AI Engineer

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Location: San Francisco, CA
Company size: 10–50
Posted: 1mo ago
Via: Yc

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Job listing · Updated 21 AUG 2026

AI Engineer

Sphere· San Francisco HQView company profile

Job title: AI Engineer
Job location: San Francisco HQ
Job listing URL: https://www.ycombinator.com/companies/sphere/jobs/5CBpoL3-ai-engineer
Job description: Sphere has built the world’s first AI-native tax engine that helps companies like Lovable, Eleven Labs, Replit, Runway AI, Windsurf (+ many more) automate their sales tax, VAT and GST obligations: - We're growing rapidly (34%+ MoM revenue growth) and helping the fastest growing tech companies around the world including Lovable, Eleven Labs, Replit, Windsurf, Fathom, Linktree, Photoroom, Sierra AI, Zed etc - We’ve spent the last 1.5 years building local rails into tax authorities in both the US and internationally to properly automate compliance processes (no other vendor has done this) - We're building the world's first AI-native tax engine (which will be the foundation for a broader cross border compliance platform; think Deel for international billing) - We're well funded by Andreessen Horowitz, YC and Felicis Ventures Sphere is looking for an AI engineer to help build out its proprietary Tax Review and Assessment Model (TRAM) across jurisdictions and other compliance areas. You will be pushing the frontiers of what's possible with AI in the finance space and building the core piece of technology that shape the future of Sphere. **Why this is a massive opportunity:** 🌍 Massive TAM: Every business around the world needs this. Compliance isn’t optional. 🌬️ Strong macro tailwinds: Businesses are expanding globally at a faster pace, while tax authorities are cracking down on cross-border compliance, driving urgent demand. ✨ AI advantage: Incumbents can’t scale beyond the U.S.; our AI-native tax engine can. 🔮 Product vision: Indirect tax is just the start; we’re building the Deel for international billing. **What you will do:** _Within weeks:_ - Lead development of new features aimed at increasing TRAM’s test-time accuracy - Work on the underlying data and retrieval pipelines that help power our AI workflows - Work directly with our internal tax experts to understand how TRAM can better reason like them _Within months:_ - Own TRAM’s eval framework and workflows - Work directly with leading frontier labs to reinforce fine tune models on our proprietary data **Requirements:** - Prior experience building AI enabled products, particularly RAG systems - Experience fine tuning base models, ideally via RFT - Willingness to dive into tax technical problems - if you aren’t willing to dive deep on how the model should reason through the tax research process you won’t be effective - A strong understanding of how LLMs and reasoning models function _Nice to have:_ - Experience working with LLMs on legal applications - Experience with RAG data pipelines and collecting/curating data for the pipeline ## **What’s important to us:** - The Dog: Grit \> pedigree. - Ship fast: If it can be done today, do it today. - Self-starter: No hand-holding - Accountability: You’ll be held accountable to objective, measurable targets each month. - In-person: SF only.

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