Senior Software Engineer, AI at Lassie | San Francisco

At Lassie, we are revolutionizing healthcare by building AI solutions that empower health practices. Our innovative approach addresses the chronic staffing shortages that have plagued medical offices, particularly since the pandemic, leading to frustrating patient experiences.We envision a future where AI serves as the backbone of medical practices—efficiently managing administrative tasks and enhancing patient interactions through intelligent agents.Founded by seasoned entrepreneurs Steijn Pelle and Frédéric Renken, who have successfully driven growth at major tech companies, we are infusing consumer product design into healthcare, reshaping how doctors and patients connect.

At Lassie, we are revolutionizing the healthcare landscape by developing AI solutions for independent doctors. Our mission is to transform a $1 trillion industry that still relies heavily on paper into a streamlined, automated powerhouse. With rapid growth and a strong technological edge, our early customer feedback has been overwhelmingly positive, positioning us to achieve unicorn status in the near future.Founded by Steijn Pelle, who played a pivotal role in elevating Robinhood and Coinbase to their first hundreds of millions in annual revenue, and Frédéric Renken, an engineer turned product innovator at Superhuman, we are in the process of forming a dynamic go-to-market team.We are seeking a proactive individual ready to embrace substantial responsibilities quickly and evolve into a key player within our operations. In this role, you will collaborate closely with Steijn and the initial GTM team to drive our journey towards a $100 million ARR over the next year.

Lassie is revolutionizing the healthcare industry by leveraging artificial intelligence to transition health practices from outdated paper systems to efficient, automated solutions. Positioned as a technology frontrunner, we are rapidly expanding, with a trajectory towards unicorn status by next year, serving a growing base of satisfied customers.Founded by industry veterans Steijn Pelle and Frédéric Renken, who have previously propelled companies like Robinhood and Coinbase to substantial revenue milestones, Lassie is currently in the process of building its Series A team. Our early employees have experienced excellence and are committed to recreating that success.About the RoleWe are seeking a proactive and strategic Founding Recruiter to spearhead the establishment of our entire talent acquisition function. In this pivotal role, you will collaborate closely with the founders, overseeing hiring initiatives across software engineering, product development, and go-to-market strategies as we undergo rapid scaling.You will be responsible for crafting and implementing our recruiting strategy, sourcing top-tier talent, and developing processes that attract the best candidates. As one of our foundational hires, your contributions will significantly influence the culture, workforce, and future direction of Lassie.This opportunity is perfect for individuals enthusiastic about working in a dynamic, early-stage environment and who are passionate about building teams from the ground up.

At Lassie, we are revolutionizing healthcare by creating the AI that powers every health practice.Over a million health practices are spending upwards of $100 billion annually on administrative staff, yet they struggle to recruit enough personnel. The ongoing impacts of COVID-19 have left many offices understaffed, resulting in patients experiencing unanswered calls and confusing bills daily.We envision a future where AI manages the operations of a doctor's office, streamlining administration and facilitating patient interactions.Founded by Steijn Pelle, who played a pivotal role in scaling Robinhood and Coinbase to hundreds of millions in revenue, and Frédéric Renken, a former engineer and the first product hire at Superhuman, we are infusing consumer product excellence into healthcare and transforming the interaction dynamic between doctors and their patients.About the RoleWe are seeking a Software Engineer to take charge of the systems that enhance the entire customer experience: from discovering our services to onboarding and going live.Independent health practices are often overburdened and require better tools. Your role will be crucial in helping them discover Lassie and achieve success swiftly. Collaborating closely with sales and product teams, you will develop infrastructure that ensures smooth deal closures and enables new customers to thrive from day one.This position is perfect for someone who enjoys experimentation, thrives in a fast-paced environment, and desires to see a direct correlation between their efforts and revenue impact.You Will Be a Great Fit If You...Are enthusiastic about experimentation, learning from mistakes, and employing first principles thinking.Develop tools and systems that amplify the effectiveness of sales and engineering teams.Work closely with sales to transform chaotic workflows into streamlined processes.Help shape our marketing strategies, branding, and distribution methods.Engage with technologies such as Python, TypeScript, various databases, serverless environments, and Salesforce, even if some are new to you.Some Things We've BuiltA specialized growth and onboarding infrastructure that has reduced the demo-to-close timeframe from weeks to mere hours.Data pipelines capable of processing over $1 billion in insurance claims.A synchronization engine supported by encrypted SQLite.

