Principal Software Engineer - Breeze Assistant

HubSpot•Cambridge, MA

14d

About The Position

Breeze Assistant is HubSpot’s AI-powered "System of Action." Our mission is to transform how marketers, sales representatives, and support professionals work by moving beyond simple chat interfaces to an autonomous, proactive assistant that executes GTM (Go-To-Market) workflows. Unlike traditional search-based AI, Breeze Assistant is deeply integrated into the HubSpot CRM. We build the intelligence and infrastructure that allow AI to not just answer questions, but to take actions—like preparing for a complex meeting, researching prospects across the web, and automating multi-step cross-functional tasks—all while maintaining the trust and brand voice of our customers. We are seeking a Principal Software Engineer to be the technical anchor for the Breeze Assistant product line. This role is for a builder who thrives at the intersection of robust distributed systems and bleeding-edge Generative AI. As a Principal Engineer, you are not just following a roadmap; you are helping define it by identifying what is possible with the latest LLM capabilities and turning those possibilities into production-grade features. You will balance the "need for speed" in AI experimentation with the "need for scale" required to support millions of users.

Requirements

User-First Mindset: You have a track record of building products that people love. You advocate for the end-user in design reviews and are willing to pivot technical strategies if it means a better outcome for the customer.
Proven Expertise in Distributed Systems: You have experience building and scaling high-throughput, low-latency systems with strict reliability requirements.
GenAI Proficiency: Deep experience with LLM orchestration, vector databases, and building production-grade RAG pipelines. You understand the trade-offs between different model architectures (GPT-4o, Claude, open-source models).
Agentic Thinking: A background in building autonomous or semi-autonomous systems where AI takes actions, handles tool-calling, and manages complex states.
A Bias for Action: You prefer a working prototype over a 20-page design doc. You have a habit of turning ambiguity into clear plans and working software.
Product Intuition: You care about the "why" behind the "what." You understand the pain points of sales and marketing professionals and build technology that solves them.

Responsibilities

Architectural Leadership for AI Actions: Define the patterns for how AI agents safely and predictably interact with HubSpot’s CRM and third-party ecosystems (Slack, Google Workspace, Microsoft 365).
Rapid GenAI Experimentation: Act as a "zero-to-one" builder. You stay current with the latest trends in LLMs, RAG (Retrieval-Augmented Generation), and Agentic frameworks (like LangGraph or AutoGen) to rapidly prototype and validate new "System of Action" capabilities.
Hands-on, High-Leverage Contributor: You ship production code. You will lead the development of high-impact initiatives, moving from a Jupyter notebook prototype to a petabyte-scale production system with ease.
System Reliability & Trust: Ensure that GenAI outputs are not just "cool," but trustworthy. You will drive the strategy around LLM evaluation, observability, and guardrails to ensure accuracy and data privacy.
Technical Mentorship & Multiplier: You will elevate the AI fluency of the entire engineering org. You’ll mentor senior engineers on prompt engineering, model selection, and the nuances of building non-deterministic systems.
Cross-Functional Influence: Partner with Product and AI Research teams to scope opportunities where GenAI can solve real-world GTM friction, ensuring our technical bets align with HubSpot’s broader AI strategy.
Rapid Domain Fluency: The AI landscape changes weekly. You must be able to dive into a new paper, model, or framework today and explain its strategic value to the team tomorrow.

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