder. You stay current with the latest in LLMs, RAG, and agentic frameworks to rapidly prototype and validate new capabilities — and you know when to ship the prototype and when to wait for production-grade infrastructure.
Hands-on, High-Leverage Contributor: You ship production code. You will lead development of high-impact initiatives, moving from a prototype to a production system supporting a broad user base.
System Reliability & Trust: Ensure GenAI outputs are not just capable, but trustworthy. You will drive strategy around LLM evaluation, observability, guardrails, and data privacy — the technical foundation that lets customers trust Breeze enough to run real business processes on it.
Cross-Functional Technical Leadership: Breeze is both a product and a platform. You will partner with Product, AI Research, HubSpot engineering teams, and the Ecosystem teams to ensure every HubSpot team can expose their tools and API endpoints to Breeze — because coverage is the single biggest unlock for use-case completeness.
Technical Mentorship & Multiplier: Elevate AI fluency across the engineering org. Mentor senior engineers on prompt engineering, model selection, agentic design patterns, and the nuances of building non-deterministic systems at scale.

What You Bring
Proven Expertise in Distributed Systems: You have built and scaled high-throughput, low-latency systems with strict reliability requirements — the kind that support high concurrency and vast data scale.
GenAI Proficiency: Deep experience with LLM orchestration, vector databases, RAG pipelines, and multi-agent frameworks. You understand the trade-offs between model architectures, fine-tuning strategies, and inference costs, and you make principled bets.
Agentic System Design: A background in building autonomous or semi-autonomous systems where AI takes actions, handles tool-calling, manages complex state, and recovers gracefully from failure. You've thought hard about the interplay between deterministic and non-deterministic steps in production workflows.
Platform Thinking: You build for other builders. You design primitives — skills, tools, APIs, agentic harnesses — that internal teams and partners can compose into use cases you haven't imagined yet.
User-First Mindset: You have a track record of building products that people love. You advocate for the end-user in design reviews and understand the pain points of sales and marketing professionals well enough to know when a technical tradeoff harms the outcome.
Bias for Action: You prefer a working prototype over a lengthy design doc. You turn ambiguity into clear plans and working software, and you know how to balance the speed of AI experimentation with the rigor of production-grade systems.
Rapid Domain Fluency: The AI landscape changes weekly. You dive into a new paper, model, or framework today and can explain its strategic value — and its limitations — to the team tomorrow.