Responsibilities:Develop Our Product. Take ownership of software features that enhance our AI platform, empowering private market investors to analyze deals swiftly and accurately. This role requires you to actively engage in coding and delivering essential platform components from the ground up.Ensure Quality and Excellence. Establish and maintain coding standards, architectural guidelines, and review procedures; mentor fellow engineers. Co-cultivate a culture centered on practical, reliable, and test-driven development that swiftly meets business requirements.Scale for Growth. Assist in monitoring and scaling the architecture of our platform and its infrastructure.Collaborate Across Functions. Engage closely with product, security, and go-to-market teams to translate our strategic roadmap into actionable features and deliverables.

Join the Revolution at Retell AIRetell AI is pioneering the future of call centers through innovative voice AI, driven by first principles thinking.In just 18 months since our inception, we have empowered thousands of businesses with our AI voice agents, transforming how sales, support, and logistics calls are managed—previously requiring extensive human teams. Supported by prestigious investors such as Y Combinator and Alt Capital, we've rapidly scaled from $5M ARR to an impressive $36M ARR with a compact yet dynamic team of 20.Our ambition for 2026 is to create a revolutionary customer experience platform, where entire contact centers are powered by AI. Moving beyond basic automation, we aim to develop intelligent AI “workers” that serve as frontline agents, QA analysts, and managers, continuously enhancing customer interactions without the need for constant human oversight.As we expand, we are seeking passionate engineers who are eager to solve challenging technical problems, act swiftly, and make a significant impact in one of the fastest-growing voice AI startups. Let’s shape the future together.

fractional-ai is looking for a Senior or Staff Software Engineer to join the San Francisco office. This position centers on building advanced AI solutions with a team that values both technical depth and collaboration. Role overview This role focuses on designing and developing AI-driven systems. The work involves solving technical challenges and contributing to projects that push the boundaries of what AI can achieve. Collaboration with other engineers and stakeholders is a key part of daily responsibilities. Who will thrive Experienced engineers with a strong background in software development Those who enjoy working on complex technical problems Individuals who value teamwork and open communication Location This position is based in the San Francisco office.

Join Our Innovative Team at Retell AIRetell AI is at the forefront of revolutionizing the call center industry through advanced voice AI technology. In just 18 months since our inception, we have empowered thousands of businesses to optimize their sales, support, and logistics calls, which previously relied on large teams of human agents. Supported by prominent investors including Y Combinator and Alt Capital, we've achieved remarkable growth, scaling from $5 million to $36 million in annual recurring revenue (ARR) while expanding our talented team to 20 members.Our ambitious vision for 2026 is to develop a state-of-the-art customer experience platform, transforming entire contact centers with AI. Unlike traditional automation that requires ongoing human oversight, we are building intelligent AI "workers" capable of functioning as frontline agents, quality assurance analysts, and managers, constantly enhancing customer interactions.If you are a passionate innovator eager to solve complex technical challenges and make a tangible impact at one of the fastest-growing voice AI startups, we invite you to join us in shaping the future.Ranked among the top 50 AI applications by a16z: a16z List4th on Brex's Fast-Growing Software Vendors of 2025: Brex BenchmarkFeatured as a leading startup on: Leanaileaderboard

fractional-ai is hiring a Software Engineer to join the team onsite in San Francisco. This role centers on building and improving technology that advances artificial intelligence. Role overview As a Software Engineer, you will work closely with others to develop and support projects that drive the company’s AI initiatives forward. The work involves collaborating with colleagues and contributing technical solutions in a team setting. What you will do Develop software for AI-driven projects Collaborate with team members in the San Francisco office Contribute ideas and technical expertise to ongoing initiatives Requirements Interest in technology and artificial intelligence Ability to work onsite in San Francisco Strong motivation to learn and contribute to team projects

