Principal Software Engineer - UI

• What you get to do in this role:
• Platform Architecture & Strategy — Define and own the long-term architecture of a server-rendered web component platform that powers AI-native user experiences across the product. You'll make the key decisions on rendering, component runtime, design systems, and streaming UX for AI-generated content, and keep the experience layer resilient and coherent as the platform scales.
• Rendering & Performance — Own end-to-end experience performance: server-side rendering, streaming HTML, hydration correctness, and time-to-interactive. Push the state of the art in server rendering of web components so experiences are fast, deterministic, and consistent between server and client.
• AI-Native Intelligent Experiences — Build the platform primitives product teams use to expose agentic backends to end users, including recommendations, autonomous triage, generated insights, and multi-step agent reasoning. Own the hard UX problems specific to AI-native products: streaming model output, progressive disclosure of agent reasoning, graceful handling of latency and uncertainty, and human-in-the-loop review flows that make autonomous behavior legible and controllable.
• Secure, Scalable Runtime — Design how the platform runs in production on Kubernetes: sandboxed execution of application code, multi-tenant isolation, secure credential and token propagation, memory and resource budgeting, version-tiered rollouts, and observability for a large Node.js fleet under real traffic.
• Developer Platform & Ecosystem — Shape the component model, data-loading and context APIs, design system, tooling, and guardrails that let many teams build applications on the platform. Make the right path the easy path.
• Agentic Pipeline Awareness — Work closely with ML and platform teams building agent orchestration and tool-calling infrastructure (multi-agent dispatch, MCP-style tool integration, reasoning traceability). Translate what those backends can do into UX patterns that are usable, safe, and trustworthy.
• Business Alignment — Tie platform and experience architecture to business goals, so that engineering velocity, experience quality, and adoption of AI-native features support customer acquisition, retention, and time-to-market.
• Hands-on Engineering — Write high-performance, production-grade code across the experience stack (TypeScript, Lit.js / Web Components, Node.js, modern build tooling) and the runtime stack (Kubernetes, containerized services). Debug the hardest problems yourself, from hydration mismatches to memory leaks to intermittent production failures.
• Cross-functional Execution — Drive business-critical platform outcomes together with ML, backend platform, SRE, security, UX, and product teams.
• Engineering Culture — Mentor senior and staff engineers, lead architecture reviews, raise the bar on testing and reliability, and build a culture of rapid, impact-driven innovation.
• Ownership & Initiative — Spot platform and experience gaps before they become problems, propose solutions, align stakeholders, and own execution.
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To be successful in this role you have:

• 15+ years of software engineering experience, focused in frontend or web platform engineering at a high-growth tech company or top-tier AI lab.
• Deep expertise in web platform internals: Web Components and Shadow DOM, server-side rendering and hydration, streaming, module loading, and browser performance. Production experience with Lit.js, React, or comparable frameworks, and a clear view of the tradeoffs between them.
• Strong server-side JavaScript/TypeScript engineering skills: Node.js, HTTP/2, proxies and streaming, V8 memory behavior, and isolate or worker-based execution models.
• Hands-on experience running latency-sensitive services on Kubernetes, including resource management, rollout strategies, Helm, and production observability.
• Strong web security fundamentals: session and token handling, egress control, sandboxing of untrusted code, and trust boundaries in multi-tenant systems.
• Has shipped intelligent, AI-driven user experiences (not just consumed an LLM API), with strong intuition for how agent and model output should surface to real users.
• Hands-on experience with agentic or multi-agent systems from the consumer side.
• Understands agent orchestration, tool-calling protocols (MCP or equivalent), and reasoning traceability well enough to design UX and platform primitives around them.
• Experience designing frameworks, SDKs, or design systems adopted by many teams, including versioning, backward compatibility, and migration strategy.
• A track record of connecting platform and UX decisions to business outcomes such as adoption, retention, and time-to-market, not just technical metrics.
• Self-driven with strong ownership: able to identify gaps, propose solutions, align stakeholders, and execute at startup pace.

Good to Have

• Prior experience in distributed systems performance and scalability, or in large-scale Node.js fleet operations.
• Open-source contributions to major web frameworks, SSR tooling, build systems, design systems, or agent-framework projects.
• Experience with enterprise SaaS platforms and their extensibility and customization models.
• Prior startup experience working closely with Product and Growth teams in an early-stage environment.