About UnifyUnify is revolutionizing the way revenue teams operate by developing the first AI-powered system of action. Our mission is to transform outbound strategies into a robust growth engine, ensuring that go-to-market execution is observable, repeatable, and scalable. Established in 2023 by industry leaders from Ramp and Scale AI, our talented team boasts backgrounds from renowned companies like Airbnb, Meta, Waymo, and Perplexity.In 2024, Unify achieved an impressive 8x revenue growth and serves a diverse clientele including Perplexity, Cursor, SoFi, and Justworks. We are a dynamic team fueled by high energy and intensity, having secured $58M in funding from leading investors such as Thrive, Emergence, and OpenAI. Join us in shaping the future of GTM!About the Role:As a Senior Software Engineer specializing in AI at Unify, you will be at the forefront of innovation, developing new AI products and enhancing our AI platform. Your work will encompass agents, retrieval systems, classification, fine-tuning, reinforcement learning, and LLM inference infrastructure. If you are passionate about creating production-ready AI systems and wish to contribute to cutting-edge applications used by premier GTM teams, this role is for you.

Join Us in Combating the Escalating Wildfire Crisis with Cutting-Edge AI and IoT SolutionsAbout UsThe Challenge: In the face of climate change, wildfires are becoming more frequent and severe. Traditional methods of fire detection, reliant on bystanders and emergency calls, lead to critical delays in response times. Fire authorities require innovative solutions for faster detection, verification, and response to avert catastrophic fire outbreaks.Who We Are: Pano AI is a dynamic growth-stage startup based in San Francisco, comprising over 150 passionate professionals. We stand at the forefront of wildfire detection and intelligence, equipping fire services with timely information and advanced technology to enhance their response capabilities. Our platform integrates cutting-edge hardware, software, and AI, utilizing ultra-high-definition 360-degree cameras positioned strategically to provide real-time threat assessments. Our technology empowers fire professionals with actionable insights, enabling them to prevent minor flare-ups from escalating into significant disasters.Recognized by TIME as one of the 100 Most Influential Companies of 2025, and featured in MIT Technology Review's top 15 climate tech companies to watch, Pano AI is paving the way for innovative solutions in fire response. Our contributions have been recognized in major publications such as the Wall Street Journal and Bloomberg.

Join Us at Retell AIRetell AI is revolutionizing the call center industry by leveraging innovative voice AI technology based on first principles.In just 18 months since our inception, we have attracted thousands of companies that rely on Retell's AI voice agents to efficiently manage sales, support, and logistics calls, previously handled by large teams of human agents. Supported by renowned investors such as Y Combinator and Alt Capital, we have rapidly grown from $5M to $36M in Annual Recurring Revenue (ARR) with a dedicated team of 20.Looking ahead to 2026, our ambition is to establish a state-of-the-art customer experience platform entirely powered by AI. We aim to create intelligent AI “workers” capable of serving as frontline agents, quality assurance analysts, and managers, continuously optimizing customer interactions without the need for constant human oversight.We are on an exciting growth trajectory and are seeking driven individuals who are eager to solve complex technical challenges, accelerate progress, and make a significant impact at one of the fastest-growing voice AI startups.Let’s innovate the future together!Ranked as a top 50 AI app by a16z: https://tinyurl.com/5853dt2x#4 on Brex's Fast-Growing Software Vendors of 2025: https://www.brex.com/journal/brex-benchmark-december-2025One of the top startups on: https://leanaileaderboard.com/

Join Retell AI as a Senior Full Stack Software EngineerAt Retell AI, we are revolutionizing the call center industry with innovative voice AI technology. Our cutting-edge solutions are designed to improve communication efficiency, allowing businesses to automate sales, support, and logistics calls that once required large teams of human agents. In just 18 months, we have experienced remarkable growth, achieving $36M in annual recurring revenue with a dedicated team of 20, up from $5M at the beginning of 2025.Our goal for 2026 is to create a modern customer experience platform powered entirely by AI. We are not just automating but building intelligent AI agents that can perform the roles of frontline agents, quality assurance analysts, and managers, continuously enhancing customer interactions.We are rapidly expanding and seeking talented individuals who are ready to solve challenging technical problems, work at a fast pace, and make a significant impact in one of the fastest-growing voice AI startups.Let’s shape the future of communication together!

About Simple AIAt Simple AI, we are pioneering cutting-edge voice AI solutions tailored for enterprises. Our lifelike voice agents empower renowned companies such as DoorDash, xAI, and Omaha Steaks in managing diverse phone operations ranging from customer support to order intake and lead qualification. As we experience rapid revenue growth, we seek a couple of founding software engineers to help us meet current customer demands while developing innovative systems for the future. Our team is passionate about harnessing AI to transform the world, and we operate from our San Francisco office five days a week.Simple AI is proudly supported by top-tier investors and industry leaders, including Y Combinator, Massive Tech Ventures, and prominent figures like Michael Seibel (co-founder of Twitch), Jared Friedman (Scribd), Alexandr Wang (Scale AI), Matt Van Horn (June Oven and Lyft), Suhail Doshi (Mixpanel), JJ Fliegelman (WayUp), and Scott Wu (Cognition).Meet the FoundersThe founders, Catheryn Li and Zach Kamran, previously led software teams at Y Combinator, where they launched numerous products for YC founders, including the co-founder matching site. Cat brings experience from Instagram and Facebook and holds degrees in mathematics and computer science from MIT. Zach studied computer science and statistics at the University of Chicago and led software initiatives at PEAK6.What We ProvideCompetitive salary with significant equity opportunitiesEmployee-friendly equity termsOffice located in San FranciscoComprehensive health, dental, and vision insuranceComplimentary lunch and dinner at the officeFree Uber rides home after 8:30 PMRegular team events and offsite activitiesYour Qualifications4+ years of relevant software engineering experience.Exceptional problem-solving skills and a passion for tackling technical challenges.A customer-centric mindset coupled with strong communication skills and a keen interest in product design and prioritization.Self-motivated with the ability to work independently.A genuine enthusiasm for continual learning and keeping abreast of the latest advancements in AI.

Join Aircall, a rapidly growing unicorn company and pioneering AI-driven customer communication platform utilized by over 22,000 businesses globally to enhance revenue, expedite issue resolution, and empower customer-facing teams. We are transforming the landscape of customer communications by seamlessly integrating voice, SMS, WhatsApp, and AI into one cohesive workspace.Our success stems from a straightforward principle: empower teams to work smarter, not harder. With features like the AI Voice Agent automating routine calls, AI Assist optimizing post-call tasks, and AI Assist Pro providing real-time support, we enable teams to achieve exceptional performance. The outcome? Increased revenue, quicker resolutions, and scalable teams operating with confidence.Headquartered in Paris, our European HQ, we also have a robust North American presence anchored in Seattle, with teams spread across Madrid, London, Berlin, San Francisco, New York City, Sydney, and Mexico City. With a product that delights customers and a business model that is scaling rapidly, we are supported by top-tier investors and are at the forefront of AI innovation across diverse product lines.At Aircall, you will be part of a dynamic company. Our ambition drives us, we are product-focused, and we prioritize execution with tangible impacts, swift decision-making, and genuine growth.Our Work Culture at Aircall: We are obsessed with our customers, driven by data, and dedicated to achieving meaningful results. We cherish ownership, continuous learning, and a thoughtful approach to speed. If you thrive in a collaborative and fast-paced environment where trust and impact are valued, you will find your place with us.As a Senior Backend & AI Engineer, you will play a crucial role in designing, developing, deploying, and maintaining essential AI features for our business. Your prior experience in implementing AI functionalities is crucial. You will be expected to promote best practices, mentor fellow team members, and contribute to enhancing quality, excellence, and agility in our delivery processes. Your innovative contributions will include building practical applications such as chatbots, virtual assistants, automated content generation, and other NLP-driven tools. You will leverage and optimize existing large language models (LLMs) to meet specific business needs and domains, ensuring they perform exceptionally in real-world scenarios.

About Flow EngineeringFlow Engineering is an innovative platform harnessing the power of AI to transform how modern engineering teams manage requirements. Our AI-native solution empowers hardware teams to collaborate seamlessly with intelligent agents, facilitating the design, validation, and evolution of complex systems at unprecedented speed and precision.About the RoleWe are on the lookout for experienced senior software engineers with a passion for AI to develop advanced capabilities that enhance the way teams create, review, and oversee requirements. In this role, you will engage with agentic systems and domain engineer workflows, positioning AI at the core of team decision-making processes regarding their systems.This position uniquely integrates AI, product development, and full-stack engineering, allowing you to transform ideas from initial prototypes into stable, observable features deployed in production environments.What You’ll DoDesign and implement AI-driven features, such as assisted requirement drafting, consistency checks, impact analysis, and intelligent suggestions tailored for systems and domain engineers.Create agentic workflows that empower systems engineers and domain engineers to explore designs, simulate changes, and validate requirements effectively.Assess and integrate language models and associated tools, focusing on optimizing reliability, latency, cost, and debuggability within production settings.Develop and sustain the necessary infrastructure, including data pipelines, evaluation harnesses, prompt and model management, observability, and safety protocols.Engage across the entire technology stack—from backend integrations and APIs to user interface components—to deliver comprehensive AI features beyond mere model endpoints.Collaborate with product teams and customers to identify high-value workflows, conduct experiments, and iterate rapidly based on real-world usage insights.About YouA minimum of 3 years’ experience in applied machine learning, large language models, or related fields, with a proven history of delivering ML/LLM-powered features to production.At least 5 years of experience in software development, involving the design, testing, and operation of scalable services in a cloud-based environment.Practical experience with contemporary LLM providers and tools (e.g., OpenAI, Anthropic, Hugging Face, vector stores, and retrieval-augmented generation patterns).Familiarity with prompt design, retrieval-augmented systems, evaluation methodologies, and safety/guardrail strategies.Strong analytical skills to evaluate trade-offs between various models, architectures, and deployment patterns, enabling informed decision-making.A collaborative spirit and effective communication skills to work alongside cross-functional teams.

Senior Software EngineerEngineeringProlific is at the forefront of AI innovation, crafting the essential human data infrastructure that is transforming the AI development landscape. In an era where foundational AI technologies are becoming increasingly common, it is the quality and diversity of human-generated data that sets apart leading products and models.The roleWe seek impact-driven Software Generalists to join our expert team dedicated to supporting frontier model creators and enterprise AI application developers. As a full-stack engineer, you will collaborate across Prolific’s various domains to address customer and product challenges.This position offers an exhilarating chance to engage directly with pioneering AI companies, making vital technical decisions that balance agile startup execution with scalable, reliable engineering practices, as Prolific transforms research within the AI community. You will regularly collaborate in person with customers and our US team, while also working closely with our technology teams based in the UK.What you’ll bring to the roleOver 4 years of experience in a product engineering roleAbility to translate business concepts into effective software modelsCapacity to quickly learn and adapt across the breadth of Prolific’s domainsExperience working with both monolithic and distributed systemsExcellent communication and collaboration skills for direct customer interactionStrong understanding of modern web applications and architecture design patternsExperience in supporting applications within production environmentsSound judgment in technical decisions

At Comulate, we are revolutionizing the insurance back office through the power of AI. Our innovative platform streamlines costly and labor-intensive accounting processes, marking the beginning of our mission to unlock the vast sums spent on manual insurance operations. Our Series B funding, announced in early 2025 and led by BOND & Workday, follows a period of remarkable growth and ambitious expansion plans.Why Join Us?Unprecedented growth trajectory, achieving 8-figure ARR within just three years, placing us in the 95th+ percentile of startup growth.Demonstrated strong product-market fit, with users praising our platform as “the best thing since sliced bread” and “life-changing”.A lean and talented team focused on developing category-defining products for prominent public and private enterprises, driving significant ROI and sustainable operations.We are making bold, innovative bets for a dedicated customer base, with an exciting pipeline of new clients on the horizon.We are just beginning to realize our vision and are well-positioned to integrate AI into crucial workflows across the insurance sector.Role OverviewWe are seeking a Senior Software Engineer to join our in-office team in San Francisco. You will be responsible for developing essential systems, services, and customer-facing features from start to finish. Your work will involve transforming high-level objectives into tangible outcomes, navigating ambiguity, and innovating to discover optimal solutions. As an early member of our team, you will play a crucial role in shaping our company culture and team dynamics.Our technology stack includes: TypeScript, Node, Postgres, React, GraphQL (Apollo), and Next.js.Discover more about our engineering culture and insights on our engineering blog.Are You a Good Fit?A strong desire to innovate and improve software processes.

Join Our Innovative Team at Simple AIAt Simple AI, we are transforming enterprise communications through cutting-edge voice AI agents. Our highly realistic agents empower leading companies such as DoorDash, xAI, and Omaha Steaks to efficiently manage a variety of phone operations, including customer support, order processing, and lead qualification.As we experience exponential growth and a surge in customer demand, we are seeking a few founding software engineers to help us navigate this exciting journey and develop systems for the future. Our passionate team operates from our vibrant San Francisco office five days a week, driven by a shared vision of leveraging AI to make a significant impact in the world.We are proud to be backed by esteemed investors and operators, including Y Combinator, Massive Tech Ventures, and industry leaders such as Michael Seibel (Twitch), Jared Friedman (Scribd), and more.

Join Airwallex as a Senior Software Engineer - AI ToolsAre you ready to make a significant impact in the world of global finance? At Airwallex, we are the leading unified payments and financial platform for businesses around the globe. Our innovative solutions empower over 200,000 businesses, including industry giants like Brex, Qantas, and SHEIN, to seamlessly manage everything from accounts to treasury operations.Founded in Melbourne and now boasting a team of over 2,000 talented individuals across 26 offices worldwide, we are valued at $8 billion and supported by top-tier investors such as T. Rowe Price and Visa. If you're eager to take on challenging projects and grow your career, we want you on our team.What We ValueWe seek dynamic builders with a passion for innovation and a desire to take ownership of their work. You should bring a wealth of expertise and a sharp, analytical mindset, driven by our mission and operating principles. Your ability to make quick yet sound decisions while exploring new avenues will be paramount.As a collaborative team player, you will turn groundbreaking ideas into tangible products and drive our projects to completion. Leveraging AI will be key to working efficiently and solving problems swiftly. Join us in addressing complex challenges with exceptional colleagues while advancing your career in the future of global banking.Your RoleAs a Senior Software Engineer focusing on AI tools, your mission will be to maintain the security of over $150 billion in payments across 150,000 companies and thousands of employees.You will collaborate with internal teams to identify impactful projects, such as developing automation tools, managing our extensive log pipelines, and employing AI to enhance team operations. We value versatility and intelligent problem-solving over specific technologies, so you'll have the freedom to choose the best approaches. Additionally, you'll play a crucial role in mentoring junior engineers and contributing to the growth of our exceptional engineering team.